APPARATUS FOR STORING NOx REDUCTANT ON A VEHICLE

Abstract

Apparatus is disclosed for storing a liquid NOx reductant on a vehicle. The apparatus comprises a container for containing the liquid NOx reductant, a first heating device located in the container and adapted to heat the NOx reductant in use, and a tube that has a first end adapted to be submerged in the liquid NOx reductant in the container in use. The tube is adapted to extract liquid NOx reductant from the container and the tube includes a second heating device extending along at least a portion of the length of the tube that is located within the container.

Description

TECHNICAL FIELD

The invention relates to apparatus for storing NO_x reductant on a vehicle.

BACKGROUND OF THE INVENTION

Diesel engines are typically more efficient than gasoline engines, with regard to fuel economy and emit less greenhouse gasses. However, diesel engines typically produce emissions containing higher concentrations of nitrogen oxides (NO_x) compared to gasoline engines fitted with three-way catalysts.

SUMMARY OF THE INVENTION

One method that has been employed to remove NO_x from diesel exhaust utilizes selective catalytic reduction (SCR) of NO_x with a liquid nitrogen containing reductant, such as aqueous urea. NO_x and the liquid reductant are brought into contact with a selective catalyst and catalytically converted into environmentally safe nitrogen and water. When a liquid reductant is used, the liquid reductant is typically injected directly into the exhaust pipe in front of a catalyst to effect reduction of NO_x on the surface of the catalyst or in the catalyst itself.

However, one major disadvantage of liquid reductants is that freezing of the reductant may occur. The freezing temperature varies relative to the composition and concentration of the dissolved reductant. For example, solutions having a urea content of about 32.5% in water (eutectic), typically freeze at about 12° F., (−11° C.). As can be readily expected, liquid reductant freezing is particularly a problem for the use of diesel vehicles in cold-weather climates when a liquid reductant is employed to help meet emission standards for NO_x.

Therefore, a thermal heating system is required to melt the solidified urea solution to enable an on-board-vehicle pump to draw the liquid urea solution from its container and to deliver it into the exhaust pipe for the SCR.

In accordance with a first aspect of the present invention, there is provided apparatus for storing a liquid NO_x reductant on a vehicle, the apparatus comprising a container for containing the liquid NO_x reductant, a first heating device located in the container and adapted to heat the NO_x reductant in use, and a tube having a first end adapt to be submerged in liquid NO_x reductant in the container in use, and the tube being adapted to extract liquid NO_x reductant from the container, the tube including a second heating device extending along at least a portion of the length of the tube that is located within the container. The container may be a NO_x reductant tank used to store the NO_x reductant (e.g. urea) for use in a catalytic emission reduction system on a vehicle.

In accordance with a second aspect of the invention, there is provided an NO_x reductant storage apparatus for a vehicle, the apparatus comprising: a container for containing the NO_x reductant; a first heating device located in the container; a tube assembly adapted to extract liquid NO_x reductant from the container, the tube assembly comprising a flexible tube and a second heating device extending along at least a portion of the length of the tube; and a plate member mechanically coupled to the first heating device and the tube assembly and adapted to locate the first heating device within the container at a predetermined position relative to the tube assembly.

Beneficially, at least a section of the portion of the length of the tube along which the second heating device extends and any length of tube between the section and the first end are adapted to be submerged in NO_x reductant in the container, in use.

Typically, the portion of the length of the tube along which the second heating device extends is at least substantially the length of the tube that is located within the container.

In one example of the invention, the second heating device comprises a helical resistive wire heating device encircling the tube. In another example of the invention, the second heating device comprises a ribbon heater, which may be, for example, made from carbon fibre materials. Alternatively, the second heater may be a flexible resistive heater, for example, made of carbon or silicon rubber materials.

In a further example of the invention, the second heater may comprise a thick film heater circuit, which may be printed on the outside surface of the tube.

In one example of the invention, the tube may be a flexible tube and in this case, the second heating device may be integrally formed within the material of the tube. A flexible tube can be advantageous it that it allows for ease of manufacture and assembly of the apparatus.

In another example of the invention, the tube may be a substantially rigid tube, for example, a metal tube, such as stainless steel and the second heating device is in contact with the external surface of the tube so that heat from the heating device is conducted through the side wall of the tube to the interior of the tube.

Typically, the portion of the tube along which the second heating device extends, may be enclosed in an outer tube, which, for example, may be a metal tube, such as a stainless steel tube. Typically, the outer tube is plugged at both ends and for example, could be filled with a filler material, such as a resin or elastomeric material that is preferably compatible with the NO_x reductant.

Suitably, where an outer tube surrounds the second heating device and the portion of the tube along which the second heating device extends, a temperature sensor and/or a liquid level sensor may be housed within an annular gap between the tube and the outer tube to sense the temperature and the level of the NO_x reductant within the container, in use.

Generally, the liquid NO_x reductant is a urea solution, typically having a urea content of between 25% and 40% and suitably, between 30% and 35% and most preferably, substantially 32.5%.

In one example of the invention, the tube extends through a sidewall of the container so that a second end of the tube is outside the container. For example, it is possible that the tube could extend to a dispensing device, such as an injector, for dispensing the NO_x reductant into the exhaust flow. However, alternatively, the second end of the tube could terminate inside the container at a connector mounted on a sidewall of the container. The term “sidewall” in this context means any wall of the container, including the top, bottom or sides of the container.

Advantageously, the container includes a removable closure and the first and second heating devices are electrically coupled and the tube is fluidly coupled to further apparatus outside the container through the removable closure when the container is closed by the closure. Conveniently, the closure is adapted to removably mount to the top of the container.

Typically, the first heating device and the first end of the tube are mechanically coupled to a plate member that is located adjacent the bottom of the container when the container is closed by the closure. In this way the location of the first end of the tube can be fixed at a position relative to the plate member and to the first heating device. This allows a beneficial predetermined separation of the first end of the tube and the heater to optimise the performance of the apparatus and maximise the usable urea. This arrangement is convenient for allowing the withdrawal of liquid NO_x reductant rapidly after activation of the first heating device, and is particularly beneficial when a flexible pickup tube is used as the first end of the tube will remain in the optimal predetermined location relative to the first heating device, even when the apparatus is moving or not positioned in its intended orientation.

The mechanical coupling between the first heating device and the plate member also acts as thermal coupling between the respective components so that the base plate provides additional surface area for more rapidly heating the NO_x reductant.

The first heating device may be a resistive heating element, typically located at or adjacent to the bottom of the container. For example, the resistive heating element may be in the form of a helical coil.

Alternatively, the first heating device may comprise a positive temperature coefficient (PTC) heater element. Typically, where the first heating device comprises a PTC heater element, the PTC heater element is located at or adjacent to the bottom of the container. Typically, a number of PTC heater elements form the first heating device. For example, the first heating device may include three PTC heater elements. However, any number of PTC heater elements may be used. The number of PTC elements that are used may depend, for example, on the shape and configuration of the container, the type of NO_x reductant used and the maximum volume of NOx reductant that can be held in the container. Suitably, the PTC heater elements are encased in a NO_x reductant compatible material. For example, the PTC heater elements could be encapsulated in a suitable material that is resistant to the NO_x reductant. The encapsulation could be performed by a moulding technique, such as injection moulding.

In a particularly suitable embodiment the first heating device is a resistive element coiled heater that is mechanically (and thermally) coupled to a plate member. A pickup tube is further connected to the plate member. Conveniently the pickup tube is a flexible tube containing a second heating device.

Where the tube is a flexible tube, the tube may comprise a multilayer tube and for example, may include at least a sealing layer and a thermoplastic elastomeric layer and the second heating device is integrally formed in at least one of the layers. The tube may also preferably include an insulating layer.

Typically, the second heating device is located in or close to the innermost layers of the tube so that it is relatively close to the internal surface of the tube. Alternatively or in addition, the second heating device may be located in or close to the outermost layers of the tube. Beneficially, the second heating device extends between the innermost and the outermost layers of the tube. This has the advantage that the second heating device can be used to both heat the interior of the tube and the exterior of the tube. Heating the exterior of the tube as well as the interior of the tube has the advantage of helping to create a liquid flow path along the outside surface of the tube when the NO_x reductant is frozen in the container, in use.

Advantageously, the first and second heating devices can be controlled independently of each other, as desired.

The invention also encompasses apparatus for extracting liquid NO_x reductant from a container on a vehicle. Thus, is another aspect the invention provides apparatus for extracting a liquid NO_x reductant from a container on a vehicle, the apparatus comprising a tube having a first end for submersion in a liquid NO_x reductant and a heating device extending along at least a portion of the length of the tube.

It will be appreciated that while features of the invention may be described in relation to particular aspects, embodiments or examples, these features may be applicable to any other aspect, embodiment or example.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of apparatus for storing an NO_x reductant in accordance with the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1A is a perspective view of a first example of apparatus for storing a urea solution on a vehicle and including three PTC heater elements and a heated flexible pickup tube;

FIG. 1B is a perspective view from below of a cover for the apparatus shown in FIG. 1A

FIG. 2 is a perspective view of a second example of apparatus for storing a urea solution on a vehicle and including a resistive heater element and a heated flexible pickup tube;

FIG. 3 is an enlarged view of a bottom of the apparatus shown in FIG. 2;

FIG. 4 is a cross-sectional view of the heated flexible pickup tube shown in FIGS. 1A, 1B, 2 and 3;

FIGS. 5A and 5B are cross sectional views of a first example of a heated rigid pickup tube;

FIGS. 6A and 6B are cross sectional views of a second example of a heated rigid pickup tube; and

FIGS. 7A and 7B are cross sectional views of a third example of a heated rigid pickup tube.

BEST MODE FOR CARRYING OUT THE INVENTION

All references cited herein are incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

FIGS. 1A and 1B show a urea solution storage system for light duty vehicles that is mounted in an appropriate location on the vehicle. The storage system consists of a container (or tank) 1, a cover 2, a combined liquid level and temperature sensor 3, a pickup tube 5 with a filter (not shown) at its lower end and a heater 4. The heater 4 consists of three positive temperature coefficient (PTC) heating elements 61 that are located near the bottom 6 of the container 1. The PTC heating elements 61 are encased in a urea resistant protective shell and are mechanically mounted on a base plate 8 and electrically coupled by wires 62 to a connector 7 on the other side of the cover 2. Generally, the base plate 8 also supports lower end of the pickup tube 5. The base plate 8 is mounted inside the container 1 near the base 6 of the container 1. This helps to prevent movement of the heater elements 61 and the pickup tube 5 within the container 1 during movement of the vehicle and also spaces the heater and the lower end of the pickup tube 5 from the bottom 6 so that liquid urea solution can easily enter the lower end of the pickup tube 5 and to permit a pool of liquid urea solution to form under the pickup tube 5 and the heater 4 during melting of frozen urea solution within the container 1.

FIGS. 2 and 3 show a urea solution storage system similar to that shown in FIGS. 1A and 1B, except that the PTC heating elements 61 of the heater 4 are replaced with a coiled resistive heating element 65 mechanically mounted on the base plate 8 and which is electrically coupled to a connector 66 on the cover 2 by means of a heater shaft 67. In this example, the resistive heating element is in the form of a resistive heating wire mounted inside a coiled metal tube to form the coiled resistive heating element 65. However, any suitable type of resistive heating element could be used. Also, in the example shown in FIGS. 2 and 3, the heater shaft 67 is not heated. This helps to avoid the problem of the urea solution being overheated by the heater shaft.

FIG. 3 shows a filter connector 60 that is connected to a connector 16 on the lower end of the pick-up tube 5. The filter connector 60 attaches to a filter (not shown) located below the base plate 8.

FIG. 4 is a cross sectional view of the pickup tube 5 shown in FIGS. 1 and 2. The pickup tube 5 comprises a flexible hose 10. Typically, the flexible hose is a multilayered hose that includes at least a thermoplastic elastomeric layer, a heating element, a sealing layer and insulating layer. Typically, the sealing layer is the inner most layer and the next inner layer is the thermoplastic elastomeric layer and the heating element is preferably incorporated into the thermoplastic elastomeric layer. The outer layer is typically the insulating layer. As shown in FIG. 4, the heating element 11 is a resistive wire heater that is helically formed along the length of the flexible hose 10 and is an integral part of the hose 10. However, other heating devices could be used, such as a ribbon heater made of carbon fibre materials or an etched resistive pattern ribbon heater. At end 12 of the pickup tube 5 is an end connector 13 that connects the pickup tube 5 to a tubing connector 14 in the cover 2. At the opposite end 15 of the pickup tube 5 is another connector 16 which permits the pickup tube 5 to be coupled to the filter 60. As shown in FIG. 1B, the electrical connections for the heating element 11 are provided by wires 17 that extend from the sidewall of the pickup tube 5 through a sealed opening 18 in the cover to terminate in a connector 19. However, an alternative option would be to have the wires 17 extend from the sidewall of the pickup tube 5 on the other side of the cover 2. This would have the advantage of not requiring the opening 18 in the cover 2.

FIGS. 5A to 7B show three further examples of the pickup tube 5 in which the pickup tube 5 comprises a rigid stainless steel tube 20 through which the urea solution is extended from the container 1.

FIGS. 5A and 5B show a first example of a rigid pickup tube 35 using the rigid stainless steel tube 20. In this example a flexible heater 21 is in intimate contact with the outside surface of the stainless steel tube 20 and partially encircles the stainless steel tube 20. An outer protective stainless steel tube 22 encloses the flexible heater 21 and the length of the stainless steel tube 20 along which the flexible heater 21 extends. At both the upper end 23 and the lower end 24 of the outer stainless steel tube 22 is an elastomeric end plug 25, 26 respectively. The rubber end plugs 25, 26 are compatible with the NO_x reductant and seal the ends of the annular gap between the outer stainless steel tube 22 and the inner stainless steel tube 20 to prevent the ingress of urea solution into the annular gap between the tubes 20, 22 and so isolate the flexible heater 21 from the urea solution.

The upper plug 25 also provides a connection to permit the plug 25 to be inserted into a boss 50 in the cover 2 and the lower plug 26 provides for connection of the pickup tube 35 to a filter (not shown).

As shown in FIG. 5B, the outer stainless steel tubing 22 can also house a printed circuit board (PCB 27) in the annular gap. The PCB 27 includes a temperature sensor and a liquid level sensor to enable monitoring of the temperature of the urea solution in the container 1 and the level of the urea solution in the container 1. The wiring for the sensors and the heater 21 are also contained within the annular gap between the inner and outer tubes 20, 22 but are not shown in FIGS. 5A and 5B.

FIGS. 6A and 6B show a second example of a rigid pickup tube 45 incorporating an inner stainless steel tube 20. In this example, a thick film heater 46 is printed onto the outside surface of the stainless steel tube 20. As in the first example described above and shown in FIGS. 5A and 5B, the inner stainless steel tube 20 and printed heater 46 are enclosed in an outer protective stainless steel tube 22 that has plugs 25, 26 at its upper 23 and lower ends 23, 24 to seal the annular gap between the inner tube 20 and the outer tube 22 to prevent the ingress of urea solution into the annular gap between the tubes 20, 22.

As in the first example of the pickup tube 35 described above and shown in FIGS. 5A and 5B, the annular gap between the inner tube 20 and the outer tube 22 in the second example shown in FIGS. 6A and 6B can also accommodate a PCB 27. The PCB 27 can include a temperature sensor and a liquid level sensor to permit the temperature of the urea solution in the container 1 to be monitored and the level of the urea solution in the container 1 to be monitored.

FIGS. 7A and 7B show a third example of a rigid pickup tube 55 incorporating an inner stainless steel tube 20. In this example, the heating element is provided by an electrically insulated resistive wire wound heater 40 that is wound helically around the inner tube 20 along the length of the inner tube 20, as shown in FIG. 7A. As with the first and second examples shown in FIGS. 5A to 6B, an outer protective stainless steel tube 22 is located around the resistive wire heater element 40 and the inner tube 20 and plugs 25, 26 are provided at the upper and lower ends 23, 24 of the outer tube 22, respectively. As in the first and second examples of the pickup tubes 35, 45, the pickup tube 55 is mounted on a boss 50 of the cover 2 by means of the upper plug 25 and the lower plug 26 provides a connection to a filter (not shown). The plugs 25, 26 also seal the annular gap between the outer tube 22 and the inner tube 20 to prevent the ingress of urea solution into the annular gap between the tubes 20, 22.

Furthermore, a PCB 27 with a temperature sensor and liquid level sensor may also be mounted in the outer protective tube 22, in a similar manner to that described above for the pickup tubes 35, 45.

In use, the apparatus is mounted on a diesel fuel powered vehicle and contains a urea solution for injection into the exhaust of the vehicle upstream of a catalyst so that the urea solution mixes with the exhaust gases and on contact with the catalyst reduces any NO_x in the gases to nitrogen and water.

If the vehicle is in a cold climate and the urea solution has frozen in the container 1, the temperature sensor 3 detects that the urea solution may be frozen and switches on the heater 4 to start to melt the urea solution in the container 1.

A certain amount of urea solution around the pickup tube 5 also needs to melted to so that it creates a fluid path from the top of the container 1 to below the base plate 8 where the urea pickup occurs through the filter 60 attached to the lower end of the pickup tube 5. This path creates a fluid communication channel to prevent vacuum locking beneath the frozen urea solution as melted urea solution is extracted from the container 1. Therefore, the heating device 11, 21, 46, 40 in the pickup tube 5 is also used to melt frozen urea solution surrounding the tube 5 to create this communication path around the outside of the pickup tube 5, as well as heating the interior of the tube 5 to reduce the risk of melted urea solution within the pickup tube 5 refreezing in the pickup tube 5.

An advantage of the invention is that it enables independent heating control of the pickup tubes 5, 35, 45, 55 and the urea liquid within the container 1 which is heated by the separately controlled heater 4. This enables optimum heating of both the pickup tube 5 and the mass of urea solution within the container 1.

In addition, the use of a heated pickup tube 5, 35, 45, 55 mitigates the risk of the urea solution freezing at the cover interconnection 14.

Another advantage of the invention is its ease of manufacture and assembly. For example, it does not require a separate thawing container (including one or more heating elements) within the NO_x reductant container/tank in order to operate efficiently and rapidly.

Although particular embodiments of the invention have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims, which follow. It is proposed by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. Apparatus for storing a liquid NOx reductant on a vehicle, the apparatus comprising: a container for containing the liquid NOx reductant;a first heating device located in the container and adapted to heat the NOx reductant in use;a tube assembly having a first end adapted to be submerged in liquid NOx reductant in the container in use, and being adapted to extract liquid NOx reductant from the container, the tube assembly comprising a tube and a second heating device extending along at least a portion of the length of the tube that is located within the container; anda plate member mechanically coupled to the first heating device and the first end of the tube assembly.

2. Apparatus according to claim 1, wherein the container includes a removable closure and the first and second heating devices are electrically coupled to electrical apparatus outside the container through the removable closure and the tube assembly is fluidly coupled to further apparatus outside the container through the removable closure when the container is closed by the closure.

3. Apparatus according to claim 2, wherein the first heating device and the first end of the tube assembly are mechanically coupled to a plate member that is adapted to be located adjacent the bottom of the container when the container is closed by the closure.

4. Apparatus according to claim 1, wherein the second heating device comprises a helical resistive wire heating device encircling the tube.

5. Apparatus according to claim 1, wherein the second heating device comprises a ribbon heater.

6. Apparatus according to claim 1, wherein the second heating device comprises a flexible resistive heater.

7. Apparatus according to claim 1, wherein the second heating device comprises a film heater circuit.

8. Apparatus according to claim 7, wherein the film heater circuit is printed on the outside surface of the tube.

9. Apparatus according to claim 1, wherein the tube comprises a flexible tube.

10. Apparatus according to claim 9, wherein the second heating device is embedded within the walls of the flexible tube

11. Apparatus according to claim 1, wherein the tube comprises a first substantially rigid tube.

12. Apparatus according to claim 11, wherein the first substantially rigid tube comprises a metal tube and the second heating device is in contact with the external surface of the first substantially rigid tube, so that heat from the second heating device is conducted through the sidewall of the first substantially rigid tube.

13. Apparatus according to claim 1, wherein the tube assembly comprises an outer sheath, and wherein the portion of the tube along which the second heating device (11; 21; 46; 40) extends is enclosed in the outer sheath.

14. Apparatus according to claim 13, wherein the tube and the outer sheath define a space between the outer surface of the tube and the inner surface of the outer sheath, and the space is plugged at both ends to isolate the second heating device from NOx reductant in the container, in use.

15. Apparatus according to claim 1, wherein the tube assembly further comprises a temperature sensor and/or a liquid level sensor.

16. Apparatus according to claim 1, wherein the tube has an internal wall defining a channel for extracting liquid NOx reductant from the container and an external wall, and the second heating device is adapted to heat both the internal wall and the external wall of the tube.

17. Apparatus according to claim 1, wherein the first and second heating devices are independently operable.

18. An NOx reductant storage apparatus for a vehicle, the apparatus comprising: a container for containing the NOx reductant;a first heating device located in the container;a tube assembly adapted to extract liquid NOx reductant from the container, the tube assembly comprising a flexible tube and a second heating device extending along at least a portion of the length of the tube; anda plate member mechanically coupled to the first heating device and the tube assembly and adapted to locate the first heating device within the container at a predetermined position relative to the tube assembly.

19. The NOx reductant storage apparatus of claim 18, wherein the first heating device is a resistive element coiled heater which is thermally coupled to the plate member.

20. The NOx reductant storage apparatus of claim 18, wherein the first and second heating devices are independently operable.