Exhaust aftertreatment device

Abstract

When an estimated value (A value) of an accumulation amount in a filter for trapping particulate matter reaches a prescribed value A1 corresponding to a prescribed accumulation amount Qm of the particulate matter and ash (S12), the forced regeneration of the filter is performed (S20); and when the estimated value (A value) reaches the prescribed value A1 again before the elapsed time since the completion of the forced regeneration of the filter reaches a prescribed time period T1 (S12, S14), it is judged that the amount of the ash accumulated in the filter is equal to or larger than a regulation amount (cleaning is required).

Description

TECHNICAL FIELD[0001]The present invention relates to an exhaust aftertreatment device, and more specifically, to a technology of assessing ash accumulation in a filter for trapping particulate matter contained in exhaust gas of a diesel engine.BACKGROUND ART[0002]An exhaust path of a vehicle diesel engine is normally provided with a filter for trapping particulate matter (PM) such as soot together with an exhaust purification catalyst. By this means, harmful substances (CO, HC, NOx, etc.) in exhaust gas are oxidized or reduced to be removed, and are prevented from being dispersed in the atmosphere.[0003]Particulate matter is accumulated in the filter, and it is burned and removed by heating the filter to higher temperature. The filter is thus regenerated and prevented from clogging. In general, a so-called forced regeneration is carried out. In the forced regeneration, an estimation is made of PM accumulation amount in the filter on the basis of differential pressure between the fr...

AI Technical Summary

Benefits of technology

[0013]In the exhaust aftertreatment device claimed in claim 1, if the estimated value obtained by the accumulation-amount estimating means reaches the prescribed value corresponding to the prescribed accumulation amount of the particulate matter and the ash, the forced regeneration of the filter is performed by the forced regeneration means; and if the estimated value obtained by the accumulation-amount estimating means reaches the prescribed value again before the elapsed time since completion of the forced regeneration of the filter by the forced regeneration reaches the prescribed time period, the ash-judging means judges that the amount of the ash accumulated in the filter is equal to or larger than the regulation amount.

[0014]Under the situation where the accumulation amount of the particulate matter and the ash in the filter is small, the estimated value often contains an error for various reasons. It is then difficult to accurately estimate an ash accumulation amount, and there is the possibility that ash accumulation cannot be properly assessed. However, if the forced regeneration of the filter is performed when the estimated value reaches the prescribed value corresponding to the relatively large prescribed accumulation amount of the particulate matter and the ash as described above, and if it is judged that the amount of the ash accumulated in the filter is equal to or larger than the regulation amount when the estimated value later reaches the prescribed value again within a prescribed time period as mentioned above, it is possible to eliminate an affect of the error and yet precisely realize the decrease of an interval of the forced regeneration that is performed when a particulate matter-trapping function of the filter is deteriorated. Consequently, ash accumulation can be assessed with accuracy.

[0015]By this means, the ash is removed by cleaning the filter with the most suitable timing. The filter clogging caused by ash is thus prevented from progressing, and the particulate matter-trapping function of the filter is well maintained. Overall, an increase of exhaust pressure and a deterioration of fuel consumption are prevented. In addition, the filter is prevented from being excessively cleaned.

[0016]In the exhaust aftertreatment device claimed in claim 2, it is judged that the amount of the ash accumulated in the filter is equal to or larger than the regulation amount when the estimated value reaches the prescribed value a predetermined number of times or more within a regulation time period.

[0017]It is then possible to avoid a faulty judgment and assess the ash accumulation with accuracy.

[0018]In the exhaust aftertreatment device claimed in claim 3, when the amount of the ash accumulated in the filter becomes equal to or larger than the regulation amount, filter cleaning is urged. This way, the filter is cleaned without fail, and the ash is removed.

Problems solved by technology

Ash therefore has the problem that it is not removed by forced regeneration and remains accumulated in the filter.

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