An SCR device for a motor vehicle, comprising a tank for storing reducing liquid, an injection device for injection of the reducing liquid into an exhaust gas system of a motor vehicle, a liquid conduit for delivering reducing liquid from the tank to the injection device, a feed pump for conveying reducing liquid in the conduit, and a valve arrangement in the conduit, the valve arrangement designed to interrupt an injection flow in the conduit when the tank-side pressure is greater, than the injection device-side pressure in the conduit by less than an injection threshold value, and to allow the injection flow to pass when the tank-side pressure is greater by at least the injection threshold, the valve arrangement designed to interrupt a return flow in the conduit from the injection device to the tank when the injection device-side pressure is greater than the tank-side pressure by less than a return threshold value, and to allow the return flow to pass through when the injection device-side pressure is greater than the tank-side pressure in the conduit, by at least the return threshold value, the injection threshold value being greater than the return threshold value.

A heat-insulated pipe assembly includes a pipe allowing a fluid to flow therethrough, and a heat insulating member covers at least a part of the pipe. The pipe is used in an exhaust gas purification system using an SCR catalyst. The heat insulating member has a closed-cell structure and suppresses an increase in a temperature of the fluid due to heat exchange with air. In the exhaust gas purification system using the SCR catalyst, the interior of the pipes is thermally insulated from the exterior by the heat insulating member. Thereby an increase in the temperature of the fluid flowing through the pipe due to heat exchange with air is suppressed.

An object is to prevent abrasion inside an addition valve and clogging of the addition valve due to an increase in the particle diameter of precipitates. A first control is performed by which a pump is caused to operate in such a way as to return urea solution contained in the addition valve and a urea solution channel to a tank by a predetermined quantity. After the lapse of a certain time after the end of the first control, a second control is performed by which the pump is caused to operate in such a way as to return the urea solution remaining in the addition valve and the urea solution channel thoroughly to the tank.

An exhaust gas purification apparatus includes: a reduction catalyst converter that reduces and purifies nitrogen oxides in exhaust gas; a tank that stores a liquid reducing agent or precursor thereof; and an injection nozzle that injects the liquid reducing agent or precursor thereof stored in the tank on an exhaust gas upstream side of the reduction catalyst converter. Some of the exhaust gas flowing through an exhaust pipe is diverted to the tank by a bypass pipe, to cause an exchange of heat between the diverted exhaust gas and the liquid reducing agent or precursor thereof stored in the tank, thereby thawing the liquid reducing agent or precursor thereof frozen in the tank.

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.

An injector for injecting a reagent includes an axially translatable valve member positioned within a housing. An electromagnet is positioned within the housing and includes a coil of wire positioned proximate the valve member such that the valve member moves between a seated position and an unseated position relative to an orifice in response to energizing the electromagnet. A connector coupled to the housing includes an inlet tube concentrically aligned with and surrounding a return tube. The inlet tube is adapted to receive pressurized reagent from a source of reagent. The return tube is adapted to return reagent to the source.

Tank for a liquid solution based on water and urea which is suitable for being combined with a selective catalytic reduction system. The tank comprises: a container including an upper wall; a filling pipe union which is positioned on the upper wall of the container and which is suitable for introducing the liquid solution; a lower opening, from which the liquid solution being introduced passes into the container and which protrudes with respect to the upper wall towards the interior of the container; a closure float which is positioned in the container and which is connected to the lower opening and which is configured so as to raise and close the lower opening once the liquid solution in the container reaches a predetermined level.

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.

A sensor head for being arranged in an orifice of a fluid tank includes an opening in fluid communication with a fluid return line returning a fluid to the fluid tank and a bubble reducer device disposed at the opening. The bubble reducer device is configured to block bubbles in the fluid in the fluid return line while the fluid passes through the bubble reducer device during operation.