Patent Description:
Engine systems for vehicles and the like may comprise an aftertreatment module for removing unwanted gaseous emissions or pollutants from the exhaust gases of an internal combustion engine. A selective catalytic reduction (SCR) system may be provided in the exhaust gas stream for removing nitrogen oxides (NOx). An SCR system may comprise a reductant injector located upstream of a catalyst and the reductant injector may inject a liquid reductant into the exhaust gases before they contact the catalyst. Suitable liquid reductants may include anhydrous ammonia, aqueous ammonia and urea. The high temperature of the exhaust gases may evaporate the liquid reductant and upon contact with the catalyst, the gaseous reductant may react with the NOx in the exhaust gas to form nitrogen and water.

The SCR system may comprise a pump for directing reductant from a reductant reservoir to the reductant injector. A suction tube may extend into the reductant reservoir to a flexible filter located at the end of the suction tube. During a purge process the pump may draw reductant from the injector back into the reservoir to prevent damage by freezing. However, in doing so, any air in the filter may also be drawn back into the reservoir and into the filter. At the start of the next operation cycle a priming process may run in which reductant is drawn from the reservoir through the filter and suction tube to the injector. However, the pump may draw the air from the filter back into the pump such that priming fails. Alternatively, the air may be released from the filter through the suction tube slowly during operation due to vibration or sloshing in the reservoir. The resulting air bubbles can cause pump pressure to drop due to aeration therein.

<CIT>, entitled "Urea Reservoir for a Motor Vehicle," describes a liquid reservoir for urea solution having at least one discharge line, which is embodied as an intake line, and which communicates with the reservoir volume via at least one filter element. The filter element comprises at least one filter fabric and/or a non-woven filter material, which when wetted prevents an aspiration of air. A distinguishing feature of the liquid reservoir according to the invention is that the filter element comprises a housing, which defines an accumulator volume, which can be at least partially drained when the reservoir volume is empty.

The present invention provides a filter arrangement for a reductant supply system of a selective catalytic reduction system according to claim <NUM>.

The present invention further provides a reductant supply system for a selective catalytic reduction system according to claim <NUM>.

The present disclosure further provides an engine system comprising an exhaust aftertreatment module for receiving exhaust gas from an internal combustion engine, the exhaust aftertreatment module comprising a selective catalytic reduction system, the selective catalytic reduction system comprising the aforementioned reductant supply system.

By way of example only, embodiments according to the present disclosure are now described with reference to, and as shown in, the accompanying drawings.

The present disclosure is generally directed towards a filter arrangement of a reductant supply system for a selective catalytic reduction system. The filter arrangement comprises a restraining body and a filter mounted to a suction tube in a reductant liquid tank. The restraining body extends radially outwardly from the suction tube and over the filter. The restraining body prevents the filter from, under the effects of buoyancy of gas therein, floating upwardly above a tube inlet of the suction tube and is instead configured to direct the gas towards the tube inlet. As a result, any gas in the filter is removed early in the next operation cycle during a priming process.

<FIG> illustrates an exemplary embodiment of an engine system <NUM> comprising the filter arrangement <NUM> of the present disclosure. The engine system <NUM> may be for providing power and/or drive to a machine. The machine may comprise a work machine or vehicle, such as an excavator, backhoe, articulated truck or the like.

The engine system <NUM> comprises an engine <NUM> receiving air for an air intake <NUM>, such as via a turbocharger <NUM> and/or supercharger <NUM>. The engine <NUM> may be an internal combustion engine, such as a compression-ignition or spark-ignition engine. Fuel, such as diesel, petrol or natural gas, may be selectively provided to engine cylinders in the engine <NUM> to combust with the intake air and drive the pistons, thereby rotating a crankshaft and providing an engine output torque and power. The by-product of the combustion process is exhaust gas, which may be directed from the engine <NUM> towards an exhaust <NUM> via an aftertreatment module <NUM> and optionally the turbocharger <NUM>. The engine system <NUM> may comprise any other suitable component, such as a cooler <NUM> upstream of the engine <NUM>, a supercharger bypass <NUM> and/or a turbine bypass <NUM>.

The exhaust gas exiting the engine <NUM> may comprise unwanted gaseous emissions or pollutants, such as nitrogen oxides (NOx), particulate matter (such as soot), sulphur oxides, carbon monoxide, unburnt hydrocarbons and/or other organic compounds. The exhaust aftertreatment module <NUM> may receive and treat the exhaust gas to remove pollutants prior to directing the exhaust gas to atmosphere via the exhaust <NUM>. The exhaust aftertreatment module <NUM> comprises a selective catalytic reduction or SCR system <NUM> and may comprise a diesel oxidation catalyst <NUM>. The diesel oxidation catalyst <NUM> may be arranged to receive exhaust gases from the engine <NUM> and may be located upstream of the SCR system <NUM>.

The SCR system <NUM>, which is illustrated schematically in <FIG>, comprises an SCR catalyst arrangement <NUM> and a reductant supply system <NUM>. The reductant supply system <NUM> may comprise a reductant injector <NUM> for selectively injecting reductant liquid <NUM> into the exhaust gas directed from the engine <NUM>, such as via the turbocharger <NUM> and/or diesel oxidation catalyst <NUM>. The reductant injector <NUM> may inject reductant liquid <NUM> upstream of the SCR catalyst arrangement <NUM>.

The reductant liquid <NUM> may comprise aqueous urea, aqueous ammonia or the like. The reductant liquid <NUM> may be diesel fluid (DEF) and the DEF may meet the ISO22241 standard and comprise from <NUM>% to <NUM>% urea by weight. The reductant injector <NUM> may selectively inject the reductant liquid <NUM> into the stream of exhaust gas to provide a dose of reductant liquid <NUM> to the SCR catalyst arrangement <NUM>. The high exhaust gas temperature may cause the reductant liquid <NUM> to evaporate and the resulting combination of gases may contact a catalyst substrate in the SCR catalyst arrangement <NUM>. The reductant liquid <NUM> may react with the NOx in the exhaust gas to reduce it to nitrogen and water, which may pass out of the engine system <NUM> via the exhaust <NUM>.

The reductant supply system <NUM> comprises a tank <NUM> for storing reductant liquid <NUM> and a pump <NUM> in fluid communication with the tank <NUM> and the reductant injector <NUM>. The pump <NUM> is configured to draw reductant liquid <NUM> from the tank <NUM> and direct the reductant liquid <NUM> to the reductant injector <NUM>. The reductant supply system <NUM> comprises an outlet or suction tube <NUM> at least partially mounted in the tank <NUM> and in fluid communication with the pump <NUM>. The suction tube <NUM> may extend from inside the tank <NUM> to the pump <NUM> as illustrated or further conduits and/or valves may be located between the tank <NUM> and pump <NUM>.

The suction tube <NUM> comprises a tube inlet <NUM> for receiving reductant liquid <NUM> from the tank <NUM>. The pump <NUM> may selectively draw reductant liquid <NUM> from the tank <NUM> through the tube inlet <NUM>. The suction tube <NUM> may be configured to extend into the tank <NUM> such that the tube inlet <NUM> is below a predetermined level (for example, a minimum fill level below which the SCR system <NUM> is not operational) of reductant liquid <NUM> therein when the SCR system <NUM> is operational. The tube inlet <NUM> may be, in use, the lowest (i.e., lowest along the direction of gravity when the engine system <NUM> is level) point of suction of the suction tube <NUM> as the pump <NUM> operates.

The suction tube <NUM> may extend along a longitudinal axis <NUM> from a centre point of the tube inlet <NUM>. In use, when the engine system <NUM> is in an upright position (such as when the machine it is mounted in is on level ground), the longitudinal axis <NUM> is coaxial with the direction of gravity. The suction tube <NUM> may be configured such that reductant liquid <NUM> may flow in a direction along the longitudinal axis <NUM> when passing in or out of the tube inlet <NUM>.

The reductant supply system <NUM> further comprises the filter arrangement <NUM> mounted to the suction tube <NUM> and the filter arrangement <NUM> is configured to filter the reductant liquid <NUM> prior to being drawn into the suction tube <NUM> and out of the tank <NUM>. The filter arrangement <NUM> of <FIG> is illustrated in further detail in <FIG>. The filter arrangement <NUM> is mounted to the suction tube <NUM> so as to cover the tube inlet <NUM>.

The filter arrangement <NUM> comprises a restraining body <NUM>, a filter mount <NUM> mounting the filter arrangement <NUM> to the suction tube <NUM>, a filter <NUM> mounted to the restraining body <NUM> and a filter outlet <NUM> formed through the restraining body <NUM> and/or filter <NUM>.

The filter <NUM> is for filtering reductant liquid <NUM> drawn from the tank <NUM> into the filter arrangement <NUM> by the pump <NUM>. Substantially all reductant liquid <NUM> drawn from the tank <NUM> and directed to the reductant injector <NUM> by the pump <NUM> may pass through the filter <NUM> prior to entry into the suction tube <NUM>.

The filter <NUM> may be flexible, may comprise a flexible membrane, may comprise a filter fabric and/or may be more flexible than the restraining body <NUM>. The filter <NUM> may be sufficiently flexible such that under the effects of the buoyancy of air therein, the filter <NUM> may be inclined to change in shape, although the restraining body <NUM> may substantially prevent such a change in shape. The filter <NUM> may comprise a 2D or 3D filter and/or a mesh filter and may comprise multiple layers of materials bound together for filtration of the reductant liquid <NUM>.

The filter arrangement <NUM> comprises a filter chamber <NUM> formed at least partially by the filter <NUM> and, optionally, by the restraining body <NUM> and/or filter mount <NUM>. Fluid communicated between the suction tube <NUM> and filter <NUM> may pass through the filter chamber <NUM>. The reductant liquid <NUM> may pass through the filter chamber <NUM> after passing through the filter <NUM> and prior to passing through the suction tube <NUM> when the pump <NUM> draws reductant liquid <NUM> from the tank <NUM> to the reductant injector <NUM>.

The filter chamber <NUM> may be formed within the filter <NUM> and the filter <NUM> may surround the filter chamber <NUM>. The filter <NUM> may comprise at least one filter wall <NUM>, <NUM>, such as upper and lower filter walls <NUM>, <NUM> as illustrated in <FIG>, and the filter chamber <NUM> may be enclosed therebetween. The filter <NUM> may form a pouch or bag as illustrated in <FIG> and <FIG> and may define the filter chamber <NUM> within the pouch.

The filter <NUM> may comprise or define a filter aperture <NUM> for liquid communication between the filter chamber <NUM> and the suction tube <NUM>. The filter aperture <NUM> may extend through the upper filter wall <NUM> and may extend through the pouch. The filter aperture <NUM> may be configured to enable liquid communication between the filter chamber <NUM> and the suction tube <NUM>.

The restraining body <NUM> extends radially outwardly from the filter mount <NUM> and the suction tube <NUM> between a proximal body side <NUM> and a distal body side <NUM>. The term "radially outwardly" may refer to a radial direction <NUM> perpendicular to the direction of gravity, perpendicular to the longitudinal axis <NUM> of the suction tube <NUM> and/or perpendicular to the (main) direction of flow of liquid entering or exiting the suction tube <NUM> at the tube inlet <NUM>.

The proximal body side <NUM> may extend from adjacent to the suction tube <NUM> and the proximal body side <NUM> of the restraining body <NUM> may be closest to the suction tube <NUM> compared to the distal body side <NUM>. The distal body side <NUM> may be furthest from the suction tube <NUM> and may face away from the suction tube <NUM>. In use, the distal body side <NUM> may face downwardly into the tank <NUM> and the proximal body side <NUM> may face upwardly towards the suction tube <NUM> and the top of the tank <NUM>.

The restraining body <NUM> may extend from a body aperture <NUM> to an outer body edge <NUM> between the proximal and distal body sides <NUM>, <NUM>. The proximal and distal body sides <NUM>, <NUM> may comprise any suitable shape, such as rectangular as illustrated in <FIG> and <FIG> or conical as illustrated in <FIG> and <FIG>.

The restraining body <NUM> may comprise a plate and/or be thin walled. The maximum width of the restraining body <NUM>, which may be the maximum diameter or dimension across the proximal and distal body sides <NUM>, <NUM> within the outer body edge <NUM> and across the body aperture <NUM>, may be substantially greater than the maximum thickness of the restraining body <NUM>, which may be the dimension between the proximal and distal body sides <NUM>, <NUM>. In particular, the maximum width may be at least ten times greater than the maximum thickness.

The restraining body <NUM> is rigid and may be substantially more rigid than the filter <NUM>. The restraining body <NUM> may be configured to retain its shape regardless of its orientation and is configured to restrain the shape of the filter <NUM>, which may be more flexible than the restraining body <NUM>. The restraining body <NUM> may comprise a metal or plastic.

The filter <NUM> is attached or mounted to the restraining body <NUM>. The filter <NUM> extends at least partially across the distal body side <NUM> and is mounted adjacent to and/or to the distal body side <NUM>. The filter <NUM> may be mounted on the distal body side <NUM> of the restraining body <NUM> to the suction tube <NUM>. The at least one filter wall <NUM>, <NUM> may be attached to the restraining body <NUM>, such as to the distal body side <NUM>, for example by adhesive. However, adhesive may not be necessary as air in the filter <NUM> may push it towards the restraining body <NUM> and the restraining body <NUM> may restrict the upward movement of the filter <NUM> due to buoyancy. The upper filter wall <NUM> may be mounted to and extend across the distal body side <NUM>. The filter chamber <NUM> may separate the upper and lower filter walls <NUM>, <NUM> from one another. The filter <NUM> may comprise an outer filter edge <NUM>, which may form the outer perimeter of the filter <NUM> furthest from the filter aperture <NUM>, tube inlet <NUM>, filter mount <NUM> and/or body aperture <NUM>.

The outer filter edge <NUM> may extend between the upper and lower filter walls <NUM>, <NUM>. Therefore, the filter chamber <NUM> may be enclosed within the upper and lower filter walls <NUM>, <NUM> and the outer filter edge <NUM>.

The restraining body <NUM> may extend radially outwardly to at least the entire outer perimeter of the filter <NUM>. The restraining body <NUM> may extend over the entire filter <NUM> and the filter <NUM> may extend along the distal body side <NUM> no further than the outer body edge <NUM>. The filter <NUM> may be mounted to the restraining body <NUM> such that the outer filter edge <NUM> does not extend beyond the outer body edge <NUM>.

The restraining body <NUM> may comprise a mesh as illustrated in <FIG> and may comprise a plurality of mesh apertures <NUM> extending therethrough, such as between the proximal and distal body sides <NUM>, <NUM>. The mesh apertures <NUM> may be configured to allow fluid communication from the filter <NUM>, such as through the upper filter wall <NUM>, at the distal body side <NUM>, through the restraining body <NUM> and beyond the proximal body side <NUM>. In particular, the mesh apertures <NUM> may be configured to allow gas trapped in the filter <NUM> to escape from the filter <NUM> and through the restraining body <NUM> via the mesh apertures <NUM>, such as under the effects of buoyancy.

The filter mount <NUM> is for mounting the filter arrangement <NUM> to the suction tube <NUM> such that (a) the filter chamber <NUM> is in fluid communication with the suction tube <NUM> via the filter outlet <NUM> and (b) the filter <NUM> is on the distal body side <NUM> of the restraining body <NUM> to the suction tube <NUM>.

The filter mount <NUM> is mounted to the restraining body <NUM> and/or filter <NUM>. The filter mount <NUM> may be formed from the restraining body <NUM> and/or the filter <NUM>. As illustrated, the restraining body <NUM> may be mounted to the filter mount <NUM> at the body aperture <NUM>, such as by the filter mount <NUM> being mounted in and/or around the body aperture <NUM>. The filter mount <NUM> may be integrated with the restraining body <NUM> or the filter <NUM> or may be a separate component attached thereto.

The filter mount <NUM> may comprise a mount passageway <NUM> extending therethrough and the filter aperture <NUM> may be mounted over the mount passageway <NUM>. The filter mount <NUM> may be mounted to the suction tube <NUM> such that the mount passageway <NUM> is in fluid communication with the tube inlet <NUM>. Therefore, liquid may be drawn from the filter chamber <NUM>, through the filter aperture <NUM> and into the suction tube <NUM>, such as via the mount passageway <NUM> and tube inlet <NUM>.

The filter mount <NUM> may comprise a fastener, such as a thread on the inside of the mount passageway <NUM>, for fastening to a reciprocal fastener, such as a thread, of the suction tube <NUM>. Alternatively, the filter mount <NUM> may be mounted onto the suction tube <NUM> by a push-fit connection.

The filter outlet <NUM> extends from the filter chamber <NUM> and is formed through the restraining body <NUM> and/or filter <NUM>. The filter outlet <NUM> may also extend through the filter mount <NUM>. Therefore, the filter outlet <NUM> may comprise the filter aperture <NUM>, the body aperture <NUM> and/or the mount passageway <NUM>, which may be aligned with each other as illustrated. Reductant liquid may communicate between the filter chamber <NUM> and the suction tube <NUM> through the filter outlet <NUM>. The filter outlet <NUM> is configured to direct liquid along the longitudinal axis <NUM> between the filter chamber <NUM> and the suction tube <NUM>.

The restraining body <NUM> extends radially outwardly from the filter mount <NUM> and is configured to restrain the filter <NUM> such that, under the effect of buoyancy in the tank <NUM> in use, gas in the filter chamber <NUM> is directed towards the filter outlet <NUM>. Such buoyancy arises due to the filter <NUM> being immersed in reductant liquid <NUM> in the tank <NUM>.

In order to direct gas towards the filter outlet <NUM>, the restraining body <NUM> may depend downwardly from the suction tube <NUM> Z and the restraining body <NUM> extends radially outwardly at an acute angle to the longitudinal axis <NUM> away from the filter outlet <NUM>. Thus the restraining body <NUM> may extend at an acute angle to the suction tube <NUM>. As a result, in use the entire filter chamber <NUM> is located below the filter outlet <NUM> and the tube inlet <NUM> and gas travels up the filter chamber <NUM> and into the filter outlet <NUM>.

The following alternative embodiments fall with the scope of the present disclosure. <FIG> and <FIG> illustrate a further embodiment of the filter arrangement <NUM> in which the restraining body <NUM> comprises a thin-walled cone, which may be truncated as shown at the filter outlet <NUM>. Gas in the filter <NUM> may flow upwardly under buoyancy in the filter chamber <NUM> towards the centre of the cone to exit through the filter outlet <NUM>, which is located at the tip of the cone. The term "thin-walled" refers to the distance between the proximal and distal body sides <NUM>, <NUM> which may be less, such as at least ten times less, than the diameter or distance across the restraining body <NUM> within the outer body edge <NUM>. The filter arrangement <NUM> may therefore be rotationally symmetric about the filter outlet <NUM>. In this embodiment the filter <NUM> may comprise a pouch as illustrated entirely enclosing the filter chamber <NUM> other than at the filter outlet <NUM>. The filter may also be shaped as a substantially thin-walled hollow cone as illustrated.

Furthermore, the restraining body <NUM> may be solid and may not comprise mesh apertures <NUM> such that gas cannot escape therethrough. In such an arrangement the filter <NUM> may not comprise an upper filter wall <NUM> extending across the distal body side <NUM>. Instead, a filter wall may be attached at or adjacent to the outer body edge <NUM> and extend across the distal body side <NUM>. The filter chamber <NUM> may be formed between filter wall and the distal body side <NUM>.

In further embodiments the filter mount <NUM> may be integrated with the suction tube <NUM> and the reductant supply system <NUM> may comprise the restraining body <NUM>, the filter mount <NUM> and the suction tube <NUM> as a unitary component.

In use the pump <NUM> is operated to draw reductant liquid <NUM> from the tank <NUM>, through the filter <NUM> into the filter chamber <NUM>, from the filter chamber <NUM> through the filter outlet <NUM>, through the suction tube <NUM> and to the reductant injector <NUM>. Reductant liquid <NUM> may thus be selectively injected into the exhaust gas stream by the reductant injector <NUM>.

At the end of an operating cycle a purge process may be run in which the pump <NUM> is operated to draw any reductant liquid <NUM> back from the reductant injector <NUM> and into the tank <NUM>. However, in such a process air may also be drawn into the tank <NUM>. Due to the construction of the filter <NUM>, much of the gas may be maintained within the filter chamber <NUM>.

It has been identified that a particular cause for air to remain in flexible filters <NUM> after a purge process is that, by virtue of the buoyancy of the air in the flexible filters <NUM>, the filters <NUM> may be inclined to balloon upwardly around the tube inlet <NUM>. This prevents the air from exiting the filter <NUM> and the air may subsequently cause a failure in priming or aeration of the reductant liquid <NUM>.

The present disclosure therefore overcomes such issues by the restraining body <NUM> restricting the filter <NUM> from rising above the tube inlet <NUM>. The restraining body <NUM> therefore ensures that the whole of the filter <NUM> is always below the tube inlet <NUM> and any air therein moves towards and through the tube inlet <NUM> after the purge is completed. During or after priming, in which the pump <NUM> draw reductant liquid <NUM> from the tank <NUM> towards the reductant injector <NUM>, there is then no stored air in the filter that can be released, such as due to machine vibration. Any air in the reductant supply system <NUM> will be quickly driven therefore.

Claim 1:
A filter arrangement (<NUM>) for a reductant supply system (<NUM>) of a selective catalytic reduction system, the reductant supply system (<NUM>) comprising a tank (<NUM>) and a suction tube (<NUM>) mounted at least partially in the tank (<NUM>) for receiving reductant liquid (<NUM>) from the tank (<NUM>), wherein the filter arrangement (<NUM>) comprises:
a rigid restraining body (<NUM>) comprising a distal body side (<NUM>);
a filter (<NUM>) mounted adjacent to and/or to the distal body side (<NUM>) of the restraining body (<NUM>) and extending at least partially across the distal body side (<NUM>) of the restraining body (<NUM>) and at least partially forming a filter chamber (<NUM>);
a filter outlet (<NUM>) from the filter chamber (<NUM>) formed through the restraining body (<NUM>) and/or filter (<NUM>), wherein the filter outlet (<NUM>) is configured to direct liquid along a longitudinal axis (<NUM>) between the filter chamber (<NUM>) and the suction tube (<NUM>); and
a filter mount (<NUM>) mounted to the restraining body (<NUM>) and/or filter (<NUM>), wherein the filter mount (<NUM>) is for mounting the filter arrangement (<NUM>) to the suction tube (<NUM>) such that (a) the filter chamber (<NUM>) is in fluid communication with the suction tube (<NUM>) via the filter outlet (<NUM>) and (b) the filter (<NUM>) is on the distal body side (<NUM>) of the restraining body (<NUM>) to the suction tube (<NUM>),
wherein the restraining body (<NUM>) extends radially outwardly at an acute angle to the longitudinal axis (<NUM>) away from the filter mount (<NUM>) and is configured to restrain the filter (<NUM>) such that, under the effect of buoyancy in the tank (<NUM>) in use, gas in the filter chamber (<NUM>) is directed towards the filter outlet (<NUM>).