Abstract:
A liquid dispenser includes an exterior surface and an interior surface. The interior surface encloses a volume that tapers outwardly in a downward direction so that any horizontal cross-section of the volume fits inside each horizontal cross-section below it from a full to an empty level of the dispenser. The interior surface also includes a projection oriented opposite the exterior surface and configured to limit a motion of solids within the dispenser. The structure so provided enables the solid, e.g., a frozen liquid, to slide to the heated, bottom portion of the dispenser as liquid is drawn from the dispenser thus providing faster melting.

Description:
TECHNICAL FIELD 
     The present application relates to the field of fluidics, and more particularly to managing fluid flow and/or storage in motor vehicles. 
     BACKGROUND AND SUMMARY 
     A motor vehicle may carry a freezable liquid in a dispenser. Examples of freezable liquids include water, windshield washer, and urea mixtures for use in emissions control. During operation, the motor vehicle may draw the liquid from the bottom of the dispenser. At low temperatures, however, the liquid may freeze to solid form and require thawing prior to being drawn out. Thus, in some applications, it may be advantageous to provide heat to the dispenser to thaw the solid, and thereby reclaim the liquid. 
     The rate of thawing may depend on the detailed geometry of the dispenser. Although a dispenser may be designed to have substantially parallel walls, various factors may cause the walls to be non-parallel. Finite dimensional tolerances of the dispenser, which arise during manufacturing, are one such factor. Another factor is that the dispenser may deform subsequent to manufacturing—because it is made of a pliable material or because of expansion, on freezing, of a liquid within it. If the walls taper even slightly inward from the top of the dispenser to the bottom, a frozen solid may be held up and be slow to reach a heated bottom portion of the dispenser. As the thawed liquid is drawn out, further thawing may be limited by convective heat transfer through an air-filled zone at the bottom portion. This effect may limit the rate at which liquid may be drawn from the dispenser. 
     Additionally, when a liquid is thawed in a container having substantially parallel walls, the remaining solid—if it is less dense than the liquid—may float to the top, and convective heat transfer from the bottom of the container to the frozen solid above may be slow. Therefore, U.S. Pat. No. 5,235,823 discloses a container in which ice is thawed to provide cooling, wherein the walls of the container taper outward from the top of the container to the bottom. In this container, the taper prevents ice from floating to the top of the liquid and thereby increases the rate of heat transfer. 
     In the cited reference, heat is transferred to the ice through the walls of the container. Additional problems may arise, however, if heat is provided by an immersion heater set in the container, and the container is disposed in a motor vehicle. In a motor vehicle, where vibration and acceleration may be significant, the possibility of unthawed solids moving freely within the container and contacting the immersion heater may be unacceptable. Further, the problem of the frozen portion floating to the top of the liquid may be irrelevant if the liquid is drawn out of the container and delivered elsewhere during the melting process. 
     The inventor herein has recognized the above problems and issues and has devised a series of approaches to address them. Thus, in one embodiment, a liquid dispenser is provided. The dispenser includes an exterior surface and an interior surface. The interior surface encloses a volume that tapers outwardly in a downward direction so that any horizontal cross-section of the volume fits inside each horizontal cross-section below it from a full to an empty level of the dispenser. The interior surface also includes a projection oriented opposite the exterior surface and configured to limit a motion of solids within the dispenser. 
     Another embodiment provides a system for delivering a liquid to a motor-vehicle component such as an exhaust-aftertreatment device. The system includes a liquid dispenser as described above and a conduit coupled to an opening at a bottom portion of the dispenser. The conduit is configured to conduct the liquid to the motor-vehicle component. The system also includes a heater operatively coupled to a controller and configured to heat at least the bottom portion of the dispenser. 
     The structure so provided enables the solid to slide to the heated, bottom portion of the dispenser as liquid is drawn from the dispenser. This configuration reduces limitations on the rate of thawing of the solid related to the rate of mass transport to the heated, bottom portion of the dispenser. Also, if the solid melts faster than the liquid is drawn from the dispense, the structure holds the solid portion down to increase heat transfer to the solid via the structure. 
     Other embodiments disclosed herein provide different variants of the dispenser, and methods for delivering a liquid to an exhaust-aftertreatment device in a motor-vehicle in accordance with the disclosed configurations. 
     It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the Detailed Description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the Detailed Description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example system for delivering a liquid to an exhaust-aftertreatment device in a motor vehicle, in accordance with the present disclosure. 
         FIG. 2A  shows a section of an example dispenser, in accordance with the present disclosure. 
         FIG. 2B  shows the section of  FIG. 2A  intersected by a pair of horizontal planes, in accordance with the present disclosure. 
         FIG. 2C  shows the intersections of  FIG. 2B  translated into the plane of the page, in accordance with the present disclosure. 
         FIG. 3  shows in cross-section, three example embodiments of a dispenser, in accordance with the present disclosure. 
         FIG. 4  shows an example process for delivering a liquid to an exhaust-aftertreatment device in a motor vehicle, in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows, in schematic detail, an example system for delivering a liquid to an exhaust-aftertreatment device in a motor-vehicle. In some embodiments, the liquid may include a reductant-containing mixture, e.g., a urea-containing mixture. The exhaust-aftertreatment device may include a NOx trap. 
       FIG. 1  shows dispenser  102  configured to contain liquid  104 . A vertical cross-section of the dispenser includes opposing first and second wall segments  106  and  108 . The horizontal distance between the first and second wall segments, at the level of the liquid, increases continuously as the level descends from substantially full level  110  to substantially empty level  112 . 
       FIG. 2A  shows section  200  of example dispenser  102 , which extends from substantially full level  110  to substantially empty level  112 . The illustrated section includes interior surface  202  and exterior surface  204 . The interior surface is configured to contain a liquid so that the level of the liquid is between the substantially full level and the substantially empty level. As shown in  FIG. 2A , the interior surface of the dispenser includes projection  206  oriented opposite the exterior surface. The projection is configured to limit a motion of solids within the dispenser. In other embodiments, the interior surface may include a plurality of projections oriented opposite the exterior surface and configured to limit a motion of solids within the dispenser. In one example, the dispenser may include three projections substantially equivalent to projection  206 , each radiating from the center of the dispenser and set 120° apart from each other. Other embodiments may include two projections, four, five, etc. In the illustrated embodiment, an inner edge  216  of the projection oriented toward the center of the dispenser is oblique, and is biased in the same direction as the tapering of the interior surface. In other embodiments, the inner edge projection  216  may be substantially vertical, or may have a bias different than that of the tapering of the interior surface. 
     In the illustrated embodiment, each horizontal cross section of the interior surface of the dispenser between the substantially full level and the substantially empty level defines a circle; the one, illustrated projection is aligned along a vertical plane that contains a radius of the circle. In embodiments that include a plurality of projections and wherein a horizontal cross section of the interior surface defines a circle, one or more of the projections may be aligned along vertical planes that contain radii of the circle. 
       FIG. 2B  shows section  200  intersected by upper horizontal plane  208  and lower horizontal plane  210 .  FIG. 2B  also shows upper intersection  212  and lower intersection  214 . Upper intersection  212  is a geometric figure defined by the intersection of interior surface  102  with the upper horizontal plane; lower intersection  214  is a geometric figure defined by the intersection of the interior surface with the lower horizontal plane. The shape of section  200  provides that the upper intersection is fittable inside the lower intersection, absent rotation of either intersection, for any upper horizontal plane between the substantially full level and the substantially empty level, and for any lower horizontal plane between the upper horizontal plane and the substantially empty level. 
       FIG. 2C  shows upper intersection  212  and lower intersection  214  translated into the plane of the page, the translation occurring without rotation of either intersection. This drawing shows that the upper intersection is fittable inside the lower intersection. 
     It will be understood from this example that fittability of the upper intersection within the lower intersection may, in certain embodiments, require not only an outward tapering of the walls of the dispenser but also a continuous waning of projection  206  from substantially full level  110  to substantially empty level  112 . Such waning may further include a decrease in one or more dimensions of a horizontal cross section of the projection—i.e., a thinning of the projection and/or a shortening of the projection. In one, non-limiting example, a thickness of the projection at the substantially full level may be 1.5 times the thickness of the projection at the substantially empty level. Accordingly, in embodiments that comprise a plurality of projections akin to projection  206 , each of the plurality of projections may wane continuously from the substantially full level to the substantially empty level. 
     Further, it will be understood that the absolute and relative dimensions of the illustrated dispenser, the illustrated projection, and other parts of the system were chosen to emphasize various features and functions of the system, and for other illustrative purposes, and may be varied from the scale illustrated in the depicted embodiment. 
     Returning now to  FIG. 1 , the illustrated embodiment further includes liquid conduit  114 , valve  116 , exhaust-aftertreatment device  118 , exhaust conduit  120 , and controller  122 . The exhaust conduit may comprise a plurality of segments, those segments interrupted by various devices, which include the exhaust-aftertreatment device. The exhaust-aftertreatment device is configured to receive engine exhaust from one segment of the exhaust conduit and to release treated engine exhaust into another segment of the exhaust conduit. The liquid conduit may likewise comprise a plurality of segments interrupted by various devices. In the illustrated embodiment, the liquid conduit is configured to conduct at least some of the liquid from the dispenser to the exhaust-aftertreatment device. As shown in the drawing, the liquid conduit penetrates the dispenser. Specifically, the interior surface of the dispenser defines an opening below the substantially empty level. The opening is configured to allow at least some of the liquid to flow out of the dispenser. In the illustrated embodiment, the opening is a terminus of the liquid conduit. 
     In the illustrated embodiment, liquid conduit  114  is interrupted by valve  116 , and the valve is actuable by controller  122 . Further, the controller is configured to actuate the valve, and thus, to control a flow of the liquid from the dispenser and to the exhaust-aftertreatment device. 
     In  FIG. 1 , solid  123  is shown within dispenser  102  and is disposed substantially above the level of liquid  104 . The solid may be a frozen form of the liquid; it may form spontaneously when the temperature in the dispenser falls below the freezing point of the liquid. Thus, depending on temperature, the dispenser may include one or more substances from a group consisting of the liquid and a solid derived by freezing the liquid. 
     The illustrated embodiment further includes heater  124 , level sensor  126 , and flow sensor  128 . The heater shown in the drawing is at least partly interior dispenser  102 , is operatively coupled to controller  122 , and is configured to provide heat to at least a bottom portion of the dispenser. In some embodiments, the heater may include an electrical heating element. The level sensor is operatively coupled to the controller and responsive to an amount of the one or more substances in the dispenser. In some embodiments, the level sensor may include a float. The flow sensor is operatively coupled to the controller and responsive to a flow of liquid from the dispenser. 
     In some embodiments, controller  122  may be further configured to regulate a flow of heat from the heater in response to an amount of the one or more substances in the dispenser, in addition to regulating the flow of liquid from the dispenser. In particular, the controller may be configured to increase the flow of heat from the heater when the amount of the one or more substances in the dispenser is above a first threshold and when the flow of liquid from the dispenser is below a second threshold. The controller may further be configured to decrease the flow of heat from the heater when the amount of the one or more substances in the dispenser is below a first threshold or when the flow of liquid from the dispenser is above a second threshold. To estimate the amount of the one or more substances in the dispenser, the controller may interrogate or receive an output from level sensor  126 . To estimate the flow rate, the controller may interrogate or receive an output from flow sensor  128 . 
     The system shown by example in  FIG. 1  may be configured for delivering a liquid reductant to an exhaust-aftertreatment device in a motor-vehicle. As shown, the system may include a vertically mounted dispenser in the motor-vehicle, an interior surface of the dispenser enclosing an outwardly tapering interior volume in a descending vertical direction. In such embodiments, the interior volume may be configured to hold the liquid reductant, and, as illustrated in the drawing, an exhaust injection supply connection may be coupled to a bottom portion of the vertically mounted dispenser. Further, a heater may be operatively coupled to the vertically mounted dispenser and configured to provide heat primarily to the bottom portion of the dispenser. 
       FIG. 3  shows three example embodiments of dispenser  102  (viz.  102 A,  102 B,  102 C) that differ with respect to the disposition of the liquid conduit and the heater. 
     In dispenser  102 A, heater  124 A is exterior the dispenser and below the dispenser. In this embodiment, liquid conduit  114 A penetrates the dispenser from above. 
     In dispenser  102 B, heater  124 B is at least partly interior the dispenser. In this embodiment, liquid conduit  114 B penetrates the dispenser from above. 
     In dispenser  102 C, heater  124 C is at least partly interior the dispenser. In this embodiment, liquid conduit  114 C penetrates the dispenser from below. 
       FIG. 4  shows example process  400  for delivering a liquid to an exhaust-aftertreatment device in a motor-vehicle. The process may be initiated by a motor-vehicle controller, such as controller  122  in  FIG. 1 ; it may be initiated, for example, when a charge of the liquid to the exhaust-aftertreatment device is requested. 
     At  402 , the controller determines whether the charge of liquid to the exhaust-aftertreatment device is complete, or whether additional liquid is to be supplied. If the charge of liquid is not complete, then the process proceeds to  404 . 
     At  404 , a motive force is applied to the liquid to draw it from the dispenser. The motive force may be applied in several different ways. In some embodiments, a valve disposed in a liquid conduit connecting the dispenser to the exhaust-aftertreatment device may be opened. Opening the valve may allow the liquid to flow from the dispenser under the force of gravity. If a pressure differential exists between the dispenser and the exhaust-aftertreatment device, the liquid may flow in response to the pressure differential when the valve is opened. In other embodiments, a pump disposed in the liquid conduit may be activated to draw the liquid from the dispenser to the exhaust-aftertreatment device. In some embodiments, the liquid may be drawn out of the dispenser faster than it accumulates due to a thawing the solid, such that the thawing of the solid effectively limits the rate of delivery of the liquid to the exhaust-aftertreatment device. 
     At  406 , the controller determines whether the flow of liquid from the dispenser exceeds a minimum expected flow threshold. To make this determination, the controller may interrogate or receive an output from a flow sensor disposed in the liquid conduit. If the flow of liquid exceeds the minimum expected flow threshold, then the process returns to  402 . But if the flow of liquid does not exceed the minimum expected flow threshold, then the process continues to  408 . 
     At  408 , the controller determines whether the level of one or more substances in the dispenser exceeds a minimum level threshold. To make this determination, the controller may interrogate or receive an output from a level sensor disposed in the dispenser. If the level of the one or more substances exceeds the minimum threshold, then, at  410 , heat is applied to a bottom portion of the dispenser, and the process returns to  402 . 
     Heat may be applied to at least a bottom portion of the dispenser in order to thaw the solid, the shape of which may conform to the inner surface of the dispenser. Thus, in some embodiments, step  410  may comprise heating a bottom portion of the dispenser, the dispenser including a solid formed from the liquid by freezing and configured to allow the solid to descend to the bottom portion of the dispenser when the dispenser is substantially emptied of the liquid. Further, by virtue of steps  406  and  408 , the rate of heating at  410  may be responsive to the combined level of the solid and the liquid in the dispenser and further responsive to the flow of the liquid from the dispenser. 
     If the controller determines, at  402 , that the liquid charge is complete, then, at  412 , the motive force on the liquid is suspended. The motive force may be suspended, for example, by closing a valve and/or deactivating a pump disposed in a conduit connecting the dispenser to the exhaust-aftertreatment device. Then, at  414 , the application of heat to the dispenser is discontinued. Steps  412  and  414  are also executed from  408 , when it is determined that the level of substance in the dispenser does not exceed the minimum level threshold. 
     The example control and estimation routines disclosed herein may be used with various system configurations. These routines may represent one or more different processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, the disclosed process steps (operations, functions, and/or acts) may represent code to be programmed into computer readable storage medium in a control system. It should be understood that some of the process steps described and/or illustrated herein may in some embodiments be omitted without departing from the scope of this disclosure. Likewise, the indicated sequence of the process steps may not always be required to achieve the intended results, but is provided for ease of illustration and description. One or more of the illustrated actions, functions, or operations may be performed repeatedly, depending on the particular strategy being used. 
     Finally, it should be understood that the systems and methods described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are contemplated. Accordingly, the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and methods disclosed herein, as well as any and all equivalents thereof.