JPH0610444B2 - Fuel injection amount control method for internal combustion engine - Google Patents

Description

The present invention relates to a fuel injection amount control method for an internal combustion engine, and
The present invention relates to a fuel injection amount control method suitable for controlling an air-fuel ratio of an air-fuel mixture according to an engine rotation speed and an engine load state.

[Conventional technology]

Conventionally, by controlling the amount of fuel supplied to the engine, an air-fuel mixture with an air-fuel ratio according to the engine load and rotational speed is provided to improve exhaust gas purification performance and improve engine output characteristics. The technology to do is known.

Further, in such control, if the air-fuel ratio is feedback-controlled to the stoichiometric air-fuel ratio based on the detection output of the oxygen concentration sensor in the exhaust gas, the exhaust gas purification performance is improved, while
It is also known that the output of the engine is improved by increasing the amount of fuel and making the air-fuel ratio richer than the stoichiometric air-fuel ratio.

For example, in the method disclosed in Japanese Patent Laid-Open No. 57-24435, the high load operating state of the engine is detected by the intake pipe negative pressure and the throttle valve opening degree, and the fuel injection amount (fuel supply amount) during high load operation is detected. ) Is increased. This increase correction is performed by giving a predetermined value to the increase coefficient at the time of calculating the fuel injection amount, but in an operating state in which the increase is not necessary, a predetermined reference value is given to this increase coefficient. Further, the feedback control to the stoichiometric air-fuel ratio is carried out on the condition that the increase value is a predetermined reference value.

Similarly, in the fuel injection device described in JP-A-55-78130, in order to perform more appropriate increase correction, a storage means is prepared in which the increase value is stored in advance using the engine load and engine speed as parameters, The increased value corresponding to the actual engine load and the rotational speed is read from the storage means, and the fuel injection amount is increased and corrected by this increased value. On the other hand, the feedback control to the stoichiometric air-fuel ratio is performed when this increase value is a predetermined value (= 0 or less than a predetermined value) that does not have an increase function.

[Problems to be Solved by the Invention]

In such a conventional technique, whether to be in the feedback region (whether to perform feedback control) is determined according to whether or not there is an increase value. In other words, since feedback control is performed when the increase value is a value that does not have an increase function, there is no choice but to have a correlation between the feedback region and the increase value, and therefore, due to the reason described in detail, There is a case where the increase value is not appropriate for the operating region of No. 1, and there is a problem that the engine output does not reach a preferable value in that specific region. Further, when the increase value is set to a suitable value, the increase value remains even in the region where the feedback control should be originally performed to the stoichiometric air-fuel ratio, and this time there is a problem that the feedback region is narrowed and exhaust gas characteristics deteriorate. .

It is also possible to perform feedback control while increasing with the increase value, but since the center of feedback control is on the decrease side by the amount corresponding to the fuel increase amount, the engine state changes in the feedback region and the increase value changes. Then, there is a problem that the air-fuel ratio is disturbed and exhaust gas purification performance is deteriorated until the feedback center for the increase value before change reaches the feedback center for the increase value after change.

These problems of the prior art will be further described with reference to the drawings.
For example, as the fuel increase value, the increase value α ₁ corresponding to the engine rotation speed N shown in FIG. 2 and the engine load state determined by the ratio between the intake air amount Q and the engine rotation speed N as shown in FIG. When the value obtained by adding the increase value β ₁ determined in accordance with is used, the increase value obtained as a result is as shown in FIG. It should be noted that FIG. 1 also shows a region where feedback control should be performed on the stoichiometric air-fuel ratio. In this example, the increased value (α
_{Since 1} + β ₁ ) is 0%, there is a drawback that the engine output becomes insufficient in the low speed and high load region. Therefore, by setting the increase values α ₂ and β ₂ shown by the chain lines in FIGS. 2 and 3 as the increase values, the increase values (α ₂ + β ₂ ) Is set to be scattered, the lack of engine output can be resolved.

However, as is clear from FIG. 5, since the increase value also exists in the feedback region to the stoichiometric air-fuel ratio, according to the above-mentioned conventional technique that defines the region without the increase value as the feedback region, the feedback region is It is limited to a narrow range, and the exhaust gas purification performance deteriorates. Further, if feedback is performed while the amount is increased, the center of the air-fuel ratio is deviated as described above, so that the exhaust gas purification performance deteriorates when the operating state changes.

Further, as shown in FIG. 4, the increase value is stored in correspondence with the engine load (intake air amount Q / engine speed N) and the engine speed N, and the actual load and speed are stored. Accordingly, the same problem occurs when the value calculated by two-dimensional interpolation from FIG. 4 is used as the increase value.
In other words, since the increase value is obtained by two-dimensional interpolation,
It is difficult to set the increase value to 0 in the entire feedback area including the boundary between the feedback area and the increase area.

For example, in FIG. 4, in the feedback area,
Consider a grid point A adjacent to the boundary line of the feedback area, a grid point B in the feedback area at the same engine speed as the grid point, and an intersection C between the engine load and the engine speed that defines the feedback area.

In the conventional technique that determines that the amount of increase is 0 in the feedback region, the amount of increase at point B must be 0, but since there is an amount of increase (≠ 0) at point A, points B and C
On the line segment BC determined by, there is a certain increase value.

Moreover, if an increase amount on the line segment AC determined by the points A and C is properly determined, the point B becomes a value other than 0.
For example, assuming that the line segment AC and the line segment BC are equal in length,
If the preferable increase value at the point A is 10% and the preferable increase value at the point C is 8%, the increase value at the point B must be set to 6%.

As described above, if an attempt is made to appropriately adjust the increase value by using the two-dimensional interpolation, a virtual increase value is required also in the feedback area, and as a result, the increase value remains in the feedback area. Problem occurs.

In short, if the relationship between the engine load, the engine speed, and the increase value is determined so that the appropriate necessary increase value is obtained, the increase value will remain in the feedback region, but
It is an object of the present invention to prevent the exhaust gas purification performance from being narrowed or the exhaust gas purification performance being deteriorated when the operating state changes during the feedback even if such an increase value is set.

In order to achieve the above object, the present invention provides a feedback correction value based on an oxygen concentration sensor output for feedback controlling the fuel injection amount so that the air-fuel ratio of the air-fuel mixture supplied to the engine becomes the stoichiometric air-fuel ratio, and the air-fuel mixture. A fuel injection amount control method for increasing the fuel injection amount so that the air-fuel ratio becomes a rich air-fuel ratio, and a fuel injection amount control method for an internal combustion engine that corrects the fuel injection amount by using the feedback control. The engine load and the engine speed that define the area are stored in advance, and the relationship between the engine load and the engine speed and the fuel increase value, which is set independently of the feedback area, is stored in advance, and The fuel increase value calculated by the relationship is set to take a value for increasing and correcting the fuel injection amount also in the feedback region. The detected actual engine load and the actual engine speed, and the stored relationship to calculate the actual fuel increase value, the detected actual engine load and the actual engine speed, and By comparing the engine load and the engine speed that define the stored feedback region, it is determined whether or not the actual operating state is within the feedback control region, and if it is determined that it is within the feedback region, then The calculated increase value is changed to a value at which the fuel injection amount is not corrected, and when it is determined that the fuel injection amount is not within the feedback region, the feedback correction value is set to a value at which the fuel injection amount is not corrected. Take the way.

[Action]

The relationship between the engine load and engine speed and the increase value is
In a region where a predetermined rich air-fuel ratio is required, the fuel increase value necessary to achieve the rich air-fuel ratio is obtained and set (stored) independently of the feedback region and stored. In other words, even if the increase value is allowed to exist in the feedback region, the engine load, the engine speed, and the increase amount should be adjusted so that the increase value becomes appropriate in a predetermined operating condition that requires a predetermined rich air-fuel ratio. A value relationship is set and stored in advance. In other words,
The fuel increase value is configured to be determined prior to the feedback region.

Then, if the actual engine load and engine speed are within the feedback region, the calculated fuel increase value at that time is calculated as a value having a function of increasing the fuel injection amount.

Therefore, in the present invention, by comparing the actual engine load and the engine speed with the engine load and the engine speed that define a feedback region that is stored in advance, it is determined whether the actual operating region is in the feedback region. Whether the increase value is present or not is determined, and if the actual operation area is in the feedback area, the increase value obtained at that time is reset to a value without the increase function.

Therefore, when in the feedback region, the fuel injection amount is substantially corrected by the feedback correction value and is not corrected by the increase value, and suitable feedback control is possible. , Fuel injection amount increase correction based on an appropriate amount increase amount is executed.

〔Example〕

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 6 shows the configuration of a system to which the present invention is applied.

In FIG. 6, the intake system of the engine 10 is provided with an air flow meter 12, a throttle valve 14, etc.
The air taken in via the air flow meter 12 is supplied to the intake manifold 16 via the throttle valve 14 and mixed with the fuel injected from the fuel injection valve 18. The air-fuel mixture is supplied to the combustion chamber 22 via the intake valve 20, burned by the ignition plug 26 provided in the cylinder head 24, and discharged to the exhaust system via the exhaust valve 28. The exhaust system is provided with an oxygen concentration sensor (hereinafter referred to as O ₂ sensor) 30 that detects the oxygen concentration in the exhaust gas. When the air-fuel ratio of the air-fuel mixture is feedback controlled to near the stoichiometric air-fuel ratio based on the detection output of the O ₂ sensor, the exhaust gas contained in the exhaust gas is purified by a three-way catalyst (not shown) provided in the exhaust system. Are discharged.

Further, the cylinder block 32 is provided with a water temperature sensor 34 for detecting the engine water temperature.

The distributor 38, which distributes the ignition signal from the igniter 36 to each cylinder, has a cylinder discrimination sensor 40 and a rotation angle sensor 42 built therein.

Air flow meter 1 for detecting various engine operating conditions
The detection outputs of various sensors such as 2, the O ₂ sensor 30 are supplied to the control device 44.

FIG. 7 shows the configuration when a microcomputer is used as the control device 44.

The controller 44, as shown in FIG.
0, RAM 52, ROM 54, input / output ports 56, 5
8, output ports 60 and 62, A / D converter 64, multiplexer 66, drive circuits 68 and 70, waveform shaping circuit 7
2, composed of an input circuit 74, CPU 50, R
The AM 52, the ROM 54, the input / output ports 56 and 58, and the output ports 60 and 62 are connected by a bus line 76, respectively.

The detection outputs of the air flow meter 12 and the water temperature sensor 34 are supplied to the input / output port 56 via the multiplexer 66 and the A / D converter 64. Detection outputs of the cylinder discrimination sensor 40 and the rotation angle sensor 42 are supplied to the input / output port 58 via the waveform shaping circuit 72. The detection output of the O ₂ sensor 30 is supplied to the input / output port 58 via the input circuit 74.

The igniter 36 can supply an ignition signal to the distributor 38 by a control signal supplied through the output port 60 and the drive circuit 68. The fuel injection valve 18 is
The fuel injection time can be controlled by the control signal supplied via the output port 62 and the drive circuit 70.

Further, in the ROM 54, in addition to the numerical data of the increase values α ₂ and β ₂ shown in FIG. 2 and FIG. 3, the engine speed and engine load value that define the feedback region, the fuel injection amount control is necessary. Information is stored.

In the present embodiment, the increase value is obtained as (α ₂ + β ₂ ) as in the case of the post-operation, so that the calculated increase value takes a value as shown in FIG. That is, the relationship between the engine load and the number of revolutions and the increase value is set and stored so that the appropriate increase value can be obtained even in the low speed and high load range where the increase is required.
At this time, the relationship is determined irrespective of the feedback area indicated by the slanted lines in FIG. 5, and therefore, the increase value remains in the feedback area.

Further, in the present embodiment, the engine load condition is determined according to the ratio of the intake air amount Q and the engine rotation speed N, so that the engine load shown in FIG. The load state of the engine is determined based on the detection output of the meter 12 and the detection output of the rotation angle sensor 42.

FIG. 9 shows a flow chart in the case of performing the air-fuel ratio control according to the operating state of the engine by the system shown in FIG. 6 in which the present invention is commonly used.

In FIG. 9, first, at step 100, the increase value f ₁ according to the engine speed N and the engine load is calculated from the detection outputs of the rotation angle sensor 42 and the air flow meter 12. Specifically, α _{2 of} FIG. 2 stored in advance is stored.
And the actual engine speed to obtain the increase value α,
The increase value β is obtained from β _{2 in} FIG. 3 and the actual engine load (Q / N), and (α + β) is calculated as the increase value.

In step 102, it is determined whether the engine load region belongs to the feedback region. The determination in this step is made based on the map data of the engine load region shown in FIG. 8 based on the detection output of the air flow meter 12 and the rotation angle sensor 42 whether or not the engine load region belongs to the feedback region. If YES is determined in this step, the process proceeds to step 104, and the increase value f ₁ calculated in step 100 is set to 0. After that, the routine proceeds to step 106, where a correction value f ₂ for feedback controlling the air-fuel ratio of the air-fuel mixture to near the stoichiometric air-fuel ratio is calculated based on the detection output of the O ₂ sensor 30. The correction value f ₂ is calculated as a correction value for the basic fuel injection amount calculated based on the outputs of various sensors such as the air flow meter 12 and the water temperature sensor 34. After the process of step 106, the process proceeds to step 108. In step 108, the fuel injection time τ obtained from the fuel injection time τ × (1 + f ₁ ) × f ₂ determined corresponding to the basic fuel injection amount is calculated, and the fuel injection valve 18 is controlled. In the process in step 108 in this case, since the increase value f ₁ is set to 0 in step 104,
The air-fuel ratio of the air-fuel mixture is feedback-controlled to the vicinity of the stoichiometric air-fuel ratio based on the detection output of the O ₂ sensor 30 without increasing and correcting the fuel injection time by the increase value f ₁ to remove harmful gas contained in the exhaust gas. Can be purified.

On the other hand, if NO in step 102, the routine proceeds to step 110, where a correction value f ₂ for feedback control of the air-fuel ratio of the air-fuel mixture to near the stoichiometric air-fuel ratio based on the detection value 6 of the O ₂ sensor 30. Is set to 1 and the process proceeds to step 108. In step 108, the variable injection time τ × corresponding to the basic fuel injection time as in the above processing
The fuel injection time τ obtained from (1 + f ₁ ) × f ₂ is calculated and the fuel injection valve 18 is controlled. Since the correction value f ₂ of the fuel injection time τ at this time is set to 1 in step 110, the increase value f calculated in step 100 is calculated.
_The fuel injection valve 18 is controlled by the fuel injection time τ based on ₁ . Therefore, since the fuel amount is increased even at low speed and high load, it is possible to prevent the engine output from decreasing at low speed and high load.

〔The invention's effect〕

As described above, according to the present invention, the amount of increase can be set freely regardless of the feedback region, so that the amount of the amount of increase in the region requiring the amount of increase can be appropriately set and feedback control can be performed. In the required area, even if there is a calculated increase value, it is changed to a value that does not have an increase function and fuel injection amount control is executed, so it is possible to prevent deterioration of exhaust gas purification performance, It is possible to both improve output characteristics and prevent deterioration of exhaust gas characteristics.

[Brief description of drawings]

FIG. 1 is an engine load region characteristic diagram determined from the relationship between engine speed and load, FIG. 2 is a diagram showing the relationship between engine speed and amount of increase, and FIG. 3 is intake air amount / engine speed. FIG. 4 is a diagram showing a relationship with an increase value, FIG. 4 is a diagram showing a relationship between engine rotation speed and intake air amount / engine rotation speed, and FIG. 5 is an engine load determined from a relationship between engine rotation speed and engine load. FIG. 6 is a region characteristic diagram, FIG. 6 is a system configuration diagram of an internal combustion engine to which the present invention is applied, and FIG.
Configuration diagram for explaining the configuration of the control device shown in FIG.
FIG. 9 is an engine load region characteristic diagram determined from the relationship between engine speed and engine load according to the present invention, and FIG. 9 is a flowchart for explaining the operation according to the present invention. 10 ... Engine, 12 ... Air flow meter, 18 ... Fuel injection valve, 30 ... O ₂ sensor, 34 ... Water temperature sensor, 42 ... Rotation angle sensor, 44 ... Control device.

Claims (1)

[Claims] 1. A feedback correction value based on the output of an oxygen concentration sensor that feedback-controls the fuel injection amount so that the air-fuel ratio of the air-fuel mixture supplied to the engine becomes a stoichiometric air-fuel ratio, and the air-fuel ratio of the air-fuel mixture is rich air A fuel injection control method for an internal combustion engine, which corrects a fuel injection amount using a fuel increase value for increasing and controlling a fuel injection amount so that a fuel ratio is obtained, wherein an engine load and an engine speed that define a feedback region for feedback control are provided. The number is stored in advance and set independently of the feedback area,
The relationship between the engine load and the engine speed and the fuel increase value is stored in advance, and the fuel increase value calculated by the relationship has a value for increasing and correcting the fuel injection amount also in the feedback region. The actual engine load and the actual engine speed that have been set are calculated, and the actual fuel increase value is calculated using the stored relationship and the detected actual engine load and the actual engine speed. And the engine load and engine speed that define the stored feedback region are compared to determine whether the actual operating state is within the feedback control region, and when it is determined that the actual operating state is within the feedback region. Changes the calculated increase value to a value that does not increase the fuel injection amount and determines that it is not within the feedback range. When the can, the feedback correction value, the fuel injection quantity control method for an internal combustion engine and sets a value that does not correct the fuel injection amount.