Abstract:
A fluid supply assembly includes a tank configured for holding a fluid and a pump configured to draw the fluid from the tank, wherein the tank includes a recess and the pump is mounted to the tank in the recess. The pump may be connected to the tank along either, or both of, a first and/or a second surface of the recess, wherein the first surface and the second surface may be orthogonal to one another. The fluid supply assembly may further include a header disposed on a horizontal surface of the tank, the header may include at least a portion thereof which extends into an interior of the tank, wherein the pump may draw the fluid from the tank via the header.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to engine exhaust aftertreatment systems and more particularly to a pump and tank unit used in providing a reductant to the exhaust aftertreatment systems. 
       BACKGROUND 
       [0002]    A selective catalytic reduction (SCR) system may be included in an exhaust treatment or aftertreatment system for a power system to remove or reduce nitrous oxide (NOx or NO) emissions coming from the exhaust of an engine. SCR systems use reductants, such as urea, that are introduced into the exhaust stream to significantly reduce the amount of nitrous oxides (NOx) in the exhaust. 
         [0003]    The construction and installation of the SCR system can be a considerable component of the overall power system cost. Packaging of the SCR system is of particular concern given that most applications for power systems have a limited space requirement. That is, there is only so much space available within a machine, boat, generator housing, etc., in which the power system is installed to accommodate the engine and any required emissions solutions systems, such as the SCR system. 
         [0004]    U.S. Pat. No. 7,895,829 (the &#39;829 patent) discloses an aftertreatment system including an SCR system. The SCR system includes a urea solution tank. A urea solution pump is provided within the urea solution tank. 
       SUMMARY 
       [0005]    The present disclosure provides a fluid supply assembly including a tank configured for holding a fluid, and a pump configured to draw the fluid from the tank, wherein the tank includes a recess and the pump is mounted to the tank in the recess. 
         [0006]    The present disclosure also provides an aftertreatment system that includes an exhaust conduit which transmits exhaust gases from an engine, a fluid supply assembly which introduces a fluid into the exhaust gases. The fluid supply assembly includes a tank configured for holding a fluid, a pump disposed in a recess and configured to draw the fluid from the tank, and an SCR catalyst which receives the exhaust and reductant. The tank includes a recess therein. The pump is supported on two separate sides by the recess and an SCR catalyst which receives the exhaust and reductant. 
         [0007]    The present disclosure also provides a method of manufacturing a fluid supply assembly that includes providing a tank configured to hold the fluid, the tank having a recess, mounting a pump to the tank in the recess, and fluidly connecting the pump to an inside of the tank via a header. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a diagrammatic view of a machine including a power system with an engine and an aftertreatment system. 
           [0009]      FIG. 2  is a diagrammatic view of the aftertreatment system including a reductant supply system including a pump electronics and tank unit (PETU) according to the present disclosure. 
           [0010]      FIG. 3  is a left-side elevation view of a PETU according to the present disclosure. 
           [0011]      FIG. 4  is a right-side elevation view of a PETU according to the present disclosure. 
           [0012]      FIG. 5  is a top elevation view of a PETU according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  is a diagrammatic view of a machine  1  including a cab  2  where an operator  3  sits and a power system  10 . The machine  1  might be a track type tractor (as illustrated), on-highway truck, car, vehicle, off-highway truck, earth moving equipment, material handler, logging machine, compactor, construction equipment, stationary power generator, pump, aerospace application, locomotive application, marine application, or any other device or application requiring a power system  10 . 
         [0014]    The power system  10  includes an engine  12  and an aftertreatment system  14  to treat an exhaust stream  16  produced by the engine  12 . The engine  12  may include other features not shown, such as controllers, fuel systems, air systems, cooling systems, peripheries, drivetrain components, turbochargers, exhaust gas recirculation systems, etc. The engine  12  may be any type of engine (internal combustion, gas, diesel, gaseous fuel, natural gas, propane, etc.), may be of any size, with any number of cylinders, any type of combustion chamber (cylindrical, rotary spark ignition, compression ignition, 4-stroke and 2-stroke, etc.), and in any configuration (“V,” in-line, radial, etc.). 
         [0015]    The aftertreatment system  14  includes an exhaust conduit  18  for delivering the exhaust stream  16  and a Selective Catalytic Reduction (SCR) system  20 . The SCR system  20  includes an SCR catalyst  22 , and a reductant supply assembly  24 . 
         [0016]    In some embodiments, the aftertreatment system  14  may also include a diesel oxidation catalyst (DOC)  26 , a diesel particulate filter (DPF)  28 , and a clean-up catalyst  30 . The DOC  26 , DPF  28 , SCR catalyst  22 , and clean-up catalyst  30  may include the appropriate catalyst or other material, respective of their intended functions, disposed on a substrate. The substrate may consist of cordierite, silicon carbide, other ceramic, a metal structure or other configurations of similar materials. In one embodiment, the substrates may form a honeycomb structure with a plurality of longitudinal channels or cells for the exhaust stream  16  to pass through. The DOC  26 , DPF  28 , SCR catalyst  22 , and clean-up catalyst  30  substrates may be housed in canisters, as shown, or may be integrated into the exhaust conduit  18 . The DOC  26  and DPF  28  may be in the same canister, as shown, or may be separately disposed. Similarly, the SCR catalyst  22  and clean-up catalyst  30  may also be in the same canister, as shown, or may be separately disposed. 
         [0017]    The aftertreatment system  14  is configured to remove, collect, or convert undesired constituents from the exhaust stream  16 . The DOC  26  oxidizes carbon monoxide (CO) and unburnt hydrocarbons (HC) into carbon dioxide (CO2) and water (H2O). The DPF  28  collects particulate matter or soot. The SCR catalyst  22  is configured to reduce an amount of nitrous oxides (NOx) in the exhaust stream  16  in the presence of a reductant. 
         [0018]    The clean-up catalyst  30  may embody an ammonia oxidation catalyst (AMOX). The clean-up catalyst  30  is configured to capture, store, oxidize, reduce, and/or convert reductant that may slip past or breakthrough the SCR catalyst  22 . The clean-up catalyst  30  may also be configured to capture, store, oxidize, reduce, and/or convert other constituents present in the exhaust stream. 
         [0019]    In the illustrated embodiment, the exhaust stream  16  is configured to exit the engine  12 , pass through the DOC  26  and DPF  28 , pass through the SCR catalyst  22 , and then pass through the clean-up catalyst  30  via the exhaust conduit  18 . In the illustrated exemplary embodiment, the SCR system  20  is downstream of the DPF  28  and the DOC  26  is upstream of the DPF  28 . In embodiments where it is included, the clean-up catalyst  30  is downstream of the SCR system  20 . In other embodiments, these devices may be arranged in a variety of orders and may be combined together. In one alternative embodiment, the SCR catalyst  22  may be combined with the DPF  28  with the catalyst material for the SCR deposited on the DPF  28 . Other exhaust treatment devices may also be located upstream, downstream, or within the SCR system  20 . 
         [0020]      FIG. 2  is a diagrammatic view of the aftertreatment system  14  wherein the reductant supply assembly  24  is configured to introduce the reductant into the exhaust stream  16  upstream of the SCR catalyst  22 . The reductant supply assembly  24  may include a reductant supply system  32 , which may also be referred to hereinafter as a pump electronics and tank unit (PETU)  32 , a reductant line  34 , and an injector  36 . In the embodiment illustrated in  FIGS. 1 and 2 , the PETU  32  generally includes a tank  110 , a header  120 , a pump  130  and associated electronics  140 . Embodiments of the PETU  32  will be described in more detail below. 
         [0021]    As illustrated in  FIGS. 2-5 , the tank  110  may include a cap and associated filling passage  111  to introduce reductant into the tank  110 . The tank  110  also includes a recess  112 . The recess  112  is configured such that the pump  130  is at least partially disposed within the recess  112 . Referring in particular to  FIGS. 3-5 , in at least one embodiment, the tank  110  includes grooves  113  disposed along the tank  110  to provide structural strength thereto. The tank  110  may also be configured to include at least one drain  114  disposed along the bottom thereof in order to easily drain the tank  110 , e.g., to drain the tank  110  to remove sludge, to prevent freezing of the reductant within the tank, or to correct a misfilling event. 
         [0022]    As illustrated in  FIGS. 2-5 , the header  120  includes a plurality of ports disposed thereon. According to one exemplary embodiment, the header  120  includes a reductant outlet port  121 , a reductant return port  122  for returning reductant to the tank  110  during a purge event, a coolant inlet port  123  and a coolant outlet port  124 . In the illustrated embodiment, the header  120  also includes an electrical connection  125  which may be connected to a level sensor (not shown), a temperature sensor (not shown), or various other sensors for detecting conditions within the tank  110 . As illustrated in  FIG. 2 , the header  120  may be connected to a coolant loop  126 . The function of the coolant will be described in more detail below. The header  120  may also be connected to a reductant pickup line  127  which extends in proximity to a bottom of the tank  110 . Alternative embodiments include configurations wherein one or more of the ports, lines, sensors and/or connections described above may be omitted or wherein additional ports, lines, sensors and/or connections may be added. 
         [0023]    As illustrated in  FIGS. 2-5 , the pump  130  may be connected to the various ports on the header  120 . For instance, a reductant supply line  151  may connect the reductant outlet port  121  to a reductant inlet  131  on the pump  130 . Similarly, a reductant return line  152  may connect the reductant return port  122  to a reductant outlet  132  on the pump  130 . The pump  130  may also include various connections for coolant. In the illustrated embodiment, the pump  130  includes a coolant inlet  134  connected to a coolant supply line  154  in fluid communication with the coolant outlet port  124  on the tank  110 . In such an embodiment, the pump  130  receives coolant that has already flowed through the tank  120 . The pump  130  may include an internal passage (not shown) in fluid communication with the pump coolant inlet, wherein the internal passage is in thermal communication with a chamber of the pump which contains reductant. Thus, the internal passage of the pump  130  may be heated such that any reductant contained in the pump  130  may be thawed by the coolant. In the illustrated embodiment, the pump  130  includes a coolant outlet  135  for flowing coolant back to the engine  12 . However, such a configuration is only one exemplary embodiment, and alternative configurations are within the scope of this disclosure. 
         [0024]    As illustrated in  FIGS. 2-5 , the pump  130  is disposed at least partially within the recess  112  of the tank  110 . That is, the pump  130  is mounted such that it is bounded on two sides, e.g., a horizontal and vertical side, by edges of the recess  112 . In one embodiment, the pump  130  is mounted to the tank  110  via at least one fastener assembly  136 . In one exemplary embodiment the fastener assembly  136  may include a boss and a means for securing the pump  130  to the boss. According to one exemplary embodiment, the fastener assembly  136  may be spun-welded to the tank  110 , thus reducing a number of through holes in the tank  110 . A support structure of the pump  130  then connects to the fastener assembly  136 . In the present exemplary embodiment, the pump  130  is illustrated as being directly connected to the at least one fastener assembly  136 , and thus the pump  130  is mounted directly to the tank  110  via the fastener assembly  136 . Alternative embodiments include configurations wherein the pump  130  may be disposed on a bracket (not shown) which is mounted to the fastener assembly  136 , and thus the bracket may be the support structure of the pump  130 . 
         [0025]    The pump  130  may further include a filter  137 . The filter  137  may be disposed such that it may be easily removed from the pump  130  in a substantially downward direction parallel with a height of the tank  110 . According to various alternative embodiments, the filter  137  may be disposed separately from the pump in a separate housing; however, even in such an alternative embodiment, the filter  137  is in fluid communication with the pump  130 . 
         [0026]    A coolant flow valve  138  may be connected to the pump  130  or, in an alternative embodiment, on a bracket (not shown) coupled to the tank  110 , e.g., the bracket (not shown) on which the pump  130  may alternatively be mounted. The coolant flow valve  138  may control a flow of coolant from the engine  12  to the tank  110  through a coolant inlet line  153 . In at least one embodiment, the coolant flow valve  138  includes an electronic control capability as discussed below. 
         [0027]    As illustrated in  FIGS. 2-5 , the electronics unit  140  may be disposed adjacent to the pump  130 . In one embodiment, the electronics unit  140  may be mounted directly to the pump  130 , although alternative embodiments include configurations wherein the electronics unit  140  is connected to the bracket (not shown) on which the pump  130  is mounted for connection to the tank  110 . According to one exemplary embodiment, the electronics unit  140  supplies control signals to the pump  130 , injector  36  and coolant flow valve  138 . In the present embodiment, the electronics unit  140  receives signals from a level sensor (not shown) and a temperature sensor (not shown) from the tank  110  and relays those signals to an independent electronics unit (not shown), such as an electronics control unit associated with the main power system  10 . The electronics unit  140  may also receive signals from at least one NOx sensor  160  and relay signals from that at least one NOx sensor  160  to the independent electronics unit. The electronics unit  140 , or the independent electronics unit, may use the NOx sensor  160 , or engine maps, or both to control the introduction of reductant from the reductant supply system  24  to achieve the desired level of NOx reduction while controlling reductant slip through the clean-up catalyst  30 . 
         [0028]    Alternative embodiments include configurations wherein the electronics unit  140  is omitted from the PETU  32  and disposed in an alternative location, e.g., separate from the tank  110 , header  120  and pump  130 . According to one exemplary embodiment, the electronics unit  140  is omitted altogether; in such an alternative embodiment, electronic control signals may alternatively be sent from, and received by, the independent electronics unit. In such an alternative exemplary embodiment, signals from the level sensor (not shown), the temperature sensor (not shown), soot sensors (not shown) and NOx sensor  160  may be sent directly to the independent electronics unit. Combinations of the two configurations are also possible within the scope of this disclosure. 
         [0029]    As shown in  FIGS. 3 and 5 , the PETU  32  has a height h 1 , a length h 1  and a width w 1 . The tank  110  has a height h 2 , a length l 2  and a width w 2 . The pump  130  has a height h 3 , a length l 3  and a width w 3 . As particularly shown in  FIG. 5 , the pump  130  is disposed such that a width of the header  120 , pump  130  and the electronics unit  140  is substantially equal to the width w 1  of the tank  110 . Also, as shown in  FIGS. 3-5 , the height h 1  of the PETU  32  is less than a combined height of the tank  110  and the pump  130  (h 1 &lt;h 2 +h 3 ); a length l 1  of the PETU is less than a combined length of the tank  110  and pump  130  (l 1 &lt;l 2 +l 3 ). As shown in  FIG. 3 , the height direction corresponds to a gravitation field direction, e.g., the height of the tank  110  is the direction in which fluid fills the tank  110 . Advantages of such a configuration are discussed in detail below. 
         [0030]    The injector  36  injects reductant in a mixing section  40  of the exhaust conduit  18  where the reductant may be mixed with the exhaust stream  16 . A mixer (not shown) may also be included in the mixing section  40  to assist the mixing of reductant with the exhaust stream  16 . While other reductants are possible, urea is the most common reductant. 
         [0031]    A heat source (not shown) may also be included to remove soot from the DPF  28  in a process referred to as regeneration. The heat source may also thermally manage the SCR catalyst  22 , DOC  26 , or clean-up catalyst  30 , to remove sulfur from the DOC  26 , DPF  28 , SCR catalyst  22  or clean-up catalyst  30 , or to remove deposits of reductant that may have formed in any of those components or along the exhaust conduit  18 . The heat source may embody a burner, hydrocarbon dosing system to create an exothermic reaction on the DOC  26 , electric heating element, microwave device, or other heat source. The heat could also be applied by operating the engine  12  under conditions to generate elevated exhaust stream  16  temperatures. A backpressure valve or another restriction in the exhaust conduit  18  could also be used to cause elevated exhaust stream  16  temperatures. 
       INDUSTRIAL APPLICABILITY 
       [0032]    Prior art SCR systems utilize reductant supply systems that locate the tank separately a distance away from the pump. The pump and tank are then connected via relatively long lines for transporting the reductant from one to another. This leads to increased risk of line freezing due to failure to remove all reductant from the lines when the machine is shut down. Such a configuration also leads to difficulties with packaging as separate spaces must be found for the pump and tank. The tanks used in the prior art SCR systems also are typically of a size and shape such that even if a pump were to be mounted to the tank, such a combined unit would have at least one dimension that was equal to the sum of the extension of the pump in that dimension and the extension of the tank in that dimension, e.g., the combined height would be equal to the height of the pump plus the height of the tank. Such a configuration also leads to difficulties with packaging. The present disclosure is presented to alleviate such difficulties. 
         [0033]    Referring again to  FIGS. 1 and 2 , in operation, the power system  10  generates the exhaust stream  16 . The exhaust stream flows along the exhaust conduit  18  and is received by the DOC  26 , when included, and the DPF  28 . The DOC  26  and DPF  28  modify the exhaust stream  16  to remove particulate matter and oxidizes carbon monoxide (CO) and unburnt hydrocarbons (HC) into carbon dioxide (CO2) and water (H2O) as discussed above. 
         [0034]    The modified exhaust stream  16  then flows downstream to be treated by the SCR system  20 . The injector  36  injects a reductant into the exhaust stream  18  upstream of the SCR catalyst  22 . While other reductants are possible, urea is the most common reductant. The urea reductant converts, decomposes, or hydrolyzes into ammonia (NH3) and is then adsorbed or otherwise stored in the SCR catalyst  22 . The NH3 is then consumed in the SCR catalyst  22  through a reduction of NOx into nitrogen gas (N2) and water (H2O). 
         [0035]    The injector  36  receives the reductant from the pump  130 , which in turn draws the reductant from the header  120  and the tank  110  along the reductant pickup line  127 . The reductant may undergo filtering within the tank  110 , at the filter  137  and again at the injector  36 , among various other filtering locations. According to various alternative embodiments, the filter  137  may be easily removed from along an overhanging portion of the pump  130  rather than necessitating a removal of the pump  130  from its mounting position in order to access the filter  137 . 
         [0036]    As illustrated in  FIGS. 2-5 , the PETU  32  includes the tank  110  having sufficient capacity for supplying reductant to the exhaust stream  16  during operation of the power system  10 . That is, if the power system  10  typically undergoes a work period of 8 hours between shut-down events, the tank  110  may be sized to provide enough reductant for operation of the power system  10  under typical operating conditions during the 8 hour work period. 
         [0037]    As briefly discussed above, the PETU  32  includes a thermal management system utilizing coolant from the engine  12  in order to thaw, or prevent freezing of, the reductant within the tank  110 , header  120  and pump  130 . In operation, a temperature reading sensed by the temperature sensor in the tank may be sent to the electronics unit  140 . A determination about the condition of the reductant contained in the tank  110  may then be made based on the temperature reading and appropriate actions may be taken based on the determination, e.g., if the temperature reading is below a predetermined threshold, the electronics unit  140  initiates a reductant thawing event. 
         [0038]    One embodiment of the thawing event may include opening the coolant flow valve  138  to allow coolant from the engine, which has a relatively high temperature compared to the frozen reductant, to flow therethrough, into the header  120  and then through the coolant loop  126  of the tank  110 . After flowing through the radiative coolant loop, the coolant then flows back out through the header  120  and into the pump  130 . The coolant then transfers thermal energy to the pump  130  before flowing back to the engine  12 . Once the temperature reading from the tank  110  is above the predetermined threshold, the electronics unit  140  determines the reductant to be thawed and terminates the thawing event, e.g., by closing the coolant flow valve  138 . 
         [0039]    According to various alternative embodiments, the reductant lines  34  may be heated by electrical heaters (not shown) or by water jackets (not shown) heated by engine coolant in order to thaw, or prevent freezing of, reductant contained therein. 
         [0040]    While one embodiment of a method for thawing the tank  110 , header  120  and pump  130  has been described above, the present disclosure is not limited thereto and various other control schemes may alternatively be used to thermally manage the SCR system  20 . 
         [0041]    By locating the tank  110  and pump  130  adjacent to one another with the pump  130  disposed within a recess  112  of the tank  110 , the coolant flow lines, i.e., the coolant inlet line  153  and coolant supply line  154 , from the coolant control valve  138  to the header  120  and from the header  120  to the pump  130 , may be shortened, thereby reducing the overall number of coolant connections as compared to a system where the pump and tank are separately supplied with coolant. 
         [0042]    In contrast to prior art systems wherein the tank  110  and pump  130  are separately mounted, the disclosed system allows for easier packaging and assembly. That is, in the disclosed system, all of the connections related to the reductant supply system  24  are conveniently located in one assembly. The required connections between the tank  110 , header  120 , pump  130  and electronics unit  140  may be preassembled prior to insertion into a particular application, e.g., a machine. 
         [0043]    The disposition of the pump  130  within the recess  112  provides mounting options for providing both vertical and lateral support to the pump  130  in relation to the tank  110 . Using two planes of support may be advantageous in a high-vibration environment, such as those produced in association with power system  10 . As illustrated in  FIGS. 2-5 , having multiple planes of support may reduce movement of the pump  130  along a single plane and provides additional support in the event of a fastener assembly  136  failure. However, the recess  112  also provides easy mounting options if the pump  130  were to be mounted to only one side of the recess  112 , e.g., the pump  130  may be mounted only to the side of recess  112  or only to the bottom of recess  112  depending upon a desired assembly process. 
         [0044]    In one embodiment, the fastener assemblies  136  may be spin-welded to the tank  110 , thereby supplying a quick and inexpensive method for providing the fastener assemblies  136  on the tank  110 . In addition, such a method reduces the number of orifices in the tank and thereby helps to prevent opportunities for leakage from the tank  110 . Such a method also may reduce the total number of parts used in the system, and thus reduces the number of potential failure modes. 
         [0045]    Although the embodiments of this disclosure as described herein may be incorporated without departing from the scope of the following claims, it will be apparent to those skilled in the art that various modifications and variations can be made. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.