Urea water tank of construction machinery

Abstract

To provide a urea water tank of a construction machine that can speedily unfreeze and supply urea water reserved inside to an injection nozzle if the urea water is frozen, and thereby can let an SCR catalyst function as early as possible.SOLUTION: A urea water suction duct 25 is extended vertically in a urea water tank 16, and urea water is sucked from a suction part 31 provided therebelow to be supplied to an injection nozzle for an SCR catalyst. Cooling water ducts 27a and 27b are extended vertically and also have their lower parts connected by a folded duct 27c, and the urea water frozen in the urea water tank 16 is unfrozen with heat of engine cooling water circulating therein. A heat insulation cover 40 is installed correspondingly to vertical extension parts of the ducts 25, 27a and 27b to block heat radiated to the left from the cooling water ducts 27a and 27b, and consequently, quantities of heat transfer to the urea water suction duct 25 and the suction part 31 located on the right side of the heat insulation cover 40 are increased to achieve early unfreezing.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an aqueous urea tank for construction machinery.

Background Art

[0002] Construction machinery, such as hydraulic excavators, bulldozers, wheel loaders, etc., is equipped with an engine as a power source, and an exhaust gas treatment device for treating various harmful components contained in the exhaust gas is provided in the exhaust passage of the engine. As one of the exhaust gas treatment devices, an SCR catalyst (selective reduction type NOx catalyst) is provided to treat NOx in the exhaust gas, and an injection nozzle for aqueous urea is installed upstream of the SCR catalyst. The injection nozzle is connected to an aqueous urea tank via a pipe equipped with an aqueous urea pump, and an aqueous urea pipeline communicating with the pipe is disposed in the aqueous urea tank. During the operation of the engine, the aqueous urea pump operates, the aqueous urea in the aqueous urea tank is sucked from the suction part at the tip of the aqueous urea pipeline, injected from the injection nozzle through the pipe, and thereby the SCR catalyst functions to reduce NOx in the exhaust gas.

[0003] The aqueous urea in the aqueous urea tank may freeze. For example, when the construction machinery is parked overnight in a cold region, even if the engine can be started and operated, a situation may occur where the aqueous urea freezes and cannot be supplied to the injection nozzle. In such a case, since the SCR catalyst does not function properly and the construction machinery cannot be started, it is desired to quickly thaw the aqueous urea in the aqueous urea tank. As a countermeasure, a cooling water pipeline connected to the engine side is disposed inside the aqueous urea tank, and the cooling water of the engine is circulated through the cooling water pipeline, so that the heat of the cooling water thaws the aqueous urea in the aqueous urea tank.

[0004] In order to efficiently utilize the heat of such engine cooling water, for example, the technology described in Patent Document 1 has been proposed. In this technology, by devising the shape of the cooling water pipeline in the aqueous urea tank, the uneven heat transfer to the frozen aqueous urea is reduced, and the uniform thawing of the aqueous urea in the aqueous urea tank is achieved.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, since there are the following limitations in the thawing ability of urea aqueous solution using engine cooling water, it was difficult to quickly thaw the urea aqueous solution with the technology of Patent Document 1.

[0007] That is, the thawing ability by cooling water depends on the amount of heat possessed by the cooling water itself and the efficiency of heat transfer determined by the surface area of the cooling water pipe in the urea aqueous solution tank, etc. However, due to the recent trend of reducing fuel consumption, the exhaust heat of the engine is decreasing, so the amount of heat possessed by the cooling water, in other words, the amount of heat available for thawing the urea aqueous solution is limited. In addition, increasing the surface area by extending the cooling water pipe, etc. will increase the size, so there are limitations from the viewpoints of, for example, arranging the cooling water pipe in the urea aqueous solution tank or the work of attaching and detaching the cooling water pipe to the urea aqueous solution tank. Therefore, it is important how to efficiently utilize the limited thawing ability by engine cooling water to quickly thaw the urea aqueous solution and supply it to the injection nozzle.

[0008] However, since the technology of Patent Document 1 aims at uniform thawing of the aqueous urea in the aqueous urea tank, waste occurs in the thawing of the aqueous urea. Specifically, the aqueous urea in the aqueous urea tank is sucked from the suction part and supplied to the injection nozzle through the aqueous urea pipeline. For this reason, quickly thawing the aqueous urea frozen inside the aqueous urea pipeline including the suction part and the aqueous urea frozen around the suction part leads to rapid supply to the injection nozzle. When the aqueous urea in the aqueous urea tank is uniformly thawed, not only the aqueous urea in such important areas but also the aqueous urea in areas where early thawing is not required, for example, the aqueous urea in areas far from the aqueous urea pipeline, is thawed. And there was a problem that the thawing of the aqueous urea in the important area and thus the supply of the aqueous urea to the injection nozzle were delayed by the amount of heat consumed at that time.

[0009] The present invention has been made to solve such problems, and its object is to provide an aqueous urea tank for a construction machine that can quickly thaw the aqueous urea stored inside and supply it to an injection nozzle, thereby enabling the SCR catalyst to function quickly.

Means for Solving the Problems

[0010] To achieve the above object, the aqueous urea tank of the construction machine of the present invention is an aqueous urea tank for a construction machine that stores the aqueous urea to be supplied to an exhaust gas treatment device provided in an engine in a tank body. In the tank body, it extends vertically downward and a suction part is provided at the lower part, an aqueous urea suction pipeline that supplies the aqueous urea sucked up from the suction part to the exhaust gas treatment device, a cooling water pipeline that extends vertically in the tank body and circulates the cooling water from the engine, and a urea water supply and thawing unit composed of sensors for detecting the state of the aqueous urea in the tank body, and a heat insulation cover arranged with one side facing each other with respect to the vertical extension locations of the aqueous urea suction pipeline and the cooling water pipeline. , the sensors include a liquid level sensor having a float that changes its vertical position corresponding to the liquid level of the aqueous urea solution. In the tank body, a replenishment port for replenishing the aqueous urea solution from the outside is opened and a water supply filter is connected. The water supply filter is disposed on the side opposite to the float with the heat insulation cover interposed therebetween. It is characterized by this. Further, in the urea water tank of a construction machine according to the present invention, in the urea water tank of a construction machine that stores the urea water supplied to an exhaust gas treatment device provided in an engine in a tank body, a suction portion is provided at a lower portion thereof extending vertically in the tank body. A urea water suction pipeline that supplies the urea water sucked up from the suction portion to the exhaust gas treatment device, a cooling water pipeline that extends vertically in the tank body and circulates the cooling water from the engine, and sensors that detect the state of the aqueous urea solution in the tank body. A urea water supply and thawing unit, and a heat insulation cover disposed with one side facing each other in the vertical extension locations of the urea water suction pipeline and the cooling water pipeline, respectively. The suction portion is bent at a substantially right angle from the lower end of the vertical extension location of the urea water suction pipeline, and extends in a direction away from the heat insulation cover along the bottom surface of the tank body in a plan view.

Effects of the Invention

[0011] According to the urea water tank of the construction machine of the present invention, when the urea water stored inside freezes, it can be quickly thawed and supplied to the injection nozzle, thereby enabling the SCR catalyst to function quickly.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an embodiment in which the present invention is embodied in the urea water tank of a hydraulic excavator will be described. [Overall Configuration] FIG. 1 is a side view showing a hydraulic excavator equipped with the urea water tank of the present invention. In the following description, the front-rear, left-right, and up-down directions are defined mainly based on the operator riding on the hydraulic excavator.

[0014] The lower traveling body 2 of the hydraulic excavator 1 (which is a construction machine of the present invention and may hereinafter also be referred to as a vehicle) is provided with a pair of left and right crawlers 3, and these crawlers 3 are driven by a traveling drive device (not shown) so that the lower traveling body 2 travels. On the lower traveling body 2, a swing frame 5 of an upper swing body 4 is connected via a swing device (not shown), and the upper swing body 4 swings by being driven by the swing device. A bearing frame 6 is provided at the front part on the swing frame 5, and a multi-articulated working front 9 composed of a boom 7, an arm (not shown), and a bucket is supported by the bearing frame 6. The boom 7, the arm, and the bucket are each tilted by being driven by a hydraulic cylinder such as a boom cylinder 8, whereby the working front 9 operates.

[0015] A driver's cab 10 is provided on the left side of the bearing frame 6 on the swing frame 5, and the driver's cab 10 is equipped with operating equipment (not shown) for an operator to operate the hydraulic excavator 1. Further, a machine room 11 is provided on the swing frame 5, and a counterweight 12 is provided at the rearmost part. The machine room 11 houses a diesel engine 13 (hereinafter simply referred to as an engine), an exhaust gas treatment device 14, and a urea water tank 16, and also houses various devices such as a hydraulic control unit, a fuel tank, and a hydraulic oil tank (not shown).

[0016] During the operation of the hydraulic excavator 1, the engine 13 is operated by the fuel supplied from the fuel tank, and the hydraulic pump of the hydraulic control unit is driven. The hydraulic oil in the hydraulic oil tank is pumped up by the hydraulic pump, and the hydraulic oil discharged from the hydraulic pump is supplied to the hydraulic valve of the hydraulic control unit. The hydraulic valve is switched according to the operator's operation, and is selectively supplied to the hydraulic motor of the traveling drive device or the swing device, or the boom cylinder 8 of the working front 9. Thereby, the traveling of the vehicle 1, the swinging of the upper swing body 4, the operation of the working front 9, etc. can be arbitrarily executed.

[0017] The exhaust gas treatment device 14 is provided in the exhaust passage of the engine 13 and treats harmful components contained in the exhaust gas. In order to treat NOx in the exhaust gas, although not shown in the figure, an SCR catalyst (selective reduction type NOx catalyst) is provided as one of the exhaust gas treatment devices 14, and an injection nozzle for urea water is installed upstream of the SCR catalyst. The injection nozzle is connected to the urea water tank 16 via a pipe, and a urea water pump is interposed in the pipe. During the operation of the engine 13, the urea water pump operates, and the urea water in the urea water tank 16 is injected from the injection nozzle into the exhaust passage of the engine 13 through the pipe. The urea water is hydrolyzed by the exhaust heat and water vapor in the exhaust gas, and the NH3 generated thereby is supplied onto the SCR catalyst, and the NOx in the exhaust gas is reduced to harmless N2.

[0018] FIG. 2 is a perspective view showing the urea water tank 16, FIG. 3 is a sectional view taken along line III-III of FIG. 2 showing the urea water supply / thawing unit, and FIG. 4 is a sectional view taken along line IV-IV of FIG. 2 showing the urea water supply / thawing unit. For such supply of urea water, a urea water suction pipe 25 and a urea water return pipe 26 are provided in the urea water tank 16, and a cooling water pipe 27 for thawing the frozen urea water, and sensors 33, 34 for detecting the storage amount, temperature, and concentration of the urea water (each corresponding to the "state of the urea water" of the present invention) are provided. These urea water suction pipe 25, urea water return pipe 26, cooling water pipe 27, and sensors 33, 34 are integrated as a urea water supply / thawing unit 23 attached to the urea water tank 16, and the details thereof will be described below.

[0019] [Configuration of Urea Water Supply / Thawing Unit] The tank body 17 of the urea water tank 16 is in the shape of a hollow rectangular parallelepiped, and an inclined surface 17a is formed at the upper part of its front surface, and a replenishment port 18 is provided. A detachable cap 19 is attached to the replenishment port 18, and a water supply filter 20 is attached to the replenishment port 18 inside the tank body 17. The replenishment of urea water to the tank body 17 is carried out by removing the cap 19 after opening the cover 11a (shown in FIG. 1) of the machine room 11, and the urea water replenished from the outside to the replenishment port 18 is filtered by the water supply filter 20 and stored in the tank body 17.

[0020] A circular insertion / removal hole 22 is formed through the substantially center of the top surface 17b of the tank body 17, and a circular base portion 24 of the urea water supply / thawing unit 23 is detachably attached to and closes the insertion / removal hole 22. Inside the tank body 17, a urea water suction pipeline 25, a urea water return pipeline 26, a cooling water pipeline 27, a float guide pipeline 28, and a harness pipeline 29 are arranged.

[0021] The cooling water pipeline 27 is composed of a cooling water introduction pipeline 27a, a cooling water discharge pipeline 27b, and a return pipeline 27c. The upper parts of the urea water suction pipeline 25, the urea water return pipeline 26, the cooling water introduction pipeline 27a, the cooling water discharge pipeline 27b, the float guide pipeline 28, and the harness pipeline 29 respectively penetrate through the base portion 24 and protrude upward.

[0022] The upper part of the urea water suction pipeline 25 protruding from the base portion 24 is connected to the injection nozzle of the SCR catalyst via pipes (not shown) and a urea water pump. Inside the tank body 17, the urea water suction pipeline 25 extends downward from the base portion 24, bends at a right angle to the right near the bottom surface 17c of the tank body 17, and a filter 30 is attached. Thereby, a suction portion 31 of the urea water suction pipeline 25 is formed, and the suction portion 31 extends to the right along the bottom surface 17c of the urea water tank 16.

[0023] Also, although not shown in the drawings, the injection nozzle is connected to the upper part of the urea water return pipe 26 via a pipe of a different system from the pipe on the urea water suction pipe 25 side, and the urea water return pipe 26 opens at an upper position inside the tank body 17 via the base part 24.

[0024] The upper parts of the cooling water introduction pipe 27a and the cooling water discharge pipe 27b protruding from the base part 24 are connected to the cooling circuit of the engine 13 via pipes not shown in the drawings, respectively. Inside the tank body 17, the cooling water introduction pipe 27a and the cooling water discharge pipe 27b extend downward from the base part 24, respectively, and are bent at a right angle to the right near the bottom surface 17c of the tank body 17, and are connected to each other via a return pipe 27c forming a substantially U shape directly below the filter 30.

[0025] Note that since the configuration of the cooling circuit of the engine 13 is well-known, details will not be described. However, it is a system in which cooling water is circulated through the cooling circuit formed between the engine 13 and the radiator to cool the engine 13 and the radiator dissipates the heat of the temperature-risen cooling water. Therefore, a part of the cooling water circulating through the cooling circuit circulates through the cooling water pipe 27 of the urea water supply and thawing unit 23.

[0026] Inside the tank body 17, the float guide pipe 28 extends downward from the base part 24, and its lower end is located near the bottom surface 17c of the tank body 17. Although not shown in the drawings, a reed switch is accommodated inside the float guide pipe 28, and is electrically connected to a control device (not shown) of the hydraulic excavator 1 via the upper part of the float guide pipe 28 protruding from the base part 24. A float 32 with a built-in magnet (not shown) is fitted into the float guide pipe 28 so as to be movable in the vertical direction, and the vertical position of the float 32 changes corresponding to the liquid level of the urea water inside the tank body 17. The float guide pipe 28 and the float 32 constitute a liquid level sensor 33 for detecting the storage amount of the urea water as one of the sensors, and a detection signal corresponding to the vertical position of the float 32 is input from the reed switch to the control device.

[0027] Inside the tank body 17, the harness pipeline 29 extends downward from the base portion 24 and is bent in a crank shape slightly to the right. At its lower end, a temperature and concentration sensor 34 for detecting the temperature and concentration of the aqueous urea solution is connected as one of the sensors. The lower part of the temperature and concentration sensor 34 is connected to the lower end of the float guide pipeline 28 via a bracket 35. Although not shown in the figure, the harness of the temperature and concentration sensor 34 extends upward inside the harness pipeline 29 and is electrically connected to the control device via the upper part of the harness pipeline 29 protruding from the base portion 24, and a detection signal corresponding to the temperature and concentration of the aqueous urea solution is input to the control device.

[0028] The control device executes the control of the above-described hydraulic control unit, the operation control of the engine 13, the control of the exhaust gas treatment device 14 including the injection nozzle of the SCR catalyst, etc. For example, the temperature and concentration of the aqueous urea solution are used for processes such as calculating the injection amount of the aqueous urea solution from the injection nozzle, and the storage amount of the aqueous urea solution is used for warning processes to the operator when the remaining amount is insufficient.

[0029] FIG. 5 is a sectional view taken along line V-V of FIG. 3 showing the aqueous urea solution supply and thawing unit, and FIG. 6 is a sectional view taken along line VI-VI of FIG. 3 showing the aqueous urea solution supply and thawing unit. In the plan view shown in FIG. 5, the aqueous urea solution suction pipeline 25 and the cooling water introduction pipeline 27a are arranged adjacent to each other on the left and right. At a front position spaced apart from these pipelines 25, 27a by a predetermined distance, the aqueous urea solution return pipeline 26 and the cooling water discharge pipeline 27b are arranged in a position relationship adjacent to each other on the left and right. The harness pipeline 29 is arranged at the central position within the predetermined distance separated before and after, and the float guide pipeline 28 is arranged at a position separated to the left from the harness pipeline 29.

[0030] While maintaining such a positional relationship, each of the pipelines 25, 27a, 27b, 28, 29 (excluding the aqueous urea solution return pipeline 26 and the lower side of the bent portion of the harness pipeline 29) extends parallel in the vertical direction. Note that the reason for arranging the aqueous urea solution suction pipeline 25 adjacent to the cooling water introduction pipeline 27a is to promote the thawing of the aqueous urea solution to some extent by direct heat transfer from the cooling water introduction pipeline 27a to the aqueous urea solution suction pipeline 25.

[0031] The vertically extending portions of the urea aqueous solution suction pipe 25, the cooling water introduction pipe 27a, the cooling water discharge pipe 27b, and the harness pipe 29 are connected to each other by clamp fittings 36 at two positions in the vertical direction while maintaining the above-described positional relationship. Specifically, as shown in FIG. 5, the clamp fitting 36 is formed by bending a single metal plate so as to surround each of the pipes 25, 27a, 27b, 29, and the front and rear portions thereof are fastened by bolts 37 and nuts 38 to sandwich each of the pipes 25, 27a, 27b, 29. The clamp fitting 36 is curved in an arc shape following the outer peripheral surfaces of the respective pipes 25, 27a, 27b, 29, thereby restricting the movement of each of the pipes 25, 27a, 27b, 29 and maintaining the desired positional relationship. Note that the clamp fitting 36 also serves to increase the heat dissipation area by coming into contact with the cooling water introduction pipe 27a and the cooling water discharge pipe 27b.

[0032] All the members constituting the urea aqueous solution supply / thawing unit 23 are disposed in the tank body 17 while being supported from the base portion 24. Since the insertion / removal hole 22 is formed to have a size through which the urea aqueous solution supply / thawing unit 23 can pass, for example, maintenance and inspection of the urea aqueous solution supply / thawing unit 23 are carried out after taking out the urea aqueous solution supply / thawing unit 23 from inside the tank body 17 through the insertion / removal hole 22.

[0033] [Operating state of the urea aqueous solution supply / thawing unit 23] Next, the operating state of the urea aqueous solution supply / thawing unit 23 configured as described above will be described. When the operation of the engine 13 is started, the urea aqueous solution pump operates, and the urea aqueous solution in the tank body 17 is sucked from the suction portion 31 of the urea aqueous solution suction pipe 25, and is supplied to the injection nozzle through the urea aqueous solution suction pipe 25 and the pipe. The urea aqueous solution is injected from the injection nozzle into the exhaust passage of the engine 13, and the reduction action of NOx in the exhaust gas is exerted on the SCR catalyst. Further, the surplus urea aqueous solution that has not been injected from the injection nozzle is returned into the tank body 17 through the pipe and the urea aqueous solution return pipe 26.

[0034] In parallel with this, during the operation of the engine 13, the cooling water circulates through the cooling circuit, and a part of it is guided through a pipe to the cooling water introduction pipe 27a of the aqueous urea supply / thawing unit 23. The cooling water flows from the cooling water introduction pipe 27a through the return pipe 27c to the cooling water discharge pipe 27b, and then returns to the cooling circuit of the engine 13 through a pipe. When the aqueous urea in the aqueous urea tank 16 freezes in a cold region or the like, the heat of the cooling water flowing through the cooling water pipe 27 is transmitted to the frozen aqueous urea, whereby the aqueous urea is thawed and the supply to the injection nozzle is started.

[0035] In the aqueous urea tank described in Patent Document 1, since a cooling water pipe shape suitable for uniform thawing of the aqueous urea is adopted, the aqueous urea in the useless area is also thawed, resulting in a problem that the thawing of the aqueous urea in the important area is delayed. In order to solve such a problem, in the present invention, a heat insulation cover 40 for preferentially thawing the aqueous urea in the important area is provided in the aqueous urea supply / thawing unit 23, and the details thereof will be described below.

[0036] [Configuration of Heat Insulation Cover 40] As a whole, the heat insulation cover 40 extends vertically along the pipes 25, 27a, 27b, 28, 29 in the aqueous urea tank 16. Specifically, as shown in FIGS. 3 and 4, the heat insulation cover 40 is disposed corresponding to the vertically extending portions (linear regions) of the aqueous urea suction pipe 25, the cooling water introduction pipe 27a, and the cooling water discharge pipe 27b. Its upper end is higher than the liquid level corresponding to the maximum storage amount, and its lower end is located near the suction portion 31 of the aqueous urea suction pipe 25.

[0037] Also, as shown in FIG. 6, the heat insulation cover 40 as a whole is in the shape of a plate extending in the vertical direction and has an arc shape, surrounding the periphery of the float guide pipe 28 and the float 32 from the left in a plan view. The rear side portion 40r (corresponding to the "one side portion" of the present invention) of the heat insulation cover 40 extends to the urea water suction pipe 25 and the cooling water introduction pipe 27a, and rear locking claws 41r (corresponding to the "locking portion" of the present invention) are formed at two positions above and below. The front surface of each rear locking claw 41r is concave, and due to the elasticity of the heat insulation cover 40, it is locked to the outer peripheral surface of the cooling water introduction pipe 27a and the outer peripheral surface of the urea water suction pipe 25. As a result, displacement of the rear locking claw 41r forward, leftward, and rightward is restricted.

[0038] In addition, the front side portion 40f (corresponding to the "other side portion" of the present invention) of the heat insulation cover 40 extends along the arc cross-section to the cooling water discharge pipe 27b, and front locking claws 41f (corresponding to the "locking portion" of the present invention) are formed at two positions above and below. The rear surface of each front locking claw 41f is concave, and due to the elasticity of the heat insulation cover 40, it is locked to the outer peripheral surface of the cooling water discharge pipe 27b. As a result, displacement of the front locking claw 41f rearward, leftward, and rightward is restricted.

[0039] Also, as shown in FIG. 4, the upper front locking claw 41f and the rear locking claw 41r are in contact with the upper clamp fitting 36 located directly below to restrict downward displacement, and the lower front locking claw 41f and the rear locking claw 41r are in contact with the lower clamp fitting 36 located directly above to restrict upward displacement. As a result, the heat insulation cover 40 is supported in a state of maintaining a desired positional relationship with respect to the urea water suction pipe 25, the cooling water introduction pipe 27a, and the cooling water discharge pipe 27b via the front locking claw 41f and the rear locking claw 41r.

[0040] The positional relationship regarding the heat insulation cover 40 will be described in more detail. As shown in the plan view of FIG. 6, the rear side portion 40r and the front side portion 40f of the heat insulation cover 40 having a semi-circular cross-section are spaced apart in the front-rear direction. In the region spaced apart in the front and rear, the urea water suction pipeline 25 and the cooling water introduction pipeline 27a are arranged in the vicinity of the rear side portion 40r, and the cooling water discharge pipeline 27b is arranged in the vicinity of the front side portion 40f.

[0041] As a result, the heat insulation cover 40 is located on the left side in FIG. 6, and the cooling water introduction pipeline 27a, the urea water suction pipeline 25, and the cooling water discharge pipeline 27b are all arranged on the right side in FIG. 6, that is, on the same side with respect to the heat insulation cover 40. In other words, the heat insulation cover 40 is arranged such that the inner surface 40a (corresponding to the "one side surface" of the present invention) of the semi-circular cross-section faces the vertical extension portions of the urea water suction pipeline 25, the cooling water introduction pipeline 27a, and the cooling water discharge pipeline 27b from the left side.

[0042] [Function and Effect of the Heat Insulation Cover 40] The urea water in the urea water tank 16 is sucked from the suction portion 31 and supplied to the injection nozzle through the urea water suction pipeline 25. Therefore, when the urea water in the urea water tank 16 is frozen, quickly thawing the urea water inside the urea water suction pipeline 25 including the suction portion 31 and the urea water around the suction portion 31 leads to a rapid supply to the injection nozzle. On the other hand, the heat source for thawing the urea water is the cooling water pipeline 27 through which cooling water flows inside. Therefore, it is important to transfer the heat radiated from the cooling water pipeline 27 to the inside of the urea water suction pipeline 25 and the suction portion 31 and the periphery of the suction portion 31 without waste, giving priority over other regions where early thawing is not required.

[0043] When the heat insulation cover 40 is arranged in the positional relationship as described above, part of the heat radiated from the cooling water introduction pipe 27a and the cooling water discharge pipe 27b is blocked by the heat insulation cover 40. Stating the effect of the heat insulation cover 40 at this time, in a plan view, heat is radiated from the cooling water introduction pipe 27a and the cooling water discharge pipe 27b in all 360° directions. For example, the heat radiated to the right shown by the arrow A in FIGS. 3 and 6 is consumed for thawing the urea aqueous solution located on the right as it is because there is no heat insulation cover 40 in that direction.

[0044] On the other hand, the heat radiated to the left shown by the arrow B should originally be consumed for thawing the urea aqueous solution located on the left. However, the radiated heat is blocked by the heat insulation cover 40 and is not consumed for thawing the urea aqueous solution in the area to the left of it, and the heat in other directions increases by that amount. Not only in the direction of the arrow B, but all the heat radiated toward the heat insulation cover 40 is blocked, increasing the heat in other directions and thus being consumed for thawing the urea aqueous solution located in other directions. Note that the arrow B in FIGS. 3 and 6 does not represent the actual heat reflection path, but conceptually represents the situation where the heat radiated to the left is blocked by the heat insulation cover 40, increasing the heat to the right.

[0045] For the heat insulation cover 40, the vertically extending portions of the cooling water introduction pipe 27a and the cooling water discharge pipe 27b are arranged on the right side, and similarly, the vertically extending portion of the urea aqueous solution suction pipe 25 is also arranged on the right side. That is, since the urea aqueous solution suction pipe 25 is located in the region where the heat increases (mainly the region to the right of the heat insulation cover 40) due to the arrangement of the heat insulation cover 40, the amount of heat transfer to the urea aqueous solution suction pipe 25 increases.

[0046] For this reason, the aqueous urea inside the aqueous urea suction pipeline 25 is rapidly thawed, and the heat of the aqueous urea suction pipeline 25 with the increased temperature is transmitted to the suction part 31, so that the aqueous urea inside the suction part 31 and the surrounding aqueous urea are also rapidly thawed. Then, the thawed aqueous urea is sucked from the suction part 31 and supplied to the injection nozzle through the aqueous urea suction pipeline 25 and the pipe. Therefore, the SCR catalyst can function quickly and the operation of the hydraulic excavator 1 can be started.

[0047] In this embodiment, the aqueous urea suction pipeline 25 extends vertically on the right side of the heat insulation cover 40, and its lower end bends at a right angle to the right to form the suction part 31. As a result, in plan view, the suction part 31 extends in a direction away from the heat insulation cover 40 along the bottom surface 17c of the tank body 17. Therefore, since this suction part 31 is also located in the region where the heat increases due to the action of the heat insulation cover 40, the aqueous urea inside the suction part 31 and the surrounding aqueous urea can be thawed more quickly.

[0048] On the other hand, during the operation of the hydraulic excavator 1, the aqueous urea in the aqueous urea tank 16 is constantly agitated by the vibration accompanying the work. For this reason, as shown in FIGS. 3 and 6, when the liquid level of the aqueous urea is relatively high, the water supply filter 20 attached to the replenishment port 18 floats on the liquid surface and drifts on the liquid surface with the agitation of the aqueous urea. Since the liquid level sensor 33 is disposed in the vicinity of the right side of such a water supply filter 20, there is a possibility that the water supply filter 20 interferes with the float 32 and causes false detection.

[0049] In this embodiment, the float 32 is disposed on the right side of the heat insulation cover 40, that is, on the same side as the aqueous urea suction pipeline 25, the cooling water introduction pipeline 27a, and the cooling water discharge pipeline 27b. On the contrary, the water supply filter 20 is disposed on the left side of the heat insulation cover 40, that is, on the opposite side of the float 32 with the heat insulation cover 40 interposed therebetween. Therefore, since the interference of the water supply filter 20 with the float 32 is avoided by the heat insulation cover 40, another effect of preventing false detection of the liquid level and improving the detection accuracy can be obtained.

[0050] Particularly in this embodiment, since the heat insulation cover 40 is formed in a semi-circular cross-section surrounding the float 32 from the left, interference with the float 32 can be reliably prevented regardless of the state in which the water supply filter 20 is floating.

[0051] Also, in the plan view shown in FIG. 6, the urea water suction pipe 25, the cooling water introduction pipe 27a, and the cooling water discharge pipe 27b are arranged at intervals in the front-rear direction, and the heat insulation cover 40 is supported by using these pipes 25, 27a, 27b. Specifically, by utilizing the elasticity of the heat insulation cover 40, the rear locking claws 41r on the rear side portion 40r are locked to the urea water suction pipe 25 and the cooling water introduction pipe 27a, and the front locking claws 41f on the front side portion 40f are locked to the cooling water discharge pipe 27b.

[0052] By fixing the front side portion 40f and the rear side portion 40r corresponding to both ends of the heat insulation cover 40 to the pipes 25, 27a, 27b respectively, the heat insulation cover 40 is firmly and stably supported. Although the heat insulation cover 40 is constantly subjected to force with the stirring of the urea water in the urea water tank 16, since the heat insulation cover 40 is maintained in the expected positional relationship with respect to each of the pipes 25, 27a, 27b, the above-described effects regarding the thawing of the urea water can be reliably achieved.

[0053] In addition, in this embodiment, since the locking claws 41f, 41r are used as the fixing structure of the heat insulation cover 40 for each of the pipes 25, 27a, 27b, the assembly thereof is easy. In the assembly work of the urea water supply and thawing unit 23, for example, when the assembly of other members is completed and the heat insulation cover 40 is fixed last, the heat insulation cover 40 is arranged so as to surround the float 32 from the left side of FIG. 6. Naturally, the rear locking claws 41r are locked to the urea water suction pipe 25 and the cooling water introduction pipe 27a, and the front locking claws 41f are locked to the cooling water discharge pipe 27b. At the same time, the vertical displacement of the heat insulation cover 40 in the vertical direction is restricted by the upper and lower clamp fittings 36. Therefore, the fixing of the heat insulation cover 40 can be completed by such a simple operation.

[0054] In addition, each pipeline 25, 27a, 27b used for fixing the heat insulation cover 40 and the clamp fitting 36 for fixing the same are existing members provided in the urea water supply and thawing unit 23. Therefore, since it is not necessary to add a new member for fixing the heat insulation cover 40, it can be implemented without increasing the manufacturing cost of the urea water supply and thawing unit 23.

[0055] With the above, the description of the embodiment is completed. However, the aspects of the present invention are not limited to this embodiment. For example, in the above embodiment, it is embodied in the urea water tank 16 of the hydraulic excavator 1, but the construction machine targeted is not limited to this. For example, it can be arbitrarily changed to a bulldozer, a wheel loader, etc. The routing of each pipeline 25, 27a, 27b of the urea water supply and thawing unit 23, or the types of sensors 33, 34, etc. are not limited to the above embodiment and can be arbitrarily changed.

[0056] Also, in the above embodiment, the heat insulation cover 40 is formed in a semi-circular cross-section, and a rear locking claw 41r is formed on its rear side portion 40r to be locked to the urea water suction pipeline 25 and the cooling water introduction pipeline 27a, and a front locking claw 41f is formed on the front side portion 40f to be locked to the cooling water discharge pipeline 27b. Thereby, in a plan view, a positional relationship is realized in which the urea water suction pipeline 25, the cooling water introduction pipeline 27a, and the cooling water discharge pipeline 27b are arranged on the same side with respect to the heat insulation cover 40, but it is not limited to this.

[0057] For example, regarding the shape of the heat insulation cover 40, it may be a flat plate shape instead of a semi-circular cross-section. Also in this case, the urea water suction pipeline 25, the cooling water introduction pipeline 27a, and the cooling water discharge pipeline 27b may be arranged on the same side with respect to the plate-shaped heat insulation cover. In other words, the heat insulation cover may be arranged so that the flat one side faces each other for each pipeline 25, 27a, 27b. Regarding the area of the heat insulation cover 40 in the vertical direction, it is not limited to the above embodiment. For example, in order to further promote the thawing of the urea water around the suction section 31, the heat insulation cover 40 shown in FIG. 3 may be extended further downward.

[0058] Regarding the fixing method of the heat insulation cover 40, the heat insulation cover 40 may be fixed using a binding band or the like instead of the latching claws 41f and 41r. Further, regarding the object to which the heat insulation cover 40 is fixed, it is not necessarily required to be fixed to each of the pipe lines 25, 27a, and 27b, and the heat insulation cover 40 may be fixed to another member. For example, it may be supported from the top surface 17b of the tank body 17 via a bracket, or supported from the bottom surface 17c via a bracket. In any case, compared with the embodiment, the positional relationship between the heat insulation cover 40 and each of the pipe lines 25, 27a, and 27b can be set more freely.

Explanation of Signs

[0059] 1 Hydraulic excavator (construction machine) 13 Engine 14 Exhaust gas treatment device 16 Urea water tank 17 Tank body 18 Filling port 20 Water supply filter 23 Urea water supply and thawing unit 25 Urea water suction pipe line 27 Cooling water pipe line 27a Cooling water introduction pipe line 27b Cooling water discharge pipe line 27c Return pipe line 31 Suction section 32 Float 33 Liquid level sensor (sensors) 34 Temperature and concentration sensor (sensors) 40 Heat insulation cover 40a Inner surface (one side surface) 40f Front side portion (other side portion) 40r Rear side portion (one side portion) 41f Front latching claw (latching portion) 41r Rear latching claw (latching portion)

Claims

1. In a urea water tank of a construction machine that stores urea water supplied to an exhaust gas treatment device provided in an engine in a tank body, a urea water supply and thawing unit including a urea water suction pipe that extends vertically in the tank body and has a suction section provided at a lower part thereof, and supplies the urea water sucked up from the suction section to the exhaust gas treatment device, a cooling water pipe that extends vertically in the tank body and circulates cooling water from the engine, and sensors that detect the state of the urea water in the tank body; a heat insulation cover disposed with one side facing each of the vertically extending portions of the urea water suction pipe and the cooling water pipe; and comprising, the sensors include a liquid level sensor having a float that changes its vertical position corresponding to the liquid level of the urea water, a replenishment port for replenishing urea water from the outside is opened in the tank body and a water supply filter is connected, the water supply filter is disposed on the side opposite to the float with the heat insulation cover interposed therebetween, which is a urea water tank of a construction machine.

2. In a urea water tank of a construction machine that stores urea water supplied to an exhaust gas treatment device provided in an engine in a tank body, a urea water supply and thawing unit including a urea water suction pipe that extends vertically in the tank body and has a suction section provided at a lower part thereof, and supplies the urea water sucked up from the suction section to the exhaust gas treatment device, a cooling water pipe that extends vertically in the tank body and circulates cooling water from the engine, and sensors that detect the state of the urea water in the tank body; a heat insulation cover disposed with one side facing each of the vertically extending portions of the urea water suction pipe and the cooling water pipe; and comprising, the suction section is bent substantially at a right angle from the lower end of the vertically extending portion of the urea water suction pipe, and in plan view, extends along the bottom surface of the tank body in a direction away from the heat insulation cover which is a urea water tank of a construction machine.

3. the cooling water pipe comprises a cooling water introduction pipe and a cooling water discharge pipe that each extend vertically in the urea water tank, and a return pipe that connects the lower parts of the cooling water introduction pipe and the cooling water discharge pipe to each other, the heat insulation cover is plate-shaped, In a plan view, the heat shield cover is arranged such that one surface thereof faces the cooling water introduction pipeline, the cooling water discharge pipeline, and the urea aqueous solution suction pipeline. The urea aqueous solution tank for a construction machine according to claim 1 or 2, characterized in that.

4. Hooking portions are respectively provided on one side portion and the other side portion of the heat shield cover, and each hooking portion is hooked on any one of the cooling water introduction pipeline, the cooling water discharge pipeline, and the urea aqueous solution suction pipeline. The urea aqueous solution tank for a construction machine according to claim 3, characterized in that.

5. In a plan view, the heat shield cover has a semi-circular cross section and surrounds the periphery of the float. The urea aqueous solution tank for a construction machine according to claim 1, characterized in that.

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