JPS6312852A - Air-fuel ratio controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the output response or the operationability, by varying the switching speed of actual air-fuel ratio which follows to a target level according to the varying speed of engine load thereby suppressing the variation of air-fuel ratio during abrupt acceleration. CONSTITUTION:Means (a) for detecting an engine load is provided and a varying speed operating means (b) detects the varying speed of engine load on the basis of an output signal from said means (a). A target setting means (c) for setting a target air-fuel ratio corresponding to the operating condition of engine and selecting a target air-fuel ratio leaner than a theoretical level during at least a portion of steady traveling is provided. A control means (d) controls the supply quantity of intake air or fuel such that the target air-fuel ratio can be achieved, and when the target air-fuel ratio varies, the varying speed of supply quantity is varied corresponding to the varying speed of engine load and an operating means (e) for operating the supply quantity is controlled according to an output signal from said control means (d).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for controlling the air-fuel ratio of an automobile internal combustion engine.

(Prior art) In recent years, demands on automobile engines have become more sophisticated.
There is a tendency for mutually contradictory issues such as reduced exhaust gas, high output4, and low fuel consumption to be achieved at a high level.

Particularly from the viewpoint of fuel efficiency, partial lean control has been attempted in which the air-fuel ratio is switched from the stoichiometric air-fuel ratio to a lean air-fuel ratio in a relatively low load region. Those described in Japanese Patent Application Laid-open No. 59-51147 and Japanese Patent Application Laid-Open No. 59-7741 are known.

These devices calculate engine load and vehicle acceleration based on intake pipe pressure, rate of change in engine speed (or rate of change in vehicle running speed), and change in throttle opening, and calculate the load and acceleration. Based on the calculation results, an attempt is made to improve the fuel efficiency of the engine and achieve fuel savings by selecting a lean (lean) air-fuel ratio in the operating range under predetermined conditions.

(Problems to be Solved by the Invention) However, in such conventional air-fuel ratio control devices, the rate of change (air-fuel ratio switching speed) when switching the air-fuel ratio to follow the target value is not always constant. Therefore, for example, if the operating conditions suddenly change due to sudden acceleration, etc., and the target value changes from a lean air-fuel ratio to the stoichiometric air-fuel ratio, the actual air-fuel ratio may change to follow the target value. There may be a delay. In such a case, the following speed to the target value becomes insufficient, the engine output decreases, and problems such as hesitation (deterioration of acceleration response) occur.

Considering this phenomenon from the perspective of engine operability, if the target value shifts from the lean air-fuel ratio to the stoichiometric air-fuel ratio, the actual air-fuel ratio switching speed will change from the lean air-fuel ratio during normal gentle acceleration. It is advantageous to switch to the stoichiometric air-fuel ratio relatively slowly because the shock during switching can be alleviated. On the other hand, during sudden acceleration, it is more effective to switch the air-fuel ratio from the lean air-fuel ratio to the stoichiometric air-fuel ratio as quickly as possible in order to obtain more output.

However, with the current technology (i.e., conventional devices), the switching speed of the air-fuel ratio in response to changes in the target value is always constant regardless of the acceleration state, so this does not pose a problem when the acceleration is relatively gentle as described above. However, during rapid acceleration, the actual air-fuel ratio switching speed cannot sufficiently follow changes in the actual operating conditions, and the air-fuel ratio remains leaner than necessary, causing problems during acceleration. The lack of output leads to deterioration of acceleration response such as hesitation. If the acceleration response deteriorates, it becomes impossible to obtain a smooth acceleration feeling, and drivability deteriorates significantly.

(Purpose of the Invention) Therefore, the present invention suppresses fluctuations in the air-fuel ratio during sudden acceleration, etc. by changing the switching speed of the actual air-fuel ratio that follows the target value according to the rate of change in engine load, and outputs The purpose is to improve responsiveness and drivability.

(Means for Solving the Problems) In order to achieve the above object, the air-fuel ratio control device for an internal combustion engine according to the present invention has a load detection means a for detecting the load of the engine, as shown in FIG. The rate-of-change calculation means calculates the rate of change in engine load based on the output of the load detection means, sets a target air-fuel ratio according to the operating state of the engine, and maintains the target air-fuel ratio during at least a part of steady running. a target setting means C that selects a leaner side than the stoichiometric air-fuel ratio; and a target setting means C that controls the supply amount of intake air or fuel so that the target air-fuel ratio is achieved, and when the target air-fuel ratio changes, the control speed of the supply It includes a control means d that changes the load according to the rate of change of the load, and an operation means e that operates the amount of intake air or fuel supplied based on a signal from the control means d.

(Operation) In the present invention, the rate of change in load is detected, and the actual switching rate of the air-fuel ratio that follows the target value is appropriately changed in accordance with the rate of change. Therefore, fluctuations in the air-fuel ratio during sudden acceleration, etc. are suppressed, and output responsiveness and engine drivability are improved.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 9 are diagrams showing one embodiment of the present invention, and the present invention is referred to as SP i (Single Point Inj
This is an example in which the present invention is applied to an engine of the 3.

First, the configuration will be explained. In Fig. 2, 1 is an engine, and intake air passes through an air cleaner 2, a throttle chamber 3, and is turned 0N10FF by a heater control signal S□.
After being heated by the PTC heater 4, the fuel is supplied to each cylinder from each branch of the intake manifold 5, and the fuel is injected into a single injector (operating means) provided upstream of the throttle valve 6 based on the injection signal SA. It is injected by 7.

An ignition plug 10 is attached to each cylinder, and a high-voltage pulse PULSE from an ignition coil 12 is supplied to the ignition plug 10 via a distributor 11. The spark plug 10, the distributor 11, and the ignition coil 12 constitute an ignition means 13 that ignites the air-fuel mixture, and the ignition means 13 generates and discharges a high-voltage pulse PULSE based on the ignition signal 5IGN. Then, the air-fuel mixture in the cylinder is ignited by the discharge of the high-pressure pulse PULSE.
It explodes and becomes exhaust gas, which passes through the exhaust pipe 14 and is removed from the muffler 16 by the catalytic converter 15, where harmful components (Co, HC, NOx) in the exhaust gas are purified by a three-way catalyst.

Here, the flow of intake air is controlled by a throttle valve 6 in the throttle chamber 3 which is interlocked with the accelerator pedal, and the throttle valve 6 is almost closed during idling. Air flow during idling is by bypass passage 20
, and based on the opening signal 515C, the ISC valve (I
dle 5peed ControlValve:
An appropriate amount of air is secured by the idle control valve (idle control valve) 21.

Further, a swirl control valve 22 is disposed near the intake port of each cylinder.
2 is connected to a servo diaphragm 24 via a rod 23. A predetermined control negative pressure is guided to the servo diaphragm 24 from a solenoid valve 25, and the solenoid valve 25 converts the negative pressure supplied from the intake manifold 5 to the atmosphere based on a swirl control signal S3CV having a duty value DSCV. By leaking, the control negative pressure introduced into the servo diaphragm 24 is continuously changed. The servo diaphragm 24 responds to the control negative pressure and adjusts the opening degree of the swirl control valve 22 via the rod 23.

The swirl control valve 22, rod 23, servo diaphragm 24, and electromagnetic valve 25 collectively constitute a swirl operating means 26.

The opening degree α of the throttle valve 6 is detected by a throttle sensor 30, and the temperature Tw of the cooling water is detected by a water temperature sensor 31. Further, the engine crank angle Ca is detected by a crank angle sensor 32 built into the distributor 11, and the engine rotation speed N can be determined by counting pulses representing the crank angle Ca. - An oxygen sensor 33 is attached to the exhaust pipe 14,
The oxygen sensor 33 is connected to an air-fuel ratio detection circuit 34. The air-fuel ratio detection circuit 34 supplies a pump current Ip to the oxygen sensor 33, and the oxygen concentration in the exhaust gas is detected over a wide range from rich to lean based on the value of this pump current 1p. The oxygen sensor 33 and the air-fuel ratio detection circuit 34 constitute an air-fuel ratio detection means 35.

The operating position of the transmission is detected by a position sensor 36, and the vehicle speed S VSF is detected by a vehicle speed sensor 37. Further, the operation of the air conditioner is detected by the air conditioner switch 38, and the operation of the power steering is detected by the power steering detection switch 39.
Detected by

Each of the above sensors 30.31.32.34.36.37.3
The signals from 8.39 are input to the control unit 50, and the control unit 50 performs engine combustion control (ignition timing control,
(fuel injection control, etc.).

That is, the control unit 50 has functions as a change rate calculation means, a target setting means, and a control means,
CPU U51. ROM52, RAM53 and I10
It is composed of a boat 54.

The CPU 51 reads necessary external data from the I10 boat 54 according to the program written in the ROM 52, and calculates processing values necessary for engine combustion control while exchanging data with the RAM 53. , process the data as necessary to I10 port 5
Output to 4. The I10 boat 54 is equipped with each of the above sensors 30.
．． Signals from 31, 32, 34, 36, 37, 38, and 39 are input, and the respective signals Stt, 5ION, S+sc, and 5scv SS are input from the I10 port 54.
H is output. The ROM 52 stores calculation programs for the CPU 51, and the RAM 53 stores data used in calculations in the form of a map or the like. In addition, R.A.
A part of M53 is made up of non-volatile memory, and retains its memory contents even after engine 1 is stopped.

Next, the operation will be explained, but first the air flow rate calculation system will be explained.

In this embodiment, when detecting the air flow rate, an air flow meter or the like as in the conventional case is not provided, and the air passing through the injector 7 part 1iQAinj (hereinafter referred to as injector air The system uses a method (hereinafter simply referred to as the α-N system) of calculating the amount (hereinafter simply referred to as the α-N system).

The reason why the amount of air passing through the injector portion Q A f n j is calculated using such an α-N system is as follows.

In other words, according to the conventional sensor described above, (a) there is a large fluctuation in the sensor output due to intake pulsation, which causes fluctuations in the fuel injection amount, which causes torque fluctuations, and (b) there is no transient response in terms of sensor responsiveness. (c) The above sensors are relatively expensive. From this point of view, in this example, the α-N system, which is low cost and has excellent responsiveness and detection accuracy, is adopted. are doing.

In addition, especially for Spi type engines, the α
By adopting the -N system, the accuracy of air-fuel ratio control can be greatly improved.

The following is the air N passing through the injector section by this system.
Calculation of Q A i n j will be explained.

FIG. 3 is a flowchart showing a calculation program for the cylinder air amount Q4cyr. First, P, the previous QA
c y L is stored in memory as an old value QAcy1'. Here, QAcyL is the amount of intake air passing through the cylinder section, and corresponds to the intake air IQa (engine load Tp) in a conventional device (for example, an EGi system engine), as shown in Fig. 8 described later. This becomes basic data when calculating the air amount Q Ain j in the injector section by a program.

Next, in P2, the necessary data, ie, the throttle opening α, the duty D of the opening signal 5ISC to the ISC valve 21 (hereinafter referred to as ISO duty), 3c, and the engine speed N are read.

In P3, a flow passage area (hereinafter referred to as throttle valve flow passage area) Aα in a portion where the throttle valve 6 is mounted is calculated based on the throttle opening degree α. This is determined, for example, by looking up the corresponding value of Aα from the table map shown in FIG. In P4, bypass passage areas A and l are similarly calculated from the table map of FIG. 5 based on the ISO duty disc, and in P, the total passage area A is determined according to the following formula (2).

A=Aα+A8...■ Next, in P6, steady air iQi is calculated. To calculate this, first divide the total flow path area A by the engine speed N, and then calculate A/N.
This is done by looking up the corresponding values of steady air iJQi from a table map as shown in FIG. 6 using this A/N and engine speed N as parameters.

Next, in P7, with A and N as parameters, 2 is looked up as a delay coefficient considering the volume of the intake manifold 5 from the table map shown in FIG. 7, and in P, the cylinder air amount QAcyL is calculated according to the following formula to end the routine.

qAc, L=ctAc,,' x (1- to 2) +Q
o xK2...■ However, QAcyL': The value stored in p, the air amount QAcy obtained in this way is Sp as in this example.
For example, the present invention can be applied directly to an EGi-type engine that injects fuel near the intake boat, instead of the i-type engine.

However, since this embodiment uses the SPi method, it is necessary to calculate the injector air amount Q Ai□, and this calculation is performed using the program shown in FIG.

In this program, first, the intake pipe air change amount ΔCM is determined using Pl+ according to the following equation (2). This 60M means the amount of air for changing the pressure of the air in the throttle chamber 3 during a transition with respect to the cylinder air amount QAcyL.

ΔCM= KM
)/N--00, K is a constant determined according to the volume of the intake manifold 5, and the optimum value is selected according to the model of the engine 1, etc. Next, injector air amount Q A according to the following formula (■) at p+z
Calculate i n j.

Q az nj = Q acyt+ΔCM...
...■ Q A i n j obtained in this way has extremely high responsiveness because it uses the throttle valve opening degree α as one of the information parameters, and is calculated using a table map based on experimental data. Accurately correlates with the actual value and has high detection accuracy (high resolution). Furthermore, since existing sensor information is used and only software support by a microcomputer is required, the cost is low. In particular, it is extremely convenient to apply to a type such as the SPi method in which fuel is injected on the upstream side of the throttle chamber 3.

Next, we will explain the function of this paper.

FIG. 9 is a flowchart showing a program for air-fuel ratio control. This program is executed once at a predetermined time or every predetermined crank angle.

First, in P21, it is determined whether the current operating range is in the lean operating range where the target value is the lean air-fuel ratio. This determination is made based on whether operating conditions such as engine cooling water temperature, vehicle speed, engine speed, and load are within predetermined ranges.

When the operating region is in the lean operating region, the target value TFBYAO of the lean target air-fuel ratio is looked up from the lean map in P2□. On the other hand, when the operating region is not in the lean operating region, PX3 looks up the target value TFBYAO of the stoichiometric air-fuel ratio from the stoichiometric map. That is, p2
．． In step -wPx3, the value of the target air-fuel ratio in the current operating range is adopted as the target value TFBYAO at that time, so for example, if the operating range switches to the lean range, the lean target value is immediately adopted. Therefore, the target value can be selected accurately. Here, there are 5 toichio metric points.
: Abbreviation for equivalence point, λ-1 (hereinafter referred to as stoichi).

Next, use the above P in pza or the target value TFBYAO looked up in PX3 and the current air-fuel ratio value (hereinafter referred to as
The current value) is compared with TFBYA. in this way,
By comparing the target value and the current value, it is determined whether the current air-fuel ratio is larger than the target air-fuel ratio. If it is small, the next P zss P zb step is corrected by increasing, and if it is large, P. , P31
Correction by reduction is performed in step .

When TFBYA<TFBYAO, the current value is smaller than the target value, and it is judged that the acceleration is currently in progress, and if pis increases, the increase DR (DR=func (dQAcyt
/dt)) is calculated. The increase DR is expressed as a function of the rate of change (dQAcy1/dt) of the cylinder air amount QAcyL corresponding to the engine load, and the greater the rate of change, the greater the value of the increase DRO.

Here, the cylinder air amount QAc,L is the above-mentioned 3rd to 8th
This is calculated using the figure and shows an extremely high correlation with the engine load in the SPi method.

In this way, in this step, the increase DR from the current value to the target value is appropriately calculated depending on the degree of acceleration of the engine.

Next, at Pg&, a value M obtained by adding the increase DR to the current value TFBYA (referred to as a current value correction value) is stored in the memory as the corrected actual air-fuel ratio. Furthermore, P2? Then, has the current value correction value M reached the target value TFBYAO? (M≧TFB
YAO) or not.

When M≧TFBYAO, it is determined that the current value correction value M has reached the target value (that is, the air-fuel ratio switching has been completed), and the target value TFBYAO is adopted as the current value TFBYA at P, and the current processing is performed. end.

When M<TFBYAO, it is determined that the current value correction value M has not yet reached the target value (that is, the air-fuel ratio switching has not been completed), and in P29, the current value correction value M is set to the current value TFBYA. Adopt the value.

Therefore, by this step PtS''-P2., the current value TFBYA gradually increases and approaches the target value TFBYAO while changing its following speed according to the change speed of the load.

On the other hand, if TFBYA≧TFBYAO in P24, it is determined that the current value is larger than the target value and deceleration is in progress, and P
,. Decrease amount DL in case of deceleration (DL=func'
(dQacyt/dt)) is calculated.

The decrease DL corresponds to the increase DR in the case of the above increase,
The rate of change (dQAcyL/dt) is the DR described above.
The same is true for . Therefore, here, vi is the amount of decrease D that decreases from the current value to the target value depending on the degree of speed.
L is calculated appropriately.

Next, in P31, the value obtained by subtracting the decrease amount DL from the current value TFBYA is stored in the memory as the current value correction value M.

Furthermore, in pzz, the current value correction value M is the single target price TFBY.
It is determined whether AO has been reached (M≧TFBYAO).

When M<TFBYAO, it is determined that the current value correction value M has reached the target value (that is, the air-fuel ratio switching has been completed), and PZII changes the final current value TFBYA to the target value TFBY.
We will adopt AO and complete this process this winter.

On the other hand, when M≧TFBYAO, it is determined that the current value correction value M has not yet reached the target value (air-fuel ratio switching has not been completed), and the current value correction value M is adopted as the current value TFBYA in P29. .

Therefore, in the steps from pza to P31, the current value TFVB is
YA is gradually decreased and brought closer to the target value TFBYAO while changing the tracking speed according to the rate of change of the engine load.

In this way, in this embodiment, the actual air-fuel ratio switching speed that follows the target value is appropriately corrected by the rate of change in engine load (dQAcyt/dt), which represents the acceleration/deceleration state of the engine. It is possible to prevent lean during acceleration and avoid deterioration of acceleration response such as hesitation.

In addition, in this embodiment, even during acceleration, the switching speed of the actual air-fuel ratio that follows the target value is not uniformly changed, so that during normal, relatively slow acceleration, the switching speed of the actual air-fuel ratio is not uniformly changed. By switching slowly, the shock during switching is minimized. Therefore, according to the present invention, it is possible not only to maintain the same shock reduction as in the past during relatively low acceleration, but also to increase the switching speed depending on the acceleration/deceleration state to avoid engine problems such as hesitation. .

(Effects) According to the present invention, since the switching speed of the actual air-fuel ratio that follows the target value is appropriately changed according to the rate of change in engine load, fluctuations in the air-fuel ratio during sudden acceleration can be suppressed. , output responsiveness and drivability can be improved.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 9 are diagrams showing an embodiment of the present invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a diagram showing an embodiment of the present invention.
The figure is a flowchart showing a calculation program for the cylinder air amount QAcy, Figure 4 is a table map of the throttle valve passage area Aα, Figure 5 is a table map of the bypass passage area API, and Figure 6 is the total flow passage. A table map of steady air Wt, QH with A/N, which is the area A divided by the engine speed N, and the engine speed N as parameters.
The figure shows the injector air ff Q A i n j
FIG. 9 is a flowchart showing a program for calculating the air-fuel ratio. ■...Engine, 7...Injector (operating means), 50...
...Control unit (change rate calculation means, target setting means, control means). Fig. 3 Fig. 4 Seattle level (deg) Fig. 5 ISC table 1-buoy [%] Fig. 6 A [degree] Fig. 7 Air flow path surface level i A (cm”) Fig. 8 figure

Claims (1)

[Scope of Claims] a) load detection means for detecting the load on the engine; b) change rate calculation means for calculating the rate of change in the engine load based on the output of the load detection means; and c) according to the operating state of the engine. d) target setting means for setting a target air-fuel ratio according to the target air-fuel ratio and selecting the target air-fuel ratio to be leaner than the stoichiometric air-fuel ratio during at least a part of steady driving; and d) supplying intake air or fuel to achieve the target air-fuel ratio. control means for controlling the amount of intake air or fuel and changing the control speed of the supply amount according to the rate of change of engine load when the target air-fuel ratio changes; and e) the amount of intake air or fuel to be supplied based on a signal from the control means. An air-fuel ratio control device for an internal combustion engine, comprising: an operating means for operating; and an air-fuel ratio control device for an internal combustion engine.