JP6981121B2 - Exhaust information processing device, exhaust information processing system and exhaust information processing program - Google Patents

Description

The present disclosure relates to a technique for processing the output of an exhaust sensor that detects nitrogen oxides.

Conventionally, for example, Patent Document 1 discloses an engine control device that detects nitrogen oxides contained in exhaust gas by a NOx sensor and measures the concentration of nitrogen oxides contained in exhaust gas. It is known that the output of such NOx sensors changes with continuous use. Therefore, the engine control device has a function of correcting the output of the NOx sensor.

More specifically, the engine control device of Patent Document 1 acquires the NOx concentration detected by the NOx sensor (hereinafter referred to as “detection concentration”), and at the same time, the concentration of nitrogen oxides contained in the exhaust gas from the operating state of the engine. (Hereinafter, "estimated concentration") is estimated. The engine control device calculates the output characteristic of the NOx sensor in the deteriorated state by associating the detected concentration with the estimated concentration when the estimated concentration is in a relatively high specific state.

Japanese Unexamined Patent Publication No. 2002-47779

By the way, in Patent Document 1, the mechanism of deterioration caused by the NOx sensor is not specified at all. Therefore, the engine control device simply corrects the output of the NOx sensor in the deteriorated state by mathematical processing such as linear interpolation from the correspondence between the estimated concentration and the detected concentration. Therefore, it is difficult for the detected density after correction to correctly reflect the deterioration state of the detection unit in the NOx sensor. Therefore, when the information used for the correction is small, it may be difficult to specify the detection characteristics of the detection unit in the deteriorated state, and it may be difficult to secure the accuracy of the detected concentration after the correction.

An object of the present disclosure is to provide a processing technique for exhaust information that can accurately identify the detection characteristics of a detection unit in a deteriorated state even if the information used for correction is small.

In order to achieve the above object, one disclosed aspect is a detection unit (53) for detecting nitrogen oxides contained in the exhaust gas of the engine (1) and an inhibitor (68) for inhibiting the reduction of nitrogen oxides. An exhaust information processing device that processes the output of an exhaust sensor (50, 60) having an exhaust unit (51) that contains Au as () and removes oxygen contained in the exhaust gas toward the detection unit, and nitrogen oxides. A signal acquisition unit (31) that acquires a concentration signal indicating the concentration of an object from a detection unit, and a concentration estimation unit (32) that estimates the concentration of nitrogen oxides contained in exhaust gas based on operation information indicating the operating state of the engine. And, the detection characteristic of the detection unit related to the concentration of nitrogen oxides contained in the exhaust gas, and the characteristic storage that stores the reference data of the detection characteristic that changes due to the adhesion of the inhibitor detached from the exhaust gas to the detection unit. The reference data stored in the characteristic storage unit is corrected using the relationship between the unit (33), the detected concentration indicated by the concentration signal, and the estimated concentration estimated by the concentration estimation unit, and the deterioration state due to the adhesion of the inhibitor is obtained. It is an exhaust information processing apparatus including a characteristic calculation unit (34) for calculating the detection characteristics of the detection unit.

Further, one embodiment contains a detection unit (53) for detecting nitrogen oxides contained in the exhaust gas of the engine (1) and Au as an inhibitor (68) for inhibiting the reduction of nitrogen oxides. An exhaust sensor (50, 60) having an exhaust unit (51) for removing oxygen contained in the exhaust gas toward the head, a signal acquisition unit (31) for acquiring a concentration signal indicating the concentration of nitrogen oxides from the detection unit, and an engine. It is the detection characteristic of the concentration estimation unit (32) that estimates the concentration of nitrogen oxides contained in the exhaust gas based on the operation information indicating the operating state of, and the detection unit related to the concentration of nitrogen oxides contained in the exhaust gas. , The characteristic storage unit (33) that stores the reference data of the detection characteristics that change due to the adhesion of the inhibitor detached from the discharge unit to the detection unit, and the detection concentration indicated by the concentration signal and the estimated concentration estimated by the concentration estimation unit. It has a characteristic calculation unit (34), which corrects the reference data stored in the characteristic storage unit using the relationship with and calculates the detection characteristics of the detection unit in a deteriorated state due to the adhesion of an inhibitor, and has an exhaust sensor. It is an exhaust information processing system including an exhaust information processing device (100) for processing an output.

Further, one embodiment contains a detection unit (53) for detecting nitrogen oxides contained in the exhaust gas of the engine (1) and Au as an inhibitor (68) for inhibiting the reduction of nitrogen oxides. It is an exhaust information processing program that processes the output of an exhaust sensor (50, 60) having an exhaust unit (51) that removes oxygen contained in the exhaust gas toward the exhaust gas, and at least one control unit (30) is nitrogen oxide. A signal acquisition unit (31) that acquires a concentration signal indicating the concentration of oxides from the detection unit, and a concentration estimation unit (32) that estimates the concentration of nitrogen oxides contained in exhaust gas based on operation information indicating the operating state of the engine. , A characteristic storage unit that stores the reference data of the detection characteristics that are the detection characteristics of the detection unit related to the concentration of nitrogen oxides contained in the exhaust gas and that change due to the adhesion of the inhibitor detached from the exhaust gas to the detection unit. (33), and the reference data stored in the characteristic storage unit is corrected using the relationship between the detected concentration indicated by the concentration signal and the estimated concentration estimated by the concentration estimation unit, and the deterioration state due to the adhesion of the inhibitory substance is corrected. It is an exhaust information processing program that functions as a characteristic calculation unit (34) that calculates the detection characteristics of the detection unit.

The inventors of the present disclosure have found that the main cause of deterioration of the detection unit is the adhesion of an inhibitor detached from the exhaust unit that removes oxygen from the exhaust gas to the detected substance. The inhibitory substance adhered to the detection unit in this way substantially reduces the contact area between the exhaust gas and the detection unit, and causes a change in the detection characteristics of the detection unit related to the concentration of nitrogen oxides.

As described above, since the mechanism of deterioration of the detection unit can be specified, the change in the detection characteristics of the detection unit can be estimated in advance. Therefore, in each aspect of the present disclosure, the reference data of the detection characteristic changed by the adhesion of the inhibitor is stored in the characteristic storage unit. In addition, the progress of deterioration of the detection unit can be grasped by the characteristic calculation unit from the relationship between the detected concentration and the estimated concentration. Then, the characteristic calculation unit calculates the detection characteristic reflecting the deterioration state of the current detection unit by correcting the reference data. Based on the above, the calculated detection characteristics can be contents that correctly reflect the deterioration state of the detection unit. Therefore, even if the amount of information used for correction is small, the detection characteristics of the detection unit in the deteriorated state can be accurately specified.

The reference numbers in parentheses are merely examples of the correspondence with the specific configuration in the embodiment described later, and do not limit the technical scope at all.

It is an overall view which shows the whole structure of the engine and the exhaust system to which the engine control system by 1st Embodiment is applied. It is a block diagram which shows the electrical composition of an engine control system. It is sectional drawing which shows the mechanical structure of the oxygen discharge part and NOx detection part in a NOx sensor. It is a figure which shows the detection characteristic of a NOx detection part. It is a schematic diagram for demonstrating the mechanism of deterioration of a NOx detection part. It is a figure which shows the correspondence relationship between the actual NOx concentration and NOx detection rate, and is the figure which shows the reference characteristic data and the correction characteristic data of a NOx detection unit. It is a figure which shows the reference correction data and density correction data. It is a flowchart which shows the detail of the deterioration detection processing performed in the control circuit. It is a flowchart which shows the detail of the NOx measurement processing carried out in a control circuit. It is a figure for demonstrating the execution timing of the deterioration detection process. It is a figure which shows the relationship between the error assumed in the comparative example which a correction process is not performed, and the size of a margin with respect to an allowable upper limit value. It is a figure which shows the relationship between the error in the 1st Embodiment in which a correction process is carried out, and the size of a margin with respect to an allowable upper limit value. It is a figure for demonstrating the effect by a correction process. It is a figure which shows typically the state of the exhaust gas when the structure of a post-treatment apparatus is simplified as the effect of a correction process. It is a figure which shows typically the state of the exhaust gas when the fuel consumption is improved as the effect of the correction process. It is a figure explaining the calculation method of the 2nd Embodiment which calculates the correction characteristic data from the reference characteristic data. It is a figure which shows the reference correction data and density correction data of 2nd Embodiment. It is a figure which shows the detection rate map used in 3rd Embodiment. It is a figure which shows the engine control system of the modification 1. It is a figure which shows the engine control system of the modification 2.

Hereinafter, a plurality of embodiments will be described with reference to the drawings. By assigning the same reference numerals to the corresponding components in each embodiment, duplicate description may be omitted. When only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other parts of the configuration. Further, not only the combination of the configurations specified in the description of each embodiment but also the configurations of a plurality of embodiments can be partially combined even if the combination is not specified. Further, a combination of configurations described in a plurality of embodiments and modifications is also disclosed by the following description.

(First Embodiment)
The engine control system 10 according to the first embodiment shown in FIGS. 1 and 2 is mounted on a vehicle together with an internal combustion engine. The internal combustion engine is a compression self-ignition type diesel engine (hereinafter, "engine 1"), and is a power source for driving a vehicle. The engine 1 generates power by burning light oil. The exhaust pipe 3 connected to the engine 1 is provided with an aftertreatment device such as an oxidation catalyst 2 and an SCR (Selective Catalytic Reduction) catalyst 4.

The engine control system 10 is a system that controls the engine 1. The engine control system 10 has a function of measuring the concentration of nitrogen oxides (hereinafter, “NOx”) contained in the exhaust gas flowing through the exhaust pipe 3. The engine control system 10 includes two NOx sensors 50 and 60 and a control unit 100.

The NOx sensors 50 and 60 are provided at different positions in the exhaust pipe 3. The NOx sensor 50 is located on the upstream side (engine 1) of the NOx sensor 60 and is arranged between the oxidation catalyst 2 and the SCR catalyst 4. The NOx sensor 50 is located closer to the oxidation catalyst 2 than the SCR catalyst 4, and detects NOx contained in the exhaust gas that has passed through the oxidation catalyst 2. The NOx sensor 60 is located downstream of the NOx sensor 50 and the SCR catalyst 4, and is arranged between the SCR catalyst 4 and the outlet of the exhaust pipe 3. The NOx sensor 60 detects NOx contained in the exhaust gas that has passed through the SCR catalyst 4.

The NOx sensors 50 and 60 shown in FIGS. 2 and 3 are provided with sensor elements for detecting NOx. The sensor element is composed of a solid electrolyte 61, a spacer 62, a reference electrode 63, a pump electrode 64, a sensor electrode 65, and the like.

The solid electrolyte 61 is formed in a rectangular plate shape by a solid electrolyte material such as yttria-stabilized zirconia (YSZ). The solid electrolyte 61 exhibits the conductivity of oxygen ions at a high temperature, specifically, in the case of YSZ, at a temperature of about 600 ° C. or higher. A pump electrode 64 and a sensor electrode 65 are provided on the first surface of the solid electrolyte 61. A reference electrode 63 is provided on the second surface of the solid electrolyte 61, which is opposite to the first surface.

The spacer 62 is formed of an electrically insulating material such as _{alumina (Al 2} O _3). The spacer 62 is laminated on the front surface side of the solid electrolyte 61. A gas chamber 57 and an introduction port 59 are partitioned between the spacer 62 and the solid electrolyte 61. Exhaust gas flowing through the exhaust pipe 3 (see FIG. 1) is introduced into the gas chamber 57 through the introduction port 59.

The reference electrode 63 is formed of a conductive material containing Pt, for example, in the form of a rectangular thin film of about 10 μm. The reference electrode 63 is arranged on the second surface of the solid electrolyte 61. The reference electrode 63 overlaps with both the pump electrode 64 and the sensor electrode 65 with the solid electrolyte 61 sandwiched therein.

The pump electrode 64 is formed of a conductive material containing Au and Pt in a rectangular thin film shape of, for example, about 10 μm. Au contained in the pump electrode 64 is an inhibitor 68 (see FIG. 5) that inhibits the reducing action of NOx by the pump electrode 64. The pump electrode 64 has a reduced ability to decompose NOx molecules due to the inclusion of Au. On the other hand, the pump electrode 64 exhibits a reducing action on oxygen molecules. The pump electrode 64 is located on the downstream side of the introduction port 59 and on the upstream side of the sensor electrode 65 in the gas flow direction F. The pump electrode 64 forms an oxygen discharge portion 51 together with the solid electrolyte 61, the reference electrode 63, and the like.

The oxygen discharge unit 51 exerts a function of adjusting the oxygen concentration contained in the exhaust gas to be the measured gas. More specifically, a predetermined voltage is applied between the pump electrode 64 and the reference electrode 63 by the control unit 100. Under the state where a voltage is applied, oxygen molecules in the gas to be measured introduced into the gas chamber 57 are adsorbed on the adsorption surface 64a which is the noble metal surface of the pump electrode 64, and are reduced and decomposed into oxygen ions. .. Oxygen ions are conducted from the pump electrode 64 to the solid electrolyte 61 and moved to the reference electrode 63. By the above pumping action, the oxygen discharge unit 51 removes at least a part, preferably all of the oxygen molecules contained in the gas to be measured, and adjusts the oxygen concentration in the gas to be measured.

The sensor electrode 65 is formed in the form of a rectangular thin film of, for example, about 10 μm by a conductive material having an enhanced decomposition activity ability for NOx molecules by containing Pt and Rh (rhodium). The sensor electrode 65 exhibits a catalytic action on NOx molecules. The sensor electrode 65 is provided on the surface of the solid electrolyte 61 facing the gas chamber 57. The sensor electrode 65 is located downstream of the pump electrode 64 in the gas flow direction F. The sensor electrode 65 forms a NOx detection unit 53 together with the solid electrolyte 61, the reference electrode 63, and the like.

The NOx detection unit 53 exerts a function of detecting NOx contained in the exhaust gas as the gas to be measured. More specifically, a predetermined voltage is applied between the sensor electrode 65 and the reference electrode 63 by the control unit 100. Under a voltage applied state, NOx molecules in the gas to be measured introduced into the gas chamber 57 are adsorbed on the detection surface 65a, which is the noble metal surface of the sensor electrode 65, and are catalyzed into nitrogen ions and oxygen ions. Is decomposed into. Oxygen ions are conducted from the sensor electrode 65 to the solid electrolyte 61 and moved to the reference electrode 63 to generate a sensor current. The NOx detection unit 53 outputs the magnitude of the sensor current that increases or decreases according to the amount of oxygen ions to the control unit 100 as a concentration signal indicating the concentration of NOx contained in the gas to be measured.

Here, the value obtained by dividing the NOx concentration detected by the NOx detection unit 53 by the actual NOx concentration in the measured gas is defined as the NOx detection rate. As shown in FIG. 4, the NOx detection rate is a value that is substantially uniquely determined by the ratio (NOx concentration / effective area) of the NOx concentration in the gas to be measured and the effective area of the detection surface 65a. The NOx detection rate is substantially "1" in the region where the ratio of the NOx concentration to the effective area is lower than the predetermined value, and when the ratio of the NOx concentration to the effective area exceeds the predetermined value, the ratio increases. Gradually decrease.

Then, the NOx detection rate decreases due to deterioration of the NOx sensors 50 and 60. The main factor is the inhibitor 68 shown in FIG. The inhibitor 68 separates from the suction surface 64a of the pump electrode 64 and adheres to the sensor electrode 65 located on the downstream side in the gas flow direction F to form a film on the detection surface 65a. The coating with the inhibitor 68 inhibits the NOx reduction reaction at the sensor electrode 65. Such a mechanism causes a substantial reduction in the effective area of the detection surface 65a by the inhibitor 68. As a result, as shown in FIG. 4, the ratio of the NOx concentration to the effective area increases due to the transition from the initial state to the deteriorated state, which causes a decrease in the NOx detection rate.

The control unit 100 shown in FIGS. 1 and 2 can correct the decrease in the NOx detection rate due to deterioration as a part of the function of processing the outputs of the NOx sensors 50 and 60. The control unit 100 includes a control circuit 30 mainly composed of a microcomputer or a microcontroller. The control circuit 30 is provided with a processor, RAM, and a rewritable non-volatile memory device. The control unit 100 is directly or indirectly electrically connected to the NOx sensors 50 and 60. The control unit 100 constructs a plurality of functional blocks that process the outputs of the NOx sensors 50 and 60 by executing the exhaust information processing program stored in the memory device by the processor. Specifically, the control unit 100 is constructed with a signal acquisition unit 31, a concentration estimation unit 32, a characteristic storage unit 33, a characteristic calculation unit 34, a concentration calculation unit 35, an update control unit 36, and the like.

The signal acquisition unit 31 controls to apply a voltage to each NOx detection unit 53 and each oxygen discharge unit 51 of the NOx sensors 50 and 60. The signal acquisition unit 31 acquires the value of the sensor current of each NOx detection unit 53 as a density signal.

The concentration estimation unit 32 acquires information such as a fuel injection amount, an injection timing, an injection pattern, an intake amount, an EGR rate, an intake temperature, and a water temperature as engine operation information indicating an operating state of the engine 1. The concentration estimation unit 32 estimates the NOx concentration contained in the exhaust gas (hereinafter, “estimated NOx concentration”) based on these engine operation information. For example, the fuel injection amount can be estimated with high accuracy from the value of the pressure sensor provided in the injector, the waveform of the drive signal applied to the injector, and the like. Further, the concentration estimation unit 32 can estimate the purification rate of NOx by the oxidation catalyst 2 and the SCR catalyst 4, and individually calculates the estimated NOx concentration of the exhaust gas reaching each of the NOx sensors 50 and 60. The estimated NOx concentration calculated in this way is a value that is not based on the outputs of the NOx sensors 50 and 60.

The characteristic storage unit 33 includes reference characteristic data showing the detection characteristics of the NOx detection unit 53 (see the solid line in FIG. 6) and reference correction data for correcting the density signal to calculate the actual NOx concentration (see the solid line in FIG. 7). I remember. The reference characteristic data is data showing the detection characteristics related to the NOx concentration, and specifically, the data showing the correspondence between the NOx concentration contained in the exhaust gas and the NOx detection rate. The reference correction data is data showing the correspondence between the NOx concentration (hereinafter, “detected NOx concentration”) indicated by the concentration signal acquired by the signal acquisition unit 31 and the actual NOx concentration. Each data shows the correlation in the initial state in which the NOx detection unit 53 is not deteriorated. The characteristics of the NOx detection unit 53 shown in each data are changed by the adhesion of the inhibitor 68 separated from the adsorption surface 64a to the detection surface 65a. The format of each data may be a map or a model formula showing an approximate curve.

The characteristic calculation unit 34 estimates the progress of deterioration of the NOx sensors 50 and 60, and executes deterioration determination processing for correcting both the reference characteristic data and the reference correction data stored in the characteristic storage unit 33 (see FIG. 8). .. First, the characteristic calculation unit 34 corrects the detection NOx concentration at the zero point (see FIG. 8S11). More specifically, the characteristic calculation unit 34 describes the concentration signal so that the NOx detection rate becomes "1" or the detected NOx concentration becomes cello under the condition that the actual NOx concentration becomes substantially zero. Offset the values (see Figure 6 and Figure 7 alternate long and short dash line).

The characteristic calculation unit 34 acquires the detected NOx concentration D1 indicated by the concentration signal and the estimated NOx concentration E1 estimated by the characteristic storage unit 33 under specific conditions (see FIGS. 8S12 and S13). The characteristic calculation unit 34 calculates the current NOx detection rate R1 (= D1 / E1) based on these sets of detected NOx concentration D1 and estimated NOx concentration E1 (see FIG. 8S14). The characteristic calculation unit 34 transforms the reference characteristic data so as to pass through the intersection point of the estimated NOx concentration E1 and the NOx detection rate R1. The detection characteristic thus obtained becomes the correction characteristic data indicating the current detection characteristic of the NOx detection unit 53 (in the deteriorated state) (see the broken line in FIG. 6).

Further, the characteristic calculation unit 34 corrects the reference correction data based on the correction characteristic data. Specifically, the characteristic calculation unit 34 calculates the NOx concentration E2 (see FIG. 8S15) that takes the NOx detection rate R1 from the reference characteristic data, and the deterioration correction coefficient K (= E1 /) indicating the rate of change with deterioration. The calculation of E2) (see FIG. 8S16) is carried out in order. The characteristic calculation unit 34 multiplies the horizontal axis (detection NOx concentration axis) of the reference correction data indicating the initial characteristics by the deterioration correction coefficient K (see FIG. 8S17). As a result, concentration correction data (see the broken line in FIG. 7) showing the correspondence between the detected NOx concentration in the current deteriorated state and the actual NOx concentration is generated (see FIG. 8S18). The characteristic calculation unit 34 individually generates density correction data associated with each NOx detection unit 53 of the NOx sensors 50 and 60. In the first embodiment, the density correction data is stored in the memory device as information in the map format. Therefore, in the following description, the density correction data will be referred to as a “correction map”. The density correction data may be a model formula or the like in the same manner as the above-mentioned reference correction data or the like.

The concentration calculation unit 35 carries out a NOx measurement process (see FIG. 9) for calculating the NOx concentration contained in the exhaust gas (hereinafter, “corrected NOx concentration”) during the period in which the engine 1 is operating. The concentration calculation unit 35 acquires the detected NOx concentration based on the concentration signal of each NOx detection unit 53 (see FIG. 9S21), applies each detected NOx concentration to each correction map, and calculates the corrected NOx concentration (FIG. 9). 9 See S22). By repeating the above processing, the NOx concentration at each measurement point where the NOx sensors 50 and 60 are arranged is continuously calculated. The detected NOx concentration is a value to which the above-mentioned correction of the zero point position is applied.

The update control unit 36 controls the execution timing of deterioration correction by the characteristic calculation unit 34 and the like, that is, the timing of updating the reference correction data and the correction map (density correction data). The update control unit 36 is a deterioration detection process for updating the reference correction data and the correction map (concentration correction data) in a state where the engine 1 is sufficiently warmed up and the engine 1 is in a steady operation, for example. To execute. The execution interval of the deterioration detection process is determined based on the preset operation information. When the operation time is used as the operation information, as shown in FIG. 10, the update control unit 36 performs the deterioration detection process when the integrated operation time counted from the previous execution of the deterioration detection process exceeds the execution determination threshold value th. To be carried out. The execution interval of the deterioration detection process may not be constant, and may be set to an unequal interval by increasing or decreasing the execution determination threshold value th.

As described above, since the mechanism of deterioration of the NOx detection unit 53 can be specified, the change in the detection characteristics of the NOx detection unit 53 can be estimated in advance. Specifically, in the first embodiment, the reference characteristic data of the detection characteristic that changes due to the adhesion of the inhibitor 68 is stored in the characteristic storage unit 33. In addition, the progress of deterioration of the NOx detection unit 53 is grasped by the characteristic calculation unit 34 from the relationship between the detected NOx concentration and the estimated NOx concentration. Then, the characteristic calculation unit 34 calculates the correction characteristic data indicating the detection characteristic reflecting the deterioration state of the current NOx detection unit 53 by correcting the reference characteristic data. Based on the above, the correction characteristic data can be a content that correctly reflects the deterioration state of the NOx detection unit 53. Therefore, even if the amount of information used for correction is small, the detection characteristics of the NOx detection unit 53 in the deteriorated state can be accurately specified.

In addition, in the first embodiment, as the data showing the detection characteristics of the NOx detection unit 53, the reference characteristic data showing the correspondence relationship between the actual NOx concentration and the NOx detection rate is stored. As described above, the decrease in the effective area due to the adhesion of the inhibitor 68 directly affects the value of the NOx detection rate with respect to the actual NOx concentration. Therefore, in the process of identifying the change in the detection characteristics of the NOx detection unit 53 while reflecting the newly found mechanism of deterioration due to the adhesion of the inhibitor 68, the above-mentioned corresponding relationship between the actual NOx concentration and the NOx detection rate is shown. It is preferable to use the reference characteristic data of.

Further, the concentration calculation unit 35 of the first embodiment corrects the detected NOx concentration using the correction map generated by using the correction characteristic data, and calculates the corrected NOx concentration. As described above, if the detected NOx concentration is corrected using the correction map that reflects the detection characteristics in the deteriorated state, the error between the corrected NOx concentration and the actual NOx concentration can be reduced. As described above, the advantage of being able to accurately correct the deterioration of the NOx sensors 50 and 60 will be described with reference to FIGS. 11 to 15.

In the comparative example according to the prior art shown in FIG. 11, the correction process reflecting the change in the detection characteristic is not performed. Therefore, the error of the detected NOx concentration with respect to the actual NOx concentration increases with the accumulation of the usage time of the NOx sensor. Therefore, the target control value of the aftertreatment device should be such that the detected NOx concentration is below the allowable upper limit value, including the margin and the error amount, so that the actual NOx concentration is lower than the allowable upper limit value (for example, the legal regulation value). , I had to set it to a value considerably lower than the allowable upper limit.

However, as shown in FIG. 12, according to the correction process based on the correction map, the error between the corrected NOx concentration and the actual NOx concentration can be reduced. As a result, the actual NOx concentration can be changed to a value far below the allowable upper limit value. Therefore, as shown in FIG. 13, even if the target control value of the processing device is set to a value closer to the allowable upper limit value than that of the comparative example (see FIG. 11), it is possible to secure a margin equivalent to that of the comparative example. .. Such relaxation of the target control value can contribute to simplification of the aftertreatment device and improvement of fuel efficiency.

More specifically, as shown in FIG. 14, if the NOx emission amount can be mitigated by performing the correction process, the performance of the aftertreatment device can be lowered. Specifically, the catalyst sizes of the oxidation catalyst 2 and the SCR catalyst 4 can be reduced. Further, the consumption of the reducing agent such as urea water supplied to the SCR catalyst 4 and the fuel supplied to the LNT catalyst occluding NOx can be reduced. As a result, the effect of suppressing the initial cost and running cost related to the aftertreatment device can be obtained.

On the other hand, when the purification performance of the aftertreatment device is maintained, as shown in FIG. 15, the effect of improving the accuracy can be used to improve the output of the engine 1. Specifically, by controlling the injection timing of the injector to be adapted to the advance angle side, it is possible to improve fuel efficiency while allowing an increase in NOx.

Further, by assuming a reduction in the effective area of the detection surface 65a in advance, it is possible to design the NOx detection unit 53 on the premise of deterioration. That is, the NOx detection unit 53 in which the area of the detection surface 65a is smaller than the conventional one can be realized. Further, if deterioration can be detected and corrected, the product life assumed for the NOx sensor can be extended.

In addition, in the first embodiment, the corrected NOx concentration is calculated by the process of applying the detected NOx concentration to the correction map generated using the correction characteristic data. According to such processing, the control unit 100 can perform an operation of acquiring a highly accurate corrected NOx concentration from the density signal with a low load.

Further, in the first embodiment, the correction characteristic data is calculated from the reference characteristic data by using the relationship between the set of detected NOx and the estimated NOx concentration. By such processing, it becomes possible to specify the detection characteristics of the NOx detection unit 53 in the deteriorated state with a low load and high speed.

Further, in the first embodiment, the NOx sensors 50 and 60 are corrected so that the detected NOx concentration indicated by the concentration signal is zero under the condition that the concentration of the nitrogen oxide is substantially zero. After performing such zero point correction, the characteristic calculation unit 34 calculates the correction characteristic data from the reference characteristic data. Based on the above, the correction characteristic data can be a content that more accurately reflects the detection characteristics of the NOx detection unit 53 in the deteriorated state.

In the first embodiment, the engine 1 corresponds to the "engine", the control circuit 30 corresponds to the "control unit", and the concentration calculation unit 35 corresponds to the "concentration correction unit". Further, the NOx sensors 50 and 60 correspond to the "exhaust sensor", the oxygen discharge unit 51 corresponds to the "exhaust unit", and the NOx detection unit 53 corresponds to the "detection unit". Further, the engine control system 10 corresponds to the "exhaust information processing system", and the control unit 100 corresponds to the "exhaust information processing device". Then, the reference characteristic data corresponds to the "reference data", the concentration correction data corresponds to the "correction data", the detected NOx concentration corresponds to the "detection concentration", and the estimated NOx concentration corresponds to the "estimated concentration".

(Second embodiment)
The characteristic calculation unit 34 of the second embodiment acquires a concentration signal in a state where the operating conditions of the engine are changed in the deterioration detection process. As a result, as shown in FIG. 16, the characteristic calculation unit 34 acquires a plurality of sets (two sets) of the detected NOx concentrations D1 and D2 and the estimated NOx concentrations E21 and E22 as information for correction. The characteristic calculation unit 34 calculates the NOx detection rates R1 (= D1 / E21) and R2 (= D2 / E22) for each set of information, and coordinates P1 (E21, R1) and P2 (E22, R2). Is specified. Then, the characteristic calculation unit 34 reduces the reference characteristic data in the horizontal axis (NOx concentration axis) direction, and searches for a scale value that minimizes the square error between the reduced data lines and the coordinates P1 and P2. do. The characteristic calculation unit 34 acquires the data line having the minimum squared error with each of the coordinates P1 and P2 as the correction characteristic data indicating the current detection characteristic, and obtains the scale ratio of the correction characteristic data with respect to the reference characteristic data. The deterioration correction coefficient K is used.

As shown in FIG. 17, the characteristic calculation unit 34 multiplies the horizontal axis (detection NOx concentration axis) of the reference correction data indicating the initial state by the deterioration correction coefficient K. As a result, the density correction data reflecting the detection characteristics of the NOx detection unit 53 in the deteriorated state is acquired. As described above, the concentration calculation unit 35 can calculate the corrected NOx concentration DC1 corresponding to the deteriorated state, instead of the corrected NOx concentration C1 in the initial state, for the detected NOx concentration D1.

Even in the second embodiment described so far, the control unit exerts the same effect as that of the first embodiment, accurately identifies the detection characteristics of the deteriorated NOx detection unit 53, and has an error with the actual NOx concentration. It is possible to calculate the corrected NOx concentration with a small amount of. In addition, if the information of the detected NOx concentration and the estimated NOx concentration of a plurality of sets (two sets) is used in the process of generating the correction characteristic data from the reference characteristic data as in the second embodiment, the correction characteristic data is in a deteriorated state. The detection characteristics of the NOx detection unit in the above can be shown more accurately.

(Third embodiment)
The characteristic calculation unit 34 of the third embodiment generates the detection rate map shown in FIG. 18 as “correction data” used for correcting the detected NOx concentration. The detection rate map is data showing the correspondence between the detected NOx concentration and the NOx detection rate. The characteristic calculation unit 34 generates a detection rate map that reflects the current deterioration state by multiplying the horizontal axis (detection NOx concentration axis) of the reference correction data indicating the initial state by the deterioration correction coefficient K.

The concentration calculation unit 35 applies the detected NOx concentration D1 to the detection rate map and calculates the NOx detection rate R1. The concentration calculation unit 35 calculates the corrected NOx concentration (= D1 / R1) by dividing the detected NOx concentration D1 by the NOx detection rate R1. As described above, the same effect as that of the first embodiment is exhibited in the third embodiment in which the corrected NOx concentration is calculated by using the detection rate map as the correction data.

(Fourth Embodiment)
The characteristic calculation unit 34 of the fourth embodiment generates a deterioration correction coefficient K as "correction data" used for correction of the detected NOx concentration. The concentration calculation unit 35 calculates the corrected NOx concentration by a process of applying the value (= D1 / K) obtained by dividing the detected NOx concentration by the deterioration correction coefficient K to the reference correction data (see the solid line in FIG. 7). As described above, the same effect as that of the first embodiment is exhibited in the fourth embodiment in which the corrected NOx concentration is calculated by using the deterioration correction coefficient K. Further, by adopting the above process using the deterioration correction coefficient K, it is possible to reduce the storage capacity required for correcting the detected NOx concentration. In the fourth embodiment, the deterioration correction coefficient K corresponds to the “correction coefficient”.

(Other embodiments)
Although the plurality of embodiments have been described above, the present disclosure is not construed as being limited to the above embodiments, and may be applied to various embodiments and combinations without departing from the gist of the present disclosure. can.

The engine control system 10 of the above embodiment includes a plurality of (two) NOx sensors 50 and 60. However, the number and arrangement of NOx sensors can be changed as appropriate. For example, three or more NOx sensors may be provided in the exhaust pipe. Further, the NOx sensor 50 may be provided only on the upstream side of the SCR catalyst 4, as in the engine control system 510 of the modification 1 shown in FIG. Alternatively, the NOx sensor 60 may be provided only on the downstream side of the SCR catalyst 4, as in the engine control system 610 of the second modification shown in FIG.

In the above embodiment, the reference characteristic data showing the correspondence between the actual NOx concentration and the NOx detection rate was used as the "reference data" showing the detection characteristics of the NOx detection unit 53. However, the "reference data" is not limited to such information. Further, the implementation of zero point correction for correcting the offset of the density signal may be omitted as appropriate.

The update control unit of the above embodiment uses the operation time as the operation information. However, the update control unit can use the temperature integration amount, the mileage, and the like as the operation information. The integrated temperature value is a value obtained by integrating the temperature of the exhaust gas with the operating time. Even by such processing, it is possible to update the correction characteristic data and the density correction data at appropriate timings according to the deterioration state of the NOx detection unit.

In the above embodiment, Au is described as an inhibitor contained in the oxygen discharging part. However, the inhibitor is not limited to Au. In the oxygen discharge section, a substance that suppresses the discharge of NOx from the pump electrode and may be scattered from the pump electrode to the sensor electrode may correspond to the inhibitory substance. Further, the inhibitor may be a substance contained in the pump electrode or a substance coated on the surface of the pump electrode.

In the above embodiment, the functions provided by the control circuit of the control unit can be provided by hardware and software different from those described above, or a combination thereof. For example, in the above embodiment, the concentration calculation unit corrects the detected NOx concentration using the concentration correction data, and the corrected NOx concentration is calculated. However, the NOx measurement process for calculating the corrected NOx concentration may be carried out with a configuration different from that of the control unit. Further, a control circuit dedicated to post-processing provided separately from the ECU for integrated control of engine operation may execute a part or all of deterioration detection processing and NOx measurement processing as an "exhaust information processing device". ..

Various non-transitory tangible storage media such as flash memory and hard disk can be adopted as the memory device for storing the exhaust information processing program. In addition, the storage medium for storing the exhaust information processing program is not limited to the storage medium provided in the control unit mounted on the vehicle, such as an optical disk as a copy source to the storage medium and a hard disk drive of a general-purpose computer. May be.

In the above embodiment, an example in which the correction process according to the present disclosure is applied to the engine control system and the control unit applied to the diesel engine mounted on the vehicle has been described. However, the above correction process can be applied not only to an in-vehicle engine but also to an engine control system and a control unit of an internal combustion engine or an external combustion engine mounted on a ship, a railroad vehicle, an aircraft or the like. Further, the above correction process can be applied to the engine control system and the control unit of the power generation engine.

1 engine (engine), 10,510,610 engine control system (exhaust information processing system), 30 control circuit (control unit), 31 signal acquisition unit, 32 concentration estimation unit, 33 characteristic storage unit, 34 characteristic calculation unit, 35 Concentration calculation unit (concentration correction unit), 50, 60 NOx sensor (exhaust sensor), 51 oxygen discharge unit (exhaust unit), 53 NOx detection unit (detection unit), 68 inhibitor, 100 control unit (exhaust information processing device) , K Deterioration correction coefficient (correction coefficient)

Claims (11)

The detection unit (53) that detects nitrogen oxides contained in the exhaust gas of the engine (1) and the exhaust gas that contains Au as an inhibitor (68) that inhibits the reduction of nitrogen oxides and heads toward the detection unit. An exhaust information processing device that processes the output of an exhaust sensor (50, 60) having an exhaust unit (51) for removing contained oxygen.
A signal acquisition unit (31) that acquires a concentration signal indicating the concentration of nitrogen oxides from the detection unit, and
A concentration estimation unit (32) that estimates the concentration of nitrogen oxides contained in the exhaust gas based on the operation information indicating the operating state of the engine, and
Stores reference data of the detection characteristics, which are the detection characteristics of the detection unit related to the concentration of nitrogen oxides contained in the exhaust gas, and which are changed by the adhesion of the inhibitor detached from the exhaust unit to the detection unit. Characteristic storage unit (33)
The reference data stored in the characteristic storage unit is corrected using the relationship between the detected concentration indicated by the concentration signal and the estimated concentration estimated by the concentration estimation unit, and the deterioration state due to the adhesion of the inhibitory substance is corrected. An exhaust information processing apparatus including a characteristic calculation unit (34) for calculating the detection characteristics of the detection unit. The first aspect of claim 1, wherein the characteristic storage unit stores the correspondence between the concentration of nitrogen oxides contained in the exhaust gas and the detection rate of nitrogen oxides in the detection unit as the reference data of the detection characteristics. Exhaust information processing device. Claim 1 further includes a density correction unit (35) for correcting the detection density indicated by the density signal by using the correction data reflecting the detection characteristic in the deteriorated state calculated by the characteristic calculation unit. Or the exhaust information processing apparatus according to 2. The characteristic calculation unit generates a correction map for correcting the detected density as the correction data.
The exhaust information processing apparatus according to claim 3, wherein the concentration correction unit calculates the concentration of nitrogen oxides contained in the exhaust gas by a process of applying the detected concentration to the correction map. The characteristic calculation unit generates a correction coefficient for correcting the detection density as the correction data, and generates the correction coefficient.
The exhaust information processing apparatus according to claim 3, wherein the concentration correction unit calculates the concentration of nitrogen oxides contained in the exhaust gas by a process of correcting the concentration signal using the correction coefficient. The characteristic calculation unit generates a detection rate map showing the correspondence between the detection concentration and the detection rate of nitrogen oxides as the correction data.
The exhaust information processing apparatus according to claim 3, wherein the concentration correction unit calculates the concentration of nitrogen oxides contained in the exhaust gas by a process of applying the detected concentration to the detection rate map. Any one of claims 1 to 6, wherein the characteristic calculation unit corrects the reference data using the relationship between the detection concentration and the estimated concentration of the set, and calculates the detection characteristics of the detection unit in a deteriorated state. The exhaust information processing device according to paragraph 1. Any one of claims 1 to 6, wherein the characteristic calculation unit corrects the reference data using the relationship between a plurality of sets of the detection concentration and the estimated concentration, and calculates the detection characteristics of the detection unit in a deteriorated state. The exhaust information processing device according to paragraph 1. The characteristic calculation unit corrects the output of the exhaust sensor so that the detection concentration indicated by the concentration signal indicates zero under the condition that the concentration of nitrogen oxides becomes substantially zero, and then the characteristic calculation unit is in a deteriorated state. The exhaust information processing apparatus according to any one of claims 1 to 8, wherein the detection characteristic of the detection unit is calculated. Detection unit (53), which detects nitrogen oxides contained in the exhaust gas of the engine (1),
And an exhaust sensor (50, 60) having an exhaust unit (51) containing Au as an inhibitor (68) that inhibits the reduction of nitrogen oxides and removing oxygen contained in the exhaust gas toward the detection unit.
A signal acquisition unit (31) that acquires a concentration signal indicating the concentration of nitrogen oxides from the detection unit,
Concentration estimation unit (32), which estimates the concentration of nitrogen oxides contained in the exhaust gas based on the operation information indicating the operating state of the engine.
Stores reference data of the detection characteristics, which are the detection characteristics of the detection unit related to the concentration of nitrogen oxides contained in the exhaust gas, and which are changed by the adhesion of the inhibitor detached from the exhaust unit to the detection unit. Characteristic storage unit (33),
And the reference data stored in the characteristic storage unit is corrected by using the relationship between the detected concentration indicated by the concentration signal and the estimated concentration estimated by the concentration estimation unit, and in a deteriorated state due to the adhesion of the inhibitor. An exhaust information processing device (100) having a characteristic calculation unit (34) for calculating the detection characteristic of the detection unit and processing the output of the exhaust sensor.
Exhaust information processing system equipped with. The detection unit (53) that detects nitrogen oxides contained in the exhaust gas of the engine (1) and the exhaust gas that contains Au as an inhibitor (68) that inhibits the reduction of nitrogen oxides and heads toward the detection unit. An exhaust information processing program that processes the output of an exhaust sensor (50, 60) having an exhaust unit (51) that removes contained oxygen.
At least one control unit (30)
A signal acquisition unit (31) that acquires a concentration signal indicating the concentration of nitrogen oxides from the detection unit,
Concentration estimation unit (32), which estimates the concentration of nitrogen oxides contained in the exhaust gas based on the operation information indicating the operating state of the engine.
Stores reference data of the detection characteristics, which are the detection characteristics of the detection unit related to the concentration of nitrogen oxides contained in the exhaust gas, and which are changed by the adhesion of the inhibitor detached from the exhaust unit to the detection unit. Characteristic storage unit (33),
And the reference data stored in the characteristic storage unit is corrected by using the relationship between the detected concentration indicated by the concentration signal and the estimated concentration estimated by the concentration estimation unit, and in a deteriorated state due to the adhesion of the inhibitor. An exhaust information processing program that functions as a characteristic calculation unit (34) that calculates the detection characteristics of the detection unit.

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