Abstract:
A leak detection method of a reducing agent pumping system including a reducing agent tank, an injector, a line formed through the reducing agent tank and the injector, and a pumping module disposed in the line may include pumping a reducing agent to the injector with a pump of the pumping module and detecting a pressure thererof, operating the pump at a predetermined load or less and stopping an operation of the injector, when it is determined that a detected pressure is between a first set value and a second set value, operating a heater for heating the reducing agent in the pumping module for a predetermined time, and determining that leak occurred in the line between the pumping module and the injector, when it is determined a temperature of the reducing agent in the pumping module is lower than a predetermined value.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Korean Patent Application No. 10-2013-0143262 filed on Nov. 22, 2013, the entire contents of which is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a leak detection method of a reducing agent pumping system that pumps a reducing agent safely and pleasantly by pumping a reducing agent stored in a reducing agent tank to an injector and rapidly detecting leak of the reducing agent in the pumping. 
         [0004]    2. Description of Related Art 
         [0005]    At present, a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF), a nitrogen oxide purifying unit (LNT, lean NOx trap), and a selective catalytic reduction unit (SCR) have been considered in diesel engines of vehicle to cope with the exhaust gas regulations. 
         [0006]    Particularly, in the requirements of exhaust gases in Europe, ARTEMIS mode is examined instead of NEDC mode, which is a typical actual high-speed running condition. In the actual high-speed running condition, since the DOC+DPF+LNT system exhausts nitrogen oxide (NOx), there is a need of a method of reducing nitrogen oxide. 
         [0007]    Accordingly, the selective catalyst reduction system is used, which reduces nitrogen oxide by spraying urea, which is a reducing agent, to the front of a catalyst. 
         [0008]    In order to effectively spray urea that is a reducing agent, a pumping pressure of about 9 bar is required, and the reducing agent pumping system may stop when the pumping pressure drops. Bubbles flowing in the pumping line or malfunction of a pressure sensor may stop the reducing agent pumping system. 
         [0009]    The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
       BRIEF SUMMARY 
       [0010]    Various aspects of the present invention are directed to providing a leak detection method of a reducing agent pumping system having advantages of enabling a reducing agent pumping system to more stably operate by more precisely determining leak in a pumping line even if a pumping pressure for a reducing agent drops due to bubbles flowing in the pumping line or malfunction of a pressure sensor. 
         [0011]    In an aspect of the present invention, a leak detection method of a reducing agent pumping system including a reducing agent tank, an injector, a line formed through the reducing agent tank and the injector, and a pumping module disposed in the line, may include pumping a reducing agent to the injector with a pump of the pumping module and detecting a pressure thererof, operating the pump at a predetermined load or less and stopping an operation of the injector, when it is determined that a detected pressure is larger than a first set value and smaller than a second set value which is larger than the first set value, operating a heater for heating the reducing agent in the pumping module for a predetermined time, and determining that leak occurred in the line between the pumping module and the injector, when it is determined a temperature of the reducing agent in the pumping module is lower than a predetermined value. 
         [0012]    The method may further include increasing a pump load of the pumping module to a maximum and making a load of the injector to zero when the detected pressure is between the first and second set values. 
         [0013]    The method may further include generating a warnign signal when the detcted pressure is lower than the first set value. 
         [0014]    The method may further include comparing the first temperature of the reducing agent in the reducing agent tank with a second temperature of the reducing agent in the pumping mold added with a predetermined value, and generating supply pressure drop warning signal when the first first temperature is smaller than the second temperature added with the predetermined value, and restoring the reducing agent when the first first temperature is larger than the second temperature added with the predetermined value. 
         [0015]    The method may further include determining that pumping is normally performed, when it is determined that the detected pressure is larger than a third set value which is larger than the second set value. 
         [0016]    The method may further include a pressure sensor that is disposed at an outlet of the pump and detects pumping pressure, in the pumping module. 
         [0017]    The method may further include a temperature sensor that is disposed at an inlet or an outlet of the pump and detects the temperature of the reducing agent, in the pumping module. 
         [0018]    In the determining of the leak, the set value is determined from the temperature of the reducing agent in the reducing agent tank. 
         [0019]    After the operating of the heater for a predetermined time, the heater is turned off. 
         [0020]    After the heater is turned off, the determining of the leak is performed. 
         [0021]    The reducing agent in the reducing agent tank that may include generating a pressure drop warning signal, when it is determined that the detected pressure is a predetermined value or less, is maintained at a predetermined temperature by a coolant of an engine. 
         [0022]    According to the present invention, it is possible to effectively prevent the system from temporarily stopping due to bubbles flowing in the supply line of urea or malfunction of the pressure sensor. 
         [0023]    Further, when the pumping pressure of urea drops due to a temporal reason, it is possible to easily determine unnecessary actual leak of a reducing agent, using the temperature of the reducing agent in the pumping module. 
         [0024]    The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a schematic diagram a reducing agent pumping system according to an exemplary embodiment of the present invention. 
           [0026]      FIG. 2  is a flowchart illustrating a leak detection method of a reducing agent pumping system according to an exemplary embodiment of the present invention. 
           [0027]      FIG. 3  is a flowchart illustrating the leak detection method of a reducing agent pumping system according to an exemplary embodiment of the present invention. 
           [0028]      FIG. 4  is a graph showing temperature according to the leak state in a reducing agent pumping system according to an exemplary embodiment of the present invention. 
       
    
    
       [0029]    It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
         [0030]    In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
       DETAILED DESCRIPTION 
       [0031]    Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0032]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0033]      FIG. 1  is a schematic diagram a reducing agent pumping system according to an exemplary embodiment of the present invention. 
         [0034]    Referring to  FIG. 1 , a reducing agent pumping system includes a reducing agent tank  100 , a restoring line  162 , a supply line  160 , a pumping module  110 , a pressure sensor  112 , a temperature sensor  114 , an exhaust line  150 , an injector  140 , a selective catalytic reduction unit  130 , and a dodging controller  120 . 
         [0035]    The injector  140  is disposed in the exhaust line  150  to spray a reducing agent to an exhaust gas passing through the exhaust line  150  and the selective catalytic reduction unit  130  is disposed at the downstream side further than the injector  140 . 
         [0036]    The reducing agent that is sprayed from the injector is an aqueous urea solution and the reducing tank  100  is filled with an aqueous urea solution. The reducing agent tank  100  and the injector  140  are connected through a line and the line includes the supply line  160  and the restoring line  162 . 
         [0037]    The pumping module  110  is disposed at the middle of the supply line  160  and the restoring line  162 . A pump which pumps a reducing agent from the reducing agent tank  100  to the injector  140  is disposed in the pumping module  110 . 
         [0038]    The pressure sensor  112  and the temperature sensor  114  which detect the pressure and temperature of the pumped reducing agent, respectively, are disposed in the pumping module  110 , in which the pressure sensor  112  is disposed at the outlet of the pump and the temperature sensor  114  may be disposed at the outlet or the inlet. 
         [0039]    The pumping module  110 , the reducing agent tank  100 , the supply line  160 , and the restoring line  162  are each provided with a heater to prevent the aqueous urea solution, which is a reducing agent, from freezing. 
         [0040]    The heater of the reducing agent tank  100  controls the temperature of the reducing agent with the coolant of a engine, the pumping module  110 , the supply line  160 , and the restoring line  162  are provided with an electric heater  116 , and the reducing agent tank  100  is equipped with a lever sensor too which detects the level of the aqueous urea solution. 
         [0041]    The dodging controller  120  allows the aqueous urea solution, which is a reducing agent, to be sprayed to the exhaust gas passing through the exhaust line  150  by controlling the pumping module  110  and the injector  140  on the basis of the operation information and diagnosis information of the engine. 
         [0042]    In an exemplary embodiment of the present invention, when it is determined that the pumping pressure detected by the pressure sensor  112  of the pumping module  110  is 7.5 bar or more, it is determined that pumping is normally performed. On another hand, when the pumping pressure is less than 0.5 bar, the pumping pressure is low and a warning signal is generated. 
         [0043]    When it is determined that the pumping pressure detected by the pressure sensor  112  of the pumping module  110  is 0.5 bar or more and less than 7.5 bar, a leak detection mode is performed. In an exemplary embodiment of the present invention, 7.5 bar and 0.5 bar are values set in advance. 
         [0044]    When the leak detection mode is performed, the pump of the pumping module  110  is operated at the maximum output and the injector  140  stops operating. The heater  116  of the pumping module  110  is turned on and a set time (about  40  seconds) is maintained. 
         [0045]    Further, the heater  116  of the pumping module  110  is turned off and the first temperature of the reducing agent in the pumping module  110  and the second temperature of the reducing agent in the reducing agent tank  100  are compared. 
         [0046]    When the value obtained by adding a predetermined value (5° C.) to the second temperature is larger than the first temperature, the dodging controller  120  generates a pressure drop warning signal. Further, when the value obtained by adding a predetermined value (5° C.) to the second temperature is the first temperature or less, the dodging controller  120  restores the reducing agent in the supply line  160  through the restoring line  162  by controlling the pumping module  110 . 
         [0047]    In an exemplary embodiment of the present invention, with the injector  140  turned off and the pump of the pumping module  110  operated at the maximum output, when leak occurs at the downstream side from the pumping module  110 , a new reducing agent is supplied from the reducing agent tank  100  even though the heater  116  of the pumping module  110  heats the existing reducing agent, such that the temperature does not rapidly increase. 
         [0048]    In contrast, with the injector  140  turned off and the pump of the pumping module  110  operated at the maximum output, when there is no leak at the downstream side from the pumping module  110 , the heater  116  of the pumping module  110  heats the reducing agent and a new reducing agent is not supplied from the reducing agent tank  100 , such that the temperature of the reducing agent continuously increases. 
         [0049]    Accordingly, in an exemplary embodiment of the present invention, with the injector  140  turned off and the pump of the pumping module  110  operated at the maximum output, leak in the supply line  160  is determined by comparing the temperature of the reducing agent in the pumping module  110  with a predetermined value (temperature of the reducing agent in the reducing agent tank+5° C.). 
         [0050]    In an exemplary embodiment of the present invention, it is possible to effectively prevent the system from temporarily stopping due to bubbles flowing in the supply line of urea that is a reducing agent or malfunction of the pressure sensor. Further, when the pumping pressure of urea drops due to a temporal reason, it is possible to easily determine leak of a reducing agent, using the temperature of the reducing agent in the pumping module. 
         [0051]      FIG. 2  is a flowchart illustrating a leak detection method of a reducing agent pumping system according to an exemplary embodiment of the present invention. 
         [0052]    Referring to  FIG. 2 , control starts in S 200 , the pump of the pumping module  110  pumps an aqueous urea solution that is a reducing agent in S 205 , and a timer starts operation from zero in S 210 . 
         [0053]    In S 215 , it is determined whether the line pressure by the pump of the pumping module  110  is smaller than 7.5 bar. 
         [0054]    S 265  is performed when the line pressure is larger than 7.5, S 220  is performed and the timer starts operating when the line pressure is 7.5 bar or more, and whether the line pressure is smaller than 0.5 bar is determined in S 225 . 
         [0055]    When the line pressure is smaller than 0.5 bar, it is determined that the line pressure dropped abnormally and a warning signal is generated in S 230 . When it is determined that the line pressure is 0.5 bar or more, S 235  is performed. 
         [0056]    In S 235 , the pump load of the pumping module  110  is increased to the maximum and the load of the injector  140  is made zero. It is determined whether 40 seconds have passed in S 245 . When 40 seconds do not pass, the process returns to S 215 , and when 40 seconds have passed, S 250  is performed. 
         [0057]    The heater  116  that heats the reducing agent in the pumping module  110  is turned off in S 250  and the first temperature of the reducing agent in the pumping module  110  and the second temperature of the reducing agent in the reducing agent tank  100  are compared in S 255 . 
         [0058]    In more detail, 5° C. is added to the second temperature, and when the resultant value is smaller than the first temperature, S 230  is performed, and when the resultant value is the first temperature or more, S 260  is performed. In S 260 , the pumping module  110  restores the reducing agent in the supply line  160  through the restoring line  162 . 
         [0059]    In an exemplary embodiment of the present invention, refer to those known in the art, for the structure in which the pump of the pumping module  110  pumps an aqueous urea solution that is a reducing agent, the structure in which it restores the aqueous urea solution in the supply line  160 , the structure of the injector  140 , and the method of controlling the parts with the dodging controller  120 , and the detailed description is not provided. 
         [0060]    Further, the dodging controller  120  executes a series of programs or instructions for performing the leak detection method of a reducing agent pumping system according to an exemplary embodiment of the present invention. 
         [0061]      FIG. 3  is a flowchart illustrating the leak detection method of a reducing agent pumping system according to an exemplary embodiment of the present invention. 
         [0062]    Referring to  FIG. 3  pumping control on urea that is a reducing agent is started in S 300  and the line pressure of the supply line through which urea is pumped is detected in S 305 . In S 310 , it is determined whether the line pressure is within a predetermined range. When the line pressure is over the predetermined range, it is determined that the system is in a normal state, and when it is smaller than the predetermined range, an emergency warning signal is generated. 
         [0063]    When the line pressure is within the predetermined range, the pump of the pumping module  110  is operated at the maximum output in S 320  and the injector  140  is turned off in S 330 . The heater  116  of the pumping module  110  is turned on in S 340  and the predetermined time passes with the heater  116  turned on in S 350 . 
         [0064]    The heater  116  of the pumping module  110  is turned off in S 360 , the temperature of the reducing agent in the pumping module  110  and the temperature of the reducing agent in the reducing agent tank  100  are compared in S 370 , and it is determined whether there is leak in the supply line  160  in S 380 . Further, the reducing agent in the supply line  160  is restored to the reducing agent tank  100  by the restoring function of the pumping module  110  in S 390 . 
         [0065]      FIG. 4  is a graph showing temperature according to the leak state in a reducing agent pumping system according to an exemplary embodiment of the present invention. 
         [0066]    Referring to (a) of  FIG. 4 , the horizontal axis shows time and the vertical axis shows temperature. As shown in the figure, when the heater  116  is turned on, the internal temperature (reducing agent temperature) of the reducing agent tank  100  (urea tank) is maintained at a predetermined level, but the internal temperature (reducing agent temperature) of the pumping module  110  gradually increases. The reason that the internal temperature of the pumping module  110  gradually increases means that a reducing agent does not leak. 
         [0067]    Referring to (b) of  FIG. 4 , the horizontal axis shows time and the vertical axis shows temperature. As shown in the figure, even though the heater is turned on, the internal temperature (reducing agent temperature) of the pumping module  110  increases little, as compared with the internal temperature (reducing agent temperature) of reducing agent tank  100 . The reason that the internal temperature of the pumping module  110  increases less means that the reducing agent leaks and a new reducing agent is supplied to the pumping module  110 . 
         [0068]    For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
         [0069]    The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.