Exhaust gas cleaning system

Abstract

The present invention provides an exhaust gas purification system which, in a continuous regeneration type DPF (3), has little variation in torque and prevents generation of white smoke during regeneration control operation for DPF regeneration. , the structure is as follows: When the regeneration control of the continuous regeneration type DPF (3) with the oxidation catalyst (3Aa) installed on the upstream side of the filter (3Ab) is performed, the exhaust gas temperature (T1) at the inlet of the oxidation catalyst (3Aa) is oxidized When the catalyst activation temperature (Ta) is below, the exhaust throttle valve (31) installed in the exhaust passage (2) is closed to perform retarded multi-stage injection control, and the temperature of the exhaust gas is raised and the inlet of the catalyst (3Aa) is oxidized. After the exhaust gas temperature (T1) rises above the activation temperature (Ta) of the oxidation catalyst, the exhaust throttle valve (31) is opened stepwise or continuously to make the inlet exhaust temperature (T2) of the filter (3Ab) Reach above the lower limit temperature (Tb1) of forced combustion of PM.

Description

technical field [0001] The present invention relates to an exhaust gas purification system having a continuous regeneration type diesel particulate filter to purify exhaust gas discharged from an engine. Background technique [0002] Regarding the discharge amount of particulate matter (PM: Particulate Matter, hereinafter referred to as PM) discharged from the diesel engine, NO X , CO and HC are strengthened every year. With the strengthening of such regulations, it is not possible to improve the engine alone. Therefore, a technology has been developed that uses a filter called a Diesel Particulate Filter (DPF: Diesel Particulate Filter, hereinafter referred to as DPF) to trap PM exhausted from the engine to reduce the amount of PM exhausted to the outside. [0003] DPFs that directly capture the PM include a ceramic monolithic honeycomb wall-flow filter, a fiber filter made of ceramic or metal fibers, and the like. The exhaust gas purification system using the DPF, like ...

AI Technical Summary

Problems solved by technology

However, torque fluctuations also occur in this case

[0021] In addition, when switching from multi-stage injection with an exhaust throttle valve to normal injection control, HC and white smoke may sometimes be generated due to changes in the injection amount.

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