JP6440790B2 - Exhaust gas aftertreatment unit and work vehicle - Google Patents

Description

  The present invention relates to an exhaust gas aftertreatment unit and a work vehicle.

  Conventionally, a work vehicle is provided with an exhaust gas aftertreatment unit for purifying nitrogen oxides contained in exhaust gas from a diesel engine (see, for example, Patent Document 1). The exhaust gas aftertreatment unit includes a selective catalyst reduction device, a reducing agent injection device, and a cooling water path. The selective catalyst reduction device reduces nitrogen oxides in the exhaust gas. The reducing agent injection device injects the reducing agent into the exhaust gas flowing into the selective catalyst reduction device. The cooling water path supplies cooling water for cooling the reducing agent injection device heated by the engine and the exhaust gas to the reducing agent injection device.

  Here, Patent Document 1 proposes to provide a cooling water path with a convection portion extending upward from the reducing agent injection device for the purpose of cooling the reducing agent injection device after the engine is stopped.

Japanese Patent No. 5546694

  However, after the engine is stopped, steam may be generated from the cooling water heated by the high-temperature reducing agent injection device, and air may be mixed in the cooling water path. In this case, since the replenishment of the cooling water to the reducing agent injection device is suppressed, there is a possibility that the reducing agent injection device cannot be efficiently cooled.

  The present invention has been made in view of the above situation, and an object thereof is to provide an exhaust gas aftertreatment unit and a work vehicle capable of improving the replenishability of cooling water to the reducing agent injection device. .

  The exhaust gas aftertreatment unit according to the first aspect of the present invention includes a selective catalyst reduction device, a connection pipe, a reducing agent injection device, and a cooling water path. The selective catalyst reduction device processes exhaust gas from the engine. The connecting pipe guides exhaust gas from the engine to the selective catalytic reduction device. The reducing agent injection device is installed in the connection pipe and injects the reducing agent into the exhaust gas supplied to the selective catalyst reduction device. The cooling water path guides cooling water for cooling the reducing agent injection device to the reducing agent injection device. The reducing agent injection device has an internal flow path for flowing cooling water. The cooling water path includes a first flow path that communicates with the internal flow path of the reducing agent injection device, and a second flow path and a third flow path that branch from the first flow path. The branch point where the first flow path branches into the second flow path and the third flow path is located above the connection portion between the reducing agent injection device and the first flow path. The third flow path extends above the second flow path from the branch point. The second flow path and the third flow path merge on the opposite side of the branch point.

  According to the exhaust gas aftertreatment unit according to the first aspect of the present invention, after the engine is stopped, water vapor generated in the internal flow path of the reducing agent injection device is discharged from the first flow path to the third flow path. Therefore, it is possible to suppress water vapor from staying in the internal flow path or the first flow path of the reducing agent injection device. As a result, since the cooling water can be smoothly supplied from the second flow path to the internal flow path of the reducing agent injection device via the first flow path, the replenishability of the cooling water to the reducing agent injection device is improved. can do.

  The exhaust gas aftertreatment unit according to the second aspect of the present invention relates to the first aspect, and the cooling water passage has a tank for temporarily storing the cooling water. Each of the second flow path and the third flow path is connected to a tank.

  According to the exhaust gas aftertreatment unit according to the second aspect of the present invention, the cooling water stored in the tank while the engine is being driven can be supplied to the reducing agent injection device after the engine is stopped. Therefore, the amount of cooling water supplied to the reducing agent injection device after the engine is stopped can be increased.

  The exhaust gas aftertreatment unit according to the third aspect of the present invention relates to the second aspect, and the second flow path extends upward from the branch point.

  According to the exhaust gas aftertreatment unit according to the third aspect of the present invention, the cooling water stored in the tank can be smoothly flowed from the second flow path to the first flow path by its own weight.

  The exhaust gas aftertreatment unit according to the fourth aspect of the present invention relates to the second or third aspect, and the third flow path is connected to the tank above the second flow path.

  According to the exhaust gas aftertreatment unit according to the fourth aspect of the present invention, the cooling water is discharged from the tank to the second flow while the water vapor generated in the internal flow path of the reducing agent injection device is discharged from the third flow path to the tank. Can be drained to the road. Therefore, it is possible to smoothly flow out the cooling water from the second flow path while suppressing the back flow of the cooling water to the third flow path.

  The exhaust gas aftertreatment unit according to the fifth aspect of the present invention relates to the second to fourth aspects, and the cooling water path has a fourth flow path connected to the tank and the cooling water pump. The fourth flow path is connected to the tank above the center of the tank in the vertical direction.

  According to the exhaust gas aftertreatment unit according to the fifth aspect of the present invention, more cooling water can be stored in the tank than in the case where the fourth flow path is connected below the center of the tank. .

  The exhaust gas aftertreatment unit according to the sixth aspect of the present invention relates to the first to fifth aspects, and the first flow path is shorter than the third flow path.

  According to the exhaust gas aftertreatment unit according to the sixth aspect of the present invention, the flow path length of the first flow path can be made relatively short, so that the water vapor generated in the internal flow path of the reducing agent injection device is supplied to the third flow path. It can be discharged smoothly from the road.

  The exhaust gas aftertreatment unit according to the seventh aspect of the present invention relates to the first to sixth aspects, and the second flow path is thicker than the third flow path.

  According to the exhaust gas aftertreatment unit according to the seventh aspect of the present invention, the amount of cooling water remaining in the second flow path when the engine is stopped can be increased. The amount of cooling water supplied to can be increased.

  A work vehicle according to an eighth aspect of the present invention includes a work machine, an engine, and an exhaust gas aftertreatment unit according to any one of the first to seventh aspects.

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas aftertreatment unit and work vehicle which can improve the replenishment property of the cooling water to a reducing agent injection apparatus can be provided.

Side view of excavator Perspective view of exhaust gas aftertreatment unit Perspective view of exhaust gas aftertreatment unit Perspective view of reducing agent injection device Perspective view of branch block Schematic diagram for explaining the supply of cooling water to the reducing agent injection device during driving of the engine Schematic diagram for explaining the supply of cooling water to the reducing agent injection device after the engine is stopped Schematic diagram showing another form of cooling water path

(Configuration of hydraulic excavator 100)
FIG. 1 is a side view of the excavator 100. In the following description, “front”, “rear”, “left”, and “right” indicate directions with reference to the state of looking forward from the driver's seat. “Vehicle width direction” is synonymous with “left-right direction”.

  The excavator 100 is an example of a work vehicle according to the present embodiment. The excavator 100 includes a vehicle main body 1 and a work machine 4.

  The vehicle body 1 includes a traveling body 2 and a turning body 3. The traveling body 2 is driven by the power of the engine 10. The swivel body 3 is placed on the traveling body 2. The turning body 3 can turn with respect to the traveling body 2.

  The swivel body 3 includes a cab 5, an equipment room 6, an engine room 7 and a counterweight 8. The cab 5 is disposed on the left side of the base end portion of the work machine 4. The equipment room 6 is arranged behind the cab 5. The equipment chamber 6 accommodates a fuel tank and a hydraulic oil tank. The engine room 7 is disposed behind the equipment room 6. The engine chamber 7 houses an engine 10, an exhaust gas aftertreatment unit 20, a radiator 12 (see FIG. 6), which will be described later, and the like. In the present embodiment, the exhaust gas aftertreatment unit 20 is disposed above the engine 10. An engine hood 9 is disposed above the engine chamber 7. The counterweight 8 is disposed behind the engine compartment 7.

  The work machine 4 is attached to the front part of the revolving unit 3. The work machine 4 includes a boom 4a, an arm 4b, and a bucket 4c. The work machine 4 is driven by supplying hydraulic oil.

(Configuration of exhaust gas aftertreatment unit 20)
FIG. 2 is a perspective view of the exhaust gas aftertreatment unit 20 as viewed from the diagonally left rear. FIG. 3 is a perspective view of the exhaust gas aftertreatment unit 20 as viewed from the right rear side. 2 and 3, the engine hood 9 is removed.

  The exhaust gas aftertreatment unit 20 includes a diesel particulate filter device 21, a selective catalyst reduction device 22, a connection pipe 23, a reducing agent injection device 24, and a cooling water path 25.

  The diesel particulate filter device 21 collects particulate matter contained in the exhaust gas from the engine 10 with a filter. The diesel particulate filter device 21 incinerates the collected particulate matter with a heater attached thereto. Exhaust gas from the engine 10 is introduced into the interior from the front end of the diesel particulate filter device 21. The diesel particulate filter device 21 has a substantially cylindrical outer shape. In the present embodiment, the diesel particulate filter device 21 is disposed along the front-rear direction.

  The selective catalyst reduction device 22 is disposed downstream of the diesel particulate filter device 21. Exhaust gas that has passed through the diesel particulate filter device 21 is introduced into the selective catalyst reduction device 22. The selective catalyst reduction device 22 processes the exhaust gas from the engine 10. Specifically, the selective catalyst reduction device 22 reduces nitrogen oxides in the exhaust gas with ammonia. The selective catalyst reduction device 22 has a substantially cylindrical outer shape. In the present embodiment, the selective catalyst reduction device 22 is disposed along the front-rear direction. An exhaust pipe 26 protruding from the engine hood 9 (see FIG. 1) is connected to the rear end portion of the selective catalyst reduction device 22. The exhaust gas processed by the exhaust gas post-processing unit 20 is discharged to the outside from the exhaust pipe 26.

  The connection pipe 23 connects the diesel particulate filter device 21 and the selective catalyst reduction device 22. The connection pipe 23 guides the exhaust gas that has passed through the diesel particulate filter device 21 to the selective catalyst reduction device 22. The connection pipe 23 is connected to the rear end portion of the diesel particulate filter device 21 and the front end portion of the selective catalyst reduction device 22. The connection pipe 23 is formed in an S shape as a whole.

  The reducing agent injection device 24 is installed in the connection pipe 23. A reducing agent supply pipe 27 is connected to the reducing agent injection device 24. The reducing agent supply pipe 27 supplies urea water (an example of a reducing agent) sent from a urea water tank (not shown) to the reducing agent injection device 24. The reducing agent injection device 24 injects urea water into the exhaust gas supplied to the selective catalyst reduction device 22. The urea water injected from the reducing agent injection device 24 is hydrolyzed by the heat of the exhaust gas to become ammonia. Ammonia generated in the connection pipe 23 is introduced into the selective catalyst reduction device 22 together with the exhaust gas.

  Here, FIG. 4 is a perspective view showing the configuration of the reducing agent injection device 24. The reducing agent injection device 24 includes a main body portion 70, a first injection device connection portion 71, and a second injection device connection portion 72. A reducing agent supply pipe 27 is connected to the main body 70. An internal flow path 24 a is formed inside the main body 70. The internal flow path 24 a communicates with the first injection device connection portion 71 and the second injection device connection portion 72. A first piping 31 described later is connected to the first injection device connection portion 71. A fifth pipe 35 described later is connected to the second injection device connection portion 72.

  The reducing agent injection device 24 is heated by the radiant heat of the engine 10 and the high-temperature exhaust gas flowing through the connection pipe 23 while the engine 10 is being driven. Further, the reducing agent injection device 24 is heated by the radiant heat of the engine 10 and the high-temperature exhaust gas staying in the connection pipe 23 even after the engine 10 is stopped. While the engine 10 is being driven, the reducing agent injection device 24 is latently cooled by the cooling water supplied from the fifth pipe 35 to the internal flow path 24a. After the engine 10 is stopped, the reducing agent injection device 24 is latently cooled by the cooling water supplied from the first pipe 31 to the internal flow path 24a.

  The cooling water path 25 includes a storage tank 29 (an example of a tank), a branch block 30, a first pipe 31, a second pipe 32, a third pipe 33, a fourth pipe 34, a fifth pipe 35, and a sixth pipe 36. .

  The storage tank 29 is disposed above the diesel particulate filter device 21. The storage tank 29 stores cooling water for cooling the reducing agent injection device 24 while the engine 10 is being driven. After the engine 10 is stopped, the cooling water stored in the storage tank 29 is supplied to the reducing agent injection device 24. The storage of the cooling water in the storage tank 29 and the supply of the cooling water from the storage tank 29 will be described later.

  The storage tank 29 has a main body part 60, a first tank connection part 61, a second tank connection part 62, and a third tank connection part 63. In the present embodiment, the main body 60 is formed in a cylindrical shape. The main body 60 is disposed along the front-rear direction. The first tank connection portion 61 and the second tank connection portion 62 are attached to the rear surface of the main body portion 60. The first tank connection portion 61 is disposed above the second tank connection portion 62. The third tank connection portion 63 is attached to the front surface of the main body portion 60. The third tank connecting portion 63 is disposed above the center of the storage tank 29 in the vertical direction.

  The branch block 30 is disposed above the reducing agent injection device 24. In the present embodiment, the branch block 30 is disposed behind the diesel particulate filter device 21 and above the connection pipe 23. The branch block 30 is fixed to the bracket 38. The bracket 38 is attached to the connection pipe 23.

  Here, FIG. 5 is a perspective view showing the configuration of the branch block 30. The branch block 30 includes a main body portion 40, a first branch connection portion 41, a second branch connection portion 42, a third branch connection portion 43, a fourth connection portion 44, and a fifth connection portion 45.

  The main body 40 includes a first internal channel 40a and a second internal channel 40b.

  The first internal channel 40 a is formed inside the main body 40. The first internal flow path 40a is formed in a trifurcated shape. The first internal flow path 40 a communicates with the first branch connection portion 41, the second branch connection portion 42, and the third branch connection portion 43. In the present embodiment, the first branch connection part 41, the second branch connection part 42, the third branch connection part 43, and the first internal flow path 40a constitute a “branch pipe” that branches in three directions.

  The first internal channel 40 a has a first opening 51, a second opening 52, and a third opening 53. The first opening 51 opens on the left surface of the main body 40. The second opening 52 opens on the front surface of the main body 40. The second opening 52 is located below the third opening 53. In the present embodiment, the second opening 52 is located at the same height as the first opening 51. The third opening 53 opens on the upper surface of the main body 40. The third opening 53 is located above the second opening 52. However, as long as the 3rd opening 53 is located above the 2nd opening 52, the height of each opening can be changed suitably. For example, the third opening 53 may be higher than the second opening 52, and the second opening 52 may be higher than the first opening 51. The third opening 53 may be the same height as the first opening 51, and the second opening 52 may be lower than the first opening 51.

  The second internal channel 40 b is formed inside the main body 40. The second internal channel 40b is located below the first internal channel 40a. The second internal channel 40b is formed in an L shape. The second internal flow path 40 b has a fourth opening 54 and a fifth opening 55. The fourth opening 54 opens on the left surface of the main body 40 below the first opening 51. The fifth opening 55 opens to the front surface of the main body 40 below the second opening 52. In the present embodiment, the fourth opening 54 is positioned at the same height as the fifth opening 55, but the height of each opening can be changed as appropriate. The fifth opening 55 is preferably higher than the fourth opening 54, but may be lower than the fourth opening 54.

  The first branch connection portion 41 is attached to the first opening 51. The first branch connection portion 41 protrudes leftward from the left surface of the main body portion 40. In the present embodiment, the first branch connection portion 41 is disposed at the same height as the second branch connection portion 42.

  The second branch connection portion 42 is attached to the second opening 52. The second branch connection portion 42 protrudes forward from the front surface of the main body portion 40. The second branch connection portion 42 is disposed below the third branch connection portion 43.

  The third branch connection portion 43 is attached to the third opening 53. The third branch connection portion 43 protrudes upward from the upper surface of the main body portion 40. The third branch connection portion 43 is formed in an L shape. The third branch connection portion 43 extends upward from the third opening 53 and is then bent in a substantially horizontal direction. The third branch connection portion 43 is disposed above the second branch connection portion 42.

  However, as long as the 3rd branch connection part 43 is arrange | positioned rather than the 2nd branch connection part 42, the height of the 1st thru | or 3rd branch connection parts 41-43 can be changed suitably. For example, the third branch connection unit 43 may be higher than the second branch connection unit 42, and the second branch connection unit 42 may be higher than the first branch connection unit 41. In addition, the third branch connection portion 43 may be set to the same height as the first branch connection portion 41, and the second branch connection portion 42 may be lower than the first branch connection portion 41.

  The fourth connection portion 44 is attached to the fourth opening 54. The fourth connection portion 44 protrudes leftward from the left surface of the main body portion 40. The fourth connection portion 44 is disposed below the first branch connection portion 41.

  The fifth connection portion 45 is attached to the fifth opening 55. The fifth connecting portion 45 protrudes forward from the front surface of the main body portion 40. In the present embodiment, the fourth connecting portion 44 is disposed at the same height as the fifth connecting portion 45, but the heights of the fourth and fifth connecting portions 44, 45 can be changed as appropriate. The fifth connecting portion 45 is preferably higher than the fourth opening 54, but may be lower than the fourth opening 54.

  One end portion of the first pipe 31 is connected to a first injection device connecting portion 71 of the reducing agent injection device 24 as shown in FIG. The other end of the first pipe 31 is connected to a first branch connection part 41 of the branch block 30 as shown in FIG. The first pipe 31 is connected to the third pipe 33 and the second pipe 32 via the first internal flow path 40a. In the present embodiment, the first pipe 31 is disposed above the fifth pipe 35.

  One end portion of the second pipe 32 is connected to the second tank connection portion 62 of the storage tank 29 as shown in FIG. The other end of the second pipe 32 is connected to the second branch connection portion 42 of the branch block 30 as shown in FIG. The second pipe 32 is disposed below the third pipe 33. In this embodiment, the 2nd piping 32 is arrange | positioned along the front-back direction.

  One end of the third pipe 33 is connected to the first tank connection 61 of the storage tank 29 as shown in FIG. The other end of the third pipe 33 is connected to a third branch connection 43 of the branch block 30 as shown in FIG. The third pipe 33 is disposed above the second pipe 32. In this embodiment, the 3rd piping 33 is arrange | positioned along the front-back direction.

  One end portion of the fourth pipe 34 is connected to the third tank connection portion 63 of the storage tank 29 as shown in FIG. 3. The other end of the fourth pipe 34 is connected to a cooling water pump 11 described later (see FIG. 6). In the present embodiment, the fourth pipe 34 functions as a discharge pipe for discharging the cooling water from the storage tank 29 while the engine 10 is being driven.

  One end of the fifth pipe 35 is connected to the second injection device connecting portion 72 of the reducing agent injection device 24 as shown in FIG. The other end portion of the fifth pipe 35 is connected to the fourth connection portion 44 of the branch block 30 as shown in FIG. The fifth pipe 35 is connected to the sixth pipe 36 via the second internal flow path 40b. In the present embodiment, the fifth pipe 35 is disposed along the lower side of the first pipe 31.

  One end of the sixth pipe 36 is connected to the fifth connection 45 of the branch block 30 as shown in FIG. The other end of the sixth pipe 36 is connected to a cooling water pump 11 described later (see FIG. 6). The sixth pipe 36 is connected to the fifth pipe 35 via the second internal flow path 40b.

(Supply of cooling water to the reducing agent injection device 24)
FIG. 6 is a schematic diagram for explaining the supply of cooling water to the reducing agent injection device 24 while the engine 10 is driven. FIG. 7 is a schematic diagram for explaining supply of cooling water to the reducing agent injection device 24 after the engine 10 is stopped.

  As shown in FIGS. 6 and 7, a cooling water pump 11, a radiator 12, and an EGR (exhaust gas recirculation device) cooler 13 are connected to the engine 10.

  The coolant pump 11 is connected to the crankshaft of the engine 10 and is driven in synchronization with the rotation of the crankshaft. The cooling water pump 11 sends out cooling water while the engine 10 is being driven. The cooling water pump 11 does not send out the cooling water after the engine 10 is stopped.

  As shown in FIGS. 6 and 7, the cooling water path 25 includes a first flow path F1, a second flow path F2, a third flow path F3, a fourth flow path F4, a fifth flow path F5, a storage tank 29, and It has an internal flow path 24a. The cooling water path 25 guides cooling water for cooling the reducing agent injection device 24 to the reducing agent injection device 24.

  The first flow path F <b> 1 is formed inside the first pipe 31. The second flow path F <b> 2 is formed inside the second pipe 32. The third flow path F <b> 3 is formed inside the third pipe 33. The fourth flow path F4 is formed inside the fourth pipe 34. The fifth flow path F <b> 5 is formed inside the fifth pipe 35 and the sixth pipe 36. The internal flow path 24 a is formed inside the reducing agent injection device 24.

  The first flow path F1 is continuous with the internal flow path 24a. The first flow path F1 extends upward from the internal flow path 24a. The first flow path F1 branches into a second flow path F2 and a third flow path F3 at a branch point FP. The branch point FP is located above the connection portion between the reducing agent injection device 24 and the first flow path F1. The branch point FP is located below the connection portion between the storage tank 29 and the second flow path F2. Accordingly, one end portion of the first flow path F1 provided with the branch point FP is located above the other end portion of the first flow path F1 connected to the internal flow path 24a of the reducing agent injection device 24. In addition, one end portion of the first flow path F1 provided with the branch point FP is positioned below one end portion of the second flow path F2 connected to the storage tank 29. In the present embodiment, the first flow path F1 is shorter than the third flow path F3.

  The second flow path F2 extends upward from the branch point FP. The third flow path F3 extends above the second flow path F2 from the branch point FP. The third flow path F3 extends to the branch point FP from above the second flow path F2. The rising angle from the branch point FP of the second flow path F2 is larger than the rising angle from the branch point FP of the third flow path F3. The rising angle is an angle formed by each flow path with respect to the horizontal line. The second flow path F2 is generally disposed above the third flow path F3, but may be partially disposed below the third flow path F3. In the present embodiment, the second flow path F2 is thicker than the third flow path F3. Therefore, the capacity per unit length in the second flow path F2 is larger than the capacity per unit length in the third flow path F3.

  The second flow path F2 and the third flow path F3 merge on the opposite side of the branch point FP. In the present embodiment, the second flow path F2 and the third flow path F3 merge in the storage tank 29. Each of the second flow path F2 and the third flow path F3 is connected to the storage tank 29. The third flow path F3 is connected to the storage tank 29 above the second flow path F2.

  The fourth flow path F4 is connected to the storage tank 29. The fourth flow path F4 is connected to the storage tank 29 above the center of the storage tank 29 in the vertical direction. In the present embodiment, the fourth flow path F4 is connected to the storage tank 29 above the second flow path F2. The fourth flow path F4 is connected to the storage tank 29 at a position equivalent to the third flow path F3 in the vertical direction. The fourth flow path F <b> 4 is connected to the cooling water pump 11.

  The fifth flow path F5 is continuous with the internal flow path 24a on the opposite side of the first flow path F1. The fifth flow path F <b> 5 is connected to the cooling water pump 11.

  Next, referring to FIG. 6, the supply of cooling water while the engine 10 is being driven will be described.

  Most of the cooling water sent out from the cooling water pump 11 is supplied to a water jacket (not shown) formed in the engine 10 and the EGR cooler 13. The cooling water that has passed through the water jacket of the engine 10 returns to the cooling water pump 11 through the radiator 12. The cooling water that has passed through the EGR cooler 13 returns to the cooling water pump 11.

  The remainder of the cooling water sent out from the cooling water pump 11 is supplied to the internal flow path 24a of the reducing agent injection device 24 through the fifth flow path F5. The reducing agent injection device 24 is cooled by latent heat by the cooling water supplied to the internal flow path 24a. The cooling water that has passed through the internal flow path 24a of the reducing agent injection device 24 flows into the first flow path F1. The cooling water that has flowed into the first flow path F1 is divided into the second flow path F2 and the third flow path F3 at the branch point FP, and then is transferred to the storage tank 29 from each of the second flow path F2 and the third flow path F3. Inflow. Cooling water is gradually stored in the storage tank 29 from the start of driving of the engine 10, and when the storage tank 29 is filled with cooling water, the cooling water flows out from the fourth flow path F4. The cooling water that has flowed out to the fourth flow path F4 returns to the cooling water pump 11.

  Next, the supply of cooling water after the engine 10 is stopped will be described with reference to FIG.

  Since the cooling water pump 11 is stopped together with the engine 10, the cooling water supply from the cooling water pump 11 to the engine 10, the EGR cooler 13, and the reducing agent injection device 24 is also cut off.

  As described above, the storage tank 29 stores cooling water, and the storage tank 29 is disposed above the reducing agent injection device 24 and the branch point FP. Therefore, the cooling water stored in the storage tank 29 tends to flow out from the second flow path F2 due to its own weight.

  On the other hand, since the cooling water left in the internal flow path 24a of the reducing agent injection device 24 is vaporized by latent heat to become water vapor, this water vapor stays in the internal flow path 24a and the first flow path F1 and accumulates air. When this occurs, it becomes difficult for the cooling water to flow out from the storage tank 29 to the second flow path F2.

  Therefore, in the present embodiment, the first flow path F1 is branched into the second flow path F2 and the third flow path F3 at the branch point FP. The water vapor generated in the internal flow path 24a of the reducing agent injection device 24 enters the storage tank 29 from the first flow path F1 through the third flow path F3. As the water vapor is discharged (so-called air bleeding), the cooling water stored in the storage tank 29 smoothly passes through the first flow path F1 from the second flow path F2 and flows into the reducing agent injection device 24. It is supplied to the internal flow path 24a. As a result, the reducing agent injection device 24 is cooled by latent heat even after the engine 10 is stopped by the cooling water supplied to the internal flow path 24a.

(Feature)
(1) The exhaust gas aftertreatment unit 20 includes a cooling water path 25 that guides cooling water for cooling the reducing agent injection device 24 to the reducing agent injection device 24. The cooling water path 25 includes a first flow path F1 connected to the internal flow path 24a of the reducing agent injection device 24, and a second flow path F2 and a third flow path F3 branched from the first flow path F1. A branch point FP where the first flow path F1 branches into the second flow path F2 and the third flow path F3 is located above the reducing agent injection device 24. The third flow path F3 extends above the second flow path F2 from the branch point FP.

  Therefore, after the engine 10 is stopped, water vapor generated in the internal flow path 24a of the reducing agent injection device 24 is discharged from the first flow path F1 to the third flow path F3. It can suppress that water vapor | steam retains in 24a and the 1st flow path F1. As a result, since the cooling water can be smoothly supplied from the second flow path F2 to the internal flow path 24a of the reducing agent injection device 24 through the first flow path F1, the cooling water to the reducing agent injection device 24 is supplied. The replenishability of can be improved.

  (2) Each of the second flow path F2 and the third flow path F3 is connected to the storage tank 29.

  Therefore, the cooling water stored in the storage tank 29 during the driving of the engine 10 can be supplied to the reducing agent injection device 24 after the engine 10 is stopped. Therefore, the amount of cooling water supplied to the reducing agent injection device 24 after the engine 10 is stopped can be increased.

  (3) The second flow path F2 extends upward from the branch point FP. Therefore, after the engine 10 is stopped, the cooling water stored in the storage tank 29 can flow smoothly from the second flow path F2 to the first flow path F1 due to its own weight.

  (4) The third flow path F3 is connected to the storage tank 29 above the second flow path F2.

  Therefore, the cooling water can flow out from the storage tank 29 to the second flow path F2 while releasing the water vapor generated in the internal flow path 24a of the reducing agent injection device 24 from the third flow path F3 to the storage tank 29. Therefore, it is possible to smoothly flow out the cooling water from the second flow path F2 while suppressing the back flow of the cooling water to the third flow path F3.

  (5) The fourth flow path F4 is connected to the storage tank 29 above the center of the storage tank 29 in the vertical direction.

  Therefore, more cooling water can be stored in the storage tank 29 than when the fourth flow path F <b> 4 is connected below the center of the storage tank 29.

  (6) The first flow path F1 is shorter than the third flow path F3. Therefore, since the flow path length of the first flow path F1 can be relatively shortened, water vapor generated in the internal flow path 24a of the reducing agent injection device 24 can be smoothly discharged from the third flow path F3.

  (7) The second flow path F2 is thicker than the third flow path F3. Therefore, since the amount of the cooling water remaining in the second flow path F2 can be increased when the engine 10 is stopped, the amount of the cooling water supplied to the reducing agent injection device 24 is increased after the engine 10 is stopped. Can do.

(Other embodiments)
In the above embodiment, the branch block 30 is used to constitute a “branch pipe” including the first branch connection part 41, the second branch connection part 42, the third branch connection part 43, and the first internal flow path 40a. However, it is not limited to this. As the “branch pipe”, a known three-way branch pipe can be used.

  In the above embodiment, the first internal flow path 40a and the second internal flow path 40b are formed inside the branch block 30, but the present invention is not limited to this. Only the first internal flow path 40 a may be formed inside the branch block 30. In this case, a single pipe including the fifth pipe 35 and the sixth pipe 36 may be used. Further, only the second internal flow path 40 b may be formed inside the branch block 30. In this case, a three-way branch pipe to which the first to third pipes 31 to 33 are connected may be used separately.

  In the above embodiment, the cooling water path 25 includes the storage tank 29, but as illustrated in FIG. 8, it does not need to include the storage tank 29. In this case, the reducing agent injection device 24 is cooled using the cooling water remaining inside the second flow path F2 and the third flow path F3 when the engine 10 is stopped. Even in this case, the water vapor generated in the internal flow path 24a of the reducing agent injection device 24 can be discharged from the first flow path F1 to the third flow path F3.

In the said embodiment, although the exhaust-gas aftertreatment unit 20 was provided with the diesel particulate filter device 21, it is not restricted to this. The exhaust gas aftertreatment unit 20 may include a diesel oxidation catalyst (DOC) instead of the diesel particulate filter device 21. The diesel oxidation catalyst has a function of reducing nitrogen monoxide (NO) among nitrogen oxides (NOx) in exhaust gas and increasing nitrogen dioxide (NO ₂ ).

  In the above embodiment, the third flow path F3 extends above the second flow path F2 from the branch point FP, but the third flow path F3 is partially as high as the second flow path F2. It may be located in the middle or may be located partially higher than the second flow path F2.

4 Work implement 10 Engine 11 Cooling water pump 20 Exhaust gas aftertreatment unit 22 Selective catalyst reduction device 23 Connection pipe 24 Reductant injection device 24a Internal flow path 25 Cooling water path F1 First flow path F2 Second flow path F3 Third flow Path F4 Fourth flow path F5 Fifth flow path 29 Storage tank (an example of a tank)
100 Hydraulic excavator (an example of a work vehicle)

Claims (7)

A reducing agent injection device for injecting a reducing agent into exhaust gas from the engine ;
A cooling water path for guiding cooling water for cooling the reducing agent injection device to the reducing agent injection device;
With
The reducing agent injection device has an internal flow path for flowing cooling water,
The cooling water path is
A first flow path connected to the internal flow path of the reducing agent injection device;
A second flow path and a third flow path branched from the first flow path;
A tank for temporarily storing cooling water;
Including
A branch point where the first flow path branches into the second flow path and the third flow path is located above a connection portion between the reducing agent injection device and the first flow path,
The third flow path extends upward from the branch point than the second flow path,
Each of the second flow path and the third flow path is connected to the tank .
Exhaust gas aftertreatment unit. The first flow path is shorter than the third flow path;
The exhaust gas aftertreatment unit according to claim 1. The second flow path extends upward from the branch point.
The exhaust gas aftertreatment unit according to claim 1 or 2 . The third flow path is connected to the tank above the second flow path,
The exhaust gas aftertreatment unit according to any one of claims 1 to 3 . The cooling water path has a fourth flow path connected to the tank and the cooling water pump,
The fourth flow path is connected to the tank above the center of the tank in the vertical direction.
The exhaust gas aftertreatment unit according to any one of claims 1 to 4 . The second flow path is thicker than the third flow path,
The exhaust gas aftertreatment unit according to any one of claims 1 to 5 . A working machine,
Engine,
The exhaust gas aftertreatment unit according to any one of claims 1 to 6 ,
Work vehicle equipped with.

Images