Exhaust Gas Purification System for Working Machine

Abstract

Disclosed is an exhaust gas purification system for a working machine. The system is provided with a filter for capturing particulate matter contained in exhaust gas from an engine, a differential pressure sensor for detecting a differential pressure between an exhaust upstream side and an exhaust downstream side of the filter, and a controller having a regeneration determination unit for determining whether or not a time, at which forced regeneration is needed, has been reached. The controller includes one that has a variation determination unit for determining whether or not a state quantity relevant to an operation of the engine, for example, an engine speed has varied abruptly and that, when the state quantity is determined to have abruptly varied, performs processing to invalidate the determination by the regeneration determination unit during a predetermined time in which an effect of the state quantity is considered to diminish.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the priority of Japanese Patent Application 2011-004960 filed Jan. 13, 2011, which is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an exhaust gas purification system for a working machine such as a hydraulic excavator, which is provided with a filter for removing particulate matter (hereinafter abbreviated as “PM”) contained in exhaust gas from an engine.[0004]2. Description of the Related Art[0005]As a conventional technology of this type, there is one disclosed in JP-A-2005-307878. This conventional technology is provided with a filter for capturing PM, which is contained in exhaust gas from an engine, on an exhaust downstream side, an exhaust gas temperature sensor, and a differential pressure sensor for detecting a differential pressure between an exhaust upstream side and the exhaust downstream side of the filter. The conventio...

AI Technical Summary

Benefits of technology

[0011]The present invention has been made with an attention focused on the fact that upon occurrence of an abrupt variation on a body, a state quantity relevant to an operation of an engine, such as the engine speed or the injection quantity of fuel, varies abruptly. According to the present invention, when the state quantity relevant to the operation of the engine is determined by the variation determination unit of the controller to have abruptly varied in response to an abrupt variation of the body, processing is performed by the controller to invalidate the determination by the regeneration determination unit that determines whether or not forced regeneration is to be performed, in other words, to terminate a determination function of the regeneration determination unit during a predetermined time in which an effect of the abrupt variation in the state quantity is considered to diminish. The above-described predetermined time can be set experimentally or empirically in view of load variations which may occur on the associated working machine. As a consequence, the present invention can realize forced regeneration without being affected by abrupt variations of the body.

[0015]In the exhaust gas purification system of the present invention for the working machine equipped with the working equipment, the controller is constituted to comprise one that has the variation determination unit for determining whether or not the state quantity relevant to an operation of the engine has varied abruptly and that, when the state quantity is determined to have abruptly varied by the variation determination unit, performs processing to invalidate the determination by the regeneration determination unit during the predetermined time in which the effect of the state quantity is considered to diminish. Owing to this constitution, it is possible to realize forced regeneration without being affected by abrupt variations of the body. Described specifically, it is possible to minimize the performance of unnecessary forced regeneration that would otherwise tend to be performed in response to abrupt variations of the body, thereby making it possible to prevent wasteful injections of fuel and hence to improve the fuel economy of the working machine equipped with the exhaust gas purification system.

Problems solved by technology

When the conventional technology is applied to a working machine and a determination is made at the regeneration determination unit of the controller by using such a determinative differential pressure ΔP2, a problem may hence arise that, even if PM has not deposited much on the filter actually, ΔP1>ΔP2 is determined and forced regeneration is performed although it is not needed.

Such unnecessary forced regeneration results in a wasteful injection of fuel, and leads to a deterioration in fuel economy.

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