Air driven reductant delivery system

A method for controlling a fluid dosing system including a fluid tank, a first pump with a first-pump suction stroke and a first-pump pressing stroke, a second pump with a second-pump suction stroke and a second-pump pressing stroke, a hydraulic buffer, a pressure sensor provide a sensing value indicative of a fluid pressure in said hydraulic buffer, and an injector, comprising:

• building up fluid pressure in said hydraulic buffer in said first-pump pressing stroke of said first pump;
• enabling a feedback control to maintain said fluid pressure within a predetermined range in said first-pump pressing stroke of said first pump with at least said sensing value obtained from said pressure sensor, and starting said second-pump suction stroke of said second pump thereafter;
• enabling a feedback control to maintain said fluid pressure within said predetermined range in said second-pump pressing stroke of said second pump with at least said sensing value obtained from said pressure sensor, and starting said first-pump suction stroke of said first pump thereafter;
• and
• controlling a fluid delivery amount by adjusting an opening time of said injector.

A method for controlling a fluid delivery system including a fluid tank, a pump with a suction stroke and a pressing stroke, a hydraulic buffer, a pressure sensor providing a sensing value indicative of a fluid pressure in said hydraulic buffer, and an injector opened and closed with a valve operated by a solenoid, comprising:

• building up fluid pressure in said hydraulic buffer in said pressing stroke of said pump;
• enabling a feedback pressure control in each of said pressuring stroke of said pump to maintain a fluid pressure within a predetermined range in said hydraulic buffer by adjusting an air amount in said pump through feeding compressed air into said pump, keeping air in said pump, and releasing air from said pump, according to said sensing value obtained from said pressure sensor;
• disabling said feedback pressure control in each of said suction stroke of said pump;
• and
• controlling a fluid delivery amount by energizing said solenoid for a period of time.