JPH10266883A - Engine fuel control device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the fuel consumption rate during running of a vehicle and suppress the emission of harmful exhaust components accompanying the fuel consumption rate. A fuel rich correction coefficient and a lean correction coefficient are set for an air-fuel ratio correction coefficient set to maintain a stoichiometric air-fuel ratio for each fuel injection, and switching is performed at a predetermined timing for each fuel injection. [Effect] The fuel consumption rate is reduced by increasing the number of times the lean-side correction coefficient is set more than the number of times the rich-side correction coefficient is set. The nitrogen oxides generated by setting the air-fuel ratio to the lean side are reduced by the rich side fuel while being stored in the redox catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control device for an engine, and more particularly to a control method for an engine for reducing fuel consumption.

[0002]

2. Description of the Related Art The prior art is disclosed in Japanese Patent Application Laid-Open No. 58-48749.
As described above, an air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture in the vicinity of the stoichiometric air-fuel ratio and in the fuel-lean air-fuel ratio region from the oxygen concentration in the exhaust gas, and an air-fuel ratio control unit that controls the air-fuel ratio of the air-fuel mixture It is described that based on the output of the air-fuel ratio sensor, the air-fuel control is feedback-controlled so that the air-fuel ratio of the air-fuel mixture becomes the target air-fuel ratio in the stoichiometric air-fuel ratio and the fuel-lean air-fuel ratio region. I have.

[0003]

In the above prior art, no consideration is given to exhaust harmful components (particularly nitrogen oxides) in the fuel-lean air-fuel ratio range. At this time, the exhaust gas component at this time contains more nitrogen oxides than in the stoichiometric air-fuel ratio control region.

[0004] Therefore, the fuel-lean air-fuel ratio range for reducing fuel consumption is considerably limited.

The present invention has been made in view of such a problem, and an object of the present invention is to reduce the fuel consumption by operating an engine in a fuel-lean air-fuel ratio range and to reduce the amount of exhaust gas components. It is an object of the present invention to provide an engine fuel control device that reduces nitrogen oxides.

[0006]

In order to achieve the above object,
The engine fuel control device according to the present invention is configured such that the engine intake air amount measurement unit, the engine speed detection unit, the unit for obtaining a predetermined crank angle of the engine, and the engine intake air amount measurement unit are measured. From the intake air amount and the rotation speed detected by the rotation speed detection means of the engine,
Means for obtaining a basic amount of fuel to be supplied to the engine, means for detecting the oxygen concentration of exhaust gas discharged from the engine,
Means for obtaining a first fuel amount based on the detected oxygen concentration so as to obtain an air-fuel ratio that targets the basic fuel amount, and a theoretical unit based on the first fuel amount. Means for obtaining a second fuel amount richer than the air-fuel ratio, means for obtaining a third fuel amount leaner than the stoichiometric air-fuel ratio based on the first fuel amount, and the first fuel amount depending on the state of the engine. Means having a region for supplying a fuel amount, a region for switching and supplying a second amount of fuel and a third amount of fuel in accordance with the timing of injecting the fuel, and a region for supplying the predetermined amount of the obtained crank angle. And means for injecting an amount of fuel supplied to the engine in accordance with the timing.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall configuration of an engine and a control device of the engine according to the present embodiment. The engine 100 has a heating element resistance type air flow meter (hereinafter, referred to as H) that measures the amount of air taken into the engine 100 by the heating element resistance.
/ W sensor) 101, a throttle valve 103 for adjusting the flow rate of air taken in by the engine 100, a throttle opening sensor 102 for converting the opening of the throttle valve 103 into an electric signal, and a given electric power. A fuel injection valve 104 is provided to supply fuel to the engine 100 with a target signal, and the engine 100 is provided with an ignition plug 105 for igniting a mixture of fuel and air in a cylinder with a given electric signal and timing. And a crank angle sensor 106 installed on the circumference of the crankshaft of the engine to measure the number of revolutions per unit time. The exhaust pipe of the engine 100 has an oxygen concentration sensor 107 for detecting an oxygen concentration in the exhaust gas and generating an electric signal for feedback control for setting the engine 100 to a fuel injection amount having a target air-fuel ratio. An oxidation-reduction catalyst 108 for oxidizing and reducing the exhaust gas to purify the exhaust gas is provided downstream of the concentration sensor 107, and the H / W sensor 101, the crank angle sensor 106 and the oxygen concentration sensor 107 An engine control device 109 is provided, which processes the target signal based on a predetermined procedure, determines the fuel amount and ignition timing required by the engine 100, and sends an electric signal to an actuator such as the fuel injection valve. I have.

FIG. 2 shows an example of an engine control device according to the present embodiment. The engine control device 10
Reference numeral 9 denotes a driver circuit 201 for inputting signals from sensors installed in various parts of the engine 100 and converting a small signal (TTL level) into a large signal for driving the actuator, and an analog circuit for performing digital arithmetic processing on input / output signals. An input / output circuit 202 for performing digital signal conversion, a microcomputer for performing digital arithmetic processing, or an arithmetic circuit 203 having an arithmetic circuit equivalent thereto, a non-volatile memory 204 for storing constants and programs used for arithmetic processing of the arithmetic circuit 203, Volatile memory 205 for storing variables,
Power supply holding circuit (backup) 206 for holding the contents of the memory of the arithmetic circuit 203 and the volatile memory 205
It is composed of In this embodiment, the input / output circuit 20 is used.
2 and the arithmetic circuit 203 are described separately, but the arithmetic circuit 203 may include an input / output circuit 202 in some cases.
Further, the control device of the engine according to the present embodiment includes an H / W sensor,
Electrical signals of an oxygen concentration sensor, a crank angle sensor, a throttle opening sensor, and a water temperature sensor are input, and drive signals for a fuel injection valve and an ignition plug are output.

FIG. 3 shows the air-fuel ratio (mixing ratio of gasoline and air) of the engine and the unburned gasoline (H
C) 301, nitrogen oxides (NOx) 302, and fuel consumption rate 303 are shown. When the air-fuel ratio is richer than the stoichiometric air-fuel ratio, a large amount of HC is emitted, and when the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio, the amount of emission decreases rapidly. On the other hand, NOx gradually increases as the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio. Further, the point where the fuel consumption rate becomes minimum indicates that the fuel consumption rate is slightly leaner than the stoichiometric air-fuel ratio.

FIG. 4 shows an example of a fuel injection mode according to the present invention. A solid line 401 indicates the fuel injection width actually injected. A dashed line 402 indicates the fuel injection width required to maintain the stoichiometric air-fuel ratio. Therefore, the fuel injection width 403
Is injected with fuel richer than the stoichiometric air-fuel ratio, and the other fuel injection widths are set to the fuel injection width leaner than the stoichiometric air-fuel ratio. A chart 404 is a cylinder counter, which is incremented every fuel injection timing and reset when a predetermined value 405 is reached. At this reset timing, the above-described fuel injection width 403
The fuel injection amount is set.

FIG. 5 shows another example of a fuel injection mode according to the present invention. 4, the timing at which the fuel injection width on the rich side of the stoichiometric air-fuel ratio is set follows the fuel injection pattern table for each fuel injection timing. FIG. 6 shows a region in which the fuel injection mode of the configuration shown in FIGS. 4 and 5 is executed.
An area 601 is an area for performing feedback of the air-fuel ratio based on the output of the oxygen concentration sensor installed in the exhaust pipe. The region 602 is a region (intermittent lean region) in which the fuel injection mode of the configuration shown in FIGS. 4 and 5 is executed. An area 603 is a power area in which fuel injection richer than the stoichiometric air-fuel ratio is performed.

FIG. 7 shows the relationship between the output of the oxygen concentration sensor and the feedback coefficient, and the air-fuel ratio correction coefficient when the fuel injection modes of FIGS. 4 and 5 are performed. A chart 701 is the output of the above-described oxygen concentration sensor, and a chart 702 is the air-fuel ratio correction coefficient calculated from the output of the oxygen concentration sensor. The coefficient 703 is an average value of the air-fuel ratio correction coefficients calculated by a weighted average or a moving average. The coefficient 704 is a coefficient for calculating the fuel injection width on the rich side in FIGS. 4 and 5 calculated from the average value of the air-fuel ratio correction coefficient, and the coefficient 705 is a coefficient for calculating the fuel injection width on the lean side.

FIG. 8 shows a flow chart of the fuel injection of the engine control device according to the present invention. At step 801, the output of the H / W sensor is read. Step 80
In step 2, the engine speed calculated from the signal of the engine crank angle sensor is read. Step 803,
At 804, the engine load and the basic fuel amount are calculated based on the output of the H / W sensor and the engine speed. Step 805
Then, the fuel injection mode determined by the engine speed and the engine load is determined. If it is in the air-fuel ratio feedback area, step 807 is executed in the intermittent lean control area, and step 808 is executed in the power area. Each corrected fuel is set in step 809 and is actually injected into the engine.

FIG. 9 shows a flow chart of the above-mentioned air-fuel ratio feedback. In step 901, the output of the oxygen concentration sensor is read. In step 902, it is determined whether the output of the oxygen concentration sensor is larger than a predetermined value. Steps 903, 904, and 905 are processing in the case where the output of the oxygen concentration sensor is larger than a predetermined value. As shown in the flowchart, the air-fuel ratio correction coefficient αf is subjected to differential correction and integration feedback correction. . Steps 906, 907, and 908 are feedback corrections when the output of the oxygen concentration sensor is smaller than a predetermined value.

FIG. 10 is a flowchart for calculating the air-fuel ratio correction coefficient used in the intermittent lean region. In step 1001, the air-fuel ratio correction coefficient α is read. Step 10
In 02, the average value αf of the above-described air-fuel ratio correction coefficient αf is calculated. In steps 1003 and 1004, the engine speed and the basic fuel amount are read. In steps 1005 and 1006, the lean fuel gain Kl and the rich fuel gain Kr are searched from the above-described map of the engine speed and the basic fuel amount. In steps 1007 and 1008, a lean fuel correction coefficient αl and a rich fuel correction coefficient αr are calculated from the aforementioned lean, rich fuel gain and air-fuel ratio correction coefficient average value αf.

FIG. 11 is an example of a flowchart for correcting the intermittent lean fuel. This flowchart is executed for every crank angle synchronization of the engine, especially for each fuel injection amount set. In step 1101, the cylinder counter is incremented. In step 1102, it is determined whether the value of the cylinder counter is equal to or greater than a predetermined value. If the cylinder counter is equal to or greater than the predetermined value, the rich-side air-fuel ratio correction coefficient αr is determined in step 1103;
In step 4, the lean air-fuel ratio correction coefficient αl is read in step 1
At 105, the cylinder counter is cleared (reset).
In step 1106, the basic fuel amount is corrected with the read air-fuel ratio correction coefficient, and intermittent lean control is performed.

FIG. 12 is another example of the intermittent lean fuel correction flowchart. The switching between the rich fuel side correction coefficient and the lean side fuel correction coefficient in the example of FIG. 11 is determined by reading the intermittent fuel injection pattern table in step 1201.

Although the embodiment of the present invention has been described above, the fuel control apparatus for an engine according to the present invention configured as described above injects fuel on the lean side with respect to the stoichiometric air-fuel ratio to reduce fuel consumption. To reduce. The nitrogen oxides generated at this time are in a state where they are temporarily stored in an oxidation-reduction catalyst installed downstream of the exhaust pipe. To reduce emissions to the public.

[0020]

According to the present embodiment, the fuel consumption can be reduced without increasing harmful exhaust components (particularly nitrogen oxides) when the vehicle is running. In addition, since the control region, which is a feature of the present invention, is divided depending on the state of the engine, the operability is not impaired.

[Brief description of the drawings]

FIG. 1 is an example of a configuration diagram of an engine and an engine control device according to an embodiment of the present invention.

FIG. 2 is an example of a conceptual configuration diagram of an engine control device of the present invention.

FIG. 3 is an example of a correlation diagram of an air-fuel ratio, an exhaust gas component, and a fuel consumption rate of the engine of the present invention.

FIG. 4 shows an example of a fuel injection mode according to the present invention.

FIG. 5 shows another example of the fuel injection mode of the present invention.

FIG. 6 is an example of a region in which the fuel injection mode of the present invention is executed.

FIG. 7 is a correlation diagram of an oxygen concentration sensor output, a feedback coefficient, and an air-fuel ratio correction coefficient according to the present invention.

FIG. 8 is an example of a fuel injection flowchart of the control device of the present invention.

FIG. 9 is an example of an air-fuel ratio feedback flowchart of the control device of the present invention.

FIG. 10 is an example of a flowchart for calculating an air-fuel ratio correction coefficient in an intermittent lean region of the control device of the present invention.

FIG. 11 is an example of a flowchart of intermittent lean fuel correction of the control device of the present invention.

FIG. 12 is another example of a flowchart of intermittent lean fuel correction of the control device of the present invention.

[Explanation of symbols]

100 ... engine, 101 ... heating element resistance type air flow meter,
104: fuel injection valve, 106: crank angle sensor, 1
07: oxygen concentration sensor, 109: engine control device.

Claims (5)

[Claims] 1. An engine intake air amount measuring means, an engine speed detecting means, a means for obtaining a predetermined crank angle of the engine, an intake air amount measured by the engine intake air amount measuring means, Means for obtaining a basic amount of fuel to be supplied to the engine from the number of revolutions detected by the number of revolutions of the engine; means for detecting the oxygen concentration of exhaust gas discharged from the engine; and the detected oxygen concentration. Means for correcting the basic fuel amount to obtain a target air-fuel ratio based on the first fuel amount, and a second fuel concentration based on the first fuel amount. Means for obtaining a third fuel amount based on the first fuel amount; means for obtaining a third fuel amount leaner than the stoichiometric air-fuel ratio based on the first fuel amount; and a region for supplying the first fuel amount according to the state of the engine. And the second fuel amount and the third fuel Means for switching and supplying the fuel according to the injection timing, and means for injecting into the engine the amount of fuel supplied according to the area and the timing at the obtained predetermined crank angle, A fuel control device for an engine, comprising: 2. The engine fuel control device according to claim 1, wherein said intake air amount measuring means of said engine is a heating resistor type air flow meter. 3. An air-fuel ratio in the region where the second fuel amount and the third fuel amount are switched and supplied, the average air-fuel ratio in the region is leaner than the stoichiometric air-fuel ratio.
An engine fuel control device according to claim 1. 4. The fuel control system for an engine according to claim 1, wherein the timing of switching between the second fuel amount and the third fuel amount is switched every predetermined number of injections. 5. The engine fuel control device according to claim 1, wherein the timing for switching between the second fuel amount and the third fuel amount is switched according to a predetermined pattern.