JP7059912B2 - Exhaust purification device for internal combustion engine - Google Patents

Description

The present invention relates to an exhaust gas purification device for an internal combustion engine.

The oxidation rate of particulate matter (PM) calculated from the rate of change in the differential pressure between the upstream side and the downstream side of the filter, and the oxidation rate of PM when the sulfur concentration of the fuel is assumed to be as set. There is known a technique for correcting the set value of the sulfur concentration of the fuel according to the difference between the two (see, for example, Patent Document 1). This technique is based on the phenomenon that the higher the sulfur concentration of the fuel, the higher the oxidation rate of PM.

Japanese Unexamined Patent Publication No. 2016-142256

Here, when the sulfur component contained in the fuel is adsorbed by the oxidation catalyst, so-called sulfur poisoning occurs in which the purification performance of the oxidation catalyst deteriorates. When performing an abnormality determination for determining whether or not the oxidation catalyst has deteriorated, if sulfur poisoning has occurred, it may be determined that the oxidation catalyst is abnormal. However, unlike the case where the oxidation catalyst is deteriorated due to sintering of precious metals or the like, sulfur poisoning can be recovered. Therefore, it is not preferable to determine that the oxidation catalyst has an abnormality when the purification performance is deteriorated due to the occurrence of sulfur poisoning.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to prevent the accuracy of catalyst abnormality determination from being lowered due to sulfur poisoning of the catalyst.

One aspect of the present invention is a catalyst provided in an exhaust passage of an internal combustion engine and having an oxidizing performance, and if the purification performance of the catalyst is equal to or higher than a threshold value, it is determined that the catalyst is normal, and the purification performance is the said. A control device for determining that the catalyst is abnormal if it is less than the threshold value, and an exhaust gas purification device for an internal combustion engine including a control device for changing the threshold value based on the hygroscopicity of the catalyst.

Hygroscopicity is an index showing the ease of adsorbing water when the catalyst adsorbs water. Hygroscopicity is, for example, the amount of water actually adsorbed on the catalyst relative to the estimated value of the amount of water adsorbed on the catalyst assuming the catalyst is normal and the sulfur component is not adsorbed on the catalyst. The ratio. The hygroscopicity is, for example, the water actually adsorbed on the catalyst with respect to the estimated value of the amount of water adsorbed on the catalyst when the catalyst is normal and the sulfur concentration of the fuel is assumed to be a set value. The ratio of quantities. Water is adsorbed on the catalyst when the temperature of the catalyst is relatively low, for example, when the internal combustion engine is cold started, and therefore the hygroscopicity may be acquired in such a case. Purification performance is an index showing the performance of the catalyst to purify the exhaust gas. For example, a sensor for detecting a specific component of exhaust gas may be provided, and purification performance may be acquired based on the detection value of the sensor. This purification performance may be based on the purification rate of the exhaust gas in the catalyst. Further, the purification performance is based on, for example, an estimated value of an increase in the temperature of the exhaust gas in the catalyst when HC (reducing agent) is supplied, assuming that the catalyst is normal and the sulfur component is not adsorbed on the catalyst. It is the ratio of the amount of increase in the temperature of the exhaust gas in the catalyst when the HC is actually supplied. Since HC is supplied to the catalyst, for example, when the filter is regenerated or when the temperature of the catalyst rises, the purification performance may be acquired at such times.

When the sulfur component is adsorbed on the catalyst, the hygroscopicity of the catalyst is enhanced. That is, the larger the amount of sulfur component adsorbed on the catalyst, the more water is adsorbed by the catalyst. On the other hand, as the amount of the sulfur component adsorbed on the catalyst increases, the purification performance of the catalyst deteriorates. Therefore, when the hygroscopicity is high, the purification performance of the catalyst is lowered accordingly. The deterioration of the purification performance in this case can be eliminated by carrying out a treatment for releasing the sulfur component from the catalyst. Therefore, the decrease in purification performance due to sulfur poisoning should be excluded when determining an abnormality in the catalyst. That is, the abnormality of the catalyst is determined by changing the threshold value according to the deterioration of the purification performance due to sulfur poisoning and comparing the purification performance with the threshold value. As a result, it is possible to prevent the accuracy of determining abnormality of the catalyst from being lowered due to sulfur poisoning of the catalyst.

Further, the control device may have a smaller threshold value as the hygroscopicity is higher.

That is, the larger the amount of the sulfur component adsorbed on the catalyst, the higher the hygroscopicity. Therefore, by reducing the threshold value accordingly, the influence of sulfur poisoning on the abnormality determination of the catalyst can be reduced.

Further, the control device further includes a temperature sensor for detecting the temperature of the exhaust gas flowing out of the catalyst, and the control device has the moisture absorption property based on the rate of increase of the detected value of the temperature sensor from the cold start time of the internal combustion engine. May be obtained.

The rate of increase in the detected value of the temperature sensor may be the amount of increase in the temperature of the exhaust gas flowing out of the catalyst per unit time. Here, in the process in which the temperature of the exhaust gas flowing out of the catalyst gradually rises after the cold start of the internal combustion engine, there is a period in which the temperature of the exhaust gas becomes substantially constant. This phenomenon occurs when the water adsorbed on the catalyst evaporates. During this period, the difference between the temperature of the exhaust gas flowing into the catalyst and the temperature of the exhaust gas flowing out of the catalyst becomes large. The period during which the temperature of the exhaust gas flowing out of the catalyst becomes substantially constant correlates with the amount of water adsorbed on the catalyst. That is, it has a correlation with hygroscopicity. Therefore, the hygroscopicity can be acquired based on the rate of increase of the detected value of the temperature sensor from the cold start time of the internal combustion engine.

Further, the control device may acquire the hygroscopicity based on a period in which the rate of increase of the detected value of the temperature sensor from the cold start time of the internal combustion engine is within a predetermined range including 0.

The period during which the rate of increase of the detected value of the temperature sensor falls within a predetermined range including 0 is a period in which the rate of increase hardly changes, and it may be considered that the rate of increase is 0 or the rate of increase is 0. It is a period without. During the period when the water adsorbed on the catalyst is evaporating, the rate of increase of the detected value of the temperature sensor becomes substantially 0. Therefore, the period during which the rate of increase of the detected value of the temperature sensor is within the predetermined range including 0 can be considered as the period during which the water adsorbed on the catalyst is evaporating, and the length of this period is set on the catalyst. Since it correlates with the amount of adsorbed water, it correlates with the hygroscopicity of the catalyst. Therefore, hygroscopicity can be obtained based on this period.

According to the present invention, it is possible to suppress a decrease in the accuracy of determining an abnormality of the catalyst due to sulfur poisoning of the catalyst.

It is a figure which shows the schematic structure of the exhaust gas purification device of the internal combustion engine which concerns on embodiment. It is a figure which showed the relationship between the temperature of an oxidation catalyst and the purification rate. It is a time chart showing the transition between the temperature of the exhaust gas flowing into the oxidation catalyst after the cold start of the internal combustion engine and the temperature of the exhaust gas flowing out from the oxidation catalyst. It is a figure which showed the relationship between the hygroscopicity in an oxidation catalyst, and the purification performance of an oxidation catalyst. It is a flowchart which showed the flow which carries out the abnormality determination of the oxidation catalyst which concerns on Example.

Hereinafter, embodiments for carrying out the present invention will be described in detail exemplary with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention to those alone.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an exhaust gas purification device for an internal combustion engine according to the present embodiment. The internal combustion engine 1 shown in FIG. 1 may be a diesel engine or a gasoline engine. The internal combustion engine 1 is mounted on a vehicle, for example.

An exhaust passage 2 is connected to the internal combustion engine 1. In the middle of the exhaust passage 2, an oxidation catalyst 3 and a filter 4 are provided in order from the upstream side in the exhaust flow direction. The oxidation catalyst 3 may be any catalyst having oxidation performance, and may be, for example, a three-way catalyst or an occlusion-reduced NOx catalyst. The filter 4 collects particulate matter (PM) in the exhaust. The oxidation catalyst 3 may be supported on the filter 4.

Further, a first temperature sensor 11 for detecting the temperature of the exhaust gas is attached to the exhaust passage 2 upstream of the oxidation catalyst 3. A second temperature sensor 12 for detecting the temperature of the exhaust gas is attached to the exhaust passage 2 downstream of the oxidation catalyst 3 and upstream of the filter 4. The first temperature sensor 11 can detect the temperature of the exhaust gas flowing into the oxidation catalyst 3. Further, the second temperature sensor 12 can detect the temperature of the exhaust gas flowing out from the oxidation catalyst 3.

An injection valve 6 for supplying fuel to the internal combustion engine 1 is attached to the internal combustion engine 1. Further, an intake passage 8 is connected to the internal combustion engine 1. A throttle 9 for adjusting the intake air amount of the internal combustion engine 1 is provided in the middle of the intake passage 8. An air flow meter 14 for detecting the amount of intake air of the internal combustion engine 1 is attached to an intake passage 8 on the upstream side in the intake flow direction of the throttle 9.

The internal combustion engine 1 configured as described above is provided with an ECU 10 which is an electronic control unit (controller) for controlling the internal combustion engine 1. The ECU 10 is a computer having a processor, a main storage unit, and an auxiliary storage unit. The ECU 10 controls the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the demands of the driver. In addition to the above sensors, the ECU 10 includes an accelerator opening sensor 16 that outputs an electric signal according to the amount of depression of the accelerator pedal 15 by the driver to detect the engine load, and a crank position sensor 17 that detects the engine rotation speed. It is connected via electrical wiring, and the output signals of these various sensors are input to the ECU 10. On the other hand, the injection valve 6 and the throttle 9 are connected to the ECU 10 via electrical wiring, and these devices are controlled by the ECU 10. At this time, the processor executes a predetermined program on the main memory.

The ECU 10 regenerates the filter 4, which is a process of removing PM accumulated on the filter 4. When the amount of PM collected in the filter 4 reaches a predetermined amount, the ECU 10 supplies HC (reducing agent) to the oxidation catalyst 3. When HC is oxidized in the oxidation catalyst 3, the temperature of the exhaust gas rises. By circulating this high temperature exhaust gas through the filter 4, the temperature of the filter 4 can be raised, so that PM can be oxidized and removed from the filter 4. In this way, the ECU 10 regenerates the filter 4 by supplying HC to the oxidation catalyst 3. For example, HC can be supplied to the oxidation catalyst 3 by providing an addition valve for supplying fuel on the upstream side of the oxidation catalyst 3. Further, by adjusting the air-fuel ratio of the internal combustion engine 1 to a rich air-fuel ratio, which is a smaller air-fuel ratio than the theoretical air-fuel ratio, HC can be supplied to the oxidation catalyst 3. In this case, the air-fuel ratio is adjusted by adjusting the opening degree of the throttle 9 or adjusting the fuel injection amount from the injection valve 6.

Further, the ECU 10 determines the abnormality of the oxidation catalyst 3 by comparing the purification performance of the oxidation catalyst 3 with the threshold value. The ECU 10 determines that the oxidation catalyst 3 is normal if the purification performance of the oxidation catalyst 3 is equal to or higher than the threshold value, and determines that the oxidation catalyst 3 is abnormal if the purification performance of the oxidation catalyst 3 is less than the threshold value. This threshold value is the lower limit of the purification performance when the oxidation catalyst 3 is normal.

In this embodiment, the purification performance of the oxidation catalyst 3 is defined as the ratio of the actual increase in the exhaust temperature to the estimated value of the increase in the exhaust temperature when HC is supplied to the oxidation catalyst 3. The estimated value of the increase in the temperature of the exhaust gas is based on the assumption that the oxidation catalyst 3 is normal and the sulfur component is not adsorbed on the oxidation catalyst 3, and if HC is supplied to the oxidation catalyst 3, the oxidation catalyst 3 is used. It is a value estimated how much the temperature of the exhaust rises in. When it is assumed that the oxidation catalyst 3 is normal and the sulfur component is not adsorbed on the oxidation catalyst 3, for example, it is assumed that the oxidation catalyst 3 exhibits the desired performance because the degree of deterioration of the oxidation catalyst 3 is low. Or when it is assumed that the oxidation catalyst 3 is new. Further, the amount of increase in the actual exhaust gas temperature when HC is supplied to the oxidation catalyst 3 is the amount of increase in the exhaust gas temperature in the oxidation catalyst 3 that actually supplies HC, and is from the detection value of the second temperature sensor 12. It can be calculated by subtracting the detected value of the first temperature sensor 11.

As the degree of deterioration of the oxidation catalyst 3 increases, the ability to oxidize HC decreases, so that the amount of increase in the temperature of the exhaust gas in the oxidation catalyst 3 when HC is supplied to the oxidation catalyst 3 decreases. Therefore, the amount of increase in the temperature of the exhaust gas correlates with the degree of deterioration of the oxidation catalyst 3. Therefore, the purification performance is acquired based on the amount of increase in the exhaust temperature. The amount of increase in the temperature of the exhaust gas correlates with the HC concentration of the exhaust gas flowing into the oxidation catalyst 3. Therefore, the estimated value of the increase in the temperature of the exhaust gas is calculated based on the HC concentration of the exhaust gas. This HC concentration can be calculated based on the air-fuel ratio (intake air amount and fuel injection amount) of the internal combustion engine 1.

Further, the amount of increase in the temperature of the exhaust gas in the oxidation catalyst 3 when the HC is supplied is affected by the amount of fuel supplied to the internal combustion engine 1 and the flow rate of the exhaust gas. Here, FIG. 2 is a diagram showing the relationship between the temperature of the oxidation catalyst 3 and the purification rate. The higher the exhaust flow rate, the larger the amount of fuel, the higher the degree of deterioration of the oxidation catalyst 3, or the higher the degree of sulfur poisoning of the oxidation catalyst 3, the higher the temperature of the oxidation catalyst 3 in the direction of the arrow in FIG. And the purification rate change. Therefore, in consideration of these, the estimated value of the increase in the temperature of the exhaust gas in the oxidation catalyst 3 is calculated. The above relationship is obtained in advance by an experiment, simulation, or the like and stored in the ECU 10.

The ECU 10 calculates the purification performance of the oxidation catalyst 3 when the filter 4 is regenerated. When the filter 4 is regenerated, HC is supplied to the oxidation catalyst 3, and at this time, the temperature of the exhaust gas in the oxidation catalyst 3 rises, so that the purification performance can be calculated as described above.

The purification performance can be defined in other ways. The purification performance in this embodiment may be an index indicating the performance of the oxidation catalyst 3 to purify the exhaust gas. For example, the degree of deterioration of the oxidation catalyst 3 correlates with the differential pressure upstream of the filter 4 and downstream of the filter 4 during regeneration of the filter 4, so that purification performance is acquired based on this differential pressure. May be good. Further, a sensor for detecting HC or the like may be attached to the exhaust passage 2 downstream of the oxidation catalyst 3 to acquire the purification performance of the oxidation catalyst 3 based on the detection value of this sensor.

When the sulfur component in the fuel is adsorbed by the oxidation catalyst 3, sulfur poisoning occurs in the oxidation catalyst 3. The occurrence of this sulfur poisoning lowers the purification performance of the oxidation catalyst 3. Such deterioration of the purification performance of the oxidation catalyst 3 due to sulfur poisoning can be eliminated by releasing the sulfur component from the oxidation catalyst 3 by raising the temperature of the oxidation catalyst 3. On the other hand, when the purification performance is deteriorated due to sintering of a precious metal or the like, it is difficult to restore the purification performance of the oxidation catalyst 3. Therefore, it is desirable to determine that the oxidation catalyst 3 is abnormal only when the purification performance is deteriorated due to the sintering of the precious metal or the like. On the other hand, when the purification performance is deteriorated only due to sulfur poisoning, it is desirable to determine that the oxidation catalyst 3 is normal. Therefore, the ECU 10 sets the threshold value used for determining the abnormality of the oxidation catalyst 3 as follows.

Here, when the sulfur component in the fuel is adsorbed on the oxidation catalyst 3, the hygroscopicity of the oxidation catalyst 3 increases. That is, there is a correlation between the hygroscopicity of the oxidation catalyst 3 and the amount of the sulfur component adsorbed on the oxidation catalyst 3, and therefore, the deterioration of the purification performance due to sulfur poisoning is correlated with the hygroscopicity of the oxidation catalyst 3. It can be said that. In this embodiment, the hygroscopicity of the oxidation catalyst 3 is defined as the ratio of the amount of water actually adsorbed by the oxidation catalyst 3 to the estimated value of the amount of water adsorbed by the oxidation catalyst 3. This estimated value of the amount of water estimated how much water was adsorbed on the oxidation catalyst 3 when it was assumed that the oxidation catalyst 3 was normal and the sulfur component was not adsorbed on the oxidation catalyst 3. The value. The estimated value of the amount of water is estimated based on the operation history of the internal combustion engine 1 from the cold start time.

Further, the amount of water actually adsorbed on the oxidation catalyst 3 can be detected based on the temperature of the exhaust gas flowing out of the oxidation catalyst 3 after the cold start of the internal combustion engine 1. Here, when the oxidation catalyst 3 is not yet activated (for example, when the temperature of the oxidation catalyst 3 is 150 ° C. or lower) in the process in which the temperature of the oxidation catalyst 3 rises after the cold start of the internal combustion engine 1. There is a time when the temperature of the oxidation catalyst 3 does not rise due to the influence of the heat of evaporation of water adsorbed on the oxidation catalyst 3. That is, there is a time when the temperature of the exhaust gas flowing out from the oxidation catalyst 3 becomes substantially constant.

FIG. 3 is a time chart showing the transition between the temperature of the exhaust gas flowing into the oxidation catalyst 3 after the cold start of the internal combustion engine 1 and the temperature of the exhaust gas flowing out of the oxidation catalyst 3. The solid line shows the temperature of the exhaust gas flowing out of the oxidation catalyst 3, and the alternate long and short dash line shows the temperature of the exhaust gas flowing into the oxidation catalyst 3. Therefore, the solid line can be considered as the detection value of the second temperature sensor 12, and the alternate long and short dash line can be considered as the detection value of the first temperature sensor 11. Since the water adsorbed on the oxidation catalyst 3 evaporates from the oxidation catalyst 3 at around 100 ° C., the temperature of the exhaust gas flowing out from the oxidation catalyst 3 becomes substantially constant at around 100 ° C. Then, in FIG. 3, the period from T1 to T2 is a period in which the temperature of the exhaust gas flowing out from the oxidation catalyst 3 becomes substantially constant. It can be said that this period is a period in which the rate of increase of the detected value of the second temperature sensor 12 is within a predetermined range including 0.

The period during which the temperature of the exhaust gas becomes substantially constant correlates with the amount of water adsorbed on the oxidation catalyst 3. That is, the larger the amount of water adsorbed on the oxidation catalyst 3, the longer the period during which the temperature of the exhaust gas flowing out of the oxidation catalyst 3 becomes substantially constant. Therefore, the temperature of the exhaust gas flowing out of the oxidation catalyst 3 after the cold start of the internal combustion engine 1 is detected by the second temperature sensor 12, and the water adsorbed on the oxidation catalyst 3 is adsorbed based on the period during which the detected value becomes constant. The amount of can be calculated. The period during which the exhaust temperature becomes substantially constant and the amount of water adsorbed on the oxidation catalyst 3 can be determined in advance by experiments, simulations, or the like.

In addition, hygroscopicity can be defined in other ways. The hygroscopicity in this embodiment may be an index indicating the ease of adsorbing water when the oxidation catalyst 3 adsorbs water. For example, the value obtained by multiplying the difference between the temperature of the exhaust gas flowing into the oxidation catalyst 3 and the temperature of the exhaust gas flowing out of the oxidation catalyst 3 by the flow rate of the exhaust gas (hereinafter, also referred to as a temperature difference integrated value) is obtained. It correlates with the amount of water adsorbed on the oxidation catalyst 3. That is, the larger the amount of water adsorbed on the oxidation catalyst 3, the longer the period during which the temperature of the exhaust gas flowing out of the oxidation catalyst 3 becomes substantially constant, and the larger the integrated temperature difference value becomes. Therefore, hygroscopicity may be obtained by calculating the amount of water adsorbed on the oxidation catalyst 3 based on the integrated temperature difference value.

If the purification performance of the oxidation catalyst 3 estimated as described above is low, sulfur poisoning or deterioration of the oxidation catalyst 3 is considered, but in the case of sulfur poisoning, oxidation occurs at the cold start of the internal combustion engine 1. The amount of water adsorbed on the catalyst 3 increases. Therefore, even if the purification performance is low, if the hygroscopicity is high, it is considered that the purification performance is deteriorated due to sulfur poisoning. Therefore, when the hygroscopicity is high, it is difficult to determine that the oxidation catalyst 3 is abnormal even when the purification performance is low.

FIG. 4 is a diagram showing the relationship between the hygroscopicity of the oxidation catalyst 3 and the purification performance of the oxidation catalyst 3. An abnormality determination of the oxidation catalyst 3 is carried out based on the relationship shown in FIG. That is, in the range lower than the threshold value in FIG. 4, it is determined that the oxidation catalyst 3 is abnormal, and in the range above the threshold value, it is determined that the oxidation catalyst 3 is normal. Here, when the hygroscopicity is high, it is considered that the sulfur concentration of the fuel is high. Therefore, even if the purification performance of the oxidation catalyst 3 is deteriorated, it is considered that the influence of sulfur poisoning is greater. Therefore, the higher the hygroscopicity, the smaller the threshold value. That is, the higher the hygroscopicity, the greater the deterioration of the purification performance due to sulfur poisoning. Therefore, the threshold value is reduced by the amount of the deterioration of the purification performance, and the abnormality determination of the oxidation catalyst 3 is carried out.

FIG. 5 is a flowchart showing a flow for performing abnormality determination of the oxidation catalyst 3 according to this embodiment. This flowchart is executed by the ECU 10 at predetermined time intervals. In step S101, it is determined whether or not the internal combustion engine 1 is in the cold start. When the detected value of the second temperature sensor 12 is equal to or less than the value at the time of cold start (for example, 150 ° C. or less), it is determined that the internal combustion engine 1 is at the time of cold start. If the elapsed time from the start of the internal combustion engine 1 is within a predetermined time, it may be determined that the internal combustion engine 1 is in the cold start time. If an affirmative determination is made in step S101, the process proceeds to step S102, and if a negative determination is made, the process proceeds to step S106.

In step S102, it is determined whether or not the rate of increase in the detected value of the second temperature sensor 12 (hereinafter, also referred to as the rate of temperature increase of the exhaust gas) is equal to or less than a predetermined rate. The predetermined rate is 0 or a value equivalent to 0, and it may be considered that the temperature of the exhaust gas flowing out from the oxidation catalyst 3 has not risen. In step S102, it can be said that it is determined whether or not the time of T1 in FIG. 3 has been reached. If an affirmative determination is made in step S102, the process proceeds to step S103, and if a negative determination is made, this routine is temporarily terminated.

In step S103, the time is counted, and in step S104, it is determined whether or not the temperature rise rate of the exhaust gas is larger than the predetermined rate. In step S104, it can be said that it is determined whether or not the time of T2 in FIG. 3 has been exceeded. If an affirmative determination is made in step S104, the process proceeds to step S105, and if a negative determination is made, the process returns to step S103 and the time is counted.

In step S105, the hygroscopicity of the oxidation catalyst 3 is calculated. Further, the threshold value is calculated from the hygroscopicity calculated in step S105 and the relationship shown in FIG. In step S105, the hygroscopicity is calculated based on the time counted in step S103. The relationship between the time counted in step S103 and the hygroscopicity is obtained in advance by an experiment, simulation, or the like.

In step S106, it is determined whether or not the conditions for calculating the purification performance of the oxidation catalyst 3 are satisfied. In this embodiment, in order to calculate the purification performance of the oxidation catalyst 3 when the filter 4 is regenerated, it is a condition that the purification performance of the oxidation catalyst 3 can be calculated that the filter 4 is regenerated. If an affirmative determination is made in step S106, the process proceeds to step S107, and if a negative determination is made, this routine is temporarily terminated.

In step S107, the purification performance of the oxidation catalyst 3 is calculated. Then, in step S108, it is determined whether or not the purification performance of the oxidation catalyst 3 is equal to or higher than the threshold value. If an affirmative determination is made in step S108, the process proceeds to step S109, and it is determined that the oxidation catalyst 3 is normal. On the other hand, if a negative determination is made in step S108, the process proceeds to step S110, and it is determined that the oxidation catalyst 3 is abnormal.

As described above, according to the present embodiment, since the abnormality determination of the oxidation catalyst 3 is performed in consideration of the deterioration of the purification performance due to the sulfur component adsorbed on the oxidation catalyst 3, more accurate abnormality determination is possible. It becomes.

1 Internal combustion engine 2 Exhaust passage 3 Oxidation catalyst 4 Filter 6 Injection valve 8 Intake passage 9 Throttle 10 ECU
11 1st temperature sensor 12 2nd temperature sensor

Claims (3)

A catalyst provided in the exhaust passage of an internal combustion engine and having oxidizing performance,
A control device that determines that the catalyst is normal if the purification performance of the catalyst is equal to or higher than the threshold value, and determines that the catalyst is abnormal if the purification performance is less than the threshold value. A control device that changes the threshold value based on sex, and
A temperature sensor that detects the temperature of the exhaust gas flowing out of the catalyst, and
Equipped with
The control device is an exhaust gas purification device for an internal combustion engine that acquires the hygroscopicity based on the rate of increase of the detected value of the temperature sensor from the cold start time of the internal combustion engine. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the control device reduces the threshold value as the hygroscopicity increases. The control device acquires the hygroscopicity based on a period in which the rate of increase of the detected value of the temperature sensor from the cold start time of the internal combustion engine is within a predetermined range including 0, claim 1 or 2 . The exhaust purification device for an internal combustion engine described in.

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