Abstract:
An injector which incorporates the use of an insert to compensate for the change in volume of diesel exhaust fluid as the diesel exhaust fluid freezes, reducing or eliminating the effects on the calibration of the injector. The calibration freeze protection insert is located adjacent a calibration sleeve in the injector, where the insert is welded to an inlet tube. Any axial forces applied to the calibration sleeve from the blocking force of the freezing diesel exhaust fluid are transmitted to the insert, and the position of the insert is maintained by the welds. The insert and the calibration sleeve are configured to only allow small amounts of diesel exhaust fluid to migrate around the injector components, which is able to be compensated for by the elastic modulus of the various injector components.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to an insert used as part of an injector for a selective catalytic reduction system, where the insert prevents a change in the operation of the injector due to the freezing of diesel exhaust fluid. 
       BACKGROUND OF THE INVENTION 
       [0002]    New emissions legislation in Europe and North America is driving the implementation of new exhaust aftertreatment systems, particularly for lean-burn technologies such as compression-ignition (diesel) engines, and stratified-charge spark-ignited engines (usually with direct injection) that are operating under lean and ultra-lean conditions. Lean-burn engines exhibit high levels of nitrogen oxide emissions (NOx), that are difficult to treat in oxygen-rich exhaust environments characteristic of lean-burn combustion. Exhaust aftertreatment technologies are currently being developed that treat NOx under these conditions. 
         [0003]    One of these technologies includes a catalyst that facilitates the reactions of ammonia (NH 3 ) with the exhaust nitrogen oxides (NOx) to produce nitrogen (N 2 ) and water (H 2 O). This technology is referred to as Selective Catalytic Reduction (SCR). Ammonia is difficult to handle in its pure form in the automotive environment, therefore it is customary with these systems to use a liquid aqueous urea solution, typically at a 32% concentration of urea (CO(NH 2 ) 2 ). The solution is referred to as AUS-32, or diesel exhaust fluid (DEF), and is also known under its commercial name of AdBlue. The DEF is delivered to the hot exhaust stream and is transformed into ammonia in the exhaust after undergoing thermolysis, or thermal decomposition, into ammonia and isocyanic acid (HNCO). The isocyanic acid then undergoes a hydrolysis with the water present in the exhaust and is transformed into ammonia and carbon dioxide (CO 2 ), the ammonia resulting from the thermolysis and the hydrolysis then undergoes a catalyzed reaction with the nitrogen oxides as described previously. 
         [0004]    The delivery of the DEF solution to the exhaust involves precise metering of the DEF and proper preparation of the DEF to facilitate the later mixing of the ammonia in the exhaust stream. The delivery of the DEF into the exhaust is typically achieved using some type of injector. 
         [0005]    The injector is calibrated during manufacturing to function correctly during the life of the vehicle such that a consistent amount of DEF is injected into the exhaust stream each time the injector is actuated. One approach to achieving the proper calibration is to use a calibration sleeve which is mounted in a specific position to properly position a return spring (which is part of a solenoid unit used for actuating the injector). However, when the vehicle is exposed to different environments and operating conditions, the DEF may freeze, and therefore expand. Injectors are typically expected to operate at temperatures between −40° C. to 160° C. DEF freezes at −11° C., which may occur in cold environments when the vehicle is not in use, and the volume of DEF increases by approximately 9% when frozen. Since the DEF in its liquid form is able to migrate around different parts of the injector, the expansion of the DEF during freezing may cause different components of the injector to shift and deform, or displace permanently, compromising the operation of the injector, and affecting performance. Some injectors incorporate the use of external devices to compensate for this expansion, which add cost and number of components. 
         [0006]    Accordingly, there exists a need for an injector which is able to compensate for the increase in volume of frozen diesel exhaust fluid during certain conditions, and still function correctly once the frozen diesel exhaust fluid has returned to liquid form. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is an injector which incorporates the use of an insert to compensate for the change in volume of diesel exhaust fluid as the diesel exhaust fluid freezes, reducing or eliminating the effects on the calibration of the injector. 
         [0008]    In one embodiment, the present invention is a calibration freeze protection insert which is located adjacent a calibration sleeve in an injector, where the insert is welded to an inlet tube. Any axial forces applied to the calibration sleeve from the blocking force of the freezing diesel exhaust fluid are transmitted to the insert, and the position of the insert is maintained by the welds. The insert and the calibration sleeve are configured to only allow small amounts of diesel exhaust fluid to migrate around the injector components, which is able to be compensated for by the elastic modulus of the various injector components. 
         [0009]    In one embodiment, the present invention is an injector having an insert to prevent damage or a change in operation of the injector, due to the freezing of diesel exhaust fluid, where the injector includes an inlet tube configured for receiving diesel exhaust fluid, a pole piece disposed in the inlet tube, a calibration sleeve partially disposed in the pole piece, and an insert disposed in the inlet tube, such that the insert in contact with the calibration sleeve. Under conditions where the diesel exhaust fluid freezes, the diesel exhaust fluid is directed from the calibration sleeve through the insert. The calibration sleeve is connected to the pole piece through a press-fit connection. 
         [0010]    The injector also includes a lower aperture formed as part of the calibration sleeve, and a central aperture formed as part of the insert. The diesel exhaust fluid in the lower aperture migrates through the central aperture as the diesel exhaust fluid freezes. In one embodiment, the lower aperture is approximately the same diameter as the central aperture, but it is within the scope of the invention that the lower diameter may be larger or smaller than the central aperture. 
         [0011]    A filter assembly is disposed in the insert, and a retention cavity is formed as part of the insert such that a portion of the filter assembly is disposed in the retention cavity when the filter assembly is disposed in the insert. 
         [0012]    The injector also includes a retention feature formed as part of the insert, and a ledge portion is formed as part of the insert such that the ledge portion is part of the retention cavity. A body portion is part of the filter assembly, and the body portion is located between the retention feature and the ledge portion when the filter assembly is placed in the insert. 
         [0013]    A central cavity is formed as part of the insert, such that the central cavity is adjacent the retention cavity. The filter assembly also includes a filter portion, and the filter portion partially extends into the central cavity when the filter assembly is disposed in the insert. 
         [0014]    At least one weld connection provides a connection between the insert and the inlet tube. The weld connections secure the position of the insert relative to the inlet tube, therefore preventing the calibration sleeve from moving, maintaining the proper calibration of the injector. 
         [0015]    In an embodiment, an upper surface is formed as part of the calibration sleeve, a contact surface is formed as part of the insert, and the upper surface is in contact with the contact surface when the calibration sleeve and the insert are disposed in the inlet tube. The contact between the calibration sleeve and the insert may be such that the lower aperture and central aperture are in alignment with one another. 
         [0016]    The insert may also include a receiving cavity located in proximity to the central aperture such that a portion of the calibration sleeve extends into the receiving cavity when the insert and the calibration sleeve are disposed in the inlet tube, such that the calibration sleeve contacts the insert, and the lower aperture is in substantial alignment with the central aperture. 
         [0017]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0019]      FIG. 1  is a perspective view of an injector having an insert, according to embodiments of the present invention; 
           [0020]      FIG. 2  is an exploded view of an injector having an insert, according to embodiments of the present invention; 
           [0021]      FIG. 3  is a sectional view of an injector having an insert, according to embodiments of the present invention; 
           [0022]      FIG. 4  is a sectional exploded view of an insert and a filter assembly used as part of an injector, according to embodiments of the present invention; and 
           [0023]      FIG. 5  is a sectional view of a filter assembly connected to an insert used as part of an injector, according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0025]    An injector having a calibration protection insert is shown in  FIGS. 1-5 /generally at  10 . Referring to the Figures generally, the injector  10  includes an actuator, shown generally at  12 , which in this embodiment is a solenoid  12 , where the solenoid  12  has a pole piece  14  surrounded by a bobbin  16 , and the bobbin  16  is surrounded by a coil  18 . The pole piece  14  is welded to an inlet tube  20  as shown by the welds  14   a , 14   b , and the inlet tube  20  is at least partially surrounded by a housing  22 . A portion of the inlet tube  20  protrudes out of the housing  22 , such that a first O-ring  24  surrounds the inlet tube  20  as shown in  FIGS. 1-3 . The housing  22  also includes a groove  26 , and a second O-ring  28  is disposed in the groove  26 . 
         [0026]    The pole piece  14  includes an aperture  30 , and during assembly, a calibration sleeve  32  is placed in the aperture  30  to apply force to a return spring  34 , as part of the calibration process of the injector  10 . The calibration sleeve  32  is positioned in the aperture  30  such that the return spring  34  is compressed a desired amount, which may vary from one injector  10  to the next, due to variations in the spring constant of the return spring  34 . The position of the calibration sleeve  32  is maintained by a press-fit connection inside the pole piece  14 . 
         [0027]    The injector  10  also includes an insert  36 , which is located in the inlet tube  20  in proximity to the calibration sleeve  32 . The insert  36  includes a receiving portion  38  having a receiving cavity, shown generally at  40 . The receiving portion  38  is generally circular in shape, and has a larger diameter as compared to the diameter of the calibration sleeve  32 . The insert  36  also includes a contact surface  42  which forms part of the cavity  40 , and a central aperture  44  which is in fluid communication with the cavity  40 . The diameter of the aperture  44  is narrower than the diameter of the cavity  40 . In fluid communication with the aperture  44  is a central cavity, shown generally at  46 . The cavity  46  includes a tapered portion  46   a  and a non-tapered portion  46   b . The tapered portion  46   a  includes a small diameter portion  48   a , which is approximately the same diameter as the aperture  44 , and a large diameter portion  48   b , which has approximately the same diameter as the non-tapered portion  46   b  of the cavity  46 . 
         [0028]    The insert  36  also includes a retention cavity, shown generally at  50 . The retention cavity  50  is larger in diameter than the non-tapered portion  46   b  of the cavity  46 . Formed as part of the retention cavity  50  is a ledge portion  52 , and a retention feature  54 . The retention feature  54  is a deformation, or crimped, portion of the side wall  54   a  of the insert  36 . 
         [0029]    The injector  10  also includes a filter assembly, shown generally at  56 , which includes a body portion  58  and a filter portion  60 . The body portion  58  also includes a lower mounting surface  62  and an upper mounting surface  64 . The filter portion  60  is tapered, and when the filter assembly  56  is connected to the insert  36 , part of the filter portion  60  is disposed in the cavity  46 , as shown in  FIGS. 3 and 5 . During assembly, the filter assembly  56  is inserted into the retention cavity  50  in the direction of the arrow  66  shown in  FIG. 4 , such that the filter assembly  56  is moved towards the cavity  46 . The retention feature  54  includes an innermost edge  54   b , a lowermost edge  54   c , and a retention surface  54   d . The diameter of the innermost edge  54   b  of the retention feature  54  is smaller than the diameter of the body portion  58 . Therefore, as the filter assembly  56  is inserted into the retention cavity  50 , the body portion  58  causes the retention feature  54  to deflect. The filter assembly  56  is moved in the direction of the arrow  66  until the lower mounting surface  62  contacts the ledge portion  52 , and the upper mounting surface  64  has moved past the retention feature  54  such that the retention feature  54  is no longer deflected by the body portion  58  and moves back to the position shown in  FIGS. 3 and 5 , and the retention surface  54   d  is in contact with the upper mounting surface  64 . The angle of the retention feature  54  and the distance  68  between the lowermost edge  54   c  and the ledge portion  62  is such that there is an interference fit, or “snap fit” connection between the retention feature  54  and the upper mounting surface  64 , where the filter assembly  56  is retained in place and prevented from moving. 
         [0030]    The insert  36  is connected to the inlet tube  20  through the use of some type of connection, which in this embodiment is a weld connection  70 . However, it is within the scope of the invention that other types of connections may be used. The weld connection  70  is located in proximity to the inlet of the inlet tube  20 , and in proximity to the retention feature  54 . It is also within the scope of the invention that the weld connection  70  may be located along different areas of the inlet tube  20  and the insert  36 , depending on what is best suited for a particular application and construction. Furthermore, the steps taken to assemble the filter assembly  56 , the insert  36 , and the inlet tube  20  may vary as well. In one embodiment, the insert  36  is placed in the inlet tube  20 , and secured with the weld connections  70  prior to the filter assembly  56  being placed and secured into the insert  36 . In another embodiment, the filter assembly  56  is placed in the insert  36  prior to the insert  36  being placed into the inlet tube  20 . In either embodiment, the calibration sleeve  32  is placed in the pole piece  14  prior to the insert  36  being placed in the inlet tube  20 . 
         [0031]    The calibration sleeve  32  also includes a lower aperture  72 , which is substantially the same diameter as the aperture  44  of the insert  36 . When the insert  36  is placed in the inlet tube  20 , a portion of the calibration sleeve  32  extends into the cavity  40 , such that an upper surface  74  of the calibration sleeve  32  contacts the contact surface  42  of the insert  36 , and the aperture  72  of the calibration sleeve  32  is in substantial alignment with the aperture  44  of the insert  36 . During operation, DEF flows into the inlet tube  20 , through the filter portion  60  into the retention cavity  50 , through the aperture  44  of the insert  36 , and through the aperture  72  of the calibration sleeve  32 . After the DEF has passed through the aperture  72  of the calibration sleeve  32 , the DEF then flows towards a valve portion (not shown), where as the injector  10  is actuated, the DEF is injected into an exhaust conduit. 
         [0032]    There are conditions where the vehicle is turned off, and the environment is such the DEF may freeze. Since the injector  10  is designed for use in environments having temperatures ranging from −40° C. to 160° C., and DEF freezes at −11° C., it is possible that there may be conditions where the DEF freezes when the vehicle is not in use. As the DEF freezes, the DEF expands, which increases the volume the DEF occupies in the injector  10 . As the DEF expands, the DEF in the pole piece  14  migrates though the aperture  72  of the calibration sleeve  32 , and through the aperture  44  of the insert  36 . This allows for most of the DEF in the injector  10  to expand during freezing without applying any pressure to the components of the injector  10 . In some instances, some of the DEF may migrate between the contact surface  42  and the upper surface  74  of the pole piece, and migrate into other areas of the injector  10 . However, the amounts of DEF that migrate into other parts of the injector  10  is minimal such that if the DEF expands during freezing, the elastic modulus of the materials of the components of the injector  10 , such as the inlet tube  10 , the pole piece  14 , and the housing  12 , are able to compensate for the expansion of the minimal amount of DEF, without damaging or affecting the operation of the injector  10  once the DEF melts back to a liquid. Furthermore, the weld connections  70  secure the position of the insert  36  relative to the inlet tube  20 , therefore preventing the calibration sleeve  32  from moving, maintaining the proper calibration of the injector  10 . 
         [0033]    Another advantage of the present invention is that the insert  36  occupies additional space inside the inlet tube  20 , which would otherwise be occupied by DEF if the insert  36  were not used. Less overall DEF in the injector  10  reduces the amount of overall volume expansion of the DEF during freezing, reducing the force applied to the different components of the injector  10  due to DEF expansion during freezing. 
         [0034]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.