JP2023145122A5

JP2023145122A5 -

Info

Publication number: JP2023145122A5
Application number: JP2022052419A
Authority: JP
Filing date: 2022-03-28
Publication date: 2024-03-29

Description

本発明の一態様は、
被測定ガス（Ｇ）に含まれるＮＯｘを検出するセンサ素子（１）と、上記センサ素子を加熱するヒータ（Ｈ）と、上記センサ素子及び上記ヒータの動作を制御すると共に、上記センサ素子からの信号に基づいてＮＯｘ濃度を算出するセンサ制御部（１０）と、を備えるＮＯｘセンサ（Ｓ）であって、
上記センサ素子は、
ガス導入部（３）を介して上記被測定ガスが導入され、固体電解質体（１１）を室壁とする被測定ガス室（２）と、
上記被測定ガス室において、導入されるガス流れの上流側に配置され、上記被測定ガス中のＨ₂Ｏ濃度と相関を有する第１信号（Ｉｐ）を出力する第１セル（１ｐ）、及び、上記第１セルよりも下流側に配置され、上記被測定ガス中のＮＯｘ濃度及びＨ₂Ｏ濃度に応じた第２信号（Ｉｓ）を出力する第２セル（１ｓ）と、を有しており、
上記センサ制御部は、
上記第２信号に基づくＮＯｘ濃度基準値（Ｃ１）を算出するＮＯｘ濃度基準値算出部（１０１）と、
上記第１信号又は外部情報に基づいて、Ｈ₂Ｏ濃度又はＨ₂Ｏ濃度と相関を有する濃度情報を含むＨ₂Ｏ濃度情報（Ｃｉ）を検出するＨ₂Ｏ濃度情報検出部（１０２）と、
上記ＮＯｘ濃度基準値を、上記Ｈ₂Ｏ濃度情報に基づいてオフセット補正する、ＮＯｘ濃度補正部（１０３）と、
上記第１セル及び上記第２セルへの印加電圧を制御する検出制御部（２００）と、を有し、
上記ＮＯｘ濃度補正部は、予め定められた基準環境温度（Ｔ０）にて取得される上記センサ素子の出力特性に基づいて、上記Ｈ₂Ｏ濃度情報に対応する上記第２信号のオフセット補正情報を記憶しており、上記基準環境温度は、上記センサ素子の搭載環境における上記被測定ガスの定常温度域に設定されており、
上記検出制御部は、電圧印加指示部（２０２）から入力される指示電圧（Ｖ０）に応じた電圧を生成する電圧印加回路（２０１）と、指示電圧補正部（２０３）とを備え、上記指示電圧補正部は、上記電圧印加回路にて生成される実電圧（Ｖ１）を検出する電圧検出部（２０３ａ）と、上記指示電圧を、上記指示電圧と上記実電圧との差分値に基づいて補正する補正値算出部（２０３ｂ）とを備える、ＮＯｘセンサにある。 One aspect of the present invention is
A sensor element (1) that detects NOx contained in the gas to be measured (G), a heater (H) that heats the sensor element, and controls the operation of the sensor element and the heater, and A NOx sensor (S) comprising a sensor control unit (10) that calculates a NOx concentration based on a signal,
The above sensor element is
A gas to be measured chamber (2) into which the gas to be measured is introduced via a gas introduction part (3) and has a solid electrolyte body (11) as a chamber wall;
A first cell (1p) that is arranged in the upstream side of the gas flow to be introduced in the gas to be measured chamber and outputs a first signal (Ip) having a correlation with the H ₂ O concentration in the gas to be measured; , a second cell (1s) that is disposed downstream of the first cell and outputs a second signal (Is) according to the NOx concentration and H ₂ O concentration in the gas to be measured. Ori,
The above sensor control section is
a NOx concentration reference value calculation unit (101) that calculates a NOx concentration reference value (C1) based on the second signal;
an H _{2 O concentration information detection unit (102) that detects H 2} O concentration or H ₂ O concentration information (Ci) including concentration information having a correlation with the H ₂ O concentration, based on the first signal or _external information; ,
a NOx concentration correction unit (103) that offset-corrects the NOx concentration reference value based on the H ₂ O concentration information;
a detection control unit (200) that controls voltages applied to the first cell and the second cell ;
The NOx concentration correction section calculates offset correction information of the second signal corresponding to the H ₂ O concentration information based on the output characteristics of the sensor element acquired at a predetermined reference environmental temperature (T0). The reference environmental temperature is set to a steady temperature range of the gas to be measured in the environment in which the sensor element is mounted;
The detection control section includes a voltage application circuit (201) that generates a voltage according to an instruction voltage (V0) input from a voltage application instruction section (202), and an instruction voltage correction section (203), and includes an instruction voltage correction section (203). The voltage correction section includes a voltage detection section (203a) that detects the actual voltage (V1) generated by the voltage application circuit, and corrects the indicated voltage based on a difference value between the indicated voltage and the actual voltage. The NOx sensor includes a correction value calculation unit (203b) for calculating the correction value .

センサ電極２２及びモニタ電極２３は、ガス流れ方向Ｘにおいて同等となる位置に並設され、ポンプ電極２１よりも小面積の同一形状に形成される。これにより、排ガスＧの流れに対して、センサ電極２２とモニタ電極２３が同等条件となり、センサセル１ｓとモニタセル１ｍの出力を比較することにより、ＮＯｘ出力に含まれる残存酸素の影響を取り除くことができる。 The sensor electrode 22 and the monitor electrode 23 are arranged in parallel at the same position in the gas flow direction X, and are formed in the same shape with a smaller area than the pump electrode 21. As a result, the sensor electrode 22 and the monitor electrode 23 are placed under the same conditions with respect to the flow of the exhaust gas G, and by comparing the outputs of the sensor cell 1s and the monitor cell 1m, the influence of residual oxygen contained in the NOx output can be removed. I can do it.

これに対して、指示電圧補正部２０３を備える場合には、以下の式により表される補正指示電圧Ｖ２が印加されることになる。
補正指示電圧Ｖ２＝指示電圧Ｖ０－補正値［実電圧Ｖ１－指示電圧Ｖ０］
このようにして補正された補正指示電圧Ｖ２が、電圧印加回路２０１へ出力されることにより、実際の印加電圧が、本来の指示電圧Ｖ０となる。そして、ポンプセル１ｐにおけるＨ₂Ｏの分解反応が抑制され、センサセル電流Ｉｓ、モニタセル電流Ｉｍのばらつきが抑制されることにより、ＮＯｘ出力誤差を低減することができる。 On the other hand, when the command voltage correction unit 203 is provided, a corrected command voltage V2 expressed by the following formula is applied.
Corrected command voltage V2 = command voltage V0 - correction value [actual voltage V1 - command voltage V0]
The corrected command voltage V2 thus obtained is output to the voltage application circuit 201, so that the actual applied voltage becomes the original command voltage V0. This suppresses the decomposition reaction of _H2O in the pump cell 1p and reduces the variations in the sensor cell current Is and the monitor cell current Im, thereby reducing the NOx output error.

Claims

A sensor element (1) that detects NOx contained in the gas to be measured (G), a heater (H) that heats the sensor element, and controls the operation of the sensor element and the heater, and A NOx sensor (S) comprising a sensor control unit (10) that calculates a NOx concentration based on a signal,
The above sensor element is
A gas to be measured chamber (2) into which the gas to be measured is introduced via a gas introduction part (3) and has a solid electrolyte body (11) as a chamber wall;
A first cell (1p) that is arranged in the upstream side of the gas flow to be introduced in the measurement gas chamber and outputs a first signal (Ip) that has a correlation with the H ₂ O concentration in the measurement gas; , a second cell (1s) that is disposed downstream of the first cell and outputs a second signal (Is) according to the NOx concentration and H ₂ O concentration in the gas to be measured. Ori,
The above sensor control section is
a NOx concentration reference value calculation unit (101) that calculates a NOx concentration reference value (C1) based on the second signal;
an H _{2 O concentration information detection unit (102) that detects H 2} O concentration or H ₂ O concentration information (Ci) including concentration information having a correlation with the H ₂ O concentration, based on the first signal or _external information; ,
a NOx concentration correction unit (103) that offset-corrects the NOx concentration reference value based on the H ₂ O concentration information;
a detection control unit (200) that controls voltages applied to the first cell and the second cell ;
The NOx concentration correction section calculates offset correction information of the second signal corresponding to the H ₂ O concentration information based on the output characteristics of the sensor element acquired at a predetermined reference environmental temperature (T0). The reference environmental temperature is set to a steady temperature range of the gas to be measured in the environment in which the sensor element is mounted;
The detection control section includes a voltage application circuit (201) that generates a voltage according to an instruction voltage (V0) input from a voltage application instruction section (202), and an instruction voltage correction section (203), and includes an instruction voltage correction section (203). The voltage correction section includes a voltage detection section (203a) that detects the actual voltage (V1) generated by the voltage application circuit, and corrects the indicated voltage based on a difference value between the indicated voltage and the actual voltage. A NOx sensor, comprising a correction value calculation unit (203b) .

The sensor element is installed in an exhaust gas passage (EX) of the internal combustion engine through which the gas to be measured is discharged, and the steady temperature range is determined when the sensor element is installed when the internal combustion engine is in a steady operating state. The NOx sensor according to claim 1, wherein the temperature range of the gas to be measured that reaches the position is within a possible temperature range.

The NOx sensor according to claim 1 or 2, wherein the reference environmental temperature is set in a temperature range higher than the lower limit temperature of the steady temperature range.

The above reference environmental temperature is based on the output characteristics obtained by the sensor element in a low temperature range including the lower limit temperature of the above steady temperature range, and the output characteristic obtained by the above sensor element in a high temperature range including the upper limit temperature of the above steady temperature range. The NOx sensor according to any one of claims 1 to 3, wherein the NOx sensor is set to a reference temperature range exhibiting an intermediate output characteristic.

The NOx sensor according to any one of claims 1 to 4, wherein the reference environmental temperature is set in a range of 300°C or more and 700°C or less.

The NOx sensor according to any one of claims 1 to 4, wherein the offset correction information is information based on output characteristics individually acquired for the sensor element.

The NOx sensor according to claim 1, wherein the offset correction information is information obtained by averaging a plurality of output characteristics obtained for a plurality of the sensor elements.

The NOx sensor according to any one of claims 1 to 7, wherein in the voltage application instruction section, the instruction voltage is set within a range that can suppress a decomposition reaction of H ₂ O in the first cell .