JP2021095889A - Exhaust emission control device - Google Patents

Abstract

To provide an exhaust emission control device capable of preventing a control error by deriving the reaction speed of an oxidation catalyst with high accuracy.SOLUTION: An exhaust emission control device 20 includes a front stage oxidation catalyst 22 for oxidizing NOx contained in exhaust gas, a selective reduction type catalyst 36 for reducing NOx contained in the exhaust gas, an injector 30 constructed to inject reductant into the exhaust gas, a NOx sensor 28 for detecting the concentration of the NOx contained in the exhaust gas, and an ECU 44 for deriving the reaction speed of the front stage oxidation catalyst 22. The ECU 44 is constructed to execute first processing for estimating a contact concentration showing a degree at which the front stage oxidation catalyst 22 is in contact with the exhaust gas at a predetermined temperature or higher and deriving a first parameter, second processing for deriving a second parameter according to a difference between an estimated value and an actually measured value for the emission control rate of the NOx, and third processing for deriving a final reaction speed by correcting a base reaction speed using the first parameter and the second parameter.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust gas purification device.

An exhaust purification device that reduces NOx contained in the exhaust gas of a diesel engine is known (see, for example, Patent Document 1). Such an exhaust purification device includes an oxidation catalyst that oxidizes NOx contained in the exhaust gas and a reduction catalyst that is arranged downstream of the oxidation catalyst and reduces NOx contained in the exhaust gas.

Japanese Unexamined Patent Publication No. 2008-133760

In the exhaust gas purification device as described above, the reaction rate in the oxidation catalyst is estimated according to the temperature, and the NOx purification rate by the NOx reduction reaction in the reduction catalyst is estimated in consideration of the estimation result. Here, with respect to the oxidation catalyst, it is difficult to estimate the reaction rate with high accuracy simply according to the temperature because there are differences in the usage state and individual differences in the oxidation ability in the first place. Since the estimation accuracy of the reaction rate of the oxidation catalyst is lowered, the estimation accuracy of the purification rate of NOx is lowered. As a result, for example, the estimated value of the NOx purification rate deviates from the measured value of the NOx purification rate based on the detection result of the NOx sensor, and there is a possibility that erroneous control is performed in the exhaust gas purification device.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust gas purification device that prevents erroneous control by deriving the reaction rate in an oxidation catalyst with high accuracy.

The exhaust purification device according to one aspect of the present invention is an exhaust purification device that purifies the exhaust gas discharged from the engine, is arranged in an exhaust passage through which the exhaust gas flows, and oxidizes NOx contained in the exhaust gas. An oxidation catalyst, a reduction catalyst arranged downstream of the oxidation catalyst in the exhaust passage and reducing NOx contained in the exhaust gas, and an exhaust passage downstream of the oxidation catalyst and upstream of the reduction catalyst. When estimating the purification rate of NOx by a NOx reduction reaction with a reduction catalyst, a reducing agent injection device configured to inject a reducing agent into the exhaust gas, a NOx sensor that detects the concentration of NOx contained in the exhaust gas, and The control unit is provided with a control unit for deriving the reaction rate of the oxidation catalyst, which is considered in the above, and the control unit estimates and estimates the contact concentration indicating the degree to which the oxidation catalyst is in contact with the exhaust gas above a predetermined temperature. The difference between the first process of deriving the first parameter according to the concentration, the estimated value of the NOx purification rate by the NOx reduction reaction with the reduction catalyst, and the measured value of the NOx purification rate based on the detection result of the NOx sensor. The second process of deriving the second parameter accordingly, and the third process of deriving the final reaction rate by correcting the reaction rate derived according to the temperature with the first parameter and the second parameter. Is configured to run.

In the exhaust gas purification device according to one aspect of the present invention, the reaction rate in the oxidation catalyst derived according to the temperature is corrected by the first parameter and the second parameter, and the final reaction rate is derived. The first parameter is a parameter according to the contact concentration indicating the degree to which the oxidation catalyst is in contact with the exhaust gas having a predetermined temperature or higher. The oxidizing power of the oxidation catalyst is highest immediately after production, and then gradually decreases as the contact concentration with the high-temperature exhaust gas increases. Therefore, by correcting the reaction rate by the first parameter in consideration of the contact concentration described above, the reaction rate can be derived with higher accuracy in consideration of the state of the oxidizing power of the oxidation catalyst. The second parameter is a parameter according to the difference between the estimated value and the actually measured value of the purification rate of NOx. By considering the above-mentioned first parameter, the reaction rate can be derived in consideration of the difference in oxidizing power based on the usage state of the oxidation catalyst (how much it is in contact with the high-temperature exhaust gas). However, since there are individual differences (individual differences in oxidizing ability) in the oxidation catalyst, there is a limit to improving the accuracy of the reaction rate only by the correction by the first parameter. In this regard, the reaction rate is actually measured by correcting the reaction rate by a parameter (second parameter) corresponding to the difference between the estimated value of the purification rate of NOx derived in consideration of the reaction rate of the oxidation catalyst and the measured value. The reaction rate can be derived with higher accuracy by making corrections according to the inherent oxidizing ability of the oxidation catalyst in consideration of the obtained information. From the above, according to the exhaust gas purification device according to one aspect of the present invention, it is possible to derive the reaction rate in the oxidation catalyst with high accuracy and prevent the occurrence of erroneous control due to the deterioration of the estimation accuracy of the NOx purification rate. it can.

The control unit may estimate the contact concentration based on the operating time of the engine. This makes it possible to easily estimate the contact concentration.

The control unit may estimate the contact concentration based on the cumulative exhaust gas flow rate that has passed through the oxidation catalyst. As a result, the contact concentration can be estimated with higher accuracy than the case where the contact concentration is simply estimated from the operating time of the engine.

The control unit may estimate the contact concentration based on the cumulative exhaust gas flow rate that has passed through the oxidation catalyst and the exhaust gas energy flow rate derived from the exhaust gas temperature. In this way, the contact concentration can be estimated with higher accuracy by considering not only the flow rate of the exhaust gas but also the temperature.

According to the present invention, erroneous control can be prevented by deriving the reaction rate in the oxidation catalyst with high accuracy.

It is a schematic block diagram of the exhaust gas purification apparatus which concerns on this embodiment. It is a flowchart which shows the reaction rate derivation process of the pre-stage oxidation catalyst performed by the exhaust gas purification apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate description is omitted.

FIG. 1 is a schematic configuration diagram of an exhaust gas purification device 20 according to the present embodiment. The exhaust gas purification device 20 shown in FIG. 1 is a device that purifies the exhaust gas discharged from the engine 10. The engine 10 is, for example, an internal combustion engine for driving a vehicle, for example, a multi-cylinder diesel engine.

The exhaust gas purification device 20 is arranged in the exhaust passage 12 of the engine 10. The exhaust gas purification device 20 is an integrated catalyst device that combines a urea SCR (Selective Catalytic Reduction) method and a DPF (Diesel Particulate Filter) method. The exhaust purification device 20 is selected from the pre-stage oxidation catalyst 22 (oxidation catalyst), DPF 24, NOx sensor 28, exhaust temperature sensor 29, injector 30 (reducing agent injection device), tank 32, and pressure feed pump 34. It is configured to include a reduction catalyst 36 (reduction catalyst), a post-stage oxidation catalyst 40, and an ECU 44 (control unit). Of each configuration, at least the first-stage oxidation catalyst 22, the DPF 24, the selective reduction catalyst 36, and the second-stage oxidation catalyst 40 are arranged in the exhaust passage through which the exhaust gas flows. The exhaust gas that has flowed into the exhaust purification device 20 first flows into the pre-stage oxidation catalyst 22.

The pre-stage oxidation catalyst (DOC: Diesel Oxidation Catalyst) 22 is an oxidation catalyst having a known constitution, and for example, a metal such as platinum or palladium, a metal oxide or the like is supported on a carrier made of alumina, silica, zirconia, zeolite or the like. It is composed of the catalysts. The first-stage oxidation catalyst 22 oxidizes hydrocarbons (HC) and nitric oxide (NO) contained in the exhaust gas to water (H ₂ O), carbon dioxide (CO ₂ ), nitrogen dioxide (NO ₂ ), and the like. Convert. In this way, the pre-stage oxidation catalyst 22 oxidizes NOx contained in the exhaust gas.

The oxidizing power of the pre-stage oxidation catalyst 22 changes depending on the temperature. The oxidizing power of the pre-stage oxidation catalyst 22 depends on the state of use, specifically, the contact concentration indicating the degree of contact with the exhaust gas at a predetermined temperature (for example, around 180 ° C. at which the pre-stage oxidation catalyst 22 starts to be activated) or higher. Change. The oxidizing power of the pre-stage oxidation catalyst 22 is highest in the state immediately after production, and then gradually decreases as the contact concentration with the high-temperature exhaust gas increases. This is because the metals (platinum, etc.) of the pre-stage oxidation catalyst 22 stick to each other when they come into contact with the high-temperature exhaust gas, and the region that exerts the function as a catalyst becomes smaller. In addition, the oxidizing power of the pre-stage oxidation catalyst 22 varies from individual to individual.

The DPF (Diesel particulate filter) 24 is a filter that is disposed downstream of the pre-stage oxidation catalyst 22 and upstream of the selective reduction catalyst 36 and collects PM (particulate matter) contained in the exhaust gas. .. The DPF 24 is composed of, for example, a ceramic or a metal porous body.

The exhaust temperature sensor 29 detects the temperature in the exhaust passage 12 downstream of the DPF 24 at a predetermined control cycle. The exhaust temperature sensor 29 outputs a signal indicating the detected temperature to the ECU 44.

The injector 30 is configured to be capable of injecting a reducing agent into the exhaust gas flowing through the exhaust passage 12 on the downstream side of the pre-stage oxidation catalyst 22 and the DPF 24 and on the upstream side of the selective reduction catalyst 36. The urea water in the tank 32 is pumped to the injector 30 by the pump 34. The pressure feed pump 34 has a built-in relief valve (not shown), and pumps the urea water in the tank 32 to the injector 30 at a predetermined pressure. The injector 30 is opened and closed controlled by the ECU 44. The urea water supplied to the exhaust gas is hydrolyzed to ammonia by the heat of the exhaust gas.

The selective reduction catalyst 36 is arranged downstream of the pre-stage oxidation catalyst 22, DPF 24, and injector 30 in the exhaust passage 12, and selectively catalytic reduction that reduces NOx contained in the exhaust gas with ammonia. )I do. The selective reduction catalyst 36 is, for example, a carrier made of honeycomb-shaped ceramic on which highly adsorptive zeolite or zirconia is supported. NOx in the exhaust gas reacts with ammonia by the catalytic action of the selective reduction catalyst 36 and is reduced to nitrogen and water.

The post-stage oxidation catalyst 40 is disposed downstream of the selective reduction catalyst 36 in the exhaust passage 12, and decomposes ammonia that has not been consumed in the reduction reaction in the selective reduction catalyst 36. The latter-stage oxidation catalyst 40 is a carrier made of, for example, alumina, silica, zeolite, etc., on which a metal such as platinum or palladium, a metal oxide, or the like is supported.

The NOx sensor 28 is arranged on the downstream side of the post-stage oxidation catalyst 40 in the exhaust passage 12, for example, and detects the concentration of NOx contained in the exhaust gas at a predetermined control cycle. The NOx sensor 28 outputs a signal indicating the detected concentration of NOx to the ECU 44.

The ECU 44 is a microcomputer provided with a CPU, RAM, ROM, and the like. A signal indicating the temperature is input from the exhaust temperature sensor 29, and a signal indicating the concentration of NOx is input from the NOx sensor 28 to the ECU 44. The ECU 44 adjusts the amount of urea water supplied to the exhaust gas by controlling the opening and closing of the injector 30. The ECU 44 may adjust the amount of urea water supplied to the exhaust gas according to the difference between the estimated value and the actually measured value of the NOx purification rate, which will be described later.

The ECU 44 derives the reaction rate of the NO oxidation reaction in the pre-stage oxidation catalyst 22 by using the oxidation catalyst model. The oxidation catalyst model is a model that outputs the reaction rate in the pre-stage oxidation catalyst 22 by inputting a base reaction rate determined according to temperature, a first parameter (described later), and a second parameter (described later). Entering the base reaction rate, the first parameter, and the second parameter into the oxidation catalyst model is synonymous with correcting the base reaction rate with the first parameter and the second parameter. The oxidation catalyst model can output the reaction rate only from the base reaction rate, and can output the reaction rate from only one of the base reaction rate and the first parameter and the second parameter. You may. Further, the ECU 44 derives the purification rate of NOx by using the selective reduction type catalyst model. In the selective reduction catalyst model, information such as the reaction rate output from the oxidation catalyst model is input, and the purification rate of NOx by the NOx reduction reaction in the selective reduction catalyst 36 (the reaction rate in the selective reduction catalyst 36 is taken into consideration). It is a model that outputs the purification rate of NOx).

As described above, the ECU 44 derives the reaction rate of the pre-stage oxidation catalyst 22 which is taken into consideration when estimating the NOx purification rate by the NOx reduction reaction in the selective reduction catalyst 36. The ECU 44 estimates the contact concentration indicating the degree to which the pre-stage oxidation catalyst 22 is in contact with the exhaust gas having a predetermined temperature or higher, and derives the first parameter according to the estimated contact concentration, and the selective reduction catalyst. The second process of deriving the second parameter according to the difference between the estimated value of the NOx purification rate by the NOx reduction reaction at No. 36 and the measured value of the NOx purification rate based on the detection result of the NOx sensor 28, and the temperature The base reaction rate derived accordingly is corrected by the first parameter and the second parameter, so that the third process of deriving the final reaction rate is executed.

In the first process, the ECU 44 may estimate the above-mentioned contact concentration based on, for example, the operating time of the engine 10 after starting the use of the pre-stage oxidation catalyst 22. It is estimated that the longer the operating time of the engine 10, the higher (increased) the contact concentration. In this case, detailed information such as the flow rate of the exhaust gas and whether the exhaust gas is above the predetermined temperature is not taken into consideration, but since the contact concentration is simply estimated from the operating time of the engine 10, the contact concentration is easily estimated. can do.

Further, the ECU 44 may estimate the contact concentration based on, for example, the cumulative flow rate of the exhaust gas that has passed through the pre-stage oxidation catalyst 22. In this case, the contact concentration is estimated with higher accuracy than the contact concentration is estimated from the operating time of the engine 10 described above. Further, the ECU 44 may estimate the contact concentration based on, for example, the cumulative flow rate of the exhaust gas passing through the pre-stage oxidation catalyst 22 and the energy flow rate of the exhaust gas derived from the temperature of the exhaust gas. The ECU 44 acquires the above-mentioned exhaust gas temperature information based on the signal indicating the temperature input from the exhaust temperature sensor 29.

In the second process, the ECU 44 obtains an estimated value of the purification rate of NOx by inputting information such as the reaction rate output from the oxidation catalyst model into the selective reduction catalyst model, for example. In this case, the reaction rate input to the selective reduction catalyst model may be the reaction rate output from the oxidation catalyst model in consideration of the first parameter derived in the first treatment. Then, the ECU 44 derives a difference between the estimated value of the NOx purification rate obtained from the selective reduction catalyst model and the measured value of the NOx purification rate based on the detection result of the NOx sensor 28, and according to the difference. The second parameter is derived. When the ECU 44 controls the injector 30 so that the amount of urea water supplied to the exhaust gas is adjusted according to the difference between the estimated value of the purification rate of NOx and the measured value, the injector 30 The second parameter may be derived by indirectly acquiring information on the difference between the estimated value of the purification rate of NOx and the actually measured value according to the urea injection amount in the above.

In the third process, the ECU 33 inputs the derived base reaction rate, the derived first parameter, and the derived second parameter into the oxidation catalyst model, for example, in the pre-stage oxidation catalyst 22. Obtain reaction rate. That is, the ECU 33 derives the final reaction rate by correcting the base reaction rate with the first parameter and the second parameter.

Next, the reaction rate derivation process of the pre-stage oxidation catalyst 22 described above will be described with reference to FIG. FIG. 2 is a flowchart showing a reaction rate derivation process of the pre-stage oxidation catalyst 22 performed by the exhaust gas purification device 20.

As shown in FIG. 2, in the reaction rate derivation process, the ECU 44 first estimates the contact concentration of the pre-stage oxidation catalyst 22 based on the operating time of the engine 10 and derives the first parameter K1 (step S1). The ECU 44 is based on the cumulative exhaust gas flow rate that has passed through the pre-stage oxidation catalyst 22, or the exhaust gas energy derived from the cumulative exhaust gas flow rate that has passed through the pre-stage oxidation catalyst 22 and the exhaust gas temperature. The above-mentioned contact concentration may be estimated based on the flow rate.

Subsequently, the ECU 44 derives the second parameter K2 from the difference between the estimated value of the NOx purification rate output from the selective reduction catalyst model and the measured value of the NOx purification rate based on the detection result of the NOx sensor 28. (Step S2).

Subsequently, the ECU 44 derives the reaction rate of the pre-stage oxidation catalyst 22 in consideration of the first parameter K1 and the second parameter K2 (step S3). Specifically, the ECU 44 inputs the derived base reaction rate according to the temperature, the derived first parameter, and the derived second parameter into the oxidation catalyst model, thereby reacting in the pre-stage oxidation catalyst 22. Get speed. After the reaction rate of the pre-stage oxidation catalyst 22 is obtained, the reaction rate is taken into consideration when estimating the purification rate of NOx and the like. Then, it is determined whether or not it is the end timing of the control (step S4), and if it is not the end timing, it is repeatedly executed from the process of step S1, and if it is the end timing, the process ends.

Next, the action and effect of this embodiment will be described.

The exhaust purification device 20 according to the present embodiment is an exhaust purification device that purifies the exhaust gas discharged from the engine 10, is arranged in the exhaust passage 12 through which the exhaust gas flows, and oxidizes NOx contained in the exhaust gas. The pre-stage oxidation catalyst 22 to be used, the selective reduction type catalyst 36 disposed downstream of the pre-stage oxidation catalyst 22 in the exhaust passage 12 to reduce NOx contained in the exhaust gas, and the downstream side and downstream from the pre-stage oxidation catalyst 22. An injector 30 configured to inject a reducing agent into the exhaust gas flowing through the exhaust gas passage 12 upstream of the selective reduction type catalyst 36, a NOx sensor 28 for detecting the concentration of NOx contained in the exhaust gas, and selective reduction. The ECU 44 includes an ECU 44 for deriving the reaction rate of the pre-stage oxidation catalyst 22, which is considered when estimating the NOx purification rate by the NOx reduction reaction in the mold catalyst 36, and the ECU 44 includes a pre-stage oxidation catalyst 22 having a temperature equal to or higher than a predetermined temperature. The first treatment, which estimates the contact concentration indicating the degree of contact with the exhaust gas and derives the first parameter according to the estimated contact concentration, and the NOx purification rate by the NOx reduction reaction in the selective reduction catalyst 36 The second process of deriving the second parameter according to the difference between the estimated value and the measured value of the purification rate of NOx based on the detection result of the NOx sensor 28, and the base reaction rate derived according to the temperature are the first. It is configured to execute the third process of deriving the final reaction rate by correcting with the parameter and the second parameter.

In the exhaust gas purification device 20 according to the present embodiment, the reaction rate in the pre-stage oxidation catalyst 22 derived according to the temperature is corrected by the first parameter and the second parameter, and the final reaction rate is derived. The first parameter is a parameter according to the contact concentration indicating the degree to which the pre-stage oxidation catalyst 22 is in contact with the exhaust gas having a predetermined temperature or higher. The oxidizing power of the pre-stage oxidation catalyst 22 is highest in the state immediately after production, and then gradually decreases as the contact concentration with the high-temperature exhaust gas increases. Therefore, by correcting the reaction rate by the first parameter in consideration of the contact concentration described above, the reaction rate can be derived with higher accuracy in consideration of the state of the oxidizing power of the pre-stage oxidation catalyst 22. The second parameter is a parameter according to the difference between the estimated value and the actually measured value of the purification rate of NOx. By considering the above-mentioned first parameter, the reaction rate can be derived in consideration of the difference in oxidizing power based on the usage state of the pre-stage oxidation catalyst 22 (how much it is in contact with the high-temperature exhaust gas). However, since there are individual differences (individual differences in oxidizing ability) in the pre-stage oxidation catalyst 22, there is a limit to improving the accuracy of the reaction rate only by the correction by the first parameter. In this regard, the reaction rate is actually corrected by a parameter (second parameter) corresponding to the difference between the estimated value of the purification rate of NOx derived in consideration of the reaction rate of the pre-stage oxidation catalyst 22 and the measured value. In consideration of the information measured in the above, the reaction rate can be derived with higher accuracy by making corrections according to the inherent oxidizing ability of the pre-stage oxidation catalyst 22. From the above, according to the exhaust gas purification device 20 according to the present embodiment, the reaction rate in the pre-stage oxidation catalyst 22 is derived with high accuracy, and the occurrence of erroneous control due to the deterioration of the estimation accuracy of the NOx purification rate is prevented. Can be done. In addition, the erroneous control here means that, for example, when the estimation accuracy of the NOx purification rate is low, the deviation from the measured value of the NOx purification rate becomes large, and it is determined that the measured value is abnormal, and the apparatus determines. It may be determined that the device is out of order, or the amount of urea water injected from the injector 30 may be changed by mistake.

For example, in the conventional exhaust purification device, the reaction rate of the oxidation catalyst is derived only according to the temperature of the exhaust gas. In this case, the usage state of the oxidation catalyst and individual differences were not taken into consideration. Therefore, for example, the state of use of the oxidation catalyst is considered to be a uniformly aged state, and the reaction rate is derived only from the information on the temperature of the exhaust gas. In this case, for example, for an oxidation catalyst having a high oxidizing power immediately after production, the reaction rate is faster than the reaction rate calculated in the model, and there is a discrepancy between the calculated value of the model and the actual value. According to the exhaust gas purification device 20 according to the present embodiment, the reaction rate of the pre-stage oxidation catalyst 22 can be derived with high accuracy while considering the difference in the usage state as described above.

The ECU 44 may estimate the contact concentration based on the operating time of the engine 10. This makes it possible to easily estimate the contact concentration.

The ECU 44 may estimate the contact concentration based on the cumulative flow rate of the exhaust gas that has passed through the pre-stage oxidation catalyst 22. As a result, the contact concentration can be estimated with higher accuracy than the case where the contact concentration is simply estimated from the operating time of the engine 10.

The ECU 44 may estimate the contact concentration based on the cumulative exhaust gas flow rate that has passed through the pre-stage oxidation catalyst 22 and the exhaust gas energy flow rate derived from the exhaust gas temperature. In this way, the contact concentration can be estimated with higher accuracy by considering not only the flow rate of the exhaust gas but also the temperature.

10 ... Engine, 12 ... Exhaust passage, 20 ... Exhaust purification device, 22 ... Pre-stage oxidation catalyst (oxidation catalyst), 28 ... NOx sensor, 30 ... Injector (reducing agent injection device), 36 ... Selective reduction catalyst (reduction catalyst) , 44 ... ECU (control unit).

Claims (4)

An exhaust purification device that purifies the exhaust gas emitted from the engine.
An oxidation catalyst that is disposed in the exhaust passage through which the exhaust gas flows and oxidizes NOx contained in the exhaust gas, and
A reduction catalyst arranged downstream of the oxidation catalyst in the exhaust passage and reducing NOx contained in the exhaust gas, and a reduction catalyst.
A reducing agent injection device configured to be able to inject a reducing agent into the exhaust gas flowing through the exhaust passage on the downstream side of the oxidation catalyst and on the upstream side of the reduction catalyst.
A NOx sensor that detects the concentration of NOx contained in the exhaust gas, and
A control unit for deriving the reaction rate of the oxidation catalyst, which is considered when estimating the purification rate of NOx by the NOx reduction reaction in the reduction catalyst, is provided.
The control unit
The first process of estimating the contact concentration indicating the degree to which the oxidation catalyst is in contact with the exhaust gas at a predetermined temperature or higher and deriving the first parameter according to the estimated contact concentration.
A second process for deriving a second parameter according to the difference between the estimated value of the NOx purification rate due to the NOx reduction reaction in the reduction catalyst and the measured value of the NOx purification rate based on the detection result of the NOx sensor.
Exhaust gas is configured to perform a third process of deriving the final reaction rate by correcting the reaction rate derived according to the temperature with the first parameter and the second parameter. Purification device. The exhaust gas purification device according to claim 1, wherein the control unit estimates the contact concentration based on the operating time of the engine. The exhaust gas purification device according to claim 1 or 2, wherein the control unit estimates the contact concentration based on the cumulative flow rate of the exhaust gas that has passed through the oxidation catalyst. The control unit estimates the contact concentration based on the cumulative flow rate of the exhaust gas that has passed through the oxidation catalyst and the energy flow rate of the exhaust gas derived from the temperature of the exhaust gas, claims 1 to 3. Exhaust gas purification device according to any one of the above.

Images