JPS5848754A - Air-fuel ratio control apparatus for internal- combustion engine - Google Patents

Abstract

PURPOSE:To improve an operability upon switching by a method wherein a hysteresis zone, in which a torque is changed continuously in case the control mode of the air-fuel ratio is switched from the feedback control mode for the logical air-fuel ratio to the lean control mode, is provided. CONSTITUTION:The control circuit, operating and controlling the valve opening time of a fuel injection valve based on the detecting values of an airflow meter and a revolving number sensor, sets a lean flag to one (1) in a step 52 in case a standard injection time Tp is smaller than a predetermined value alpha0 in the step 51, thereafter, the value of the feedback control is operated in the step 53. When a load is increased and Tp>alpha0 in step 51 as well as the lean flag = 1 in step 54 are decided, the lean flag is set in one (1) while Tp<=alpha2 in the step 58, but the lean flag becomes zero (0) in the step 57 when Tp>alpha2. When the load is decreased and Tp becomes Tp<=alpha1, respective lean flags are set in one (1) and a lean operation is effected in the step 59.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to an air-fuel ratio control device for an internal combustion engine that employs a partial lean system for combustion.

A three-way catalyst and a zero. A method is used in which the three components in the exhaust gas, Co%HC and NOx, are simultaneously subjected to an oxidation and ring reaction using a gas cleaner to purify the exhaust gas.

In order to simultaneously work on the three components in the exhaust gas at a high purification rate, the engine must always be operated near the stoichiometric air-fuel ratio. For this purpose, the output signal of the
＝Shiru.

By the way, when the foot check control is performed in the entire operating range of the engine, there will be a range where fuel efficiency deteriorates. Therefore, in the light load region, the air-fuel ratio is shifted to the lean 1 law, the foot control in the normal region is stopped, and open loop control is performed. For example, the change in intake pipe negative pressure (or equivalent output), specifically, the basic injection time that is approximately proportional to the intake pipe negative pressure, is approximately proportional to the basic injection time Tp in a smaller region than the value of . The air-fuel ratio is directly controlled by feedback control in the range where the set value is larger (=high load), and the range where the set value is smaller (=high load).
= @Load) was being operated under lean control.

However, depending on the switching conditions between Lean MN and Fitoback control, the engine condition becomes extremely unstable and the drivability of the P1 vehicle deteriorates. For example, when switching between lean control and feedback control, 1. big toru,
If the switch is made while there is a difference in the pitch, a shock will be generated in the vehicle each time the switch is made, resulting in poor drivability.

The purpose of the present invention is to (lean 1 in partial lean system)
It is an object of the present invention to provide an internal air-fuel ratio control device that improves the four-turn performance when switching between IIII# and feedpack control and eliminates the above-described drawbacks of the conventional art.

In order to achieve the above object, the present invention provides hysteresis to the load condition when switching between lean control and feed parameter control. , which improves drivability by performing switching smoothly.

That is, as shown in Fig. 1, the basic fuel injection pulse width tep
(= K - A However, 'B constant, Qv and intake air density 5%.

Hysteresis operation is performed in the switching range between lean control and feed batter control (engine speed). When the engine condition changes from light load to high load, tep reaches the set value α-; at the 9-point point, switch from 9-on control to feedback control, and when the engine condition changes from high load to smooth load, 1 for·? When the general fixed value is reached, the control switches from 1 feedback control to 1 feedback control with hysteresis. By providing hysteresis to the switching conditions in this way, the t
el) A high level of power output is obtained. for example,! pmaro α,
At point ゛, switch from lean control to feedback control in line 5', and! , the torque changes from the - torque range to -, but if the torque is too large in -, it can pass through the -7-) range. In contrast, conventionally! Since there is no torsion region in the . FIG. 6 is a diagram schematically showing the structure of an example of the beak of No. Bg Hiromoto.

In the 3rd E, l is the engine, 2 air cleaners, 3
is the intake pipe, 4 is the suittle pulp, 5 is the injector,
6 is a hold on the exhaust, 7 is a flower air pipe, 8 is a potentiometer-type intake air amount sensor built in the air 70-meter that detects the intake air amount, 9 is an intake temperature sensor that detects the internal air temperature,
! o is a water temperature sensor that detects the engine cooling water temperature, 11 is a rotation speed sensor that outputs a nine-frequency pulse signal according to the rotation speed of the tarrank shaft of the engine 1, 12 is a 0° senna, 13 is a three-way catalyst device, and 2o is a It is a control device.

The air passes through the air cleaner 2 and is taken into the intake pipe 3 by the negative pressure inside the intake pipe 3. The amount of intake air is controlled by the throttle valve 4, and a predetermined amount is injected from the injector 5. The mixture is mixed and sent to the combustion engine of the engine. The combusted exhaust gas is purified by the exhaust gas provided in the exhaust pipe 7. Injector 6
The amount of fuel injected is determined by controlling nine solenoid valves (not shown) provided in the injector by means of a control circuit 2o. The information for performing this control includes air intake rate sensor 8, intake temperature sensor 9, water temperature sensor +1, rotation mode sensor 11, and 0. These are the output signals of each sensor of the sensor 1a. Although the control circuit 2o can be constructed as a destarite circuit, it is advantageous to use a microcombination circuit in view of the advantage of being able to perform other processes besides air-fuel ratio control.

The fourth diagram is an IPM boot diagram when a microcomputer is used in the control circuit 20.

The control circuit zO is connected to a central processing unit (CPU) 100 via a path 1sO to a rotation number counter 101 and an interrupt control unit 1.
02, Digital input port) 101.7 tw/, Input port 104, Timer, -105, RAM (Tsundam Access Memory) tOS and ROM (Lead-on')
(memory) The toy's human connection and memory section are connected, and each of the counter 108 and the power amplification section 10G are also connected. For each circuit value, the required voltage is supplied from the power supply circuit 110 to the zero revolution counter 101.
The upper control unit 102 counts the number of pulses of the rotation speed sensor 11 which outputs the number of engine revolutions, and outputs an interrupt command signal to the interrupt control unit 102 in synchronization with the engine rotation. Upon receiving the command signal, it outputs an interrupt signal to the CPU 100 via the path 150. That is, the engine speed is measured once per engine revolution, and the measurement is completed.

At the same time, an interrupt command signal is supplied to the interrupt control unit 102, and in response to this, the interrupt control unit j02 generates an interrupt signal,
The CPt7100 is caused to execute an interrupt processing routine for calculating the fuel injection lid. A digital input capo) 103 sends digital signals such as a starter signal from the starter switch 14 that turns on and off the operation of star # (not shown) to the CPU.
100 (two transmissions), and the analog/four input converter 104 is configured with an analog multiplexer to zero converter, and includes an intake air amount sensor 8, an intake air temperature sensor 9, and a cooling water temperature sensor 1.
0.0. - It has a function of converting each signal from 1.2 to 1.2 and sequentially reading it into CPσ100. R
OM107 is a read-only memory that stores programs and various constant values. The valve opening time of the injector 5 is calculated by crtytoo based on the various input outputs shown in the figure, and has a function as a down counter. That is, it converts a digital signal representing the fuel injection amount into a pulse signal with a pulse time giving the actual valve opening time of the injector. Power amplification-1
0 has a function of driving the injector based on the output signal of the counter 1011. Note that the timer 10S measures the elapsed time and outputs cptrto.

The power is supplied to the power supply circuit 110 via the switch 15 and the battery 16).
It is a chart. In the example shown here, the rounding feedback control area for performing learning control is also provided at the lower end of the lean area (the smallest area of ?).

First, in step s1, it is determined whether or not it is in the feedback region by comparing the basic fuel injection pulse width Tp at that time with the fuel 1 & urine injection pulse width setting value. If it is ip, a lean flag is set in step 52, and an air-fuel ratio control calculation for feedback control is executed in step 53. On the other hand, if "p>%" in step 51, it is checked in step 54 whether or not the lean flag is set, and depending on the result, step 5s or step 5
Process 6 ζ: Move. (If Lean 7 lag is not set)
The process moves to step 55, where the current basic fuel injection pulse width τp is compared with the set point on the lower limit side of the hysteresis characteristic. If the lean flag is not set, there are five reasons: the current engine condition is the characteristics shown in Figure 2.
, it is predicted that the system will be switched to the line control region.

In other words, if "]>>" is 1, there is still an ap feedback region t above the characteristic 'mu town, so as a result of this judgment, the lean flag is reset in step 51, and - for feedback control is set in step 83. Calculation'
, and based on this result, perform the first set of Techno 60. On the other hand, if it is tep, 49 sex 1. Since it means that the vehicle is in the self-control state, in step i8, it is determined that it has entered the lean control region by setting 1, 7, and 2.・The judgment in step 55 is 6 times 9 when switching from feedback control to Y-y control, and conversely, ・Switching from lean control to feedback control is performed in step 55. Determine by 5. The meaning of lean 7 puffer standing in step 54 is that the current control is being carried out on the snow, which means that the set value is 1.
If it is -, it means that the characteristics are still in the condition that should be controlled. Therefore, as a result of this judgment, the lean flag is set again in step 58, and the lean flag is set again in step 5. in! -, the lean value is calculated according to ÷p>, on the other hand, @ $7. This means that you are in a state where you should move from Musi 2, and that means escaping from the lean area.Reset the line 7 U1 in Step 5, and move to Step + SS to get on the characteristic Musi. Performs feed pack control calculations for Step 53
Based on the calculation results obtained by step S9, a correction amount is set in step 6o, and all processing is completed.

In the process 9 shown in Fig. It is also applicable to cases. In this case, the processing company in steps 51 and +12 is not necessary.

As is clear from the above, according to the present invention, by reducing the hysteresis region, it is possible to smoothly switch between one-in control and feedback control, thereby improving drivability during switching. I can do it.

[Brief explanation of the drawing]

Figure 1 is an air-fuel ratio characteristic diagram showing the principle of the present invention. ill
Fig. 3 is a schematic configuration diagram showing an example of the present invention, Fig. 4 is a detailed block diagram of the control circuit 20 according to the invention, and Fig. 5 is a torque characteristic diagram showing the principle of the present invention. 3 is a flowchart showing processing of the present invention. 1...Engine Black...Injector, 1
1...One rotation speed sensor, 12...Ol cent. 13.-Mi former infiltrator device, 20...control circuit, Zoo
- Central processing unit (CI'U), 101 - Number of revolutions counter, 10 - φ interrupt control unit, 1o6...Kum v1107
・-110M 16 B,,, off/re, 109-... Power amplifier, 15 G path. Agent Tatsuyuki Unuma (and 2 others) Procedural amendment January 1980/? Day 1, Display of the case 1982 Patent Application No. 147308 2, Name of the invention Air-fuel ratio control device for internal combustion engine 3, Relationship with the case by the person making the amendment Name of the patent applicant (!120))! Yu Jidosha Kogyo Co., Ltd. (and 1 other person) 4. Agent Drawing 8, Amendment 8 (1) Figure 2 of the drawing is corrected as shown in the attached sheet. that's all

Claims (1)

[Claims] (1) Detects the oxygen concentration in the exhaust gas and feedback controls the air-fuel ratio within the window of the three-way catalyst.
In the air-fuel ratio control device for the inner m+A system, which adopts a partial system in which spin feedback control is stopped in the nine load range and the air-fuel ratio is controlled in a lean state C, torque changes due to the control switching are considered in advance. An air-fuel ratio control device for an internal combustion engine, characterized in that a continuous hysteresis region is provided between the region in which the feedback control is performed and the region in which the forward distribution control is performed.