Abstract:
A urea solution pump unit includes a bracket mounted to a lower side of a urea solution tank. A pump unit is horizontally disposed at a center of an upper part of the bracket and includes a pump suctioning a urea solution to one direction and a motor pumping the urea solution to another direction through a gap between a rotor and a stator of the motor inside the pump and discharging the urea solution to a lower side of the bracket. A pair of thawing units are fixedly disposed at both sides of the pump unit on the bracket. The thawing units transfer heat to the urea solution and prevent the urea solution from being frozen. A sensor unit is disposed at one side of one of the thawing units and detects a level, a temperature, and a pressure of the urea solution.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of priority to Korean Patent Application No. 10-2015-0032757 filed in the Korean Intellectual Property Office on Mar. 9, 2015, the entire content of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to a urea solution pump unit which is disposed at a lower part of a urea solution tank, and sucks a urea solution and pumps the urea solution to outside to decrease harmful substances included in exhaust gas of an engine. 
       BACKGROUND 
       [0003]    An environmentally-friendly vehicle has been developed globally, and vehicle emission standards for each country are being gradually reinforced. Further, vehicle makers have developed an environmentally-friendly diesel vehicle due to the regulation of carbon dioxide. 
         [0004]    The exhaust gas emission of the diesel vehicle includes nitrogen oxides and particulate matter, and among them, a nitrogen oxide decreasing technique focuses to a lean NOx trap (LNT) and urea-selective catalytic reduction (urea-SCR). Particularly, the urea-SCR is useful to decrease nitrogen oxides discharged from a diesel engine of a large vehicle. 
         [0005]    The urea-SCR is a selective reduction system which injects a harmless urea solution to an exhaust system, converts the injected urea solution into ammonia through pyrolysis, and causes the converted ammonia to react with a nitrogen oxide to convert the converted ammonia into a harmless component, such as water and nitrogen, and requires a storage system separately storing the urea solution. 
         [0006]    The urea solution storage system includes a urea solution tank, a pump, an inlet, a pipe, a wire, and various kinds of sensors, and particularly, the pump requires a structure stably pumping a strong alkaline urea solution and a decrease in a vertical length of the urea solution tank. 
         [0007]    A research to decrease a problem by improving a sealing structure of a power supply system, improving durability by preventing a rotor and a stator from being corroded due to a urea solution, effectively preventing a urea solution from being frozen, improving mounting stability of the sensors, and preventing impact according to a pressure increase when pumping a urea solution has been conducted. 
         [0008]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY 
       [0009]    The present disclosure has been made in an effort to provide a urea solution pump unit which is capable of generally improving operation stability, durability, and a sealing property of the pump unit by improving a sealing structure, preventing a stator and a rotor from being corroded, and effectively preventing a urea solution from being frozen. 
         [0010]    An exemplary embodiment of the present inventive concept, a urea solution pump unit includes a bracket mounted to a lower side of a urea solution tank. A pump unit is horizontally disposed at a center of an upper part of the bracket and includes a pump suctioning a urea solution to one direction and a motor pumping a urea solution to another direction through a gap between a rotor and a stator of a motor inside the pump and discharging the urea solution to a lower side of the bracket. A pair of thawing units are fixedly disposed at both sides of the pump unit on the bracket. The pair of thawing units transfer heat to a urea solution and prevent the urea solution from being frozen. A sensor unit is disposed at one side of one of the thawing units and detects a level, a temperature, and a pressure of the urea solution. 
         [0011]    The stator may include an exterior stator over-molding surrounding an outer peripheral surface of the stator, and an interior stator over-molding surrounding an inner peripheral surface of the stator. 
         [0012]    The rotor may include an exterior rotor over-molding surrounding an outer side of the rotor. 
         [0013]    The motor may include a rotating shaft rotating together with the rotor, in which the urea solution is suctioned through one end of the rotating shaft and is discharged through another end of the rotating shaft. The pump unit may include: an upper cover disposed at the other end of the rotating shaft, having an outlet at a center thereof corresponding to the rotating shaft, and having a three-phase terminal which supplies power to the stator and is disposed at an external side of the outlet; an outlet adaptor integrally extending from the upper cover to an opposite side of the rotor, and fastened to an upper surface of the bracket to transfer the urea solution to a lower side of the bracket; and a relief valve fastened to the outlet adaptor and maintaining the urea solution at a predetermined pressure or lower. 
         [0014]    When the relief valve is connected with the outlet and a pressure equal to or larger than the predetermined pressure is detected, the relief valve may autonomously open and relieve the pressure to an upper side of the bracket. 
         [0015]    The three-phase terminal may extend to a lower side of the outlet adaptor and be connected to the outside through the bracket. 
         [0016]    The urea solution pump unit may further include a first adaptor o-ring disposed around the three-phase terminal, which extends to lower sides of the outlet and the outlet adaptor, to seal the outlet and the outlet adaptor from the urea solution, in which the outlet extends at a lower side of the outlet adaptor. 
         [0017]    A pipe-shaped metal port may be inserted into an internal peripheral surface of the outlet corresponding to the outlet adaptor, and one or more port o-rings that are sealing members may be disposed on an outer peripheral surface of the metal port. 
         [0018]    A discharge pipe discharging a urea solution received from the outlet adaptor may integrally extend at the lower side of the bracket, a pipe-shaped metal port may be inserted in an internal peripheral surface of the outlet, and one or more port o-rings that are sealing members may be disposed on an outer peripheral surface of the metal port. 
         [0019]    An adaptor insertion recess, into which the outlet adaptor is inserted, may be formed on the bracket, and the urea solution pump unit may include a clip that may fix the outlet adaptor to the adaptor insertion recess so that the outlet adaptor is inserted into the adaptor insertion recess. 
         [0020]    The urea solution pump unit may further include a second adaptor o-ring disposed between a lower surface of the outlet adaptor and a bottom surface of the adaptor insertion recess to seal the urea solution. 
         [0021]    Hooks may be integrally formed on the bracket, and hook fastening parts fastened to the hooks may be integrally formed at a lower side of each thawing unit. 
         [0022]    The sensor unit may include: a sensor flange extending to the upper side of the bracket; and a sensor cell mounted on the bracket at a lower end of the sensor flange. The sensor cell may be surrounded by a resin material and sealed from the urea solution to be fixed to the bracket, and may be electrically connected to a lower external side of the bracket. 
         [0023]    The thawing unit may include: a positive temperature coefficient (PTC) transistor configured to generate heat by electric energy; a PTC guide having a recess, into which the PTC is mounted; power supply terminals attached to both surfaces of the PTC guide and being in contact with the PTC; an adhesive film attached to an external surface of each power supply terminal; and a thawing over-molding surrounding external sides of the PTC, the PTC guide, and the adhesive film to protect the PTC, the PTC guide, and the adhesive film from the urea solution. 
         [0024]    The relief valve may include a check ball and an elastic member elastically supporting the check ball. 
         [0025]    The urea solution pump unit may further include: a heater connector connecting a power supply to the thawing units; a pressure sensor connector connecting the power supply to the sensor unit; a motor connector connecting the power supply to the motor; a level/temperature sensor connector connecting the power supply to the sensor unit; and a collective connector mounted at the lower side of the bracket and connected to each of the heater connector, the pressure sensor connector, the motor connector, and the level/temperature sensor connector at one side thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a partial perspective view illustrating a urea solution pumping system according to an exemplary embodiment of the present inventive concept 
           [0027]      FIG. 2  is a partial exploded perspective view of a motor of the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
           [0028]      FIG. 3  is a partial perspective view of a discharge unit of the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
           [0029]      FIG. 4  is a partial exploded perspective view of the motor and a pump unit in the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
           [0030]      FIG. 5  is a partial cross-sectional view of the pump unit, the motor, and the discharge unit according to the exemplary embodiment of the present inventive concept. 
           [0031]      FIG. 6  is a partial exploded perspective view of the discharge unit according to the exemplary embodiment of the present inventive concept. 
           [0032]      FIG. 7  is a partial perspective view illustrating a state in which a bracket is fastened to an adaptor part in the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
           [0033]      FIG. 8  is a partial exploded perspective view illustrating a part fastened to the adaptor on the bracket according to the exemplary embodiment of the present inventive concept. 
           [0034]      FIG. 9  is a partial exploded perspective view illustrating a fastening structure of the bracket and a thawing unit according to the exemplary embodiment of the present inventive concept. 
           [0035]      FIG. 10  is a partial cross-sectional view of the bracket according to the exemplary embodiment of the present inventive concept. 
           [0036]      FIG. 11  is a partial exploded perspective view of the thawing unit according to the exemplary embodiment of the present inventive concept. 
           [0037]      FIG. 12  is a partial exploded perspective view of the discharge unit according to the exemplary embodiment of the present inventive concept. 
           [0038]      FIG. 13  is a partial exploded perspective view illustrating a structure of a connector in the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0039]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0040]      FIG. 1  is a partial perspective view illustrating a urea solution pumping system according to an exemplary embodiment of the present inventive concept. 
         [0041]    Referring to  FIG. 1 , a urea solution pumping system  100  includes a bracket  105 , a clip  705 , a discharge pipe  110 , an outlet adaptor  1112 , an upper cover  300 , a sensor flange  125 , a thawing unit  120 , a pump unit  115 , a hook fastening part  905 , and a hook  900 . 
         [0042]    The bracket  105  has a structure mounted at an opened hole formed at a lower part of a urea solution tank, and the pump unit  115  pumping a urea solution is disposed on the bracket  105 . 
         [0043]    The thawing unit  120  thawing the urea solution is disposed at both sides of the pump unit  115 , and is fastened onto the bracket  105  through the hook  900  and the hook fastening part  905 . 
         [0044]    The sensor flange  125  for a level sensor and a pressure sensor may be integrally formed with the bracket  105  at one side of the thawing unit  120 , and the temperature sensor may be disposed in the bracket  105  in correspondence with an inlet side of the pump unit  115  to improve temperature detecting performance. 
         [0045]    The outlet adaptor  1112 , which sucks the urea solution at a rear side of the pump unit  115 , has the upper cover  300  disposed at a front side thereof, and discharges the urea solution to a front side of the upper cover  300 , is integrally formed. 
         [0046]    The outlet adaptor  1112  is fastened to the upper bracket  105  through the clip  705 , and the urea solution pumped by a pump of the pump unit  115  is pumped to a urea solution injector (not illustrated) through the upper cover  300 , the outlet adaptor  1112 , and the discharge pipe  110 . 
         [0047]    The thawing unit  120  prevents the urea solution filled in a urea solution tank from being frozen, and is firmly fixed through a fastening structure of the hook  900  formed on the bracket  105  and the hook fastening part  905  formed at a lower side of the thawing unit  120 . 
         [0048]    Further, the thawing unit  120  is disposed at both sides of the pump unit  115  to make the thawed urea solution be rapidly supplied to a suction side of the pump unit  115 . 
         [0049]      FIG. 2  is a partial exploded perspective view of a motor of the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
         [0050]    Referring to  FIG. 2 , the pump unit  115  includes a motor  554 , and the motor  554  includes a rotating shaft  200 , a rotor  205 , a rotor over-molding  210 , a stator  215 , an interior stator over-molding  220 , an exterior stator over-molding  225 , and terminal holes  230 . 
         [0051]    The rotor over-molding  210  surrounds the rotor  205  to prevent the urea solution from permeating, and the interior stator over-molding  220  and the exterior stator over-molding  225  generally surround the stator  215  to prevent the urea solution from permeating. 
         [0052]    The terminal holes  230 , through which power is supplied, are formed on a front surface of the exterior stator over-molding  225 , and the terminal holes  230  are formed in correspondence with a three-phase terminal  305  of  FIG. 3 . 
         [0053]    The rotor over-molding  210  may be formed of a material in which an engineering plastic is mixed with a glass fiber, and similarly, the exterior stator over-molding  225  and the interior stator over-molding  220  may also be formed of a material in which the engineering plastic is mixed with the glass fiber. 
         [0054]      FIG. 3  is a partial perspective view of a discharge unit of the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
         [0055]    Referring to  FIG. 3 , the upper cover  300  is formed to cover a front surface of the exterior stator over-molding  225 , and has an outlet  315  at a center thereof. 
         [0056]    The three-phase terminal  305 , through which power is supplied, protrudes and is disposed around the outlet  315 , and o-ring grooves  310  are formed based on the outlet  315  at both sides based on the three-phase terminal  305 . 
         [0057]    Here, upper motor o-rings  505  of  FIG. 5  are sealing members and mounted at the o-ring grooves  310  to block the urea solution flowing through the outlet  315  and an external urea solution from flowing into the three-phase terminal  305 . 
         [0058]      FIG. 4  is a partial exploded perspective view of the motor and the pump unit in the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
         [0059]    Referring to  FIG. 4 , the pump unit  115  includes the rotating shaft  200 , the rotor over-molding  210 , the exterior stator over-molding  225 , a lower motor o-ring  400 , a lower motor cover  405 , a pump  410 , a pump cover  415 , a lower pump cover  420 , an inlet  425 , fastening bolts  430 , and a housing  435 . 
         [0060]    The lower motor o-ring  400  is formed in a sealing structure between the stator outside molding  225  and the lower motor cover  405 , and the pump  410  sucks an external urea solution through the inlet  425  of the lower pump cover  420  and pumps the sucked urea solution between the rotor  205  and the stator  215 , so that the urea solution is pumped through the outlet  315 . The pump  410  may be a gerotor. 
         [0061]    The fastening bolts  430  are fastened to the exterior stator over-molding  225  while passing through the lower pump cover  420 , the exterior stator over-molding  225  is inserted into the housing  435 , and a leading end of the housing  435  is bent and fixed to the exterior stator over-molding  225 . 
         [0062]      FIG. 5  is a partial cross-sectional view of the pump unit, the motor, and the discharge unit according to the exemplary embodiment of the present inventive concept. 
         [0063]    Referring to  FIG. 5 , the pump unit includes a pump unit  552  and a motor  554 , and the pump unit  552  sucks a urea solution through the inlet  425  of the lower pump cover  420 , while the pump  410  rotates by the rotating shaft  200  to pump the urea solution between the rotor  205  and the stator  215 . 
         [0064]    The motor  554  rotates the rotating shaft  200  and the pump  410  through a structure of the stator  215  and the rotor  205 , and provides a urea solution flow gap between the rotor  205  and the stator  215 . 
         [0065]    The outlet  315  is formed at a part corresponding to the rotating shaft  200  at a center of the upper cover  300 , and the outlet adaptor  1112  is integrally formed at a leading end of the upper cover  300 . 
         [0066]    A relief valve  500  relieving pressure to an upper side (a right side of  FIG. 5 ) is disposed at an end of the outlet  315  in the outlet adaptor  1112 , and a urea solution is discharged to a lower side (a left side of  FIG. 5 ). 
         [0067]      FIG. 6  is a partial exploded perspective view of the discharge unit according to the exemplary embodiment of the present inventive concept. 
         [0068]    Referring to  FIG. 6 , an outlet adaptor  1112  having the outlet  315  opened to a lower side is integrally formed at a front side of the upper cover  300 , and a relief pipe  710 , in which the relief valve  500  is disposed, protrudes and is integrally formed on the upper cover  300 . 
         [0069]    A pipe-shaped metal port  605  is inserted into the outlet  315  formed at the lower side of the outlet adaptor  1112 , a port o-ring  610  as a sealing member is mounted on an outer peripheral surface of the pipe-shaped metal port  605 , and the three-phase terminal  305  connecting a power supply (not shown) to one side of the outlet  315  protrudes in a downward direction and is formed at a lower part of the outlet adaptor  1112 . 
         [0070]    A first adaptor o-ring  600  is disposed along a circumference at a lower side of an edge of the outlet adaptor  1112 , and the first adaptor o-ring  600  forms a sealing structure with an internal surface of an adaptor insertion recess  715  of  FIG. 7 . 
         [0071]      FIG. 7  is a partial perspective view illustrating a state in which the bracket is fastened to the adaptor part in the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
         [0072]    Referring to  FIG. 7 , the adaptor insertion recess  715  is formed on an upper surface of the bracket  105 , a lower part of the outlet adaptor  1112  is inserted into the adaptor insertion recess  715 , and the clip  705  fixes the outlet adaptor  1112  to the adaptor insertion recess  715 . 
         [0073]    Further, the relief pipe  710  extends to an upper part of the outlet adaptor  1112 , and the relief valve  500  is disposed at an internal side of the relief pipe  710 . 
         [0074]      FIG. 8  is a partial exploded perspective view illustrating a part fastened to the adaptor on the bracket according to the exemplary embodiment of the present inventive concept. 
         [0075]    Referring to  FIG. 8 , a second adaptor o-ring  800  is in close contact with a bottom surface of the adaptor insertion recess  715 , and the second adaptor o-ring  800  is in close contact with a lower surface of the outlet adaptor  1112  to form a sealing structure between the bracket  105  and the outlet adaptor  1112 . 
         [0076]    Further, a power connection hole  805  is formed on the bottom surface of the adaptor insertion recess  715  so that the three-phase terminal  305  protruding from the lower surface of the outlet adaptor  1112  is connected with the power supply. 
         [0077]      FIG. 9  is a partial exploded perspective view illustrating a fastening structure of the bracket and the thawing unit according to the exemplary embodiment of the present inventive concept. 
         [0078]    Referring to  FIG. 9 , the hooks  900  protrude and are integrally formed on the bracket  105 , and the hook fastening parts  905 , which are fastened to the hook  900  to be fixed, are integrally formed at a side lower portion of the thawing unit  120 . 
         [0079]      FIG. 10  is a partial cross-sectional view of the bracket according to the exemplary embodiment of the present inventive concept. 
         [0080]    Referring to  FIG. 10 , a sensor unit  1001  is disposed on the bracket  105 , the sensor unit  1001  includes a sensor cell  1000 , and the sensor cell  1000  is covered by a sealant and the like, and foreign substances such as a urea solution are fundamentally prevented from flowing into the sensor cell  1000  by fixing the sensor cell  1000 . The sensor unit  1001  may include a temperature sensor, a pressure sensor, or a level sensor. 
         [0081]      FIG. 11  is a partial exploded perspective view of the thawing unit according to the exemplary embodiment of the present inventive concept. 
         [0082]    Referring to  FIG. 11 , the thawing unit  120  includes a positive temperature coefficient (PTC) thermistor  1005 , a PTC guide  1010 , power supply terminal plates  1015 , a polyimide adhesive film  1020 , and a thawing over-molding  1025 . 
         [0083]    A recess is formed at a center of the PTC guide  1010 , the PTC thermistor  1005  is inserted into and disposed at the recess, and the power supply terminal plates  1015  are in close contact with both surfaces of the PTC guide  1010 . 
         [0084]    The polyimide adhesive film  1020  is attached to each of both external surfaces of the power supply terminal plate  1015 , and the thawing over-molding  1025  is formed to completely surround an external side of the polyimide adhesive film  1020 . 
         [0085]      FIG. 12  is a partial exploded perspective view of the discharge unit according to the exemplary embodiment of the present inventive concept. 
         [0086]    Referring to  FIG. 12 , the outlet adaptor  1112  protrudes and is integrally formed at the front side of the upper cover  300 , the relief pipe  710  protrudes and is integrally formed at an upper side of the outlet adaptor  1112 , and the relief valve  500  is disposed at an inner side of the relief valve  710 . 
         [0087]    As illustrated in  FIG. 12 , the relief valve  500  includes an elastic member  1200  and a check ball  1205 , and when the elastic member  1200  elastically supports the check ball  1205  and a pressure of the urea solution pumped through the outlet  315  is equal to or larger than a predetermined value, the urea solution pushes the check ball  1205  and is relieved to the upper side of the outlet adaptor  1112 . 
         [0088]      FIG. 13  is a partial exploded perspective view illustrating a structure of a connector in the urea solution pumping system according to the exemplary embodiment of the present inventive concept. 
         [0089]    Referring to  FIG. 13 , a collective connector  1300  is fastened to a lower part of the bracket  105  to be connected to respective elements, and the collective connector  1300  is electrically connected with each of a heater connector  1305 , a pressure sensor connector  1310 , a motor connector  1315 , and a level/temperature sensor connector  1320 . 
         [0090]    The heater connector  1305  is electrically connected with the PTC thermistor  1005  of the thawing unit  120 , the pressure sensor connector  1310  is electrically connected with the pressure sensor, the motor connector  1315  is electrically connected with the rotor  205  or the stator  215 , and the level/temperature sensor connector  1320  is electrically connected with the level sensor and the temperature sensor, respectively. 
         [0091]    Accordingly, the urea solution pump unit according to the present disclosure may improve sealing performance and anti-corrosive performance by adopting the rotor molding and the stator molding formed by mixing engineering plastic and glass fiber. 
         [0092]    Further, the o-ring for sealing is applied to each connection portion to prevent a urea solution from permeating into a power supply system. The metal port is applied to the inner side of the outlet, and thus it is possible to improve freezing stability and durability. 
         [0093]    In the exemplary embodiment of the present inventive concept, the sensor unit includes a temperature sensor, a level sensor, or a pressure sensor, detailed structures of which are referred to in the publicly disclosed technology. 
         [0094]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.