Liquid Supply Device for Exhaust Gas Post-Treatment Device

Abstract

In a thermal-maintaining device ( 40 ) which is mounted to thermally maintain a pipe ( 3 ) for supplying urea water solution U stored in the inside of a tank ( 2 ) to an exhaust gas post-treatment device ( 100 ), a selecting part ( 50 ) which selectively outputs an ambient temperature signal (S 2 ) when it is determined that the urea water solution (U) in the inside of the pipe ( 3 ) is frozen based on a flow state of the urea water solution (U) in the inside of the pipe ( 3 ), and selectively outputs a tank temperature signal (S 1 ) when it is determined that the urea water solution (U) in the inside of the pipe ( 3 ) flows is provided. Further, a drive current (Y) necessary for thermal-maintenance is supplied to a heater ( 17 A) in response to an output signal (S 3 ) from the selecting part ( 50 ).

1 . A liquid supply device for an exhaust gas post-treatment device which supplies liquid stored in the inside of a tank to an exhaust gas purifying device through a pipe, and the pipe being thermally maintained using a thermally-maintaining device after thawing the liquid in the inside of the tank, wherein the thermally-maintaining device includes: 
 a tank temperature sensor which detects a temperature in the inside of the tank;    an ambient temperature sensor which detects an ambient temperature;    a heater which heats the pipe;    a selecting part which selects either one of an output of the ambient temperature sensor and an output of the tank temperature sensor based on a flow state of the liquid in the inside of the pipe; and    a driving part which supplies a current for thermal-maintenance necessary for thermal-maintenance in response to the output from the selecting part.    
   
   
       2 . A liquid supply device for an exhaust gas post-treatment device according to  claim 1 , wherein the selecting part includes a detecting part which detects a flow state of liquid in the inside of the pipe, and a switching part which selects either one of the output of the ambient temperature sensor and the output of the tank temperature sensor in response to the detecting part.  
   
   
       3 . A liquid supply device for an exhaust gas post-treatment device according to  claim 1 , wherein the selecting part selectively outputs the output of the ambient temperature sensor when it is determined that the liquid is frozen in the inside of the pipe based on the flow state of the liquid in the inside of the pipe, and selectively outputs the output of the tank temperature sensor when it is determined that the liquid flows in the inside of the pipe.  
   
   
       4 . A liquid supply device for an exhaust gas post-treatment device according to  claim 1 , wherein the driving part outputs a pulse current of a duty ratio which is controlled in response to the output from the selecting part.  
   
   
       5 . A liquid supply device for an exhaust gas post-treatment device according to  claim 4 , wherein the driving part sets the duty ratio of the pulse current to a predetermined fixed value when thawing the liquid in the inside of the tank.  
   
   
       6 . A liquid supply device for an exhaust gas post-treatment device according to  claim 4 , wherein the driving part further includes a determining part which determines whether the liquid in the inside of the pipe is required to be thawed or thermally maintained or not, and outputs the pulse current only when it is determined that the liquid in the inside of the pipe is required to be thawed or thermally maintained.  
   
   
       7 . A liquid supply device for an exhaust gas post-treatment device according to  claim 5 , wherein the driving part further includes a determining part which determines whether the liquid in the inside of the pipe is required to be thawed or thermally maintained or not, and outputs the pulse current only when determined that the liquid in the inside of the pipe is required to be thawed or thermally maintained.  
   
   
       8 . A liquid supply device for an exhaust gas post-treatment device according to  claim 6 , wherein the determining part responds to the tank temperature sensor or the ambient temperature sensor and performs the determination based on whether either one of the tank temperature and an ambient temperature becomes a urea-water freezing temperature or below.  
   
   
       9 . A liquid supply device for an exhaust gas post-treatment device according to  claim 7 , wherein the determining part responds to the tank temperature sensor or the ambient temperature sensor and performs the determination based on whether either one of a tank temperature and an ambient temperature becomes a urea-water freezing temperature or below.  
   
   
       10 . A liquid supply device for an exhaust gas post-treatment device according to  claim 2 , wherein the selecting part selectively outputs the output of the ambient temperature sensor when it is determined that the liquid is frozen in the inside of the pipe based on the flow state of the liquid in the inside of the pipe, and selectively outputs the output of the tank temperature sensor when it is determined that the liquid flows in the inside of the pipe.  
   
   
       11 . A liquid supply device for an exhaust gas post-treatment device according to  claim 2 , wherein the driving part outputs a pulse current of a duty ratio which is controlled in response to the output from the selecting part.