JPS61101644A - Air-fuel ratio controlling apparatus - Google Patents

Abstract

PURPOSE:To prevent the air-fuel mixture from becoming over-ruch, by setting the value of feedback factor alpha for stopping feedback control of the air-fuel ratio at the time of fuel cut at a specific value in an apparatus in which judgement is made from the output of an O2-sensor whether the air-fuel mixture is rich or lean and the value alphais detected from the result of the above judgement. CONSTITUTION:In normal operation of an engine, a base injection pulse width Tp is calculated by an arithmetic circuit 3 from the output signals of an air-flow meter 1 and a rotation sensor 2, and a feedback factor alpha is calculated by an alpha-value calculating circuit 7 on the basis of the result of judgement made by an air-fuel ratio judging circuit 6 to which the output of an O2-sensor 5 is furnished. The final injection pulse width Ti is calculated by correcting the above pulse width Tp by an arithmetic circuit 4 on the basis of the value alpha, etc. On the other hand, in case that the conditions of fuel cut are satisfied at the time of deceleration, changeover circuits 11, 13 are switched respectively to the sides of clamping circuits 12, 14 in response to the fuel-cut signal given from a fuel-cut circuit 15 to clamp the value alpha at a center value alphai based on the valve alpha at the time of idling operation, and the final injection pulse width Ti is calculated by use of the value alphai when supply of fuel is recommenced.

Description

[Detailed description of the invention]

(Industrial Application Field 1 The present invention is directed to a fuel injection device for a vehicle engine.
This relates to an air-fuel ratio control device that maintains the air-fuel ratio of the air-fuel mixture near the stoichiometric air-fuel ratio through feedback control based on the signal from the 01 sensor, and in particular relates to a field with a feedback coefficient α that is clamped when the feedback is stopped due to a fuel cut. .

[Backbone of the invention] The air-fuel ratio control device for the fuel injection device has a system in which a signal from an Oi sensor is determined to be rich or lean by an air-fuel ratio determination circuit.
By multiplying the components of the PI multiplied signal, for example Pla, that is, the step voltage drop in the rich case and the step voltage rise in the lean case, for example, 1 ± 25
% is calculated and input to the fuel injection pulse width calculation circuit. Then, in that circuit, the injection pulse width Ti is calculated from the basic pulse width Tp based on the intake air layer and engine speed, the above α value, the correction coefficient KH, etc., and fuel is injected from the injector based on this. There is. From this, the value of the feedback coefficient α is determined when the air-fuel ratio is set to L! when performing feedback control using the signal from the 02 sensor. I! This is an important element for maintaining the air-fuel ratio near the stoichiometric air-fuel ratio, and α=1 corresponds to the stoichiometric air-fuel ratio. By the way, in the case of actual feedback control, if we look at the fluctuation state of the α value that constantly fluctuates, we find that α does not always change due to variations in the various products of the control system and changes over time.
It does not fluctuate around 1. In other words, the center of the range of variation of this value may shift to a side larger than 1 and shift toward the rich side overall, or conversely, shift toward a side smaller than 1 and shift toward the lean side overall. be. In this case, the value of α-1±δ<δ is the amount of deviation) corresponds to the actual ai (stoichiometric air-fuel ratio in the I system). [Prior art and problems l] Here, the above feedback control is as follows: It does not occur in all operating states of the engine, but it stops until the 0□ sensor is activated or when it is abnormal, when it is cold, when starting, when fuel is cut, etc.This feedback stop occurs. Sometimes, the feedback coefficient α is conventionally clamped uniformly to α-1, which is 10. Therefore, in the case of fuel cut, in the process of returning afterward,
The fuel injection amount is determined by the clamped α-1 value until actual feedback control is performed using the 01 senna signal. On the other hand, when the engine speed drops below a certain value with the accelerator being released and the fuel is restored, the engine immediately shifts to idling operation, so the fuel injection c) in this case greatly affects exhaust gas and the like. Therefore, if the center value of α is shifted due to the above-mentioned product variations, etc., and the value of α′ is on the lean side, which is smaller than 1, as shown in Figure 3 (C), The clamped value of α=1 is located on the rich side. Then, when returning to fuel, the actual α
By performing fuel injection determined by α = 1 on the rich side of Φ center line a', the air-fuel ratio becomes overrich and the unburned phosphorus content in the exhaust gas increases as shown in Figure 3 Φ). However, there are problems such as poor starting performance. [Object of the Invention] In view of the problems in the prior art described above, the present invention aims to prevent overriching when returning from a state in which feedback control is stopped due to fuel cut, and to improve exhaust gas purification and startability. The purpose of the present invention is to provide an air-fuel ratio control device that achieves the following. [Configuration of the Invention] For this purpose, the configuration of the present invention is 01t? The air-fuel ratio judgment circuit judges the signal from the sensor as lean or rich, and α
In the control system used to determine the fuel injection pulse width by determining the value of the feedback coefficient α in the value calculation circuit, only the α value in the idling state is studied and its α center value α1 is determined.
When feedback is stopped due to fuel cut, α = α
The main idea is to clamp the fuel to the value of i and set the fuel injection when returning to fuel to correspond to the actual stoichiometric air-fuel ratio of the control system to prevent over-richness when transitioning to idle link. That is.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described based on the drawings. In Fig. 1, we will first explain the basic fuel 181 injection q'' judgment υβ system.The intake air mQ captured by the air flow meter 1 and the engine rotation speed N from the rotation sensor 2 are the basic injection pulse width output stop. The basic injection pulse width T p is calculated by Tp = KQ/N (K is a constant), and this pulse width - [p is input to the fuel injection pulse width calculation circuit 4. In addition, the signal from the 02 Senna 5 is input to the air-fuel ratio determination circuit 6, which outputs the P value (proportional valve) when the air-fuel ratio is rich or lean.Based on this, the αla calculation circuit 1 calculates the feedback coefficient α. This is calculated and input to the fuel injection pulse width calculation circuit 4. Furthermore, it has correction elements 8 such as water temperature, starting temperature, intake air temperature, etc., and the correction signal from this is also input to the fuel injection pulse width calculation circuit 4. . In this way, the fuel injection pulse width calculation circuit 4 calculates the basic injection pulse width Tp. Feedback coefficient α9 Various correction systems v! iK +1.
The injection pulse width T1 is determined by using the mill correction pulse Ts in the history.
Calculated using the following formula. ■ i = Tp ・ α (1+ K
I-1> + T S Based on this pulse width T1, the drive circuit 9 opens the injector 10, thereby performing a predetermined fuel injection. Next, to explain the fuel cut control system, in the control system 45, a switching circuit 11 and a fixed circuit 12 that makes the pulse width T: approximately zero are connected to the fuel injection pulse width calculation circuit 4 in a bypass manner. α1lOr>The output circuit 7 is also connected to the switching circuit 13 and a fixed circuit 14 fixed to α-αi in a bypass manner. The output of the fuel cut circuit 15 is used to switch the switching circuits 11 and 13. In addition, it has an idle judgment circuit 16 as a fli control system that learns the actual α center field of the control system, and this idle judgment circuit 1G and the αlid C'J output circuit 4 output side are connected to the α center 1if [learning circuit 17]. It is connected to the fixed circuit 14 via. The idle determination circuit 1G generates an output for a predetermined period of time when the accelerator is released and the engine speed is, for example, 800+''pilt or less.The learning circuit 17 generates an output for a predetermined period of time when the accelerator is released and the engine speed is 800+''pilt or less. The idle α value αi output from 7 is input, added, and averaged to find the center of α (Dαi,
The value of αi thus learned is stored in the fixed circuit 14. Next, the operation of the device configured in this way will be explained. First, normal fuel injection control will be explained. Since the fuel cut circuit 15 does not output a cut signal, the switching circuit 11.13 switches to the fuel injection pulse width control circuit 4.
It has been switched to the α output circuit 7. Therefore, air 70, meter 11, rotation sensor 2 signals Q, N
Accordingly, the basic injection pulse width calculation circuit 3 calculates the basic injection pulse width p, and further, based on the judgment result of the air-fuel ratio judgment circuit 6 based on the signal from the 01 sensor 5, α is calculated by the α value calculation circuit. . Based on this and the correction element 8, the fuel injection pulse width "i" is calculated in the fuel injection pulse width calculation circuit 4. Then, by injecting fuel with the injector 10 based on the fuel injection pulse width T+, the air-fuel ratio is near the stoichiometric air-fuel ratio. On the other hand, in this state of feedback control, a fuel cut condition is established during deceleration when the accelerator is released.Then, a cut signal is output from the fuel cut circuit 15, and the switching circuit 11 is switched to the fixed circuit 12. Therefore, the pulse width T i is fixed to approximately zero by the fixed circuit 12, resulting in a fuel cut state.Furthermore, the switching circuit 13 is also switched to the fixed circuit 14 by the cut signal. Under the idle condition before the 111 cut, the actual αφ cardiac value αi of the control system has already been learned by the idle judgment circuit 1G and the αφ cardiac study circuit 17 and stored in the fixed circuit 14, and therefore this central value αi is input to the fuel injection pulse width calculation circuit 4 and clamped to α-αi.Next, when the fuel cut condition is canceled due to a decrease in the engine speed, for example, and the fuel is restored, the switching circuit 11
．． 13 is returned to its original value, and the pulse width Ti is again suppressed in the fuel injection pulse width calculation circuit 4, but at this time, the feedback coefficient J, which was clamped during the fuel cut, is repaired.
Calculated using the following formula. Ti=Tp ・αi (1+KH) +Ts and,
After the fuel injected with this pulse width is detected by the 02-YU5, the control returns to the normal feedback control described above, and this state is illustrated in FIG. 2. In this way, when the fuel is restored after a fuel cut, the fuel injection is determined based on the αφ center value αi of the actual control system 80 under idle conditions, so the air-fuel ratio is set from the beginning to the stoichiometric air-fuel ratio specific to that control system. becomes. And I will move to Idol Link! The first case results immediately without the air-fuel ratio changing significantly with the α value. It goes without saying that, except when the fuel f1 is cut when J3 and feedback are stopped, it is clamped to α-1 as in the conventional case. Although one embodiment of the present invention has been described above, it is not limited to the above embodiment. Further, the above system can also be processed using microcomputer C software. Effect 1 of the invention As is clear from the above explanation, air-fuel ratio control 3 of the present invention
According to the I+ device, when the center value of the feedback coefficient α deviates due to variations in products in b, which is feedback-controlled by the injector method, it is
'Since it is used to restore fuel after fuel cut under the control, -
Compared to normally clamping at α-1, A-bridge formation is prevented and the exhaust gas purification is improved. This also makes it stable against product variations and changes over time.)
J1゛Gas characteristics are 19.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the device according to the present invention, Fig. 2 (f) to (C) are characteristic curve diagrams, and Fig. 3 (2) to (C)
is a conventional characteristic diagram. 4...Fuel injection pulse width calculation circuit, 5...Ol sensor, 6...Air-fuel ratio determination circuit, 7...α value calculation circuit,
13...Switching circuit, 14...α fixed circuit, 15...
・Fuel cut circuit, 16... Idle judgment circuit, 17
...αφ Psychological Learning Circuit Patent Applicant Fuji Heavy Industries Co., Ltd. Agent Patent Attorney Nobu Kobashi Ukiyo Patent Attorney Susumu Murai r21X3 FfrIv'1 Saiz! 4;.

Claims (1)

[Claims] The air-fuel ratio determination circuit determines the signal from the O_2 sensor as lean or rich, and the α value calculation circuit determines the value of the feedback coefficient α.The control system uses only the α value in the idling state to determine the fuel injection pulse width. An air-fuel ratio control device characterized in that the central value of α is determined by learning, and when feedback is stopped due to fuel cut, clamping is performed to the value of α=@αi@.