Patent Description:
<CIT> discloses an exhaust after-treatment system associated with a diesel engine includes a diesel exhaust fluid storage unit. The storage unit includes a diesel exhaust fluid tank and a vent system coupled to the tank and configured to regulate flow of air into the tank and fluid vapor out of the tank.

An exhaust after-treatment system associated with a diesel engine and an engine exhaust pipe includes a diesel exhaust fluid storage unit. The storage unit includes a diesel exhaust fluid DEF tank and a vent system coupled to the DEF tank and configured to regulate flow of air into the DEF tank and fluid vapor out of the DEF tank.

The vent system includes a diesel exhaust fluid tank venting control unit arranged to extend into an interior region of the diesel exhaust fluid (DEF) tank through a single unit-mount aperture formed in the top wall of the DEF tank. The tank venting control unit includes a fill-limit valve module located, for example, in the DEF tank and exposed to fluid vapor extant in the DEF tank, a breather-valve module located outside the tank and exposed to the atmosphere, and a vapor-transfer module in fluid communication with each of the fill-limit valve and breather-valve modules. The vapor-transfer module is adapted to transfer fluid vapor discharged from an interior region of the DEF tank through the fill-limit valve module to a DEF vapor recirculation line associated with a tank filler neck coupled to the DEF tank.

In illustrative embodiments, each of the breather-valve, vapor-transfer, and fill-limit valve modules includes a hollow shell made of a plastics material. The three hollow shells cooperate to form a unitary vent housing that is associated with the single unit-mount aperture formed in the top wall of the DEF tank. The shell of the breather-valve module cooperates with either a low-flow membrane or a relatively high-flow membrane to form the breather-valve module. The shell of the fill-limit valve module cooperates with a fill-limit valve to form the fill-limit valve module. And the shell of the vapor-transfer module is interposed between and coupled to each of the shells of the breather-valve and fill-limit valve modules to cause the vapor-transfer module to be interposed between and coupled in fluid communication to each of the breather-valve and fill-limit valve modules.

The breather-valve module includes a membrane receiver and the vent system further includes first and second semi-permeable membranes that cooperate with the shell of the breather-valve module and other components of the tank venting control unit to provide a venting kit. The membrane receiver is formed in the shell that is included in the breathing-valve module and is configured to receive either the first semi-permeable membrane to establish a first embodiment of the breather-valve module or the second semi-permeable membrane to establish a second embodiment of the breather-valve module. The membrane receiver opens downwardly to communicate with an interior chamber that is formed in the shell of the vapor-transfer module and exposed to diesel exhaust fluid vapor in the DEF tank.

The membrane receiver of the breather-valve module includes a small cavity sized to receive a small membrane and a concentric relatively larger cavity sized to receive a relatively larger membrane. In one vent system configuration, the small membrane is mounted in the small cavity to limit the flow of tank vapor therethrough during tank ventilation of the atmosphere to a relatively low flow rate. In another vent system configuration, the relatively larger membrane is mounted in the relatively larger cavity to provide high-flow ventilation and to allow the flow of tank vapor there through to the atmosphere during tank ventilation at a relatively higher flow rate.

Additional features of the present invention will become apparent to those skilled in the art upon consideration of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.

A diesel exhaust fluid (DEF) storage unit <NUM> in accordance with the present invention is used to supply a metered amount of diesel exhaust fluid <NUM> to a mixing zone <NUM> in an exhaust pipe <NUM> coupled to a diesel engine <NUM> as suggested diagrammatically in <FIG>. In mixing zone <NUM>, diesel exhaust fluid <NUM> mixes with an exhaust product (i.e., NOX) <NUM> flowing through exhaust pipe <NUM> away from diesel engine <NUM> to produce a mixture <NUM> that reacts with a suitable catalyst <NUM> provided in a downstream Selective Catalytic Reduction (SCR) converter <NUM> to cause water and nitrogen to be discharged from a downstream end <NUM> of exhaust pipe <NUM> so as to minimize NOX emissions downstream from diesel engine <NUM>.

Diesel exhaust fluid <NUM> is a mixture of ionized water and urea. Diesel exhaust fluid <NUM> is discharged as a liquid into mixing zone <NUM> formed in exhaust pipe <NUM> to mix with filtered exhaust product <NUM> to produce a NOX/DEF mixture <NUM> that is admitted into a downstream SCR converter <NUM> as suggested in <FIG>. Liquid urea in diesel exhaust fluid <NUM> crystallizes when exposed to a sufficient amount of air so DEF storage unit <NUM> is a substantially sealed system designed in accordance with the present invention to store and maintain diesel exhaust fluid <NUM> in a liquid state until it is discharged from DEF tank <NUM> and delivered in metered amounts to mixing zone <NUM> in exhaust pipe <NUM>.

DEF storage unit <NUM> includes a diesel exhaust fluid (DEF) tank <NUM> and a DEF tank venting control unit <NUM> formed to include a fill-limit valve module <NUM>, a vapor-transfer module <NUM>, and a breather-valve module <NUM> as shown illustratively in <FIG>. DEF tank venting control unit <NUM> is mounted in a single unit-mount aperture <NUM> formed in DEF tank <NUM> as suggested in <FIG> and <FIG>. A low-flow DEF tank venting control unit <NUM> in accordance with a first embodiment of the present invention comprises a breather-valve module <NUM> including a low-flow membrane 431MLF as shown in <FIG>. Alternatively, a high-flow DEF tank venting control unit <NUM>' in accordance with a second embodiment of the present invention comprises a breather-valve module <NUM>' including a high-flow membrane 432MHF as shown in <FIG>.

Fill-limit valve module <NUM> is located substantially inside DEF tank <NUM> as suggested in <FIG> and <FIG>. Fill-limit value module <NUM> provides means for controlling flow of fluid vapor 12V (e.g. ammonia gas) associated with diesel exhaust fluid <NUM> from an interior region <NUM> formed in DEF tank <NUM> to a DEF vapor recirculation line <NUM> coupled in fluid communication to vapor-transfer module <NUM> and a tank filler neck <NUM> coupled to DEF tank <NUM> to control shutoff of a fluid-dispensing pump nozzle <NUM> included in a diesel exhaust fluid (DEF) delivery system <NUM> during a tank-refilling activity after DEF tank <NUM> is full.

An inlet check valve <NUM> is provided as suggested in <FIG> to regulate flow of fluid between tank filler neck <NUM> and interior region <NUM> of tank <NUM>. Inlet check valve <NUM> comprises a one-way check valve to allow liquid to flow through tank filler neck <NUM> into tank <NUM> but to block discharge of liquid from tank <NUM> into tank filler neck <NUM>.

Breather-valve module <NUM> is located substantially outside DEF tank <NUM> in an illustrative embodiment as suggested in <FIG> and <FIG>. Breather-valve module <NUM> includes a shell <NUM> and either a semi-permeable membrane 431MLF or 432MHF that is mounted in shell <NUM> and configured to provide breathing means for regulating flow of air from atmosphere <NUM> into interior region <NUM> of DEF tank <NUM> through vapor-transfer and fill-limit valve modules <NUM>, <NUM> to maintain a selected positive vapor pressure in interior region <NUM> without exposing diesel exhaust fluid <NUM> to enough air to change from a normal liquid state to an unwanted crystalline state and also for regulating discharge of DEF vapor 12V from interior region <NUM> of DEF tank <NUM> to atmosphere <NUM> through fill-limit valve and vapor-transfer modules <NUM>, <NUM> to block development of a vapor pressure in interior region <NUM> in excess of a selected maximum pressure.

Vapor-transfer module <NUM> is interposed between and coupled in fluid communication to each of fill-limit valve and breather-valve modules <NUM>, <NUM> in an illustrative embodiment as suggested illustratively in <FIG>. Vapor-transfer module <NUM> comprises a shell <NUM> and a vapor-discharge tube 42T and portions of shell <NUM> and vapor-discharge tube 42T are interposed between fill-limit valve module <NUM> and breather-valve module <NUM> as shown in <FIG>. And each of interior chamber 42C of shell <NUM> and a fluid-conducting channel 42TC formed in vapor-transfer module <NUM> is coupled in fluid communication to each of the fill-limit valve module <NUM> and the breather-valve module <NUM> as shown in <FIG>. During a ventilation operation shown (in solid) in <FIG>, DEF vapor 12V can flow from interior region <NUM> of DEF tank and interior chamber 42C of shell <NUM> through breather-valve module <NUM> to the atmosphere <NUM>. During a refilling operation suggested (in phantom) in <FIG>, DEF vapor 12V extant in interior region <NUM> of DEF tank <NUM> and interior chamber 42C of shell <NUM> of vapor-transfer module <NUM> can flow through fill-limit valve module <NUM> and vapor-conducting channel 42TC of vapor-discharge tube 42T of vapor-transfer module <NUM> to DEF vapor recirculation line <NUM>.

DEF tank venting control unit <NUM> is arranged to extend into interior region <NUM> of DEF tank <NUM> through a single unit-mount aperture <NUM> formed in a top wall <NUM> of DEF tank <NUM> as suggested in <FIG> and <FIG>. Fill-limit valve module <NUM> of DEF tank venting control unit <NUM> is located substantially in interior region <NUM> of DEF tank <NUM> and is exposed to diesel exhaust fluid <NUM> and fluid vapor 12V extant in interior region <NUM> as suggested in <FIG>. Breather-valve module <NUM> of unit <NUM> is located outside of interior region <NUM> in an illustrative embodiment and is formed to include an interior chamber 43C in fluid communication with atmosphere <NUM> as suggested in <FIG>.

Each of the breather-valve, vapor-transfer, and fill-limit modules <NUM>, <NUM>, and <NUM> include a hollow shell (e.g. shell <NUM>, <NUM>, and <NUM>) made of a plastics material as suggested in <FIG> and <FIG>. The three shells <NUM>, <NUM>, and <NUM> cooperate to form a unitary vent housing <NUM> that is associated with the single unit-mount aperture <NUM> formed in top wall <NUM> of DEF tank <NUM> as suggested in <FIG>. Vent housing <NUM> provides a compact size and minimized height above top wall <NUM> of DEF tank <NUM> in accordance with the present invention to allow more space in interior region <NUM> of DEF tank <NUM> for tank volume and to fit in a single unit-mount aperture <NUM> formed in top wall <NUM> of DEF tank <NUM>.

Breather-valve module <NUM> includes either a semi-permeable membrane 431MLF or a semi-permeable membrane 432MHF that is mounted in shell <NUM> of breather-valve module <NUM> to communicate fluidly with an interior chamber 42C formed in vapor-transfer module <NUM> and interior chamber 43C formed in shell <NUM> of breather-valve module <NUM>. Each semi-permeable membrane 431MLF and 432MHF is configured to (<NUM>) block flow of liquid fluid <NUM> from chamber 42C into a fluid-transfer tube 43T included in breather-valve module <NUM>, (<NUM>) allow some fluid vapor 12V to pass from chamber 42C to atmosphere <NUM> through interior chamber 43C as long as a positive pressure is maintained in interior region <NUM> of DEF tank <NUM>, and (<NUM>) allow some air to pass from atmosphere <NUM> into interior region <NUM> of DEF tank <NUM> in sequence through interior chamber 43C, interior chamber 42C, and the fill-limit valve module <NUM> to dissipate any unwanted negative pressure (i.e., vacuum) that might develop in interior region <NUM> of DEF tank <NUM> owing to exposure of DEF tank <NUM> to various external environmental conditions such as, for example, cool evening temperatures and without causing crystallization of the liquid diesel exhaust fluid <NUM> stored in DEF tank <NUM>.

Fill-limit valve module <NUM> includes a body <NUM> and a fill-limit vent valve <NUM>. Fill-limit valve <NUM> comprises a float <NUM> and a closure <NUM> coupled to an upper portion of float <NUM> and arranged to move up and down on liquid diesel exhaust fluid <NUM> admitted from interior region <NUM> of DEF tank <NUM> into a float chamber <NUM> formed in body <NUM> to receive float <NUM> therein as suggested in <FIG>. Body <NUM> comprises a valve-receiver tube 60T and suitable valve-support means 60V for retaining fill-limit vent valve <NUM> inside tube 60T after valve <NUM> has been installed in float chamber <NUM> in vent housing <NUM>. Valve-support means 60V is located inside front chamber <NUM> and is coupled to valve-receiver tube 60T as shown, for example, in <FIG>.

When installed in a membrane receiver 43R formed in breather-valve module <NUM>, each of semi-permeable membranes 431MLF and 432MHF have an underside in fluid communication with fluid vapor 12V extant in interior chamber 42C of vapor-transfer module <NUM> and a topside in fluid communication with atmospheric air <NUM> extant in interior chamber 43C of breather-valve module <NUM> as suggested in Figs. <NUM>-<NUM>. Membrane 431MLF is configured to provide a relatively low-flow membrane of a relatively small size as suggested in Fig. <NUM>. In contrast, membrane 432MHF is configured to provide a relatively high-flow membrane of a relatively larger size as suggested in Fig. <NUM>. These membranes 431MLF and 432MHF are configured to be mounted in a membrane receiver 43R formed in breather-valve module <NUM> and are interchangeable as suggested in Figs. <NUM>-<NUM> to change flow rate of DEF vapor 12V discharged from DEF tank <NUM> via breather valve module <NUM>. In illustrative embodiments, each membrane is a one layer PTFE membrane.

Membrane receiver 43R of breather-valve module <NUM> lies under a fluid-transfer tube 43T included in shell <NUM> of breather-valve module <NUM> as suggested in <FIG>. Membrane receiver 43R comprises a large membrane-receiving cavity 43RL that is sized to receive the relatively larger high-flow membrane 432MHF therein and open downwardly toward interior chamber 42C of vapor-transfer module <NUM> and interior region <NUM> of DEF tank <NUM> as suggested in <FIG>, <FIG>, and <NUM>. Membrane receiver 43R also comprises a relatively smaller membrane-receiving cavity 43RS that is sized to receive the relatively smaller low-flow membrane 431MLF therein and open downwardly toward interior chamber 42C of vapor-transfer module <NUM> and interior region <NUM> of DEF tank <NUM> as suggested in <FIG> and <FIG>. Small cavity 43RS is located between fluid-transfer tube 43T and large cavity 43RL as suggested in <FIG>.

Each membrane 431MLF and 432MHF is a filter medium which allows air to go through but blocks liquid flow in both directions. The size of the membrane 431MLF, 432MHF defines the ventilation area and directly affects how much air can flow through the membrane in time to determine, for example, how quickly over-pressure conditions or vacuum conditions in the tank can be relieve by discharge of pressurized fluid vapor 12V from DEF tank <NUM> or admission of outside air into DEF tank <NUM>.

The selection of which membrane 431MLF or 432MHF to use depends on the SCR system design. For example, larger membrane 432MHF will often be used in versions of an SCR system where there is little risk of tank overfilling and the large membrane is used only for tank ventilation. In contrast, small membrane 431MLF could be used in an SCR system where there might be a risk of tank overfilling.

If the tank ventilation flow is too great, then there is a risk that the DEF tank <NUM> could be overfilled (for example, during repeated refilling), because the pressure in DEF tank <NUM> which builds up at the end of the refilling would be ventilated too quickly allowing more and more liquid DEF fluid <NUM> to be added to DEF tank <NUM>. Such liquid DEF fluid <NUM> could fill interior region <NUM> of DEF tank <NUM>. That condition is to be avoided since DEF fluid freeze in an overfilled DEF tank <NUM> during winter could lead to ice expansion and damage to DEF tank <NUM>. This is one reason why the kit in accordance with the present invention provides a small low-flow membrane 431MLF option so as to provide limited ventilation flow which is sufficient to compensate for small pressure changes-especially during vacuum conditions created in DEF tank <NUM> by tank pump <NUM>. In an SCR system in which membrane 431MLF is used in accordance with the present invention, another vent membrane (not shown) would be provided in an SCR cap to allow for high ventilation flow which does not affect the tank refilling as long as that vent membrane is included in a cap that is demounted during tank refilling.

An illustrative exhaust after-treatment system <NUM> is shown diagrammatically in <FIG>. System <NUM> is associated with diesel engine <NUM> and comprises DEF storage unit <NUM> and a DEF transfer system <NUM> coupled to DEF storage unit <NUM> and to an exhaust pipe <NUM> that is coupled to a diesel engine <NUM>.

Exhaust pipe <NUM> is configured to mate with and receive exhaust product <NUM> discharged from diesel engine <NUM> through an exhaust output port 18P formed in diesel engine <NUM> as suggested in <FIG>. Exhaust pipe <NUM> comprises, in series, an upstream conduit <NUM>, a diesel particulate filter <NUM>, a midstream conduit <NUM>, a selective catalytic reduction (SCR) converter <NUM>, and a downstream conduit <NUM> as suggested in <FIG>. Exhaust product <NUM> discharged from diesel engine <NUM> and flowing through upstream exhaust conduit <NUM> comprises nitrogen oxides (NOx) and particulate matter (PM). The particulate matter is trapped in diesel particulate trap <NUM> to cause filtered exhaust product <NUM> to flow away from diesel particulate trap <NUM> through midstream conduit <NUM>. Owing to operation of converter <NUM> and metered discharge of diesel exhaust fluid <NUM> into mixing zone <NUM> in midstream conduit <NUM>, diesel exhaust fluid <NUM> mixes with filter exhaust product <NUM> in mixing zone <NUM> to produce a NOx/DEF mixture <NUM> that is then converted in SCR converter <NUM> to water and nitrogen for discharge from exhaust pipe <NUM> through downstream conduit <NUM> as suggested in <FIG>.

A diesel exhaust fluid (DEF) transfer system (means) <NUM> is provided for injecting a metered flow of diesel exhaust fluid <NUM> discharged from DEF tank <NUM> into the mixing zone <NUM> formed in midstream conduit <NUM> of filler neck <NUM> as suggested in <FIG>. In illustrative embodiments, DEF transfer system <NUM> comprises, in series, a discharge conduit <NUM>, a fluid pump <NUM>, a fluid meter <NUM>, and a fluid-discharge nozzle <NUM> coupled in fluid communication to mixing zone <NUM> as suggested in <FIG>. In illustrative embodiments, the diesel exhaust fluid <NUM> discharged into mixing zone <NUM> hydrolyzes into ammonia gas (NH<NUM>) which mixes with flowing filtered exhaust product <NUM> to produce a mixture <NUM> that flows into SCR converter <NUM>. Ammonia (NH<NUM>) and Nitrogen Oxides (NOx) react with the catalyst <NUM> provide in SCR converter <NUM> to form nitrogen and water.

During tank refilling activity (before shutoff), fluid-dispensing pump nozzle <NUM> is on and dispenses liquid diesel exhaust fluid <NUM> into interior region <NUM> of DEF tank <NUM> via tank filler neck <NUM>. Fluid level rises in interior region <NUM> to displace air and fuel vapor exhaust in interior region <NUM>. Fuel vapor 12V exits interior region <NUM> through first and second vent apertures 60T1, 60T2 formed in valve-receiver tube 60T of body <NUM> of fill-limit valve module <NUM> and flows through float chamber <NUM> to DEF vapor recirculation line <NUM> and tank filler neck <NUM> as suggested in <FIG>.

At shutoff, float <NUM> has risen in float chamber <NUM> formed in tube 60T to cause closure <NUM> to close the aperture opening into interior chamber 42C formed in vapor-transfer module <NUM>. This closure increases pressure in interior region <NUM> of DEF tank <NUM> and provides shutoff for DEF delivery system <NUM> in a normal way.

A breathing operation begins in breather-valve module <NUM> (after shutoff) using semi-permeable membrane 431MLF or 432MHF. Semi-permeable membrane 431MLF or 432MHF restricts discharge of fluid vapor 12V and liquid diesel exhaust fluid <NUM> to atmosphere <NUM> through interior chamber 43C but allows DEF tank <NUM> to breath to admit atmospheric air into interior region <NUM> of DEF tank <NUM> as needed so as to minimize unwanted high-pressure and negative-pressure conditions that might otherwise develop in DEF tank <NUM> under certain operating conditions. Air and fluid vapor 12V are able to flow between atmosphere <NUM> and interior region <NUM> of DEF tank <NUM> in accordance with predetermined flow criteria established by design of the semi-permeable membrane 431MLF (low-flow) or 432MLF (high-flow) via the interior chamber 42C of vapor-transfer module <NUM> during normal operating conditions of system <NUM>.

DEF tank venting control valve <NUM> is configured to manage operation venting of DEF tank <NUM> to provide compensation of vacuum created by the delivery pump <NUM> and compensation of over/under pressure created by environmental changes (e.g. temperature, atmospheric pressure, etc.). DEF tank venting control valve <NUM> is also configured to manage refilling ventilation to provide ventilation of DEF tank <NUM> during refilling and stop ventilation after fluid <NUM> in DEF tank reaches a defined fill level.

An exhaust after-treatment system <NUM> adapted to supply a metered amount of diesel exhaust fluid <NUM> to a mixing zone <NUM> in an exhaust pipe <NUM> is coupled to a diesel engine <NUM> as suggested in <FIG>. System <NUM> comprises a diesel exhaust fluid tank venting control unit <NUM> shown diagrammatically in <FIG>. As suggested in <FIG>, tank venting control unit <NUM> includes a fill-limit valve module <NUM> adapted to receive diesel exhaust fluid <NUM> from a diesel exhaust fluid tank <NUM>, a breather-valve module <NUM> exposed to the atmosphere <NUM>, and a vapor-transfer module <NUM> interposed between and coupled in fluid communication to each of fill-limit valve module <NUM> and breather-valve module <NUM>.

Breather-valve module <NUM> includes an interior chamber 43C and a semi-permeable membrane 431MLF or 432MHF as suggested in <FIG> and <FIG>. One of those membranes will be selected and mounted in interior chamber 43C as suggested in <FIG> so that it has a topside exposed to atmospheric air <NUM> admitted into the interior chamber and an underside exposed to fluid vapor 12V associated with diesel exhaust fluid <NUM> in the diesel exhaust fluid tank <NUM> and fluid vapor 12V conducted through vapor-transfer module <NUM> as suggested.

Breather-valve module <NUM> is formed to include a membrane receiver 43R that comprises a lower portion of interior chamber 43C as suggested in <FIG>. Membrane receiver 43R is arranged to open downwardly toward an interior chamber 42C formed in vapor-transfer module <NUM> as suggested in <FIG>. Membrane receiver 43R is and adapted to communicate with an interior region <NUM> of diesel exhaust fluid tank <NUM> via the interior chamber 42C of vapor-transfer module <NUM> when the diesel exhaust tank venting control unit <NUM> is mounted in an aperture <NUM> formed in a top wall <NUM> of diesel exhaust fluid tank <NUM> and one of the semi-permeable membranes 431MLF or 432MHF is mounted in membrane receiver 43R.

Membrane receiver 43R comprises a small membrane-receiving cavity 43RS arranged to lie in spaced-apart relation to the interior chamber 42C of vapor-transfer module <NUM> and a relatively larger membrane-receiving cavity 43RL arranged to lie between the small membrane-receiving cavity 43RS and the interior chamber 42C of vapor-transfer module <NUM> as suggested in <FIG>. The selected membrane 431MLF or 432MHF is mounted in only one of the small and relatively larger membrane-receiving cavities 43RS, 43RL as suggested in <FIG>.

The selected membrane is one of a low-flow membrane 431MLF sized to fit in the small membrane-receiving cavity 43RS as suggested in <FIG> and a relatively larger high-flow membrane 432MHF sized to fit in the relatively larger membrane-receiving cavity 43RL as suggested in <FIG>. These membranes are selected from a kit comprising the low-flow and high-flow membranes 431MLF, 432MHF as suggested in <FIG>. By providing a kit in accordance with the present invention, it is easy to change OPERATION VENTING flow associated with breather-valve module <NUM> simply by exchanging one membrane for another as described herein. Low-flow membrane 431MLF is a round disk having a first diameter and the relatively larger high-flow membrane 432MHF is a round disk having a second diameter that is greater than the first diameter as shown, for example, in <FIG>.

Diesel exhaust fluid tank <NUM> has a top wall <NUM> formed to include a unit-mount aperture <NUM> as shown, for example, in <FIG> and <FIG>. Vapor-transfer module <NUM> includes a shell <NUM> comprising a plate <NUM> and a downwardly extending endless rim <NUM> coupled to a perimeter edge of plate <NUM> as shown in <FIG>. Rim <NUM> of shell <NUM> is arranged to mate with an upwardly facing portion of top wall <NUM> of diesel exhaust fluid tank <NUM> bordering unit-mount aperture <NUM> as shown in <FIG> to locate plate <NUM> above unit-mount aperture <NUM> and place interior chamber 42C of vapor-transfer module <NUM> bounded by plate <NUM> and the downwardly extending endless rim <NUM> in communication with an interior region <NUM> formed in diesel exhaust fluid tank <NUM> via unit-mount aperture <NUM> formed in top wall <NUM> of diesel exhaust fluid tank <NUM>.

Breather-valve module <NUM> includes an upright shell <NUM> coupled to a topside of plate <NUM> as suggested in <FIG> and <FIG>. Upright shell <NUM> is arranged to extend upwardly away from interior region <NUM> of diesel exhaust fluid tank <NUM> as shown, for example, in <FIG>. Fill-limit valve module <NUM> includes a pendant shell <NUM> coupled to an underside of plate <NUM> as suggested in <FIG> and <FIG>. Pendant shell <NUM> is arranged to extend downwardly into interior region <NUM> of diesel exhaust fluid tank <NUM> as suggested in <FIG>.

Vapor-transfer module <NUM> further includes a vapor-discharge tube 42T adapted to be coupled to a DEF vapor recirculation line <NUM> and coupled to the topside of plate <NUM> to align with a fill-limit vapor-discharge aperture 421A formed in plate <NUM> as suggested in <FIG>. Vapor-discharge tube 42T is coupled to the topside of plate <NUM> as shown in <FIG> to receive pressurized fluid vapor 12V discharged from interior region <NUM> of diesel exhaust fluid tank <NUM> via the float chamber <NUM> formed in valve-receiver tube 60T and the fill-limit vapor discharge aperture 421A formed in plate <NUM>.

Vapor-discharge tube 42T is formed to include a vapor-conducting channel 42TC that is arranged to receive fluid vapor 12V discharged from interior region <NUM> of diesel exhaust fluid tank <NUM> through fill-limit valve module <NUM> and to conduct such fluid vapor 12V to a DEF vapor recirculation line <NUM> associated with an output end 42TD of vapor-discharge tube 42T. Vapor-discharge tube 42T includes an elongated proximal portion 42TP that is arranged to overlie plate <NUM> and a portion of endless rim <NUM> and a distal portion 42TD that is arranged to extend away from rim <NUM> to locate proximal portion 42TP between breather-valve module <NUM> and distal portion 42TD as suggested in <FIG> and <FIG>.

Breather-valve module <NUM> includes a vertically extending fluid-transfer tube 43T and a tube-support base 43B as shown, for example, in <FIG> and <FIG>. Tube-support base 43B is coupled to fluid-transfer tube 43T cooperatively to form the interior chamber 43C of breather-valve module <NUM> as shown I <FIG> and coupled to plate <NUM> to locate fluid-transfer tube 43T above plate <NUM> as shown in <FIG>. Vapor-discharge tube 42T is arranged to extend horizontally in a direction away from the vertically extending fluid-transfer tube 43T as shown, for example, in <FIG>.

Fill-limit valve module <NUM> includes a valve-receiver tube 60T having a lower end located in interior region <NUM> of diesel exhaust fluid tank <NUM> and an upper end coupled to the underside of plate <NUM> and surrounded by endless rim <NUM> as shown, for example, in <FIG>. Valve-receiver tube 60T is formed to include a float chamber <NUM> exposed to DEF vapor 12V extant in interior region <NUM> of diesel exhaust fluid tank <NUM> and arranged to open into fill-limit vapor discharge aperture 421A formed in plate <NUM> as shown, for example, in <FIG> Valve-receiver tube 60T is located in laterally spaced-apart relation to the breather-valve module <NUM> that is coupled to plate <NUM>.

Fluid-transfer tube 43T of breather valve module <NUM> is formed to include a fluid-conducting channel that provides a first portion of interior chamber 43C as suggested in <FIG>. Tube-support base 43B is formed to provide a membrane receiver 43R that provides a second portion of interior chamber <NUM> to cause membrane receiver 43R to lie in fluid communication with the fluid-conducting channel as also suggested in <FIG>. The selected semi-permeable membrane 431MLF or 432MHF is arranged to lie in membrane receiver 43R to regulate fluid flow between the fluid-conducting channel of fluid transfer tube 43T and vapor-transfer module <NUM> as suggested in <FIG> and shown in <FIG>.

Claim 1:
An exhaust after-treatment system adapted to supply a metered amount of diesel exhaust fluid (<NUM>) to a mixing zone (<NUM>) in an exhaust pipe (<NUM>) coupled to a diesel engine (<NUM>), the system comprising
a diesel exhaust fluid tank venting control unit (<NUM>) including a fill-limit valve module (<NUM>) adapted to receive diesel exhaust fluid (<NUM>) from a diesel exhaust fluid tank (<NUM>), a breather-valve module (<NUM>) exposed to the atmosphere (<NUM>), and a vapor-transfer module (<NUM>) interposed between and coupled in fluid communication to each of the fill-limit valve module (<NUM>) and the breather-valve module (<NUM>), wherein the breather-valve module (<NUM>) includes an interior chamber (43C) and a semi-permeable membrane (431MLF, 431MHF) having a topside exposed to atmospheric air admitted into the interior chamber (43C) and an underside exposed to fluid vapor (12V) associated with diesel exhaust fluid (<NUM>) in the diesel exhaust fluid tank (<NUM>) and fluid vapor (12V) conducted through vapor-transfer module (<NUM>),
wherein the breather-valve module (<NUM>) is formed to include a membrane receiver (43R) that is arranged to open downwardly toward an interior chamber (42C) formed in the vapor-transfer module (<NUM>)and adapted to communicate with an interior region (<NUM>) of the diesel exhaust fluid tank (<NUM>) via the interior chamber (42C) of the vapor-transfer module (<NUM>) when the diesel exhaust tank venting control unit (<NUM>) is mounted in an aperture (<NUM>) formed in a wall (<NUM>) of the diesel exhaust fluid tank (<NUM>) and the semi-permeable membrane (431MLF, 431MHF) is mounted in the membrane receiver (43R), and
wherein the membrane receiver (43R) comprises a small membrane-receiving cavity (43RS) arranged to lie in spaced-apart relation to the interior chamber (42C) of the vapor-transfer module (<NUM>) and a relatively larger membrane-receiving cavity (43RL) arranged to lie between the small membrane-receiving cavity (43RS) and the interior chamber (42C) of the vapor-transfer module (<NUM>) and the membrane (431MLF, 431MHF) is mounted in only one of the small and relatively larger membrane-receiving cavities (43RS, 43RL).