A diesel exhaust fluid delivery system and a dual-variable control strategy for adjusting the delivery pressure and the mass flow rate of the fluid passing through the system. The method for operating the system using two operating modes: low flow rate and high flow rate. While operating in the low flow rate operating mode, the speed of a DEF pump remains constant and DEF delivery to the exhaust system is adjusted by controlling a backflow valve. While operating in the high flow rate operating mode, the backflow valve is closed and the speed of the pump is adjusted to regulate DEF delivery to the exhaust system.

A method for operating a device configured to deliver a liquid includes: a) back-suctioning a liquid situated in a pressure line section counter to a usual delivery direction by at least one pump; b) monitoring at least one operating parameter of the at least one pump during the back-suctioning, the at least one operating parameter being representative of a counterpressure that the at least one pump operates against during the back-suctioning; and c) detecting an increase in the counterpressure, and stopping the back-suctioning.

A method for operating a device that conveys a fluid includes: A) detecting activation of the device; B) filling a conveying line with the fluid by operating at least one pump in a conveying direction from at least one tank to at least one injector, and detecting complete filling of the conveying line based on at least one sudden pressure increase at at least one pressure sensor; C) operating the pump and making available fluid at the injector; D) detecting deactivation of the device; and E) partially emptying the conveying line by sucking back the fluid by operation of the at least one pump in a direction counter to the conveying direction. The emptying is stopped if pressure measured at the at least one pressure sensor corresponds to an ambient pressure.

A method and a device for determining the injection quantity or the injection rate of a fluid which is transported to an injector through a hydraulic line and is injected into a reaction space by the injector. The fluid pressure in the hydraulic line is measured by a pressure sensor, the fluid pressure at the injector is determined using the pressure measured by the pressure sensor and a stored transmission function of the hydraulic line, and the injection quantity or the injection rate of the fluid injected by the injector is determined using the fluid pressure determined at the injector.

Disclosed is a method for diagnosing functionality of dosing units of a fluid dosing system comprising at least two dosing units, a tank unit for holding a fluid, and a pump unit for pressurizing the fluid for the dosing units. The method comprises determining a first hydraulic stiffness value on the basis of first pressure variations and determining a second hydraulic stiffness value on the basis of said second pressure variations. The first hydraulic stiffness value and second hydraulic stiffness value are compared. In a case where the first hydraulic stiffness value and second hydraulic stiffness value differ to a certain extent, concluding that malfunction of at least one of said dosing units is at hand, and in a case where the first hydraulic stiffness value and the second hydraulic stiffness value do not differ to said certain extent, concluding that the first and second dosing units function as intended.

A method for controlling a return valve of an exhaust system and to an exhaust system with a control unit which is configured to carry out the method. The method is based on the object of avoiding an overpressure in the line system for urea solution as a result of a reduction in the injection rate. The method includes the steps of determining whether one or more of the following states are present during the operation of the exhaust system: a) an injection rate per unit of time of urea solution of the dosing valve is less than or equal to a predefined injection limit, b) a pressure measured by the pressure sensor in the line system overshoots a predefined first upper pressure limit (P2). The return valve is opened for a first predefined opening duration (Δt1) if states a) and b) are present and at least one of the states has already been present for at least a predefined period of time (Δta). The return valve is closed after the first predefined opening duration (Δt1) has elapsed.

A system including a pump fluidly connected to a fluid reservoir, the pump configured to direct diesel exhaust fluid (DEF) from the fluid reservoir to an injector fluidly connected to the pump via a flow line. The system also includes a first pressure sensor configured to determine fluid pressure at a first location in the flow line between the pump and the injector and a second pressure sensor configured to determine fluid pressure at a second location in the flow line between the pump and the injector. The system further includes an air source coupled to the injector via an air flow line, the air source configured to direct air to the injector via the air flow line and a controller communicatively coupled to the first pressure sensor, the second pressure sensor, and the air source, the controller configured to diagnose the system.

The present disclosure relates to a hydrocarbon dosing system to control dosing of diesel fuel into an exhaust upstream of a vehicle's oxidation catalyst (VOC). The system 100 includes separate inlets (102,104) to allow inflow of a first fluid and the second fluid into the system, and an outlet 116. The first fluid configured to facilitate purging of the second fluid into the VOC through the outlet 116. The system 100 incorporates multiple valves (106, 108, 112) and pressure sensor 114 to control dosing and purging of the fluids. The system 100 provides an intrinsic non-return valve mechanism to restrict the flow of the first fluid into a fluid path of the second fluid, and vice versa. The system 100 provides intrinsic pressure relief mechanism for controlled release of pressure from system 100. The system 100 includes additional optional check valves 208 and filter screens 206 for redundancy purposes.

The invention proposes a method for operating a metering system (32) with a plurality of metering valves (34, 35) for an SCR catalyst system, in which opening times for the injection of reducing agent are calculated for the metering valves (34, 35) based on a metering amount requirement. In the calculations of the opening times, a metering-valve-specific adaptation factor is used, w herein a deviation (Δp) of a system pressure (p.sub.ist) in the metering system (32) from a target pressure (p.sub.soll) and a weighting factor are used for calculation of the metering-valve-specific adaptation factor. The weighting factor depends on a proportion (r.sub.34, r.sub.35) of the required metering amount ((formula (I)), (formula (II)) of the respective metering valve (34,35) in relation to a total metering amount ((formula (I)), (formula (II)) of all metering valves (34, 35).

A reductant dosing system includes: an injector; a fixed displacement pump in fluid communication with the injector; a reductant source in fluid communication with the fixed displacement pump; a pressure sensor assembly configured to detect a pressure of reductant in the reductant dosing system; and a controller communicatively coupled to the fixed displacement pump and to the pressure sensor assembly, wherein the controller is configured to calculate a flow rate of the fixed displacement pump based on at least a calibration value determined based on data received from the pressure sensor assembly.