JPS6065247A - Air-fuel ratio controlling method in internal- combustion engine - Google Patents

Abstract

PURPOSE:To make an exhaust emission control ratio keep in a ternary catalytic converter so better, by detecting capacity deterioration in an air-fuel ratio sensor, while subtracting a specified compensation value from the desired injection quantity for compensation in time of the capacity deterioration. CONSTITUTION:In the case where air-fuel ratio control takes place with an electronic control circuit 20, a fundamental fuel injection quantity is processed through operation on the basis of a state of operation in an internal-combution engine. And, on the basis of an air-fuel ratio detecting signal out of an air-fuel ratio sensor detecting the air-fuel ratio, the fundamental injection quantity is compensated. In addition, variation time per unit voltage in time of the air-fuel ratio detecting signal being altered from rich to lean is detected, and when the variation time is longer than the setting value at normal time, the fuel injection quantity is compensated into decrement. Thus, the controlling air-fuel ratio is prevented from slipping to the rich side in time of capacity deterioration in the air-fuel ratio sensor so that an exhaust emission control ratio in a ternary catalytic converter is maintainable so favorably.

Description

Detailed Description of the Invention [Technical Field J] The present invention detects the air-fuel ratio based on the exhaust gas components of an internal combustion engine (hereinafter also simply referred to as the engine), and uses this detection signal to detect the AT rut of the air-fuel mixture supplied to the internal combustion engine. This invention relates to an air-fuel ratio control method for an internal combustion engine that uses H Full Old Kesha Watland + 1 Okanishiki L-1 No 1 Par J/7.

[Prior Art] Conventionally, C01l-IC contained in engine exhaust gas
A three-way catalytic converter is used to purify harmful substances of 1NOx, but in order to maintain a good purification rate of this three-way catalytic converter, the air-fuel ratio of the air-fuel mixture supplied to the engine is always kept close to the stoichiometric air-fuel ratio. There is a need. For this purpose, the air-fuel ratio is detected from the oxygen concentration in the exhaust gas, and a high-level signal is output when the air-fuel ratio is rich, which is lower than the stoichiometric air-fuel ratio.
An air-fuel ratio sensor that outputs a low-level signal when the engine is lean, which is greater than the stoichiometric air-fuel ratio, is installed in the exhaust pipe of the engine.

However, when the air-fuel ratio sensor is new and functions perfectly normally, as shown in the waveform diagram of the air-fuel ratio detection signal in Figure 1A, the slope of the solid line waveform a at the boundary where the state changes from rich to lean is Although it is close to vertical, if the air-fuel ratio sensor is used for a long time and the detection element deteriorates due to changes over time, the air-fuel ratio detection signal will change from rich to lean, as shown in the broken line waveform in Figure 1A. In part,
During normal conditions, the transition from comparatively rich to lean starts quickly,
The slope of the broken line waveform in that part also becomes small.

This air-fuel ratio detection signal is waveform-shaped and becomes a signal as shown in FIG. 1B.

In other words, when the air-fuel ratio sensor deteriorates, the air-fuel ratio detection signal changes from the solid line waveform in FIG. The air-fuel ratio controlled based on such an air-fuel ratio detection signal deviates from the target stoichiometric air-fuel ratio to the rich side, making it impossible to control the air-fuel ratio with high precision. decreases, NOx,
This causes an increase in harmful substances in GOll-IC.

[Object of the Invention] Focusing on the above points, the present invention compensates for the deviation of the control air-fuel ratio toward the rich side when the performance of the air-fuel ratio sensor deteriorates, and keeps the air-fuel ratio always close to the stoichiometric air-fuel ratio. An object of the present invention is to provide an air-fuel ratio control method for an internal combustion engine that can maintain a good purification rate of a three-way catalytic converter.

[Configuration of the Invention] As shown in FIG. 2, the configuration of the present invention to achieve the above object is to (Pl) calculate the basic fuel injection amount based on the operating state of the internal combustion engine, and (P2) calculate the exhaust gas of the internal combustion engine. In an air-fuel ratio control method for an internal combustion engine that corrects a basic fuel injection amount based on an air-fuel ratio detection signal of an air-fuel ratio sensor that detects an air-fuel ratio from gas components, (P3) the air-fuel ratio detection signal changes from rich to rich. The internal combustion engine is characterized by detecting the change time per unit voltage when the change occurs, comparing this change time with a set value during normal operation, and correcting the reduction of the fuel injection tA stone if the change time is longer than the set value. The gist of this book is how to control the air-fuel ratio of an engine.

[Example] The present invention will be explained below by giving examples and referring to the drawings.

First, FIG. 3 is a schematic system diagram showing a four-stroke, four-cylinder internal combustion engine and its peripheral equipment to which the method of the present invention is applied.

1 is an engine, 2 is a piston, 3 is a spark plug, 4 is an exhaust manifold, 5 is provided in the exhaust manifold 4,
This is an air-fuel ratio sensor that detects the air-fuel ratio from the residual oxygen concentration in exhaust gas.When the air-fuel ratio is rich, which is lower than the stoichiometric air-fuel ratio, a high level signal is output, and when the air-fuel ratio is lean, which is higher than the stoichiometric air-fuel ratio, a low level signal is output. do. 6 is a fuel injection valve provided for each cylinder and injects fuel; 7 is an intake manifold; 7a is an intake port to which the intake manifold 7 is connected; 7b is an intake valve; 1 is an intake air temperature sensor that detects the temperature of intake air sent to 1; 9 is a water temperature sensor that detects the engine cooling water temperature; 10 is a throttle valve; Throttle position sensor that outputs a signal, 12
1 is a bypass passage, 13 is an idle speed control valve (ISCV) that controls the opening area of the bypass passage 12 and controls the rotation speed, 14 is an air flow meter that measures the amount of intake air, and 15 is an air cleaner that purifies the intake air. It represents.

Further, 16 is an igniter that is equipped with an ignition coil and outputs the high voltage necessary for ignition, and 17 is a distributor that is linked to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 3 of each cylinder. , 18
is installed in the distributor 17 and rotates 24 times per revolution of the distributor 17, that is, two revolutions of the crankshaft.
Reference numeral 19 represents a cylinder discrimination sensor that outputs one pulse signal per revolution of the distributor 17, and 20 represents an electronic control circuit.

Further, reference numeral 21 indicates an air valve that controls the amount of air passing through the bypass passage 21 for bypassing the throttle valve, that is, the fast idle bypass passage 21 when the engine is cold. Note that the air valve 22 operates to open the fast idle bypass passage 21 in order to secure the engine rotational speed necessary for warm-up operation when the engine is cold.

Next, FIG. 4 shows a block diagram of the electronic control circuit 20.

30 inputs and calculates data output from each sensor according to a control program, and also inputs and calculates data output from each sensor, and also inputs and calculates data output from each sensor.
A central processing unit (hereinafter simply referred to as a CPU) performs processing to control the operation of various devices such as the CV13.
31 is a read-only memory (hereinafter simply referred to as ROM) in which data such as the control program and a map for calculating the fuel injection amount is stored; 32 is a read-only memory (hereinafter simply referred to as ROM); 32 is data input to the electronic control circuit 20 and calculations; Random access memory (hereinafter referred to as
33 is a backup random access memory (hereinafter simply referred to as backup RAM) backed up by a battery so as to retain learning value data necessary for subsequent engine operation even if a key switch (not shown) is turned off. 34 is an input port (not shown), a waveform shaping circuit provided as necessary, a multiplexer that selectively outputs the output signal of each sensor to the CPU 30, and an A/D converter that converts an analog signal into a digital signal. , etc., each represents an input unit provided with the input unit.

35 is provided with an output port in addition to an input port (not shown), and a fuel injection valve 6, rscV1 as required.
36 is an input/output unit equipped with a drive circuit etc. for driving the CPU 3 etc. according to the control signal of the CPLI 30;
The path lines connecting each element such as the O1 ROM 31, the input section 34, and the output section 35 and through which each data is sent are shown.

The control of the fuel injection valve 6 by the CPU 30 is executed by outputting to the fuel injection valve 6 a pulse signal that remains at a low level for a time corresponding to the calculated fuel injection amount.

Next, the air-fuel ratio control process executed by the CPU 30 will be explained based on the flowchart of the control program shown in FIG.

First, when the process starts, step 101 is executed,
■Intake amount data Q detected by the aphrometer 14
and the engine rotation speed data N detected by the rotation speed sensor 18 are read into the CPU 30, and the next step 102
Calculate the basic fuel injection amount. And step 103
In step 104, it is determined whether the air-fuel ratio detection signal output from the air-fuel ratio sensor 5 is rich or lean. If rich, the correction amount α is adjusted from the basic fuel injection amount (time) T0 in step 104.
If it is lean, the correction amount α is added to the basic fuel injection amount (time) T0 in step 105.

Subsequently, step 106 is executed to determine whether the performance of the air-fuel ratio sensor 5 has deteriorated based on the time per unit voltage when the air-fuel ratio detection signal changes from rich to lean.

That is, here, the change time T2 per unit voltage Vo < Vo = V1 - V2 when the sixth air-fuel ratio changes from rich to lean is measured, and this change time T2 is the preset standard for normal performance. It is compared with the change time T1, and if the change time T2 is greater than T1, then step 10
7 is executed, and the correction amount β is further subtracted from the fuel injection amount (time) T1 calculated in step 104 or 105. Then, the corrected final fuel injection amount (time) τ is set in the output register in step 10B, and the opening time of the fuel injection valve 6 is controlled in injection control executed at every predetermined timing in another interrupt routine. controlled mother fuel injection is performed at a predetermined timing.

In this way, when the performance of the air-fuel ratio sensor 5 deteriorates, the lean time becomes longer than it actually is, so the control air-fuel ratio shifts to the rich side, but the predetermined correction amount β is subtracted from the fuel injection amount. By correcting this, the air-fuel ratio is prevented from shifting to the rich side and becomes excessively rich, and the air-fuel ratio is always maintained at a good purification rate.] As explained above, the air-fuel ratio control of the present invention According to the method, by detecting performance deterioration of the air-fuel ratio sensor and subtracting a predetermined correction amount from the target injection amount when the performance deteriorates,
It is possible to prevent the control air-fuel ratio from shifting to the rich side, to always control the air-fuel ratio to be close to the stoichiometric air-fuel ratio, and to maintain a good exhaust gas purification rate in the three-way catalytic converter.

[Brief explanation of the drawing]

FIG. 1A is a detection signal waveform diagram of the air-fuel ratio sensor, FIG. 1B is a waveform diagram of the waveform-shaped detection signal of the air-fuel ratio sensor, FIG. 2 is a basic configuration diagram of the present invention, and FIG. 3 is a diagram of the present invention. FIG. 4 is a block diagram of an electronic control circuit, FIG. 5 is a flowchart showing a control program of an embodiment of the method of the present invention, and FIG. 6 is a diagram of an air-fuel ratio sensor. An enlarged waveform diagram of a detection signal is shown. 1... Engine 5... Air-fuel ratio sensor 6... Fuel injection valve 14... Air flow meter 18... Rotation speed sensor 20... Electronic control circuit 30... CPLI Agent Patent attorney Tsutomu Adachi 1 other person Figure 1 (A) (B) 1 Low -J ul----J Figure 2 Figure 5 Figure 6

Claims (1)

[Claims] The basic fuel injection amount is calculated based on the operating state of the internal combustion engine, and the basic fuel injection amount is corrected based on the air-fuel ratio detection signal of an air-fuel ratio sensor that detects the air-fuel ratio from the exhaust gas components of the internal combustion engine. In the air-fuel ratio control method for an internal combustion engine, the change time per unit voltage when the air-fuel ratio detection signal changes from rich to lean is detected, and the second change time is compared with a normal setting value, An air-fuel ratio control method for an internal combustion engine, characterized in that when the change time is longer than a set value, the amount of fuel injection is corrected to decrease.