Patent Publication Number: US-2016222859-A1

Title: Method and system for detecting malfunctioning of fluid tank of machine

Description:
TECHNICAL FIELD 
     The present disclosure relates to a fluid tank of a machine, and more specifically, to a method for detecting a malfunctioning of the tank containing the fluid. 
     BACKGROUND 
     Machines employing diesel engines generally use an after-treatment system. The after-treatment system utilizes a selective catalytic reduction (SCR) process for treating exhaust emissions. The SCR process includes reducing nitrogen oxide (NO x ) emissions to nitrogen (N 2 ), water (H 2 O), and carbon dioxide (CO 2 ), by using a reducing agent, known as diesel exhaust fluid (DEF). The diesel exhaust fluid (DEF) is a clear non-hazardous liquid made up of a solution of about 32.5% high-purity urea in de-mineralized water. A small quantity of the DEF is injected into high temperature exhaust stream upstream of a SCR catalyst, where the DEF vaporizes and decomposes to form ammonia (NH 3 ) and carbon dioxide (CO 2 ). Further, the ammonia in conjunction with the SCR catalyst converts the (NO x ) to harmless nitrogen (N 2 ) and water (H 2 O). 
     Typically, the DEF is stored in tanks for dispensing at a customer&#39;s site where the DEF is replenished in a machine. The tank includes a cap with air passages in it or the tank is coupled to a breather system which is adapted to facilitate exchange of air between the tank and atmosphere. The exchange of air between the tank and the atmosphere helps in maintaining atmospheric pressure inside the tank. The tank is further coupled to a pump and a dispensing system for drawing the DEF out of the tank. The air passages in the cap of the tank or the breather system can get blocked with debris in the surrounding environment or with crystallized urea, left after vaporization of water from the DEF. The blockage of the cap or the breather system creates a vacuum inside the tank leading to shrinkage of the tank. Further, the ability of the pump to draw the DEF out of the tank reduces drastically due to creation of vacuum inside the tank. The blockage of the cap or the breather system, if left unnoticed, leads to degradation in performance of the after-treatment system. Therefore, there is a need for a method that can detect the blocked cap of the tank storing the DEF or the blocked breather system coupled to the tank storing the DEF immediately so that they can be replaced without affecting the performance of the after-treatment system. 
     U.S. Pat. No. 5,339,788 discloses an arrangement for conducting a tank-venting diagnosis for a motor vehicle equipped with a tank-venting apparatus. The tank-venting apparatus includes a tank-venting valve actuated by an actuator between an open position and a closed position. The arrangement includes a pressure-difference sensor means for measuring the underpressure, and a control means having a sequence control/diagnosis unit connected to the pressure-difference sensor for receiving a signal indicative of the measured underpressure. The sequence control/diagnosis unit is adapted to determine when the measured underpressure exceeds a threshold underpressure and to emit a signal to the actuator for closing said tank-venting valve. However, such an arrangement is complex, and is expensive for conducting the tank-venting diagnosis. Therefore, there is a need of an improved method for detecting any malfunctioning of the tank containing diesel exhaust fluid (DEF). 
     SUMMARY OF THE DISCLOSURE 
     in one aspect of the present disclosure, a method for detecting a malfunctioning of a tank containing fluid is disclosed. The method includes calculating a rate of consumption of the fluid in the tank. The method further includes calculating an estimated change in level of the fluid in the tank based on the rate of consumption of the fluid. The method further includes determining a measured change in level of the fluid in the tank. The method further includes comparing the estimated change in level of the fluid with the measured change in level of the fluid, The method further includes determining the malfunctioning of the tank if a difference between the estimated change in level of the fluid and the measured change in level of the fluid exceeds a predetermined value. 
     Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic view of a system for treating exhaust of a diesel engine, the system including a tank containing fluid, in accordance with the concepts of the present disclosure; 
         FIG. 2  illustrates a schematic view of the tank having a cap with air-passages, in accordance with the concepts of the present disclosure; 
         FIG. 3  illustrates a schematic view of the tank having the cap with blocked air-passages, in accordance with the concepts of the present disclosure; and 
         FIG. 4  illustrates a flowchart of a method for detecting a malfunctioning of the tank containing the fluid, in accordance with the concepts of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a system  10  for treating exhaust of a diesel engine  12  is provided. The system  10  includes a tank  14 , a dispensing system  16 , a processor  18 , and a catalytic converter  20 . The tank  14  contains fluid and air. In an embodiment, the fluid contained in the tank  14  is a diesel exhaust fluid (DEF). The DEF is a clear non-hazardous liquid made up of a solution of about 32.5% high purity urea in de-mineralized water. The DEF is replenished in the tank  14  by a nozzle  22 . The nozzle  22  is further connected to a DEF supply (not shown). The nozzle  22  dispenses the DEF into a first conduit  24  coupled to the tank  14 . The tank  14  is provided with a cap  26  with a number of air passages  28  to receive air into the tank  14  from an atmosphere  30 . It will be apparent to one skilled in the art that the air from the atmosphere  30  may be provided to the tank  14  by various mechanisms such as, but not limited to, the air passages  28  in the cap  26 , a breather system (not shown) coupled to the tank  14  without departing from the meaning and the scope of the disclosure. 
     An exhaust conduit  32  is adapted to receive exhaust from the diesel engine  12 . The exhaust conduit  32  includes a second conduit  34 , a filter  36 , and a third conduit  38 . The diesel engine  12  is in fluid communication with the filter  36  via the second conduit  34 . Further, the filter  36  is in fluid communication with the catalytic converter  20  via the third conduit  38 . The exhaust, discharged from the diesel engine  12  into the second conduit  34  of the exhaust conduit  32 , includes nitrogen oxides (NO x ), particulate matter (PM), unburned hydrocarbons (HC), carbon monoxide (CO), among others. The filter  36  traps the particulate matter (PM) when the exhaust flows into the filter  36 . Further, the exhaust free from the particulate matter (PM) is discharged into the third conduit  38  of the exhaust conduit  32 . 
     The dispensing system  16  includes a pump  40 , a flow meter  42 , an injector  44 , and a sensor module  46 . The pump  40  is in fluid communication with the tank  14  and is adapted to draw the DEF from the tank  14  via a fourth conduit  48 . The pump  40  is coupled to the flow meter  42 , which is further coupled to the injector  44 . The flow meter  42  is adapted to regulate the flow of the DEF received from the pump  40  into the injector  44 . The injector  44  is coupled to the sensor module  46 . The injector  44  injects a small quantity of the DEF into a mixing zone  50  in the third conduit  38  of the exhaust conduit  32 . The mixing zone  50  corresponds to a zone where the small quantity of the DEF is mixed with the nitrogen oxides (NO x ). The DEF injected into the mixing zone  50  hydrolyzes into ammonia (NH 3 ) and carbon dioxide (CO 2 ). Further, the ammonia (NH 3 ) from the DEF and the nitrogen oxides (NO) flow from the third conduit  38  into the catalytic converter  20 . The ammonia (NH 3 ) and the nitrogen oxides (NO x ) react in presence of a catalyst provided in the catalytic converter  20 . The ammonia (NH 3 ) reduces the nitrogen oxides (NO) in the catalytic converter  20  into nitrogen (N 2 ) and water (H 2 O), as shown by arrows  52 . 
     A level sensor  54  is provided in the tank  14 . The level sensor  54  is configured to measure a change in level of the fluid in the tank  14 . The level sensor  54  is supported in the tank  14  by a fifth conduit  56 . The processor  18  is coupled to the level sensor  54  in the tank  14  via a first communication line  58 . The processor  18  is further coupled to the sensor module  46  in the dispensing system  16  via a second communication line  60 . The sensor module  46  includes a pressure sensor (not shown) and a time sensor (not shown). The processor  18  is coupled to a dashboard  62  via a third communication line  64 . 
     Referring to  FIGS. 1, and 2 , the tank  14  is made up of plastic. The tank  14  receives air from the atmosphere  30  via the air passages  28  in the cap  26 . As the DEF is consumed from the tank  14 , the pressure in the tank  14  decreases. The air received from the atmosphere  30  into the tank  14  creates atmospheric pressure inside the tank  14  and compensates for the pressure reduced due to consumption of the DEF from the tank  14 . It is essential to maintain atmospheric pressure inside the tank  14  for efficient operation of the pump  40  of the dispensing system  16  so that the pump  40  continues to draw DEF form the tank  14 . 
     The air passages  28  in the cap  26  of the tank  14  get blocked leading to a malfunctioning in the cap  26  of the tank  14 . The processor  18  of the system  10  determines the malfunctioning in the cap  26  of the tank  14 . The processor  18  calculates a rate of consumption of the DEF from the tank  14 . The injector  44  of the dispensing system  16  is provided with a solenoid valve (not shown). The solenoid valve (not shown) of the injector  44  is energized to inject the DEF into the mixing zone  50  of the third conduit  38  of the exhaust conduit  32 . The pressure sensor (not shown) of the sensor module  46 , connected to the injector  44 , records the supply pressure of the DEF into the mixing zone  50  of the third conduit  38 . The pressure sensor (not shown) of the sensor module  46 , connected to the processor  18  via the second communication line  60 , communicates the recorded supply pressure to the processor  18 . The time sensor (not shown) of the sensor module  46  measures the duration of injection of the DEF into the exhaust conduit  32 . The processor  18  references the map of the supply pressure and the duration of injection of the DEF to calculate the rate of consumption of DEF in the tank  14 . 
     The level of the DEF in the tank  14  decreases when DEF is injected into the exhaust conduit  32 . The processor  18  calculates an estimated change in level of the DEF in the tank  14  based on the rate of consumption of the DEF and the dimensions of the tank  14 . The level sensor  54  determines a measured change in level of the DEF in the tank  14 . The level sensor  54 , connected to the processor  18  by the first communication line  58 , communicates the measured change in level of the DEF in the tank  14  to the processor  18 . The processor  18  compares the estimated change in level of the DEF with the measured change in level of the DEF in the tank  14 . 
     The processor  18  determines the malfunctioning of the tank  14  if a difference between the estimated change in level of the DEF and the measured change in level of the DEF exceeds a predetermined value. The measured change in level of the DEF is less than the estimated change in level of the DEF if the tank  14  malfunctions. The processor  18  indicates an error to the dashboard  62  if the malfunctioning is determined by the processor  18 . The dashboard  62  displays the error to an operator (not shown). The operator (not shown), after identifying the error, cleans the cap  26  or replaces the cap  26  of the tank  14 . The indication of the error by the processor  18  depends on the degree of the error. If the error is large, the processor  18  indicates the error to the dashboard  62  else, if the error is small as set within the prescribed limit, the processor  18  does not indicate the error to the dashboard  62  but saves the error. The error is analyzed further by service engineers during maintenance of a machine (not shown). 
     Referring to  FIG. 3 , the air passages  28  in the cap  26  of the tank  14  are blocked. The air passages  28  in the cap  26  of the tank  14  get blocked either with debris from surrounding environment or with the dried DEF. Some amount of DEF enters the air passages  28  of the cap  26  when the machine (not shown) moves at extreme angles. The DEF in the cap  26  dries, when exposed to the air in the air passages  28  in the cap  26 , leaving behind crystallized urea, and leading to blockage of air passages  28 . In the absence of air inside the tank  14 , the atmospheric pressure decreases and fails to compensate the reduction in pressure due to consumption of the DEF inside the tank  14 . As a result, vacuum is created inside the tank  14  and the tank  14  shrinks. The level sensor  54  determines the measured change in level of the DEF in the tank  14  to be less than expected. The delivery efficiency of the pump  40  is reduced, and thereby leading to failure of the dispensing system  16 . 
     It should be noted that the tank  14  may be made from materials which are as stiff as plastic. It will be apparent to one skilled in the art that the dispensing system  16  may operate without expensive instruments such as the flow meter  42  and the solenoid valve (not shown). The dispensing system  16  may include a metering pump (not shown), instead of the solenoid valve (not shown), that doses the amount of DEF injected in the exhaust conduit  32  without departing from the meaning and the scope of the disclosure. 
     INDUSTRIAL APPLICABILITY 
     Referring to  FIG. 4 , a method  66  for detecting the malfunctioning of the tank  14  containing fluid is described in conjunction with  FIGS. 1, 2, and 3 . At step  68 , the processor  18  calculates the rate of consumption of the fluid (i.e. the diesel exhaust fluid (DEF)) in the tank  14 . The processor  18  calculates the rate of consumption of the DEF by referencing a map of supply pressure and the duration of injection of the DEF in the exhaust conduit  32 . At step  70 , the processor  18  calculates the estimated change in level of the DEF in the tank  14  based on the rate of consumption of the DEF. At step  72 , the level sensor  54  determines the measured change in level of the DEF in the tank  14 . The level sensor  54 , connected to the processor  18  via the first communication line  58 , communicates the measured change in level of the DEF to the processor  18 . At step  74 , the processor  18  compares the estimated change in level of the DEF with the measured change in level of the DEF. At step  76 , the processor  18  determines the malfunctioning of the tank  14  if the difference between the estimated change in level of the diesel exhaust fluid and the measured change in level of the diesel exhaust fluid exceeds a predetermined value. 
     The present disclosure discloses the method  66  for detecting the malfunctioning of the tank  14 . The method  66  efficiently detects that the cap  26  is blocked (as shown in  FIG. 3 ). The processor  18  compares the estimated change in level of the DEF in the tank  14  with the measured change in level of the DEF in the tank  14 . The processor  18  determines the malfunctioning of the tank  14  if a difference between the estimated change in level of the DEF in the tank  14  and the measured change in level of the tank  14  exceeds a predetermined value. Further, the processor  18  indicates an error to the dashboard  62  informing the operator if the malfunctioning is determined. The operator of the machine immediately changes the cap  26  or replaces the cap  26 , which is blocked, so that the air from the atmosphere  30  continues to enter the tank  14 . The method  66  ensures the proper working of the dispensing system  16  so that the system  10  treats exhaust of the diesel engine  12  without any failure. The method  66  is a cost effective method to detect the malfunctioning of the tank  14  and the method  66  provides real time indication of the malfunctioning of the tank  14  to the operator through the dashboard  62 . 
     While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.