JP2009197672A - Combustion state detection device - Google Patents

Combustion state detection device Download PDF

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JP2009197672A
JP2009197672A JP2008040028A JP2008040028A JP2009197672A JP 2009197672 A JP2009197672 A JP 2009197672A JP 2008040028 A JP2008040028 A JP 2008040028A JP 2008040028 A JP2008040028 A JP 2008040028A JP 2009197672 A JP2009197672 A JP 2009197672A
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heat generation
generation rate
combustion
release rate
heat release
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JP5098690B2 (en
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Masaya Hoshi
真弥 星
Akikazu Kojima
昭和 小島
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Denso Corp
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Denso Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
    • F02D35/02—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions
    • F02D35/023—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining the cylinder pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/26—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using computer, e.g. microprocessor
    • F02D41/28—Interface circuits
    • F02D2041/281—Interface circuits between sensors and control unit

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion state detection device capable of calculating heat generation while reducing the effect of noise, and enhancing the detection accuracy of a combustion mass ratio. <P>SOLUTION: A noise removing unit 18 removes noise included in the heat release rate, in other words, the noise removing unit 18 removes the noise included in an electric signal output from a pressure sensor 25 when the heat release rate becomes maximum on the most phase lag side in a combustion chamber 12 calculated by a heat release rate calculating unit 16, and becomes below the lower limit of the heat release rate for the first time. Thus, the heat release rate in the combustion chamber 12 calculated by the heat release rate calculating unit 16, and the heat production amount calculated by integrating the heat release rate by a combustion mass ratio calculating unit 17 are reduced in an error after the second half of the combustion, in other words, the heat release rate reaches a peak. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、燃焼状態検出装置に関し、特に内燃機関の燃焼質量割合から内燃機関の燃焼状態を検出する燃焼状態検出装置に関する。   The present invention relates to a combustion state detection device, and more particularly to a combustion state detection device that detects a combustion state of an internal combustion engine from a combustion mass ratio of the internal combustion engine.

内燃機関、特にディーゼルエンジンの場合、エミッション抑制、ドラビリや燃費の改善、振動や騒音の低減の観点から燃焼室の燃焼状態を検出する必要がある。このような燃焼状態検出装置として、燃焼質量割合から燃焼状態を検出することが提案されている。この場合、クランク角度によって変化する熱発生率を積分して熱発生量を算出し、熱発生率の積分値が総熱発生量の例えば５０％あるいは９０％に達する点を燃焼質量割合として求めることにより、内燃機関の燃焼状態を検出する。熱発生率は、例えば燃焼室の圧力変化などに基づいて算出される（特許文献１、２）。特許文献１、２の場合、例えば圧力センサで検出した燃焼室の圧力は、圧力センサから電気信号として出力される。
特許第２８３０３０５号明細書 特開２００２−２４２７５０号公報 In the case of an internal combustion engine, particularly a diesel engine, it is necessary to detect the combustion state of the combustion chamber from the viewpoint of suppressing emissions, improving drivability and fuel consumption, and reducing vibration and noise. As such a combustion state detection device, it has been proposed to detect a combustion state from a combustion mass ratio. In this case, the heat generation rate that varies depending on the crank angle is integrated to calculate the heat generation amount, and the point at which the integrated value of the heat generation rate reaches, for example, 50% or 90% of the total heat generation amount is obtained as the combustion mass ratio. Thus, the combustion state of the internal combustion engine is detected. The heat generation rate is calculated based on, for example, a pressure change in the combustion chamber (Patent Documents 1 and 2). In Patent Documents 1 and 2, for example, the pressure in the combustion chamber detected by the pressure sensor is output as an electrical signal from the pressure sensor.
Japanese Patent No. 2830305 JP 2002-242750 A

しかしながら、このようなセンサから出力される電気信号はノイズを含んでいる。ところで、燃焼室における燃焼状態は、所定のクランク角度の範囲で燃焼室における発熱量の変化に基づいて検出される。そのため、センサから出力される電気信号のノイズが大きくなると、熱発生率を積分する範囲によって算出する熱発生量にばらつきが生じるという問題がある。また、電気信号に含まれるノイズを除去するために電気信号に対しフィルタリング処理を施すと、センサから出力される電気信号の全体が歪んでしまう。その結果、所望の燃焼質量割合の正確な検出が困難になるという問題がある。   However, the electrical signal output from such a sensor contains noise. Incidentally, the combustion state in the combustion chamber is detected based on a change in the amount of heat generated in the combustion chamber within a predetermined crank angle range. Therefore, when the noise of the electrical signal output from the sensor increases, there is a problem that the amount of heat generation calculated depending on the range in which the heat generation rate is integrated varies. Further, if the filtering process is performed on the electrical signal in order to remove noise included in the electrical signal, the entire electrical signal output from the sensor is distorted. As a result, there is a problem that it is difficult to accurately detect a desired combustion mass ratio.

そこで、本発明は、上記の課題に鑑みてなされたものであり、その目的は、ノイズの影響を低減しつつ熱発生量を算出し、燃焼質量割合の検出精度が向上する燃焼状態検出装置を提供することにある。   Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a combustion state detection device that calculates the amount of heat generation while reducing the influence of noise and improves the detection accuracy of the combustion mass ratio. It is to provide.

請求項１記載の発明では、ノイズ除去手段は、熱発生率が設定クランク角度の範囲内で最も遅角側で熱発生率が最大となって遅角側で最初に下限熱発生率を下回ると、熱発生率算出手段で算出した熱発生率に含まれるノイズを除去する。最も遅角側で熱発生率が最大となった以降、すなわち燃焼の後半において、熱発生率に重畳するノイズが大きくなると、熱発生率の積算によって算出する熱発生量は設定クランク角度の範囲によって誤差が大きくなる。そこで、燃焼の後半において熱発生率が最初に下限熱発生率を下回ると、熱発生率に含まれるノイズを除去している。これにより、熱発生量は設定クランク角度の範囲に関わらず収束し、熱発生率の積算によって算出される熱発生量は誤差が低減される。また、燃焼の後半において熱発生率に含まれるノイズを除去することにより、熱発生率全体および熱発生量の波形全体の歪みは小さくなる。したがって、熱発生率に含まれるノイズの影響を低減しつつ熱発生量を算出することができ、燃焼質量割合の検出精度を向上することができる。   In the first aspect of the present invention, the noise removing means has a maximum heat generation rate on the most retarded side within the range of the set crank angle, and first falls below the lower limit heat generation rate on the retarded side. Then, noise included in the heat generation rate calculated by the heat generation rate calculation means is removed. After the heat release rate reaches its maximum on the most retarded side, that is, in the second half of combustion, if the noise superimposed on the heat release rate increases, the heat generation amount calculated by integrating the heat release rate depends on the set crank angle range. The error increases. Therefore, when the heat generation rate first falls below the lower limit heat generation rate in the second half of combustion, noise included in the heat generation rate is removed. As a result, the heat generation amount converges regardless of the range of the set crank angle, and an error is reduced in the heat generation amount calculated by integrating the heat generation rate. Further, by removing the noise included in the heat generation rate in the second half of combustion, the distortion of the entire heat generation rate and the entire waveform of the heat generation amount is reduced. Therefore, the amount of heat generation can be calculated while reducing the influence of noise included in the heat generation rate, and the detection accuracy of the combustion mass ratio can be improved.

請求項２記載の発明では、下限熱発生率は内燃機関の運転条件に応じて設定されている。例えば内燃機関の負荷が大きいとき、燃焼室における圧力の変化および熱発生率が大きいため、ノイズの影響は受けにくい。一方、内燃機関の負荷が小さいとき、燃焼室における圧力の変化および熱発生率は小さいため、ノイズの影響を受けやすくなる。内燃機関の負荷に応じて下限熱発生率を設定することにより、ノイズの影響の低減と波形の歪みの低減とが両立される。したがって、燃焼質量割合の検出精度を向上することができる。   In the invention according to claim 2, the lower limit heat generation rate is set according to the operating condition of the internal combustion engine. For example, when the load on the internal combustion engine is large, the pressure change and the heat generation rate in the combustion chamber are large, so that it is less susceptible to noise. On the other hand, when the load on the internal combustion engine is small, the pressure change and the heat generation rate in the combustion chamber are small, and therefore, it is easily affected by noise. By setting the lower limit heat generation rate according to the load of the internal combustion engine, both the reduction of the influence of noise and the reduction of waveform distortion can be achieved. Therefore, the detection accuracy of the combustion mass ratio can be improved.

以下、本発明による燃焼状態検出装置の一実施形態を図面に基づいて説明する。
図１に示すように、燃焼状態検出装置１０は、内燃機関１１の燃焼状態を検出する。内燃機関１１は、例えばディーゼルエンジンやガソリンエンジンなどのピストンエンジンが適用される。内燃機関１１は、複数の燃焼室１２を備えている。燃焼室１２は、シリンダブロック１３と図示しないピストンとの間に形成される。燃焼状態検出装置１０は、制御部１４、クランク角度検出部１５、熱発生率検出部１６、燃焼質量割合算出部１７、ノイズ除去部１８および下限値設定部１９を備えている。 Hereinafter, an embodiment of a combustion state detection apparatus according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, the combustion state detection device 10 detects the combustion state of the internal combustion engine 11. For example, a piston engine such as a diesel engine or a gasoline engine is applied to the internal combustion engine 11. The internal combustion engine 11 includes a plurality of combustion chambers 12. The combustion chamber 12 is formed between the cylinder block 13 and a piston (not shown). The combustion state detection device 10 includes a control unit 14, a crank angle detection unit 15, a heat generation rate detection unit 16, a combustion mass ratio calculation unit 17, a noise removal unit 18, and a lower limit value setting unit 19.

制御部１４は、内燃機関１１のＥＣＵ（Engine Control Unit）などによって構成され、ＣＰＵ、ＲＯＭおよびＲＡＭなどからなるマイクロコンピュータを有している。制御部１４は、ＲＯＭまたは図示しない記憶装置に記憶されているコンピュータプログラムにしたがって燃焼状態検出装置１０や内燃機関１１などの各部を制御する。クランク角度検出部１５は、内燃機関１１のクランクシャフト２１の回転角度すなわちクランク角度を検出する。クランク角度検出部１５は、クランクシャフト２１の回転角度を検出する角度センサ２２に接続している。クランク角度検出部１５は、角度センサ２２から出力された電気信号に基づいてクランクシャフト２１の回転角度を検出する。   The control unit 14 is constituted by an ECU (Engine Control Unit) of the internal combustion engine 11 and has a microcomputer including a CPU, a ROM, a RAM, and the like. The control unit 14 controls each unit such as the combustion state detection device 10 and the internal combustion engine 11 according to a computer program stored in a ROM or a storage device (not shown). The crank angle detector 15 detects the rotation angle of the crankshaft 21 of the internal combustion engine 11, that is, the crank angle. The crank angle detector 15 is connected to an angle sensor 22 that detects the rotation angle of the crankshaft 21. The crank angle detector 15 detects the rotation angle of the crankshaft 21 based on the electrical signal output from the angle sensor 22.

制御部１４は、回転数センサ２３およびアクセルセンサ２４に接続している。回転数センサ２３は、内燃機関１１のクランクシャフト２１の回転数を検出する。なお、回転数センサ２３は、角度センサ２２と共用してもよい。回転数センサ２３は、検出したクランクシャフト２１の回転数を電気信号として制御部１４へ出力する。アクセルセンサ２４は、図示しないアクセルペダルの踏み込み量を検出する。アクセルセンサ２４は、検出したアクセルペダルの踏み込み量を電気信号として制御部１４へ出力する。制御部１４は、回転数センサ２３およびアクセルセンサ２４から出力された電気信号から内燃機関１１の運転条件を検出する。   The control unit 14 is connected to the rotation speed sensor 23 and the accelerator sensor 24. The rotation speed sensor 23 detects the rotation speed of the crankshaft 21 of the internal combustion engine 11. The rotation speed sensor 23 may be shared with the angle sensor 22. The rotation speed sensor 23 outputs the detected rotation speed of the crankshaft 21 to the control unit 14 as an electrical signal. The accelerator sensor 24 detects the amount of depression of an accelerator pedal (not shown). The accelerator sensor 24 outputs the detected depression amount of the accelerator pedal to the control unit 14 as an electrical signal. The control unit 14 detects the operating condition of the internal combustion engine 11 from the electrical signals output from the rotation speed sensor 23 and the accelerator sensor 24.

熱発生率算出部１６は、内燃機関１１の各燃焼室１２における燃料の燃焼によって発生した熱発生率を筒内圧から算出する。熱発生率は、クランクシャフト２１の単位回転角度当たりの熱発生量である。したがって、熱発生率の単位は、「Ｊ／ｄｅｇ」で示される。内燃機関１１の各燃焼室１２には、それぞれ圧力センサ２５が設けられている。圧力センサ２５は、燃焼室１２における圧力を検出する筒内圧力検出手段である。圧力センサ２５は、検出した燃焼室１２の圧力を電気信号として制御部１４へ出力する。熱発生率算出部１６は、圧力センサ２５から出力された電気信号に基づいて熱発生率を算出する。制御部１４は、クランクシャフト２１が所定の角度回転するごとに、圧力センサ２５から燃焼室１２の圧力を取得する。制御部１４は、各燃焼室１２の圧力センサ２５から燃焼室１２ごとに圧力を取得する。   The heat generation rate calculation unit 16 calculates the heat generation rate generated by the combustion of fuel in each combustion chamber 12 of the internal combustion engine 11 from the in-cylinder pressure. The heat generation rate is a heat generation amount per unit rotation angle of the crankshaft 21. Therefore, the unit of heat release rate is indicated by “J / deg”. Each combustion chamber 12 of the internal combustion engine 11 is provided with a pressure sensor 25. The pressure sensor 25 is an in-cylinder pressure detection unit that detects the pressure in the combustion chamber 12. The pressure sensor 25 outputs the detected pressure in the combustion chamber 12 to the control unit 14 as an electrical signal. The heat generation rate calculation unit 16 calculates the heat generation rate based on the electrical signal output from the pressure sensor 25. The control unit 14 acquires the pressure of the combustion chamber 12 from the pressure sensor 25 every time the crankshaft 21 rotates by a predetermined angle. The control unit 14 acquires the pressure for each combustion chamber 12 from the pressure sensor 25 of each combustion chamber 12.

熱発生率算出部１６は、例えば以下の式（１）に基づいて圧力センサ２５で取得した燃焼室１２の圧力Ｐから熱発生率ｄＱ（Ｊ／ｄｅｇ）を算出する。なお、下記の式（１）は圧力センサ２５で算出した圧力Ｐから熱発生率ｄＱを算出する式の一例である。式（１）において、Ｐは圧力センサ２５で検出した筒内圧（ｋＰａ）である。また、Ｖは燃焼室１２の容積（ｍ３）であり、θはクランク角度（ｄｅｇ）であり、κは比熱比（−）である。 The heat generation rate calculation unit 16 calculates the heat generation rate dQ (J / deg) from the pressure P of the combustion chamber 12 acquired by the pressure sensor 25 based on the following formula (1), for example. The following formula (1) is an example of a formula for calculating the heat generation rate dQ from the pressure P calculated by the pressure sensor 25. In the formula (1), P is the in-cylinder pressure (kPa) detected by the pressure sensor 25. V is the volume (m 3 ) of the combustion chamber 12, θ is the crank angle (deg), and κ is the specific heat ratio (−).

Figure 2009197672
Figure 2009197672

熱発生率算出部１６は、クランクシャフト２１の回転角度と圧力センサ２５で検出した圧力とから燃焼室１２の熱変化率を検出する。検出された熱変化率は、図２（Ａ）に示すようにクランク角度に応じて変化する。   The heat generation rate calculation unit 16 detects the rate of heat change in the combustion chamber 12 from the rotation angle of the crankshaft 21 and the pressure detected by the pressure sensor 25. The detected rate of change of heat changes according to the crank angle as shown in FIG.

燃焼質量割合算出部１７は、熱発生量および燃焼質量割合を算出する。燃焼質量割合算出部１７は、上述の熱発生率算出部１６で算出した燃焼室１２の熱変化率から熱発生量を算出する。熱発生率算出部１６で算出した熱発生率は、クランクシャフト２１の単位回転角度あたりの熱発生量である。燃焼質量割合算出部１７は、熱発生率を積分することにより、燃焼室１２における熱発生量を算出する。算出された熱発生量は、図２（Ｂ）に示すようにクランク角度に応じて変化する。   The combustion mass ratio calculation unit 17 calculates a heat generation amount and a combustion mass ratio. The combustion mass ratio calculation unit 17 calculates a heat generation amount from the heat change rate of the combustion chamber 12 calculated by the heat generation rate calculation unit 16 described above. The heat generation rate calculated by the heat generation rate calculation unit 16 is a heat generation amount per unit rotation angle of the crankshaft 21. The combustion mass ratio calculation unit 17 calculates the heat generation amount in the combustion chamber 12 by integrating the heat generation rate. The calculated heat generation amount changes according to the crank angle as shown in FIG.

また、燃焼質量割合算出部１７は、燃焼質量割合を算出する。燃焼質量割合算出部１７は、クランクシャフト２１の所定の回転角度範囲で設定された設定クランク角度の範囲内で熱発生率を積分することにより、燃焼室１２における総熱発生量Ｑｔを算出する。燃焼質量割合算出部１７は、図２（Ａ）に示すようにクランクシャフト２１の回転角度が予め設定された積分開始角θ１から積分終了角θ２の範囲で総熱発生量Ｑｔを算出する。燃焼質量割合算出部１７は、この総熱発生量Ｑｔを１００％としたとき、θ１から積算した熱発生量が５０％に達したクランク角度を燃焼５０％点とする燃焼質量割合として算出する。燃焼質量割合は、燃焼５０％点に限らず、内燃機関１１の制御に応じて任意の点を設定することができる。ノイズ除去部１８は、熱発生率算出部１６で算出する熱発生率に含まれるノイズを除去する。   Further, the combustion mass ratio calculation unit 17 calculates the combustion mass ratio. The combustion mass ratio calculation unit 17 calculates the total heat generation amount Qt in the combustion chamber 12 by integrating the heat generation rate within a set crank angle range set within a predetermined rotation angle range of the crankshaft 21. As shown in FIG. 2 (A), the combustion mass ratio calculation unit 17 calculates the total heat generation amount Qt in the range where the rotation angle of the crankshaft 21 is preset from the integration start angle θ1 to the integration end angle θ2. When the total heat generation amount Qt is 100%, the combustion mass ratio calculation unit 17 calculates the combustion mass ratio with the crank angle at which the heat generation amount integrated from θ1 has reached 50% as the combustion 50% point. The combustion mass ratio is not limited to the 50% combustion point, and any point can be set according to the control of the internal combustion engine 11. The noise removal unit 18 removes noise included in the heat generation rate calculated by the heat generation rate calculation unit 16.

下限値設定部１９は、ノイズ除去部１８によって熱発生率に含まれるノイズの除去を開始する熱発生率の閾値を熱発生率下限値として設定する。制御部１４は、回転数センサ２３で検出した内燃機関１１の回転数およびアクセルセンサ２４で検出したアクセルペダルの開度に基づいて内燃機関１１の運転条件を検出する。そして、制御部１４は、検出した内燃機関１１の運転条件に基づいて、熱発生率下限値を設定する。   The lower limit setting unit 19 sets, as the heat generation rate lower limit value, a threshold value of the heat generation rate at which the noise removal unit 18 starts removing noise included in the heat generation rate. The control unit 14 detects the operating condition of the internal combustion engine 11 based on the rotational speed of the internal combustion engine 11 detected by the rotational speed sensor 23 and the accelerator pedal opening detected by the accelerator sensor 24. Then, the control unit 14 sets a heat generation rate lower limit value based on the detected operating condition of the internal combustion engine 11.

次に、上記の構成による燃焼状態検出装置１０の作動について説明する。
制御部１４は、内燃機関１１のクランクシャフト２１の回転角度が検出開始角θ０になると、所定の回転角ごとに圧力センサ２５から燃焼室１２の圧力を取得する。検出開始角θ０は、例えば図示しないピストンの下死点（ＢＤＣ）に設定されている。熱発生率算出部１６は、圧力センサ２５から取得した燃焼室１２の圧力から燃焼室１２の熱発生率を算出する。算出した燃焼室１２の熱発生率は、図２（Ａ）に示すようにクランク角度に応じて変化する波形として得られる。この熱発生率が最大となるときのクランク角度を、ピーク角θｍとする。クランク角度がピーク角θｍを超えると、熱発生率は徐々に減少する。 Next, the operation of the combustion state detection device 10 configured as described above will be described.
When the rotation angle of the crankshaft 21 of the internal combustion engine 11 reaches the detection start angle θ0, the control unit 14 acquires the pressure in the combustion chamber 12 from the pressure sensor 25 for each predetermined rotation angle. The detection start angle θ0 is set, for example, at a bottom dead center (BDC) of a piston (not shown). The heat generation rate calculation unit 16 calculates the heat generation rate of the combustion chamber 12 from the pressure of the combustion chamber 12 acquired from the pressure sensor 25. The calculated heat release rate of the combustion chamber 12 is obtained as a waveform that changes according to the crank angle as shown in FIG. The crank angle when the heat generation rate is maximized is the peak angle θm. When the crank angle exceeds the peak angle θm, the heat generation rate gradually decreases.

ところで、図２（Ａ）に示すように、熱発生率は、真の値を示す太破線の真値に対し、燃焼室１２の圧力に基づいて熱発生率算出部１６で算出した太実線で示す算出値に誤差が生じる。この誤差は、圧力センサ２５から出力される電気信号に含まれるノイズに起因する。そのため、熱発生率算出部１６で算出した算出値は、真値を挟んで上下に誤差を含んでいる。そして、この誤差は、燃焼室１２の容積に応じて大きさが変化し、上死点（ＴＤＣ）位置から離れるほど大きな値となる。本実施形態の場合、燃焼の後半とは、クランクシャフト２１の回転角がピーク角θｍを超えた後を意味している。特に、この燃焼の後半では、ピーク角θｍからのクランクシャフト２１の回転角が大きくなるにつれて、ピストンの下降にともない燃焼室１２の容積は増大するため、熱発生率算出値の誤差は増大する。   Incidentally, as shown in FIG. 2A, the heat generation rate is a thick solid line calculated by the heat generation rate calculation unit 16 based on the pressure in the combustion chamber 12 with respect to the true value of the thick broken line indicating the true value. An error occurs in the calculated value shown. This error is caused by noise included in the electrical signal output from the pressure sensor 25. For this reason, the calculated value calculated by the heat generation rate calculating unit 16 includes errors up and down across the true value. The magnitude of the error changes according to the volume of the combustion chamber 12 and increases as the distance from the top dead center (TDC) position increases. In the present embodiment, the latter half of combustion means after the rotation angle of the crankshaft 21 exceeds the peak angle θm. In particular, in the second half of the combustion, as the rotation angle of the crankshaft 21 from the peak angle θm increases, the volume of the combustion chamber 12 increases as the piston descends, so the error in the calculated heat release rate increases.

このように熱発生率の算出値において誤差が大きくなると、熱発生率に基づいて算出する熱発生量についても図２（Ｂ）に示すように誤差が大きくなる。特に、熱発生率の算出値の誤差が大きな燃焼の後半では、算出した熱発生量の誤差も増大する。そのため、積分終了角θ２の設定位置によって、燃焼質量割合算出部１７で算出する総熱発生量が変化し、この総熱発生量を基礎に算出する燃焼５０％点に対応するクランク角度の値も誤差が大きくなる。その結果、内燃機関１１の燃焼状態の検出精度が低下する。   As described above, when the error increases in the calculated value of the heat generation rate, the error also increases in the heat generation amount calculated based on the heat generation rate as shown in FIG. In particular, in the second half of the combustion in which the calculated value of the heat generation rate has a large error, the calculated heat generation amount error also increases. Therefore, the total heat generation amount calculated by the combustion mass ratio calculation unit 17 changes depending on the setting position of the integration end angle θ2, and the value of the crank angle corresponding to the 50% combustion point calculated based on this total heat generation amount is also set. The error increases. As a result, the detection accuracy of the combustion state of the internal combustion engine 11 decreases.

一方、熱発生率に含まれるノイズの影響を低減するために、ノイズ除去部１８でノイズを低減することも考えられる。この場合、検出開始角θ０から全域にわたりノイズを除去、すなわちフィルタリングすると、図２（Ａ）の細破線で示すように熱発生率算出部１６で検出した熱発生率の波形は全体として歪みや遅れが生じてしまう。その結果、燃焼質量割合算出部１７において熱発生率を積分した熱発生量も、真値からの差が拡大する。   On the other hand, in order to reduce the influence of noise included in the heat generation rate, it is conceivable to reduce noise by the noise removing unit 18. In this case, when noise is removed, that is, filtered from the detection start angle θ0, the waveform of the heat generation rate detected by the heat generation rate calculation unit 16 as a whole is distorted or delayed as shown by a thin broken line in FIG. Will occur. As a result, the difference from the true value of the heat generation amount obtained by integrating the heat generation rate in the combustion mass ratio calculation unit 17 also increases.

そこで、本実施形態の場合、ノイズ除去部１８は、図２（Ａ）に示すように熱発生率算出部１６で算出した熱発生率が最大となるピーク角θｍを超えた後であって、その熱発生率が熱発生率下限値ｈを下回ると、細実線で示すように熱発生率に含まれるノイズである高周波成分をフィルタリングする。熱発生率が熱発生率下限値ｈ以上であれば、熱発生率の値も大きいため、熱発生率算出部１６で算出した熱発生率はノイズの影響を受けにくい。一方、熱発生率が熱発生率下限値ｈを下回ると、熱発生率の値も小さくなるため、熱発生率算出部１６で検出した熱発生率はノイズの影響を受けやすくなる。熱発生率が熱発生率下限値ｈを下回ってからノイズ除去部１８でノイズを除去することにより、積分開始角θ１からピーク角θｍを超えるまでノイズ除去による熱発生率の波形の歪みや遅れの影響を受けることなく、ノイズの大きな領域においてもノイズの影響が低減される。なお、図２（Ｂ）における線種は、図２（Ａ）における線種に対応している。   Therefore, in the present embodiment, the noise removing unit 18 is after the peak angle θm at which the heat generation rate calculated by the heat generation rate calculation unit 16 is maximum as shown in FIG. When the heat generation rate falls below the heat generation rate lower limit h, high frequency components that are noise included in the heat generation rate are filtered as indicated by a thin solid line. If the heat generation rate is equal to or higher than the heat generation rate lower limit h, the value of the heat generation rate is large, and thus the heat generation rate calculated by the heat generation rate calculation unit 16 is not easily affected by noise. On the other hand, when the heat generation rate falls below the heat generation rate lower limit value h, the value of the heat generation rate also decreases, so that the heat generation rate detected by the heat generation rate calculation unit 16 is easily affected by noise. After the heat generation rate falls below the heat generation rate lower limit h, noise is removed by the noise removing unit 18, so that distortion and delay of the heat generation rate waveform due to noise removal from the integration start angle θ1 to the peak angle θm are exceeded. Without being affected, the influence of noise is reduced even in a noisy region. Note that the line types in FIG. 2B correspond to the line types in FIG.

下限値設定部１９は、内燃機関１１の回転数およびアクセルペダルの開度から検出した内燃機関１１の運転条件に基づいて熱発生率下限値ｈを設定する。例えば内燃機関１１の負荷が大きいとき、内燃機関１１に噴射される燃料の量は多くなる。そのため、燃焼室１２における熱発生率も増大する。一方、内燃機関１１の負荷が小さいとき、内燃機関１１に噴射される燃料の量は少なくなる。そのため、燃焼室１２における熱発生率も低下する。このように、下限値設定部１９は、熱発生率下限値ｈを内燃機関１１の運転条件に基づいて設定している。熱発生率下限値ｈは、内燃機関１１の運転条件（内燃機関１１の回転数、燃料の噴射量）に対する関数として設定される。下限値設定部１９は、例えば制御部１４のＲＯＭなどに、内燃機関１１の運転条件に応じた熱発生率下限値ｈのマップを有している。下限値設定部１９は、検出した内燃機関１１の運転条件に基づいて、対応する熱発生率下限値ｈをマップから取得する。   The lower limit setting unit 19 sets the heat generation rate lower limit h based on the operating condition of the internal combustion engine 11 detected from the rotational speed of the internal combustion engine 11 and the opening of the accelerator pedal. For example, when the load on the internal combustion engine 11 is large, the amount of fuel injected into the internal combustion engine 11 increases. Therefore, the heat generation rate in the combustion chamber 12 also increases. On the other hand, when the load on the internal combustion engine 11 is small, the amount of fuel injected into the internal combustion engine 11 decreases. Therefore, the heat generation rate in the combustion chamber 12 is also reduced. Thus, the lower limit setting unit 19 sets the heat release rate lower limit h based on the operating conditions of the internal combustion engine 11. The heat release rate lower limit h is set as a function with respect to the operating conditions of the internal combustion engine 11 (the rotational speed of the internal combustion engine 11 and the fuel injection amount). The lower limit value setting unit 19 has a map of the heat generation rate lower limit value h corresponding to the operating conditions of the internal combustion engine 11, for example, in the ROM of the control unit 14. The lower limit setting unit 19 acquires a corresponding heat generation rate lower limit h from the map based on the detected operating condition of the internal combustion engine 11.

以上説明したように、本発明の一実施形態では、熱発生率算出部１６で算出した燃焼室１２における熱発生率が最大となって最初に熱発生率下限値ｈを下回ると、ノイズ除去部１８は熱発生率に含まれるノイズすなわち圧力センサ２５から出力される電気信号に含まれるノイズを除去する。これにより、熱発生率算出部１６で算出する燃焼室１２における熱発生率、および燃焼質量割合算出部１７で熱発生率を積分することにより算出する熱発生量は、燃焼の後半すなわち熱発生率がピークとなった以降における誤差が低減される。したがって、内燃機関１１の燃焼質量割合の検出精度を向上することができる。   As described above, in one embodiment of the present invention, when the heat generation rate in the combustion chamber 12 calculated by the heat generation rate calculation unit 16 is maximized and first falls below the heat generation rate lower limit h, the noise removal unit. 18 removes noise included in the heat generation rate, that is, noise included in the electrical signal output from the pressure sensor 25. Thus, the heat generation rate in the combustion chamber 12 calculated by the heat generation rate calculation unit 16 and the heat generation amount calculated by integrating the heat generation rate in the combustion mass ratio calculation unit 17 are the second half of combustion, that is, the heat generation rate. The error after the peak is reduced. Therefore, the detection accuracy of the combustion mass ratio of the internal combustion engine 11 can be improved.

また、本発明の一実施形態では、ノイズ除去部１８でノイズの除去を開始する熱発生率下限値ｈを内燃機関１１の運転条件（回転数、噴射量）に応じて設定している。したがって、内燃機関１１の運転条件に応じて燃焼質量割合の検出精度、および燃焼状態の検出精度を向上することができる。
以上説明した本発明は、上記実施形態に限定されるものではなく、その要旨を逸脱しない範囲で種々の実施形態に適用可能である。 In one embodiment of the present invention, the heat generation rate lower limit h at which the noise removing unit 18 starts removing noise is set according to the operating conditions (the rotational speed and the injection amount) of the internal combustion engine 11. Therefore, the detection accuracy of the combustion mass ratio and the detection accuracy of the combustion state can be improved according to the operating conditions of the internal combustion engine 11.
The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

本発明の一実施形態による燃焼状態検出装置の構成を示す概略図Schematic which shows the structure of the combustion state detection apparatus by one Embodiment of this invention. （Ａ）はクランク角度と熱発生率との関係を示す概略図であり、（Ｂ）はクランク角度と熱発生量との関係を示す概略図(A) is the schematic which shows the relationship between a crank angle and a heat release rate, (B) is the schematic which shows the relationship between a crank angle and the amount of heat generation

符号の説明Explanation of symbols

図面中、１０は燃焼状態検出装置、１１は内燃機関、１２は燃焼室、１５はクランク角度検出部（クランク角度検出手段）、１６は熱発生率検出部（熱発生率算出手段）、１７は燃焼質量割合算出部（燃焼質量割合算出手段）、１８はノイズ除去部（ノイズ除去手段）、２２は角度センサ（クランク角度検出手段）、２５は圧力センサ（筒内圧検出手段）を示す。   In the drawing, 10 is a combustion state detection device, 11 is an internal combustion engine, 12 is a combustion chamber, 15 is a crank angle detection unit (crank angle detection means), 16 is a heat generation rate detection unit (heat generation rate calculation means), and 17 is A combustion mass ratio calculation section (combustion mass ratio calculation means), 18 is a noise removal section (noise removal means), 22 is an angle sensor (crank angle detection means), and 25 is a pressure sensor (in-cylinder pressure detection means).

Claims (2)

内燃機関の各燃焼室における燃焼状態を検出する燃焼状態検出装置であって、
前記内燃機関のクランク角度を検出するクランク角度検出手段と、
クランク角度によって変化する前記燃焼室の筒内圧を検出する筒内圧検出手段と、
前記筒内圧に基づいて前記燃焼室における熱発生率を算出する熱発生率算出手段と、
前記熱発生率算出手段で算出した熱発生率が、予め設定されたクランク角度の範囲内で最も遅角側において最大の熱発生率となったときよりも遅角側で最初に予め設定された下限熱発生率を下回ると、前記熱発生率算出手段で算出した熱発生率に含まれるノイズを除去するノイズ除去手段と、
前記設定クランク角度の範囲内で熱発生率を積算した熱発生量から、燃焼質量割合を算出する燃焼質量割合算出手段と、
を備えることを特徴とする燃焼状態検出装置。 A combustion state detection device for detecting a combustion state in each combustion chamber of an internal combustion engine,
Crank angle detecting means for detecting a crank angle of the internal combustion engine;
An in-cylinder pressure detecting means for detecting an in-cylinder pressure in the combustion chamber that varies depending on a crank angle;
Heat generation rate calculating means for calculating a heat generation rate in the combustion chamber based on the in-cylinder pressure;
The heat generation rate calculated by the heat generation rate calculating means is preset in advance on the retard side than when the maximum heat generation rate is obtained on the most retard side within the range of the crank angle set in advance. When less than the lower limit heat generation rate, noise removal means for removing noise included in the heat generation rate calculated by the heat generation rate calculation means,
A combustion mass ratio calculating means for calculating a combustion mass ratio from a heat generation amount obtained by integrating the heat generation rates within the set crank angle range;
A combustion state detection apparatus comprising: 前記下限熱発生率は、前記内燃機関の運転条件に応じて設定されていることを特徴とする請求項１記載の燃焼状態検出装置。   The combustion state detection device according to claim 1, wherein the lower limit heat generation rate is set according to an operating condition of the internal combustion engine.
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Publication number Priority date Publication date Assignee Title
GB2475062A (en) * 2009-11-03 2011-05-11 Gm Global Tech Operations Inc Method for determining an index of the fuel combustion in an engine cylinder
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JP2014240617A (en) * 2013-06-11 2014-12-25 トヨタ自動車株式会社 Heat generation rate waveform creation device of internal combustion engine and combustion state diagnosis device
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