JPS59126048A - Air-fuel ratio controlling method for internal- combustion engine for vehicle - Google Patents

Abstract

PURPOSE:To prevent rough idling operation of an engine and generation of irritant odor from catalyst, by stopping feedback control of the air-fuel ratio and correcting the air-fuel ratio to make air-fuel mixture lean when the vehicle is stopped and the engine temperature is higher than the ordinary level. CONSTITUTION:When an engine is in operation, an engine control unit 48 controls the air-fuel ratio to an aimed value by way of feedback control by obtaining a datum injection pulse signal Tp from the amount of intake air detected by an air-flow meter 14 and the engine speed detected from a primary ignition signal Ig and controlling operation of an injector 26 by correcting the signal Tp appropriately according to the output of an O2-sensor 30, etc. Here, if it is detected from the output of a vehicle-speed sensor 44 that the vehicle is at rest and the output of a water-temperature sensor 36 is higher than an ordinary value, feedback control of the air-fuel ratio is stopped. Further, control is executed to make air-fuel mixture lean by reducing the air-fuel ratio correction factor by about 5-10% uniformly, for instance, by reducing the correction factor by 5%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control method for an internal combustion engine for a vehicle, and particularly for use in an automobile engine in which exhaust gas purification measures are taken using an air-fuel ratio sensor and a three-way catalyst. suitable for
The present invention relates to an improvement in an air-fuel ratio control method for a vehicle internal combustion engine that performs air-fuel ratio t feedback control according to the state of the exhaust air-fuel ratio so that the air-fuel ratio becomes a target air-fuel ratio.

In automobile engines, 1% of internal combustion engines are equipped with exhaust gas purification measures using three-way catalysts.

It is necessary to maintain the exhaust air-fuel ratio strictly near the stoichiometric air-fuel ratio, and for this purpose, for example, an air-fuel ratio sensor consisting of an oxygen concentration sensor that detects the rich-lean state of the exhaust air-fuel ratio from the oxygen concentration in the exhaust gas, and a fuel an air-fuel ratio control means consisting of an electronically controlled fuel injection device that controls the air-fuel ratio sound of the air-fuel mixture by controlling the injection fL; , a fuel injection amount of the Hiroko control fuel injection device.

That is, a system in which the air-fuel ratio is feedback-controlled to make the oxygen a degree in the exhaust gas equal to the oxygen concentration when a mixture at a target air-fuel ratio, for example, a stoichiometric air-fuel ratio is combusted, has been put into practical use. ing.

This type of air-fuel ratio control has the advantage that it is possible to obtain good exhaust gas purification performance regardless of changes in engine operating conditions.

However, conventionally, after driving at high speed for a long time under high temperature conditions, the vehicle suddenly stops and is left in an idling state, or when the vehicle is stopped and the accelerator is repeatedly turned on and off. However, the air-fuel ratio shifts to the rich side, which not only causes the engine to idle roughly, but also causes the catalyst to emit an irritating odor.

That is, as shown in FIG.
Under high temperature conditions with sunlight, no wind, or a tailwind,
If you suddenly stop the vehicle after driving at high speed and under high load and leave it idling, the engine cooling water temperature will rise due to the wind and the engine thermostat while driving at high speed.

If the temperature is controlled to be below the normal state upper limit while repeatedly descending, or if you suddenly leave it in idling mode under such conditions as in this case, even if the cooling fan is running, there will be no running air at all. The engine cooling water temperature becomes uncontrollable and becomes abnormally high as shown in FIG. 1(B).

Also, as the temperature in the engine compartment increases, the intake air temperature increases.

In particular, in engines equipped with intake air i-sensing electronically controlled fuel injection systems, the density of the air decreases and the temperature of the oxygen concentration sensor increases, so the control frequency increases and the engine is judged to be rich. cormorant. Therefore, the engine rotational speed, as shown by the number ↓4 in FIG. 1(O), becomes lower and unstable than the normal idle rotation and speed, resulting in a so-called rough idle state. Naturally, at this time, the catalyst temperature is also high.

There is also an irritating odor due to HC generated by the catalyst.

Also, if the vehicle is stopped and the accelerator is turned on and off many times, asynchronous injection is performed many times when the idle switch is turned off, so the air-fuel ratio changes rich and lean repeatedly. In addition, the engine cooling water temperature and catalyst temperature also rise abnormally, and even after returning to the idle state, the air-fuel ratio shifts to rich, resulting in a rough idle and a pungent odor. was there.

The present invention has been made to solve the above-mentioned conventional problems, such as when a vehicle is suddenly stopped and left idling after driving at high speed for a long time under high temperature conditions.

To provide an air-fuel ratio control method for a vehicle internal combustion engine capable of preventing rough idling and catalyst irritating odor from occurring when the accelerator is repeatedly turned on and off while the vehicle is stopped.

The present invention provides an air-fuel ratio control method for a vehicle internal combustion engine in which the air-fuel ratio is feedback-controlled according to the state of the exhaust air-fuel ratio so that the air-fuel ratio becomes a target air-fuel ratio. As shown, when the vehicle is stopped and the engine temperature is higher than normal, the previous feedback control is stopped and the air-fuel ratio is corrected to make the air-fuel ratio leaner. In this way, the purpose of the first part was achieved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electronically controlled fuel injection system that senses the amount of intake air for an automobile engine, in which the air-fuel ratio control method for an internal combustion engine for a vehicle according to the present invention is adopted, will be described in detail below with reference to one drawing.

As shown in FIG. 3, this embodiment includes an air cleaner 12 for taking in atmospheric air, an air flow meter 14 for detecting the flow rate of intake air taken into the intake pipe 13 by the air cleaner 12, and a nuclear air flow meter 14.
built into. and an intake air temperature sensor 16 for detecting the temperature of intake air.

It is arranged on the throttle body 18 and opened and closed in conjunction with an accelerator pedal (not shown) arranged on the driver's seat. A throttle valve 20 for sub-controlling the flow of intake air, a throttle sensor 22 including an idle switch that is turned on when the throttle valve 20 is in a fully closed state, and an intake manifold 24 are provided. An injector 26 for injecting fuel toward the intake boats of each cylinder of the engine 10 and an oxygen concentration sensor (hereinafter referred to as 02 (referred to as a sensor) 30, and an exhaust pipe 32.
a three-way catalytic converter 34 disposed in the middle of the engine 10, a water temperature sensor 36 disposed in the cylinder block of the engine 10 for detecting the engine cooling water temperature, and an engine lO
It has a destroyer shaft (not shown) that rotates in conjunction with the rotation of the crankshaft, and the primary ignition signal Ig? r, and a high-pressure ignition secondary signal generated by the ignition coil 38 in accordance with the ignition primary signal Ig. From rotation speed.

A vehicle speed sensor 44 for detecting the running speed of an automobile equipped with an engine 1O, a battery 46, an intake air amount output from the air flow meter 14, and the ignition primary signal 1.
A basic injection pulse signal Tp having a pulse width corresponding to the basic injection time is generated at every predetermined crank angle according to the engine rotational speed determined from An analog calculation circuit outputs an injector drive pulse signal Ti to the injector 26, and a feedback correction is made to the basic injection pulse signal Tp output from the analog calculation circuit in accordance with the rich-lean state of the air-fuel ratio output from the 02 sensor 30. , previous H
In addition to forming a correction signal Vf i for applying correction etc. according to the output of the C throttle sensor 22, when the engine operating state reaches a predetermined operating state, for example, when the idle switch of the throttle sensor 22 is turned off. teeth,
A hybrid engine control device 48 mounted on a digital arithmetic circuit that immediately generates an asynchronous injection pulse signal Taf.
In the intake air meter sensing type electronically controlled fuel injection system for a four-cylinder automobile engine IO, which is equipped with the above-mentioned engine control device 48, when the automobile is in a stopped state and the engine cooling water temperature is higher than normal. When it is high, stop the front d pitch feedback correction.

In addition, the air-fuel ratio correction coefficient is generally about 5 to 10%.

For example, reduce the air-fuel ratio by 5%? It is designed to convert into lr'J-n.

As shown in detail in FIG. 4, the engine control device 48 includes a frequency dividing circuit 50 for dividing the primary ignition signal Igk inputted from the distributor 40 into a signal for each predetermined crank angle, and A basic injection pulse generation circuit that generates a basic injection pulse signal Tpf with a pulse width corresponding to the basic injection time at every predetermined crank angle according to the output of the circuit 50 and the intake air amount signal input from the front @vinia flow meter 14. 52 and the basic injection pulse signal Tp inputted through the diodes 54, correction of the intake temperature signal output from the intake temperature sensor 16, the engine cooling water temperature signal output from the water temperature sensor 36, and the output from the digital control circuit described later. Multiplication correction circuit 56 for performing correction according to signal Vf
and an OR circuit 58 that outputs the logical sum of the injector drive pulse signal Ti output from the multiplication correction circuit 56 and the asynchronous injection pulse signal Ta output from the digital signal control circuit,
An injector drive transistor 60 is driven by the output of the OR circuit 58 and is used to supply current to the cut hole C injector 26, and is used to perform each product calculation process.

For example, a central processing unit (hereinafter referred to as CPU) 62a consisting of a microprocessor, a timer 62b for generating various time signals, and a timer 62b for making an interrupt in response to the basic injection pulse signal Tp output from the basic injection pulse generation circuit 52. An interrupt control section 62c, a digital input port 2d for taking in the air-fuel ratio signal output from the 02 sensor 30, the output from the throttle sensor 22, the output from the front b-speed sensor 44, etc., and the intake air input from the air flow meter 14. Dragon signal - Analog-digital controller (hereinafter referred to as A/D) for converting the engine cooling water temperature signal etc. input from the water temperature sensor 36 into a digital signal and taking it in.
Random access memory (hereinafter referred to as RAM) 621 for temporarily storing calculation data etc. in the fi2e-CPU 62a (referred to as converter) 621 Read-only memory (referred to as RAM) for storing control programs and various constants, etc.
(hereinafter referred to as ROM) 62 g, target 1d CPU 62a
The asynchronous injection pulse signal Ta
The digital output port 2h for outputting to the OR circuit 58, and the digital correction signal obtained according to the calculation result in the CPU 62a as an analog correction signal v
A digital-to-analog converter (hereinafter referred to as a D/A converter) 621 converts the voltage into f and outputs it to the multiplication correction circuit 56 marked #, and applies the voltage of the battery 46 to each component through the key switch 49. A digital control circuit 62 includes a power supply circuit 62j for supplying voltage, and a power supply circuit 62k for supplying voltage directly applied from the battery 46 to the RAM 62f. In fig.

64 is a pull-up resistor, and 66 is an injector resistor.

The action will be explained below.

The lean correction of the air-fuel ratio in this embodiment is executed according to a routine as shown in FIG. That is, first, in step 101, it is determined based on the output of the vehicle speed sensor 44 whether the vehicle speed is below a predetermined value, for example, 7 Km/hJ9. When the determination result is positive, that is, when it is determined that the vehicle is in a stopped state, the process proceeds to step 102, and the engine cooling water temperature is set to a predetermined value higher than the normal state upper limit according to the output of the water temperature sensor 36. It is determined whether or not the value is greater than or equal to the value. If the determination result is positive, that is, if it is determined that the engine cooling water temperature is higher than normal, the process proceeds to step 103, and the air-fuel ratio feedback correction based on the output of the 02 sensor 30 is stopped. Next, the process proceeds to step 104, and the air-fuel ratio correction coefficient is set to 5%, for example.
decrease so that the fuel injection time is uniformly reduced,
The air-fuel ratio is made lean - and this routine ends.

On the other hand, if the determination result in step 101 or 102 is negative, that is, if it is determined that the 5 normal operating state is present, the process proceeds to step 105, and an air-fuel ratio correction coefficient is calculated based on the output of the 02 sensor 30. , the feedback correction is performed, and this routine ends.

In this example. Changes in the air-fuel ratio and air-fuel ratio correction coefficient when the vehicle is left idling after high-speed, high-load driving under high-temperature conditions are indicated by broken lines B in FIGS. 1(D)-(E).

According to this embodiment, a rich shift in the air-to-axis ratio is prevented, and therefore, rough idle and catalyst irritating odor are prevented from occurring.

In the embodiment described above, the engine temperature was detected from the engine cooling water temperature, but the method for detecting the engine temperature is not limited to this, and for example, the engine temperature may be configured to be detected from the engine oil temperature. As mentioned above, even if the accelerator is turned on and off many times while the vehicle is stopped, a similar situation will occur, and the present invention can also be used to deal with this situation.

In the above embodiment, the present invention was applied to an intake air amount sensing type electronically controlled fuel injection device equipped with a hybrid type engine control device, but the scope of the present invention is not limited to this, and is completely applicable to the present invention. It can be similarly applied to an intake air amount sensing type electronically controlled fuel injection engine equipped with a digitalized engine control device, an intake pipe pressure sensing type electronically controlled fuel injection engine, and even general internal combustion engines. it is obvious.

As explained above, according to the present invention, it is possible to prevent the air-fuel ratio from becoming rich when left idling after driving at high speed and under high load under high temperature conditions, or when the accelerator is repeatedly turned on and off while stopped. .

Rough idle and catalyst odor can be prevented.

Moreover, it has excellent effects such as being able to improve practical fuel efficiency.

[Brief explanation of drawings]

Figure 1 shows the vehicle speed, engine cooling water temperature, engine rotational speed, air-fuel ratio, and air-fuel ratio correction coefficient when left idling after driving at high speed and under high load under high temperature conditions in a conventional example and an embodiment of the present invention. 2 is a flowchart showing a summary of the air-fuel ratio control method for a vehicle internal combustion engine according to the present invention, and FIG. 3 is a diagram showing an example of the relationship in comparison. A plan view including some partial views showing the configuration of an embodiment of an intake air amount sensing type electronically controlled fuel injection device 4 for an automobile engine, and FIG. 4 is an engine control device used in the embodiment. The block diagram, FIG. 5, showing the configuration of
2 is a flowchart showing the main part of a routine for performing lean correction of the air-fuel ratio according to vehicle speed and engine cooling water temperature. lO...engine, 2o...throttle valve. 22... Throttle sensor, 26... Injector, 30... Oxygen concentration center (02 sensor), 34...
・Three-way catalytic converter, 36...Water temperature sensor 40・
...Distributor, 42...Dear shifter, 44...
Vehicle speed sensor 48...engine control device. Agent Takaya Ron (and 1 other person) Figure 1 Figure 2 Figure 5

Claims (1)

[Claims] (1) In an air-fuel ratio control method for a vehicle internal combustion engine, in which the air-fuel ratio is feedback-controlled according to the state of the exhaust air-fuel ratio so that the air-fuel ratio becomes a target air-fuel ratio, the vehicle is in a stopped state, and When the engine temperature is higher than normal, the feedback control is stopped and the air-fuel ratio k
An air-fuel ratio control method for an internal combustion engine for a vehicle, characterized in that the air-fuel ratio is made northward lean by performing IJ-ton correction,