JPH04191440A - Self-diagnostic device of air-fuel ratio feedback control system in internal combustion engine - Google Patents

Self-diagnostic device of air-fuel ratio feedback control system in internal combustion engine

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Publication number
JPH04191440A
JPH04191440A JP31620590A JP31620590A JPH04191440A JP H04191440 A JPH04191440 A JP H04191440A JP 31620590 A JP31620590 A JP 31620590A JP 31620590 A JP31620590 A JP 31620590A JP H04191440 A JPH04191440 A JP H04191440A
Authority
JP
Japan
Prior art keywords
air
fuel ratio
failure
feedback control
engine
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP31620590A
Other languages
Japanese (ja)
Inventor
Hiroshi Yukinari
行成 弘
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nissan Motor Co Ltd
Original Assignee
Nissan Motor Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nissan Motor Co Ltd filed Critical Nissan Motor Co Ltd
Priority to JP31620590A priority Critical patent/JPH04191440A/en
Publication of JPH04191440A publication Critical patent/JPH04191440A/en
Pending legal-status Critical Current

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  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

PURPOSE:To prevent an erroneous diagnosis and improve the self-diagnostic precision by detecting a condition in which a fouling degree by carbon of the film of an air-fuel sensor, and prohibiting the failure diagnosis of an air-fuel ratio feedback control system at the time of detecting this. CONSTITUTION:On the basis of the output signal of an air-fuel ratio sensor B installed to the exhaust passage of an internal combustion engine A, the failure of an air-fuel ratio feedback control system C is self-diagnosed. In the above device, on the basis of the feedback control signal of the air-fuel ratio feedback control system C, the presence of the failure is judged by a means D. The operating time every time of the engine is measured by a means E. Further, the engine temperature is detected by a means F. The frequency of a determined operating state in which the measured operating time is less than a determined value and the engine temperature at the time of operation end is less than a determined value is detected by a means G. When the detected frequency of the determined operating state is a determined value or more, the failure judgment is prohibited by a means H. Namely, the operating state in which the carbon generated by imperfect combustion is easily adhering to the film of the air-fuel ratio sensor B is detected, whereby the erroneous judgement of the failure judgment is prevented.

Description

【発明の詳細な説明】 〈産業上の利用分野〉 本発明は、内燃機関における空燃比フィードバック制御
系の故障を自己診断する装置に関する。
DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a device for self-diagnosing a failure in an air-fuel ratio feedback control system in an internal combustion engine.

〈従来技術〉 機関のシリンダ内に供給される混合気の空燃比を目標空
燃比(理論空燃比)にフィードバック制御する電子制御
燃料噴射装置を備えた内燃機関においては、燃料噴射弁
に目詰まり或いは燃料噴射弁駆動回路の出力回路の短絡
等の異常を生じると燃料噴射量か適正量から外れて空燃
比か大きく変化し、混合気は稀薄になるか又は過濃とな
る。この場合、機関か停止したり、出力か低下して運転
性が悪化するという問題かあった。
<Prior Art> In an internal combustion engine equipped with an electronically controlled fuel injection device that feedback-controls the air-fuel ratio of the air-fuel mixture supplied into the cylinders of the engine to a target air-fuel ratio (stoichiometric air-fuel ratio), the fuel injection valve is clogged or When an abnormality such as a short circuit in the output circuit of the fuel injection valve drive circuit occurs, the fuel injection amount deviates from the appropriate amount, the air-fuel ratio changes significantly, and the air-fuel mixture becomes lean or rich. In this case, the problem was that the engine would stop or the output would drop, resulting in poor drivability.

かかる問題点を解決するため、空燃比のフィードバック
制御信号に基づいて混合気か稀薄になっているか或いは
過濃となっているかを判断し、それによって空燃比制御
装置か故障しているか否かを判別するようにした自己診
断装置か既に提案されている(特開昭63−10025
5号公報等参照)。
In order to solve this problem, it is determined whether the air-fuel mixture is lean or rich based on the air-fuel ratio feedback control signal, and thereby it can be determined whether the air-fuel ratio control device is malfunctioning. A self-diagnosis device has already been proposed (Japanese Patent Laid-Open No. 63-10025)
(See Publication No. 5, etc.)

〈発明か解決しようとする課題〉 ところで、かかる従来の自己診断装置にあっては、現状
の機関運転状態を診て故障診断を実行する運転条件の判
別は行っているものの、過去の運転履歴による故障診断
への影響は考慮していないため次のような問題かある。
<Problem to be Solved by the Invention> Incidentally, although such conventional self-diagnosis devices examine the current operating state of the engine to determine the operating conditions for performing fault diagnosis, Since the influence on failure diagnosis is not taken into consideration, the following problems may arise.

即ち、1回の運転時間か極端に短く、機関温度か十分に
上昇しないうちに機関の運転を停止するような運転状態
が変電なった場合(例えば車両か工場から出荷され販売
会社に納入されるまでの間)、内燃機関においては拡散
燃焼等の不完全燃焼か発生し易い。その結果、排気中に
発生したカーボンで排気通路に介装された酸素センサ(
空燃比センサ)の皮膜か汚損されることにより、酸素濃
度検出量が実際の量に比較して減少する。該酸素センサ
からの検出信号により、空燃比フィードバック制御系は
空燃比か過濃側にずれているとの把握に基づいて、燃料
噴射量を減少させる方向に制御するため、フィードバッ
ク制御信号としては過a側の信号か連続的に出力される
ことになる。
In other words, if the operation time is extremely short and the operating condition is such that the engine stops operating before the engine temperature rises sufficiently (for example, when the vehicle is shipped from the factory and delivered to the sales company) In the internal combustion engine, incomplete combustion such as diffusion combustion is likely to occur. As a result, the carbon generated in the exhaust gas was removed from the oxygen sensor (
If the film on the air-fuel ratio sensor (air-fuel ratio sensor) becomes contaminated, the detected amount of oxygen concentration decreases compared to the actual amount. Based on the detection signal from the oxygen sensor, the air-fuel ratio feedback control system determines that the air-fuel ratio has deviated to the rich side and controls the fuel injection amount in the direction of decreasing. The signal on the a side will be output continuously.

したかって、空燃比フィードバック制御系は正常に作動
しているにも拘らず、異常と誤判断してしまうことかあ
る。
Therefore, even though the air-fuel ratio feedback control system is operating normally, it may be mistakenly determined to be abnormal.

本発明は、このような従来の問題点に鑑みなされたもの
で、上記のような自己診断に適しない機関状態を見出し
、該機関状態では診断を禁止することにより上記問題点
を解決した内燃機関における空燃比フィードバック制御
系の自己故障診断装置を提供することを目的とする。
The present invention has been made in view of such conventional problems, and provides an internal combustion engine that solves the above problems by finding an engine state unsuitable for self-diagnosis as described above and prohibiting diagnosis in that engine state. An object of the present invention is to provide a self-failure diagnosis device for an air-fuel ratio feedback control system.

〈課題を解決するための手段〉 このため本発明は、第1図に示すように内燃機関の排気
通路に装着された空燃比センサの出力信号に基づいて空
燃比をフィードバック制御する空燃比フィードバック制
御系の故障を自己診断する装置において、前記空燃比フ
ィードバック制御系のフィードバック制御信号に基づい
て故障の有無を判別する故障判別手段と、機関の1回毎
の運転時間を計測する運転時間計測手段と、機関温度を
検出する機関温度検出手段と、前記計測された運転時間
か所定値以下であって、かつ、運転終了時の機関温度が
所定値以下である所定運転状態の頻度を検出する運転頻
度検出手段と、検出された所定運転状態の頻度か所定値
以上であるときに前記故障判別手段による故障判別を禁
止する故障判別禁止手段と、を含んで構成した。
<Means for Solving the Problems> For this reason, the present invention provides air-fuel ratio feedback control for feedback-controlling the air-fuel ratio based on the output signal of an air-fuel ratio sensor installed in the exhaust passage of an internal combustion engine, as shown in FIG. A device for self-diagnosing a system failure, comprising a failure determination means for determining the presence or absence of a failure based on a feedback control signal of the air-fuel ratio feedback control system, and an operation time measurement means for measuring the operation time of the engine each time. , an engine temperature detection means for detecting the engine temperature; and an operation frequency for detecting the frequency of a predetermined operating state in which the measured operating time is less than or equal to a predetermined value and the engine temperature at the end of the operation is less than or equal to the predetermined value. The present invention is configured to include a detection means, and a failure determination prohibition means for prohibiting failure determination by the failure determination means when the frequency of the detected predetermined operating state is equal to or higher than a predetermined value.

〈作用〉 運転時間計測手段により計測される1回の運転時間が所
定値以下であって、かつ、該運転終了時に機関温度検出
手段によって検出される機関温度か所定値以下である運
転状態では、不完全燃焼により発生するカーホンか空燃
比センサの皮膜に付着し易い。
<Function> In an operating state in which the driving time measured by the driving time measuring means is less than a predetermined value and the engine temperature detected by the engine temperature detecting means at the end of the driving is less than the predetermined value, It tends to adhere to the air-fuel ratio sensor film caused by incomplete combustion.

したがって、かかる運転状態の頻度を運転頻度検出手段
によって検出し、該頻度か所定値以上の場合はカーボン
付着により空燃比センサの皮膜の汚損度か大きく、故障
判別を行うと誤判別される可能性かあるため、故障判別
禁止手段により故障判別手段の故障判別を禁止する。
Therefore, if the frequency of such operating conditions is detected by the operating frequency detection means, and if the frequency is greater than a predetermined value, the degree of contamination of the film of the air-fuel ratio sensor due to carbon adhesion is large, and there is a possibility that the failure will be incorrectly determined. Therefore, the failure determination prohibition means prohibits the failure determination means from making a failure determination.

〈実施例〉 以下に、本発明の実施例を図面に基づいて説明する。<Example> Embodiments of the present invention will be described below based on the drawings.

第2図は本実施例のシステム構成を示し、機関本体10
に接続された吸気マニホールド11には燃料を噴射供給
するインジェクタ12か装着されている。
FIG. 2 shows the system configuration of this embodiment, in which the engine main body 10
An injector 12 for injecting and supplying fuel is attached to the intake manifold 11 connected to the intake manifold 11 .

インジェクタ12より上流側の吸気通路にはスロットル
弁13と更に上流側に吸入空気流量を検出するエアフロ
ーメータI4か装着されている。前記スロットル弁13
には、該スロットル弁13の開度を検出するスロットル
センサ15が装着されている。
A throttle valve 13 is installed in the intake passage upstream of the injector 12, and an air flow meter I4 for detecting the intake air flow rate is installed further upstream. The throttle valve 13
A throttle sensor 15 for detecting the opening degree of the throttle valve 13 is attached to the throttle valve 13 .

一方、排気マニホールド16には、排気中の酸素濃度等
の検出によって空燃比を検出する空燃比センサ17か装
着されている。また、機関本体10には、機関温度の代
表として水温を検出する機関温度検出手段としての水温
センサ18が装着されている。
On the other hand, the exhaust manifold 16 is equipped with an air-fuel ratio sensor 17 that detects the air-fuel ratio by detecting oxygen concentration in the exhaust gas. Further, a water temperature sensor 18 is attached to the engine body 10 as an engine temperature detection means for detecting water temperature as a representative of the engine temperature.

その他、機関回転数を検出する回転数センサ19、スタ
ータスイッチ20を備える。
In addition, a rotation speed sensor 19 for detecting the engine rotation speed and a starter switch 20 are provided.

空燃比フィードバック制御を行う電子制御ユニット50
は、デジタルコンピュータからなり、双方向性バス51
によってデータを相互伝送可能に接続されたROM(リ
ードオンリーメモリ)52、RAM(ランダムアクセス
メモリ)53、CPU (マイクロプロセッサ)54、
入力ポート55及び出力ポート56を具備する。入力ポ
ート55には、前記スロットルセンサ15.空燃比セン
サ17.水温センサ18゜回転数センサ19.スタータ
スイッチ20からの各検出信号が入力される。そして、
CPU54は、前記各検出信号に基づいて運転状態に応
じた燃料噴射量を演算し、該燃料噴射量に見合ったパル
ス幅を有する燃料噴射信号を出力ポート56から前記イ
ンジェクタ12に出力する。これにより、インジェクタ
12を通電駆動し、演算された量の燃料を噴射供給する
。ここで、前記燃料噴射量の演算は、吸入空気流量Qと
機関回転数Nとに基づいて演算した基本燃料噴射量T、
(=Q/N)を、水温Twにより補正する一方、所定の
運転条件では後述するように、空燃比センサ17により
検出された空燃比を目標空燃比(理論空燃比)とすべく
比例積分制御により設定されたフィードバック補正量α
により補正して行う。
Electronic control unit 50 that performs air-fuel ratio feedback control
consists of a digital computer and has a bidirectional bus 51.
ROM (read only memory) 52, RAM (random access memory) 53, CPU (microprocessor) 54, which are connected to each other so that data can be transmitted between them.
It has an input port 55 and an output port 56. The input port 55 has the throttle sensor 15. Air fuel ratio sensor 17. Water temperature sensor 18° rotation speed sensor 19. Each detection signal from the starter switch 20 is input. and,
The CPU 54 calculates a fuel injection amount according to the operating state based on each of the detection signals, and outputs a fuel injection signal having a pulse width commensurate with the fuel injection amount from the output port 56 to the injector 12. Thereby, the injector 12 is energized and driven to inject and supply the calculated amount of fuel. Here, the calculation of the fuel injection amount is based on the basic fuel injection amount T calculated based on the intake air flow rate Q and the engine speed N,
(=Q/N) is corrected by the water temperature Tw, while under predetermined operating conditions, as will be described later, proportional-integral control is performed to make the air-fuel ratio detected by the air-fuel ratio sensor 17 the target air-fuel ratio (theoretical air-fuel ratio). Feedback correction amount α set by
Corrected by

第3図は、空燃比センサ17の出力電圧Vの変化を示し
、混合気か過濃(リッチ)なときは、0.9(V)程度
の出力電圧を発生し、混合気か稀薄(リーン)なときは
、0.1  (V)程度の出力電圧を発生する。該空燃
比センサ17の出力電圧Vは、CPU54において0.
5  (V)程度の基準電圧vFと比較され、出力電圧
■が基準電圧V、よりも高ければリッチであると判断さ
れ、vFよりも低ければリーンであると判断される。
Figure 3 shows changes in the output voltage V of the air-fuel ratio sensor 17. When the air-fuel mixture is rich, an output voltage of about 0.9 (V) is generated, and when the air-fuel mixture is lean, it generates an output voltage of about 0.9 (V). ), an output voltage of about 0.1 (V) is generated. The output voltage V of the air-fuel ratio sensor 17 is set to 0.
It is compared with a reference voltage vF of about 5 (V), and if the output voltage (2) is higher than the reference voltage V, it is determined to be rich, and if it is lower than vF, it is determined to be lean.

第4図は、前記リッチ、リーンの判断に基づいて行われ
るフィードバック補正量αの演算ルーチンを示す。この
ルーチンは所定時間間隔毎、例えば4ms毎に実行され
る。
FIG. 4 shows a calculation routine for the feedback correction amount α, which is performed based on the rich/lean judgment. This routine is executed at predetermined time intervals, for example every 4 ms.

ステップ60で空燃比のリッチ、リーン判別を行い、リ
ーンと判定されたときはステップ61に進んで前回の処
理サイクルから今回の処理サイクルの間に、リッチから
リーンに反転したか否かを判別する。
In step 60, the air-fuel ratio is determined to be rich or lean, and when it is determined to be lean, the process proceeds to step 61, where it is determined whether or not it has changed from rich to lean between the previous processing cycle and the current processing cycle. .

反転していれば、ステップ62に進み、αに所定の比例
分Pか加算され、反転していなければステップ63へ進
んてαに積分分■か加算される。
If it is inverted, the process proceeds to step 62, where a predetermined proportional amount P is added to α, and if it is not inverted, the process proceeds to step 63, where an integral value (2) is added to α.

一方、ステップ60てリッチと判定されたときには、ス
テップ64へ進んて前回の処理サイクルから今回の処理
サイクルの間にリーンからリッチに反転したか否かを判
別する。反転していればステップ65へ進んてαから比
例分Pか減算され、反転していなければステップ66へ
進んてαに積分分■か減算される。
On the other hand, when it is determined in step 60 that the oil is rich, the process proceeds to step 64, where it is determined whether or not there has been an inversion from lean to rich between the previous processing cycle and the current processing cycle. If it is inverted, the process proceeds to step 65, where the proportional portion P is subtracted from α; if it is not inverted, the process proceeds to step 66, where the integral value (2) is subtracted from α.

したがって、αは第3図に示すようにリッチからリーン
へ反転したときには、急激に比例分Pだけ増大した後に
積分分Iずつ徐々に増大し、り一ンからリッチへ反転し
たときには急激に比例分Pだけ減少した後に積分分■ず
つ徐々に減少する。
Therefore, as shown in Fig. 3, when α is reversed from rich to lean, α rapidly increases by a proportional amount P, and then gradually increases by an integral integral I, and when reversed from lean to rich, α suddenly increases by a proportional amount After decreasing by P, it gradually decreases by integral ■.

また、通常フィードバック補正量αは第3図に示すよう
に、設定された上限値MAXと下限値MINとの間にあ
って、空燃比センサ17がリッチ。
Further, as shown in FIG. 3, the normal feedback correction amount α is between the set upper limit value MAX and lower limit value MIN, and the air-fuel ratio sensor 17 is rich.

リーンの検出を周期的に繰り返すため上下動する。It moves up and down to periodically repeat lean detection.

しかしながら、何らかの原因により混合気がリッチにな
り続けた場合はMINに達し、リーンになり続けた場合
はMAXに達する。したがって、αかMAXとなったか
、或いはMINとなったかによって空燃比フィードバッ
ク制御系の故障を診断することかできる。但し、それた
けでは、前述のように故障診断を行うことか不適切であ
る場合にも診断か行われてしまうため、本発明ではかか
る場合か起こる運転条件を検出して該条件では診断を禁
止する。
However, if the air-fuel mixture continues to become rich for some reason, it reaches MIN, and if it continues to become lean, it reaches MAX. Therefore, it is possible to diagnose a failure in the air-fuel ratio feedback control system depending on whether α has reached MAX or MIN. However, if this is the case, failure diagnosis will be performed even if it is inappropriate as described above, so the present invention detects the operating conditions that occur in such cases and prohibits diagnosis under those conditions. do.

第5図及び第6図はCPU54によって行われる本発明
に係る故障診断のための制御ルーチンを示す。これらル
ーチンは一定時間毎の割込によって実行される。
5 and 6 show a control routine for fault diagnosis according to the present invention performed by the CPU 54. FIG. These routines are executed by interrupts at fixed time intervals.

第5図において、ステップ70てはスタータスイッチ2
0のオン、オフか判別され、オフである場合はステップ
71へ進み、前回の処理サイクルから今回の処理サイク
ルの間にスタータスイッチ20がオンからオフに切り換
えられたか否かを判別する。
In FIG. 5, step 70 is the starter switch 2.
0 is on or off, and if it is off, the process proceeds to step 71, where it is determined whether the starter switch 20 was switched from on to off between the previous processing cycle and the current processing cycle.

そして、オンからオフに切り換えられたと判定された場
合はステップ72へ進み、機関回転数Nを所定値例えば
500rpmと比較し、N≧500のときは機関か始動
して回転していると判定してステップ73へ進む。
If it is determined that the switch has been made from on to off, the process proceeds to step 72, where the engine speed N is compared with a predetermined value, for example 500 rpm, and if N≧500, it is determined that the engine has started and is rotating. Then proceed to step 73.

また、ステップ70てスタータスイッチ20かオンと判
定されたとき、ステップ71てスタータスイッチ20か
ONからOFFに切り換えられた直後てないと判定され
たとき、ステップ72て機関回転数N〈500と判定さ
れたときのいずれかの場合は、このルーチンを終了する
Further, when it is determined in step 70 that the starter switch 20 is on, when it is determined in step 71 that the starter switch 20 is not turned on immediately after being switched from ON to OFF, in step 72 it is determined that the engine speed N<500. In either case, exit this routine.

ステップ73て、機関始動後の経過時間を測定するタイ
マをセットした後ステップ74へ進み、機関回転数Nか
0となったか否か、つまり始動後に機関か停止されたか
否かを判別し、停止されていない間はこのステップ73
の判定を繰り返して停止を待つ。
In step 73, a timer is set to measure the elapsed time after the engine is started, and the process proceeds to step 74, in which it is determined whether the engine rotation speed N has become 0, that is, whether the engine has been stopped after starting, and then stopped. This step 73
Repeat the judgment and wait for the stop.

そして、機関か停止されるとステップ75に進んで、前
記タイマの測定値により始動後一定時間を経過している
か否かを判別し、経過していると判定されたときにはス
テップ78へ進み、後述するルーチンにより故障診断の
禁止期間を設定するための故障診断禁止カウンタをデク
リメント(値をl減らす)する。尚、前記タイマは運転
時間計測手段に相当する。
When the engine is stopped, the process proceeds to step 75, and it is determined based on the measured value of the timer whether a certain period of time has elapsed since the engine was started. The routine decrements (decreases the value by l) a fault diagnosis prohibition counter for setting a fault diagnosis prohibition period. Note that the timer corresponds to a driving time measuring means.

また、ステップ75て始動後一定時間を経過していない
と判定されたときにはステップ76へ進み機関温度を代
表する水温Tか設定値T s e、以下か否かを判別す
る。
If it is determined in step 75 that a certain period of time has not elapsed since the start of the engine, the process proceeds to step 76, where it is determined whether the water temperature T, which represents the engine temperature, is less than or equal to the set value Tse.

T≦T、6.と判定されたときにはステップ77へ進ん
で前記故障診断禁止カウンタをインクリメント(値を1
増やす)し、TNT、。1と判定されたときにはステッ
プ78へ進んで故障診断禁止カウンタをデクリメントす
る。
T≦T, 6. If it is determined that
increase) and TNT. If it is determined to be 1, the process advances to step 78 and the failure diagnosis prohibition counter is decremented.

つまり、このルーチンでは1回の運転時間か短く、かつ
、停止直後の水温か低温であるような運転かなされる毎
に故障診断禁止期間を増大し、上記以外の運転かなされ
る毎に故障診断禁止期間を減少させる。ここで、前記故
障診断禁止期間を増大させる運転は、水温か低い状態て
運転されるため不完全燃焼により発生したカーホンか空
燃比センサ17に付着し、そのまま運転を停止するのて
除去されず、かかる運転か繰り返されると付着したカー
ホンか堆積することとなる。一方、それ以外の運転では
運転終了までに水温か上かりカーホンの発生か停止する
と共に、排気温度か上昇して高温の排気により空燃比セ
ンサ17に付着したカーボンか焼き切られる。したかっ
て、これら運転回数の差として計測される故障診断禁止
カウンタのカウント値Cは空燃比センサの皮膜のカーホ
ンによる汚損度の指標となる。一方、前記カウント値C
は、前記カーホンか付着する運転の頻度に相当する値の
指標でもあるので、故障診断禁止カウンタは運転頻度検
出手段に相当する。
In other words, in this routine, the failure diagnosis prohibition period is increased each time a single operation is performed for a short time and the water temperature is low immediately after stopping, and the failure diagnosis is performed each time an operation other than the above is performed. Reduce the period of ban. Here, in the operation that increases the failure diagnosis prohibition period, because the water temperature is low, carphone generated due to incomplete combustion adheres to the air-fuel ratio sensor 17, and is not removed because the operation is stopped. If such operation is repeated, the attached carphone will accumulate. On the other hand, in other operations, the water temperature rises until the end of the operation, causing the car horn to occur or stop, and at the same time, the exhaust temperature rises and the carbon attached to the air-fuel ratio sensor 17 is burned off by the high-temperature exhaust gas. Therefore, the count value C of the failure diagnosis prohibition counter, which is measured as the difference between the number of times of operation, is an index of the degree of contamination of the film of the air-fuel ratio sensor by the car horn. On the other hand, the count value C
is also an index of a value corresponding to the frequency of driving in which the car phone sticks, so the failure diagnosis prohibition counter corresponds to driving frequency detection means.

第6図は、故障診断ルーチンを示す。FIG. 6 shows a fault diagnosis routine.

ステップ80ては前記第4図のルーチンで計測される故
障診断禁止カウンタのカウント値Cを設定値C8,1と
比較する。
In step 80, the count value C of the failure diagnosis prohibition counter measured in the routine shown in FIG. 4 is compared with the set value C8,1.

そして、C<C,。1であるときは、空燃比センサ17
のカーホンによる汚損度は小さく、故障診断を実行して
差し支えないと判断して、ステップ81へ進むか、C2
O4゜、であるときは汚損度か大きく故障診断を行うと
誤診断を行う可能性かあると判断して診断を行うことな
く、このルーチンを終了する。このステップ81により
C≧C8゜1であるときに故障診断を禁止する機能か、
故障判別禁止手段に相当する。
And C<C,. 1, the air-fuel ratio sensor 17
Since the degree of contamination caused by the car phone is small, it is determined that it is safe to perform a failure diagnosis, and the process proceeds to step 81, or the process proceeds to step C2.
When the degree of contamination is 04°, it is determined that the degree of contamination is large and there is a possibility of erroneous diagnosis if failure diagnosis is performed, and this routine is terminated without performing diagnosis. Is this step 81 a function that prohibits failure diagnosis when C≧C8゜1?
This corresponds to a failure determination prohibition means.

ステップ81ては、現在の運転状態か空燃比制御系の故
障診断領域であるか否かを判別し、該領域てないときは
このルーチンを終了する。ここで故障診断領域としては
、空燃比フィードバック制御系の診断であるため、該フ
ィードバック制御中であることは当然であるか、機関の
始動時や暖機時おける燃料噴射量の増量中等過渡的な領
域は避け、定常的な領域か選択される。
In step 81, it is determined whether the current operating state is in the failure diagnosis range of the air-fuel ratio control system, and if it is not in the range, this routine is ended. Since the fault diagnosis area here is the diagnosis of the air-fuel ratio feedback control system, it is natural that the feedback control is in progress, or transient conditions such as an increase in the amount of fuel injection at engine startup or warm-up. Areas are avoided and stationary areas are selected.

故障診断領域であると判定されたときは、ステップ82
以降へ進んで故障診断を行う。
If it is determined that the area is in the failure diagnosis area, step 82
Proceed to the following steps to perform fault diagnosis.

まず、ステップ82てはフィードバック補正量αか第3
図で示した上限値MA X、下限値MINに対しMIN
<α<MAXの範囲にあるか否かを判別する。
First, in step 82, the feedback correction amount α is
MIN for the upper limit value MAX and lower limit value MIN shown in the diagram.
It is determined whether or not it is in the range <α<MAX.

MIN<α<MAXの範囲にある場合は、空燃比フィー
ドバック制細系は正常であると判断してステップ85へ
進み、故障フラグFαを0にリセットする。
If it is within the range of MIN<α<MAX, it is determined that the air-fuel ratio feedback restriction system is normal, and the process proceeds to step 85, where the failure flag Fα is reset to 0.

一方、MIN<α〈〜fAXの範囲外と判定されたとき
、つまりα≦MINであるリーン異常状態或いはα≧M
AXであるリッチ異常状態のいずれかであると判定され
たときには、ステップ83へ進み、これらの異常状態か
過渡的てな(所定時間例えば10秒間以上継続して生じ
ているか否かを判別する。
On the other hand, when it is determined that MIN<α<~fAX is outside the range, that is, in a lean abnormal state where α≦MIN or α≧M
If it is determined that one of the rich abnormal states AX is present, the process proceeds to step 83, where it is determined whether these abnormal states are transient (for example, 10 seconds or longer).

そして、異常状態か10秒間以上継続している場合は、
空燃比フィードバック制御系が故障していると判断して
ステップ84へ進み、故障フラグFαを1にセットする
If the abnormal condition continues for more than 10 seconds,
It is determined that the air-fuel ratio feedback control system has failed, and the process proceeds to step 84, where the failure flag Fα is set to 1.

このようにして故障フラグFαの値により故障の有無が
示される。尚、ステップ82〜ステツプ85の機能か故
障判別手段に相当する。
In this way, the presence or absence of a failure is indicated by the value of the failure flag Fα. Note that the functions of steps 82 to 85 correspond to failure determination means.

かかる構成とすれば、空燃比センサ17の皮膜がカーボ
ンにより汚損され、故障を誤診断する可能性がある状態
では故障診断が禁止されるため、診断精度か向上する。
With this configuration, failure diagnosis is prohibited in a state where the film of the air-fuel ratio sensor 17 is contaminated with carbon and there is a possibility of erroneously diagnosing a failure, thereby improving diagnostic accuracy.

〈発明の効果〉 以上説明したように本発明によれは、空燃比センサの皮
膜のカーボンによる汚損度か高くなる条件を検出し、該
検出時には空燃比フィードバック制御系の故障診断を禁
止する構成としたため、上記状況での誤診を防止てき自
己診断精度か向上する。
<Effects of the Invention> As explained above, the present invention has a configuration that detects conditions in which the degree of carbon contamination of the film of the air-fuel ratio sensor becomes high, and prohibits failure diagnosis of the air-fuel ratio feedback control system when the condition is detected. This prevents misdiagnosis in the above situations and improves self-diagnosis accuracy.

【図面の簡単な説明】[Brief explanation of the drawing]

第1図は本発明の構成を示すブロック図、第2図は本発
明の一実施例のシステム構成図、第3図は空燃比センサ
の出力電圧とフィードバック補正量との関係を示す線図
、第4図は同上のフィードバック補正量の設定ルーチン
を示すフローチャート、第5図は同じく故障診断禁止期
間の設定ルーチンを示すフローチャート、第6図は同じ
く故障診断ルーチンを示すフローチャートである。 12・・・インジェクタ  16・・・排気マニホール
ド17・・・空燃比センサ  I8・・・水温センサ 
 19・・・回転数センサ  20・・・スタータスイ
ッチ  50・・・電子制御ユニット 第1図 第3図 第5図 第6図
FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system configuration diagram of an embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between the output voltage of the air-fuel ratio sensor and the feedback correction amount. FIG. 4 is a flowchart showing a routine for setting the feedback correction amount, FIG. 5 is a flowchart showing a routine for setting a fault diagnosis prohibition period, and FIG. 6 is a flowchart showing a fault diagnosis routine. 12... Injector 16... Exhaust manifold 17... Air-fuel ratio sensor I8... Water temperature sensor
19... Rotation speed sensor 20... Starter switch 50... Electronic control unit Fig. 1 Fig. 3 Fig. 5 Fig. 6

Claims (1)

【特許請求の範囲】[Claims] 内燃機関の排気通路に装着された空燃比センサの出力信
号に基づいて空燃比をフィードバック制御する空燃比フ
ィードバック制御系の故障を自己診断する装置において
、前記空燃比フィードバック制御系のフィードバック制
御信号に基づいて故障の有無を判別する故障判別手段と
、機関の1回毎の運転時間を計測する運転時間計測手段
と、機関温度を検出する機関温度検出手段と、前記計測
された運転時間が所定値以下であって、かつ、運転終了
時の機関温度が所定値以下である所定運転状態の頻度を
検出する運転頻度検出手段と、検出された所定運転状態
の頻度が所定値以上であるときに前記故障判別手段によ
る故障判別を禁止する故障判別禁止手段と、を含んで構
成したことを特徴とする内燃機関の空燃比フィードバッ
ク制御系の自己診断装置。
In a device for self-diagnosing a failure of an air-fuel ratio feedback control system that performs feedback control of an air-fuel ratio based on an output signal of an air-fuel ratio sensor installed in an exhaust passage of an internal combustion engine, the system comprises: a failure determining means for determining the presence or absence of a failure; an operating time measuring means for measuring the operating time of the engine each time; an engine temperature detecting means for detecting the engine temperature; and an operating frequency detection means for detecting the frequency of a predetermined operating state in which the engine temperature at the end of the operation is below a predetermined value; 1. A self-diagnosis device for an air-fuel ratio feedback control system of an internal combustion engine, comprising: a failure determination prohibition means for prohibiting failure determination by the determination means.
JP31620590A 1990-11-22 1990-11-22 Self-diagnostic device of air-fuel ratio feedback control system in internal combustion engine Pending JPH04191440A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP31620590A JPH04191440A (en) 1990-11-22 1990-11-22 Self-diagnostic device of air-fuel ratio feedback control system in internal combustion engine

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP31620590A JPH04191440A (en) 1990-11-22 1990-11-22 Self-diagnostic device of air-fuel ratio feedback control system in internal combustion engine

Publications (1)

Publication Number Publication Date
JPH04191440A true JPH04191440A (en) 1992-07-09

Family

ID=18074472

Family Applications (1)

Application Number Title Priority Date Filing Date
JP31620590A Pending JPH04191440A (en) 1990-11-22 1990-11-22 Self-diagnostic device of air-fuel ratio feedback control system in internal combustion engine

Country Status (1)

Country Link
JP (1) JPH04191440A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08189402A (en) * 1995-01-11 1996-07-23 Mazda Motor Corp Self-diagnostic device in engine air-fuel ratio controller
JP2002073174A (en) * 2000-08-29 2002-03-12 Mitsubishi Electric Corp Automatic controller for coke moving machine

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08189402A (en) * 1995-01-11 1996-07-23 Mazda Motor Corp Self-diagnostic device in engine air-fuel ratio controller
JP2002073174A (en) * 2000-08-29 2002-03-12 Mitsubishi Electric Corp Automatic controller for coke moving machine

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