Urea heating system and heating method thereof

Abstract

A urea solution heating device prevents freezing of a urea solution by using exhaust gas of an engine. More particularly, a urea solution heating device may use a pressure difference between an exhaust gas pipe and a muffler to bypass the exhaust gas to exchange heat between the exhaust gas and the urea solution. The urea solution heating device may include an exhaust gas pipe, a muffler, a first bypass pipe diverged from the exhaust gas pipe, a urea solution tank to which the bypassed exhaust gas is supplied, a second bypass pipe connected to the muffler, and a heat exchanger, wherein the exhaust gas sequentially flows through the first bypass line, the heat exchanger, and the second bypass line by a pressure difference between the exhaust gas pipe and the muffler. An urea solution heating method is also described.

What is claimed is: 
     
         1 . A urea solution heating device, comprising:
 an exhaust gas pipe through which exhaust gas of an engine is exhausted;   a muffler connected to one end of the exhaust gas pipe to exhaust the exhaust gas outside;   a first bypass pipe diverging from the exhaust gas pipe to bypass the exhaust gas;   a urea solution tank filled with urea solution to which the bypassed exhaust gas is supplied;   a second bypass pipe connected to the muffler and that supplies the exhaust gas passing the urea solution tank to the muffler; and   a heat exchanger disposed in the urea solution tank to connect the first bypass pipe with the second bypass and through which the exhaust gas flows such that the exhaust gas heats the urea solution, wherein the exhaust gas sequentially flows through the first bypass line, the heat exchanger, and the second bypass line by a pressure difference between the exhaust gas pipe and the muffler.   
     
     
         2 . The urea solution heating device of  claim 1 , wherein a solenoid valve is disposed on the first bypass pipe to selectively bypass the exhaust gas. 
     
     
         3 . The urea solution heating device of  claim 2 , wherein a temperature sensor is disposed on the urea solution tank to detect the temperature of the urea solution. 
     
     
         4 . The urea solution heating device of  claim 3 , further comprising a dosing control unit (DCU) connected to the solenoid valve and the temperature sensor, and receives a temperature signal of the urea solution from the temperature sensor to operate the solenoid valve. 
     
     
         5 . The urea solution heating device of  claim 1 , wherein an insulating member is disposed in the urea solution tank, both ends of the insulating member are opened and urea solution housing holes are formed in a side surface thereof, and one of the ends is engaged with a urea solution tank cap to be closed. 
     
     
         6 . The urea solution heating device of  claim 5 , wherein the heat exchanger is disposed inside the insulating member. 
     
     
         7 . The urea solution heating device of  claim 6 , wherein the heat exchanger is made by bending a pipe having a predetermine length several times such that the urea solution exchanges heat with the exhaust gas flowing in the heat exchanger. 
     
     
         8 . The urea solution heating device of  claim 6 , wherein the heat exchanger includes two ends, and an exhaust gas suction hole is formed in one end and an exhaust gas outlet is formed in the other end. 
     
     
         9 . The urea solution heating device of  claim 8 , wherein the exhaust gas suction hole is connected to the first bypass pipe through the urea solution tank cap, and the exhaust gas outlet is connected to the second bypass line through the urea solution tank cap. 
     
     
         10 . The urea solution heating device of  claim 5 , wherein a urea solution outlet is formed on the urea solution tank cap such that the urea solution of the urea solution tank is exhausted outside. 
     
     
         11 . The urea solution heating device of  claim 10 , wherein a urea solution pump is disposed at a surface of an interior direction of the insulating member of the area solution tank cap to exhaust the urea solution in the urea solution tank to the outside through the urea solution outlet. 
     
     
         12 . The urea solution heating device of  claim 5 , wherein a sealing member is disposed between an interior circumference of the urea solution tank cap and an exterior circumference of the insulating member to prevent leakage of the urea solution. 
     
     
         13 . The urea solution heating device of  claim 4 , wherein a pressure sensor is disposed at one end of the first bypass pipe diverged from the exhaust gas pipe and at one end of the second bypass pipe connected to the muffler to detect exhaust gas pressure of the exhaust gas pipe and the muffler. 
     
     
         14 . The urea solution heating device of  claim 13 , wherein the DCU is connected to the pressure sensors to open the solenoid valve when the pressure difference between the exhaust gas pipe and the muffler is larger than a predetermined value. 
     
     
         15 . A urea solution heating method, in a urea solution heating device that includes an exhaust gas pipe exhausting exhaust gas of an engine, a muffler connected to the exhaust gas pipe, a urea solution tank filled with a urea solution, a bypass pipe diverging from the exhaust gas pipe to be connected to the muffler through the urea solution tank, and a solenoid valve that selectively open/closes the bypass pipe, comprising the steps of:
 determining whether a rotation speed of the engine is faster than an idle rotation speed of the engine (S 100 );   determining whether a urea solution temperature is less than a predetermined value through a temperature sensor disposed in the urea solution tank (S 110 );   determining whether a rotation speed of the engine is slower than a maximum rotation speed of the engine (S 120 );   determining whether a load of the engine is less than a permissible value (S 130 );   opening the solenoid valve if steps S 100 , S 110 , S 120 , and S 130  are satisfied (S 150 );   closing the solenoid valve if one of steps S 100 , S 110 , S 120 , and S 130  is not satisfied (S 160 ); and   performing the procedures from step S 100  again if step S 150  or step S 160  is performed.