JP3458503B2 - Fuel injection control device 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 a fuel injection control device for an internal combustion engine having a fuel injection stop function.

[0002]

2. Description of the Related Art Conventionally, in this type of fuel injection control apparatus for an internal combustion engine, the fuel injection amount to the internal combustion engine is feedback-controlled so that the air-fuel ratio detected by the air-fuel ratio sensor matches the target air-fuel ratio. Further, when torque is not needed during deceleration or the like, fuel injection by the fuel injection valve is temporarily stopped.

[0003]

In the control device having the function of stopping the fuel injection as described above, although the fuel consumption is improved, the air-fuel ratio is disturbed due to the stop of the fuel injection, and the three devices installed in the exhaust system are provided. There is a possibility that the original catalyst may be adversely affected, and a technique for overcoming these problems has been conventionally demanded.

That is, when the fuel injection is stopped, the intake air directly flows into the exhaust system, and O ₂ (oxygen) is adsorbed on the three-way catalyst. In this case, even if the air-fuel ratio is made to converge to the stoichiometric air-fuel ratio at the time of returning from the fuel injection stop to the feedback control, the purification capacity of the three-way catalyst is increased because the excessive amount of O ₂ is adsorbed to the three-way catalyst. This causes a problem of a significant decrease. That is, excessive O ₂ may impair the purification function of harmful components of exhaust gas (mainly nitrogen oxide NOx), and the harmful components may be discharged into the atmosphere as the purification function of the three-way catalyst deteriorates. It was In particular, if an acceleration request is made after the return of fuel injection, the air-fuel ratio may be disturbed toward the lean side, and the recovery of the purification function of the three-way catalyst may be significantly delayed.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine capable of obtaining a high purification capacity by a three-way catalyst. To provide.

[0006]

In order to achieve the above object, the invention as set forth in claim 1 is installed in an exhaust system of an internal combustion engine M1 as shown in FIG. 14 to remove harmful substances in the exhaust gas. A three-way catalyst M2 for removal and an air-fuel ratio sensor M3 for detecting the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine M1.
And a fuel injection valve M4 for injecting and supplying fuel to the internal combustion engine M1, and an air-fuel ratio for controlling the fuel injection amount by the fuel injection valve M4 so that the air-fuel ratio by the air-fuel ratio sensor M3 becomes a target air-fuel ratio. A fuel injection control device for an internal combustion engine, comprising: a control means M5; and a fuel injection stop means M6 for stopping fuel injection by the fuel injection valve M4 under a predetermined condition based on an engine operating state. Of adsorbed oxygen amount M7 for calculating the amount of oxygen adsorbed on the three-way catalyst M2 when the fuel injection is stopped by
If, on the <br/> when migrated to the air-fuel ratio control by the fuel injection from said fuel injection stop by stopping means M6 air-fuel ratio control means M5, based on said adsorbed oxygen amount calculated by the adsorption oxygen amount calculating means M7 The air-fuel ratio enriching means M8 for temporarily setting the air-fuel ratio to the rich side is provided , and the adsorbed oxygen amount calculating means M is provided.
The amount of adsorbed oxygen of the three-way catalyst M2 calculated by
When the saturated adsorption amount of oxygen to the original catalyst M2 is reached,
It is summarized as hold to Rukoto a saturated adsorption amount of the adsorption amount of oxygen.

According to a second aspect of the invention, in the first aspect of the invention, the adsorbed oxygen amount calculating means M7 is an intake air to the internal combustion engine M1 when the fuel injection is stopped by the fuel injection stopping means M6. The adsorbed oxygen amount of the three-way catalyst M2 is calculated based on the amount or the fuel injection stop time.

According to a third aspect of the invention, in the first or second aspect of the invention, the amount of oxygen desorbed from the three-way catalyst M2 during the air-fuel ratio enrichment by the air-fuel ratio enrichment means M8 is calculated. The air-fuel ratio enrichment means M8 has a desorption oxygen amount calculation means for performing the air-fuel ratio calculation based on a value obtained by subtracting the desorption oxygen amount by the desorption oxygen amount calculation means from the adsorption oxygen amount by the adsorption oxygen amount calculation means M7. I try to thicken it.

According to a fourth aspect of the present invention, in the third aspect of the invention, the air-fuel ratio sensor M3 is a linear air-fuel ratio sensor that linearly detects the air-fuel ratio, and the desorbed oxygen amount calculation means is The amount of oxygen desorbed from the three-way catalyst M2 is calculated based on the detection result of the air-fuel ratio sensor M3.

According to the invention described in claim 5, claims 1 to 4 are provided.
In any of the inventions described above, the air-fuel ratio enriching means M8 changes the degree of enrichment of the air-fuel ratio according to the adsorbed oxygen amount by the adsorbed oxygen amount calculating means M7.

[0011]

According to the invention of claim 6 , the inventions of claims 1 to 5
In the invention described in (1), the three-way catalyst M2 is detected to be in a deteriorated state, and the saturated adsorption amount updating means is arranged to update the saturated adsorption amount based on the detected deterioration state.

[0013]

According to the invention described in claim 1, the air-fuel ratio control means M5 controls the fuel injection amount by the fuel injection valve M4 so that the air-fuel ratio detected by the air-fuel ratio sensor M3 becomes the target air-fuel ratio. The fuel injection stop means M6 stops the fuel injection by the fuel injection valve M4 under a predetermined condition based on the engine operating state. Further, the adsorbed oxygen amount calculation means M7 is
The amount of oxygen adsorbed on the three-way catalyst M2 when the fuel injection is stopped by the fuel injection stopping means M6 is calculated. Air-fuel ratio enrichment means M
Numeral 8 indicates that the air-fuel ratio is temporarily set to the rich side on the basis of the adsorbed oxygen amount calculated by the adsorbed oxygen amount calculation means M7 during the transition from the fuel injection stop by the fuel injection stop means M6 to the air-fuel ratio control by the air-fuel ratio control means M5. Set to.

That is, when fuel injection is stopped under predetermined conditions, the intake air passes through the exhaust system three-way catalyst M2 as it is, and oxygen in the intake air is adsorbed to the three-way catalyst M2.
In this case, after the transition from the fuel injection stop to the air-fuel ratio control, there is a problem that the excessive amount of oxygen adsorbed on the three-way catalyst M2 causes insufficient purification of harmful components (mainly NOx) in the exhaust gas. . However, according to this configuration, since the air-fuel ratio is temporarily set to the rich side at the time of transition from the stop of fuel injection to the air-fuel ratio control, the oxygen adsorbed on the three-way catalyst M2 is quickly desorbed. As a result, a quick functional recovery of the three-way catalyst M2 is achieved after the end of the fuel injection stop,
A high purification rate is secured.

According to the second aspect of the invention, the adsorbed oxygen amount calculating means M7 is ternary based on the intake air amount to the internal combustion engine M1 or the fuel injection stop time when the fuel injection is stopped by the fuel injection stop means M6. The amount of oxygen adsorbed on the catalyst M2 is calculated. That is, the larger the intake air amount when the fuel injection is stopped or the longer the fuel injection stop time is, the larger the amount of oxygen adsorbed to the three-way catalyst M2 is. Therefore, by appropriately calculating the adsorbed oxygen amount of the three-way catalyst M2 based on the intake air amount or the fuel injection stop time and further enriching the air-fuel ratio according to the adsorbed oxygen amount, an appropriate enrichment of the air-fuel ratio is realized. It

According to the third aspect of the present invention, the desorbed oxygen amount calculating means calculates the amount of oxygen desorbed from the three-way catalyst M2 during the air-fuel ratio enrichment by the air-fuel ratio enriching means M8. The air-fuel ratio enriching means M8 enriches the air-fuel ratio based on the value obtained by subtracting the desorbed oxygen amount calculated by the desorbed oxygen amount calculating means from the adsorbed oxygen amount calculated by the adsorbed oxygen amount calculating means M7. In this case, the oxygen adsorption state of the three-way catalyst M2 after the end of the fuel injection stop is monitored at any time, and the enrichment of the air-fuel ratio can be surely terminated when the adsorbed oxygen amount becomes substantially “0”.

According to the invention described in claim 4, the air-fuel ratio sensor M3 linearly detects the air-fuel ratio. The desorbed oxygen amount calculation means calculates the amount of oxygen desorbed from the three-way catalyst M2 based on the detection result of the air-fuel ratio sensor M3. In this case, the amount of desorbed oxygen can be accurately obtained.

According to the fifth aspect of the invention, the air-fuel ratio enriching means M8 changes the degree of enrichment of the air-fuel ratio according to the adsorbed oxygen amount by the adsorbed oxygen amount calculating means M7. in this case,
If the air-fuel ratio is shifted to the rich side as the amount of adsorbed oxygen increases, the quick recovery of the function of the three-way catalyst M2 is realized.

Further, according to the invention described in claim 1, the upper
In addition to the above action, when the adsorbed oxygen amount of the three-way catalyst M2 calculated by the adsorbed oxygen amount calculation means M7 reaches the saturated adsorbed amount of oxygen with respect to the three-way catalyst M2, the adsorbed oxygen amount is the saturated adsorbed amount. To be held. In other words, the oxygen adsorption capacity of the three-way catalyst M2 has a limit, and the adsorbed oxygen amount saturates at a predetermined value in the limit state. In this case, in the saturated state, the adsorbed oxygen amount calculated by the adsorbed oxygen amount calculation means M7 is held at the saturated adsorbed amount, so that the excessive enrichment of the air-fuel ratio is prevented.

According to the sixth aspect of the present invention, the saturated adsorption amount updating means detects the deterioration state of the three-way catalyst M2 and updates the saturation adsorption amount based on the detected deterioration state. In other words, when the three-way catalyst M2 deteriorates, the exhaust component adsorption capacity and purification performance deteriorate, and the saturated adsorption amount of oxygen changes accordingly. Therefore, the enrichment level of the air-fuel ratio is properly adjusted by updating the saturated adsorption amount depending on the deterioration state of the three-way catalyst M2.

[0021]

An embodiment of the present invention will be described below. FIG. 1 is a schematic structural diagram of an internal combustion engine provided with a fuel injection control device for an internal combustion engine and its peripheral equipment according to the present embodiment.

As shown in FIG. 1, the internal combustion engine 1 has four cylinders 4
It is configured as a cycle spark ignition type. The intake air passes through the air cleaner 2, the intake pipe 3, the throttle valve 4, the surge tank 5 and the intake manifold 6 from the upstream side, and is mixed with the fuel injected from each fuel injection valve 7 in the intake manifold 6 to a predetermined empty space. It is supplied to each cylinder as a fuel-air mixture. Further, a high voltage supplied from an ignition circuit 9 is distributed and supplied by a distributor 10 to an ignition plug 8 provided in each cylinder of the internal combustion engine 1, and an air-fuel mixture in each cylinder is ignited at a predetermined timing. Then, the exhaust gas after combustion passes through the exhaust manifold 11 and the exhaust pipe 12, and the three-way catalyst 13 provided in the exhaust pipe 12 causes harmful components (CO, HC, NOx).
Etc.) are purified and discharged into the atmosphere.

An intake temperature sensor 21 and an intake pressure sensor 22 are provided in the intake pipe 3, the intake temperature sensor 21 indicates the temperature of intake air (intake temperature Tam), and the intake pressure sensor 22 is on the downstream side of the throttle valve 4. Intake air pressure (intake pressure PM)
Respectively detected. Further, the throttle valve 4 is provided with a throttle sensor 23 for detecting the opening of the valve 4 (throttle opening TH). The throttle sensor 23 outputs an analog signal corresponding to the throttle opening TH. , Outputs an ON / OFF signal of an idle switch (idle SW) that detects that the throttle valve 4 is substantially fully opened. A water temperature sensor 24 is provided in the cylinder block of the internal combustion engine 1, and the water temperature sensor 24 measures the temperature of the cooling water in the internal combustion engine 1 (cooling water temperature Th.
w) is detected. The distributor 10 is provided with a rotation speed sensor 25 for detecting the rotation speed of the internal combustion engine 1 (engine rotation speed Ne), and this rotation speed sensor 25 performs two rotations of the internal combustion engine 1, that is, every 720 ° CA. Then, 24 pulse signals are output at equal intervals.

Further, on the upstream side of the three-way catalyst 13 of the exhaust pipe 12, according to the oxygen concentration of the exhaust gas discharged from the internal combustion engine 1, a wide / linear air-fuel ratio λ signal is output A / An F sensor (air-fuel ratio sensor) 26 is provided. Further, on the downstream side of the three-way catalyst 13, a voltage V depending on whether the air-fuel ratio λ is rich or lean with respect to the theoretical air-fuel ratio λ = 1.
An O ₂ sensor 27 that outputs OX2 is provided.

An electronic control unit (hereinafter referred to as ECU) 31 for controlling the operation of the internal combustion engine 1 includes a CPU (central processing unit) 32, a ROM (read only memory) 33, and a RAM.
(Random access memory) 34, Backup RAM
It is configured as a logical operation circuit around 35 and the like, and is connected via a bus 38 to an input port 36 for inputting a detection signal of each sensor and an output port 37 for outputting a control signal to each actuator. Then, the ECU 31
Is the intake air temperature T from each of the sensors via the input port 36.
am, intake pressure PM, throttle opening TH, cooling water temperature Thw,
The engine speed Ne, the air-fuel ratio signal, etc. are input, the control signals such as the fuel injection amount TAU, the ignition timing Ig, etc. are calculated based on the respective values, and the control signals are output to the output port 3
It outputs to the fuel injection valve 7 and the ignition circuit 9 etc. via 7 respectively. In the present embodiment, the CPU 32 constitutes the air-fuel ratio control means, the fuel injection stop means, the adsorbed oxygen amount calculation means, the air-fuel ratio enrichment means, and the desorbed oxygen amount calculation means.

Next, the operation of the fuel injection control device configured as described above will be described with reference to FIGS. Note that FIG.
6 is a flowchart showing a control program executed by the CPU 32, and the processing of FIG.
In s cycles, the process of FIG. 3 is executed in 32 ms cycles. The processes of FIGS. 4 to 6 are executed in a predetermined order according to the input of the TDC signal. Further, FIG. 7 is a timing chart more specifically showing the operation during fuel cut and during air-fuel ratio enrichment.

To briefly explain this operation, the CPU 32 mainly performs the air-fuel ratio feedback processing for feedback-controlling the fuel injection amount so as to match the air-fuel ratio with the target air-fuel ratio (ideal air-fuel ratio) and the engine operating state. Based on the predetermined conditions, a fuel cut process for stopping the fuel injection and an air-fuel ratio enrichment process for temporarily enriching the air-fuel ratio at the end of the fuel cut are performed. These processes are managed by the respective flags of the "feedback control flag XFB", "fuel cut flag XFC" and "air-fuel ratio enrichment flag XErich", and the period of XFB = 1 (for example, time t2 in FIG. 7). The air-fuel ratio feedback control is executed before and after time t4), the fuel cut is executed during the period of XFC = 1 (for example, time t2 to t3 in FIG. 7), and the period during XErich = 1 (for example, FIG. 7). At time t4 to t5), the air-fuel ratio enrichment process is executed.

Further, when the air-fuel ratio feedback process shifts to the fuel cut process, or when the fuel cut process shifts to the air-fuel ratio enrichment process, a delay time is set to delay the subsequent process by a predetermined time. . That is, when shifting from the air-fuel ratio feedback process to the fuel cut process, a delay time (for example, time t1 to t2 in FIG. 7) is set by the "delay counter CDFC", and shifts from the fuel cut process to the air-fuel ratio feedback process. At this time, the delay time (for example, time t3 to t4 in FIG. 7) by the "delay counter CDFB" is set.

The fuel cut flag XFC is set in the flow chart of FIG. 2 and the delay counters CDFC and CDFB are counted in the flow charts of FIGS. 3 and 4 in order to specifically execute the above processing. Further, in the flowchart of FIG. 5, the adsorbed oxygen amount of the three-way catalyst 13 at the time of fuel cut and air-fuel ratio enrichment is calculated, and in the flowchart of FIG. 5, the fuel injection amount TAU is calculated. The contents of the flowcharts shown in FIGS. 2 to 6 will be described in detail below.

In the flow chart of FIG. 2, the CPU 3
2. First, at step 101, the fuel cut flag XF
It is determined whether or not "1" is set in C. In the normal air-fuel ratio feedback state, negative determination is made in step 101 (XFC = 0), and the CPU 32 determines in step 102.
Proceed to. Then, the CPU 32 executes steps 102 and 10.
At 3, the fuel cut execution condition is determined.

That is, the CPU 32 executes step 102.
In step 103, it is determined whether or not the idle SW is ON, and in step 103 it is determined whether the engine speed Ne exceeds a predetermined speed (1400 rpm in this embodiment) for determining execution of fuel cut. . In this case, step 10
If either of the numbers 2 and 103 is negatively determined, the CPU 32
Determines that the fuel cut execution condition is not satisfied, the routine proceeds to step 104, the delay counter CDFC is cleared to "0", and this routine is ended.

If both steps 102 and 103 are affirmatively determined, the CPU 32 determines that the fuel cut execution condition is satisfied and proceeds to step 105. The CPU 32 determines in step 105 whether the count value of the delay counter CDFC is "0". In this case, initially DC
Since FC = 0, affirmative determination is made in step 105, and CP
U32 proceeds to step 106. And the CPU 32
Sets the delay counter CDFC to "1" in step 106.
Then, this routine is finished.

After setting CDFC = 1, step 1
No is determined in step 05, and the CPU 32 determines in step 107 that the count value of the delay counter CDFC is the predetermined determination value CK.
It is determined whether or not it exceeds 1 (for example, a count value corresponding to 0.5 seconds). Where delay counter CDFC
Are counted in the routine shown in FIG. More specifically, the CPU 32 determines in step 201 of FIG. 3 whether or not CDFC = 0, and if CDFC = 0, the present routine ends. If CDFC ≠ 0, CPU
In step 202, 32, the delay counter CDFC is incremented by "1" and this routine is finished. That is, after CDFC = 1 is set in step 106 of FIG. 2, each time the process of FIG. 3 is executed (32 ms
The delay counter CDFC is incremented by "1" each time.

Then, when CDFC≤CK1 and the determination in step 107 of FIG. 2 is negative, the CPU 32 ends the routine of FIG. 2 as it is. Also, CDFC> C
When the result is K1 and the determination in step 107 is affirmative, the CPU 32 proceeds to step 108 to set the fuel cut flag XFC to “1” and the feedback control flag XF.
This routine is completed by setting B to "0" and the delay counter CDFC to "0".

On the other hand, as described above, the fuel cut flag XFC
If "1" is set to, the affirmative determination is made in step 101. Therefore, the CPU 32 proceeds to step 109 and determines whether the engine speed Ne is less than a predetermined speed (1000 rpm in this embodiment) for determining the end of fuel cut. In addition, the CPU 32 executes step 1
At 10, it is determined whether the idle SW is on.

In this case, the engine speed Ne is 1000 rp
If m or more and idle SW = ON (step 1
If 09 is NO and step 110 is YES), CP
U32 ends this routine as it is. Further, if the engine speed Ne is less than 1000 rpm or the idle S
If W = OFF (YES in step 109 or NO in step 110), the CPU 32 causes step 111
Then, the fuel cut flag XFC is set to "0", the delay counter CDFB is set to "1", and this routine is finished.

The delay counter CDFB is a counter which is counted up in the routine shown in FIG. 4, and its processing will be described. As described above, the CPU 32 starts the routine of FIG. 4 in synchronization with the input of the TDC signal, and the CPU 32 first determines in step 301 whether CDFB = 0. If CDFB = 0, CPU 32
Ends this routine as it is. Further, if CDFB ≠ 0, that is, the CD in step 111 of FIG. 2 described above.
If FB = 1 is set, the CPU 32 proceeds to step 30.
In step 2, the delay counter CDFB is incremented by "1".

Thereafter, the CPU 32 determines in step 303 that the count value of the delay counter CDFB is a predetermined judgment value C.
It is determined whether or not K2 (for example, 30 counts) has been reached. When the delay counter CD2 reaches the determination value CK2, the CPU 32 proceeds to step 304, sets the air-fuel ratio enrichment flag XErich to "1", the feedback control flag XFB to "1", and the delay counter CDFB to "0". Then, this routine is finished.

On the other hand, in the adsorbed oxygen amount calculation routine of FIG. 5, the CPU 32 first determines in step 401 whether the fuel cut flag XFC is set to "1" (whether fuel cut is being executed). To do. If XFC = 1, the CPU 32 proceeds to step 402 to calculate the amount of oxygen adsorbed on the three-way catalyst 13 during the fuel cut (hereinafter referred to as adsorbed oxygen amount SMO ₂ ). Adsorbed oxygen amount SMO ₂
(mol) is calculated from the following formula 1.

[0040]

## EQU1 ## SMO ₂ = Exhaust air amount × Oxygen concentration × Volume weight conversion factor / Mole conversion factor (= 32 g) where the exhaust air amount is a value corresponding to the intake air amount,
The value is calculated from the engine speed Ne and the intake pressure PM (= Ne × PM × coefficient). In addition, since the exhaust gas becomes air during the fuel cut, the oxygen concentration matches the oxygen ratio (= about 20%) in the air.

Thereafter, the CPU 32 at step 403.
Adsorbed oxygen amount SMO₂Is the saturation adsorption amount O which is set in advance
It is determined whether ST or less. Adsorbed oxygen amount SMO₂But
If the saturated adsorption amount is OST or less (SMO₂≤ OST), CP
U32 ends this routine as it is. Also, the adsorbed acid
Elementary SMO₂Exceeds the saturated adsorption amount OST (SMO
₂> OST), the CPU 32 calculates the above in step 404.
Adsorbed oxygen amount SMO ₂Hold at saturated adsorption amount OST
Then, this routine is finished. That is, the saturated adsorption amount described above
OST said that the three-way catalyst 13 was saturated on the lean side.
Mushroom O₂Corresponding to the maximum adsorption amount. Therefore,
SMO₂> In the case of OST, the oxygen in the exhaust gas is
Above, it flows to the downstream side without being adsorbed by the three-way catalyst 13.
The amount of adsorbed oxygen SMO₂Is the saturated adsorption amount OST
Be dealt with.

On the other hand, if the determination at step 401 is negative (if fuel is not being cut), the CPU 32 proceeds to step 405 to determine whether or not the air-fuel ratio enrichment flag XErich is set to "1", that is, the air-fuel ratio. It is determined whether or not it is being concentrated. If XErich = 1, CPU 32
In step 406, the amount of oxygen desorbed from the three-way catalyst 13 (hereinafter referred to as desorbed oxygen amount PGO ₂ ) is calculated. This desorbed oxygen amount PGO ₂ (mol) is calculated by the following mathematical formula 2.

[0043]

[Formula 2] PGO ₂ = amount of exhaust air × equivalent amount of desorption of oxygen concentration × volume weight conversion coefficient / molar conversion coefficient (= 32 g) Here, the desorption amount of oxygen concentration is detected by the A / F sensor 26. Calculated from the air-fuel ratio λ (= λ × coefficient),
The value is calculated as a value substantially proportional to the actual air-fuel ratio λ.

Further, the CPU 32 proceeds to the next step 40.
In step 7, the amount of adsorbed oxygen SMO _{2 up} to
The desorbed oxygen amount PGO ₂ calculated in 06 is subtracted, and the subtracted value is set as a new adsorbed oxygen amount SMO ₂ . That is, the adsorbed oxygen amount SMO _{2 at} this time corresponds to the amount of oxygen remaining in the three-way catalyst 13.

After that, the CPU 32 determines in step 408 whether or not the adsorbed oxygen amount SMO ₂ is less than a predetermined value S 0 near “0”. At this time, if the adsorbed oxygen amount SMO ₂ is equal to or larger than the predetermined value S0 (SMO ₂ ≧ S0), the CPU 3
In the case of 2, it is considered that the air-fuel ratio needs to be enriched, and the routine is finished as it is. If the adsorbed oxygen amount SMO ₂ is less than the predetermined value S0 (SMO ₂ <S0), the CPU 32
Is considered to be unnecessary for the enrichment of the air-fuel ratio and step 40
In step 9, the air-fuel ratio enrichment flag XErich is cleared to "0", and this routine ends.

When the determination in step 405 is negative (XErich = 0), the CPU 32 proceeds to step 410, clears the adsorbed oxygen amount SMO ₂ to "0", and terminates this routine.

In the fuel injection amount calculation routine shown in FIG.
First, in step 501, the CPU 32 sets the fuel cut flag X.
It is determined whether FC is cleared to "0", and XF
If C = 1, the process proceeds to step 502. And CPU
After setting the fuel injection amount TAU to "0" to execute the fuel cut in step 502, 32 ends the present routine.

If XFC = 0, the CPU 32 proceeds to step 503 to calculate the basic injection amount Tp. This basic injection amount Tp is calculated according to the engine speed Ne and the intake pressure PM at that time, using an injection amount map stored in advance in the ROM 33, for example. Furthermore, the CPU 32
Returns the feedback control flag XFB in step 504.
It is determined whether or not "1" is set to XFB =
If it is 0, in step 509, the feedback correction coefficient F
The AF is fixed at "1.0".

If XFB = 1, the CPU 32 proceeds to step 505 to determine whether the air-fuel ratio enrichment flag XErich is set to "1". At this time, if XErich = 0, the CPU 32 proceeds to step 50.
Go to 6 and set the target air-fuel ratio λTG to "1.0" (ideal air-fuel ratio)
And If XErich = 1, the CPU 32 proceeds to step 507 and sets the target air-fuel ratio λTG to "0.995".
And That is, when the air-fuel ratio enrichment flag XErich is set to “1”, the target air-fuel ratio λTG is set to the 0.5% rich side with respect to the ideal air-fuel ratio.

After that, the CPU 32 calculates the feedback correction coefficient FAF by using the following expression 3 in step 508. The setting of the feedback correction coefficient FAF is disclosed in Japanese Patent Laid-Open No. 1-110853.

[0051]

[Equation 3]

Here, k is a variable indicating the number of times of control from the start of the first sampling, K1 to Kn + 1 are optimum feedback gains, ZI (k) is an integral term, and Ka is an integral constant. After calculating the feedback correction coefficient FAF, the CPU 3
In step 510, various correction factors FALL such as water temperature and electric load are calculated. Further, in step 511, the CPU 32 calculates the fuel injection amount TAU by using the following formula 4, and ends this routine.

[0053]

## EQU00004 ## TAU = Tp.times.FAF.times.FALL Next, the operation during fuel cut and air-fuel ratio enrichment will be described more specifically using the timing chart of FIG. In FIG. 7, time t1 is the time when the idle SW is turned on, time t2 to t3 is the period in which fuel cut is executed, and time t4 to t5 is the period in which air-fuel ratio enrichment processing is executed after fuel cut.

At time t1, the air-fuel ratio feedback control is executed, and when the idle SW is turned on at this time t1, the delay counter CDFC starts to move from "0" (however, Ne> 1400 rpm). And
At the time t2 when the count value of the counter CDFC reaches the predetermined determination value CK1, the fuel cut flag XFC is "1".
And the feedback control flag XFB
Is cleared to “0” (processing of step 108 in FIG. 2). At this time, the air-fuel ratio feedback control is stopped and the fuel cut is started. The delay counter C
If the idle SW is turned off before DFC reaches the determination value CK1, the counter CDFC is immediately cleared to "0" (process of step 104 in FIG. 2). That is, fuel cut is not executed when the idle SW is temporarily turned on.

Then, when the engine speed Ne drops to the predetermined speed (1000 rpm) at time t3, the fuel cut flag XFC is cleared to "0" (the process of step 111 in FIG. 2). That is, the fuel cut is executed during the period from time t2 to t3, and the air-fuel ratio largely deviates to the lean side during the same period. Further, during the fuel cut, the intake air passes through the cylinder and directly flows to the exhaust pipe 12 side, and the oxygen in the intake air is adsorbed to the three-way catalyst 13. The amount of oxygen adsorbed on the three-way catalyst 13 is sequentially calculated as the adsorbed oxygen amount SMO ₂ (processing of step 402 in FIG. 5).

At time t3, the delay counter C
DFB starts to move from "0", and at the time t4 when the count value of the counter CDFB reaches a predetermined judgment value CK2, the air-fuel ratio enrichment flag XErich and the feedback control flag XF.
B is set to "1" (processing of step 304 in FIG. 4). At this time, since a predetermined delay time is set from the end of fuel cut to the start of feedback, A
Even if the / F sensor 26 is output later than the actual change in the air-fuel ratio, overcorrection of the feedback control at that time is prevented.

When the air-fuel ratio feedback control is restarted at time t4, the target air-fuel ratio λTG is shifted to the rich side by a predetermined value because the air-fuel ratio enrichment flag XErich is set to "1" (Fig. 6 processing of step 507). In this case, since the air-fuel ratio shifts to the rich side, the oxygen component adsorbed on the three-way catalyst 13 gradually reacts and is consumed.

After time t4, the amount of oxygen consumed by the enrichment of the air-fuel ratio is sequentially calculated as the desorbed oxygen amount PGO ₂ , and the desorbed oxygen amount PG is calculated from the adsorbed oxygen amount SMO _{2 up} to that point.
The value obtained by subtracting O ₂ becomes the latest adsorbed oxygen amount SMO ₂ (processing of steps 406 and 407 in FIG. 5). Then, at the time t5 when the adsorbed oxygen amount SMO ₂ decreases to approximately “0”, the air-fuel ratio enrichment flag XErich is cleared to “0” (the processing of steps 408 and 409 in FIG. 5), and thereafter, the normal air-fuel ratio enrichment flag XErich is cleared. Fuel ratio feedback is implemented.

The air-fuel ratio enrichment degree is preferably set to a predetermined value on the rich side of about 0.5 to 2.0% with respect to the ideal air-fuel ratio. That is, if the enrichment degree is set beyond this range, the rich component per unit area / time of the three-way catalyst 13 increases too much, and the rich component of the rich component remains even though oxygen remains in the three-way catalyst 13. Although purification may become difficult, if the enrichment degree of the air-fuel ratio is within the above range (0.5 to 2.0%), O ₂ from the three-way catalyst 13
Both desorption and purification of rich components can be realized.

As described above in detail, in the fuel injection control device of the present embodiment, even if oxygen in intake air is adsorbed to the three-way catalyst 13 due to fuel cut, the above-mentioned three factors are caused at the transition from fuel cut to feedback control. The adsorbed oxygen of the original catalyst 13 is quickly desorbed. Therefore, unlike the conventional control device, there is no problem of insufficient purification of harmful components (mainly NOx) in the exhaust gas due to an excessive amount of oxygen adsorbed on the three-way catalyst 13 during fuel cut, It is possible to promptly recover the function of the three-way catalyst 13 after fuel cut and ensure a high purification rate. In addition, even during sudden acceleration immediately after fuel cut, which has been a concern in the past, the three-way catalyst 1
Due to the prompt functional recovery of 3, it is possible to realize appropriate purification of exhaust components.

Further, in this embodiment, the three-way catalyst 13 at the time of fuel cut is based on the intake air amount into the internal combustion engine 1.
The adsorbed oxygen amount SMO _{2 of} was calculated (Equation 1). Also, A
Based on the linear air-fuel ratio detection result detected by the / F sensor 26, the desorbed oxygen amount PGO ₂ of the three-way catalyst 13 at the time of enrichment of the air-fuel ratio was calculated (Formula 2). As a result, the effect that the air-fuel ratio can be appropriately enriched can be obtained. That is, since the adsorbed oxygen amount SMO ₂ is proportional to the intake air amount, the adsorbed oxygen amount SMO ₂ can be more accurately grasped according to the present embodiment. Further, by using the wide-range and linear air-fuel ratio detection result, the three-way catalyst 13
The oxygen desorption state from can be monitored accurately. Then, by performing the enrichment of the air-fuel ratio based on the monitoring results of the adsorbed oxygen amount SMO ₂ and the desorbed oxygen amount PGO ₂ , an appropriate enrichment of the air-fuel ratio can be realized. This embodiment corresponds to the invention described in claims 2 to 4.

Further, in this embodiment, when the adsorbed oxygen amount SMO2 of the three-way catalyst 13 reaches the saturated adsorbed amount OST of O2,
The adsorbed oxygen amount SMO2 was held at the saturated adsorbed amount OST. That is, the oxygen adsorption capacity of the three-way catalyst 13 has a limit, and the adsorbed oxygen amount is saturated in the limit state. In this case, in the saturated state, the adsorbed oxygen amount SMO2 calculated by the CPU 32 is held at the saturated adsorbed amount OST to prevent excessive enrichment of the air-fuel ratio .

On the other hand, as the three-way catalyst 13 deteriorates, the adsorption capacity and purification performance of exhaust components change, so the saturated adsorption amount OST shown in steps 403 and 404 of FIG. 5 changes with time. Therefore, the learning process of the saturated adsorption amount OST will be described below. 8 to 11 are control programs executed by the CPU 32. FIG. 8 is a learning start determination routine, FIG. 9 is an A / F fluctuation control routine, FIG. 10 is a saturation determination routine, and FIG. 11 is a saturated adsorption amount calculation. Indicates a routine. Further, FIG. 12 shows O when learning the saturated adsorption amount OST.
₂ is a timing chart showing the output voltage VOX2 of the ₂ sensor 27 and the target air-fuel ratio λTG. The CPU 32
The detection signal of the vehicle speed sensor (not shown) is used, and the learning process of the saturated adsorption amount OST by the routines shown in FIGS. 8 to 11 is executed every time the vehicle travels 2000 km based on the detection signal.

First, the CPU 32 sets XFB = 1 and XEri in step 601 of the learning start determination routine shown in FIG.
It is determined whether ch = 0, that is, whether the feedback control is being performed and the air-fuel ratio is not being enriched. Then, if step 601 is YES, the CPU 32 determines in step 602 whether the engine operating state is the steady state. In this case, if the engine speed Ne and the intake pressure PM are substantially constant values, it is determined that the engine is in a steady state. In addition, O
₂ Whether or not the output voltage VOX2 of the sensor 27 has converged within a predetermined allowable range can be added to the above determination.

If YES at step 602, the CPU
32 continues at step 603, where the learning execution flag XOSTG
It is determined whether or not a predetermined interval time T has elapsed (from the time of change of XOSTG = 1 → 0) after the clearing of, and when this interval time T has elapsed, step 6
In 04, the learning execution flag XOSTG is set to "1", and this routine ends. Also, steps 601-603
If any of the above is NO, the CPU 32 executes step 6
In step 05, the learning execution flag XOSTG is cleared to "0", and this routine ends.

When the learning execution flag XOSTG is set by the learning start determination routine, the CPU 32
Is the step 70 of the A / F fluctuation control routine shown in FIG.
1 is affirmatively determined. Then, the CPU 32 executes step 7
In step 02, whether the correction execution counter TC exceeds the preset rich correction time TR, that is, the rich correction time T
Determine if R has elapsed. Step 702 is NO
If so, the CPU 32 proceeds to step 703 to set the target air-fuel ratio λTG to the preset rich target air-fuel ratio λRT. After that, the CPU 32 increments the correction execution counter TC by "1" in step 704 and ends this routine. That is, as shown in the timing chart of FIG. 12, the target air-fuel ratio λTG is held at the rich target air-fuel ratio λRT on the rich side of the theoretical air-fuel ratio λ = 1 until the rich correction time TR elapses from the time t11. Although not described in detail, time t11 indicates the timing of satisfaction of the initial condition at the beginning of learning the saturated adsorption amount OST).

When step 702 is YES, the CPU 32 proceeds to step 705 and determines whether or not the correction execution counter TC exceeds the value obtained by adding the lean correction time TL set in advance to the rich correction time TR, that is, After the rich correction time TR has elapsed, it is determined whether or not the lean correction time TL has further elapsed. If step 705 is NO, the CPU 32 sets the target air-fuel ratio λTG to the preset lean target air-fuel ratio λLT in step 706, increments the correction execution counter TC by “1” in step 704, and then ends this routine. That is, FIG.
As shown in the timing chart of, the lean correction time T
Until the time t12 when L elapses, the target air-fuel ratio λTG is leaner than the stoichiometric air-fuel ratio λ = 1.
Held in. In the present embodiment, the deviation width of the rich target air-fuel ratio λRT with respect to the theoretical air-fuel ratio λ = 1 and the deviation width of the lean target air-fuel ratio λLT with respect to λ = 1 are equal, and the rich correction time TR and the lean correction time TL are also equal. Therefore, CO and HC adsorbed on the three-way catalyst 13 by the rich correction (step 703) are substantially completely desorbed by the subsequent lean correction (step 706), and the air-fuel ratio becomes the theoretical air-fuel ratio λ = It quickly recovers to around 1.

When the lean correction time TL has elapsed, step 705 becomes YES, the CPU 32 clears the learning execution flag XOSTG to "0" at step 707, and this routine ends.

On the other hand, when the learning execution flag XOSTG is set by the learning start judgment routine, the CPU 32
Makes a positive determination in step 801 of the saturation determination routine shown in FIG. Then, the CPU 32 proceeds to step 802, where the target air-fuel ratio λ in step 703 of FIG. 9 is set.
By correcting TG to the rich side, it is determined whether the output voltage VOX2 of the O ₂ sensor 27 has exceeded a preset saturation determination level VSL. When VOX2 ≦ VSL, CP
U32 does not perform any processing, and when VOX2> VSL, the saturation determination flag XOSTOV is set to "1" in step 803.
Is set and this routine ends. Here, the saturation determination level VSL means O ₂ when the three-way catalyst 13 is in a saturated state, in other words, when the adsorption amount of CO or HC exceeds the adsorption limit and begins to be discharged from the three-way catalyst 13. Sensor 2
Corresponding to the output voltage VOX2 output by
It is a value exceeding the rich side allowable value of OX2.

Further, when the learning execution flag XOSTG is cleared by the A / F fluctuation control routine (step 707 in FIG. 9), the CPU 32 determines that this A / F fluctuation control routine has been completed for one cycle, and FIG. An affirmative decision is made in step 901 of the saturated adsorption amount calculation routine shown in FIG. Then, the CPU 32 determines in step 902 whether or not the saturation determination flag XOSTOV is set to "1". If XOSTOV = 0, the previous A / F
Assuming that the three-way catalyst 13 has not exceeded the adsorption limit due to the execution of the fluctuation control routine, the CPU 32 executes step 903.
Proceed to. The CPU 32 adds the preset addition time Ta to the rich correction time TR and the lean correction time TL in step 903. In this way, when the adsorption limit of the three-way catalyst 13 is not reached due to the enrichment of the A / F fluctuation control routine, the rich correction time TR and the lean correction time TL
When the A / F fluctuation control routine of FIG. 9 is executed next time, the target air-fuel ratio λTG is made rich and lean by using the extended correction times TR and TL (see FIG. 12). Time t13-14).

After that, when the output voltage VOX2 of the O ₂ sensor 27 exceeds the saturation determination level VSL with the enrichment and leaning of the target air-fuel ratio λTG (time t15 in FIG. 12), the saturation determination flag XOSTOV is set (Fig. 10, steps 802 and 803), the CPU 32 proceeds from step 902 to step 904 in FIG. The CPU 32, in step 904, according to the following mathematical formula 5, the current three-way catalyst 13
The saturated adsorption amount OST of is calculated.

[0072]

## EQU5 ## OST = substance concentration × QA × TR Here, the substance concentration is the content ratio of the harmful component in the exhaust gas which is determined according to the air-fuel ratio λ as shown in FIG.
As is well known, as components in the exhaust gas, NOx and O ₂ increase when the air-fuel ratio λ is biased to the lean side, and CO and HC increase when it is biased to the rich side. 1
In 3, the substance concentration is determined based on O ₂ , so that the lean side represents the excess amount of O ₂ and the substance concentration is set as a positive value, and the rich side sets the O ₂ required by CO and HC. It represents the shortfall and the substance concentration is set as a negative value. In the case of this processing, as the substance concentration, “MR” for the preset rich target air-fuel ratio λRT is selected, and this substance concentration MR, the intake air amount QA calculated from the engine speed Ne and the intake pressure PM, and The product of represents the amount of introduced O ₂ per unit time.

As described above, the saturated adsorption amount OST of the three-way catalyst 13
The saturated adsorption amount OST of the three-way catalyst
The value corresponds to the deterioration state of 13. Therefore, as described above
Step 40 in the routine for calculating the amount of adsorbed oxygen shown in FIG.
Adsorbed oxygen amount SMO of 3,404 ₂The guard processing of
By using the saturated adsorption amount OST after the new,
A highly accurate air-fuel ratio control can be realized.

According to this embodiment, the saturated adsorption amount OST is updated at any time according to the deterioration state of the three-way catalyst 13,
It is possible to properly adjust the enrichment level of the air-fuel ratio. This embodiment corresponds to the invention described in claim 6, and the saturated adsorption amount updating means is constituted by the series of learning processing of the saturated adsorption amount OST described above.

Further, as a method of detecting the deterioration state of the three-way catalyst 13, a method of obtaining the purification rate of the three-way catalyst 13 and detecting the purification rate based on the purification rate can be used (for example, Japanese Unexamined Patent Publication No. Hei 3 (1999) -311). -253714, "Catalyst Purification Rate Detector"). That is, according to this detection method, O ₂ sensors are provided on the upstream side and the downstream side of the three-way catalyst, respectively, and the response delay time of the O ₂ sensor on the upstream side when the air-fuel ratio changes from rich to lean. The response delay time difference is calculated from the response delay time of the downstream O ₂ sensor, and the purification rate of the three-way catalyst is calculated based on the response delay time difference.

The present invention can be embodied as follows in addition to the above embodiment. (1) In the above embodiment, the enrichment degree of the air-fuel ratio is set to a constant value when the air-fuel ratio is enriched at the end of fuel cut (target air-fuel ratio λTG = 0.995), but this enrichment degree is set as the three-way catalyst 13
It may be variable according to the oxygen adsorption level of. For example, in the range of 0.5 to 2.0% with respect to the ideal air-fuel ratio (range of target air-fuel ratio λTG = 0.98 to 0.995), the enrichment degree is set in multiple stages, and the adsorbed oxygen The larger the amount SMO ₂ , the larger the target air-fuel ratio λTG is shifted to the rich side. Specifically, for example, a map having the adsorbed oxygen amount SMO ₂ and the target air-fuel ratio λTG as parameters is prepared in advance, and the target air-fuel ratio λTG is calculated using this map when the air-fuel ratio is enriched. In this case, the functional recovery of the three-way catalyst 13 can be achieved more quickly than in the above embodiment. This embodiment corresponds to the invention described in claim 5.

(2) In the above embodiment, the adsorbed oxygen amount SMO ₂ of the three-way catalyst 13 is monitored by calculating "SMO ₂ -PGO ₂ " at the time of enrichment of the air-fuel ratio, and the oxygen amount SM thereof is monitored.
The enrichment of the air-fuel ratio was executed until O ₂ reached approximately “0”, but this method may be changed. For example, an air-fuel ratio enrichment time may be set at the end of fuel cut, and the air-fuel ratio enrichment may be executed within that time. In particular,
Similar to the above embodiment, the oxygen adsorption amount S at the time of fuel cut
MO ₂ is sequentially integrated, and the enrichment time corresponding to the amount of oxygen accumulated until then is set in the timer at the end of fuel cut. After that, the enrichment of the air-fuel ratio is ended after the enrichment time of the timer has elapsed. In this case, the calculation process of the desorbed adsorption amount PGO ₂ is not performed, but the object of the present invention can be achieved as in the above-described embodiment.

(3) In the above embodiment, the adsorbed oxygen amount SMO ₂ at the time of fuel cut is calculated according to the intake air amount. However, the elapsed time at fuel cut is measured and the adsorbed oxygen amount is calculated according to this fuel cut time. The quantity SMO ₂ may be calculated. That is, as the fuel cut time is longer, the amount of oxygen adsorbed on the three-way catalyst 13 increases. Therefore, by performing the enrichment of the air-fuel ratio in accordance with the further adsorption oxygen SMO ₂ obtains the adsorbed oxygen amount SMO ₂ of the three-way catalyst 13 based on the fuel cut time, to realize the enrichment of appropriate air-fuel ratio You can

(4) In the above embodiment, the degree of adsorption of O ₂ on the three-way catalyst 13 was calculated by converting it to the amount of oxygen (adsorbed oxygen amount SMO ₂ and desorbed oxygen amount PGO ₂ ). You may change it. For example, the air-fuel ratio λ detected by the A / F sensor 26 during fuel cut or air-fuel ratio enrichment may be integrated each time, and the integrated value may be used to obtain a value corresponding to the oxygen adsorption amount. . Even in this case, the object of the present invention can be achieved.

(5) In the above embodiment, the A / F sensor 26 for linearly detecting the air-fuel ratio is provided on the upstream side of the three-way catalyst 13, and the air-fuel ratio enrichment is realized by using the detection result of the sensor 26. However, the present invention can be embodied without necessarily being a linear air-fuel ratio sensor. That is, when the calculation process of the desorbed oxygen amount PGO ₂ is unnecessary as described above as the other embodiment (2), the control device uses only the air-fuel ratio sensor of the same type as the O ₂ sensor 27 of FIG. Can also be configured.

[0081]

According to the invention described in claim 1, the air-fuel ratio is enriched in accordance with the amount of oxygen adsorbed on the three-way catalyst when the fuel injection is stopped. It has an excellent effect that it can be removed quickly and a high purification capacity by a three-way catalyst can be obtained.

According to the second aspect of the present invention, the adsorbed oxygen amount of the three-way catalyst is calculated based on the intake air amount or the fuel injection stop time, and the air-fuel ratio is enriched according to the adsorbed oxygen amount. Therefore, it is possible to realize an appropriate enrichment of the air-fuel ratio.

According to the third aspect of the present invention, the oxygen adsorption state of the three-way catalyst after the end of the fuel injection stop can be monitored at any time, and when the adsorbed oxygen amount becomes substantially "0", the empty state is reached. It is possible to surely finish the enrichment of the fuel ratio.

According to the fourth aspect of the present invention, the amount of desorbed oxygen can be accurately obtained by using the air-fuel ratio detection result linearly. According to the fifth aspect of the invention, the larger the adsorbed oxygen amount, the larger the air-fuel ratio is shifted to the rich side, whereby the quick recovery of the function of the three-way catalyst can be realized.

According to the first aspect of the invention, by holding the adsorbed oxygen amount at the saturated adsorption amount, it is possible to prevent the excessive enrichment of the air-fuel ratio. Further, the air-fuel ratio can be enriched according to the deterioration state of the three-way catalyst.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a fuel injection control device for an internal combustion engine in an embodiment.

FIG. 2 is a flowchart showing a fuel cut flag setting routine.

FIG. 3 is a flowchart showing a count routine of a delay counter CDFC.

FIG. 4 is a flowchart showing a count routine of a delay counter CDFB.

FIG. 5 is a flowchart showing an adsorbed oxygen amount calculation routine.

FIG. 6 is a flowchart showing a fuel injection amount calculation routine.

FIG. 7 is a timing chart more specifically showing the operation during fuel cut and during air-fuel ratio enrichment.

FIG. 8 is a flowchart showing a learning start determination routine.

FIG. 9 is a flowchart showing an A / F fluctuation control routine.

FIG. 10 is a flowchart showing a saturation determination routine.

FIG. 11 is a flowchart showing a saturated adsorption amount calculation routine.

FIG. 12 is a timing chart showing the output voltage of the O ₂ sensor and the target air-fuel ratio when learning the adsorption amount.

FIG. 13 is a map for calculating the substance concentration of the three-way catalyst from the air-fuel ratio.

FIG. 14 is a block diagram corresponding to a claim.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 7 ... Fuel injection valve, 13 ... Three-way catalyst, 26
... A / F sensor as an air-fuel ratio sensor, 32 ... Air-fuel ratio control means, fuel injection stop means, adsorbed oxygen amount calculation means, air-fuel ratio enrichment means, desorbed oxygen amount calculation means, CPU as saturated adsorption amount update means .

Continuation of the front page (56) Reference JP-A-6-200803 (JP, A) JP-A-5-26076 (JP, A) JP-A-6-159048 (JP, A) JP-A-6-17640 (JP , A) JP-A-5-163941 (JP, A) JP-A-4-342847 (JP, A) JP-A 64-36943 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) (Name) F02D 41/14 F01N 3/00

Claims (8)

(57) [Claims] 1. A three-way catalyst installed in an exhaust system of an internal combustion engine for removing harmful substances in exhaust gas, and an air-fuel ratio sensor for detecting an air-fuel ratio of an air-fuel mixture supplied to the internal combustion engine, A fuel injection valve for injecting and supplying fuel to the internal combustion engine; air-fuel ratio control means for controlling the fuel injection amount by the fuel injection valve so that the air-fuel ratio by the air-fuel ratio sensor becomes a target air-fuel ratio; a fuel injection stopping means under a predetermined condition based on the state to stop the fuel injection by the fuel injection valve, adsorbed oxygen amount for calculating the amount of oxygen adsorbed in the three-way catalyst in stopping the fuel injection by the fuel injection stop means a calculation unit, wherein the air-fuel ratio control means at the transition to the air-fuel ratio control by, based on adsorbed oxygen amount calculated by the adsorption oxygen amount calculating means from the fuel injection stop by the fuel injection stop means Temporarily and a air-fuel ratio enrichment means for setting the air-fuel ratio to the rich side, the three-way catalyst calculated by the adsorption oxygen amount calculating means can
Adsorbed oxygen amount of oxygen reaches the saturated adsorption amount of oxygen on the three-way catalyst
In this case, the adsorbed oxygen amount is held at the saturated adsorbed amount , the fuel injection control device for the internal combustion engine. 2. The adsorbed oxygen amount calculation means calculates the adsorbed oxygen amount of the three-way catalyst based on the amount of intake air into the internal combustion engine or the fuel injection stop time when the fuel injection is stopped by the fuel injection stop means. Item 2. A fuel injection control device for an internal combustion engine according to item 1. 3. A desorption oxygen amount calculation means for calculating an amount of oxygen desorbed from the three-way catalyst when the air-fuel ratio enrichment means enriches the air-fuel ratio, the air-fuel ratio enrichment means comprising: The air-fuel ratio is enriched based on a value obtained by subtracting the desorbed oxygen amount by the desorbed oxygen amount calculation device from the adsorbed oxygen amount by the oxygen amount calculation device.
2. A fuel injection control device for an internal combustion engine according to item 2. 4. The air-fuel ratio sensor is a linear air-fuel ratio sensor that linearly detects the air-fuel ratio, and the desorbed oxygen amount calculation means desorbs from the three-way catalyst based on the detection result of the air-fuel ratio sensor. The fuel injection control device for an internal combustion engine according to claim 3, which calculates an amount of oxygen to be stored. 5. The internal combustion engine according to claim 1, wherein the air-fuel ratio enriching means changes the degree of air-fuel ratio enrichment according to the adsorbed oxygen amount calculated by the adsorbed oxygen amount calculating means. Fuel injection control device. 6. A deterioration state of the three-way catalyst is detected and
The saturated adsorption amount is updated based on the deterioration state
The fuel injection control device for an internal combustion engine according to claim 1, further comprising a sum adsorption amount updating means . 7. Exhaust gas installed in an exhaust system of an internal combustion engine
A three-way catalyst for removing harmful substances in the air and the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine are linearly detected.
And a fuel injection valve for injecting and supplying fuel to the internal combustion engine.
And the air-fuel ratio measured by the linear air-fuel ratio sensor becomes the target air-fuel ratio.
To control the fuel injection amount by the fuel injection valve so that
The fuel ratio control means and the fuel injection under predetermined conditions based on the engine operating state.
Fuel injection stopping means for stopping fuel injection by the injection valve, and the three-way element when the fuel injection is stopped by the fuel injection stopping means
Adsorbed oxygen amount calculation means for calculating the amount of oxygen adsorbed on the catalyst
From the fuel injection stop by the fuel injection stop means
When the air-fuel ratio control by the ratio control means is made, the adsorption
Based on the amount of adsorbed oxygen calculated by the oxygen amount calculation means,
Air-fuel ratio enrichment means for temporarily setting the target air-fuel ratio to the rich side
And a fuel injection control device for an internal combustion engine.
Place 8. The air-fuel ratio enriching means comprises :
Is set on the rich side by 0.5 to 2.0% with respect to the target air-fuel ratio.
The combustion of the internal combustion engine according to claim 7, wherein
Charge injection control device.