JPS5848756A - Air-fuel ratio control method for engine - Google Patents

Abstract

PURPOSE:To obtain the most proper air-fuel ratio by a method wherein two sets of O2 sensors are provided at an exhaust manifold and at the central part of a catalyst respectively and a standard value for one O2 sensor is changed based on the output characteristic of the other O2 sensor. CONSTITUTION:The control circuit 64, effecting the operational control of the valve opening time of a fuel injection vlave 22 based on the detecting values of an airflow meter 4, a throttle sensor 10, a revolution number sensor 58 or the like, effects the feedback control of the air-fuel ratio based on the detecting values of the first O2 sensor 36, provided in the exhaust manifold 34, and the second O2 sensor 38 provided at the central part of a catalyst convertor 32, in a predetermined load zone. The control circuit 64 takes the detecting value of the second O2 sensor into it at a predetermined interval and when the value is decided that it is in a rich side or in a lean side with respect to the window of the catalyst continuously in a predetermined period of time, changes a comparative standard value for the first O2 sensor into the optimum value and compensates the change of the characteristic of the O2 sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control method, and particularly to an engine air-fuel ratio control method suitable for controlling the air-fuel ratio in an electronically controlled engine to an optimum value.

Generally, in this type of air-fuel ratio control method, an air-fuel ratio signal detected by a zero sensor installed in an exhaust branch pipe of an engine is input into an electronic control circuit, and the electronic control circuit controls the exhaust branch pipe based on the air-fuel ratio signal. If the air-fuel ratio to be used is rich, reduce the air-fuel ratio.

On the other hand, the thin (lean) pigeon coop becomes thicker.
This is a method of closing the door or controlling the injection time of the fuel injection device. Feedback (F
/B) It is called control.

The reason for controlling the air-fuel ratio as described above is that the purification power (conversion rate) of a catalytic converter such as a three-way catalyst installed downstream of the exhaust branch pipe is within a very narrow range (ζO range) near the stoichiometric air-fuel ratio. Therefore, the air-fuel ratio is maintained within this window to maximize the catalyst O purification ability.

By the way, as mentioned above, generally only one Hesenna used in the conventional air-fuel ratio control method is attached to the exhaust branch pipe. Furthermore, it is difficult to match the position of the 01 sensor attached to the exhaust branch VK with the window of the catalyst due to the effects of exhaust gas exhaust gas discharged from each cylinder of the engine and variations among the cylinders.

This ninth.

Conventionally, predictive control was performed to match the window, but feedback control was affected by changes in the characteristics of the t, +, and #Of sensors. by the way,
The ninth K to solve the above-mentioned problem is to add 7t to Ox- to the catalyst side, and in this way it will be easy to match it to the window of the catalyst. However, in such a control method, the feedback (F/B) control becomes very slow, so a delay in F/B occurs during a transient period, and the air-fuel ratio becomes rough. Emission (Emi)
ms-1on) becomes worse.9.

The object of the present invention is to solve the above-mentioned problems of the prior art.It is the ninth object of the present invention to adjust the air-fuel ratio to the window and compensate for the characteristic change of 0.27 cm. An object of the present invention is to provide an engine O air-fuel ratio control method that reduces the cost of catalysts.

This bag is the ninth to achieve the above purpose.
Next, install the first 02 senna in the 9 exhaust branch axillary pipes, and install the 02 senna in the second building on the downstream side, which is approximately in the center of the catalyst that purifies the exhaust gas, and adjust the air-fuel ratio from the sensor to jlllO. The signal is compared with a reference value, air-fuel ratio feed Para I control is performed based on the comparison result, and the second
It is detected whether or not the air-fuel ratio is within the window OII of the catalyst based on the air mm *-* from the sensor, and the detection result is determined to be rich or lean continuously within a certain period of time. The present invention is characterized in that the first reference value for the 02 senna is changed by a predetermined value when the air-fuel ratio is set to the optimum air-fuel ratio.

An embodiment of the present invention will be described in detail below with reference to the drawings.

No. 111 is an electronically controlled type 1 in which an embodiment of the present invention is implemented.
FIG. As shown in the figure, this embodiment includes an air cleaner 2 and an air 70-meter 4 as an intake air amount sensor provided downstream of the air cleaner sO. It is composed of an air flow meter 4ij, a measuring plate 4B rotatably provided in the chamber 4A, and a potentiometer 4C that detects the opening of the measuring plate 4B. Therefore, the amount of intake air is detected as the voltage output from the potentiometer 4c. Further, an intake air temperature sensor 6 is provided near the air flow meter 4 to detect the temperature of intake air.

A throttle valve 8 is disposed downstream of the air flow meter 4, and a throttle sensor 10 is disposed near the throttle valve 8 to detect the opening f of the throttle valve and output a throttle position signal.

This throttle valve 8 is provided in the driver's cab, and nine acceleration pedals 1 are provided.
1, it is designed to be linked.

! A surge tank 12 is provided downstream of the throttle valve 8, and a detour 14 that bypasses the throttle valve 8 is provided in the surge tank 12. An air valve 18 controlled by this detour 14Kit step motor 16 is provided. This air pulp 18
tj, when the engine is idle, the intake air bypasses the throttle valve 8 and passes into the surge tank 12 to control the engine speed to the target value.

Surge tank 12KF! After the intake manifold 20 is connected, the fuel injection valve 22 is placed centrally inside the intake manifold 20, and the engine 240 is connected to the engine combustion chamber 28. exhaust boat 3
The exhaust branch pipe 84K is connected to the exhaust branch pipe 84K1 through the exhaust branch pipe 84K1, and an inverter 32 filled with a three-way catalyst is connected behind it. Further, in the gathering part of the exhaust branch pipe 34 on the side connected to the exhaust port 30, a first 0! Says 36 is II
At the same time as the catalytic converter 32 is
Detecting the oxygen IIl position near the O downstream! 7 t38 to O is the center l16 of the catalyst of the catalytic converter 32!
or installed on the downstream side.

(In the ζOII example, it is attached to the center of the catalyst.

) Note that reference numeral 40 is a water temperature sensor that detects the engine cooling water temperature.

42 spark plugs of the engine 24 are connected to the distributor 44 and distributed! -44 is connected to an igniter 46. In addition, numeral 48 is an intake valve, 50 is an exhaust valve, 52 is a transmission, and 54Fi
This is a neutral start switch that detects the neutral position of the shift lever, and a 56Fi vehicle speed sensor.

Further, the distributor 44tC is provided with a pickup 5B as an engine rotation speed sensor and a signal rotor 62 fixed to the distributor shaft 60. For example, the crank angle reference position signal is transmitted to the electronic control circuit every 30 f of the crank angle. 64 is input. Therefore, the engine speed can be determined from the generation interval of the crank angle reference position signals and the number of crank angle reference position signals.

Exhaust gas recirculation (EGR) passage 66Fi exhaust branch pipe 34
and surge tank 12, and an on-off valve type exhaust gas recirculation (EGR) control valve 68 is connected to open and close the EGR passage 66 in response to electrical pulses.

These O sensors 4C16, 1O540, 36°38%s
4, the output of s6.58, and the battery 690 voltage are configured to be sent to the electronic control unit 64. fuel injection valve 2
2 is an intator corresponding to the cylinder! A pump 70 is provided near the second hold 20 and pumps fuel from a fuel tank 72 to the fuel injection valve 22 through a fuel passage 74.

The electronic control circuit 64 includes random access memories (RAM) 7g and 80, and read/write memory as shown in FIG.
Only memory (ROM) 82 and central sensing layer device (
CPU) 84, input/output circuit (Ilo) 86, analog/digital converter (MUDC38g), RAM78 and 110.ROM81 CPU84, l
1086 and a DC88Fi data bus 90. Note that the RAM 80 is supplied with power from the auxiliary power source even when the engine 24 is stopped KTh-, and serves as a trap so that the memory can be retained.

In addition, l1086 includes a crank angle reference signal output from the distributor 44, and a throttle sensor lO
Throttle position notes output from the neutral start switch 54, neutral switch signal output from the neutral start switch 54, air conditioner signal output from the near conditioner (not shown), ignition switch (
An ignition switch signal outputted from the igniter 46 (not shown), an ignition confirmation signal outputted from the igniter 46, an air-fuel ratio signal outputted from the ignition sensor 3B, etc. are input, and the air pulp 18 is controlled. An air pulp signal, a fuel injection signal for controlling the fuel injection valve 22 pipe, and a high point signal for controlling the igniter 46 are outputted.The ADC 88 also receives an intake air amount signal output from the airfmeter 4, an intake air amount signal outputted from the airfmeter 4, etc. The intake air temperature signal output from the air temperature sensor 6, the air-fuel ratio signal output from the first O0* sensor 36, the voltage from the storage battery 69, and the water temperature signal output from the water temperature sensor 40 are input, and each signal is sent to the ADC 88. The maps stored in the ROM 82 and the signals input and output to the I10@6 and ADC 88 are converted into digital signals according to the control status of the engine. Input or output.Furthermore, one electronic control circuit 64
1; is used as a parameter to calculate the fuel injection amount, and sends an electric pulse having a pulse width corresponding to the calculated fuel injection amount to the fuel injection valve 22. Electronic control circuit 641'i Air pulp 18 pulse motor 16, EGR control valve 68% automatic transmission oil pressure - control circuit so? Noid valve (not shown) and igniter 46
is designed to be controlled.

The operation of the electronically controlled engine configured as described above will be explained below.

In short, the operation of this complete example is to measure the air-fuel ratio in the nine exhaust branch pipes 34 connected to the engine 24 to the first sensor 3-
The air-fuel ratio at the center or downstream side of the catalyst of the catalyst comparator 32, which purifies the exhaust gas, is detected by the electronic control circuit 64 and is input to the electronic control circuit 64 to purify the exhaust gas. sensor 38
In this electronic control circuit 64, the air-fuel ratio signal from the first 01 sensor 36 is AD-converted by an ADC 88, and this AD-converted value F
OX is stored in RA and M2O, and stored in another area of %RAM80, and the predetermined reference value 0XVR and the AD conversion value F are stored.
OX is compared, air-fuel ratio feedback control is performed based on the comparison result, and an air-fuel ratio signal from Rust 2 0# Senna 3B is obtained via l1086.
When the air-fuel ratio signal from 6 is continuously on the rich or lean side for a certain period of time, when it is on the rich side, a predetermined value α is subtracted from the reference value 0XVR to create a new reference value 0X.
The reference value 0XVR is stored in the RAM 80 as VR, and when t*h is on the lean side, the reference value 0 The optimum air-fuel ratio is obtained by adjusting the air-fuel ratio of the catalyst to the catalyst window.

Below, 11 will be explained in detail based on Figures 3 and 4.
11. Figure 113 is book 11! The main routine related to the negative example is shown, and FIG. 4 is a book showing the routine including the same side.

In step 3-, the main routine is step 3o.

In step 301, the initial value tube is set to 0 order -, and in step 302, the feed parameter I (
F/B) Determine whether the condition is satisfied, and if the F/B condition is satisfied, 75-JINFBt*2 in step 303.
1) (Set TFBK'l") and step 30
Move on to 5. In step 302, if the F/l condition has not been established, proceed to step 304 (11), and in this step 304, set (reset) the flag IPIK'0'.
Then, in step S, the process moves to the OS. In step 305, it is determined whether the flag IP1 is set to 'l', that is, whether it is time to perform FB control. This step 3
0! ! If the flag storage FB is IO#, there is no need to perform FB control, so the process jumps to the return of step 340 and becomes 1. It was. Conversely, when the flag TFBK'l' is set in step 305, it is time to perform Fi% F/B control, so the process moves to step 306. In step 306, it is determined whether the flag IK I K"l' is set. In other words, it is determined whether or not integral (KI) control is to be performed.

In step 306, if the flag TKI is "OI', there is no need to perform KI control, so the process jumps to step 31G. Conversely, in step 306, the process jumps to step 31G.

If the flag IKI is determined to be "l" and is OK.

In order to perform KI control, a flag "T K I K'O" is set in step 307, an integral constant is calculated in step 308, and an integral correction amount ΔFAFt is set in step 309.
Output as the basic air-fuel ratio correction amount FAF. Step 31
G, it is determined whether the flag K5KIPK #1 # is set, that is, whether or not skip control is to be performed. In step 310, flag l5K
When IPK "o" is set, that is, when skip control is not performed.

Jump to step 316 without doing anything. In step 310, when the flag TSKIPK'l'' is set too low, the flag H8KIPK'O' is first set as a skip control sound, the skip calculation is performed in step all, and then the skip correction is performed in step 313. value Δ
R8 is output as the basic air-fuel ratio correction amount FAF, and further, in step 314, l'' is set in Booker TKI, and in step a18, 11!

J? Rough 31 S K jP L/% Te, jl
I 2 O0x 7 t 3 g to 0 air fuel ratio signal set based on i 1 judgment flag TOXRLK'l
” has been set, and if it has been set, the process moves to step 316, where the predetermined reference value 0XVRK is checked at a certain value tll, and a new reference value 0XVR is stored in the RAM.
80, then *D in step 317, the second
#o# is set in lean determination 7 lag l0XRL, which is set based on the air-fuel ratio signal from 00m+3't38, and the process moves to step 321. In step 3115K or i,
When the flag 10XRL is 10'', the process goes to step 318, and in step 818 it is determined whether the rich 411 constant 7 flag TOXRRK11'' is set, and if it is not set, it is determined that the flag is neither particularly high nor rich. Skip to step 321.

When the flag l0XRR is set to 1', the air-fuel ratio signal of the second Os sensor 38 is determined to be rich, and the process moves to step 319.In step 319, [,
III 0. A predetermined value tx from a predetermined reference value 0XVR for comparison with the AD conversion value FOX from the senna 36
t is subtracted and stored in the RAM 8G as a new reference value 0XVR, and in step 320, the rich determination flag T0XRRK"ON for the second Ol sensor 38 is set, and the process moves to step 321.

In step 321, the A from the first O0v sensor 36 is
The D conversion value FOX is taken in, and the process moves to step 322. In step 322, the current value FOX from the first Os sensor 36 is compared with a predetermined reference value 0XVR, and if the current value FOX is small, a flag is flagged in step 323.
0XRK'o' is set and the process moves to step 325. In step 322, the current value FOX is set to the predetermined reference value 0XVR.
If it is larger, move to step 324 and step 32
4, set flag 0XRK'l' and step 31
Move to 1. In this step 325, the current value FO
RAM l10 where the previous value of X is stored 0XOLD
0 is stored in the corresponding area, and the process moves to step 326.

In step 326, the second 01 sensor 38.

It is determined whether or not the signal is tied.

If "l" is set in the IIL time flag storage oxvR, step 327 is executed with 111:y9/T
Set OXVRK#0' to 0 then step 3
28KjPIA″c, No. 00*-kyl118 l1
The port O value OXR of 086 is loaded, and it is determined in step 32 whether this is also one. In step 329 %Ig! 00*Air-fuel ratio signal from sensor 38 is 9m,
If it is determined as y, the process moves to step 330, in which 1 is added to the lean counter CLOX at step 310, and the process moves to step 331. At step 331,
Insert the rich counter CROXK'O'' and proceed to step 3.
11 at 82, step 332 - y cow y ri CLO
If X is greater than or equal to a certain time A, it is determined that there is a shift to lean, and the process moves to step 333. In step 333, the glue one judgment flag T from the second Os sensor 38 is
0XRLK″l#t and lean counter C
Set LOXK#0#. At step 332.

If there is no AK error for a certain period of time, move to step 340. In step 329, the 200th. When the air-fuel ratio signal from the senna 38 is determined to be rich.

In step 334, a second 0 sensor'(lJi' of 8
The lean counter CROXKI is incremented, and in step 335, the lean counter CLOXK is set to "0".

That is, it is determined in steps 329 to 337 whether the rich or lean condition continues for a certain period of time. Next, in step 336, if the rich counter CROX is equal to or longer than the electric current time B, it is determined that the rich counter has deviated from the rich state, and in step 337, the rich judgment flag l0 Set CROXK'0''.

Next, make the main feathers based on the 4th map.

111E4 garden KjiPite, xfy1350t', ft
If there is an interrupt of J-JL 4 (mse.), the process moves to step 351 and it is determined whether the %F/l execution flag TFB is set (TFI-1). If the flag TFI is set in step 351, the $1 delay execution flag IDELAY is 'O' in step 352, and the OAD conversion value FO is output from the first Os sensor 36 in step 353.
Work on X. At step 8S4, the reference voltage 0XVR for comparison is compared with the FOX, and if FOX is high, 1 is set in step 2. In step 355, [1
ot-tytss glue) f75 g xOXR, the hook/HOXR is reset (i.e. T 0XR
-0), it is assumed that the comparison voltage has crossed, and a lean delay TDL is set in the delay counter CDELAY in step 356, and the process proceeds to step 3511. Also, in step 355, the flag TOXR
is #1'', the process jumps to step 361 and ends the first interrupt.If it is determined in step 354 that the MUD conversion value FOX is smaller than the reference value 0)I'VR, the process moves to step 357. , in step 357 the first 0!sensor 3
If the flag l0XR for 6 is “0#”, step 35
8, and in this step 358 the delay counter CD
The ELAYK rich delay TDR is set and the process moves to step 359. In step 357, if the flag 10XR is #1'', nothing is done and the process moves to step 363. In step 359, Fi and the delay execution flag TDELAY are set.
Set K'l'.

On the other hand, if it is determined in step 352 that the delay execution flag IDgLAYK'l is set,
Moving on to step 360, in this step 360,
The value obtained by subtracting #l" from the delay counter CDELAY is stored in the delay counter CDELAY, and the process moves to step 361. In step 361, it is determined whether the value of the delay counter CDELAY has reached 10", that is, whether the delay has ended, and the process ends. If not, step 3
63, and when it is determined in step 361 that the process has ended, in step 36'2, the skip flag
' is set and the process moves to step 363, ending the 5th interrupt.

The timer interrupt control operates as described above.

In this way, in this example #i, when the O air-fuel ratio signal is continuously output from the second Ot sensor 38 to either lean or rich for a certain period of time, lll00
The reference value to be compared with the air-fuel ratio signal from the s sensor 36 is changed by a predetermined value, the air-fuel ratio signal from the first O0t sensor 36 is compared with the changed reference value, and the air-fuel ratio feedback is performed based on the comparison result. The control and delay thereof are used to obtain an appropriate air-fuel ratio.

As described above, according to the present invention, the exhaust branch pipe is set at 0! The O air-fuel ratio signal is taken into the electronic control circuit from the can sensor installed in the central part of the NANSA and the downstream side of the catalyst for exhaust gas purification, and the air-fuel ratio signal from the 1st 2nd OF sensor within a predetermined period is input. A reference value for comparison with the air-fuel ratio signal from the first oxygen sensor is set by a predetermined value when it is determined that the air-fuel ratio signal is continuously on the rich or rebound side with respect to the catalyst window within a certain period of time. Since the air-fuel ratio feedback control is performed based on the comparison result between this change and the air-fuel ratio signal from the first Ov sensor, the Ov
This has the effect that it is possible to maintain a proper air-fuel ratio by compensating for changes in the characteristics of the t-sensor, and it is also possible to reduce the cost of the catalyst.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an electronically controlled engine to which an embodiment of the present invention is applied, Figure 2 is a block diagram showing the electronic control circuit in detail, and Figure 3 is a diagram showing an embodiment of the present invention. The flowchart shown and the IE4 diagram are the same flowchart. 24...Engine, 22...Fuel injection valve, 34...
・Exhaust branch pipe, 32...Catalytic converter, 36 ・"
Building 1 O0t sensor, 3 B-@2's Q, SE:/su,
64...Electronic control circuit. Agent Tatsuyuki Unuma and 2 others)

Claims (1)

[Claims] (1) In the exhaust branch pipe connected to the engine! In addition to installing the No. 11 Os sensor, a second Os sensor is installed approximately in the center or downstream of the catalyst that purifies exhaust gas, and the air-fuel ratio signal from the first Os sensor is compared with the reference value. Air-fuel ratio feedback control is performed based on the comparison result, and it is detected whether the air-fuel ratio is within the window of the catalyst based on the air-fuel ratio signal from the second Of sensor. When the detection result is continuously determined to be rich or rich for a certain period of time, the reference value for tlX1 is changed by a predetermined value to achieve the optimum air-fuel ratio. Fuel ratio control method.