JP2013194666A - Cooling system of urea water for exhaust gas purification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling system of urea water for exhaust gas purification, the system capable of excellently cooling the urea water.SOLUTION: In a cooling system 10 of urea water for exhaust gas purification, a urea water cooling circuit 11 is provided separately from an engine cooling circuit 7 for an engine 6 mounted on a construction machine. The urea water cooling circuit 11 includes a cooling tube 20 for cooling a urea water supply tube 4 for supplying urea water from a urea water tank 2 to a urea water supply valve 5, an electric pump 30 for supplying coolant water to the cooling tube 20, and a radiator 40 to which the coolant water flowing out from the cooling tube 20 inflows. The coolant water flowing out from the radiator 40 returns to the electric pump 30 for circulatation.

Description

  The present invention relates to a cooling system for urea water for purifying exhaust gas, and more particularly to a cooling system for urea water for purifying exhaust gas of construction machinery.

  Conventionally, as an exhaust gas purification device for an internal combustion engine, a NOx selective reduction catalyst (SCR: Selective Catalytic Reduction) is provided, and urea water as a reducing agent is supplied into the exhaust gas upstream of the NOx selective reduction catalyst. It is known that ammonia obtained from urea water reacts with NOx in exhaust gas, and NOx is decomposed into nitrogen and oxygen to be purified. The urea water is sent from the urea water tank to the supply valve through the supply pipe, and is supplied into the exhaust gas from the supply valve.

  At this time, if the temperature of the urea water sent to the supply valve becomes too high, various problems occur. Therefore, in order to prevent the problem from occurring, a cooling device is provided in the supply pipe or the supply is performed. It has been proposed to provide a cooling device in a return pipe for returning urea water from the valve to the urea water tank (see, for example, FIGS. 1 and 2 of Patent Document 1).

JP 2011-214580 A

  However, since the cooling device of Patent Document 1 is formed by a part of the supply pipe and the return pipe and uses the traveling wind of the vehicle as a cooling medium, such a device is applied to a construction machine. It is difficult. That is, for example, as represented by a hydraulic excavator, the construction machine does not move at a high speed in the work site and the traveling wind itself is difficult to obtain. There is a problem that the temperature cannot be reduced.

  Further, in the construction machine, the exhaust system of the engine which is an internal combustion engine is almost entirely contained in the engine room including the NOx selective reduction catalyst, and the supply pipe and the return pipe are also piped in the engine room. The temperature of the supply pipe and the return pipe tends to be higher than that of other traveling vehicles. For this reason, if a cooling device is formed by a part of such a supply pipe or a return pipe, the cooling device is also arranged in the engine room, and in a situation where traveling wind is difficult to obtain, the cooling device is further cooled. There is a problem that it becomes difficult.

  An object of the present invention is to provide a urea water cooling system for exhaust gas purification that can cool urea water well.

  The cooling system for purifying exhaust gas according to the first invention is provided with a urea water cooling circuit independent of the engine cooling circuit of the engine, and the urea water cooling circuit supplies urea water from a urea water tank. A cooling tube for cooling the urea water supply tube supplied to the valve; a pump for supplying cooling water to the cooling tube; and a radiator into which cooling water flowing out from the cooling tube flows in. The cooling water is configured to circulate back to the pump.

  In the urea water cooling system for exhaust gas purification according to the second invention, the urea water cooling circuit exchanges heat between the engine cooling water from the engine cooling circuit and the cooling water in the urea water cooling circuit. And a flow path switching means for switching between a flow of cooling water to the heat exchanger and a flow to the radiator.

In the exhaust gas purification urea water cooling system according to the third aspect of the present invention, the flow path switching means is a thermo valve.
In the cooling system for urea water for exhaust gas purification according to the fourth aspect of the invention, the flow path switching means is an electromagnetic valve, the cooling water temperature detecting means provided in the flow path upstream of the electromagnetic valve, and the cooling And a control device that outputs a flow path switching signal to the previous electromagnetic valve based on a detection signal from the water temperature detection means.

  In the urea water cooling system for exhaust gas purification according to a fifth aspect of the invention, the cooling tube includes an inflow portion and an outflow portion of cooling water provided corresponding to one end side of the urea water supply tube, and the urea water supply. And a folded portion provided corresponding to the other end of the tube, and is disposed along the urea water supply tube.

  In the urea water cooling system for exhaust gas purification according to the sixth aspect of the present invention, the folding portion is disposed in the urea water supply valve.

  In the urea water cooling system for exhaust gas purification according to the seventh aspect of the present invention, the cooling tube includes a cooling water inflow portion provided corresponding to one end side of the urea water supply tube, and the urea water supply tube. And a cooling water outflow portion provided corresponding to the end side, and a double pipe structure that covers the urea water supply tube is formed.

  In the urea water cooling system for exhaust gas purification according to the eighth aspect of the invention, the cooling tube includes a cooling water inflow portion provided corresponding to one end of the urea water supply tube, and the urea water supply tube. It has a cooling water outflow portion provided corresponding to the end side, and is arranged so as to follow the urea water supply tube.

  According to the first aspect of the invention, the dedicated urea water cooling circuit for forcibly cooling the urea water supply tube with the cooling water is provided. Therefore, the urea water supply tube is disposed in the engine room, and it is difficult to obtain traveling wind. Even in the case of a construction machine, the urea water can be cooled well and the exhaust gas can be purified reliably.

  According to the second invention, the urea water cooling circuit is provided with a heat exchanger for exchanging heat between the engine cooling water and the cooling water for cooling the urea water, and the flow of the cooling water to the radiator and the heat exchanger In the environment where urea water may be frozen, the flow path switching means causes the cooling water to flow to the heat exchanger, and the cooling water and the high-temperature engine cooling water are provided. It is only necessary to exchange heat between the two, and the urea water can be warmed by the cooling water whose temperature has risen, and freezing of the urea water can be prevented.

According to the third invention, since the thermo valve is used as the flow path switching means, the configuration is simple and the reliability and durability can be improved.
According to the fourth invention, the electromagnetic valve is used as the flow path switching means, and the control device performs the flow path switching control by the electromagnetic valve based on the detection signal from the cooling water temperature detection means. The set temperature can be easily implemented by changing the software, etc., and even if the change temperature of the urea water to ammonia or the freezing temperature varies over time, and the deviation from the relationship with the cooling water temperature occurs, the switch set temperature can be set. By changing, it can be easily handled, and the alteration and freezing of urea water can be more reliably prevented.

  According to the fifth aspect of the present invention, the cooling tube is folded and used at the folded portion, so that the cooling water inflow portion and the outflow portion in the cooling tube are concentrated on one end side of the urea water supply tube. It is not necessary to extend the flow path to the other end side of the urea water supply tube, and the cooling tube can be easily handled.

  According to the sixth aspect of the invention, the urea water supply valve can be cooled by the cooling water using the urea water cooling circuit, and the urea water supplied into the urea water supply valve is used as the cooling water of the urea water cooling circuit. Can be cooled.

  According to the seventh invention, the urea water supply tube is an inner tube and the cooling tube is an outer tube, and a double tube structure is formed. The cooling water in the cooling tube is brought into direct contact with the outer surface of the urea water supply tube, and urea water is supplied. Cooling can be performed efficiently.

   According to the eighth invention, the object of the present invention can be achieved while simplifying the structure. Further, depending on the total number of urea water supply tubes and cooling tubes, the arrangement position of each tube when the cooling tubes are arranged around the urea water supply tube can be stabilized.

The figure which shows the urea water cooling circuit of the cooling system which concerns on 1st Embodiment of this invention. Sectional drawing which shows the principal part of the said cooling circuit. Sectional drawing in another angle of the said principal part. The figure which shows the urea water cooling circuit of the cooling system which concerns on 2nd Embodiment of this invention. The figure which shows the urea water cooling circuit of the cooling system which concerns on 3rd Embodiment of this invention. Sectional drawing which shows the principal part of the cooling circuit of 3rd Embodiment before.

[First Embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. In the second, third, and fourth embodiments to be described later, the same members as those in the first embodiment described below are denoted by the same reference numerals, and the descriptions in the second, third, and fourth embodiments are given. Is omitted or simplified.
FIG. 1 is a diagram illustrating a urea water cooling circuit 11 of a cooling system 10 according to the present embodiment. In FIG. 1, a cooling system 10 is a system that cools urea water supplied to an exhaust gas purification device mounted on a construction machine.

Here, examples of the construction machine include a hydraulic excavator, a wheel loader, a bulldozer, a dump truck, and a motor grader.
As an exhaust gas purification device, an upstream purification device incorporating a soot filter that collects particulates in exhaust gas and a downstream side using a urea denitration catalyst (a type of SCR) made of a base metal such as zeolite or vanadium. It consists of a purification device. A downstream purification device is disposed downstream of the upstream purification device. These purification apparatuses are provided in the middle of the exhaust pipe from the engine mounted on the construction machine. The upstream side and the downstream side are the upstream side and the downstream side in the exhaust gas flow direction.

  Of these, the downstream purification apparatus includes the urea water supply unit 1 shown in FIG. 1. The urea water supply unit 1 sucks the urea water stored in the urea water tank 2 by the urea water pump 3 constituting the supply module, and supplies it to the urea water supply valve 5 constituting the dosing module through the urea water supply tube 4. To do.

  The urea water supply valve 5 is configured to eject urea water into the exhaust pipe. The jetted urea water is hydrolyzed to ammonia, and acts as a reducing agent in the urea denitration catalyst. That is, ammonia obtained from urea water is reacted with NOx in the exhaust gas using a reducing agent, and NOx is decomposed into nitrogen and oxygen for purification.

  The urea water cooling circuit 11 of the cooling system 10 cools such urea water. This urea water cooling circuit 11 is independent of the engine cooling circuit 7 of the engine 6. For this reason, in the urea water cooling circuit 11, cooling water of another system that does not join or divert is used for the engine cooling water that cools the engine 6.

  Specifically, the urea water cooling circuit 11 includes a cooling tube 20 that covers the urea water supply tube 4 over most of its entire length, an electric pump 30 that supplies cooling water to the cooling tube 20 via a flow path 31, A radiator 40 in which cooling water flowing out from the cooling tube 20 flows through the flow path 21, a thermo valve 50 as flow path switching means provided in the flow path 21, and cooling water from the thermo valve 50 to the upstream side of the electric pump 30. And a heat exchanger 60 provided in the bypass flow path 51 returning to the side, and the cooling water flowing out from the radiator 40 and the heat exchanger 60 is sucked by the electric pump 30 through the flow path 41 and circulated. ing.

  That is, according to the urea water cooling circuit 11, the urea water flowing in the urea water supply tube 4 is forcibly cooled by the cooling water flowing in the cooling tube 20 on the outer side. As the urea water supply tube 4 passes through the engine room, the temperature of the urea water increases. The urea water changes to ammonia from above 70 ° C., which adversely affects the performance and durability of the equipment such as the urea water supply valve 5. For this reason, the urea water having a high temperature is cooled by cooling water from the outside of the urea water supply tube 4 so as not to exceed 70 ° C. Since the temperature of the cooling water used for cooling the urea water becomes higher due to heat received from the urea water, the cooling water is sent from the cooling tube 20 to the radiator 40 to radiate heat, and returns to the electric pump 30.

  On the other hand, urea water freezes around -11 ° C. In an environment where the urea water may freeze, it is necessary to heat the cooling water to increase the temperature and to supply the cooling water having a high temperature to the cooling tube 20 to prevent the urea water from freezing. For this purpose, high-temperature engine cooling water is supplied from the engine 6 to the heat exchanger 60 of the urea water cooling circuit 11, and the cooling water supplied to the cooling tube 20 is warmed by the engine cooling water to freeze the urea water. Set to a temperature that does not. Further, the urea water may freeze while the engine is stopped. Even in this case, it is possible to start the engine, warm the cooling water supplied to the cooling tube 20 with the warmed engine cooling water, and defrost the urea water. In addition, since the engine cooling water to the heat exchanger 60 is not mixed with the cooling water circulating in the urea water cooling circuit 11, the independence of the urea water cooling circuit 11 from the engine cooling circuit 7 is maintained.

  Such heat radiation in the radiator 40 or heating in the heat exchanger 60 is performed by switching the flow of the cooling water from the cooling tube 20 in the thermo valve 50. The switching set temperature in the thermo valve 50 is set after being converted into the cooling water temperature based on the freezing temperature of the urea water. When the cooling water is below the switching set temperature, the thermo valve 50 shuts off the flow path 21 and opens the bypass flow path 51, causing the cooling water from the cooling tube 20 to flow to the heat exchanger 60, and in the heat exchanger 60. Heat. When the cooling water exceeds the switching set temperature, the bypass flow path 51 is blocked and the flow path 21 is communicated, and the heat of the cooling water is radiated by the radiator 40.

  At this time, the radiator 40 has a normal radiator structure, and a part of cooling air from an engine cooling fan (not shown) is supplied to the radiator 40. The electric pump 30 is generally used to pump cooling water, and detailed description thereof is omitted here. The thermo valve 50 and the heat exchanger 60 are also frequently used in other cooling circuits, and detailed description thereof is omitted here.

Below, the cooling tube 20 is demonstrated in detail.
In FIG. 1, the cooling water inflow portion 20 </ b> A and the outflow portion 20 </ b> B in the cooling tube 20 are provided at positions corresponding to the proximal end side (agrees with the upstream side) of the urea water supply tube 4. That is, in the cooling tube 20, the cooling water flows in and out in the vicinity of the proximal end side of the urea water supply tube 4, and the cooling water is cooled at a position corresponding to the distal end side (agrees with the downstream side) of the urea water supply tube 4. The water turns and flows. The inflow portion 20A and the outflow portion 20B may be provided one by one for the plurality of cooling tubes 20, or may be provided for each cooling tube 20.

  2 and 3 are sectional views of the cooling tube 20 in a state of covering the urea water supply tube 4. 2 and 3, the urea water supply tube 4 and the cooling tube 20 are realized by using a multiple tube 70 in which six tubes are arranged outside the center one. In the multiple tube 70, the urea water supply tube 4 is formed by a single central tube, and the cooling tube 20 is formed by three tubes arranged so as to follow the outside.

  Each of the three cooling tubes 20 includes a cooling water supply tube 22 having one end connected to the inflow portion 20A and a cooling water return tube 23 having one end connected to the outflow portion 20B. The sides are continuous at the folded portion 20C. As a result, six tubes appear around the urea water supply tube 4 in a cross-sectional view of the multiple tube 70.

  When six tubes are arranged around the urea water supply tube 4, the cross-sectional shape is not easily deformed when the whole is covered with the coating 71, and the positions of the tubes are stabilized in a state where they are in contact with each other. Therefore, the urea water supply tube 4 is well surrounded by the cooling tube 20, and the urea water can be efficiently cooled. Further, in such six tubes, the cooling water supply tubes 22 and the cooling water return tubes 23 are alternately arranged in the circumferential direction.

  In the first embodiment, the folded portion 20 </ b> C is provided at the end of the urea water supply tube 4, but may be disposed on the outer periphery of the urea water supply valve 5. Moreover, you may comprise so that the inside of the urea water supply valve 5 may pass. Thereby, not only the urea water is cooled with the cooling water, but also the urea water supply valve 5 can be simultaneously cooled.

  According to the cooling system 10 of the first embodiment described above, the dedicated urea water cooling circuit 11 for forcibly cooling the urea water supply tube 4 with the cooling water is provided. Even in the case of a construction machine that is arranged in a room or where it is difficult to obtain traveling wind, the urea water can be cooled well, and the exhaust gas can be reliably purified.

[Second Embodiment]
FIG. 4 shows a second embodiment of the present invention.
In the first embodiment, the thermo valve 50 (FIG. 1) is provided in the flow path 21, but in the second embodiment, an electromagnetic valve 80 as a flow path switching means is provided. Furthermore, a cooling water temperature detecting means 81 such as a temperature sensor is provided in the flow path 21 upstream of the electromagnetic valve 80. The flow path switching by the electromagnetic valve 80 is controlled by the control device 90 based on the detection signal of the cooling water temperature detecting means 81. For this reason, the detection signal output from the coolant temperature detection means 81 is input to the control device 90, and the flow path switching signal output from the control device 90 is input to the electromagnetic valve 80. Other configurations are the same as those of the first embodiment.

  According to such a configuration, when the control device 90 determines that heating of the cooling water is necessary based on the detection signal from the cooling water temperature detection means 81, the control device 90 sends a flow path switching signal to the electromagnetic valve 80. And the flow path 21 is shut off so that the cooling water flows to the heat exchanger 60. Thereby, freezing of urea water is prevented. On the other hand, when the control device 90 determines that the cooling water needs to be radiated, the control device 90 outputs a flow path switching signal to the electromagnetic valve 80, shuts off the bypass flow path 51, and supplies the cooling water to the radiator 40. Control to flow. Thereby, the urea water is cooled.

  In the present embodiment, the same effects as those of the first embodiment can be obtained, and the flow switching control by the electromagnetic valve 80 is performed by the control device 90. Therefore, it is easy to change the switching set temperature by changing the software or the like. Can be. For this reason, even if there is a variation in the transformation temperature or freezing temperature of urea water to ammonia, and there is a deviation in the relationship with the cooling water temperature, it can be easily handled by changing the switching set temperature, And freezing can be reliably prevented. In addition, depending on the resolution of the cooling water temperature detection means 81, the switching control can be performed more precisely than the thermo valve 50.

[Third Embodiment]
5 and 6 show a third embodiment of the present invention.
In the first embodiment, three cooling tubes 20 are used as the multiple tube 70, and each is folded back on the urea water supply valve 5 side. However, in the third embodiment, urea water is used as the double tube 100. One cooling tube 20 covering the supply tube 4 is used and has a double tube structure. Accordingly, there is no folded portion 20C (FIG. 3) as in the first embodiment, and the cooling tube 20 is provided with an inflow portion 20A at a position corresponding to the distal end side of the urea water supply tube 4, and the urea water supply tube Outflow portion 20B is provided at a position corresponding to the base end side of 4. That is, the inflow portion 20 </ b> A and the outflow portion 20 </ b> B are provided separately on one end side and the other end side of the cooling tube 20. Other configurations are the same as those of the first embodiment.

Although not shown in the drawings, in the inflow portion 20A and the outflow portion 20B, the flow paths 21 and 31 and the cooling tube 20 are communicated with each other through a joint inserted through the urea water supply tube 4. And the cooling water supplied through the flow path 31 flows in into the cooling tube 20 through the joint in 20 A of inflow parts, and flows the outer side of the urea water supply tube 4 toward the base end side. The cooling water that has flowed outside the urea water supply tube 4 flows out into the flow path 21 via a joint at the outflow portion 20B.
Also in this embodiment, urea water can be cooled well and the object of the present invention can be achieved.

[Fourth Embodiment]
In the third embodiment, the double tube 100 (FIGS. 5 and 6) is used. However, in the fourth embodiment, one cooling tube is disposed so as to follow the urea water cooling tube. In the present embodiment, it is possible to achieve a simpler configuration as compared with other embodiments while achieving the object of the present invention. According to this embodiment, the cross section of each tube may be a normal circle or a semicircle. In the case of a semicircular shape, the respective flat surface portions are arranged in contact with each other to form a circular cross-sectional shape as a whole, thereby increasing the contact area with each other and improving the cooling and heating effects.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the first embodiment, by using the three cooling tubes 20 in a folded manner, the multiple tubes 70 have a structure in which six tubes appear around the central urea water supply tube 4 as a cross section of the multiple tube 70. This is also for stabilizing the arrangement position of each tube, but similarly, the structure for stabilizing the arrangement position may be a structure in which two tubes appear with respect to the urea water supply tube 4. In such a case, one cooling water supply tube and one cooling water return tube are attached to the urea water supply tube. As a result, the cross section becomes a substantially triangular shape, and the arrangement position can be stabilized.

  In the fourth embodiment, one cooling tube is arranged so as to follow one urea water supply tube, but a plurality of cooling tubes are arranged on one end side of the urea water supply tube. The urea water supply tube may be arranged so as to be branched, and a plurality of cooling tubes may be joined at the other end side of the urea water supply tube. As a result, the cross section can be made substantially triangular or as shown in FIG. 2, and the arrangement position can be stabilized.

  In the first and second embodiments, the inflow portion 20A and the outflow portion 20B of the cooling tube 20 are provided at positions corresponding to the proximal end side of the urea water supply tube 4, and the turned-up portion 20C is at a position corresponding to the distal end side. However, on the contrary, the inflow portion and the outflow portion of the cooling tube may be provided at a position corresponding to the distal end side of the urea water supply tube, and the folded portion may be provided at a position corresponding to the distal end side.

  In the third and fourth embodiments, the inflow portion 20A of the cooling tube 20 is provided at a position corresponding to the distal end side of the urea water supply tube 4, and the outflow portion 20B is provided at a position corresponding to the proximal end side. However, on the contrary, the inflow portion of the cooling tube may be provided at a position corresponding to the proximal end side of the urea water supply tube, and the outflow portion may be provided at a position corresponding to the distal end side. However, since the temperature of the urea water is expected to increase as it approaches the urea water supply valve 5, the cooling water at a lower temperature is supplied to the urea water supply tube 4 as in the third and fourth embodiments. It is preferable to flow from the tip side.

In each of the above embodiments, the electric pump 30 is used as the pump according to the present invention. However, the electric pump 30 is not limited to electric, and may be a hydraulic pump or a mechanical pump that partially uses the output of the engine.
In each of the above-described embodiments, the flow path switching means such as the thermo valve 50 and the electromagnetic valve 80 and the heat exchanger 60 are provided. However, these may be provided when there is a possibility that the urea water is frozen. If it is not, it can be omitted.

  The present invention is particularly difficult to obtain a traveling wind, and can be suitably used for a construction machine in which an exhaust gas purifying device is housed in an engine room. In addition, a traveling vehicle such as a transportation truck or an internal combustion engine such as a diesel engine is used. It can also be used for stationary generators.

  2 ... urea water tank, 4 ... urea water supply tube, 5 ... urea water supply valve, 7 ... engine cooling circuit, 10 ... cooling system, 11 ... urea water cooling circuit, 20 ... cooling tube, 20A ... inflow part, 20B ... Outflow part, 20C ... turn-up part, 21 ... flow path, 30 ... electric pump as a pump, 40 ... radiator, 50 ... thermo valve as flow path switching means, 60 ... heat exchanger, 80 ... flow path switching means A certain electromagnetic valve, 81 ... cooling water temperature detecting means, 90 ... control device.

Claims (8)

A cooling system for urea water for exhaust gas purification,
A urea water cooling circuit independent of the engine cooling circuit of the engine is provided,
The urea water cooling circuit is
A cooling tube for cooling the urea water supply tube for supplying urea water from the urea water tank to the urea water supply valve;
A pump for supplying cooling water to the cooling tube;
A radiator into which cooling water flowing out of the cooling tube flows,
A cooling system for exhaust gas purification urea water, wherein the cooling water flowing out from the radiator is circulated back to the pump. The cooling system for urea water for exhaust gas purification according to claim 1,
The urea water cooling circuit is
A heat exchanger for exchanging heat between the engine cooling water from the engine cooling circuit and the cooling water in the urea water cooling circuit;
A cooling system for urea water for exhaust gas purification, characterized by comprising a flow path switching means for switching between a flow of cooling water to the heat exchanger and a flow to the radiator. The cooling system for urea water for exhaust gas purification according to claim 2,
The flow path switching means is a thermo valve. A cooling system for urea water for exhaust gas purification, wherein: The cooling system for urea water for exhaust gas purification according to claim 2,
The flow path switching means is an electromagnetic valve,
A coolant temperature detecting means provided in a flow path upstream of the electromagnetic valve;
A urea water cooling system for purifying exhaust gas, comprising: a control device that outputs a flow path switching signal to the electromagnetic valve based on a detection signal from the cooling water temperature detecting means. In the cooling system for urea water for exhaust gas purification according to any one of claims 1 to 4,
The cooling tube is
A cooling water inflow portion and an outflow portion provided corresponding to one end side of the urea water supply tube;
And having a folded portion provided corresponding to the other end side of the urea water supply tube,
A urea water cooling system for purifying exhaust gas, which is disposed along the urea water supply tube. In the cooling system of urea water for exhaust gas purification according to claim 5,
The said folding | returning part is arrange | positioned at the said urea water supply valve. The urea water cooling system for exhaust gas purification characterized by the above-mentioned. In the cooling system for urea water for exhaust gas purification according to any one of claims 1 to 4,
The cooling tube is
A cooling water inflow portion provided corresponding to one end of the urea water supply tube;
A cooling water outlet provided corresponding to the other end of the urea water supply tube, and
A dual pipe structure that covers the urea water supply tube is formed. A cooling system for urea water for purifying exhaust gas, wherein: In the cooling system for urea water for exhaust gas purification according to any one of claims 1 to 4,
The cooling tube is
A cooling water inflow portion provided corresponding to one end of the urea water supply tube;
A cooling water outlet provided corresponding to the other end of the urea water supply tube, and
A urea water cooling system for exhaust gas purification, which is disposed so as to follow the urea water supply tube.

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