JPH0246776B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Technical Field] The present invention relates to a fuel injection control device for an electronically controlled internal combustion engine that has an air-fuel ratio feedback system using an air-fuel ratio sensor (O ₂ sensor), and particularly relates to a fuel injection control device for an electronically controlled internal combustion engine having an air-fuel ratio feedback system using an air-fuel ratio sensor (O 2 sensor). The present invention relates to a fuel injection control device for an internal combustion engine that increases or decreases the amount of fuel supplied.

[Conventional technology]

In electronically controlled fuel injection internal combustion engines with an air-fuel ratio feedback system, this is installed in the engine exhaust system.
Feedback control of the fuel injection amount is performed according to the detection signal from an air-fuel ratio sensor such as an O ₂ sensor.

Also, during acceleration, the amount of fuel supplied is increased to compensate for the amount of fuel adhering to the intake port, etc. During deceleration, the above-mentioned adhering fuel vaporizes as the intake pipe negative pressure increases. The amount of fuel supplied is corrected to reduce the amount of fuel in consideration. (For example, Tokukai Sho
(Refer to Publication No. 55-35134) [Problems to be Solved by the Invention] However, in the conventional technology, fuel supply amount correction during acceleration and deceleration is always performed according to a fixed specification, and the accumulation of deposits on the intake valves and the like over time. changes and variations in fuel properties in the market, summer gasoline,
It was not possible to compensate for differences in fuel vaporization properties, such as differences in winter gasoline.

This is because the larger the amount of deposits attached to the intake valve, the more fuel will be attached to the deposits, resulting in a larger deviation in the air-fuel ratio during acceleration, and due to differences in the vaporization properties of the fuel, This is because the difference in air-fuel ratio at different times occurs.

Therefore, the purpose of the present invention is to prevent deviations in the air-fuel ratio during transient operation caused by changes in fuel properties over time, to improve drivability, and to suppress emissions of harmful components in exhaust gas. The objective is to provide a fuel injection control device that can

[Means to solve the problem]

Explaining according to FIG. 1, the fuel injection control device for an internal combustion engine according to the present invention includes an operating state detecting means 200 for detecting the operating state of the internal combustion engine, and an operating state detecting means 200 for detecting the operating state of the internal combustion engine. 201; a fuel supply amount calculation means for calculating the fuel supply amount;
air-fuel ratio detection means 202 for detecting the air-fuel ratio of the air-fuel mixture taken into the internal combustion engine; and feedback correction means for correcting the fuel supply amount with a feedback correction value based on the detection result of the air-fuel ratio detection means.
203, transient correction means 204 for correcting the fuel supply amount with a transient correction value when the operating state of the internal combustion engine is determined to be a transient operating state by the operating state detection means; A fuel injection control device for an internal combustion engine, comprising: a fuel supply means 205 for supplying the fuel supply amount corrected based on the transient correction means to the internal combustion engine; a first memory means 206 for storing the feedback correction value; a second memory means 207 for storing the transient correction value; and when the operating state detection means determines that the operating state of the internal combustion engine is a transient operating state, a first memory means 207 stores the transient correction value; A deviation calculation means 208 calculates the deviation between the feedback correction value stored in the means and the feedback correction value within a predetermined period after transition to over-bottom operation; Transient correction value updating means 209 for modifying and updating the transient correction value stored in the memory means
It is characterized by comprising:

[Effect]

The operating state detection means 200 detects the current operating state of the internal combustion engine, and based on the detection result, the fuel supply amount calculation means 201 calculates the basic fuel supply amount as a target value. The air-fuel ratio detection means 202 detects the air-fuel ratio of the air-fuel mixture taken into the internal combustion engine. Feedback correction means 203 corrects the fuel supply amount using a feedback correction value in response to the rich or lean signal detected by air-fuel ratio detection means 202.
The feedback correction value is stored in first memory means 206. The transient correction means 204 corrects the fuel supply amount using a transient correction value when a transient operating state is detected by the operating state detection means 200, and the transient correction value is stored in the second memory means 207. Also,
Deviation calculation means when a transient operating condition is detected.
208 calculates the deviation between the feedback correction value stored in the first memory means 206 during steady operation before transient operation and the current feedback correction value. The transient correction value updating means 209 corrects and updates the transient correction value stored in the second memory means 207 according to the deviation. Thus, the fuel supply means 205 supplies the internal combustion engine with the final fuel supply amount obtained by correcting the fuel supply amount calculated by the fuel supply amount calculation means 201 using the feedback correction value and the transient correction value.

The influence of deposits becomes noticeable during transient operation.

As the amount of deposits increases, the deviation in the air-fuel ratio during transient operation increases, and accordingly, a difference arises between the feedback correction value during transient operation and the feedback correction value during steady operation. In other words, the required value of the transient correction value changes. Therefore, by learning the transient correction value based on this difference, it is possible to match the transient correction value with the required value even in response to changes over time such as an increase in deposits.

〔Example〕

Examples will be described below with reference to the drawings.
In FIG. 2, 10 is an air cleaner, 12 is an air flow meter, 14 is a throttle valve, and 16 is a fuel injection valve, which are installed in this order in an intake pipe 18 of an internal combustion engine. 18 is a cylinder block, 20
is the cylinder head. cylinder block 18
A piston 22 is provided therein, and a combustion chamber 2 is provided above it.
4 is formed, and the electrode 25' of the spark plug 25 is provided facing thereto. The air-fuel mixture from the intake pipe 18 is introduced into the combustion chamber 24 when the intake valve 26 is opened. Exhaust gas is taken out from the combustion chamber 24 to an exhaust manifold 28. 30 is a fuel tank, 32 is a fuel pump, and the fuel injection valve 16 is connected via a fuel pipe 34.
supply fuel. 36 is a data distributor,
38 is an ignition coil connected to the ignition plug 25.

40 is a control circuit that controls the operating state. The control circuit 40 receives signals from various sensor groups as described below, and is informed of the current operating conditions of the engine. That is, a signal representing the amount of intake air is input from the air flow meter 12 via line ₁ . An O ₂ sensor 42 as an air-fuel ratio sensor is provided in the exhaust manifold 28 and applies an air-fuel ratio signal to the control circuit 36 via a line ₂ . Furthermore, the case 36 of the distributor 36
1 includes rotation angle sensors 44, 4 facing the rotation detection piece 363 on the distributor shaft 362.
6 is provided and connected to the control circuit via lines ₃ and ₄ . One of them 44 is for detecting the rotation speed of the distributor shaft 362, which outputs a large number of pulses during one rotation of the engine, and the other 46 is for cylinder discrimination, and also an interrupt signal that corresponds to the crank angle. plays a role in forming the A water temperature sensor 50 is provided so as to be in contact with the cooling water jacket of the cylinder block, and applies a signal to the control circuit 40 via a line ₅ . Throttle sensor 51 applies a signal corresponding to the opening degree of the throttle valve to the control circuit via line ₆ .

Figure 3 shows the configuration of the control circuit using a block diagram.
2 and water temperature sensor 50, throttle sensor 51
Other analog sensors not shown because they are not directly related to the present invention are the analog multiplexer 54.
and is converted into a binary signal by an A/D converter 56. A signal every 1/n crank angle of the engine from the rotation angle sensor 44 is converted by a speed signal forming circuit 58 into a binary signal corresponding to the speed of the engine, and is applied to an input port 59. A signal from the rotation angle sensor 46 for each engine rotation and a signal for each 1/n crank angle of the rotation angle sensor engine are sent to a timing generation circuit 60 and applied to the CPU 62 as an interrupt signal. _O2 sensor 42
The air-fuel ratio signal is compared with a reference level by the comparison amplifier circuit 66 and applied to the input port 59.

The analog multiplexer 54, A/D converter 56, and input port 59 are the components of the microcomputer system, such as the CPU 62, RAM 68,
It is connected to the ROM 70 via a bus 72. CPU62
synchronizes with the clock pulse from the clock generation circuit 74, takes in the detection signals from the sensor group and calculates the fuel injection amount, and the calculation result is
The signal is output from the CPU 62 to the output port 76 via the bus 72. The output port 76 is connected to the fuel injection valve 16 via a drive circuit 78 . CPU62 is
The fuel injection amount is calculated according to the program written in ROM70.

Before describing the software configuration of the present invention, the idea of the present invention will be explained with reference to FIG. In a fuel injection engine using an O ₂ sensor like the present invention, fuel injection control is performed as follows. Based on the engine operating conditions, for example, the rotation speed N and the intake air amount Q _a , the basic fuel injection amount t _p = C × (Q _a /
N) is calculated (C: constant). On the other hand _O2 sensor 4
2, the actual air-fuel ratio is detected. If the air-fuel ratio deviates to the rich side, the feedback correction coefficient FAF added to the basic injection amount t _p is decreased, while if the air-fuel ratio deviates to the lean side, the FAF
is increased, which causes a feedback to the air/fuel ratio. FIG. 4 schematically shows the state of this feedback. For example, at time _t1 , the signal of the O ₂ sensor 42 changes from rich 1 to lean 0.
When switched to , the feedback correction coefficient FAF is
As _R1 increases, the air-fuel mixture becomes richer, and the air-fuel ratio is corrected to a smaller value. Furthermore, at time _t2 , when the signal from the _O2 sensor 42 switches from lean to rich, the feedback correction coefficient becomes smaller as _R2 , and therefore the fuel injection amount decreases and the air-fuel ratio is corrected to a larger value. .
Due to the action of such feedback, the air-fuel ratio is maintained at the target value (A/F) ₀ as shown in (b). In addition, in order to hasten the convergence of the air-fuel ratio to the target value, the O ₂ sensor 4
It is also well known that when the signal No. 2 switches from rich to lean or from lean to rich, skips are inserted as indicated by S ₁ and S ₂ in FIG.

In the above-described operation, when the engine accelerates, the required fuel injection amount increases. In this case, since feedback alone cannot cope with this problem, it is attempted to keep the air-fuel ratio constant by increasing the amount of fuel by multiplying it by an acceleration correction coefficient. That is, it is detected that the engine is switching from steady state to acceleration, the acceleration correction coefficient is set from 1 to a predetermined value K of 1 or more, and the fuel injection amount is calculated including this. This is intended to maintain the air-fuel ratio constant even during transient operation. However, due to aging factors such as deposits as mentioned above, sufficient correction cannot be achieved simply by introducing an acceleration correction coefficient. That is, if the acceleration starts at time _t3 in Fig. 4, the air-fuel ratio shifts to lean as shown in X,
On the contrary, it may shift towards richness. The present invention focuses on the following points and aims to eliminate such fluctuations in the air-fuel ratio during transient operation. That is, if the air-fuel ratio has a roughness like X, the feedback correction amount FAF should change compared to the steady state. In other words, the deviation ΔA/F of the feedback correction amount during acceleration from the steady state is a measure of the roughness of the air-fuel ratio during acceleration operation. Therefore, if the acceleration correction coefficient is corrected according to this deviation, it is possible to suppress the roughness of the air-fuel ratio and make it uniform as indicated by Y in FIG. 4B.

The software configuration of the control circuit that implements the present invention will be explained below using a flowchart. In this embodiment, idling, which is the most stable operating condition, is taken as steady operation, and the deviation is calculated by comparing the amount of feedback correction when starting from idling with that when idling. However, it goes without saying that the idea of the present invention is not intended to be limited to this. The upper half of Fig. 5 mainly shows the feedback correction coefficient.
This relates to FAF skipping, and the lower half relates to learning correction of correction coefficients during acceleration and deceleration.

Reference numeral 100 in FIG. 5 indicates the start of the fuel injection amount calculation routine according to the present invention, and this routine is performed by the timing generation circuit 60 receiving signals from the rotation angle sensors 44 and 46 to output a signal at every predetermined crank angle of the engine. Execution begins. Then at 102
The CPU 62 calculates a basic injection amount t _p determined according to engine operating conditions. That is, the CPU 62 calculates t _p based on the engine speed N _e from the speed forming circuit 58 and the intake air amount Q _a from the air flow meter 12, and the calculation result is temporarily stored in the RAM 68.

At 104, the CPU determines whether the signal from the O ₂ sensor 42 is 1 or 0, that is, whether the air-fuel mixture is rich or lean. If No, ie, lean, the process proceeds to 106, where it is verified whether the air-fuel ratio flag _fO2 is 0 or not. This flag _fO2 is set to 0 when the air-fuel mixture changes from rich to lean, and set to 1 when the air-fuel mixture changes from lean to rich. A No result indicates that the air-fuel ratio was 1 last time, that is, a switch from rich to lean (t ₁ in FIG. 4D). At 107, the flag fO ₂ is reset to 0. In the next step 108, the feedback correction coefficient FAF is stored in the area f (A/F) of the RAM 68. That is, the value of FAF at the skip point _t1 in FIG. 4D (immediately before the skip) is stored as f(A/F). The meaning of this will be discussed later.
In the next step 110, the feedback correction coefficient FAF is stored in the RAM as the previous FAF plus 10. As a result, FAF is rapidly increased. That is, the point _t1 in FIG. 4 indicates the air-fuel ratio switching from rich to lean, and at that point the feedback correction coefficient FAF suddenly increases as shown at _S1 (so-called skip). It is well known that the followability of feedback is increased by such skip changes.

In the next step 112, the CPU receives a signal from the throttle position sensor 51 and determines whether the engine is idling. If we assume that it is currently idle, the result will be Yes, and the process will proceed to step 114. 1
14, the feedback correction coefficient f(A/F) for the current skip in 108 and the correction coefficient f(A/F) for the previous skip stored in the RAM 68 are entered.
The average with F)L is stored in RAM as f(A/F)M. That is, the skip point before the current skip point t ₁ is the switching point t ₀ from lean to rich, and the correction coefficient at that time is f(A/
F) It is L. f(A/F)M, which is the average of the correction coefficients for two adjacent skips, is the center value of the current FB control that includes factors such as deposits and other changes over time, and is used for correction calculation of the acceleration/deceleration correction coefficient. , is used as a reference value during steady operation (actually, the value immediately before transition to transient operation is adopted).

In step 118, f(A/F) calculated in step 108 is stored in the RAM area of f(A/F)L, and as already explained in step 114, this is the average f(A/F) of FAF.
F) Used as the FAF at the previous skip when calculating M.

At step 120, t _p ×FAF is calculated, and if an acceleration state is detected at step 121 based on the intake air amount change rate, throttle opening change rate, etc., then at step 122, the acceleration correction coefficient K is integrated, and the final fuel injection is performed. amount and is stored in RAM. At 123, this routine ends.

Next, when the CPU 62 starts executing the routine shown in FIG. 5, the air-fuel ratio flag fO ₂ =0 (106).
07) Therefore, the judgment is Yes. In 122
The new correction coefficient is FAF plus 1.
Therefore, the correction factor increases slowly as R ₁ in FIG. 4 until the next time the O ₂ sensor signal is reversed. In addition, the amount of change in the correction coefficient is expressed as 108 and 122.
The reason for setting it to 10.1 is only to explain that the former is large and the latter is small, and this number itself has no special meaning.

As the feedback correction coefficient FAF is gradually increased as indicated by R ₁ in FIG. 4, the air-fuel ratio changes to richer, and at time t ₂ the signal from the O ₂ sensor 42 changes from 0 to 1.
Switch to. Therefore, O ₂ =1, the determination at 104 is Yes, and the process proceeds to 130 . At 130, it is verified whether the air-fuel flag ratio fO ₂ is 1 or not. At the _t2 point where the signal of the O ₂ sensor 42 switches from 0 to 1, fO ₂ =
Since it is 0, it branches to No. Flag fO ₂ at 131
= 1. Next, in step 132, the feedback correction coefficient FAF is stored in the area f(A/F) of the RAM 68. This meaning is the same as 108.
In the next step 134, the feedback correction coefficient FAF is stored in the RAM 70 as the previous FAF minus 10. That is, the point _t2 in FIG. 4 indicates the air-fuel ratio switching from lean to rich, and at that point the feedback correction coefficient suddenly drops as shown at _S2 .
The significance of such a skip change is the same as described above.

Next, when the CPU 62 starts executing the routine shown in _FIG .
It is determined Yes and the process proceeds to 140. At 140, FAF minus 1 is set as a new correction coefficient. Therefore, the correction coefficient gradually decreases as indicated by R ₂ in FIG. 4D and is maintained until the signal from the O ₂ sensor 42 is reversed.

When acceleration starts from idling operation as described above, the signal of the throttle sensor 51 becomes t ₃ as shown in Fig. 4 A.
The CPU increases the acceleration amount at 121 and 122, and performs learning correction calculation of the acceleration correction coefficient. At this time, the determination at 112 in FIG. 5 changes to No, and the program proceeds to 150.
At 150, it is determined whether 5 seconds have elapsed since the start of acceleration. If No, that is, immediately after acceleration, proceed to 152 and calculate the feedback correction coefficient f for the current skip.
The average feedback correction coefficient f(A/F)M during idling is subtracted from (A/F), and this is temporarily stored in the RAM as the deviation ΔA/F. In other words, if the air-fuel ratio deviates to the lean side during acceleration as indicated by X in Figure 4 (b), then after skipping from the rich to lean switching point, the feedback correction value will be the average feedback correction coefficient f determined during idling.
(A/F) Starts to shift towards the larger side from M, for example t ₄
The signal from the O ₂ sensor 42 switches from lean to rich only when it reaches its maximum at the time of . In the next step 154, it is determined whether such deviation ΔA/F is within a predetermined range, for example, ±5%.
No, i.e. 15 if the deviation is not too large.
5, the value stored in the K' area of the RAM is set as the acceleration correction coefficient K during that operation. Therefore, in step 120, the total fuel injection amount is calculated by incorporating this acceleration correction coefficient.

If it is determined No in 150, i.e. more than or less than 5%, proceed to 156, and such 5%
The deviation above is determined to be positive or negative. 1 if positive
58, and stores the previous acceleration correction value K' plus 10% in order to correct the lean tendency. If it is negative, the process branches to 160, and the previous acceleration correction value K' minus 10% is stored in the RAM in order to correct the tendency to become rich. The RAM area that stores K' is configured as a nonvolatile RAM. Therefore, the acceleration correction coefficient calculated in this way is constantly revised and updated.

The total fuel injection amount τ calculated in this way, including feedback correction and acceleration correction, is 122.
The data is stored in a predetermined area of RAM, and when a predetermined crank angle is reached, the CPU outputs this data to port 7.
Set to 6. The fuel injection valve 16 is operated for a time corresponding to τ.

〔Effect of the invention〕

As explained above, according to the present invention, when transient operation is detected, the correction coefficient for transient operation is learned from the deviation between the feedback correction value stored during steady operation before transition to transient operation and the current feedback correction value. As a result, it is possible to identify the tendency of the air-fuel ratio to deviate to the lean side or rich side during transient operation and correct and update the correction coefficient using the feedback correction value stored during steady operation before transition to transient operation as a learning standard. Therefore, it is possible to eliminate deviations in the air-fuel ratio that occur due to changes over time such as adsorption of deposits to the bulk portion of the intake valve.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the basic configuration of the present invention, Fig. 2 is a diagram showing the configuration of an embodiment of the invention, Fig. 3 is a block diagram of the control circuit shown in Fig. 2, and Fig. 4 is a diagram showing the control circuit shown in Fig. 2. FIG. 5 is a schematic time chart of the operation of the device, and FIG. 5 is a flow chart showing the software configuration of the present invention. 12... Air flow meter, 14... Throttle valve, 16... Fuel injection valve, 18... Intake system, 4
0...Control circuit, 42... _O2 sensor.

Claims (1)

[Scope of Claims] 1. Operating condition detection means for detecting operating conditions of the internal combustion engine; Fuel supply amount calculation means for calculating the amount of fuel supplied to the internal combustion engine based on the detection result of the operating condition detection means; an air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture taken into the internal combustion engine; a feedback correction means for correcting the fuel supply amount with a feedback correction value based on the detection result of the air-fuel ratio detection means; and the normal operation state detection means. when it is determined by the means that the operating state of the internal combustion engine is in a transient operating state;
An internal combustion engine comprising: a transient correction means for correcting the fuel supply amount using a transient correction value; and a fuel supply means for supplying the internal combustion engine with the fuel supply amount corrected based on the feedback correction means and the transient correction means. In the fuel injection control device, the operating state of the internal combustion engine is determined to be a transient operating state by the first memory means for storing the feedback correction value, the second memory means for storing the transient correction value, and the operating state detecting means. If it is determined that
a deviation calculation means for calculating the deviation between the feedback correction value stored in the first memory means during the steady operation before the transient operation and the feedback correction value within a predetermined period after the start of the transient operation; 1. A fuel injection control device for an internal combustion engine, comprising: a transient correction value updating unit that corrects and updates a transient correction value stored in a second memory unit based on a calculation result.