SCR system

Abstract

Provided is an SCR system that can rapidly cancel engine start prohibition after filling a urea aqueous solution as well as preventing improper indication of deficiency of the urea aqueous solution by variation in a solution level in a urea aqueous solution tank and unwanted engine start prohibition. The SCR system includes a urea aqueous solution tank 105 configured to retain a urea aqueous solution to be injected into an exhaust pipe 102 of an engine E, a level sensor 120 configured to detect a solution level height in the urea aqueous solution tank 105, a lowpass filter 1 having a signal response characteristic in which a time constant is small when an engine rpm is low and the time constant is larger when the engine rpm is high, with respect to an output signal of the level sensor 120, a remaining amount indicator 2 configured to indicate a remaining amount of the urea aqueous solution based on an output signal of the level sensor 120 processed by the lowpass filter 1, and a start prohibiting unit 3 in deficiency of the urea aqueous solution configured to prohibit the engine from being started when the remaining amount of the urea aqueous solution is less than a lowerlimit 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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