US Patent No. 8,881,507, Air driven reductant delivery system
This technology is about a dosing system for delivering reductant to an exhaust gas treatment system of an internal combustion engine using air driven hydraulic pumps for closed-loop controlling reductant pressure and a two-stage PWM control method for controlling dosing rate. Reductant residue in the dosing systems is purged by using compressed air after a dosing process completes, and when the air driven hydraulic pumps are positioned inside a reductant tank, dedicated heating means for the pumps is not necessary. The air driven hydraulic pumps can also use low pressure compressed air, and the closed-loop pressure control together with the two-stage PWM control allow dosing accuracy insensitive to pressure variations in compressed air. These new features enable the dosing system use a variety of compressed air sources, including an engine turbo.
Uniqueness and benefits of this technology:
1. Air driven hydraulic dosing system in which compressed air is used for pressing reductant out and no motor is required;
2. High dosing accuracy is obtained with dual-loop feedback controls including a pressure control loop and a flow rate control loop;
3. No heating device is required for the hydraulic pump;
4. High pressure can be obtained with a pressure boosting structure.