JPS58126440A - Starting method of air-fuel ratio feedback in electronically controlled engine - Google Patents

Abstract

PURPOSE:To improve drivability, by setting an initial value of warming increase with engine temperature, reducing the value at a prescribed rate for every engine speed and starting feedback control of air-fuel ratio when the value is decreased below a preset value. CONSTITUTION:A CPU56 of an electronic control unit fetches water temperature at starting from a sensor 30 to obtain an initial value of increase from a map and store the value in a RAM56 as a warming increase value. Then interruption by a signal of every one turn of a crank angle sensor 32 subtracts a constant A in accordance with a load condition from a stored warming increase value FWL to compare the subtracted value FWLd with an air-fuel ratio feedback start value FWLf, if FWLd <=FWLf, air-fuel ratio feedback control on the basis of an output of an O2 sensor 31 is started. Accordingly, drivability is improved, and worsening of emission, caused at disorder of air-fuel ratio due to the O2 sensor under an insufficient condition of warming and at overrich due to a delay start of feedback control, can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides O! The present invention relates to a method for starting air-fuel ratio feedback of an electronically controlled engine for optimally starting air-fuel ratio feedback of the electronically controlled engine using a sensor.

Air-fuel ratio feedback control in electronically controlled engines is used to optimize the exhaust gas purification rate of the three-way catalyst by controlling it within an extremely narrow range around the stoichiometric air-fuel ratio where the conversion efficiency of the catalyst is highest. It is.

Such nitrogen-fuel ratio feedback control is usually not used during warm-up or the like in order to avoid errors.

Conventionally, the starting point of air-fuel ratio feedback is 0!
When the output of Senna exceeds the value of O! It was assumed that the resistance value of the sensor was below the specified value.

However, in this conventional method, 0! Feedback control may be started in a state where the sensor cannot fully function and the temperature level has not risen sufficiently. In such a case, the air-fuel ratio control characteristics become more disturbed than before the start of feedback, or an air-fuel mixture that is too rich than the engine's required air-fuel ratio is supplied, leading to an increase in hydrocarbons, etc. This led to deterioration in emissions and deterioration in drivability due to early or slow application of feedback control.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for starting full fuel ratio feedback for an electronically controlled engine that eliminates the above-described conventional drawbacks by optimally starting air fuel ratio feedback depending on the engine condition.

According to the present invention, air-fuel ratio feedback control is started when the warm-up increase value becomes equal to or less than a predetermined value. This warm-up increase is determined by setting an initial value based on the engine temperature at the time of startup, then subtracting a predetermined amount from this initial value at each engine rotation, and setting the point at which feedback control is started when the subtracted value reaches the set value. shall be.

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a system diagram of an electronically controlled fuel injection engine to which the present invention is applicable. The air sucked into air cleaner 1 is passed through air flow meter 2, throttle valve 3, surge tank 4, and intake y.
l? - It is sent to the combustion engine body 7 via the intake passage 12 including the intake valve 6 and the intake valve 6. The throttle valve 6 is linked to an accelerator pedal 13 in the driver's cab. The combustion chamber 8 includes a cylinder head 9, a cylinder block 10. and a piston 11, and the exhaust gas produced by the combustion of the air-fuel mixture is discharged to the atmosphere through an exhaust valve 15, an exhaust manifold 17, and an exhaust pipe 18. The bypass passage 21 connects the upstream of the throttle valve 3 and the surge tank 4, and the bypass flow it'it\IJ valves 22 control the flow cross-sectional area of the bypass passage 21, ff1lJ, to keep the engine speed constant during idle link. to be maintained. An exhaust gas recirculation (EGR) passage 23 that guides exhaust gas to the intake system in order to suppress the generation of nitrogen oxides connects the exhaust manifold 17 and the surge tank 4, and has an on-off valve type exhaust gas recirculation (EGR) passage.
If EGR>tv+, both valves 24 open and close the EGR passage 23 in response to the short pulse. The intake air temperature sensor 28 is provided in the air 70 meter 2 to detect the air intake air temperature, and the throttle position sensor 29 detects the opening degree of the throttle valve 3.

The water temperature sensor 30 is attached to the cylinder block 10 and calculates the cooling water temperature, that is, the engine temperature, and detects the failure system temperature sensor/
Shusho's air-fuel ratio sensor 31 is attached to the collecting part of the exhaust manifold 17 and detects the oxygen concentration in the collecting part, and the crank angle sensor 32 is connected to the crankshaft (not shown) of the engine body 7. The crank angle of the crankshaft is detected from the 340 rotations of the power distributor 330 shaft, and the vehicle speed sensor 35 detects the rotation speed of the output shaft of the automatic transmission 36. The outputs of these sensors 2, 28, 29, 30, 31, 32, 35 and the voltage of the storage battery 37 are sent to the electronic control unit 40. The fuel injection valve 41 is connected to the valley intake port 5 corresponding to each cylinder.
The pump 42 is provided near the fuel tank 4.
The fuel is sent to the fuel injection valve 41 via the fuel conduit wr 44 from No. 3. The electronic control unit 40 calculates the fuel injection amount using input signals from each sensor as parameters, and sends an electric pulse having a pulse width corresponding to the calculated fuel injection amount to the fuel injection valve 41.

The electronic control unit 40 also controls the bypass Kt, f control chip P22.
, the EGR control valve 24, the solenoid valve 45 (FIG. 2) of the hydraulic control circuit of the automatic transmission, and the ignition coil 46. The secondary side of the ignition coil 46 is connected to the power distributor 33. The charcoal canister 48 accommodates activated carbon 49 as an adsorbent, and connects the artificial side boat to the upper space of the fuel tank 43 via a passage 50, and connects the outlet side boat to a barge boat 52 via a passage 51. has been done. The purge boat 52 is located upstream of the throttle valve 3 when the throttle fP3 is at an opening smaller than a predetermined opening, and on the other hand, the purge boat 52 is located upstream of the throttle valve 3 when the throttle fP3 is at a predetermined opening or higher.
It is located downstream of No. 3 and receives negative pressure in the intake pipe. Open/close valve 53
has a bimetallic disk, and when the engine is at a low temperature below a predetermined temperature, it closes the passage 49 and stops releasing fuel evaporative gas into the intake system.

FIG. 2 is a block diagram showing details of the electronic control section 40. The electronic control unit 40 is composed of a microprocessor, and stores therein a CPU (central processing unit) 56 that performs calculations and control, a feedback start processing program to be described later, and programs for performing other EGR control processing, etc. aOM (read only memory) 57, 1tAM (random access memory) 5 for temporarily storing data;
8. (Second RAM 59 as a non-volatile memory element that receives power from the auxiliary 'It121X and retains the memory of essential data even when the fi function is stopped, A/
A D (analog/digital) converter 60 and a buffered l10 (input/output) device 61 are connected to each other via a bus 62. The outputs of the air flow meter 2, intake temperature sensor 28, water temperature sensor 30, air-fuel ratio sensor 31, and storage battery 37 are sent to the A/D converter 60. Further, the outputs of the throttle position sensor 29 and crank angle sensor 32 are sent to the I10 device 61, and the bypass flow control valve 22, EGR split valve 24, fuel injection valve 41, solenoid valve 45° and ignition coil 46 are sent to the I10 device 61. and receives input from the CPU 55.

An example of determining a warm-up increase value and starting air-fuel ratio feedback using the above configuration will be described below with reference to a diagram. A program for such processing is stored in the ROM 57.

FIG. 3 is a flowchart showing the startup routine,
This is a process to set the 177th period value for warm-up increase.

In step 301, the water temperature at engine start ゛rHWOya
- The water temperature is taken in from the water temperature sensor 30, and the initial increase value WLo is determined in step 302. This initial increment value WLo is obtained by calculating the increase rate in the temperature range from the lowest temperature that the engine encounters (e.g. -30°C) to the warm-up completion temperature (e.g. 80°C) in advance as a map, and interpolating this. demand. In step 303, step 3
The initial fuel increase value W L o obtained in step 02 is set as the warm-up fuel increase value FWL.
It is stored in the RAM 59 as . From now on, this warm bale increase value F
WL is used as a reference value for comparison in processing described later.

FIG. 4 is a flowchart showing an interrupt routine for each rotation, and an interrupt is executed for each revolution of the crankshaft.
Attenuation (subtraction processing) of the warm-up increase and processing to set a flag to permit air-fuel ratio feedback control are performed. In step 401, A is subtracted from the warm-up increase fiFWL stored in the memory.

This person may be a constant or a value depending on the engine load condition. In step 402, the warm-up increase amount F''WLd obtained by subtraction is compared with the feedback start value FWLf (FWLd≦FWL().The result of the determination is FWLa>
If FWLr, the process proceeds to step 403, where the feedback start flag bit f CF/B ) is set to O, and the interrupt routine program ends; on the other hand, if FWLd≦FWLt, the process proceeds to step 404, where the 7 lag f (F
/B) is set to 1. In this case, the feedback start value PWLf is selected to be a value close to the stoichiometric air-fuel ratio value, for example 1.05. If the content of the flag f (F/B) is 1, the process further advances to step 405 and warm-up increase -zpt,w
It is determined whether a satisfies the relationship (FLWd≧1). The reason why 1 is compared here is that only the increase in warm-up amount is considered as a problem, and the reduction in amount is not possible. If (FWL≧1), the subsequent processing ends, and (
If FWL<1), the process proceeds to step 406, sets the content of FWL to 1, and ends the process.

FIG. 5 is a flowchart showing the air-fuel ratio control routine, and shows the process of selecting either open control (control not based on feedback) or feedback control using the processing results shown in FIG. M4. Step 5
01, it is determined whether or not step 404 in FIG. 4 is established. If the flag f (F/B ) is 1, the process proceeds to step 502 and air-fuel ratio feedback control is started. Further, if the flag f CF/B ) is O, open control is continued.

FIGS. 6 and 7 show changes in the warm-up increase FWL depending on the engine rotational state. When the engine (E/G) rotational speed is constant (when the engine is warmed up with auto choke) as shown in Figure 6 (a), the leg wave pattern is as shown in Figure 6 (b). Feedback initiation is performed at a rate of −10,000,
When the engine rotational speed changes on the high side as shown in FIG. 7(a), the FWL wave setting characteristics change as shown in FIG. 7(b), and the feedback start time becomes earlier.

In addition, in the embodiment of the present invention, when setting the initial value of the warm-up increase, the cooling water temperature at the time of startup was taken in.
In addition, the temperature of the cylinder head, the temperature of the cylinder block, etc. can be used.

In addition, the minimum FWL is set for the water temperature THW, and the minimum FWL is set for the water temperature THW.
Air-fuel ratio feedback may be started based on a FWL value that is not attenuated more than WL.

According to the present invention, since the start of air-fuel ratio feedback can be optimized, drivability is improved and 0! It is possible to improve the deterioration in emissions that occurs when the engine becomes overrich due to air-fuel ratio roughness and feedback start delay caused by the fuel cell.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an electronically controlled fuel injection engine to which the present invention is applied, FIG. 2 is a block diagram showing details of the electronic control unit 40, and FIG. 3 is a flowchart showing a startup routine.
FIG. 4 is a flowchart showing the interrupt routine for each rotation.
Figure 5 is a flowchart showing the nitrous fuel ratio control routine, Figures 6 (a) and (b) are diagrams of warm-up increase changes when the engine rotation speed is one foot, and Figures 7 (a) and (b) are engine rotation speeds. FIG. 6 is a diagram showing a change in warm-up amount during gear shifting. 2.28.29.30, 31.32.35...Sensor, (1υ 40...Electronic control unit, 41...Fuel injection valve, 45...
...Solenoid valve, 46...Ignition coil, 56...
CPU, 57...ROI, 58.59...RA
M. 60... A/D converter, 61... i10 device, 62.
··bus. Agent Tatsuyuki Unuma (and 2 others) (12)

Claims (1)

[Claims] (1) Open control mode and 0! In an electronically controlled engine that performs optimal fuel injection by switching between feedback control and air-fuel ratio feedback control based on the output of a sensor, depending on the operating state of the engine,
An initial value for the warm-up increase is set based on the engine temperature, this initial value is attenuated at a predetermined rate for each engine rotation, and the feedback control is started when the value becomes equal to or less than a predetermined set value. A method for starting nitrous fuel ratio feedback in an electronically controlled wholesale engine, characterized in that: