JPS5934447A - Air-fuel ratio control unit for engine - Google Patents

Abstract

PURPOSE:To obtain improved control efficiency by correcting the quantity of initial corrector in a memory by reiterating addition or subtraction as prespecified until the transient air-fuel- ratio of an engine reaches a target value and by rewriting the quantity of initial correct in the memory into the above optimum quantity of correction. CONSTITUTION:When the air-fuel ratio is lean during the time of engine acceleration, the quantity of the initial correction CF, which is decided by detection values of both a throttle sensor 7 and rotary sensor 11, is read out so that pulse width T of an injection pulse signal is corrected for fuel injection. At step 29, it is judged whether the air-fuel-ratio has changed from a lean side to rich side according to a detection value by an O2-sensor 9 after fuel injection. If the air-fuel ratio atill remains lean, prespecified quantity alpha is operated to the quantity of initial correction CF to go back to step 28. When the air-fuel ratio hasturned rich at step 29, the quantity of initial correction is rewritten into current quantity of correction CF, or the optimum correction, considering the transient quantity of correction CF optimum. Next, when acceleration is carried out from this state, the quantity of fuel injection can be corrected with the optimum quantity of correction from the beginning. As a result, the theoretical air-fuel ratio can quickly be achieved, while emission can greatly be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an engine.

Generally, as an engine air-fuel ratio control device d, the oxygen concentration in the exhaust gas is detected by an 02 sensor installed in the exhaust passage, that is, the air-fuel ratio sensor, and the amount of fuel supply or intake air is adjusted according to the output of the air-fuel ratio sensor. There is one that performs feedback control of the air-fuel ratio of the air-fuel mixture by adjusting the air-fuel ratio. With such an air-fuel ratio control device, it is possible to control the air-fuel ratio of the air-fuel mixture to a target value such as the stoichiometric air-fuel ratio of 14.7 with relative accuracy during steady engine operation. During a transient period, for example during acceleration, the air-fuel ratio of the air-fuel mixture deviates from the target ++& to the lean side or rich side due to a delay in fuel supply due to an increase in intake air or a delay in signals from the control system such as the 02 sensor. In such cases, simply performing feedback control of the air-fuel ratio according to the output of the 02 sensor will take time for the air-fuel mixture to reach the target air-fuel ratio, and the HC in the exhaust gas,
There are problems such as an increase in CO, etc., which worsens emissions (exhaust gas purification).

Conventionally, in order to prevent such deterioration of emissions, for example, for engines equipped with fuel injection valves, the correction amount during transient times for each operating state is determined through experiments, etc., and then stored in memory. When the engine accelerates, add 1 to the fuel injector using the memorized auxiliary E) 1! U injection pulse signal (7) C) The V pulse width is corrected sequentially, thereby controlling the air-fuel ratio of the air-fuel mixture to the target value in a short time (see Japanese Patent Publication No. 55-26299).

However, with the conventional air-fuel ratio 'tllj611] device, if the engine condition changes due to aging, etc.
There is a problem in that the supplementary IE obtained in advance cannot necessarily be the optimum value, and therefore the control efficiency of the air-fuel ratio control during transient times deteriorates.

This invention was made in view of the above-mentioned conventional problems.In an engine that performs feedback control of the air-fuel ratio according to the output of the 02 sensor installed in the exhaust passage, the mixture air volume or combustion
When the air-fuel ratio reaches the target value, the air-fuel ratio is corrected sequentially by t11i by the initial correction in the storage device or by the correction amount obtained by repeatedly adding or subtracting a predetermined acid to this, and the initial correction value in the storage device is It is an object of the present invention to provide an air-fuel ratio control device for an engine that improves control efficiency by rewriting the correction amount into an optimal correction obtained by repeating the above addition or subtraction.

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

FIG. 81 and FIG. 2 show an air-fuel ratio control device for an engine according to an embodiment of the present invention. In the figure, 1 is an engine, and an intake passage 2 of the engine 1 is provided with a throttle valve 4 and a fuel injection valve 5, as well as a negative pressure sensor 6 and a throttle sensor 7. In this embodiment, the throttle sensor 7 serves as a transient sensor for detecting a transient state of the engine. Further, the upstream end of the intake passage 2 is connected to an air cleaner 8. On the other hand, engine 1
According to the oxygen concentration in the exhaust gas, the exhaust passage 3 of the engine 1
An 02 sensor (air-fuel ratio sensor) 9 is provided to detect the air-fuel ratio of the air-fuel mixture taken into the air-fuel mixture. is approximately constant, rapidly decreases near the stoichiometric air-fuel ratio, and thereafter remains approximately constant at that decreased value. 0 of the above exhaust passage 3
A catalyst 10 for purifying exhaust gas is disposed downstream of the two sensors 9. Further, a rotation sensor 11 is provided on a side wall of the engine 1 to detect the engine rotation speed.

In FIG. 2, reference numeral 13 indicates a negative pressure sensor 6. A/D that converts each output of the throttle sensor 7 and rotation sensor 11 into A/D
Converter, 14 is a comparator that compares the output voltage of 02 sensor 9 with reference voltage E, 15 is an input interface that receives the output of comparator 4, 15 is CPU, 17 is a table of transient correction amount CF. .

18 is a ROM that stores the arithmetic processing program of the CPU 16 shown in the flowchart in FIG.
117 tapes/l/1. [This is an AM used to store I and update the stored data.

Here, the above-mentioned tables I and IT were created by determining the transient surface 1E total CF in each operating state through experiments, etc., and storing them at addresses determined by the engine speed and throttle valve opening. Table I shows the correction 1c when the air-fuel ratio of the mixture shifts to one side.
Table (2), which stores F, is a table that stores CF, which is corrected when the air-fuel ratio shifts to the rich side.

Reference numeral 19 denotes an output interface for applying one injection saving pulse signal, which has been arithmetic processed by C:PUl 6, to the fuel injection valve 5. 13 to 19 above constitute a control circuit 12. During steady operation of the engine, the control circuit 12 receives the output of the 02 sensor 9 and feeds back the air-fuel ratio of the mixture to the target value (stoichiometric air-fuel ratio). During engine transients, ltA is maintained until the air-fuel ratio of the mixture reaches the target value.
While sequentially correcting the pulse width T of the ejection pulse signal using the initial correction amount CF in Mls or the correction amount obtained by repeatedly adding or subtracting a predetermined value α to this, the pulse width T of the ejection pulse signal is corrected.
Control is performed to rewrite the initial correction amount in Ml 8 to the optimum correction amount that is finally exhausted by repeating the above-mentioned addition or subtraction.

Further, FIG. 3 shows a flowchart of the arithmetic processing of the CPUI 6, in which 20 is a step of storing tables I and II in the ROM 17 as initial values in the RAMI 8, and 21 is a step of storing tables I and II in the ROM 17 as initial values, and 21 is a step of storing the data from the input interface 15 to the 02 sensor Read the detected value as the output value of the comparator 14,
22 is a determination step of determining whether the air-fuel mixture is at the target air-fuel ratio based on the stored detected value of the 02 sensor 9; 23 is the internal power value of both the negative pressure sensor 6 and the throttle sensor 7; The pulse width T of the injection pulse signal, which is determined by
The corrected pulse width T-T+β, T=T-
This is a step in which the fuel injection valve 5 is caused to inject fuel using the injection pulse signal β.

Here, the processing flow for determining the injection pulse signal from the divided outputs of the negative pressure sensor 6 and the throttle sensor 7 is well known, and detailed explanation thereof will be omitted.

Further, 24 is a step of reading the rain detection values of the throttle sensor 7 and rotation sensor 11 from the A/D converter 13 and storing them in registers T' and R; 25 is a step of differentiating the stored output of the throttle sensor 7, and A determination step of determining whether or not is in an acceleration state, 26 is 02 after fuel injection
This is a determination step in which the detected value of the sensor 9 is read and it is determined whether the air-fuel ratio of the air-fuel mixture is lean or rich.

27 is a step of reading out the initial correction amount CF from the address determined by the detection values of both the sensors 7 and 11 of Table I stored in the RAM 18, and 28 is a step of correcting the pulse width T of the injection pulse signal based on the initial correction amount CF. Then, the step 29 is a step of injecting fuel according to the injection pulse signal with the pulse width T=T+CF.
A determination step of reading the detected value of the sensor 9 and determining whether the detected value has been reversed, that is, whether the air-fuel ratio of the air-fuel mixture has changed from lean to rich; 30 is the initial correction amount CF;
The step of adding a predetermined amount α to , 31 is the above table ■
This is a step of rewriting the initial correction amount in the current correction amount CF. Further, step 32 is a step of reading out the initial correction amount CF from the address determined by the rain detection values of the slot deflection sensor 7 and rotation sensor 11 in the table H in the RAM 1B, and 33 is the step of reading the pulse IiT of the injection pulse signal.
is corrected based on the initial correction 1ic:p, and its pulse I
Step 34 of injecting fuel with MT=T-CF reads the detected value of the 02 sensor 9 after fuel injection, and determines whether the detected value has been reversed, that is, whether the air-fuel ratio of the mixture is from rich to lean. 35 is a step of subtracting a predetermined amount α from the initial correction amount CF, and 36 is a step of rewriting the initial correction amount in the table 1■ to the current correction amount CF. be.

Next, the operation will be explained using FIG.

While the engine is operating, air is drawn into the intake passage 2 according to the opening degree of the throttle valve 4. At this time, the negative pressure sensor 6 detects the intake negative pressure on the downstream side of the throttle valve 4, and the throttle sensor 7 detects the intake negative pressure downstream of the throttle valve 4. The rotation sensor 11 detects the engine rotation speed, and the 02 sensor 9 detects the air-fuel ratio of the air-fuel mixture from the oxygen concentration in the exhaust gas. The output of is applied to the control circuit 12. In this control circuit 12, an A10 converter 13 A/D converts the outputs of the negative pressure sensor 6, throttle sensor 7, and rotation sensor 11, and a comparator 14 converts the output voltage of the 02 sensor 9 and the reference 1 direct current E. and the comparison Fa
The output signals of 14 are inputted to an input interface 15.

During steady operation of the engine when the opening degree of the throttle valve 4 is approximately constant, the CPU 15 performs the following operations as shown in FIG.
First, proceed along the path of steps 20, 21, and 22, and in step 20, store the transient correction amount tables I and fl stored in 10M17 in the RAM 18, and in step 21
At step 22, the detected value of the 02 sensor 9 is read as the output of the comparator 14 from the input interface 15, and it is stored in the register A. At step 22, the stored comparison force is "1° or 0°, that is, the air-fuel ratio. This only indicates that the air-fuel ratio is rich or rich, and does not correspond to the target air-fuel ratio.
From there, proceed through steps 23, 24, and 25, and in step 23, apply negative pressure so that the air-fuel mixture reaches the target air-fuel ratio, that is, if the current air-fuel ratio is close to 1, it becomes rich, and if it is rich, it becomes lean. The pulse width T of the injection pulse signal determined by the side output values of the sensor 6 and the throttle sensor 7 is corrected by a predetermined amount β (T=T+β, T=T−β), and the corrected injection pulse signal is output to the output interface 19. In addition to the fuel injection valve 5, fuel is injected via the fuel injection valve 5. Also, in step 24, both side output values of the throttle sensor 7 and rotation sensor 11 are read from the A/D converter 13,
Store them in registers TI, R and step 2
It is determined whether the engine is accelerating or not based on the change in the detected value of the throttle sensor 7 stored in step 5. If the engine is not accelerating, that is, it is in steady operation, the process returns to step 21 and the route from steps 21 to 25 is followed. cycle.

In this way, during steady engine operation, the fuel injection t is 0.
Feedback control is performed according to the output of the second sensor 9, and the air-fuel ratio of the air-fuel mixture repeats minute fluctuations between lean and rich, so that the air-fuel mixture taken into the engine is controlled to approximately the target air-fuel ratio. It is something.

When the engine is accelerating, the cpty 16 proceeds from step 25 to step 26, reads the detected value of the 02 sensor 9, and determines whether the air-fuel ratio of the air-fuel mixture is lean or rich, If it is off to the lean side, proceed through steps 27° and 28.29, and check the throttle sensor 7 when acceleration starts in step 27.
and RAM1 determined by both side output values of the rotation sensor 11.
The initial correction amount CF is read from the address in Table I in step 28, the pulse width T of the injection pulse signal is corrected based on the initial correction @ CF read out in step 28, and the corrected injection pulse signal is sent via the output interface 19. In addition to the fuel injection valve 5, the fuel injection valve 5 also injects fuel. Then, in step 29, the detected value of the 02 sensor 9 after fuel injection is read to determine whether the air-fuel ratio of the mixture has changed from the lean side to the rich side. If the air-fuel ratio is still lean, the pulse width T is still Since it is short, the CPU 15 proceeds to step 30, adds a predetermined amount α to the initial correction amount Cp, returns to step 28, and circulates through steps 28-30. If the air-fuel ratio becomes rich in step 29, it is considered that the transient correction amount CF is the optimum value, so the CPU 6 proceeds from step 29 to step 31, and stores the The initial correction amount (2) is rewritten to the current correction IcF, that is, the optimum correction amount, and the process returns to step 21, where the steady operation state is established and feedback control is performed again.

Further, when the engine is accelerating and the air-fuel ratio of the air-fuel mixture deviates to the rich side, the CPU 16 proceeds from step 26 to steps 32, 33, and 34, and then steps 3.
5.33.34, or proceed from step 34 to step 36 and return to step 21,
In step 32, the initial correction tCF is read from the address of table H in RAMI s determined by the side output values of the throttle sensor 7 and rotation sensor 11, and in step 33, the pulse width T of the injection pulse signal is determined based on the initial correction 1 cF. T-Cp is corrected, and the corrected injection pulse signal is used to perform fuel injection, and step 34
In step 35, it is determined whether the air-fuel ratio has changed from rich to rich based on the detected value of the 02 sensor 9, and in step 35, the initial correction amount C is determined.
A predetermined amount α is subtracted from p, and in step 36, the initial correction amount in the table ① in the RAM 1s is rewritten to the optimum correction amount.

In this way, when the engine accelerates, the fuel injection amount is λAM
The mixture is sequentially corrected by the initial correction amount in 18 or by the correction amount obtained by repeatedly adding or subtracting a predetermined amount to this, and thereby the air-fuel mixture is quickly controlled to the target stoichiometric air-fuel ratio.

At that time, the initial correction amount in RAM1g is rewritten with the optimum correction amount obtained by repeating the above addition or subtraction, so the next time you accelerate from the same driving condition, the fuel injection system will use the optimum correction amount from the beginning. correction - this allows the stoichiometric air-fuel ratio to be reached more quickly and also significantly improves emissions. In particular, even if the injection characteristics of the fuel injection valve 5 or the air-fuel mixture distribution characteristics of the intake manifold change over time, the optimum initial correction amount is always stored in the RAM 1g. The air-fuel mixture can be controlled to the target air-fuel ratio more quickly than with other systems.

In the above embodiment, the amount of fuel in the mixture is corrected when the engine accelerates, but this correction may also be made for the amount of air in the mixture. Further, as a flowchart of the processing procedure of the CPU in the control circuit, a processing flow different from that shown in FIG. 3 may be used as long as it achieves the same function.

Furthermore, although the embodiment L has been described with respect to air-fuel ratio control during engine acceleration, the present invention can of course also be applied to air-fuel ratio control during engine deceleration. Further, the present invention can also be applied to an engine equipped with a carburetor instead of a fuel Mllf injection valve.

As described above, according to the present invention, in an engine air-fuel ratio control device l that performs feedback control of the air-fuel ratio of the air-fuel mixture according to the output of the 02 sensor provided in the exhaust passage, , sequentially correct the amount of air or fuel in the air-fuel mixture with the initial correction acid in the storage device or with urasho acid obtained by repeatedly adding or subtracting a predetermined amount to the initial correction acid until the air-fuel ratio reaches the target value; Since the initial correction acid in the memory device is rewritten to the optimum correction wax obtained by repeating the above addition or subtraction, the control efficiency during engine transients can be greatly improved, and the air-fuel ratio of the mixture can be quickly adjusted. In addition to being able to control the target value, it has the effect of significantly improving emissions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an air-fuel ratio control device for an engine according to an embodiment of the present invention, FIG. 2 is a circuit diagram of the device, and FIG. 3 is a flowchart of the processing procedure of the CPU of the device. ◎ 1...Engine, 7...Throttle sensor (transient sensor)% 9...02 sensor (air-fuel ratio sensor), 12
...control circuit, 17.18...艮OM, ltA
M (storage device). Patent applicant: Toyo Kogyo Co., Ltd. Agent: Patent attorney Ken Hayase - Figure 1

Claims (1)

[Claims] (1) An air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture taken into the engine, a transient sensor that detects the transient state of the engine, and a sensor that corrects the amount of air or fuel in the air-fuel mixture during engine transients. A storage device that stores the initial correction amount in the operating state, and feedback control of the air-fuel ratio of the air-fuel mixture in response to the output of the air-fuel ratio sensor during steady engine operation, and control of the air-fuel mixture when a transient state is detected by the transient sensor. The amount of air or fuel in the mixture is sequentially corrected using the above initial correction amount or by the correction amount obtained by repeatedly adding or subtracting a predetermined amount to the above initial correction amount until the air-fuel ratio reaches the target value, and the initial correction value in the storage device is An air-fuel ratio control device for an engine, comprising a control circuit that rewrites the correction amount into an optimal correction amount finally obtained by repeating the above addition or subtraction.