SCR urea pump pumpback control system and control method thereof

Abstract

The invention discloses a SCR urea pump pumpback control system. The system comprises a urea ejector, a urea pump, a urea liquid supply pipe and an engine controller, wherein the engine controller comprises a urea ejector control module and a urea pump control module, the signal output end of the urea pump control module is connected with the signal input end of the urea pump, the signal output end of the urea ejector control module is connected with the signal input end of the urea ejector, and the control method comprises the steps that firstly, the urea ejector control module controls the urea ejector to be tarted, then it is repeated at least twice that the urea pump control module controls the urea pump to pump back for T1 seconds and then controls the urea pump to stop for T2 seconds, and finally, the urea ejector control module controls the urea ejector to be closed, and pumpback is completed. According to the system, the residual quantity of a urea solution in a liquid supply system is reduced, and the reliability of the liquid supply system is improved.

Description

technical field [0001] The invention belongs to the technical field of engine tail gas post-treatment, and in particular relates to an SCR urea pump pumping control system and a control method, which are suitable for reducing the residual amount of urea solution, thereby improving the reliability of the SCR liquid supply system. Background technique [0002] At present, SCR post-treatment technology is the main technical means to reduce NOx in diesel engine exhaust. Its working principle is that the ammonia gas formed by injecting urea through hydrolysis and atomization will undergo redox reaction with NOx in the exhaust pipe in the catalyst to generate harmless nitrogen gas. The SCR urea supply system includes a urea tank and a urea pump integrated at the bottom of the urea tank. The urea pump is connected to the urea injector installed on the post-processor through the urea pipeline. When urea injection is required, the urea pump starts to work to realize liquid supply . ...

AI Technical Summary

Problems solved by technology

[0003] At present, the urea pump back pumping strategy is mainly adopted in the market to avoid the residual urea solution in the liquid supply system, that is, the urea pump continues to reverse for 30-60 seconds after the vehicle is stopped and turned off, and the urea residual solution in the urea pipeline, urea injector and urea pump is removed. Back pumping into the urea tank, on the one hand, because the back pumping efficiency of the urea pump is only 50–80%, the urea pipeline cannot be completely back pumped clean; The high-temperature air in the tank is rapidly cooled to form a negative pressure, which makes the urea solution flow back from the urea tank side to the urea pipeline and urea injector, resulting in a large amount of urea solution remaining in the liquid supply system. The residual urea solution crystallizes and expands under low temperature conditions, which is easy Damage to system components. Although the urea pipeline is made of a material with a large expansion coefficient and the stainless steel tube is embedded in the plastic flow channel inside the urea pump, the risk of avoiding damage to the system components by the urea residual solution can be reduced, but its development Long cycle and high cost

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