JP2013092155A - Air-fuel ratio control device for internal combustion engine - Google Patents

Air-fuel ratio control device for internal combustion engine Download PDF

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JP2013092155A
JP2013092155A JP2013003087A JP2013003087A JP2013092155A JP 2013092155 A JP2013092155 A JP 2013092155A JP 2013003087 A JP2013003087 A JP 2013003087A JP 2013003087 A JP2013003087 A JP 2013003087A JP 2013092155 A JP2013092155 A JP 2013092155A
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fuel ratio
heater
ratio sensor
temperature
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JP5376073B2 (en
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Hideyuki Suzuki
秀幸 鈴木
Tamiichi Kimura
民一 木村
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Nissan Motor Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To properly maintain an element temperature of a second air-fuel ratio sensor 13 by simplified energization control of a second heater 15 without directly detecting the element temperature of the second air-fuel ratio sensor 13 at a downstream side.SOLUTION: An air-fuel ratio control device includes a first air-fuel ratio sensor 12 at a pre-catalyst device 10 upstream side and a second air-fuel ratio sensor 13 at a downstream side in an exhaust passage 9 of an internal combustion engine 1, wherein the sensors are provided with a first heater 14 and a second heater 15, respectively. For the first air-fuel ratio sensor 12 at the upstream side, the element temperature is detected, and an ON duty ratio for the first heater 14 is feedback controlled so that a detection temperature is within a predetermined temperature range T1. In contrast, for the second air-fuel ratio sensor 13 at the downstream side, a parameter of the feedback control of the first heater 14, e.g., the ON duty ratio or the element temperature is diverted to simply control the ON duty ratio of the second heater 15.

Description

この発明は、排気通路における触媒装置の上流側および下流側に各々空燃比センサ（いわゆる広域型空燃比センサあるいは酸素センサ）を備えた内燃機関の空燃比制御装置に関し、特に、下流側の空燃比センサの温度制御の改良に関する。   The present invention relates to an air-fuel ratio control device for an internal combustion engine provided with air-fuel ratio sensors (so-called wide-range air-fuel ratio sensors or oxygen sensors) on the upstream side and downstream side of a catalyst device in an exhaust passage, and in particular, on the downstream side It relates to the improvement of temperature control of the sensor.

いわゆる排気空燃比を検出するための空燃比センサには、特許文献１に記載されているように、温度によって出力が変化する温度特性があり、従って、精度よく空燃比制御を達成するために、空燃比センサにヒータを付設し、所定の温度範囲に素子温度を維持することが広くなされている。   As described in Patent Document 1, the air-fuel ratio sensor for detecting the so-called exhaust air-fuel ratio has a temperature characteristic in which the output changes depending on the temperature. Therefore, in order to achieve the air-fuel ratio control with high accuracy, A heater is attached to the air-fuel ratio sensor to maintain the element temperature within a predetermined temperature range.

また、触媒装置の上流側および下流側に各々空燃比センサを設けた空燃比制御装置が公知であるが、この種の構成においては、コスト低減のために、上流側の空燃比センサのヒータのみを高精度にフィードバック制御し、下流側の空燃比センサのヒータは、機関運転条件などから単純にオープンループ制御するのが一般的である。   Also, an air-fuel ratio control device is known in which air-fuel ratio sensors are provided on the upstream side and downstream side of the catalyst device respectively. However, in this type of configuration, only the heater of the upstream air-fuel ratio sensor is used for cost reduction. In general, the heater of the downstream air-fuel ratio sensor is simply open-loop controlled based on engine operating conditions.

特開昭６３−１２８５５号公報JP-A 63-12855

しかしながら、上記のように下流側の空燃比センサの温度補償を行わない場合には、それだけ空燃比制御の誤差が大きく生じ得る。なお下流側の空燃比センサについても、素子温度の検出に基づいてヒータのフィードバック制御を行うようにすると、コストの上昇を伴う。   However, when the temperature compensation of the downstream air-fuel ratio sensor is not performed as described above, an error in the air-fuel ratio control can be greatly increased. The downstream air-fuel ratio sensor is also associated with an increase in cost if the heater feedback control is performed based on the detection of the element temperature.

この発明は、内燃機関の排気通路において触媒装置の上流側に配置された第１空燃比センサと、この第１空燃比センサに付設された第１ヒータと、触媒装置の下流側に配置された第２空燃比センサと、この第２空燃比センサに付設された第２ヒータと、上記第１空燃比センサの素子温度の検出に基づいて該素子温度が所定温度となるように上記第１ヒータの通電をフィードバック制御する第１ヒータ制御手段と、を備えた内燃機関の空燃比制御装置を前提としている。そして、上記第１ヒータ制御手段による第１ヒータの通電制御に相関して上記第２ヒータの通電を制御することを特徴としている。   According to the present invention, a first air-fuel ratio sensor disposed upstream of a catalyst device in an exhaust passage of an internal combustion engine, a first heater attached to the first air-fuel ratio sensor, and a downstream side of the catalyst device A second air-fuel ratio sensor, a second heater attached to the second air-fuel ratio sensor, and the first heater so that the element temperature becomes a predetermined temperature based on detection of the element temperature of the first air-fuel ratio sensor. And an air-fuel ratio control apparatus for an internal combustion engine provided with a first heater control means for feedback-controlling the energization of the internal combustion engine. Then, the energization of the second heater is controlled in correlation with the energization control of the first heater by the first heater control means.

第１空燃比センサの第１ヒータは、第１空燃比センサの素子温度の検出に基づいて、その通電がフィードバック制御されるので、例えば排気温度が低ければ通電量が大となるように制御され、逆に排気温度が高くなれば、通電量が小となるように制御される。従って、例えば、このフィードバック制御に用いられるヒータの制御デューティ比は、ヒータを具備しない場合の第１空燃比センサの温度条件を示し、ひいては、その下流に位置する第２空燃比センサの温度条件や排気温度を代替的に示す。さらに、ヒータの通電に対し空燃比センサの素子温度の変化は応答遅れを有し、温度制御の上で、この応答遅れの影響は大きなものとなるが、第１ヒータの通電制御は、フィードバック制御によりこの応答遅れを含んだものとなる。そして、ヒータの通電に対する温度変化の応答は、２つの空燃比センサで同等であるとみなすことができる。従って、フィードバック制御される第１ヒータの通電制御に相関した形で第２ヒータの通電を制御することで、簡易的に第２空燃比センサの温度制御を実現できる。   The first heater of the first air-fuel ratio sensor is feedback-controlled based on the detection of the element temperature of the first air-fuel ratio sensor. For example, if the exhaust gas temperature is low, the amount of power supply is controlled to be large. Conversely, when the exhaust gas temperature becomes high, the energization amount is controlled to be small. Therefore, for example, the control duty ratio of the heater used for this feedback control indicates the temperature condition of the first air-fuel ratio sensor when the heater is not provided, and as a result, the temperature condition of the second air-fuel ratio sensor located downstream thereof, The exhaust temperature is shown as an alternative. Furthermore, the change in the element temperature of the air-fuel ratio sensor with respect to the heater energization has a response delay, and the influence of this response delay is significant on the temperature control. However, the energization control of the first heater is a feedback control. Therefore, this response delay is included. And the response of the temperature change with respect to electricity supply of a heater can be considered that two air-fuel ratio sensors are equivalent. Therefore, the temperature control of the second air-fuel ratio sensor can be easily realized by controlling the energization of the second heater in a manner correlated with the energization control of the first heater that is feedback controlled.

この発明によれば、第２空燃比センサの素子温度を直接に検出することなく第１空燃比センサの素子温度に基づくフィードバック制御を利用して、第２空燃比センサの第２ヒータの通電をより精度良く制御でき、第２空燃比センサの素子温度を所望の温度範囲に維持することが可能となる。   According to the present invention, the second heater of the second air-fuel ratio sensor is energized using the feedback control based on the element temperature of the first air-fuel ratio sensor without directly detecting the element temperature of the second air-fuel ratio sensor. Control can be performed with higher accuracy, and the element temperature of the second air-fuel ratio sensor can be maintained in a desired temperature range.

この発明に係る空燃比制御装置の構成を示す構成説明図。BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing which shows the structure of the air fuel ratio control apparatus which concerns on this invention. 空燃比センサの温度特性を示す特性図。The characteristic view which shows the temperature characteristic of an air fuel ratio sensor. 第１実施例の制御の流れを示すフローチャート。The flowchart which shows the flow of control of 1st Example. 第２実施例の制御の流れを示すフローチャート。The flowchart which shows the flow of control of 2nd Example. 第３実施例の制御の流れを示すフローチャート。The flowchart which shows the flow of control of 3rd Example. 第４実施例の制御の流れを示すフローチャート。The flowchart which shows the flow of control of 4th Example.

図１は、この発明に係る空燃比制御装置のシステム構成を概略的に示しており、ガソリン機関である内燃機関１は、ピストン２により形成される燃焼室３に点火プラグ４を備えるとともに、吸気通路５の吸気弁直前に燃料噴射弁６を備え、かつ吸入空気量を検出するエアフロメータ７およびスロットル弁８を吸気通路５に備えている。また、排気通路９には、比較的容量の小さな上流側のプリ触媒装置１０と比較的容量の大きな下流側のメイン触媒装置１１とが介装されている。上記プリ触媒装置１０は、例えば排気マニホルドの出口部に装着され、上記メイン触媒装置１１は、例えば車両の床下に配置されている。そして、プリ触媒装置１０の上流側には第１空燃比センサ１２が配置され、プリ触媒装置１０の下流側つまりプリ触媒装置１０とメイン触媒装置１１との間には第２空燃比センサ１３が配置されている。   FIG. 1 schematically shows a system configuration of an air-fuel ratio control apparatus according to the present invention. An internal combustion engine 1 which is a gasoline engine includes a spark plug 4 in a combustion chamber 3 formed by a piston 2 and an intake air. A fuel injection valve 6 is provided immediately before the intake valve in the passage 5, and an air flow meter 7 and a throttle valve 8 for detecting the intake air amount are provided in the intake passage 5. The exhaust passage 9 is provided with an upstream pre-catalyst device 10 having a relatively small capacity and a downstream main catalyst device 11 having a relatively large capacity. The pre-catalyst device 10 is mounted, for example, at an outlet of an exhaust manifold, and the main catalyst device 11 is disposed, for example, under the floor of a vehicle. A first air-fuel ratio sensor 12 is disposed upstream of the pre-catalyst device 10, and a second air-fuel ratio sensor 13 is disposed downstream of the pre-catalyst device 10, that is, between the pre-catalyst device 10 and the main catalyst device 11. Has been placed.

これらの２つの空燃比センサ１２，１３は、いわゆる広域型空燃比センサあるいは出力がステップ的に変化する酸素センサのいずれであってもよいが、この実施例では、２つの空燃比センサ１２，１３の双方が酸素センサからなる。そして、これらの空燃比センサ１２，１３は、その素子を加熱するセラミックスヒータ等のヒータを各々備えている。ここでは、第１空燃比センサ１２のヒータを第１ヒータ１４とし、第２空燃比センサ１３のヒータを第２ヒータ１５とする。これらのヒータ１４，１５は、その通電量が、ＯＮデューティ比の可変制御によって制御される。   These two air-fuel ratio sensors 12 and 13 may be either a so-called wide-area type air-fuel ratio sensor or an oxygen sensor whose output changes stepwise. In this embodiment, the two air-fuel ratio sensors 12 and 13 are used. Both consist of oxygen sensors. These air-fuel ratio sensors 12 and 13 are each provided with a heater such as a ceramic heater for heating the element. Here, the heater of the first air-fuel ratio sensor 12 is the first heater 14, and the heater of the second air-fuel ratio sensor 13 is the second heater 15. The energization amounts of these heaters 14 and 15 are controlled by variable control of the ON duty ratio.

これらの２つの空燃比センサ１２，１３を用いた空燃比制御そのものは本発明の要部ではないので、その詳しい説明は省略するが、コントロールユニット１６において、公知の種々の態様で２つの空燃比センサ１２，１３の検出信号が利用される。例えば、上流側の第１空燃比センサ１２の検出信号を主に用いて燃料噴射量をフィードバック制御するとともに、下流側の第２空燃比センサ１３の検出信号を、そのフィードバック制御の片寄りの学習補正や触媒の劣化判定等に利用する、等の制御がなされる。   The air-fuel ratio control itself using these two air-fuel ratio sensors 12 and 13 is not a main part of the present invention, and thus detailed description thereof will be omitted. However, in the control unit 16, the two air-fuel ratios are known in various known modes. Detection signals of the sensors 12 and 13 are used. For example, the fuel injection amount is feedback-controlled mainly using the detection signal of the upstream first air-fuel ratio sensor 12, and the detection signal of the downstream second air-fuel ratio sensor 13 is learned in the vicinity of the feedback control. Controls such as correction and determination of catalyst deterioration are performed.

上記の空燃比センサ１２，１３においては、例えば図２に例示するような温度特性があり、排気空燃比に対する正しい出力を得るためには、ある温度範囲Ｔ１（例えば６００℃〜６５０℃の範囲）に素子温度を維持する必要がある。   The air-fuel ratio sensors 12 and 13 have temperature characteristics as exemplified in FIG. 2, for example. In order to obtain a correct output with respect to the exhaust air-fuel ratio, a certain temperature range T1 (for example, a range of 600 ° C. to 650 ° C.). It is necessary to maintain the element temperature.

そのため、空燃比制御に主に利用される上流側の第１空燃比センサ１２については、素子温度を例えば熱電対等を用いて検出し、この検出温度が上記の温度範囲Ｔ１内となるように、第１ヒータ１４に対するＯＮデューティ比がフィードバック制御される。   Therefore, for the upstream first air-fuel ratio sensor 12 mainly used for air-fuel ratio control, the element temperature is detected using, for example, a thermocouple, and the detected temperature falls within the temperature range T1. The ON duty ratio for the first heater 14 is feedback controlled.

これに対し、下流側の第２空燃比センサ１３については、上記の第１ヒータ１４のフィードバック制御のパラメータを流用して、第２ヒータ１５のＯＮデューティ比が簡易的に制御される。   On the other hand, for the second air-fuel ratio sensor 13 on the downstream side, the ON duty ratio of the second heater 15 is simply controlled by using the feedback control parameters of the first heater 14 described above.

図３は、この制御の具体的な第１実施例を示すフローチャートであって、まずステップ１で、上流側の第１空燃比センサ（フローチャート中ではＦｒ酸素センサと記す）１２の第１ヒータ１４のＯＮデューティ比を読み込み、ステップ２で、このＯＮデューティ比を用いて、下流側の第２空燃比センサ（フローチャート中ではＲｒ酸素センサと記す）１３の素子温度を推定する。これは下記の論理式による。   FIG. 3 is a flowchart showing a specific first embodiment of this control. First, in step 1, the first heater 14 of the upstream first air-fuel ratio sensor (referred to as Fr oxygen sensor in the flowchart) 12 is shown. In step 2, using this ON duty ratio, the element temperature of the downstream second air-fuel ratio sensor (referred to as Rr oxygen sensor in the flowchart) 13 is estimated. This is based on the following logical expression.

Ｒｒ酸素センサ素子温度＝Ｃ２＋Ｃ１＊ｅｘｐ（−ｔ／τ１）
ここで、Ｃ１およびＣ２は適宜な定数である。「ｅｘｐ（−ｔ／τ１）」は、第１ヒータ１４のＯＮデューティ比の一次応答遅れを表すものであり、τ１は第１ヒータ１４のＯＮデューティ比の時定数である。 Rr oxygen sensor element temperature = C2 + C1 * exp (−t / τ1)
Here, C1 and C2 are appropriate constants. “Exp (−t / τ1)” represents a primary response delay of the ON duty ratio of the first heater 14, and τ1 is a time constant of the ON duty ratio of the first heater 14.

このようにして推定した第２空燃比センサ１３の素子温度を用いて、ステップ３で、第２ヒータ１５のＯＮデューティ比を算出し、ステップ４で、このＯＮデューティ比に沿って第２ヒータ１５の通電を行う。これにより、第２空燃比センサ１３の素子温度が、上述の温度範囲Ｔ１内に維持される。   Using the element temperature of the second air-fuel ratio sensor 13 estimated in this way, the ON duty ratio of the second heater 15 is calculated in step 3, and in step 4, the second heater 15 is adjusted along this ON duty ratio. Turn on the power. Thereby, the element temperature of the 2nd air fuel ratio sensor 13 is maintained in the above-mentioned temperature range T1.

ここで、一つの実施例では、ステップ３で算出したＯＮデューティ比が所定の上限値を越えている場合には、実際に出力するＯＮデューティ比をその上限値に制限するようにしている。そして、ステップ３で算出された要求デューティ比を所定のテーブルを用いて要求熱量に換算し、上限値のＯＮデューティ比での通電による熱量を積算していって、この積算熱量が上記要求熱量に達するまで通電を行う。   Here, in one embodiment, when the ON duty ratio calculated in step 3 exceeds a predetermined upper limit value, the actually output ON duty ratio is limited to the upper limit value. Then, the required duty ratio calculated in step 3 is converted into a required heat amount using a predetermined table, and the heat amount due to energization at the upper limit ON duty ratio is integrated. Energize until it reaches.

次に、図４は、第２ヒータ１５の制御の第２実施例を示すフローチャートであって、ステップ１では、上記と同様に第１空燃比センサ１２の第１ヒータ１４のＯＮデューティ比を読み込むが、ステップ２では、このＯＮデューティ比を用いて、下流側の第２空燃比センサ１３周囲の雰囲気温度つまりプリ触媒装置１０通過後の排気温度を推定する。これは下記の論理式による。   Next, FIG. 4 is a flowchart showing a second embodiment of the control of the second heater 15. In step 1, the ON duty ratio of the first heater 14 of the first air-fuel ratio sensor 12 is read in the same manner as described above. However, in step 2, the ambient temperature around the downstream second air-fuel ratio sensor 13, that is, the exhaust temperature after passing through the pre-catalyst device 10, is estimated using this ON duty ratio. This is based on the following logical expression.

Ｒｒ酸素センサ雰囲気温度＝Ｃ４＋Ｃ３＊ｅｘｐ（−ｔ／τ１）
ここで、Ｃ４およびＣ３は適宜な定数である。上述したように、「ｅｘｐ（−ｔ／τ１）」は、第１ヒータ１４のＯＮデューティ比の一次応答遅れを表しており、τ１は第１ヒータ１４のＯＮデューティ比の時定数である。 Rr oxygen sensor ambient temperature = C4 + C3 * exp (−t / τ1)
Here, C4 and C3 are appropriate constants. As described above, “exp (−t / τ1)” represents the first-order response delay of the ON duty ratio of the first heater 14, and τ1 is the time constant of the ON duty ratio of the first heater 14.

このようにして推定した第２空燃比センサ１３周囲の雰囲気温度を用いて、ステップ３で、第２ヒータ１５のＯＮデューティ比を算出し、ステップ４で、このＯＮデューティ比に沿って第２ヒータ１５の通電を行う。これにより、第２空燃比センサ１３の素子温度が、やはり上述の温度範囲Ｔ１内に維持される。   Using the ambient temperature around the second air-fuel ratio sensor 13 estimated in this way, the ON duty ratio of the second heater 15 is calculated in step 3, and in step 4, the second heater along the ON duty ratio is calculated. 15 is energized. Thereby, the element temperature of the second air-fuel ratio sensor 13 is also maintained within the temperature range T1 described above.

次に、図５は、第２ヒータ１５の制御の第３実施例を示すフローチャートであって、この実施例では、ステップ１で、第１空燃比センサ１２の素子温度を読み込み、ステップ２で、この第１空燃比センサ１２の素子温度を用いて、下流側の第２空燃比センサ１３の素子温度を推定する。これは下記の論理式による。   FIG. 5 is a flowchart showing a third embodiment of the control of the second heater 15. In this embodiment, the element temperature of the first air-fuel ratio sensor 12 is read in step 1, and in step 2, The element temperature of the second air-fuel ratio sensor 13 on the downstream side is estimated using the element temperature of the first air-fuel ratio sensor 12. This is based on the following logical expression.

Ｒｒ酸素センサ素子温度＝Ｃ６＋Ｃ５＊ｅｘｐ（−ｔ／τ２）
ここで、Ｃ５およびＣ６は適宜な定数である。「ｅｘｐ（−ｔ／τ２）」は、第１空燃比センサ１２の素子温度の一次応答遅れを表しており、τ２は第１空燃比センサ１２の素子温度の時定数である。 Rr oxygen sensor element temperature = C6 + C5 * exp (−t / τ2)
Here, C5 and C6 are appropriate constants. “Exp (−t / τ2)” represents a primary response delay of the element temperature of the first air-fuel ratio sensor 12, and τ2 is a time constant of the element temperature of the first air-fuel ratio sensor 12.

このようにして推定した第２空燃比センサ１３の素子温度を用いて、ステップ３で、第２ヒータ１５のＯＮデューティ比を算出し、ステップ４で、このＯＮデューティ比に沿って第２ヒータ１５の通電を行う。これにより、第２空燃比センサ１３の素子温度が、上述の温度範囲Ｔ１内に維持される。   Using the element temperature of the second air-fuel ratio sensor 13 estimated in this way, the ON duty ratio of the second heater 15 is calculated in step 3, and in step 4, the second heater 15 is adjusted along this ON duty ratio. Turn on the power. Thereby, the element temperature of the 2nd air fuel ratio sensor 13 is maintained in the above-mentioned temperature range T1.

次に、図６は、第２ヒータ１５の制御の第４実施例を示すフローチャートであって、ステップ１では、図５と同様に第１空燃比センサ１２の素子温度を読み込むが、ステップ２では、この素子温度を用いて、下流側の第２空燃比センサ１３周囲の雰囲気温度つまりプリ触媒装置１０通過後の排気温度を推定する。これは下記の論理式による。   Next, FIG. 6 is a flowchart showing a fourth embodiment of the control of the second heater 15. In step 1, the element temperature of the first air-fuel ratio sensor 12 is read in the same manner as in FIG. The element temperature is used to estimate the ambient temperature around the second air-fuel ratio sensor 13 on the downstream side, that is, the exhaust temperature after passing through the pre-catalyst device 10. This is based on the following logical expression.

Ｒｒ酸素センサ雰囲気温度＝Ｃ８＋Ｃ７＊ｅｘｐ（−ｔ／τ２）
ここで、Ｃ８およびＣ７は適宜な定数である。上述したように、「ｅｘｐ（−ｔ／τ２）」は、第１空燃比センサ１２の素子温度の一次応答遅れを表しており、τ２は第１空燃比センサ１２の素子温度の時定数である。 Rr oxygen sensor ambient temperature = C8 + C7 * exp (−t / τ2)
Here, C8 and C7 are appropriate constants. As described above, “exp (−t / τ2)” represents the primary response delay of the element temperature of the first air-fuel ratio sensor 12, and τ2 is the time constant of the element temperature of the first air-fuel ratio sensor 12. .

このようにして推定した第２空燃比センサ１３周囲の雰囲気温度を用いて、ステップ３で、第２ヒータ１５のＯＮデューティ比を算出し、ステップ４で、このＯＮデューティ比に沿って第２ヒータ１５の通電を行う。これにより、第２空燃比センサ１３の素子温度が、やはり上述の温度範囲Ｔ１内に維持される。   Using the ambient temperature around the second air-fuel ratio sensor 13 estimated in this way, the ON duty ratio of the second heater 15 is calculated in step 3, and in step 4, the second heater along the ON duty ratio is calculated. 15 is energized. Thereby, the element temperature of the second air-fuel ratio sensor 13 is also maintained within the temperature range T1 described above.

１…内燃機関
９…排気通路
１０…プリ触媒装置
１２…第１空燃比センサ
１３…第２空燃比センサ
１４…第１ヒータ
１５…第２ヒータ
１６…コントロールユニット DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 9 ... Exhaust passage 10 ... Pre catalyst apparatus 12 ... 1st air fuel ratio sensor 13 ... 2nd air fuel ratio sensor 14 ... 1st heater 15 ... 2nd heater 16 ... Control unit

この発明は、排気通路における触媒装置の上流側および下流側に各々空燃比センサ（いわゆる広域型空燃比センサあるいは酸素センサ）を備えた内燃機関の空燃比制御装置に関し、特に、下流側の空燃比センサの温度制御の改良に関する。   The present invention relates to an air-fuel ratio control device for an internal combustion engine provided with air-fuel ratio sensors (so-called wide-range air-fuel ratio sensors or oxygen sensors) on the upstream side and downstream side of a catalyst device in an exhaust passage, and in particular, on the downstream side It relates to the improvement of temperature control of the sensor.

いわゆる排気空燃比を検出するための空燃比センサには、特許文献１に記載されているように、温度によって出力が変化する温度特性があり、従って、精度よく空燃比制御を達成するために、空燃比センサにヒータを付設し、所定の温度範囲に素子温度を維持することが広くなされている。   As described in Patent Document 1, the air-fuel ratio sensor for detecting the so-called exhaust air-fuel ratio has a temperature characteristic in which the output changes depending on the temperature. Therefore, in order to achieve the air-fuel ratio control with high accuracy, A heater is attached to the air-fuel ratio sensor to maintain the element temperature within a predetermined temperature range.

また、触媒装置の上流側および下流側に各々空燃比センサを設けた空燃比制御装置が公知であるが、この種の構成においては、コスト低減のために、上流側の空燃比センサのヒータのみを高精度にフィードバック制御し、下流側の空燃比センサのヒータは、機関運転条件などから単純にオープンループ制御するのが一般的である。   Also, an air-fuel ratio control device is known in which air-fuel ratio sensors are provided on the upstream side and downstream side of the catalyst device respectively. However, in this type of configuration, only the heater of the upstream air-fuel ratio sensor is used for cost reduction. In general, the heater of the downstream air-fuel ratio sensor is simply open-loop controlled based on engine operating conditions.

特開昭６３−１２８５５号公報JP-A 63-12855

しかしながら、上記のように下流側の空燃比センサの温度補償を行わない場合には、それだけ空燃比制御の誤差が大きく生じ得る。なお下流側の空燃比センサについても、素子温度の検出に基づいてヒータのフィードバック制御を行うようにすると、コストの上昇を伴う。   However, when the temperature compensation of the downstream air-fuel ratio sensor is not performed as described above, an error in the air-fuel ratio control can be greatly increased. The downstream air-fuel ratio sensor is also associated with an increase in cost if the heater feedback control is performed based on the detection of the element temperature.

この発明は、内燃機関の排気通路において触媒装置の上流側に配置された第１空燃比センサと、この第１空燃比センサに付設された第１ヒータと、触媒装置の下流側に配置された第２空燃比センサと、この第２空燃比センサに付設された第２ヒータと、上記第１空燃比センサの素子温度の検出に基づいて該素子温度が所定温度となるように上記第１ヒータの通電をフィードバック制御する第１ヒータ制御手段と、を備えた内燃機関の空燃比制御装置を前提としている。そして、検出した第１空燃比センサの素子温度の一次遅れを用いて第２空燃比センサの素子温度を推定し、この推定素子温度に基づき上記第２ヒータを通電制御することを特徴としている。 According to the present invention, a first air-fuel ratio sensor disposed upstream of a catalyst device in an exhaust passage of an internal combustion engine, a first heater attached to the first air-fuel ratio sensor, and a downstream side of the catalyst device A second air-fuel ratio sensor, a second heater attached to the second air-fuel ratio sensor, and the first heater so that the element temperature becomes a predetermined temperature based on detection of the element temperature of the first air-fuel ratio sensor. And an air-fuel ratio control apparatus for an internal combustion engine provided with a first heater control means for feedback-controlling the energization of the internal combustion engine. Then, the element temperature of the second air-fuel ratio sensor is estimated using the first-order delay of the detected element temperature of the first air-fuel ratio sensor, and the second heater is energized and controlled based on the estimated element temperature .

この発明によれば、第２空燃比センサの素子温度を直接に検出することなく第１空燃比センサの素子温度の一次遅れを用いて第２空燃比センサの素子温度を簡易的に推定することで、第２ヒータの通電をより精度良く制御でき、第２空燃比センサの素子温度を所望の温度範囲に維持することが可能となる。 According to the present invention, the element temperature of the second air-fuel ratio sensor can be simply estimated using the primary delay of the element temperature of the first air-fuel ratio sensor without directly detecting the element temperature of the second air-fuel ratio sensor. Thus, the energization of the second heater can be controlled with higher accuracy, and the element temperature of the second air-fuel ratio sensor can be maintained in a desired temperature range.

この発明に係る空燃比制御装置の構成を示す構成説明図。BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing which shows the structure of the air fuel ratio control apparatus which concerns on this invention. 空燃比センサの温度特性を示す特性図。The characteristic view which shows the temperature characteristic of an air fuel ratio sensor. 実施例の制御の流れを示すフローチャート。Flowchart showing a flow of control of the real施例.

図１は、この発明に係る空燃比制御装置のシステム構成を概略的に示しており、ガソリン機関である内燃機関１は、ピストン２により形成される燃焼室３に点火プラグ４を備えるとともに、吸気通路５の吸気弁直前に燃料噴射弁６を備え、かつ吸入空気量を検出するエアフロメータ７およびスロットル弁８を吸気通路５に備えている。また、排気通路９には、比較的容量の小さな上流側のプリ触媒装置１０と比較的容量の大きな下流側のメイン触媒装置１１とが介装されている。上記プリ触媒装置１０は、例えば排気マニホルドの出口部に装着され、上記メイン触媒装置１１は、例えば車両の床下に配置されている。そして、プリ触媒装置１０の上流側には第１空燃比センサ１２が配置され、プリ触媒装置１０の下流側つまりプリ触媒装置１０とメイン触媒装置１１との間には第２空燃比センサ１３が配置されている。   FIG. 1 schematically shows a system configuration of an air-fuel ratio control apparatus according to the present invention. An internal combustion engine 1 which is a gasoline engine includes a spark plug 4 in a combustion chamber 3 formed by a piston 2 and an intake air. A fuel injection valve 6 is provided immediately before the intake valve in the passage 5, and an air flow meter 7 and a throttle valve 8 for detecting the intake air amount are provided in the intake passage 5. The exhaust passage 9 is provided with an upstream pre-catalyst device 10 having a relatively small capacity and a downstream main catalyst device 11 having a relatively large capacity. The pre-catalyst device 10 is mounted, for example, at an outlet of an exhaust manifold, and the main catalyst device 11 is disposed, for example, under the floor of a vehicle. A first air-fuel ratio sensor 12 is disposed upstream of the pre-catalyst device 10, and a second air-fuel ratio sensor 13 is disposed downstream of the pre-catalyst device 10, that is, between the pre-catalyst device 10 and the main catalyst device 11. Has been placed.

これらの２つの空燃比センサ１２，１３は、いわゆる広域型空燃比センサあるいは出力がステップ的に変化する酸素センサのいずれであってもよいが、この実施例では、２つの空燃比センサ１２，１３の双方が酸素センサからなる。そして、これらの空燃比センサ１２，１３は、その素子を加熱するセラミックスヒータ等のヒータを各々備えている。ここでは、第１空燃比センサ１２のヒータを第１ヒータ１４とし、第２空燃比センサ１３のヒータを第２ヒータ１５とする。これらのヒータ１４，１５は、その通電量が、ＯＮデューティ比の可変制御によって制御される。   These two air-fuel ratio sensors 12 and 13 may be either a so-called wide-area type air-fuel ratio sensor or an oxygen sensor whose output changes stepwise. In this embodiment, the two air-fuel ratio sensors 12 and 13 are used. Both consist of oxygen sensors. These air-fuel ratio sensors 12 and 13 are each provided with a heater such as a ceramic heater for heating the element. Here, the heater of the first air-fuel ratio sensor 12 is the first heater 14, and the heater of the second air-fuel ratio sensor 13 is the second heater 15. The energization amounts of these heaters 14 and 15 are controlled by variable control of the ON duty ratio.

これらの２つの空燃比センサ１２，１３を用いた空燃比制御そのものは本発明の要部ではないので、その詳しい説明は省略するが、コントロールユニット１６において、公知の種々の態様で２つの空燃比センサ１２，１３の検出信号が利用される。例えば、上流側の第１空燃比センサ１２の検出信号を主に用いて燃料噴射量をフィードバック制御するとともに、下流側の第２空燃比センサ１３の検出信号を、そのフィードバック制御の片寄りの学習補正や触媒の劣化判定等に利用する、等の制御がなされる。   The air-fuel ratio control itself using these two air-fuel ratio sensors 12 and 13 is not a main part of the present invention, and thus detailed description thereof will be omitted. However, in the control unit 16, the two air-fuel ratios are known in various known modes. Detection signals of the sensors 12 and 13 are used. For example, the fuel injection amount is feedback-controlled mainly using the detection signal of the upstream first air-fuel ratio sensor 12, and the detection signal of the downstream second air-fuel ratio sensor 13 is learned in the vicinity of the feedback control. Controls such as correction and determination of catalyst deterioration are performed.

上記の空燃比センサ１２，１３においては、例えば図２に例示するような温度特性があり、排気空燃比に対する正しい出力を得るためには、ある温度範囲Ｔ１（例えば６００℃〜６５０℃の範囲）に素子温度を維持する必要がある。   The air-fuel ratio sensors 12 and 13 have temperature characteristics as exemplified in FIG. 2, for example. In order to obtain a correct output with respect to the exhaust air-fuel ratio, a certain temperature range T1 (for example, a range of 600 ° C. to 650 ° C.). It is necessary to maintain the element temperature.

そのため、空燃比制御に主に利用される上流側の第１空燃比センサ１２については、素子温度を例えば熱電対等を用いて検出し、この検出温度が上記の温度範囲Ｔ１内となるように、第１ヒータ１４に対するＯＮデューティ比がフィードバック制御される。   Therefore, for the upstream first air-fuel ratio sensor 12 mainly used for air-fuel ratio control, the element temperature is detected using, for example, a thermocouple, and the detected temperature falls within the temperature range T1. The ON duty ratio for the first heater 14 is feedback controlled.

これに対し、下流側の第２空燃比センサ１３については、上記の第１ヒータ１４のフィードバック制御のパラメータを流用して、第２ヒータ１５のＯＮデューティ比が簡易的に制御される。   On the other hand, for the second air-fuel ratio sensor 13 on the downstream side, the ON duty ratio of the second heater 15 is simply controlled by using the feedback control parameters of the first heater 14 described above.

図３は、第２ヒータ１５の制御の一実施例を示すフローチャートであって、この実施例では、ステップ１で、第１空燃比センサ１２の素子温度を読み込み、ステップ２で、この第１空燃比センサ１２の素子温度を用いて、下流側の第２空燃比センサ１３の素子温度を推定する。これは下記の論理式による。 FIG. 3 is a flowchart showing an embodiment of the control of the second heater 15. In this embodiment, the element temperature of the first air-fuel ratio sensor 12 is read in step 1, and the first empty air is detected in step 2. The element temperature of the second air-fuel ratio sensor 13 on the downstream side is estimated using the element temperature of the fuel ratio sensor 12. This is based on the following logical expression.

Ｒｒ酸素センサ素子温度＝Ｃ１＋Ｃ２＊ｅｘｐ（−ｔ／τ）
ここで、Ｃ１およびＣ２は適宜な定数である。「ｅｘｐ（−ｔ／τ）」は、第１空燃比センサ１２の素子温度の一次応答遅れを表しており、τは第１空燃比センサ１２の素子温度の時定数である。 Rr oxygen sensor element temperature = C 1 + C 2 * exp (−t / τ )
Here, C 1 and C 2 are appropriate constants. “Exp (−t / τ )” represents the primary response delay of the element temperature of the first air-fuel ratio sensor 12, and τ is the time constant of the element temperature of the first air-fuel ratio sensor 12.

このようにして推定した第２空燃比センサ１３の素子温度を用いて、ステップ３で、第２ヒータ１５のＯＮデューティ比を算出し、ステップ４で、このＯＮデューティ比に沿って第２ヒータ１５の通電を行う。これにより、第２空燃比センサ１３の素子温度が、上述の温度範囲Ｔ１内に維持される。   Using the element temperature of the second air-fuel ratio sensor 13 estimated in this way, the ON duty ratio of the second heater 15 is calculated in step 3, and in step 4, the second heater 15 is adjusted along this ON duty ratio. Turn on the power. Thereby, the element temperature of the 2nd air fuel ratio sensor 13 is maintained in the above-mentioned temperature range T1.

ここで、一つの実施例では、ステップ３で算出したＯＮデューティ比が所定の上限値を越えている場合には、実際に出力するＯＮデューティ比をその上限値に制限するようにしている。そして、ステップ３で算出された要求デューティ比を所定のテーブルを用いて要求熱量に換算し、上限値のＯＮデューティ比での通電による熱量を積算していって、この積算熱量が上記要求熱量に達するまで通電を行う。Here, in one embodiment, when the ON duty ratio calculated in step 3 exceeds a predetermined upper limit value, the actually output ON duty ratio is limited to the upper limit value. Then, the required duty ratio calculated in step 3 is converted into a required heat amount using a predetermined table, and the heat amount due to energization at the upper limit ON duty ratio is integrated. Energize until it reaches.

１…内燃機関
９…排気通路
１０…プリ触媒装置
１２…第１空燃比センサ
１３…第２空燃比センサ
１４…第１ヒータ
１５…第２ヒータ
１６…コントロールユニット DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 9 ... Exhaust passage 10 ... Pre catalyst apparatus 12 ... 1st air fuel ratio sensor 13 ... 2nd air fuel ratio sensor 14 ... 1st heater 15 ... 2nd heater 16 ... Control unit

Claims (5)

内燃機関の排気通路において触媒装置の上流側に配置された第１空燃比センサと、
この第１空燃比センサに付設された第１ヒータと、
触媒装置の下流側に配置された第２空燃比センサと、
この第２空燃比センサに付設された第２ヒータと、
上記第１空燃比センサの素子温度の検出に基づいて該素子温度が所定温度となるように上記第１ヒータの通電をフィードバック制御する第１ヒータ制御手段と、
を備えてなる内燃機関の空燃比制御装置において、
上記第１ヒータ制御手段による第１ヒータの通電制御に相関して上記第２ヒータの通電を制御することを特徴とする内燃機関の空燃比制御装置。 A first air-fuel ratio sensor disposed upstream of the catalyst device in the exhaust passage of the internal combustion engine;
A first heater attached to the first air-fuel ratio sensor;
A second air-fuel ratio sensor disposed downstream of the catalyst device;
A second heater attached to the second air-fuel ratio sensor;
First heater control means for feedback-controlling energization of the first heater based on detection of the element temperature of the first air-fuel ratio sensor so that the element temperature becomes a predetermined temperature;
In an air-fuel ratio control device for an internal combustion engine comprising:
An air-fuel ratio control device for an internal combustion engine, wherein the energization of the second heater is controlled in correlation with the energization control of the first heater by the first heater control means. 上記第１ヒータ制御手段による第１ヒータの制御デューティ比の一次遅れを用いて第２空燃比センサの素子温度を推定し、この推定素子温度に基づき上記第２ヒータを通電制御することを特徴とする請求項１に記載の内燃機関の空燃比制御装置。   The first heater control means estimates the element temperature of the second air-fuel ratio sensor using a primary delay of the control duty ratio of the first heater, and the energization control of the second heater is performed based on the estimated element temperature. The air-fuel ratio control apparatus for an internal combustion engine according to claim 1. 上記第１ヒータ制御手段による第１ヒータの制御デューティ比の一次遅れを用いて触媒装置下流側の排気温度を推定し、この推定排気温度に基づき上記第２ヒータを通電制御することを特徴とする請求項１に記載の内燃機関の空燃比制御装置。   An exhaust gas temperature on the downstream side of the catalyst device is estimated using a first order delay of a control duty ratio of the first heater by the first heater control means, and the second heater is energized and controlled based on the estimated exhaust gas temperature. The air-fuel ratio control apparatus for an internal combustion engine according to claim 1. 検出した第１空燃比センサの素子温度の一次遅れを用いて第２空燃比センサの素子温度を推定し、この推定素子温度に基づき上記第２ヒータを通電制御することを特徴とする請求項１に記載の内燃機関の空燃比制御装置。   2. The element temperature of the second air-fuel ratio sensor is estimated using the detected first-order lag of the element temperature of the first air-fuel ratio sensor, and energization control of the second heater is performed based on the estimated element temperature. An air-fuel ratio control device for an internal combustion engine according to claim 1. 検出した第１空燃比センサの素子温度の一次遅れを用いて触媒装置下流側の排気温度を推定し、この推定排気温度に基づき上記第２ヒータを通電制御することを特徴とする請求項１に記載の内燃機関の空燃比制御装置。   2. The exhaust temperature on the downstream side of the catalyst device is estimated using a first order lag of the detected element temperature of the first air-fuel ratio sensor, and the second heater is energized and controlled based on the estimated exhaust temperature. An air-fuel ratio control apparatus for an internal combustion engine as described.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6312855A (en) * 1986-07-04 1988-01-20 Toyota Motor Corp Air-fuel ratio controller for internal combustion engine
JP2000249679A (en) * 1999-03-03 2000-09-14 Toyota Motor Corp Heater control device of air/fuel ratio sensor
JP2005003500A (en) * 2003-06-11 2005-01-06 Toyota Motor Corp Heater control device
JP2007239689A (en) * 2006-03-10 2007-09-20 Suzuki Motor Corp Engine air-fuel ratio sensor protecting control device
JP2009007939A (en) * 2007-06-26 2009-01-15 Denso Corp Device for estimating temperature of gas sensor element

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6312855A (en) * 1986-07-04 1988-01-20 Toyota Motor Corp Air-fuel ratio controller for internal combustion engine
JP2000249679A (en) * 1999-03-03 2000-09-14 Toyota Motor Corp Heater control device of air/fuel ratio sensor
JP2005003500A (en) * 2003-06-11 2005-01-06 Toyota Motor Corp Heater control device
JP2007239689A (en) * 2006-03-10 2007-09-20 Suzuki Motor Corp Engine air-fuel ratio sensor protecting control device
JP2009007939A (en) * 2007-06-26 2009-01-15 Denso Corp Device for estimating temperature of gas sensor element

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