JPH07166937A - Air fuel ratio control method of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve follow-up of control at the time of varying a load by reloading a learning value of a map adjoining under a specified condition when a control constant stored in a two-dimentional map composed of the load and rotational speed is reloaded by utilizing the controlled result of an air-fuel ratio. CONSTITUTION:A load and rotational speed are detected in a control unit 20 by a load detection means 21 and a rotational speed detection means 22 during operating a vehicle, and count in a range preserved in the map M2 of a control constant preserving means 25 is read out. Additionally, the times of crossing from rich side to lean side by the output of a catalyst downstream side oxygen sensor 13is counted by a rich/lean counting means 24. A map M1 is referred by a control constant calculation means 23 when it is judged the count number N reaches 20, for example, and difference between a feedback corrective quantity X when the count number N is 20, and the learning value adjoining to the range is calculated, and a adjoining leaning value is switched to a corrective quantity X when the absolute value of the difference becomes larger than the specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air ratio control method for an internal combustion engine for controlling the air ratio of a gas engine or the like.

[0002]

2. Description of the Related Art In a conventional three-way catalyst system for a gas engine, when the operating condition (load, rotation speed) of the engine changes, the N ratio is adjusted until the air ratio is controlled to an optimum value.
In order to prevent harmful components such as Ox and CO from being discharged, control constants (for example, sub-feedback correction values) are stored in a map set for each region composed of load and rotation speed, and the operating status is When it changed, the responsiveness of control was enhanced by using the stored control constant.

Further, this control constant is always rewritten to an optimum value by feeding back the result of the air ratio control.

[0004]

Generally, the optimum value of the above-mentioned control constant largely depends on how much the catalyst or the oxygen sensor has deteriorated, but the values are almost the same in the adjacent operating regions.

However, in the case of a gas engine used in a cogeneration system or the like, the gas engine is often operated in a fixed region, and initial adjustment is not performed in all regions. In the case of the gas engine or the like, only the control constants in a specific operating region are updated, and the control constants stored in other regions should not be updated to the optimum values.

At this time, if the gas engine is operated in a region other than the specific region, the optimum control constant is not obtained (is not stored) in that region (region other than the specific region). It takes time for the ratio to be optimally controlled, and the emission temporarily deteriorates.
There is a problem that harmful components such as the above are discharged.

Further, when the gas engine is operated across both of the specific regions and the adjacent regions (regions other than the specific region), the control constants of the two regions are very different. Control becomes extremely unstable,
There is also a problem.

The present invention has been proposed in view of the problems of the prior art as described above, and in the case of operating in an area which is not always used on the map as a result of load variation. Another object of the present invention is to provide an air ratio control method for an internal combustion engine that can improve control speed and stability.

[0009]

According to the air ratio control method for an internal combustion engine of the present invention, a control constant stored in a two-dimensional map composed of a load and a rotational speed is always optimally controlled by using a control result of the air ratio. In an air ratio control method for an internal combustion engine that performs air ratio control by rewriting to a constant, when the internal combustion engine is operated in a certain region of the map for a certain period of time or longer, the control constant of the region (sub feedback correction value) )
And the control constant (learning value) stored in the adjacent area in the map is equal to or more than a predetermined value, the stored control constant (learning value) of the adjacent area is set to the control constant (learning value) of the area. Sub-feedback correction value) is rewritten.

Here, it is preferable that the fixed period is a period in which the output voltage of the sub oxygen sensor installed on the downstream side of the catalyst crosses the control target voltage a certain number of times or more.

[0011]

In the present invention, the follow-up speed of control when the load changes can be increased by rewriting the learned value of the adjacent map. Therefore, the control speed can be improved even if the operation is performed in an area that is not normally used on the map as a result of the load fluctuation.

Further, since the learning values of the adjacent maps can be rewritten, when the operation is performed across a region that is often used and a region that is not normally used on the map, the follow-up speed is increased to control the control. The stability can be improved.

[0013]

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

FIG. 1 shows an example of a control device for implementing the present invention in a gas engine. The intake passage 2 of the gas engine 1 is provided with an engine load detection device 3, a throttle 4, and a fuel / air mixing device 5. A gas supply path 6 for city gas G, which is a fuel, and an air supply path 7 for air A are connected to the mixing device 5. Further, a bypass passage 8 that bypasses the gas supply passage 6 and communicates the gas G with the intake passage 2 is provided, and an air ratio adjusting device 9 is interposed in the bypass passage 8.

On the other hand, a catalyst 11 is provided in the exhaust passage 10, a catalyst upstream oxygen sensor 12 is provided on the upstream side of the catalyst, and a catalyst downstream oxygen sensor 13 is provided on the downstream side. There is. Further, a rotation speed detection device 15 of the engine 1 is provided, and these members 3, 9, 12, 13 and 15 are provided.
Are respectively connected to the control unit 20.

The control unit 20 has a load calculating means 21 to which the engine load detecting device 3 and the rotation speed detecting device 15 are connected, an air ratio correction amount calculating means 22 to which the catalyst upstream oxygen sensor 12 is connected, and a catalyst rear A control constant calculating means 23 to which the oxygen flow sensor 13 and the calculating means 22 are connected, a rich / lean counting means 24 connected to the calculating means, a calculating means 23 and a counting means 24, and a map M1 composed of a load to a rotational speed. , M2, a control constant storing means 25, a bypass gas amount calculating means 26 connected to the calculating means 21 and 22, and an air ratio adjusting means 27 connected to the air ratio adjusting device 9 connected to the calculating means 26. Has been. Although not clearly shown in FIG. 1, in the illustrated embodiment, two types of maps are prepared. The map for storing the sub-feedback correction amount is M1, and the map for storing counts is M2. It is shown.

Next, the control mode will be described.

In FIG. 2, the control unit 20 detects changes in the load and the rotation speed by the load detection means 21 and the rotation speed detection means 22 based on the signals from the load detection device 3 and the rotation speed detection device 15. In step S1), the control constant calculation means 23 reads the count of the area stored in the map M2 of the control constant storage means 25 (step S2). Therefore, as shown in FIG. 4, the output voltage of the catalyst wake oxygen sensor 13 by the rich / lean counting means 24 is as follows.
The number of times the control target value is crossed from the higher voltage side, that is, the rich side to the lower voltage side, that is, the lean side, is step S2.
Counting is started from the count number read in (step S3). In FIG. 4, when the count number reaches a predetermined value, it is considered that the control is stable.

Next, it is determined whether or not the count number N has reached a count number predetermined value a (for example, 20) (step S4). If NO, the process returns to step S3. If YES, the control constant calculation means 23 determines that the feedback correction amount F (when the count value N is 20) is 20 in the map M1 shown in FIG. , The differences between the learning values A to D and E to K adjacent to the area are calculated (step S
5). Then, it is calculated whether or not the absolute value of these differences is larger than a predetermined difference value b (for example, 100) (step S).
6). In this example, | A−X |> 100 | B−X |> 100 | C−X |> 100 | D−X |> 100 | E−X | ≦ 100 | F−X | ≦ 100 | G−X |> 100 | H−X |> 100.

Therefore, in step S7, if the absolute value of the difference is smaller than the predetermined difference value b, the process proceeds to step S8, and if it is larger, the adjacent learning value (in the above example,
A to C, F to H) are rewritten to the correction amount X as in the map M1 of FIG. 6 (step S7), the count is cleared (step S8), and the process returns to step S3. At this time, in step S3, counting is started from zero.

In FIG. 3, the control unit 20 detects a change in the load rotational speed (step S10), and determines whether or not the load has changed to an area corresponding to an adjacent area of the map (step S11). If YES in step S11, that is, if the load changes to the adjacent area,
The count number N is stored in the relevant area (predetermined position or area on the map M2) of the map M2 in the control constant storage means 25, and the correction amount F is stored in the map M1 in the control constant storage means 25.
In the area (predetermined position or area on the map M1) (step S12). If step S11 is NO, that is, if the load changes to an area other than the adjacent areas of the map, the count number N is cleared,
Zero is stored in the relevant position of the map M2 (predetermined position or region on the map M2), and the correction amount F is stored in the relevant region of the map M1 (predetermined position or region on the map M1) (step S13).

[0022]

As described above, according to the present invention, it is possible to improve the control following speed in a load that is not always used.

Further, when the operation is performed across the adjacent areas on the map, in other words, when the load fluctuates, the control speed and stability are improved.

Further, the map rewriting area is expanded,
The speed of map rewriting can be improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an example of a control device for implementing the present invention.

FIG. 2 is a control flowchart of map rewriting.

FIG. 3 is a control flowchart of count storage.

FIG. 4 is a timing chart of the output of the catalyst downstream flow oxygen sensor for explaining the counting mode.

FIG. 5 is a drawing showing a map before rewriting.

FIG. 6 is a diagram showing a map after rewriting.

[Explanation of symbols]

 A ... Air F ... Feedback correction amount G ... City gas M1, M2 ... Map N ... Count number a ... Count number predetermined value b ... Difference predetermined value 1 ... Gas engine 2 ... Intake passage 3 ... Engine load detection device 4 ... Throttle 5 ... Fuel / air mixing device 6 ... Gas supply passage 7 ... Air supply passage 8 ... Bypass passage 9 ... Air ratio adjusting device 10 ... Exhaust passage 11 ... Catalyst 12 ... Catalyst upstream oxygen sensor 13 ... Catalyst downstream oxygen sensor 15 ... Rotation speed detecting device 20 ... Control Unit 21 ... Load calculating means 22 ... Air ratio correction amount calculating means 23 ... Control constant calculating means 24 ... Rich / lean counting means 25 ... Control constant storing means 26 ... Bypass gas amount Calculation means 27: Air ratio adjusting hand Step

Claims (2)

[Claims] 1. An air ratio control of an internal combustion engine for performing air ratio control by constantly rewriting a control constant stored in a two-dimensional map composed of a load and a rotational speed into an optimum control constant by using a control result of the air ratio. In the method, when the internal combustion engine is operated in a certain region of the map for a certain period or longer, the difference between the control constant of the region and the control constant stored in the adjacent region of the map is a predetermined value or more. In this case, the air ratio control method for an internal combustion engine, characterized in that the control constant of the adjacent region is rewritten to the control constant of the region. 2. The air ratio control method for an internal combustion engine according to claim 1, wherein the certain period is a period in which the output voltage of the oxygen sensor installed on the downstream side of the catalyst crosses the control target voltage a certain number of times or more.