Scr system

Abstract

The disclosed SCR system can prevent erroneous indications of insufficient aqueous urea solution due to fluctuations in the liquid surface in an aqueous urea solution tank, preventing an engine from being unnecessarily prohibited from starting. Said SCR system can also promptly remove an engine-start prohibition after the aqueous urea solution is replenished, and is provided with: an aqueous urea solution tank (105) that stores an aqueous urea solution for spraying inside an engine (E) exhaust pipe (102); a level sensor (120) that measures the height of the liquid surface in the aqueous urea solution tank (105); a low-pass filter (1) that has signal response characteristics, with respect to the output signal from the level sensor (120), that have a small time constant when the engine speed is low and a large time constant when the engine speed is high; a remaining-amount indicator (2) that, on the basis of the level sensor (120) output processed by the low-pass filter (1), displays how much aqueous urea solution remains; and an insufficient-aqueous-urea-solution start prohibition unit (3) that prohibits the engine from starting when the amount of aqueous urea solution remaining is less than a minimum value.

Description

technical field [0001] The present invention relates to an SCR system for purifying exhaust gas by injecting urea water into the exhaust gas of a diesel vehicle, and relates to an SCR system for preventing false indication of urea water shortage and undesired engine failure caused by fluctuations in the liquid level of a urea water tank Start prohibition, and quickly remove the engine start prohibition after the urea water is replenished. Background technique [0002] Used to purify NO in the exhaust gas of diesel engines x developed an SCR system using an SCR (Selective Catalytic Reduction: Selective Catalytic Reduction) device. [0003] The SCR system supplies urea water to the upstream of the exhaust gas of the SCR device, ammonia is generated by the heat of the exhaust gas, and NO is released on the SCR catalyst by the ammonia x Reduction and purification (for example, refer to Patent Document 1). [0004] prior art literature [0005] patent documents [0006] Pate...

AI Technical Summary

Problems solved by technology

Therefore, there is a problem that a warning is issued due to fluctuations in the liquid level caused by such vehicle vibration, or the engine cannot be started.

In addition, with respect to fluctuations in the remaining amount detected by the liquid level sensor, on the other hand, the estimated remaining amount based on the accumulation of the urea water injection amount is constantly decreasing, so the two deviate, and the remaining amount management becomes inaccurate.

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