Urea water supply system

Abstract

To solve a problem that a conventional tractor uses a tank in which urea water is stored to purify exhaust gas from an engine, however, the urea water in the urea water tank becomes deteriorated due to freezing or overheating.SOLUTION: A urea water supply system includes: a urea water tank 4 which stores urea water; a dosing module 5 which jets urea water supplied from the urea water tank 4 to exhaust gas exhausted from an engine 1; and a deterioration prevention mechanism P which keeps a temperature of the urea water in the urea water tank 4 at a proper temperature.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a urea water supply system for a vehicle such as a tractor equipped with a DPF device or an SCR device. [Background technology]

[0002] Conventionally, a mechanism for purifying exhaust gas using urea water is known. For example, Patent Document 1 discloses that urea water in a urea water tank is pumped from a urea water injection pump to a urea water injection nozzle, the urea water is injected from the urea water injection nozzle into a urea mixing tube, the urea water from the urea water injection nozzle is mixed with exhaust gas from a diesel engine inside the urea mixing tube, the exhaust gas mixed with the urea water passes through a second case (SCR catalyst, oxidation catalyst), nitrogen oxides (NOx) in the exhaust gas are reduced, and the exhaust gas is released to the outside from an SCR outlet tube. That is, it is disclosed that ammonia gas is generated in the exhaust gas by hydrolysis by spraying urea water into the exhaust gas, the ammonia gas is mixed with the exhaust gas and introduced into the second case from the SCR inlet tube, and the nitrogen oxides (NOx) in the exhaust gas are removed by the catalyst in the second case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-151764 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in such vehicles, there is a problem that the urea water is not maintained at an appropriate temperature, and in particular, the urea water in the urea water tank freezes or overheats, which causes the urea water to deteriorate.

[0005] In consideration of such problems, the present invention has an object to provide a urea water supply system capable of maintaining the urea water in the urea water tank at an appropriate temperature. [Means for solving the problem]

[0006] The first aspect of the present invention is a urea water tank for storing urea water; a dosing module that injects urea water supplied from the urea water tank into exhaust gas discharged from an engine; and a deterioration prevention mechanism for maintaining the temperature of the urea water in the urea water tank at an appropriate temperature.

[0007] The second aspect of the present invention is The deterioration prevention mechanism is a urea water supply system according to the first aspect of the present invention, which has a heat sink for cooling attached to the urea water tank and an electric fan for air-cooling the heat sink.

[0008] The third aspect of the present invention is In the second urea water supply system of the present invention, the deterioration prevention mechanism is configured such that a coolant circuit through which coolant from the engine flows passes through the urea water tank.

[0009] The fourth aspect of the present invention is a cooling water circuit through which cooling water from the engine flows is branched, and the two branch circuits are arranged in parallel such that one branch circuit passes through the urea water tank via a valve and the other branch circuit passes through the dosing module, The third aspect of the present invention is a urea water supply system, further comprising a control unit that controls the valve to be opened when the engine is cold and to be closed after the engine is warmed up.

[0010] The fifth aspect of the present invention is The control unit After starting the engine, measuring the intake temperature of outside air; After starting the engine, the temperature at the DPF outlet is measured and accumulated. determining an activation state of the SCR catalyst from the integrated temperature, and operating a pump that supplies urea water from the urea water tank to the dosing module when it is determined that the activation temperature threshold has been reached; In a fourth aspect of the present invention, there is provided a urea water supply system, wherein a relationship between the activation temperature threshold value for each intake air temperature and the integrated temperature is recorded in advance.

[0011] The sixth aspect of the present invention is A pressure outlet pipe is provided on the intake pipe to the turbocharger. A sealed case having a spring-loaded piston built therein is connected to the pressure output pipe, a check valve is provided in an air pipe that communicates between the sealed case and an air cleaner of the intake pipe, and the sealed case is connected to the dosing module via a valve; A piston in the sealed case moves due to negative pressure of the turbocharger, and air from the air cleaner is stored in the sealed case through the air piping, This is a fifth aspect of the urea water supply system of the present invention, in which the valve is opened after the engine is stopped, and the air stored in the sealed case is supplied to the dosing module by the movement of the spring and piston.

[0012] The seventh aspect of the present invention is In the urea water supply system according to any one of the first to sixth aspects of the present invention, the deterioration prevention mechanism is a mechanism in which the urea water tank is formed in a rear fender of a vehicle having a hollow structure.

[0013] The eighth aspect of the present invention is Equipped with a DPF controller ECU and a urea SCR controller DCU, A seventh aspect of the present invention is a urea water supply system, comprising a control unit that transmits a signal from the DCU to the ECU to interrupt manual regeneration when the DPF inlet temperature is equal to or lower than a reference value and the SCR inlet temperature is higher than the DPF inlet by a specified value or more during manual regeneration of the DPF. Effect of the Invention

[0014] According to the present invention, it is possible to solve the problem of deterioration of the urea water due to freezing or overheating of the urea water in the urea water tank. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a urea water supply system according to an embodiment of the present invention; [Diagram 2] (A) and (B) Front views of the system, including the heat sink [Diagram 3] Cooling water circuit configuration diagram of the system [Figure 4] Diagram of the engine oil circuit of the system [Diagram 5] Diagram of the system's electric heater and other components [Figure 6] Layout of the radiator and other components of the system [Figure 7] Diagram of the system's transmission oil configuration [Figure 8] Layout of exhaust gas pipe 6 of the system [Figure 9] (A) and (B) Branching diagram of the engine cooling water circuit of the same system [Figure 10] (A) and (B) are a diagram and a flow chart showing the start of operation of the dosing module using temperature integration of the system. [Figure 11] (A) and (B) Schematic diagram of the turbocharger and other components of the system [Figure 12] A perspective view of the rear fender of the tractor using the same system. [Figure 13] Control-related configuration diagram of the ECU and DCU of the system (part 1) [Figure 14] Temperature graph of the DPF device and SCR device of the same system [Figure 15] Control-related configuration diagram of the ECU and DCU of the system (part 2) [Figure 16] Control-related configuration diagram of the ECU and DCU of the system (part 3) [Figure 17] Control-related configuration diagram of the ECU and DCU of the system (part 4) [Figure 18] Control-related configuration diagram of the ECU and DCU of the system (part 5) [Figure 19] (A) and (B) Schematic diagram of the urea water recovery system [Figure 20] (A) and (B) Cooling diagram of the dosing module of the same system. [Figure 21] (A), (B), and (C) Diagram showing thermostat, housing, and gasket [Figure 22] (A) and (B) Diagram showing gasket, hook and housing [Diagram 23] Top view of the gasket [Figure 24] FIG. 1 is a perspective view showing an oil filler plug that also serves as a relief valve for a head cover. [Diagram 25] A perspective view showing an oil filler valve that also serves as a relief valve for a gear case. [Figure 26] Relief valve cross section [Figure 27] Cross-section of another relief valve [Figure 28] (A) and (B) Perspective and cross-sectional views of a relief valve [Figure 29] (A) and (B) Cross-sectional view of the relief valve, perspective view of the internal parts, and perspective view of the relief valve [Diagram 30] Sectional view of relief valve and perspective view of internal parts [Diagram 31] Sectional view of relief valve and perspective view of internal parts [Diagram 32] (A) and (B) Cross-sectional view of the relief valve, perspective view of the internal parts, and perspective view of the relief valve [Diagram 33] (A) and (B) Cross-sectional view of the relief valve, perspective view of the internal parts, and perspective view of the relief valve DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0017] 1 is a schematic diagram of a portion of a tractor as an example of a work vehicle according to an embodiment of the present invention. In the following, forward / backward, left / right, and up / down are defined based on the traveling direction of the tractor.

[0018] In Fig. 1, exhaust gas discharged from a diesel engine 1 is introduced into a DPF device 2 through an exhaust gas pipe 6, and the exhaust gas purified by the DPF device 2 is introduced into an SCR device 3, where it is purified and discharged. Reference numeral 4 denotes a urea water tank that stores urea water, and the urea water therein is introduced into the SCR device 3 through a dosing module 5.

[0019] 2(A) and (B) show one embodiment of the present invention, in which a heat sink 7 is attached to the side of the urea water tank 4, and furthermore, an electric fan 8 blows air to the heat sink 7 using a battery 9 to dissipate heat from the urea water tank 4. The fins 7a of the heat sink 7 in Fig. 2(A) are arranged horizontally. Fig. 2(B) is also an embodiment, but differs from the example in Fig. 2(A) in that the fins 7a of the heat sink 7 are arranged vertically. These heat sinks 7 and the like are examples of the deterioration prevention mechanism P of the present invention.

[0020] 3 shows one embodiment of the present invention, in which a coolant circuit 10 for the coolant discharged from the engine 1 is led into the urea water tank 4. Since the coolant discharged from the engine 1 is warm, this arrangement allows the urea water in the urea water tank 4 to be maintained at an appropriate temperature and prevents freezing. In other words, since the LLC of the engine 1 coolant does not freeze, this effect can be utilized to prevent the urea water from freezing. The coolant circuit 10 and the like are one example of the deterioration prevention mechanism P of the present invention.

[0021] 4 shows one embodiment of the present invention, in which engine oil from the engine 1 is led into the urea water tank 4. The engine oil of the engine 1 does not freeze, so this is utilized. In this way, the urea water in the urea water tank 4 is maintained at an appropriate temperature and freezing can be prevented. This engine oil is one example of the deterioration prevention mechanism P of the present invention.

[0022] 5 shows one embodiment of the present invention, in which an electric heater is removed from the battery 9 and introduced into the urea water tank 4 to heat the urea water and prevent it from freezing. These electric heaters are one example of the deterioration prevention mechanism P of the present invention.

[0023] 6 shows one embodiment of the present invention, in which the urea water tank 4 is disposed behind the radiator 11. The urea water is prevented from freezing by directing the heat of the radiator 11 to the urea water tank 4 with an engine fan 12. The arrangement of the radiator 11 and other components is one example of the deterioration prevention mechanism P of the present invention.

[0024] 7 shows one embodiment of the present invention, in which the oil of a vehicle transmission 13 is guided to the urea water tank 4 to prevent the urea water from freezing. The oil does not freeze, so this property is utilized. Such transmission oil is one example of the deterioration prevention mechanism P of the present invention.

[0025] 8 shows one embodiment of the present invention, in which an exhaust gas pipe 6 from an engine 1 is arranged around a urea water tank 4, and radiant heat from the exhaust gas pipe 6 is used to prevent the urea water from freezing. The arrangement of the exhaust gas pipe 6 is one example of the deterioration prevention mechanism P of the present invention.

[0026] 9(A) and (B) show one embodiment of the present invention, in which a cooling water circuit 10 for flowing cooling water from the engine 1 passes through the inside of the urea water tank 4, but the cooling water circuit 10 for flowing cooling water from the engine 1 is branched, with one branch circuit 10a passing through the inside of the urea water tank 4 via a valve 14, and the other branch circuit 10b being arranged in parallel so as to pass through the dosing module 5. These branch circuits 10a, 10b are one example of the deterioration prevention mechanism P of the present invention.

[0027] 9(A) shows the state when the engine is cold, and FIG.9(B) shows the state after the engine has been warmed up. As shown in (A), when the engine is cold, the valve 14 is opened, and cooling water is circulated to the urea water tank 4 side to melt the frozen urea water by reducing the amount of cooling water to the dosing module 5.

[0028] During warm-up, the valve 14 is closed, the supply of cooling water to the urea water tank 4 is stopped so as not to raise the temperature of the urea water, and the supply of cooling water to the dosing module 5 is increased. The opening and closing of such valve 14 is performed by the control unit 15. Note that in Figures 9(A) and (B), the thickness of the arrows indicating the flow of cooling water corresponds to the flow rate.

[0029] FIG. 10 shows one embodiment of the present invention, where (A) is a configuration and (B) is a flow chart explaining the operation.

[0030] In FIG. 10, the control unit 15 records in advance the relationship between the activation temperature threshold value for each intake air temperature of the engine 1 and the integrated temperature in a mapped form.

[0031] Then, the control unit 15 measures the outside air intake temperature after the engine is started (step S1), reads the above map (step S2), measures and accumulates the temperature at the outlet of the DPF device 2 after the engine is started (step S3), judges the activity status of the SCR catalyst from the accumulated temperature, and if it determines that the corresponding activation temperature threshold has been reached (step S4), immediately operates the pump 16 that supplies urea water from the urea water tank 4 to the dosing module 5 (step S5), and starts the operation of the dosing module 5 (step S6).

[0032] Originally, because urea water could not be injected until the SCR catalyst was activated, there was a problem in the past where the urea water would accumulate in the dosing module 5 and become heated and crystallized. However, by doing as described above, the pump 16 is operated immediately when the activation temperature is reached, preventing the urea water from crystallizing.

[0033] Figures 11(A) and (B) show one embodiment of the present invention, in which a pressure outlet pipe 23 is provided in an intake pipe 18 to a turbocharger 19, and a sealed case 20 incorporating a piston 20b with a spring 20a is connected to the pressure outlet pipe 23.

[0034] A check valve 22 is provided in an air pipe 21 that communicates between the sealed case 20 and the air cleaner 17 of the intake pipe 18. The sealed case 20 is also connected to the dosing module 5 via a valve 14.

[0035] 11(A), the negative pressure of the turbocharger 19 moves a piston 20b in the sealed case 20, causing air from the air cleaner 17 to accumulate inside the sealed case 20 through the air piping 21. That is, the piston 20b divides the inside of the sealed case 20 into a chamber on the turbocharger 19 side and a chamber on the air cleaner 17 side, and a spring 20a is disposed in the chamber on the turbocharger 19 side to constantly urge the piston 20b toward the chamber on the air cleaner 17 side.

[0036] Then, the air in the chamber on the turbocharger 19 side is drawn out by the negative pressure caused by the operation of the turbocharger 19, so that the piston 20b moves toward the turbocharger 19 side and takes in air from the air cleaner 17 into the chamber on the air cleaner 17 side. Note that the valve 14 is closed.

[0037] In this state, when the engine 1 stops, the valve 14 is opened, and as shown in Fig. 11(B), the piston 20b moves toward the air cleaner 17 by the biasing force of the spring 20a, and the air stored in the chamber on the air cleaner 17 side of the sealed case 20 is supplied to the dosing module 5. At that time, the check valve 22 prevents the movement of air.

[0038] Originally, if urea water remains in the urea water piping or dosing module 5 after operation, there is a problem that the urea will crystallize in the piping and cause the dosing module 5 to not operate normally. However, with the above-described configuration, the valve 14 is opened after the engine 1 is stopped, and the movement of air can blow away the remaining urea water, preventing the urea from crystallizing in the dosing module 5.

[0039] Fig. 12 shows one embodiment of the present invention, in which the rear fender 25 of the tractor 24 constitutes the urea water tank 4. In other words, this is a mechanism in which the urea water tank 4 is constituted by the rear fender 25 of the tractor 24, which is formed into a hollow structure by blow molding of resin. Originally, in agricultural tractors, the urea water tank 4 is often laid out next to the transmission under the driver's seat, but this causes a problem of it becoming hot when exposed to exhaust air from the radiator. However, with the above-mentioned configuration, more space is created in the vehicle body, and problems caused by heat can be prevented. Such a rear fender 25 that also serves as the urea water tank 4 is one example of the deterioration prevention mechanism P of the present invention.

[0040] Fig. 13 shows an embodiment for preventing the poisoning of the SCR catalyst by HC. Two controllers are provided: a DPF controller ECU and a urea SCR controller DCU.

[0041] The control unit is configured to transmit a signal from the DCU to the ECU to interrupt manual regeneration if the DPF inlet temperature is below a reference value and the SCR inlet temperature is higher than the DPF inlet by a specified value or more for a specified period of time during manual regeneration of the DPF device 2.

[0042] That is, as shown in FIG. 14, if there is an abnormality in the DOC of the DPF device 2, and the post-injection (HC) during DPF regeneration cannot be oxidized by the DOC and slips, the HC reacts with the oxidation catalyst applied to the DPF, causing the temperature at the SCR inlet to rise significantly, and the SCR may become poisoned by HC.

[0043] In such a case, the DCU sends a CAN signal to the ECU to interrupt manual regeneration as described above. In other words, the DCU issues a regeneration prohibition command to the DPF control logic implemented by the ECU to prevent the SCR from becoming HC-poisoned.

[0044] FIG. 15 shows a case where the engine is equipped with a DPF controller ECU and a urea SCR controller DCU, and when an operating condition in the low load and low speed range continues for a specified time or longer, the control unit 15 transmits a CAN signal from the DCU to the ECU to prohibit automatic regeneration of the DPF.

[0045] In the case of automatic DPF regeneration, there is a possibility that urea deposition in the SCR may not be sufficiently removed, but by doing as described above, it is possible to effectively prevent urea deposition in the SCR simply by manipulating the CAN signal sent from the DCU, without changing the DPF control logic implemented by the ECU.

[0046] FIG. 16 shows a system equipped with a DPF controller ECU and a urea SCR controller DCU. When the temperature at the SCR inlet remains below a specified value for a specified period of time or longer, the DCU sends a CAN signal to the ECU to prohibit automatic generation of the DPF.

[0047] Originally, with automatic DPF regeneration, there is a possibility that urea deposition in the SCR may not be sufficiently removed. However, with the above configuration, urea deposition in the SCR can be effectively prevented simply by manipulating the CAN signal sent from the DCU, without changing the DPF control logic implemented by the ECU.

[0048] FIG. 17 shows a case where the engine is equipped with a DPF controller ECU and a urea SCR controller DCU, and when an operating condition in the low load and low rotation range continues for a specified time or longer, the control unit 15 transmits a CAN signal from the DCU to the ECU requesting manual DPF regeneration at a higher temperature or for a longer time than normal.

[0049] Although manual regeneration may not be able to sufficiently remove urea deposition in the SCR, by doing as described above, the DCU can issue a regeneration command to the DPF control logic implemented by the ECU to more effectively prevent urea deposition in the SCR.

[0050] FIG. 18 shows a case in which the system is equipped with a controller ECU for DPF control and a controller DCU for urea SCR control, and when the temperature at the SCR inlet remains below a specified value for a specified period of time or longer, the control unit 15 sends a CAN signal from the DCU to the ECU requesting manual DPF regeneration at a temperature higher than normal or for a longer period of time.

[0051] Although manual regeneration may not be able to sufficiently remove urea deposition in the SCR, by doing as described above, the DCU can issue a regeneration command to the DPF control logic implemented by the ECU to more effectively prevent urea deposition in the SCR.

[0052] 19(A) and (B) show another embodiment, which is equipped with an electronically controlled engine having a urea SCR system, and has a pump 16 and a switching valve 14 between the urea water tank 4 and the dosing module 5. The urea water tank 4, valve 14, pump 16, valve 14, and dosing module 5 are connected in this order by piping (Fig. 19(A)).

[0053] This valve 14 has four connection points, and is connected so that the downstream of the pump can be switched to the urea water tank 4 or the dosing module 5 by operating the valve.

[0054] When the engine is stopped, the valve 14 is switched so that the urea water tank 4 is connected downstream of the pump, and the pump 16 is driven (FIG. 19(B)).

[0055] Conventionally, there was a possibility that urea water would remain in the urea water piping and dosing module 5 after operation, and the urea would crystallize in the piping, causing the dosing module 5 to malfunction. However, by doing as described above, the valve 14 is switched and the pump 16 is driven after the engine is stopped, so that the urea water in the dosing module 5 and piping is returned to the urea water tank 4 and recovered, thereby preventing the urea from crystallizing in the piping.

[0056] 20(A) and (B) show another embodiment, in which an electric water pump 30 (WP) is driven to cool the dosing module 5 of the SCR device 3 after the engine is stopped (FIG. 20(A)). The average temperature inside the substrate of the SCR catalyst is estimated by a temperature sensor 31 attached to the inlet of the SCR catalyst. The drive time of the electric water pump 30 (WP) is controlled based on the average temperature inside the substrate of the SCR catalyst when the engine is stopped (FIG. 20(B)).

[0057] Conventionally, there was no clear guideline for the time to operate the water pump 30, but by doing as described above, it is possible to cool the dosing module 5 for a more appropriate period of time by controlling it based on the average temperature inside the substrate of the SCR catalyst, which is highly correlated with the temperature of the mounting part of the dosing module 5.

[0058] 21(A), (B), and (C) show another embodiment in which the coolant temperature is stipulated as a DPF regeneration condition for an engine 1 equipped with a DPF device 2. However, if the thermostat 32 is tilted by a water flow, a gap will form between the thermostat 32 and the housing 33. If there is a gap between the thermostat 32 and the housing 33 in extremely cold weather, the coolant will return to the radiator 11, it will take a very long time for the coolant temperature to rise, and a timeout error may occur even if regeneration is attempted.

[0059] Therefore, in this embodiment, a gap is formed between the thermostat 32 and the housing 33. The thermostat 32 is fixed with a gasket 34. Figure 21(A) is a plan view of the gasket 34, (B) is a cross-sectional view thereof, and (C) is a schematic diagram showing the relationship between the thermostat 32, the housing 33, and the gasket 34. 34a are bolt fastenings at three points.

[0060] Incidentally, gasket 34 has a front and back and will not function if assembled the other way around. Therefore, as shown in Figures 22(A) and (B), in order to prevent the installation direction from being mistaken, three hooks 37 are provided on gasket 34 (Figure 22(A)), and gasket 34 is fixed to housing 33 by hooks 37. Figure 22(B) is a cross-sectional view of one hook 37 of gasket 34, showing how gasket 34 is fixed to housing 33 by three hooks 37.

[0061] FIG. 23 shows another example for preventing the gasket 34 from being installed in the wrong direction, in which reverse-assembly prevention pins 38, 38 are provided on one side of the gasket 34 at unequal pitches near two of the three locations of the bolt fastening 34a.

[0062] Figure 24 shows another embodiment. In an engine 1 operating in extremely cold conditions, the CCV (oil separator) passage may freeze and become clogged. This may cause the internal pressure of the engine 1 to rise, which may cause seals to come off due to the pressure, and in the worst case scenario, may cause the engine oil to backflow and overrun. For this reason, it is desirable to provide a relief valve, but installing a relief valve in the passage requires space and complicated piping.

[0063] Therefore, in this example, a relief valve 39 is provided to prevent engine damage if the internal pressure rises significantly, but this relief valve 39 has its function in the oil plug 39 on the head cover. The opening pressure is set to 10 kPa, and the valve does not normally open. This makes it possible to prevent engine damage when the internal pressure rises during freezing.

[0064] FIG. 25 shows another embodiment in which an oil plug 39 of a gear case is provided with the function of a relief valve 39.

[0065] In engines operating in extremely cold conditions, the CCV passages may freeze and become clogged. This can cause the internal engine pressure to rise, which can cause seals to come off under pressure, and in the worst case scenario, can cause engine oil to backflow, resulting in overrun.

[0066] If the internal pressure rises significantly, it is desirable to install a relief valve to avoid engine damage, but installing a relief valve in the pipeline requires space and complicated piping, and installing it in the gear case can lead to oil splashes leaking and blocking the relief passage, making it difficult to adequately control the pressure.

[0067] Figure 26 shows another embodiment, in which in an engine 1 operating in extremely cold conditions, the CCV (oil separator) passage can freeze and block the passage. Blockage of the passage causes the internal pressure of the engine 1 to rise, which can cause seals to come off due to pressure, and in the worst case, there is a risk of overrun due to backflow of engine oil. Therefore, it is desirable to provide a splash guard, but installing a relief valve in the passage requires space and complicated piping, and installing it on the gear case can cause oil splashes to leak and block the relief passage, making it difficult to control the pressure.

[0068] Therefore, in this example, a relief valve 39 is provided to prevent engine damage if the internal pressure rises significantly, and this relief valve 39 has its function in the oil filler plug 39 on the head cover. This makes it possible to prevent engine damage when the internal pressure rises during freezing. Furthermore, a strainer is placed inside the relief valve to prevent oil from leaking out.

[0069] 26 is a cross-sectional view of the above-mentioned relief valve 39. Here, 40 is steel wool, 41 is glass wool, 42 is nonwoven fabric, and 43 is a spacer.

[0070] FIG. 27 shows another example in which steel wool 40 is installed.

[0071] 28(A) and (B) show another example, in which oil-repellent filter paper 45 is placed under steel wool 40, and further, a fall-prevention structure 46 is provided to prevent the filter paper 45 and the like from falling off.

[0072] Figures 29(A) and (B) show another embodiment. When the CCV and pipes freeze, the internal engine pressure rises, causing problems such as the oil seal blowing off and oil leaking. Therefore, if the engine gear case has an oil filler port, a valve cap 50 with a relief function that also serves as an oil filler cap is attached to prevent the internal pressure from rising when the CCV or pipes freeze. A splash guard 51 is attached to the valve cap 50, and an extension pipe 52 (Figure 29(B)) is also provided to prevent splashed oil from leaking out. The splash guard 51 is made of nylon 6 resin. Reference numeral 53 denotes a spring for release.

[0073] Figure 30 shows another example. Steel wool 40 is fitted into splash guard 51. Figure 31 also shows another example, in which splash guard 51 has a different shape.

[0074] In yet another example, a splash guard 51 can be attached to the valve cap 50 and steel wool can be added to the extension pipe 52 to prevent splashed oil from escaping to the outside.

[0075] Figures 32(A) and (B) show another embodiment. Here, the engine internal pressure rises due to freezing of the CCV and piping, causing problems such as the oil seal being blown off and oil leaking. If the engine gear case has an oil filler port, a valve cap 50 with a relief function that also serves as an oil filler cap is attached to prevent the internal pressure from rising when the CCV or piping freezes, but a splash guard 51 is attached to the valve cap 50, and steel is inserted inside the extension pipe 52 and splash guard 51 to prevent splashed oil from leaking out.

[0076] Figures 33(A) and (B) show modified examples of Figures 32(A) and (B), in which the shape of the splash guard 51 is different. [Industrial Applicability]

[0077] The urea water supply system of the present invention can prevent the urea water in the urea water tank from freezing or overheating, which would otherwise cause the urea water to deteriorate, and is therefore ideal for tractors, combine harvesters, and the like. [Explanation of symbols]

[0078] 1 Engine 2 DPF device 3 SCR device 4. Urea tank 5 Dosing Module 6 Exhaust gas pipe 7 Heat sink 8. Electric Fan 9 batteries 10 Cooling water circuit 10a One branch circuit 10b The other branch circuit 11 Radiator 12 Engine fan 13 Vehicle Mission 14 Valve 15 Control section 16 Pump 17 Air cleaner 18 Intake piping 19. Turbocharger 20 Sealed Case 20a spring 20b piston 21 Air piping 22 Check valve 23 Pressure extraction piping 24 Tractor 25 Rear fender DCU Urea SCR controller ECU DPF controller P Deterioration prevention mechanism

Claims

1. a urea water tank for storing urea water; a dosing module that injects urea water supplied from the urea water tank into exhaust gas discharged from an engine; and a deterioration prevention mechanism for maintaining a suitable temperature of the urea water in the urea water tank.

2. 2. The urea water supply system according to claim 1, wherein the deterioration prevention mechanism comprises a heat sink for cooling attached to the urea water tank, and an electric fan for cooling the heat sink.

3. 3. The urea water supply system according to claim 2, wherein the deterioration prevention mechanism is configured such that a coolant circuit through which coolant from the engine flows passes through the urea water tank.

4. a cooling water circuit through which cooling water from the engine flows is branched, and the two branch circuits are arranged in parallel such that one branch circuit passes through the urea water tank via a valve and the other branch circuit passes through the dosing module, 4. The urea water supply system according to claim 3, further comprising a control unit that controls the valve so as to open when the engine is cold and close the valve after the engine has warmed up.

5. The control unit After starting the engine, measuring the intake temperature of outside air; After starting the engine, the temperature at the DPF outlet is measured and integrated. determining an activity state of an SCR catalyst from the integrated temperature, and operating a pump that supplies urea water from the urea water tank to the dosing module when it is determined that the activation temperature threshold has been reached; 5. The urea water supply system according to claim 4, wherein a relationship between the activation temperature threshold value and the integrated temperature for each intake air temperature is recorded in advance.

6. A pressure outlet pipe is provided on the intake pipe to the turbocharger. A sealed case having a spring-loaded piston built therein is connected to the pressure output pipe, a check valve is provided in an air pipe that communicates between the sealed case and an air cleaner of the intake pipe, and the sealed case is connected to the dosing module via a valve; A piston in the sealed case moves due to negative pressure of the turbocharger, and air from the air cleaner is stored in the sealed case through the air piping, 6. The urea water supply system according to claim 5, wherein the valve is opened after the engine is stopped, and the air stored in the sealed case is supplied to the dosing module by the movement of the spring and the piston.

7. 7. The urea water supply system according to claim 1, wherein the deterioration prevention mechanism is a mechanism in which the urea water tank is formed by a rear fender of a vehicle having a hollow structure.

8. The DPF controller ECU and the urea SCR controller DCU are provided.

8. The urea water supply system according to claim 7, further comprising a control unit that transmits a signal from the DCU to the ECU to interrupt manual regeneration when the DPF inlet temperature is equal to or lower than a reference value and the SCR inlet temperature is higher than the DPF inlet by a specified value or more during manual regeneration of the DPF.

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