JP2020051343A - Construction machine - Google Patents

Abstract

To provide a construction machine capable of efficiently thawing frozen urea water in a urea water tank not only at a place around a sensor unit but also at other places away therefrom.SOLUTION: In a sensor unit 28 inserted into a urea water tank 25, a cross-sectional shape of a lower unit section 28B positioned at a lower portion of the sensor unit is larger than the cross-sectional shape of an upper unit section 28C positioned above the lower unit section 28B. That is, a first heating tube 31 of the sensor unit 28 has an enlarged section 31A with a lower portion horizontally extended. The urea water tank 25 has a second heating tube 39 in addition to the first heating tube 31 of the sensor unit 28. The second heating tube 39 is arranged at a position immersed in urea water in the urea water tank 25. The second heating tube 39 heats the urea water in the urea water tank 25 at the position (above the lower unit section 28B) away from the first heating tube 31.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a construction machine such as a hydraulic shovel provided with an exhaust gas purifying device for purifying exhaust gas of an engine, for example.

  2. Description of the Related Art Generally, a hydraulic excavator as a representative example of a construction machine includes a movable vehicle body, an engine provided on the vehicle body, and an exhaust gas purifying device that purifies exhaust gas from the engine. The exhaust gas purifying device is connected to an exhaust pipe of an engine and selectively removes urea to remove nitrogen oxides in exhaust gas, and urea water injection that injects urea water as a liquid reducing agent upstream of the urea selective reduction catalyst. A valve, a urea water tank for storing urea water supplied to the urea water injection valve, and a heating device for heating the urea water in the urea water tank are provided (Patent Documents 1 and 2).

  Here, consider a case where the urea water tank is frozen, that is, a case where the urea water in the urea water tank is frozen. For example, when the heating device is configured by the engine cooling water pipe through which the engine cooling water flows, the frozen urea water starts to melt around the engine cooling water pipe. For this reason, the portion separated from the engine cooling water pipe is hardly melted, and there is a possibility that the thawing performance cannot be sufficiently ensured by this alone.

  On the other hand, Patent Literature 1 discloses a configuration in which urea water in a urea water tank is heated by a movable (rotatable) heating device. According to this configuration, the thawing range can be expanded by moving (rotating) the heating device. On the other hand, Patent Literature 2 discloses a configuration including a second urea water return pipe in addition to the first urea water return pipe. According to this configuration, the urea water thawing range can be expanded by adding the urea water return pipe. In other words, the urea water frozen in the portion remote from the heating device is not only urea water returned from the first urea water return pipe but also urea water returned from the second urea water return pipe. Decompression becomes possible, and the decompression performance can be improved.

JP 2014-190316 A JP-A-2015-148186

  For example, according to the technology described in Patent Document 2, in a urea water tank, a “sensor for managing the quality of urea water”, an “engine cooling water pipe through which engine cooling water flows”, and a “water supply of urea water ( A sensor unit in which a urea water supply pipe for performing suction and a urea water return pipe for discharging urea water is integrated. This sensor unit has a complicated shape in order to increase the thawing area. Specifically, the sensor unit is configured such that, when inserted into the urea water tank, the cross-sectional shape of a portion located on the lower side in the urea water tank is larger than that on the upper side. Therefore, when the sensor unit is removed from the urea water tank, the sensor unit cannot be directly pulled out directly above. Thus, for example, even if the urea water in the urea water tank is thawed from a completely frozen state to a state in which urea water can be supplied (sucked up), only the area around the engine cooling water pipe of the sensor unit is thawed. In the case of the state, the sensor unit may not be able to be pulled out from the urea water tank.

  Furthermore, according to the prior art, the state of thawing in the urea water tank is not known. For this reason, when replacing the sensor unit, the timing at which the sensor unit can be pulled out from the urea water tank is not known, and for example, there is a possibility that it is necessary to wait until the urea water is completely thawed. . That is, according to the prior art, even if the decompression performance is improved, there is a possibility that the extent of decompression cannot be known. For this reason, when pulling out the sensor unit from the urea water tank, it may not be possible to determine whether or not a necessary part has been thawed. In other words, there is a possibility that the thawing state is not known and it is not possible to determine at which point the sensor unit may be removed. For example, when the sensor unit is pulled out of the urea water tank in a state where the thawing is insufficient, not only the frozen urea water mass contacts the sensor unit, but also the inner surface of the urea water tank, the inside of the urea water tank. There is a possibility of contact with other strainers.

  In any case, it is not preferable that the sensor unit is pulled out of the urea water tank in a state where the thawing is performed only around the sensor unit (the state where the thawing is insufficient). In other words, when the urea water is frozen in the urea water tank, it is preferable that the portion separated from the sensor unit can be efficiently thawed.

  An object of the present invention is to provide a construction machine capable of efficiently thawing not only the area around the sensor unit but also the part remote from the sensor unit when the urea water freezes in the urea water tank.

  The construction machine of the present invention includes a urea water tank that stores urea water that is a reducing agent of a urea selective reduction catalyst that removes nitrogen oxides in exhaust gas, and a sensor unit inserted into the urea water tank. The sensor unit is configured to heat the urea water in the urea water tank by circulating engine cooling water disposed in the urea water tank and a urea water supply pipe for sucking up urea water from the urea water tank. A first heating device and a state sensor for detecting a state of the urea water are assembled as an assembly, and a lower side of the urea water tank is inserted in the urea water tank. The cross section of the lower unit of the unit located at the upper part is larger than the cross section of the upper unit of the unit located above the lower unit of the unit. The urea water is disposed at a position immersed in the urea water in the urea water tank separately from the first heating device of the sensor unit, and at a position away from the first heating device. A second heating device for warming the urea water in the tank is provided, and the second heating device is located below the sensor unit and has a larger cross-sectional shape at a lower portion of the unit. It is located above.

  According to the present invention, when the urea water is frozen in the urea water tank, not only the area around the sensor unit but also the part distant from the sensor unit (specifically, above the lower part of the unit) can be efficiently thawed. That is, when the urea water is frozen in the urea water tank, the area around the sensor unit can be thawed by the first heating device, and in addition to the portion distant from the sensor unit (specifically, ) Can also be efficiently thawed by the second heating device. As a result, the removal (pull-out) of the sensor unit from the urea water tank in a state where the thawing is insufficient can be suppressed.

It is a right view which shows the hydraulic shovel by embodiment. It is a top view which shows a top revolving superstructure in the state which omitted a cab, a building cover, etc. FIG. 2 is a circuit diagram illustrating an engine, an exhaust gas purification device, and the like. It is sectional drawing which shows a urea water tank, a sensor unit, an auxiliary heating unit, etc. It is sectional drawing which shows an auxiliary heating unit (a 2nd heating pipe, a float, a stopper, etc.). It is the perspective view which looked at the auxiliary heating unit with the stopper attached from the outside of the urea water tank. FIG. 7 is a perspective view similar to FIG. 6, showing a state where urea water is frozen and a stopper is removed. FIG. 7 is a perspective view similar to FIG. 6 and showing a state in which the float is raised by thawing the urea water. It is a front view which shows the auxiliary heating unit in the state where the stopper was attached. FIG. 10 is a front view similar to FIG. 9, showing a state in which urea water is frozen and a stopper is removed. FIG. 10 is a front view of the same position as in FIG. 9 showing a state in which the float is raised by thawing the urea water. It is a perspective view which cuts and shows an auxiliary heating unit.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings, taking as an example a case where the embodiment is applied to a hydraulic excavator as a representative example of a construction machine.

  In FIG. 1, a hydraulic excavator 1 as a construction machine is configured as a crawler type hydraulic excavator. That is, the hydraulic excavator 1 is mounted so as to be capable of traveling by a crawler type lower traveling body 2, a swing device 3 provided on the lower traveling body 2, and the lower traveling body 2 via the swing device 3. The upper revolving superstructure 4 and a multi-joint front working device 5 (hereinafter referred to as a “working device 5”) which is provided in front of the upper revolving superstructure 4 and performs excavation work and the like. In this case, the lower traveling body 2 and the upper revolving superstructure 4 constitute a vehicle body (hydraulic shovel body) of the hydraulic shovel 1.

  The lower traveling body 2 includes left and right traveling hydraulic motors (not shown) for driving the left and right crawler belts 2A to circulate. The upper swing body 4 is mounted on the lower traveling body 2 via a swing device 3 including a swing bearing, a swing hydraulic motor, a speed reduction mechanism, and the like. The working device 5 is configured to include, for example, a boom 5A, an arm 5B, a bucket 5C as a working tool, a boom cylinder 5D, an arm cylinder 5E, and a bucket cylinder 5F as a working tool cylinder for driving these.

  The upper revolving unit 4 is provided on a revolving frame 6 serving as a support structure, a counter weight 7 provided on the rear side of the revolving frame 6 to balance weight with the working device 5, and provided on a front left side of the revolving frame 6. The vehicle includes a cab 8 on which an operator rides, and a building cover 9 provided in front of the counterweight 7 and accommodating the engine 10, the heat exchanger 14, the exhaust gas purification device 18 and the like inside. In the embodiment, the upper swing body 4 includes the engine 10 and the exhaust gas purifying device 18 (the urea selective reduction catalyst 22, the urea water tank 25, the sensor unit 28, and the like).

  Inside the cab 8, a driver's seat on which an operator sits, a traveling lever / pedal operating device and an operating lever operating device (all not shown) which are operating devices for operating the hydraulic excavator 1 are provided. ing. By operating the traveling lever / pedal operating device and the operating lever operating device, the operator can perform a traveling operation by the lower traveling unit 2, a turning operation of the upper revolving unit 4, a digging operation by the operation device 5, and the like. .

  The engine 10 is provided on the revolving frame 6 in front of the counterweight 7 so as to extend horizontally to the left and right. The engine 10 constitutes a prime mover (drive source) of the excavator 1 and is constituted by a diesel engine (internal combustion engine). On the left side of the engine 10, a cooling fan 10A for supplying cooling air to the heat exchanger 14 is provided. On the other hand, a hydraulic pump 15 is provided on the right side of the engine 10.

  As shown in FIG. 3, the engine 10 is provided with a water jacket 10B through which engine coolant flows to suppress a rise in temperature during operation. A cooling water pump 10C for circulating engine cooling water is provided on the inflow side of the water jacket 10B. The outlet side of the water jacket 10B is connected to the inlet of the heat exchanger 14 (radiator 14A) and the inlet of the cooling water pump 10C.

  A thermostat 10D is provided between the outlet of the heat exchanger 14 (radiator 14A) and the suction port of the cooling water pump 10C. The engine cooling water circulates in the water jacket 10B by driving the cooling water pump 10C. When the temperature of the engine cooling water increases, the thermostat 10D opens. As a result, the engine coolant flows toward the heat exchanger 14 (radiator 14A), and the temperature of the engine coolant can be maintained at an appropriate temperature.

  Thus, in the embodiment, the engine cooling system 11 for maintaining the temperature of the engine cooling water at an appropriate temperature is provided. The engine cooling system 11 includes a water jacket 10B, a cooling water pump 10C, a heat exchanger 14 (radiator 14A), and a cooling pipe 12 connecting these. The cooling pipe 12 is, for example, a radiator connection pipe 12A that connects the outlet of the water jacket 10B and the inlet of the radiator 14A, and a return that connects the outlet of the water jacket 10B and the suction port of the cooling water pump 10C. The pipe 12B includes a radiator-side return pipe 12C that connects the outlet of the radiator 14A and the suction port of the cooling water pump 10C.

  As will be described later, part of the engine cooling water (warm water) whose temperature has been increased by cooling the engine 10 is also used to warm (warm) the urea water in the urea water tank 25. That is, the engine cooling water is used not only as a cooling fluid (refrigerant) for cooling the engine 10 but also as a heating fluid (heating medium) for heating the urea water in the urea water tank 25. Therefore, in the embodiment, a urea water heating system 33 that warms the urea water in the urea water tank 25 is provided. The heating pipes 34 and 36 of the urea water heating system 33 are connected to the cooling pipe 12 of the engine cooling system 11.

  As shown in FIG. 2, an exhaust pipe 13 for discharging exhaust gas is connected to the engine 10. The exhaust pipe 13 is formed as a metal exhaust pipe extending leftward and rightward on the front side of the engine 10. The exhaust pipe 13 guides high-temperature exhaust gas discharged from the engine 10 to an exhaust gas post-processing device 19.

  The heat exchanger 14 is provided on the left side of the engine 10. The heat exchanger 14 is provided to face the cooling fan 10 </ b> A of the engine 10. The heat exchanger 14 is, for example, a radiator 14A that circulates through the water jacket 10B of the engine 10 to cool heated cooling water, an oil cooler that cools hydraulic oil, and an intercooler that cools air that the engine 10 sucks. Are also not shown).

  The hydraulic pump 15 is provided on the right side of the engine 10. The hydraulic pump 15 is driven by the engine 10 to discharge hydraulic oil stored in a hydraulic oil tank 16 as pressure oil. The hydraulic oil discharged from the hydraulic pump 15 is supplied to hydraulic actuators (for example, a boom cylinder 5D, an arm cylinder 5E, a bucket cylinder 5F, a turning hydraulic motor, and a traveling hydraulic motor) via a control valve device (not shown). Supplied.

  The hydraulic oil tank 16 is provided on the right side of the turning frame 6 in front of the hydraulic pump 15. The hydraulic oil tank 16 stores hydraulic oil for driving a hydraulic actuator. On the other hand, the fuel tank 17 is provided on the turning frame 6 in front of the hydraulic oil tank 16.

  The control valve device is a control valve group including a plurality of directional control valves. The control valve device distributes the pressure oil discharged from the hydraulic pump 15 to the hydraulic actuator according to the operation of the traveling lever / pedal operating device and the working lever operating device in the cab 8. That is, the control valve device supplies or discharges the pressure oil discharged from the hydraulic pump 15 to the hydraulic actuator in accordance with the lever operation and the pedal operation of the traveling lever / pedal operating device and the working lever operating device by the operator.

  Next, the exhaust gas purification device 18 will be described.

  The exhaust gas purifying device 18 purifies exhaust gas from the engine 10. The exhaust gas purification device 18 is disposed, for example, on the right side of the engine 10 and above the hydraulic pump 15. The exhaust gas purifying device 18 removes harmful substances in exhaust gas discharged from the engine 10. Further, the exhaust gas purifying device 18 is provided with a silencing mechanism for reducing the noise of the exhaust gas. The exhaust gas purification device 18 includes an exhaust gas post-processing device 19 having a urea selective reduction catalyst 22 and a urea water injection valve 24, a urea water tank 25, a urea water pipe 26, a urea water supply device 27, a sensor unit 28, an auxiliary heating. A unit 38 is provided.

  The exhaust gas after-treatment device 19 is connected to the outlet side of the exhaust pipe 13. The exhaust gas post-processing device 19 includes, for example, a cylindrical tubular body 20 extending forward and backward, a first oxidation catalyst 21, a urea selective reduction catalyst 22, and a second oxidation catalyst 23 provided in the tubular body 20. And a urea water injection valve 24.

  The cylindrical body 20 is formed as a closed container having both ends closed, and an exhaust pipe 13 is connected to a front portion on the upstream side. On the other hand, the tubular body 20 is provided with a tail pipe 20 </ b> A located at a rear portion on the downstream side. In the cylinder 20, a first oxidation catalyst 21, a urea selective reduction catalyst 22, and a second oxidation catalyst 23 are arranged at intervals in the length direction. A urea water injection valve 24 is attached to the cylinder 20 between the first oxidation catalyst 21 and the urea selective reduction catalyst 22.

  The first oxidation catalyst 21 is formed of, for example, a ceramic cylindrical body, has a large number of through holes formed in the axial direction, and has an inner surface coated with a noble metal or the like. The first oxidation catalyst 21 oxidizes and removes carbon monoxide (CO), hydrocarbon (HC), and the like contained in the exhaust gas by flowing the exhaust gas through each through hole at a predetermined temperature. Things. Further, if necessary, the particulate matter (PM) is also burned off.

  The urea selective reduction catalyst 22 is formed of, for example, a cellular cylindrical body made of ceramics, has a large number of through holes formed in the axial direction thereof, and has an inner surface coated with a noble metal. The urea selective reduction catalyst 22 is for removing nitrogen oxides (NOx) in the exhaust gas. That is, the urea selective reduction catalyst 22 selectively reduces the nitrogen oxides contained in the exhaust gas discharged from the engine 10 with ammonia generated from urea water (aqueous urea solution) to decompose into nitrogen and water. Things.

  The second oxidation catalyst 23 is, similarly to the first oxidation catalyst 21, formed of a ceramic cylindrical body, has a large number of through holes formed in the axial direction thereof, and has an inner surface coated with a noble metal. . The second oxidation catalyst 23 oxidizes residual ammonia remaining after reducing the nitrogen oxides with the urea selective reduction catalyst 22, and separates it into nitrogen and water.

  The urea water injection valve 24 is attached to the cylinder 20 so as to be located between the first oxidation catalyst 21 and the urea selective reduction catalyst 22. The urea water injection valve 24 is for injecting a urea aqueous solution toward exhaust gas flowing in the cylinder 20. That is, the urea water injection valve 24 is connected to the urea water tank 25 via the urea water pipe 26, and the urea water serving as the liquid reducing agent is located on the upstream side of the urea selective reduction catalyst 22 and is located in the cylinder 20. Inject.

  The urea water tank 25 stores urea water as a reducing agent (liquid reducing agent) for the urea selective reduction catalyst 22. As shown in FIG. 2, the urea water tank 25 is provided on the revolving frame 6 at a position on the front side of the fuel tank 17 as an example of an installation location. That is, the urea water tank 25 is disposed in front of the turning frame 6 and on the opposite side of the cab 8 from the left and right sides of the vehicle with the working device 5 interposed therebetween. As shown in FIG. 3, the urea water tank 25 is connected to the urea water injection valve 24 via a urea water pipe 26 and a urea water supply device 27. The urea water in the urea water tank 25 is supplied to the urea water injection valve 24 through the urea water pipe 26 by driving the urea water supply device 27.

  The urea water pipe 26 connects between the urea water tank 25 and the urea water injection valve 24. The urea water conduit 26 is made of, for example, a resin hose, a metal tube, or both a resin hose and a metal tube, and supplies the urea water stored in the urea water tank 25 with a urea water injection valve. 24. The urea water pipe 26 is connected to the upstream urea water supply pipe 26A connecting the urea water tank 25 and the urea water supply apparatus 27, and is connected to the downstream between the urea water supply apparatus 27 and the urea water injection valve 24. A side urea water supply pipe 26B and a urea water return pipe 26C connecting the urea water supply device 27 and the urea water tank 25 are provided. The urea water in the urea water tank 25 is supplied to the urea water injection valve 24 through the upstream urea water supply pipe 26A, the urea water supply device 27, and the downstream urea water supply pipe 26B. The excess urea water in the urea water supply device 27 is returned to the urea water tank 25 through the urea water return line 26C.

  The urea water supply device 27 is provided in the middle of the urea water pipe 26, that is, between the upstream urea water supply pipe 26A and the downstream urea water supply pipe 26B. The urea water supply device 27 supplies urea water from the urea water tank 25 to the urea water injection valve 24. The urea water supply device 27 is configured by, for example, a pump, a switching valve, a controller, and the like, and supplies a desired urea water to the urea water injection valve 24 according to an operation state (for example, an exhaust gas discharge amount). The urea water supply device 27 should suck the urea water in the urea water tank 25 from the urea water tank 25 through the upstream urea water supply pipe 26A, and spray the urea water from the sucked urea water according to the current operating condition. The urea water is supplied to the urea water injection valve 24 through the downstream urea water supply pipe 26B. On the other hand, excess urea water in the urea water supply device 27 is returned from the urea water supply device 27 to the urea water tank 25 through the urea water return line 26C.

  Next, the urea water tank 25 and the sensor unit 28 will be described.

  As shown in FIG. 4, the urea water tank 25 stores urea water W. The urea water tank 25 is configured to include a tank body 25A and a cap 25B. The tank body 25A is formed as a hollow box having a substantially rectangular cross section by, for example, pressing a metal plate such as a steel plate or the like, or by blow molding or injection molding a synthetic resin. I have. A water supply port 25A1 is provided at an upper corner of the tank body 25A. The cap 25B is detachably attached to the water supply port 25A1 of the tank body 25A.

  A sensor unit mounting hole 25A2 in which the sensor unit 28 is mounted is provided in the upper central portion of the tank body 25A. The sensor unit mounting hole 25A2 is formed on the upper surface side of the tank body 25A as a through hole (opening) penetrating upward and downward. The sensor unit mounting hole 25A2 is closed by the lid 28A of the sensor unit 28. Further, on the upper surface side of the tank body 25A, an auxiliary heating unit mounting hole 25A3 to which an auxiliary heating unit 38 described later is mounted, and a pair of female screw holes 25A4 to which the mounting plate fixing bolts 44, 44 described later are screwed. 25A4 are provided. The auxiliary heating unit mounting hole 25A3 is also formed as a through hole (opening) penetrating upward and downward. The auxiliary heating unit mounting hole 25A3 is closed by the mounting plate 43 of the auxiliary heating unit 38.

  The sensor unit 28 is inserted into the urea water tank 25. In addition to detecting the state of urea water, the sensor unit 28 also supplies urea water (sucks and sucks up), drains (returns) urea water, and heats (warms) urea water. It is configured as a "water detection / supply / drainage / heating unit". To this end, the sensor unit 28 includes a urea water supply pipe 29, a urea water return pipe 30, a first heating pipe 31 as a first heating device, and a state sensor 32.

  The sensor unit 28 is configured as an assembly in which the urea water supply pipe 29, the urea water return pipe 30, the first heating pipe 31, and the state sensor 32 are integrally assembled. To this end, the sensor unit 28 includes a lid 28A that closes the sensor unit mounting hole 25A2. The cover 28A is provided with a urea water supply pipe 29, a urea water return pipe 30, a first heating pipe 31, and a state sensor 32 penetrating therethrough.

  The urea water supply pipe 29 sucks up urea water from the urea water tank 25. That is, the urea water supply pipe 29 is a supply pipe that supplies (water supplies) the urea water stored in the urea water tank 25 to the urea water supply device 27 (urea water injection valve 24). The urea water supply pipe 29 can be formed by, for example, a metal pipe or a resin hose. The urea water supply pipe 29 forms an upstream end of the urea water pipe 26 (upstream urea water supply pipe 26A). The urea water supply pipe 29 extends to the vicinity of the bottom inside the tank body 25A through the lid 28A.

  The urea water return pipe 30 is a drain pipe that returns urea water not supplied from the urea water supply device 27 to the urea water injection valve 24, that is, urea water surplus in the urea water supply device 27, into the urea water tank 25. It is. The urea water return pipe 30 can be formed by, for example, a metal pipe or a resin hose. The urea water return pipe 30 forms a downstream end of the urea water pipe 26 (urea water return pipe 26C). The urea water return pipe 30 extends through the lid 28A into the tank body 25A.

  The first heating pipe 31 is provided in the urea water tank 25. The first heating pipe 31 is configured as an engine cooling water pipe that warms the urea water in the urea water tank 25 by flowing the engine cooling water. The first heating tube 31 can be formed by, for example, a metal tube. The first heating pipe 31 constitutes (a main heating system 33A of) a urea water heating system 33 described later. The first heating pipe 31 is folded back on the bottom side of the tank body 25A. In this case, the first heating pipe 31 has an extension 31A extending horizontally on the bottom side of the tank body 25A.

  That is, the first heating pipe 31 is configured such that a wide area can be heated in the horizontal direction by the extension 31A by providing the extension 31A extending horizontally on the bottom side of the tank body 25A. . As a result, the sensor unit 28 is inserted into the urea water tank 25, and has a cross-sectional shape (for example, a cross-sectional area) of the unit lower portion 28B (extended portion 31A) located on the lower side in the urea water tank 25. Are larger than the cross-sectional shape of the unit upper portion 28C located above the unit lower portion 28B. That is, the cross section of the lower side of the sensor unit 28 (the unit lower part 28B) is larger than the other part (the unit upper part 28C) due to the extension 31A of the first heating pipe 31.

  The state sensor 32 is a detection sensor that detects the state (quality, temperature, and the like) of the urea water. The state sensor 32 is, for example, a concentration sensor for detecting the concentration of urea water, a temperature sensor for detecting the temperature of urea water, a liquid level sensor for detecting the position of the liquid level of urea water, and identifying the liquid in the urea water tank 25. And the like. In this case, the state sensor 32 may be configured as a combination of a plurality of types of sensors for detecting the state of the urea water, or one of the plurality of types of sensors (for example, a temperature sensor) may be used alone. You may.

  By the way, the sensor unit 28 has a complicated shape in order to increase a heating area (thaw area) by the first heating pipe 31. More specifically, the sensor unit 28 is inserted into the urea water tank 25, and the unit lower portion 28B (the extended portion 31A of the first heating pipe 31) located on the lower side in the urea water tank 25 is turned on. Spreads more horizontally than above. Therefore, when the sensor unit 28 is detached from the urea water tank 25, the sensor unit 28 cannot be directly pulled out directly above.

  Thus, for example, even if the urea water in the urea water tank 25 is thawed from a completely frozen state to a state in which urea water can be supplied (sucked up), only the area around the first heating pipe 31 is thawed. In the case of only the state, there is a possibility that the sensor unit 28 cannot be pulled out from the urea water tank 25. That is, when the sensor unit 28 is replaced while the urea water in the urea water tank 25 is completely frozen, the engine cooling water is supplied to the first heating pipe 31 of the sensor unit 28 so that the sensor unit 28 is replaced. The urea water around the (first heating pipe 31) can be thawed. However, unless the sensor unit 28 (the first heating tube 31) alone does not thaw an area that is difficult to thaw (for example, a portion A indicated by a two-dot chain line in FIG. 4), the sensor unit 28 may be removed (pulled out). May not be possible.

  Therefore, in the embodiment, a second heating tube 39 as a second heating device is provided separately from the first heating tube 31 as the first heating device. That is, in the embodiment, a second heating device (second heating pipe 39) serving as an auxiliary heater (heat source) used when removing the sensor unit 28 from the frozen urea water tank 25 is installed. When the sensor unit 28 is pulled out of the urea water tank 25, a portion that needs to be thawed can be thawed. Furthermore, a float 41 for confirming thawing is provided in the urea water tank 25 so that the timing at which thawing is completed can be grasped.

  That is, as shown in FIG. 3, in the embodiment, a urea water heating system 33 that heats the urea water in the urea water tank 25 is provided. The urea water heating system 33 heats the urea water in the urea water tank 25 using the engine cooling water heated by the engine 10. For this purpose, the urea water heating system 33 is connected to the engine cooling system 11 so that the engine cooling water can flow to and from the engine cooling system 11. The urea water heating system 33 includes a main heating system 33A that heats the urea water in the urea water tank 25 using the first heating pipe 31 of the sensor unit 28, and a sensor unit 28 that starts from a state in which the urea water is frozen. And an auxiliary heating system 33B for thawing the urea water in the urea water tank 25 using the second heating pipe 39 when removing the urea water.

  The main heating system 33A includes a main heating pipe line 34, a main switching valve 35, and a first heating pipe 31 as a first heating device. The main heating pipe 34 connects an upstream main heating pipe 34 </ b> A connecting the upstream side of the return pipe 12 </ b> B of the engine cooling system 11 and the first heating pipe 31, and the first heating pipe 31. And a downstream main heating pipe 34B connecting the downstream side of the return pipe 12B.

  The main switching valve 35 is provided in the middle of the upstream main heating pipe 34A. That is, the main switching valve 35 is provided in the middle of the main heating pipe 34 that supplies the engine cooling water to the first heating pipe 31. The main switching valve 35 is a switching valve that switches whether or not to supply the engine cooling water to the first heating pipe 31. The main switching valve 35 is composed of, for example, a 2-port 2-position electromagnetic switching valve.

  The main switching valve 35 is connected to a communication position for supplying engine cooling water to the first heating pipe 31 (and the second heating pipe 39), and the first heating pipe 31 (and the second heating pipe 39). ) Has two switching positions, and a shut-off position for stopping the supply of engine cooling water. The main switching valve 35 can be configured to automatically switch to the communication position or the cutoff position in accordance with the temperature of the urea water in the urea water tank 25, for example. Further, the main switching valve 35 can be configured to be capable of manual switching based on, for example, an operation of a switching switch provided in the vicinity of the driver's seat of the cab 8.

  The first heating tube 31 is provided integrally with the sensor unit 28. The upstream side of the first heating pipe 31 is connected to the upstream main heating pipe 34A, and the downstream side of the first heating pipe 31 is connected to the downstream main heating pipe 34B. I have. The engine cooling water flows through the first heating pipe 31 when the main switching valve 35 is at the open position. Thereby, the urea water in the urea water tank 25 can be warmed.

  The auxiliary heating system 33B includes an auxiliary heating pipe 36, an auxiliary switching valve 37, a second heating pipe 39 as a second heating device, a float 41, and a stopper 42. ing. The auxiliary heating pipe 36 includes an upstream auxiliary heating pipe 36A that connects the upstream main heating pipe 34A of the main heating system 33A and the second heating pipe 39, and a second heating pipe. There is provided a downstream auxiliary heating pipe 36B that connects the downstream side 39 and the downstream main heating pipe 34B.

  The auxiliary switching valve 37 is provided in the middle of the upstream auxiliary heating pipe 36A. That is, the auxiliary switching valve 37 is provided in the middle of the auxiliary heating pipe 36 serving as a supply pipe for supplying engine cooling water to the second heating pipe 39. The auxiliary switching valve 37 is a switching valve that switches whether to supply the engine cooling water to the second heating pipe 39. The auxiliary switching valve 37 is composed of, for example, a 2-port 2-position electromagnetic switching valve. The auxiliary switching valve 37 has two switching positions, a communication position for supplying the engine cooling water to the second heating pipe 39 and a shutoff position for stopping the supply of the engine cooling water to the second heating pipe 39. doing.

  The auxiliary switching valve 37 can be configured to be capable of manual switching based on, for example, an operation of a switching switch provided near a driver's seat of the cab 8. In this case, for example, an operator performing maintenance defrosts the urea water from a state where the urea water in the urea water tank 25 is completely frozen to a state where the sensor unit 28 can be removed (pulled out) in order to replace the sensor unit 28. At this time, the auxiliary switching valve 37 is set to the communication position based on the operation of the selector switch. As a result, the engine coolant flows through not only the first heating pipe 31 but also the second heating pipe 39, and the urea water in the urea water tank 25 can be heated. That is, the frozen urea water in the urea water tank 25 can be thawed by the two heating tubes 31 and 39, that is, the first heating tube 31 and the second heating tube 39.

  The second heating pipe 39 is provided in the urea water tank 25, similarly to the first heating pipe 31. That is, in the urea water tank 25, a second heating pipe 39 as a second heating device is provided separately from the first heating pipe 31 of the sensor unit 28. The second heating pipe 39 is disposed at a position soaked in urea water in the urea water tank 25. The second heating pipe 39 warms the urea water in the urea water tank 25 at a position away from the first heating pipe 31.

  The second heating pipe 39 is configured by an engine cooling water pipe that warms the urea water by flowing the engine cooling water. That is, similarly to the first heating tube 31, the second heating tube 39 can be formed by, for example, a metal tube. The second heating pipe 39 is located above the unit lower part 28B (the expanded part 31A of the first heating pipe 31), which is located below the sensor unit 28 and has a larger cross-sectional shape. .

  Here, the second heating pipe 39 forms an auxiliary heating unit 38 together with the float 41 and the like. That is, the auxiliary heating unit 38 includes a second heating pipe 39, an expansion plate 40, a float 41, a stopper 42, a mounting plate 43, mounting plate fixing bolts 44, 44, and a stopper holding bolt 45, 45. The auxiliary heating unit 38 not only heats (warms) the urea water in the urea water tank 25 together with the sensor unit 28, but also displays whether or not the urea water has been thawed. Decompression display unit ". The auxiliary heating unit 38 is arranged above the unit lower part 28B of the sensor unit 28, that is, in an area where the sensor unit 28 is not easily thawed (part A in FIG. 4).

  As shown in FIGS. 4 to 12, the second heating pipe 39 is configured by, for example, bending a pipe body into a U-shape. The second heating pipe 39 includes an upstream pipe 39A extending upward and downward in the urea water tank 25, a downstream pipe 39B extending upward and downward in the urea water tank 25 in parallel with the upstream pipe 39A, and an upstream pipe 39A. A connection pipe 39C for connecting the upstream pipe 39A and the downstream pipe 39B at a lower end side of the pipe 39A and the downstream pipe 39B is provided.

  The opening on the upper end side of the upstream pipe 39A and the opening on the upper end side of the downstream pipe 39B are closed by sealing plugs 46, respectively. Near the upper end of the upstream pipe 39A, that is, on the upper end side of the upstream pipe 39A, above the mounting plate 43 and below the sealing plug 46, the downstream end of the upstream auxiliary heating pipe 36A is connected. A hole 39A1 is provided. Near the upper end of the downstream pipe 39B, that is, on the upper end side of the downstream pipe 39B, above the mounting plate 43 and below the sealing plug 46, a connection to which the upstream end of the downstream auxiliary heating pipe 36B is connected. A hole 39B1 is provided.

  The expansion plate 40 is fixed below the second heating pipe 39, that is, below the connection pipe 39C. As shown in FIG. 12, the expansion plate 40 is formed as a circular plate (disk). On the upper surface side of the expansion plate 40, a concave portion 40A into which the connection pipe 39C enters is provided. The expansion plate 40 is fixed to the connection pipe 39C with the connection pipe 39C inserted into the recess 40A. The heat of the engine cooling water is transmitted to the expansion plate 40 from the connection pipe 37C. Thus, the expansion plate 40 can heat a wide area in the horizontal direction below the second heating pipe 39.

  The float 41 is provided in the urea water tank 25 so as to be able to move upward and downward with respect to the second heating pipe 39. That is, the urea water tank 25 is provided with a float 41 for determining whether or not the urea water around the second heating pipe 39 has been thawed. As shown in FIGS. 8 and 11, the float 41 floats by buoyancy when the urea water around the second heating pipe 39 is thawed. Thus, when the float 41 is floating, it can be determined that the sensor unit 28 can be removed from the urea water tank 25.

  The float 41 has a cylindrical one-side column portion 41A into which the upstream pipe 39A of the second heating pipe 39 is inserted, and a cylindrical other-side column portion 41B into which the downstream tube 39B is inserted. A connecting portion 41C is provided for connecting the one side pillar portion 41A and the other side pillar portion 41B. Even if the downstream end of the upstream auxiliary heating pipe 36A is connected to the connection hole 39A1 of the upstream pipe 39A, the one pillar 41A is moved upward and downward with respect to the upstream pipe 39A. A notch 41A1 extending upward and downward is provided so as to be movable. Even when the upstream end of the downstream auxiliary heating pipe 36B is connected to the connection hole 39B1 of the downstream pipe 39B, the other pillar 41B is moved upward and downward with respect to the downstream pipe 39B. A notch 41B1 extending upward and downward is provided so as to be able to move to the right.

  The connecting portion 41C is formed as a circular plate (disk), like the expansion plate 40 of the second heating tube 39. The float 41 can be formed of a material floating in urea water, for example, a polymer material such as plastic or styrene foam. In this case, the entire float 41, that is, all of the one-side pillar portion 41A, the other-side pillar portion 41B, and the connecting portion 41C can be formed of a material floating in urea water. Further, only the connecting portion 41C of the float 41 may be formed of a material floating on the urea water. In this case, by forming the one side pillar portion 41A and the other side pillar portion 41B from a material having a high heat transfer coefficient such as a metal, the heat of the engine cooling water flowing through the second heating pipe 39 is reduced by urea. It can be easily transmitted to water and can improve thawing performance.

  The stopper 42 supports the float 41 so that the float 41 does not float even when the urea water is not frozen (thawed). That is, the stopper 42 can maintain the state in which the float 41 is submerged in the urea water in the urea water tank 25. The stopper 42 includes a disk-shaped main body 42A detachably attached to the mounting plate 43, and a pair of bottomed cylindrical holding parts 42B, 42C protruding upward from the main body 42A.

  The upper end of the upstream pipe 39A of the second heating pipe 39 and the upper end of the one-side pillar 41A of the float 41 are accommodated inside the one holding portion 42B. The upper end of the downstream pipe 39B of the second heating pipe 39 and the upper end of the other side column 41B of the float 41 are accommodated inside the other holding section 42C. The body 42A is provided with a pair of insertion holes 42A1 and 42A1 through which the stopper holding bolts 45 and 45 are inserted. The stopper 42 is screwed to the mounting plate 43 by stopper retaining bolts 45, 45 in a state where the upper ends of the column portions 41A, 41B of the float 41 are accommodated in the retaining portions 42B, 42C.

  In this case, even if the downstream end of the upstream auxiliary heating pipe 36A is connected to the connection hole 39A1 of the upstream pipe 39A, the stopper 42 can be attached to the main body 42A and one of the holding sections 42B. Thus, the one-side notch 42D is provided. Even if the upstream end of the downstream auxiliary heating pipe 36B is connected to the connection hole 39B1 of the downstream pipe 39B, the stopper 42 can be attached to the attachment plate 43 in the main body 42A and the other holding section 42C. The other side notch 42E is provided.

  The mounting plate 43 is mounted on the tank main body 25A in a state where the mounting plate 43 covers the auxiliary heating unit mounting hole 25A3 of the urea water tank 25 from above. The mounting plate 43 is formed of a circular plate (disk) having a larger diameter than the auxiliary heating unit mounting hole 25A3. The mounting plate 43 has an upper end of an upstream pipe 39A of the second heating pipe 39 and a one-side insertion hole 43A into which the one-side pillar 41A of the float 41 is inserted, and a downstream pipe 39B of the second heating pipe 39. And the other side insertion hole 43B through which the other side column portion 41B of the float 41 is inserted.

  Thereby, the one-side pillar portion 41A of the float 41 can be displaced (moved) upward and downward between the one-side insertion hole 43A of the mounting plate 43 and the upstream pipe 39A of the second heating pipe 39. Has become. Further, the other-side column portion 41B of the float 41 can be displaced (moved) in the upward and downward directions between the other-side insertion hole 43B of the mounting plate 43 and the downstream tube 39B of the second heating tube 39. ing.

  The mounting plate 43 is provided with a pair of female screw holes 43C, 43C into which stopper stopper bolts 45, 45 are screwed, and a pair of insertion holes 43D, 43D through which the mounting plate fixing bolts 44, 44 are inserted. . The mounting plate 43 is screwed to the upper surface of the urea water tank 25 by mounting plate fixing bolts 44, 44 inserted into the insertion holes 43D, 43D.

  The mounting plate fixing bolts 44, 44 are inserted through the insertion holes 43D, 43D of the mounting plate 43, and screwed into the female screw holes 25A4, 25A4 of the tank body 25A. The stopper holding bolts 45 are inserted into the insertion holes 42A1 and 42A1 of the stopper 42 and screwed into the female screw holes 43C and 43C of the mounting plate 43.

  The hydraulic shovel 1 according to the embodiment has the above-described configuration. Next, the operation thereof will be described.

  The operator gets on the cab 8 and starts the engine 10. When the engine 10 starts, the hydraulic pump 15 is driven by the engine 10. Hydraulic oil discharged from the hydraulic pump 15 is supplied to the traveling hydraulic motor, the turning hydraulic motor, and the like according to the lever operation and pedal operation of the traveling lever / pedal operating device and the working lever operating device disposed in the cab 8. It discharges toward the boom cylinder 5D, the arm cylinder 5E, the bucket cylinder 5F, and the like. Thus, the hydraulic excavator 1 can perform a traveling operation by the lower traveling unit 2, a turning operation of the upper revolving unit 4, an excavation operation by the working device 5, and the like.

  During operation of the engine 10, exhaust gas discharged from the engine 10 passes through the exhaust pipe 13 and the exhaust gas aftertreatment device 19 and is discharged into the atmosphere. In this case, carbon monoxide (CO), hydrocarbon (HC) and the like contained in the exhaust gas are oxidized and removed by the first oxidation catalyst 21 provided in the exhaust gas post-processing device 19. Further, if necessary, the particulate matter (PM) is burned and removed. On the other hand, on the downstream side of the first oxidation catalyst 21, urea water is injected from the urea water injection valve 24 toward the exhaust gas, and nitrogen oxides are decomposed into nitrogen and water by the urea selective reduction catalyst 22. Further, the second oxidation catalyst 23 oxidizes residual ammonia and separates it into nitrogen and water, so that exhaust gas sufficiently purified can be discharged into the atmosphere.

  Here, when the engine 10 is driven and the main switching valve 35 of the urea water heating system 33 is switched to the communication position, the urea water in the urea water tank 25 is subjected to the first heating. It is heated (warmed) by the engine cooling water flowing through the pipe 31. For this reason, even when the hydraulic excavator 1 is used in a cold region where urea water freezes, the frozen urea water can be thawed by the engine cooling water and the thawed urea water can be sent to the urea water injection valve 24. it can.

  Further, for example, when replacing the sensor unit 28 when the urea water in the urea water tank 25 is completely frozen, the main switching valve 35 and the auxiliary switching valve of the urea water heating system 33 while the engine 10 is driven. 37 is switched to the communication position. Thereby, the urea water around the sensor unit 28 can be thawed by the first heating pipe 31. Further, the urea water around the auxiliary heating unit 38 can be thawed by the second heating pipe 39. Thereby, not only the periphery of the sensor unit 28 but also the part remote from the sensor unit 28 can be efficiently thawed.

  Further, when the stopper 42 of the auxiliary heating unit 38 is removed, the float 41 becomes movable. In this state, when the thawing of the urea water in the urea water tank 25 proceeds, the float 41 is pushed up by the buoyancy of the urea water. Thereby, it can be determined whether or not the urea water has been thawed. That is, an operator who replaces the sensor unit 28 can remove (pull out) the sensor unit 28 from the urea water tank 25 after the float 41 has risen, so that the removal operation can be performed smoothly.

  As described above, according to the embodiment, the second heating pipe 39 is provided in the urea water tank 25 separately from the first heating pipe 31 of the sensor unit 28. In this case, the second heating pipe 39 is disposed at a position away from the first heating pipe 31 and at a position soaked in the urea water in the urea water tank 25. For this reason, when the urea water is frozen in the urea water tank 25, not only the area around the sensor unit 28 but also the portion remote from the sensor unit 28 can be efficiently thawed by the second heating pipe 39. That is, when the urea water in the urea water tank 25 is completely frozen, and the sensor unit 28 can be removed (pulled out), the area that is not easily melted by the first heating pipe 31 is moved to the second heating pipe. 39 enables efficient melting. As a result, it is possible to prevent the sensor unit 28 from being removed (pulled out) from the urea water tank 25 in a state where the thawing is insufficient.

  Moreover, according to the embodiment, the second heating pipe 39 is located at the lower side of the sensor unit 28 and has a larger cross-sectional shape in the unit lower portion 28B (the expanded portion of the first heating pipe 31). 31A). For this reason, the area (the portion A in FIG. 4) that is difficult to warm with the first heating tube 31 above the unit lower portion 28B of the sensor unit 28 can be directly heated by the second heating tube 39. In other words, when removing (pulling out) the sensor unit 28 from the frozen urea water tank 25, the portion that needs to be thawed can be thawed directly by the second heating pipe 39. Moreover, since the upper part of the sensor lower portion 28B (extended portion 31A) of the sensor unit 28 is directly thawed by the second heating pipe 39, the sensor unit 28 can be easily removed (pulled out).

  According to the embodiment, the urea water tank 25 is provided with the float 41 for determining whether or not the urea water around the second heating pipe 39 has been thawed. Therefore, when the float 41 floats (rises), it is possible to know the timing at which the thawing of the urea water is completed. That is, the timing at which the sensor unit 28 can be removed (pulled out) from the urea water tank 25 by the float 41 can be grasped. Thus, when removing (pulling out) the sensor unit 28, for example, the frozen lump of urea water comes into contact with the sensor unit 28, the inner surface of the urea water tank 25, a component (for example, a strainer) in the urea water tank 25, and the like. Can be suppressed.

  According to the embodiment, the second heating pipe 39 is configured by an engine cooling water pipe that warms the urea water by flowing the engine cooling water. Therefore, the heat of the engine cooling water can be effectively used for warming the urea water by the second heating pipe 39. Moreover, in the middle of the supply pipe (auxiliary heating pipe 36) for supplying the engine cooling water to the second heating pipe 39, it is determined whether or not the engine cooling water is to be supplied to the second heating pipe 39. A switching valve (auxiliary switching valve 37) for switching is provided. For this reason, whether to perform heating by the second heating pipe 39 can be switched by the switching valve (the auxiliary switching valve 37). As a result, the second heating tube 39 can be used only when necessary, for example, only when removing (pulling out) the sensor unit 28 from the frozen urea water tank 25. That is, when the heating by the second heating pipe 39 is not necessary, the heating by the second heating pipe 39 can be stopped, and unnecessary heating by the second heating pipe 39 is suppressed. can do.

  In the embodiment, the case where the second heating pipe 39 as the second heating device is configured by the engine cooling water pipe has been described as an example. However, the present invention is not limited to this. For example, the second heating device may be configured by an electric heater (electric heater) that heats urea water by supplying electric power. In this case, the second heating device can be simply configured. Moreover, by providing a switch for switching between ON and OFF in the electric heater, the second heating device (electric heater) can be used only when necessary, for example, when removing (pulling out) the sensor unit from the frozen urea water tank. Can be enabled. Thereby, when the heating by the second heating device (electric heater) is not necessary, the heating by the second heating device (electric heater) can be stopped, and the second heating device (electric heating device) can be stopped. Unnecessary heating by the device) can be suppressed.

  In the embodiment, the case where the sensor unit 28 includes the urea water supply pipe 29, the urea water return pipe 30, the first heating pipe 31, and the state sensor 32 has been described as an example. However, the present invention is not limited to this. For example, the sensor unit and the urea water return pipe may be separately provided (the urea water return pipe may be provided separately from the sensor unit). That is, the sensor unit may be configured by the urea water supply pipe, the first heating device, and the state sensor. In addition, for example, two urea water return pipes may be provided. In this case, for example, one urea water return pipe may be provided in the sensor unit, and the other urea water return pipe may be provided separately from the sensor unit and the auxiliary heating unit. Further, both urea water return pipes may be arranged separately from the sensor unit and the auxiliary heating unit.

  In the embodiment, an example has been described in which the float 41 that determines whether or not the urea water around the second heating pipe 39 has been thawed is provided. However, the present invention is not limited to this. For example, the float may be omitted. In this case, for example, a configuration may be adopted in which a small window (transmission window) is provided on the tank body of the urea water tank so that it is possible to visually check whether or not the urea water has been thawed. Further, both the float and the small window may be provided.

  In the embodiment, the case where the second heating pipe 39 is provided above the unit lower part 28B of the sensor unit 28 (the extension 31A of the first heating pipe 31) has been described as an example. However, the present invention is not limited to this. The second heating device, for example, needs to be thawed when removing the sensor unit, and can be provided at a position where it is difficult for the sensor unit (first heating device) to thaw.

  In the embodiment, the case where the main switching valve 35 is provided in the middle of the upstream main heating pipe 34A has been described as an example. However, the invention is not limited to this. For example, the switching valve (main switching valve) may be omitted. That is, when the engine (cooling water pump) is driven, the engine cooling water is constantly supplied to the first heating pipe (first heating device) through the supply pipe (upstream main heating pipe). May be adopted.

  In the embodiment, the case where the auxiliary switching valve 37 is provided in the middle of the upstream auxiliary heating pipe 36A has been described as an example. However, the present invention is not limited to this. For example, the switching valve (auxiliary switching valve) may be omitted. That is, when the engine (cooling water pump) is driven, the engine cooling water is constantly supplied to the second heating pipe (second heating device) through the supply pipe (upstream auxiliary heating pipe). May be adopted.

  In the embodiment, the case where the urea water tank 25 is disposed on the front side of the fuel tank 17, that is, on the front side of the turning frame 6 has been described as an example. However, the present invention is not limited to this, and the urea water tank may be arranged at a place other than the front side of the turning frame, for example, at the front side of the counterweight, at the front side of the engine, or the like.

  In the embodiment, the case where the vehicle body is constituted by the lower traveling structure 2 and the upper revolving structure 4 has been described as an example. However, the present invention is not limited thereto, and may be applied to a vehicle body having no revolving body (for example, an articulated vehicle body in which a front vehicle body having front wheels and a rear vehicle body having rear wheels are flexibly connected via a connection shaft). Is also good.

  In the embodiment, the crawler-type hydraulic excavator 1 has been described as an example of the construction machine. However, the present invention is not limited to this, and can be widely applied to various types of construction machines such as a wheel-type hydraulic excavator, a hydraulic crane, a wheel loader, and a dump truck.

1 Hydraulic excavator (construction equipment)
Reference Signs List 22 urea selective reduction catalyst 25 urea water tank 28 sensor unit 28B unit lower part 28C unit upper part 29 urea water supply pipe 31 first heating pipe (first heating device)
32 state sensor 36 auxiliary heating line (supply line)
37 Auxiliary switching valve (switching valve)
39 Second heating pipe (second heating device)
41 float W urea water

Claims (4)

A urea water tank for storing urea water as a reducing agent of a urea selective reduction catalyst for removing nitrogen oxides in exhaust gas,
A sensor unit inserted into the urea water tank,
The sensor unit is configured to heat the urea water in the urea water tank by flowing engine cooling water disposed in the urea water tank and a urea water supply pipe for sucking up urea water from the urea water tank. A first heating device and a state sensor for detecting a state of the urea water are configured as an assembly, and a lower side of the urea water tank is inserted into the urea water tank. In a construction machine configured such that the cross-sectional shape of the unit lower portion located at a position larger than the cross-sectional shape of the unit upper portion positioned above the unit lower portion,
In the urea water tank, the sensor unit is disposed at a position immersed in the urea water in the urea water tank separately from the first heating device, and at a position away from the first heating device. A second heating device for heating the urea water in the urea water tank is provided,
The construction machine, wherein the second heating device is disposed above the lower portion of the unit, which is located below the sensor unit and has a larger cross-sectional shape. The construction machine according to claim 1,
A construction machine, wherein the urea water tank is provided with a float for determining whether or not the urea water around the second heating device has been thawed. The construction machine according to claim 1,
The construction machine, wherein the second heating device is configured by an electric heater that heats the urea water by supplying electric power. The construction machine according to claim 1,
The second heating device includes an engine cooling water pipe that warms the urea water by flowing the engine cooling water,
A switching valve for switching whether or not to supply the engine cooling water to the second heating device is provided in the middle of a supply pipe for supplying engine cooling water to the second heating device. Construction machinery.

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