Filter controller system

Abstract

In order to calculate an estimation of the amount of deposited particulates in a first filter (61) or a second filter (62), a first estimation calculating section (100) for outputting first estimation data (XA) based on pressure differential across the filter and a second estimation calculating section (110) for outputting second estimation data (XB) based on engine operating state are provided, the data between the first estimation data (XA) and the second estimation data (XB) that is the more reliable estimation data in light of engine (2) rotation is selected and whether or not filter regeneration should be conducted is decided. In addition, the difference between the first and second estimation data (XA, XB) is considered and when the difference is larger than a prescribed value, then even if the engine (2) rpm is high, selection of the first estimation data XA, which is apt to be an estimated value of low reliability owing to cracking of the deposited particulates, is avoided.

Description

TECHNICAL FIELD[0001]The present invention relates to a filter control system capable of suitably timed regeneration of a filter for collecting particulates contained in engine exhaust gas.BACKGROUND ART[0002]In recent years, various devices for after-treating diesel particulates in engine exhaust gas have been developed for installation in the exhaust systems of diesel engines so as to curb dispersion of fine particles contained in diesel engine exhaust gas into the atmosphere. The exhaust gas treatment devices of this type are equipped with filter(s) for collecting particulates contained in the exhaust gas emitted by a diesel engine when the exhaust gas passes through an exhaust gas passage. Since the particulates collected by the filter therefore progressively deposit in the filter, the filter eventually clogs to make passage of exhaust gas impossible.[0003]In the conventional exhaust gas treatment device of this type, therefore, when the amount of deposited particulates in the f...

AI Technical Summary

Benefits of technology

[0017]When the difference is equal to or greater than a prescribed value at engine start, adverse effect on the amount of deposited particulates owing to cracking of particulate matter deposited in the filter can be eliminated by selecting the estimation of the second estimation means.

[0018]In the present invention, one between an estimated value of the deposited amount of particulates obtained based on the exhaust gas pressure differential across the filter and an estimated value of the deposited amount of particulates calculated from engine operation parameters and the like is selectively used with consideration to the engine operating state and the difference between the two estimated values. As a result, the amount of deposited particulates can be estimated with higher accuracy and the proper time for filter regeneration can be decided more appropriately.

Problems solved by technology

Since the particulates collected by the filter therefore progressively deposit in the filter, the filter eventually clogs to make passage of exhaust gas impossible.

Since the method used to regenerate the filter is to burn the particulates by heating the filter, the filter comes under a load owing to the heating during filter regeneration.

However, this technique of the prior art has the following problems.

When the engine is operating at low rpm because it has entered the idling state, for example, accurate estimation of the amount of deposited particulates based on the pressure differential is difficult because the exhaust gas flow rate in the exhaust passage decreases and the pressure differential across the filter therefore becomes small even when the accumulated amount of particulates is high.

When the pressure of the exhaust gas is low, moreover, the relationship between the exhaust gas pressure and the output signal of a pressure sensor does not exhibit a linear characteristic, so that the accuracy of the pressure data contained in the output signal is degraded and, in addition, the output signal from the pressure sensor falls to a level that makes it easily affected by noise.

Thus, accurate estimation of the amount of deposited particulates also becomes difficult owing to problems regarding the properties of the pressure sensor.

Further, in a case where particulates have deposited in the filter and the filter remains at a high-temperature with the engine stopped, volatile components in the particulates deposited in the filter are released to produce cracks in the particulate matter.

This makes it difficult to estimate the amount of deposited particulates accurately.

The end result is that it tends to give rise to the disadvantage of unnecessarily shortening the filter service life by increasing the filter regeneration frequency.

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