JPS63129140A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To permit a good feeling of acceleration to be obtained even when an engine is in moderate acceleration, by providing a load parameter detecting means while discriminating an increase direction of the detected engine load in no relation to the rate of its change and inhibiting a lean control in the load increasing direction. CONSTITUTION:While an engine is in operation, in a control circuit 20 having a load increase direction discriminating means 11 and a lean control inhibiting means 12, a detected value by a throttle sensor 10 is converted into a value TA by A/D conversion, and this value TA is discriminated for whether or not it increases from the preceding time value TA. When the discrimination is YES, next the increment of a counter, measuring a number of times of continuing an acceleration condition, is executed, and a degree of the counted value C is compared with a predetermined value (x). And in the time of a relation where C>x, a lean control of air-fuel ratio is inhibited by deciding the engine to be placed in an acceleration condition. In this way, the engine, increasing its fuel injection quantity from an arithmetic value for obtaining the preset air-fuel ratio in accordance with an operative condition of load or the like, controls air-fuel ratio to a rich state.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an air-fuel ratio control device for an internal combustion engine.

[Prior art and problems]

Conventionally, for example, in internal combustion engines for automobiles, one method of achieving both improved fuel efficiency and drivability such as acceleration has been to use lean control, which allows the internal combustion engine to operate in a lean burn region with good fuel efficiency during steady driving. When rapid acceleration is required, such as when the change to a high load exceeds a predetermined value, lean control is prohibited and the air-fuel ratio is set to below the stoichiometric air-fuel ratio (rich side) to increase the combustion speed. A method is adopted to ensure drivability.

The switching point for prohibiting execution of the lean control is determined based on the degree of change in load parameters such as the rotational speed of the internal combustion engine, intake air amount, intake pipe pressure, throttle opening, etc.

However, especially in the extremely slow acceleration layer near the boundary between a steady load and a transient load, these lean control prohibition conditions do not apply, and lean control continues, so the acceleration feeling is proportional to the driver's accelerator pedal depression. However, there was a problem of poor drivability.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that is capable of canceling lean control so that a feeling of acceleration corresponding to changes in load parameters can be obtained even during extremely slow acceleration.

[Means for solving problems]

In order to solve the above problems, according to the present invention, as shown in FIG. 1, an air-fuel ratio control circuit 4 that controls the fuel supply means to control the air-fuel ratio to a desired value according to the load condition of the engine.
9, the internal combustion engine is equipped with a load parameter detection means 50, a means 49a for determining the direction of increase in the rate of change of the load regardless of its magnitude, and a means 49b for prohibiting lean control in the direction of increase in load. The air-fuel ratio fIil+ control device of the control a is operated as a slave device.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

FIG. 2 is a schematic configuration diagram of a case in which a fuel injection device (injector) is provided as a fuel supply means in this explanation, and 1 is an engine, 2 is an air cleaner, 3 is an intake pipe, 4 is a throttle valve, and 5 is an injector. , 6 is an exhaust manhold, 7 is an exhaust pipe, 8 is a potentiometer-type intake air amount sensor built into the air flow meter that detects the intake air amount,
9 is an intake air temperature sensor; 10 is a throttle sensor that detects the throttle valve opening as a load parameter; 11 is a means for comparing the currently detected throttle valve opening with the throttle valve opening at the previous detection to determine an increase; 12 is a means for determining an increase; Increase determination means 1
means for prohibiting lean control based on the information from 1; 13 is a rotational speed sensor that outputs a pulse signal with a frequency corresponding to the rotational speed of the crankshaft (not shown) of the engine L; 14;
is the water temperature sensor, 15 is the 02 sensor or lean sensor, 1
6 is a three-way catalyst device, and 20 is a control circuit configured as a microcomputer system.

In its operation, air is introduced into the intake pipe 3 via the air cleaner 2, the amount of intake air is controlled by the throttle valve 4, the air from the throttle valve 4 is mixed with fuel injected by the injector 5, and the air is introduced into the intake pipe 3 through the air cleaner 2. sent to the combustion chamber. The combusted exhaust gas is then purified by a three-way catalyst device 16 provided in the exhaust pipe 7. The injector 5 has a solenoid valve (not shown) controlled by a control circuit 20, and the amount of fuel injected is controlled by operating condition information from a group of sensors. This sensor group includes an intake sensor 8, an intake air temperature sensor 9, a rotational speed sensor 13,
Water temperature sensor 14, O2 sensor (or lean sensor) 15
and throttle sensor 10, and others. The operation of the control circuit 20 will be explained with reference to the flowchart shown in FIG. Note that the routine shown in FIG. 3 is executed at regular intervals. 3
0 is the value detected by the throttle sensor 10.
This represents the step of converting and reading as TA. 31 represents a step of determining whether the throttle opening degree TA read in step 30 has increased from the previous throttle opening degree TAO. If it is determined in step 31 that TA>TAO, the process moves to step 32. 32 is a step of incrementing the counter C and checking whether or not the result overflows. Here, the counter C is a counter that measures the number of consecutive acceleration conditions (TA>TAO). If there is no overflow, the process moves to step 33 and the increment value is put into C.

34 represents a step of determining whether the counter value C is greater than or equal to the predetermined value X. The value of this X is set to an appropriate value so as to prevent erroneous determination of acceleration due to measurement errors in TA, vibrations in measured values, noise, etc. If the counter value C is greater than X in step 34, it is determined that the engine is in an accelerating state, and the process proceeds to step 35, where lean control of the air-fuel ratio is prohibited. For example, when the air-fuel ratio control prohibition flag is set and the fuel injection control routine (controls injection ■ so that the set air-fuel ratio is reached according to the air-fuel ratio signal from the 0□ sensor) is not explained because it is well known, this When the flag is set, the fuel injection amount is increased from a calculated value for obtaining a set air-fuel ratio depending on operating conditions such as load.

As a result, the air-fuel ratio becomes rich. Then, the acceleration feeling is secured by a value equal to or higher than the stoichiometric air-fuel ratio (rich side), and the post-processing in which the current TA is set in the TAO in step 36 is completed.

On the other hand, if the throttle opening TA is equal to the previous throttle opening TAO in step 31, for example when driving at a constant speed on a flat ground, or if TA is smaller than TAO, that is, when decelerating, etc., the engine The determination is "NO" as it is a steady state, and then the process moves to step 37, where the counter C is cleared, and then, in step 38, lean control is executed. For example, if the lean control prohibition flag is reset and this flag is reset in the fuel injection routine, the fuel injection amount is maintained at a calculated value to obtain a lean air-fuel ratio set according to the operating conditions such as load. Ru. As a result, lean control is performed. Step 3
The lean control in step 8 is also executed when the taunter C is less than the predetermined value X in step 34. Similar to step 35, this lean control execution step also proceeds to step 36, and the post-processing in which the current TA is set to TAO ends. Incidentally, if the value of C+1 overflows in step 32, the value of C is held as is and the process moves to steps 34 and 35, and control prohibition is continued.

The fourth time is a schematic timing diagram illustrating the operation of the control circuit 20. When the engine shifts to acceleration at time t1 (c), the value of the counter C is incremented by 1 at a set interval (for example, every 48 m5ec) (b), and when the t2 threshold value X is exceeded, the control shifts from lean to rich control (a). When deceleration begins at t, lean control is immediately restored. When the vehicle shifts to acceleration again at t4, the same operation as described above is repeated, and at t5, when C<x, the control is switched to rich control.

〔Effect of the invention〕

According to the present invention, even when the load is in an increasing direction, it is recognized as an acceleration state, so lean control can be prohibited even in an extremely slow acceleration state, and good drivability can therefore be obtained.

In this example, the change in throttle opening was used as the load parameter closest to the driver's intention, but intake pipe negative pressure, Q/N engine speed, or vehicle speed may also be used, and the above effects can be achieved. It is something to play. In addition, in this example, lean control is prohibited and the air-fuel ratio is changed to the rich side in order to improve drivability, but in addition to the above-mentioned drivability improvement, lean control and stoichiometric air-fuel ratio are also taken into consideration to improve exhaust emissions. It is also possible to control between

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an air-fuel ratio control device of the present invention; FIG. 2 is an engine configuration diagram showing a specific embodiment of the present invention; FIG. 3 is a flowchart diagram of the control circuit shown in FIG. 2; FIG. 4 is a schematic timing diagram showing the operation of the control circuit. 1... Engine, 5... Injector, 10
...Throttle sensor, 20.49..Air-fuel ratio control circuit, 11.49a..Load increase direction determination means, 12.49
b...Lean control prohibition means 50...Load parameter detection means. b○ Fig. 1 49- Air-fuel ratio control circuit 49a-m-Load increase direction determining means 49b---Lean control prohibition means Fig. 3 t1t2 t3t4t5 Time Fig. 4

Claims (1)

[Claims] In an internal combustion engine equipped with an air-fuel ratio control circuit that controls a fuel supply means to control the air-fuel ratio to a desired value according to the load condition of the engine, a load parameter detection means and a means for determining the direction of increase;
An air-fuel ratio control device for an internal combustion engine, comprising means for prohibiting lean control in a direction of increasing load.