JP3453819B2 - Engine air-fuel ratio control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine air-fuel ratio controller, and more particularly to an air-fuel ratio sensor such as a linear O ₂ sensor which produces an output substantially proportional to the air-fuel ratio of a mixture supplied to a combustion chamber in an exhaust system. The present invention relates to an engine air-fuel ratio control device which is installed and feedback-controls the air-fuel ratio to a target value based on the output of the air-fuel ratio sensor.

[0002]

2. Description of the Related Art In an engine for an automobile or the like, air-fuel ratio control is performed for maintaining an air-fuel ratio of a mixture supplied to a combustion chamber at a predetermined target value for the purpose of improving fuel efficiency. In this air-fuel ratio control, an O ₂ sensor for detecting the residual oxygen concentration in the exhaust gas is installed in the exhaust passage, and the output of the sensor is a predetermined target value (for example, theoretical air-fuel ratio; fuel / air = 14.7). The fuel supply amount is reduced when a richer state (fuel is richer) is shown, and the fuel supply amount is increased when the sensor output is leaner than the target air-fuel ratio (fuel is lean). By
It is performed so that the air-fuel ratio converges to a target value. In this case, as the O ₂ sensor, a so-called lambda sensor is generally used in which the output suddenly changes when the value of the excess air ratio (air-fuel ratio / theoretical air-fuel ratio) λ is 1.

On the other hand, in recent years, lean burn type engines are being put to practical use in order to further improve fuel efficiency. In this lean burn type engine, there is one in which the target value of the air-fuel ratio control is set to a different value depending on the operating region.In this case, in the specific operating region, the target value is considerably higher than the theoretical air-fuel ratio. A lean value (for example, air-fuel ratio = 22.0) is adopted. Therefore, in controlling the air-fuel ratio of such an engine, a linear air-fuel ratio sensor that produces an output substantially proportional to the air-fuel ratio, generally a linear O ₂ sensor, is used as the air-fuel ratio sensor.

However, for example, when feedback control of the air-fuel ratio is performed using a linear O ₂ sensor, if the feedback target value is changed at the same time when the target air-fuel ratio is changed, the following problems will occur. become.

That is, assuming that feedback control of the air-fuel ratio is performed in the lean burn region (hereinafter referred to as the Lb region), the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber becomes the output of the linear O ₂ sensor. Based on this, feedback control is performed so as to maintain a predetermined target value (for example, 22.0). Then, assuming that the operating state changes from this state and shifts to an operating region (hereinafter referred to as the λ1 region) in which the theoretical air-fuel ratio (λ = 1) is the target value, the air-fuel mixture supplied to the combustion chamber becomes empty. The fuel supply amount is adjusted so that the fuel ratio becomes the stoichiometric air-fuel ratio. In that case, the fuel supplied to the combustion chamber burns and the exhaust gas generated at that time is the linear O ₂ sensor in the exhaust passage. There will be a time lag before reaching the installation position. In this case, since the atmosphere near the linear O ₂ sensor at the time of zone transition is in a lean state, the fuel supply amount is significantly increased in an attempt to converge the air-fuel ratio to a new target value that has been changed. . Then, when the exhaust gas due to the increased fuel reaches the linear O ₂ sensor through the exhaust passage, the atmosphere around the sensor becomes overrich, so that the fuel supply amount is greatly reduced this time. .
As a result, the air-fuel ratio is excessively hunted, and the convergence to the target value is extremely deteriorated.

To solve this problem, for example, Japanese Patent Laid-Open No. 62-
As disclosed in Japanese Patent Laid-Open No. 182456, when the target air-fuel ratio is changed, there is one that performs feedback control of the air-fuel ratio using the target value before the change until a predetermined period elapses.

However, since the exhaust gas discharged from the combustion chamber is mixed in the process of passing through the exhaust passage, the output value of the linear O ₂ sensor actually shows a value that is less than the set air-fuel ratio. Become. Therefore, for example, even if the feedback target value is switched at the timing when the exhaust gas after the change of the target air-fuel ratio reaches the installation position of the linear O ₂ sensor, the sensor output value does not properly correspond to the feedback target value. As a result, air-fuel ratio fluctuations occur, leaving room for improvement in ensuring the followability of feedback control when the target air-fuel ratio is changed.

Therefore, in consideration of the above points, when changing the target air-fuel ratio, a predetermined delay time is provided, and the changed target air-fuel ratio is reflected as the previous value as a feedback target value. It is considered to use a weighted average value.

According to this, the feedback target value changes corresponding to the temporal change of the output value of the linear O ₂ sensor, and excessive fluctuation of the air-fuel ratio at the time of changing the target air-fuel ratio is prevented. Is expected.

[0010]

However, it has been found that the following problems occur because the control constants such as the delay amount and the weighted average coefficient have been set uniformly in the prior art.

That is, taking a linear O ₂ sensor as an example, the residual oxygen concentration in the exhaust gas is not exactly proportional to the air-fuel ratio, and as shown by the solid curve in FIG. The larger the value, the smaller the degree of increase in the residual oxygen concentration.

Assuming that the exhaust gas generated when the air-fuel ratio of 22.0 burns and the exhaust gas generated when the air-fuel ratio of 14.7 burns 1: 1. Assuming that the residual oxygen concentration when mixed at a ratio of ₂ is Da, the detected value S of the air-fuel ratio obtained from the output value of the linear O ₂ sensor comes to where the horizontal line passing through the concentration Da intersects with the characteristic curve.

On the other hand, the actual value R of the air-fuel ratio at that time is indicated by a broken line between the point on the characteristic curve corresponding to the air-fuel ratio of 14.7 and the point on the characteristic curve corresponding to the air-fuel ratio of 22.0. When tied, the broken line is located at the intersection of the horizontal line passing through the concentration Da, so that the detected value S of the air-fuel ratio is the actual value R.
Since the value is relatively richer than the above value, the following problems will occur during the transition.

That is, in the above example, for example, when the operating state changes from the Lb region to the λ1 region, as shown in FIG. 9, the final target air-fuel ratio is set to the previous value after the elapse of a predetermined time T0 from the zone transition. It is assumed that the target air-fuel ratio A / F (o) is changed as shown by the solid line by reflecting and performing the weighted average processing. In this case, the measured air-fuel ratio A / F (s) obtained from the output of the linear O ₂ sensor shows a value on the rich side of the target air-fuel ratio A / F (o) as indicated by the broken line. Therefore, the measured air-fuel ratio A / F (s) becomes the final target air-fuel ratio before the target air-fuel ratio A / F (o) becomes the final target air-fuel ratio, and the actual air-fuel ratio A / F as shown by the chain line.
(R) hardly converges to the final target air-fuel ratio.

On the other hand, when the operating state changes from the λ1 region to the Lb region, as shown in FIG. 10, the target air-fuel ratio A / F (o) is indicated by a solid line after a lapse of a predetermined time T0 from the zone transition. It is supposed to change. Also in this case, the measured air-fuel ratio A / F (s) obtained from the output of the linear O ₂ sensor is the target air-fuel ratio A / F as shown by the broken line.
It indicates a value on the rich side with respect to (o). Therefore, even if the target air-fuel ratio A / F (o) reaches the final target air-fuel ratio, the measured air-fuel ratio A / F (s) does not become the final target air-fuel ratio, and the actual air-fuel ratio A / F (r) greatly overshoots the final target air-fuel ratio.

According to the present invention, the target air-fuel ratio is changed by feedback control of the air-fuel ratio using a linear air-fuel ratio sensor that produces an output that is substantially proportional to the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber. The above situation is dealt with at the time, and an object thereof is to prevent deviation of the air-fuel ratio due to feedback control.

[0017]

That is, the invention of claim 1 of the present application (hereinafter referred to as the first invention) is a linear air-fuel ratio that produces an output that is substantially proportional to the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber. With the sensor installed in the exhaust system, in an engine configured to feedback control the air-fuel ratio based on the output of the linear air-fuel ratio sensor so that a plurality of target air-fuel ratios are realized, when the target air-fuel ratio is changed, In addition to gradually changing the target air-fuel ratio, when changing the target air-fuel ratio from the lean side to the rich side, a target air-fuel ratio changing means for increasing the change speed as compared with the case of changing from the rich side to the lean side is provided. , And the previous setting of the target air-fuel ratio
Providing a weighted average processing means for reflecting the values and performing a weighted average
At the same time, the target air-fuel ratio changing means is used for the weighted average processing.
Change the target air-fuel ratio by changing the weighted average coefficient
It is characterized in that it is configured to change the degree .

The invention of claim 2 of the present application (hereinafter referred to as the second
Is called the invention) for the air-fuel ratio of the mixture supplied to the combustion chamber.
Exhausting a linear air-fuel ratio sensor that produces a nearly proportional output
Along with being installed in the system, multiple target air-fuel ratios can be achieved.
Based on the output of the linear air-fuel ratio sensor.
Smell engine with feedback ratio control
Gradually change the target air-fuel ratio when changing the target air-fuel ratio.
And change the target air-fuel ratio from the lean side to the rich side.
When changing from the rich side to the lean side,
By providing a target air-fuel ratio changing means for increasing the above changing speed,
And delay means for delaying the timing of changing the target air-fuel ratio,
When changing the target air-fuel ratio from the lean side to the rich side,
The above delay compared to changing from rich side to lean side
A delay time correction means for shortening the time is provided .

The invention of claim 3 of the present application (hereinafter referred to as the third invention) is the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber.
A linear air-fuel ratio sensor that produces an output almost proportional to
Achieves multiple target air-fuel ratios when installed in the air system
Based on the output of the linear air-fuel ratio sensor
For engines with feedback control of fuel ratio
The target air-fuel ratio is gradually changed when the target air-fuel ratio is changed.
And change the target air-fuel ratio from lean side to rich side
When changing from the rich side to the lean side,
In all, target air-fuel ratio changing means to increase the above changing speed is installed.
And add the set value of the target air-fuel ratio by reflecting the previous value.
A weighted average processing means for weighted average is provided and the target air-fuel
A weighted average coefficient used in the weighted average processing by the ratio changing means.
Change the target air-fuel ratio change speed by changing the
Furthermore, when the target air-fuel ratio is changed from the lean side to the rich side, a delay means for delaying the change time of the target air-fuel ratio and the delay time compared to the case of changing from the rich side to the lean side are provided. A delay time correction means for shortening the delay time is provided.

[0020]

According to the above construction, the following operation can be obtained.

That is, in any of the first to third inventions, during the feedback control of the air-fuel ratio using the linear air-fuel ratio sensor, when the target air-fuel ratio is changed, the target air-fuel ratio is gradually changed and Since the change speed is faster when changing the target air-fuel ratio from the lean side to the rich side than when changing from the rich side to the lean side, the target air-fuel ratio changes to the output characteristics of the linear air-fuel ratio sensor. Since they substantially coincide with each other, deviation of the air-fuel ratio due to feedback control is prevented, and good air-fuel ratio control performance can be obtained.

According to the first and third aspects of the invention, the above operation can be realized only by changing the weighted average coefficient used when changing the target air-fuel ratio.

Further, according to the second and third aspects of the invention, when the target air-fuel ratio is changed from the lean side to the rich side, a new target air-fuel ratio is obtained as compared with the case where the rich side is changed to the lean side. Since the time to change is shortened, the target air-fuel ratio more accurately corresponds to the output characteristics of the linear air-fuel ratio sensor, and the deviation of the air-fuel ratio due to feedback control can be prevented more reliably, and even better. Air-fuel ratio control performance can be obtained.

[0024]

EXAMPLES Examples of the present invention will be described below.

As shown in FIG. 1, an engine 1 according to this embodiment has an intake passage 5 and an exhaust passage 6 which communicate with a combustion chamber 4 via intake and exhaust valves 2 and 3. In the intake passage 5,
From the upstream side, the air cleaner 7, the air flow sensor 8, the throttle valve 9, the surge tank 10, and the fuel injection valve 1
1 is provided. On the other hand, the exhaust passage 6 is provided with a catalytic converter 12 of a three-way catalytic type, and a linear O ₂ sensor 13 is provided upstream of the catalytic converter 12.
Is installed. Here, the linear O ₂ sensor 13 is adapted to detect the residual oxygen concentration in the exhaust gas and generate an output voltage substantially proportional to the concentration.

In this embodiment, the intake passage 5 is divided into a main passage 5a and a sub passage 5b by a partition wall 14 provided on the downstream side of the surge tank 10, and the downstream end side of the partition wall 14 is formed. A shutter valve 15 which is disposed in the sub-passage 5b and opens and closes the sub-passage 5b;
A diaphragm type actuator 16 for driving the actuator and an electromagnetic three-way valve 17 for switching supply and discharge of operating pressure to and from the actuator 16 are provided. The actuator 16 is provided with first and second pressure chambers 16b and 16c defined by a diaphragm 16a. Of these, the first pressure chamber 16a includes a surge tank 10
The intake negative pressure is constantly supplied via a branch passage 19 branched from a negative pressure passage 18 led from the valve to the electromagnetic three-way valve 17. On the other hand, through the control passage 20 provided between the second pressure chamber 16b and the electromagnetic three-way valve 17,
Intake negative pressure is introduced. Then, when the electromagnetic three-way valve 17 is turned on, atmospheric pressure is introduced into the second pressure chamber 16b through the control passage 20, whereby the actuator 16 is actuated and the shutter is opened as shown by the chain line in the figure. The valve 15 is opened and the sub passage 5b is opened.

Further, the engine 1 is provided with an electronically controlled control unit (hereinafter referred to as ECU) 30. The ECU 30 includes an intake air temperature signal from an intake air temperature sensor 31 that detects an intake air temperature, an air flow rate signal from an air flow sensor 8, a throttle opening degree signal from a throttle opening degree sensor 32 that detects an opening degree of a throttle valve 9, An air-fuel ratio signal from the linear O ₂ sensor 13, an engine speed signal from a rotation sensor 33 that detects the engine speed, a water temperature signal from a water temperature sensor 34 that detects the engine water temperature, and the like are input. Then, the ECU 30
The open / closed state of the shutter valve 15 and the fuel injection amount from the fuel injection valve 11 are controlled based on the above signals.

Here, the shutter valve 15 performed by the ECU 30
The opening / closing control and the fuel injection control will be briefly described. The former opening / closing control of the shutter valve 15 is performed as follows.

That is, the ECU 30 controls the engine speed Ne.
Based on the throttle opening θ and the throttle opening θ, it is determined which of the regions shown in FIG. 2 the current operating region belongs to. Then, when it is determined that it belongs to the open region set to the low rotation light load side, the electromagnetic three-way valve 17 is turned on. As a result, the shutter valve 15 is opened, and the air taken in through the air cleaner is sucked into the combustion chamber 4 through the surge tank 10 and both the main passage 5a and the sub passage 5b. On the other hand, when the ECU 30 determines that the operating region belongs to the closed region set in the remaining region excluding the closed region, the ECU 30 sets the electromagnetic three-way valve 17 to OF
Let it be F. As a result, the shutter valve 15 is closed and the sub-passage 5b is shut off.
The air passing through the combustion chamber 4 passes through only the main passage 5a.
Will be inhaled.

On the other hand, the latter fuel injection control is performed as follows.

The ECU 30 calculates the amount of air taken into the combustion chamber 4 per cycle, that is, the charging efficiency Ce from the engine speed Ne and the air flow rate Q indicated by the signal from the air flow sensor 8, and at the same time, the charging efficiency Ce. The basic injection time Tp that achieves a predetermined target air-fuel ratio is set based on

Here, as shown in FIG. 3, the operating region indicated by the engine speed Ne and the throttle opening θ is an enriched region set on the high load side (hereinafter referred to as Er region).
If it is determined that the air-fuel ratio is 12.
When the basic injection time Tp is set to 0, and when it is determined that the basic injection time Tp belongs to the Lb region set to the low rotation light load side, the basic injection time Tp is set to the air-fuel ratio of 22.0. Will be done. And the remaining λ1
When it is determined to belong to the region, the basic injection time Tp is set so that the theoretical air-fuel ratio becomes 14.7.

Next, the ECU 30 determines whether or not the air-fuel ratio feedback control condition is satisfied. That is, the ECU 30 determines when the operating region belongs to either the Lb region or the λ1 region indicated by hatching in FIG. 3 and the engine water temperature indicated by the signal from the water temperature sensor 34 becomes equal to or higher than a predetermined value. It is determined that the feedback condition is satisfied, and feedback control is executed.

That is, the ECU 30 converts the output voltage of the linear O2 sensor 13 into a measured air-fuel ratio A / F (s) by comparing it with a predetermined map, and then measures the measured air-fuel ratio A /
F (s) is compared with the target air-fuel ratio A / F (o) (14.7 or 22.0). And the measured air-fuel ratio A / F
When it is determined that (s) is leaner than the target air-fuel ratio A / F (o), the feedback correction coefficient Cfb is set so that the fuel is increased, while the measured air-fuel ratio A / F is set.
When it is determined that (s) is richer than the target air-fuel ratio A / F (o), the feedback correction coefficient Cfb is set so that the fuel is reduced . Further, if necessary, other correction coefficients are obtained, the basic injection time Tp is multiplied by these correction coefficients, and then the final injection time Ti is determined in consideration of the invalid injection time Tv. Then, the drive signal corresponding to the final injection time Ti is output to the fuel injection valve 11.

In this embodiment, when the operating range of the engine 1 shifts from the Lb range to the λ1 range or from the λ1 range to the Lb range, the target air-fuel ratio is changed as shown in the flowchart of FIG. It is supposed to be done.

That is, the ECU 30 determines in step S1 whether or not the zone shifts, and if YES is determined, step S2 is executed to compare the engine speed Ne and the throttle opening θ with the basic delay amount map. Thus, the basic delay amount Db is set. This map is for the engine rotational speed Ne, the engine speed Ne as shown in FIG. 5 (a) is set as A higher basic delay amount Db decreases, and for even throttle opening theta, 5
Throttle opening as shown in (b) theta is set to be smaller size Ihodo basic delay amount Db.

Next, the ECU 30 determines in step S3 whether or not the zone shift is from the Lb region to the λ1 region, and if YES is determined, the predetermined first delay correction amount D1 is read in step S4. , Step S5 is executed to add the first delay correction amount D1 to the basic delay amount Db obtained in step S2 to determine the final delay amount De, and the weighted average used in the weighted averaging process described later in step S6. The first coefficient value K1 is set as the coefficient K.
On the other hand, when the ECU 30 determines NO in step S3, that is, when the transition from the λ1 region to the lean region is determined, the predetermined second value is determined in step S7.
After reading the delay correction amount D2, step S8 is executed to add the second delay correction amount D2 to the basic delay amount Db obtained in step S2 to determine the final delay amount De, and in step S9. The second coefficient value K2 is set as the weighted average coefficient K.

The large that case, together with the first delay correction amount D1 is set to a value smaller than the second delay correction amount D2, the first coefficient value K1 is than the second coefficient value K2
It is set to deal of value.

Therefore, when the operating region shifts from the Lb region where the target air-fuel ratio is 22.0 to the λ1 region where the target air-fuel ratio is 14.7, as shown by the arrow x in FIG. 3,
As shown by the arrow y, the final delay amount De is set to a smaller value than when the operating region shifts from the λ1 region to the Lb region.
The weighted average coefficient K while being so that is set to a large value.

Next, the ECU 30 executes step S10 to determine whether or not the delay time corresponding to the final delay amount De has elapsed, and if YES is determined, step S1
Go to 1 and set the target air-fuel ratio A / F according to the following relational expression.
The weighted average processing is performed by reflecting the previous value in (o).

A / F (o) = A / F (o) (i) · K + A / F (o) (i−1) · (1-K) ... Here, for example, the transition from the Lb region to the λ1 region At this time, the current value A / F (o) of the target air-fuel ratio A / F (o)
1i is set as (i), and the first coefficient value K1 is used as the weighted average coefficient K.
Further, at the time of transition from the λ1 region to the Lb region, 22.0 is set as the current value A / F (o) (i) of the target air-fuel ratio A / F (o), and the weighted average coefficient K is set. The second coefficient value K2 is used. Therefore, when shifting from the Lb region to the λ1 region, the target air-fuel ratio A / F (o) changes faster than when shifting from the λ1 region to the Lb region.

Next, the operation of the embodiment will be described.

Assuming that the operating region changes from the Lb region to the λ1 region as shown by the arrow x in FIG. 3, after the delay time T1 corresponding to the final delay amount De has elapsed as shown in FIG. The target air-fuel ratio A / F (o) gradually changes to the rich side as shown by the solid line. In that case,
The process for changing the target air-fuel ratio A / F (o) is started early, and the changing speed is increased. As a result, the target air-fuel ratio A can be accurately matched with the measured air-fuel ratio A / F (s) obtained from the output of the linear O ₂ sensor 13 shown by the broken line in the figure.
/ F (o) will change, and accordingly, the actual air-fuel ratio A / F (r) will also change corresponding to the measured air-fuel ratio A / F (s). Almost no deviation of the fuel ratio occurs.

On the other hand, if the operating region changes from the λ1 region to the Lb region as indicated by the arrow y in FIG. 3, the delay time T2 corresponding to the final delay amount De as shown in FIG.
After the passage of, the target air-fuel ratio A / F (o) gradually changes to the lean side as shown by the solid line. In that case, the process of changing the target air-fuel ratio A / F (o) is started relatively later than the time of transition from the Lb region to the λ1 region, and the changing speed becomes slower. As a result, the target air-fuel ratio A / F (o) changes with high accuracy in response to the measured air-fuel ratio A / F (s) obtained from the output of the linear O ₂ sensor 13 indicated by the broken line in the figure. Along with this, the actual air-fuel ratio A / F (r) also changes corresponding to the measured air-fuel ratio A / F (s), and even in this case, there is almost no difference in air-fuel ratio compared to the conventional case. .

As described above, good air-fuel ratio control accuracy can be obtained both during the transition from the Lb region to the λ1 region and during the transition from the λ1 region to the Lb region.

[0046]

As described above, according to the present invention, the linear O
_{2 When} changing the target air-fuel ratio during feedback control of the air-fuel ratio using a linear air-fuel ratio sensor such as a sensor,
While the target air-fuel ratio is gradually changed, the changing speed will be faster when changing the target air-fuel ratio from the lean side to the rich side than when changing from the rich side to the lean side. Since the target air-fuel ratio substantially matches the output characteristics of the linear air-fuel ratio sensor, deviation of the air-fuel ratio due to feedback control is prevented, and good air-fuel ratio control performance can be obtained.

When the target air-fuel ratio is changed from the lean side to the rich side as in the embodiment, the time when the target air-fuel ratio is changed to a new target air-fuel ratio is longer than that when the target side is changed from the rich side to the lean side. By making it shorter, the target air-fuel ratio will more accurately correspond to the output characteristics of the linear air-fuel ratio sensor, the deviation of the air-fuel ratio due to feedback control will be prevented more reliably, and better air-fuel ratio control performance will be obtained. Will be done.

[Brief description of drawings]

FIG. 1 is a control system diagram of an engine.

FIG. 2 is an explanatory diagram of a map showing an opening / closing area of a shutter valve.

FIG. 3 is an explanatory diagram of a map showing an air-fuel ratio control region.

FIG. 4 is a flowchart showing a process of changing a target air-fuel ratio when shifting to a zone.

FIG. 5 is an explanatory diagram of a map of a basic delay amount using the engine speed and the throttle opening as parameters.

FIG. 6 is a time chart diagram showing a relationship between a target air-fuel ratio and a measured air-fuel ratio obtained from a linear O ₂ sensor at the time of transition from the Lb region to the λ1 region according to the embodiment.

FIG. 7 is a time chart diagram showing a relationship between a target air-fuel ratio and a measured air-fuel ratio obtained from a linear O ₂ sensor at the time of transition from the λ1 region to the Lb region according to the embodiment.

FIG. 8 is a characteristic diagram showing a correspondence relationship between a residual oxygen concentration and an air-fuel ratio by a linear O ₂ sensor.

FIG. 9 is a time chart diagram showing a relationship between a target air-fuel ratio and a measured air-fuel ratio obtained from a linear O ₂ sensor, which shows a problem that occurs when the conventional Lb region shifts to a λ1 region.

FIG. 10 is a time chart diagram showing a relationship between a target air-fuel ratio and a measured air-fuel ratio obtained from a linear O ₂ sensor, which shows a problem that occurs when shifting from the λ1 region to the Lb region in the related art.

[Explanation of symbols]

1 Engine 11 Fuel Injection Valve 13 Linear O ₂ Sensor 30 ECU 32 Throttle Opening Sensor 33 Rotation Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Takagi 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) Reference JP-A-103033 (JP, A) JP-A-62 -38843 (JP, A) JP 62-103437 (JP, A) JP 59-226252 (JP, A) JP 62-189336 (JP, A) JP 6-101541 (JP, A) ) JP 5-133260 (JP, A) JP 5-306641 (JP, A) JP 4-81539 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 41/00-45/00

Claims (3)

(57) [Claims] 1. A linear air-fuel ratio sensor that produces an output that is substantially proportional to the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber is installed in the exhaust system, and the linear air-fuel ratio is realized so that a plurality of target air-fuel ratios are realized. An air-fuel ratio control device for an engine configured to perform feedback control of the air-fuel ratio based on the output of a fuel ratio sensor, wherein the target air-fuel ratio is gradually changed and the target air-fuel ratio is leaned when the target air-fuel ratio is changed. When changing from the rich side to the rich side, the target air-fuel ratio changing means for increasing the changing speed is provided as compared with the case of changing from the rich side to the lean side , and the set value of the target air-fuel ratio is set.
A weighted average processing means for reflecting the previous value and performing a weighted average is installed.
The target air-fuel ratio changing means is
By changing the weighted average coefficient used for averaging,
An air-fuel ratio control device for an engine, which is configured to change a changing speed of a fuel ratio. 2. The air-fuel ratio of the air-fuel mixture supplied to the combustion chamber is approximately
Exhaust system with a linear air-fuel ratio sensor that produces a proportional output
Installed to ensure that multiple target air-fuel ratios are achieved.
Based on the output of the linear air-fuel ratio sensor
Feedback control of the engine
The control device is configured to change the target air-fuel ratio when the target air-fuel ratio is changed.
And gradually change the target air-fuel ratio from the lean side.
When changing to the rich side, change from the rich side to the lean side
Change the target air-fuel ratio
There is a means for changing the target air-fuel ratio
And the target air-fuel ratio from the lean side.
When changing to the rich side, change from the rich side to the lean side
Delay time correction to shorten the above delay time compared to
Air-fuel ratio control system characteristics and to Rue engine that is the means are al provided. 3. The air-fuel ratio of the air-fuel mixture supplied to the combustion chamber is approximately
Exhaust system with a linear air-fuel ratio sensor that produces a proportional output
Installed to ensure that multiple target air-fuel ratios are achieved.
Based on the output of the linear air-fuel ratio sensor
Feedback control of the engine
The control device is configured to change the target air-fuel ratio when the target air-fuel ratio is changed.
And gradually change the target air-fuel ratio from the lean side.
When changing to the rich side, change from the rich side to the lean side
Change the target air-fuel ratio
There is an additional means, and the set value of the target air-fuel ratio
A weighted average processing means for reflecting the previous value and performing a weighted average is installed.
The target air-fuel ratio changing means is
By changing the weighted average coefficient used for averaging,
It is configured to change the speed of changing the fuel ratio.
In addition, delay means for delaying the change time of the target air-fuel ratio, and delay time for shortening the delay time when changing the target air-fuel ratio from the lean side to the rich side compared to changing from the rich side to the lean side. air-fuel ratio control system characteristics and to Rue engine that a correction unit is provided.