Urea injection system for diesel engine aftertreatment system

Abstract

The present application discloses a kind of urea injection systems for diesel engine post-processing system, comprising: valve, it is integrated overflow valve of two one-way valves integrated into one body that is opened at low pressure but closed at high pressure and closed at low pressure but opened at high pressure or two independent valves that a normally open exhaust valve is arranged side by side with a normally closed overflow valve, the valve is all arranged on return pipe.The present application uses a valve that is opened at low pressure but closed at high pressure to realize emptying and pressurization with a valve that is closed at low pressure but opened at high pressure, so that the pump can better maintain the stability of urea supply pressure, reduce energy consumption, while also quickly emptying when pump starts.

Description

Technical Field

[0001] This invention relates to the field of diesel engine aftertreatment technology. More specifically, this invention relates to a urea injection system for a diesel engine aftertreatment system. Background Technology

[0002] Figure 1 A schematic diagram of the urea injection system commonly used in current diesel engine aftertreatment systems is shown below: The inlet end of the urea pump 100 is connected to the urea filter 300 through the inlet pipe 200 to draw urea from the urea tank (not shown in the figure), and the outlet end is connected to the urea nozzle 500 through the injection pipe 400 to inject urea into the engine exhaust pipe; a urea return channel is also arranged at the outlet end of the urea pump 100 to allow some urea to return to the urea tank (not shown in the figure) through the return pipe 600.

[0003] The aforementioned urea injection system requires urea pump 100 to deliver urea at a relatively stable pressure to nozzle 500. While some current technologies, such as using a large overflow ratio (the ratio of overflow to nozzle injection volume) and deformable bodies like airbags or plastic containers, achieve pressure stabilization, significant pressure fluctuations still occur during nozzle opening and closing. Integrating an electrically controlled valve in the return channel, synchronized with the nozzle via a controller, can not only stabilize the pressure but also minimize urea overflow, thus reducing energy consumption. However, this design requires an additional electrically controlled valve, increasing cost and the burden on the controller, thus reducing system reliability.

[0004] With proper design, a mechanical check valve (relief valve) can achieve a similar effect to the electrically controlled valve: when the nozzle opens and the urea pressure drops, the check valve immediately closes or reduces the overflow; when the nozzle closes and the urea pressure rises, the check valve is opened by the increased pressure, increasing the overflow; thus, it can play a role in stabilizing the pressure.

[0005] However, when starting a urea pump, the air in the pump and pipeline must first be purged before urea can be drawn into the pump. For most pumps, pumping air is much less efficient than pumping liquids, and the air pressure is often insufficient to open the overflow valve. In this case, the air can only be discharged by opening the nozzle, which is extremely inefficient and often fails to meet the actual usage requirements of purging and preparing urea for delivery in a short time. Summary of the Invention

[0006] One object of the present invention is to provide a urea injection system for a diesel engine aftertreatment system, which is a purely mechanical device that does not require electronic control, and can both stabilize pressure and efficiently ventilate when the urea pump starts.

[0007] To achieve these objectives and other advantages according to the invention, a urea injection system for a diesel engine aftertreatment system is provided, characterized in that it includes: a valve that simultaneously functions as an exhaust valve and a pressure regulator, said valve being disposed on a return pipe.

[0008] Preferably, the valve includes a normally open vent valve and a normally closed relief valve, which are arranged in parallel through two return pipes.

[0009] Preferably, the valve is an integrated relief valve that combines two one-way valves that open under low pressure but close under high pressure and close under low pressure but open under high pressure.

[0010] Preferably, it further includes: a urea pump connected to a urea tank via an inlet pipe, the urea pump also being connected to a nozzle via an injection pipe; a return pipe connected to both the injection pipe and the urea tank; and a filter disposed on the inlet pipe, the injection pipe, or inside the urea pump.

[0011] Preferably, the integrated overflow valve includes: a first housing, which is hollow inside and has an inlet and an outlet respectively penetrating through the interior; the interior of the first housing is divided into an external groove and an internal channel by a cylindrical partition with openings at both the top and bottom; the lower end of the cylindrical partition is integrally formed with the first housing, and the upper end is spaced from the inlet; the internal channel is connected to the outlet and forms a stepped channel that is wider at the top and narrower at the bottom; and a first exhaust valve core, which is disposed inside the first housing, fitting snugly against the inner wall of the first housing; the first exhaust valve core has a vertical first through hole, and the first exhaust valve core passes through a... A spring supports the first valve core. The lower end of the first spring is fixed to the bottom of the external groove, and the upper end of the first spring is fixed to the bottom of the first exhaust valve core. The first overflow valve core is set close to the inner channel wall. The first overflow valve core has multiple vertical second through holes along its circumference. The first overflow valve core is supported by a second spring. The lower end of the second spring is fixed to the step of the stepped channel, and the upper end of the second spring is fixed to the bottom of the first overflow valve core. The first through hole and the second through hole are not vertically connected, the second through hole and the outlet are not vertically connected, and the first through hole and the outlet are vertically connected.

[0012] Preferably, the integrated overflow valve includes: a second housing, which is hollow inside and has an inlet and an outlet penetrating through the interior, respectively. The interior of the second housing is divided into an external groove and an internal channel by a cylindrical partition with openings at both the top and bottom. The lower end of the cylindrical partition is integrally formed with the second housing, and the upper end is spaced from the inlet. The internal channel is connected to the outlet and forms a stepped channel that is wider at the top and narrower at the bottom. A second exhaust valve core is disposed inside the second housing, which is flush with the inner wall of the second housing. The second exhaust valve core has multiple vertical third through holes and multiple vertical fourth through holes arranged along different circumferential directions. The second exhaust valve core is supported by a first spring, the lower end of which is fixed to the bottom of the external groove. The upper end is fixed to the bottom end of the second exhaust valve core, and the bottom end of the second exhaust valve core is also recessed upward to form a concave hole. The fourth through hole communicates with the concave hole, and the third through hole is located outside the concave hole. The second overflow valve core is located inside the concave hole and is set just close to the wall of the concave hole. The second overflow valve core is set to be able to move freely up and down in the internal channel. The second overflow valve core is provided with a vertical fifth through hole. The second overflow valve core is also supported by a second spring. The lower end of the second spring is fixed to the step of the stepped channel, and the upper end of the second spring is fixed to the bottom end of the second overflow valve core. Among them, the third through hole does not communicate with the internal channel in the vertical direction, the fifth through hole does not communicate with the fourth through hole in the vertical direction, and the fifth through hole communicates with the outlet in the vertical direction.

[0013] Preferably, the integrated overflow valve includes: a third housing, which is hollow inside and has an inlet and an outlet respectively through the interior at the top and bottom, and an annular partition is fixed to the inner wall of the third housing; a third overflow valve core, which is disposed inside the third housing and below the annular partition, and has multiple vertical sixth through holes arranged along its circumference. The third overflow valve core also has a vertical seventh through hole inside the sixth through holes, which is a stepped shape, wider at the top and narrower at the bottom. The third overflow valve core passes through... The second spring supports the third housing, with its lower end fixed inside and its upper end fixed to the bottom of the third overflow valve core. The third exhaust valve core is supported by the first spring and is located inside the annular partition, forming an annular eighth through hole with the annular partition. The lower end of the first spring is fixed to the step of the seventh through hole, and its upper end is fixed to the bottom of the third exhaust valve core. The sixth through hole and the eighth through hole are not vertically connected, nor are the eighth through hole and the seventh through hole. The sixth through hole and the outlet are vertically connected.

[0014] Preferably, the valve is located inside the urea tank and immersed in the urea solution to prevent the valve from losing water and drying out, causing urea crystals to form inside and thus malfunctioning the valve.

[0015] The present invention has at least the following beneficial effects:

[0016] The urea injection system of the present invention can achieve both pressure stabilization and efficient venting by setting valves, with low cost and stable and reliable system operation.

[0017] The integrated overflow valve designed in this invention can minimize overflow, thereby reducing the total liquid output of the urea pump, reducing energy consumption, and extending the service life of the urea pump.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the commonly used urea injection system structure in this invention.

[0020] Figure 2 This is a schematic diagram of one type of urea injection system of the present invention: it employs an integrated overflow valve;

[0021] Figure 3 A schematic diagram of the first structure of the integrated overflow valve used in this invention: venting state;

[0022] Figure 4 A schematic diagram of the first structure of the integrated overflow valve used in this invention: no overflow state;

[0023] Figure 5 Schematic diagram of the first structure of the integrated overflow valve of the present invention: overflow state;

[0024] Figure 6 Another schematic diagram of the urea injection system of the present invention: employing two independent one-way valves;

[0025] Figure 7 Schematic diagram of the second structure of the integrated urea pump overflow valve of the present invention: venting state;

[0026] Figure 8 Schematic diagram of the second structure of the integrated urea pump overflow valve of the present invention: no overflow state;

[0027] Figure 9 Schematic diagram of the second structure of the integrated urea pump overflow valve of the present invention: overflow state;

[0028] Figure 10 Schematic diagram of the third structure of the integrated urea pump overflow valve of the present invention: venting state;

[0029] Figure 11 Schematic diagram of the third structure of the integrated urea pump overflow valve of the present invention: no overflow state;

[0030] Figure 12A schematic diagram of the third structure of the integrated urea pump overflow valve of the present invention: overflow state.

[0031] Explanation of reference numerals in the attached figures:

[0032] 100. Urea pump; 200. Inlet pipe; 300. Filter; 400. Injection pipe; 500. Nozzle; 600. Return pipe; 700. Integrated overflow valve; 800. Normally open exhaust valve; 900. Normally closed overflow valve; 10. First housing; 11. Second housing; 12. Third housing; 15. Outlet; 20. First exhaust valve core; 21. Second exhaust valve core; 22. Third exhaust valve core; 25. First through hole; 26. Third through hole; 27. Fourth through hole; 28. Eighth through hole; 30. First spring; 40. First overflow valve core; 41. Second overflow valve core; 42. Third overflow valve core; 45. Second through hole; 46. Fifth through hole; 47. Sixth through hole; 48. Seventh through hole; 50. Second spring. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0034] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] This invention provides a urea injection system for a diesel engine aftertreatment system, comprising: a valve that simultaneously functions as an exhaust valve and a pressure regulator, the valve being disposed on a return pipe. The valve on the return pipe allows for venting of air from the pipeline when necessary, and for pressure regulation when required.

[0036] The main feature of the injection system of this invention is the use of a valve that opens under low pressure but closes under high pressure. This valve can be a normally open vent valve that opens to allow air to escape smoothly when the urea injection system is purged, paired with a normally closed relief valve that closes under low pressure but opens under high pressure. This relief valve is a normally closed overflow valve that can regulate the urea liquid pressure by controlling the overflow flow, thereby achieving purging and pressurization. This allows the pump to better maintain the stability of the urea supply pressure, reduce pressure fluctuations in the injection liquid caused by the opening and closing of the urea nozzle, reduce energy consumption, and also allow for rapid purging when the pump starts. The injection system of this invention can also integrate the two valves into a single integrated relief valve, where one valve simultaneously performs purging and pressure stabilization functions.

[0037] Example 1

[0038] like Figure 2 As shown, a urea return channel is also arranged between the urea pump 100 and the nozzle 500, so that a portion of the urea pumped out by the urea pump 100 returns to the urea tank (not shown in the figure) through the return pipe 600 and the integrated overflow valve 700.

[0039] The integrated relief valve can open at lower pressures, allowing the urea pump to discharge air through the integrated relief valve 700 during the purging phase. Once the gas is discharged, the urea pump 100, inlet pipe 200, injection pipe 400, and return pipe 600 are filled with liquid, and the hydraulic pressure continues to rise. The integrated relief valve 700 closes before the pressure reaches the required working pressure. However, when the hydraulic pressure exceeds a certain set value, the integrated relief valve 700 can open again, allowing the liquid to return to the urea tank (not shown in the figure) through the integrated relief valve 700.

[0040] Thus, whenever the nozzle 500 opens and closes, causing pressure fluctuations in the injection pipe 400 and return pipe 600, the integrated relief valve 700 opens to release pressure when the pressure is higher than a certain value, and the valve's overflow (pressure release) is proportional to the pressure. When the pressure is lower than a certain value, the integrated relief valve 700 closes, so that the urea pressure delivered to the nozzle 500 tends to stabilize.

[0041] Example 2

[0042] like Figure 6As shown, the same effect can be achieved by using two different one-way valves, namely a normally open exhaust valve 800 and a normally closed relief valve 900, instead of the relief valve 700. The return pipe between the outlet of the urea pump 100 and the inlet of the nozzle 500 is divided into a return channel and an exhaust channel. For ease of writing, this invention refers to them collectively as the return pipe 600. Both are connected to valves on a single pipe. The return channel consists of the return pipe and the normally closed relief valve 900, through which some urea can return to the urea tank (not shown in the figure). The exhaust channel consists of an exhaust pipe and a normally open exhaust valve 800, through which air can be discharged when the urea pump 100 is emptied.

[0043] The normally open vent valve 800 opens at a lower pressure to allow air to escape smoothly, and closes at a higher liquid pressure after venting is complete. Conversely, the normally closed relief valve 900 remains closed at a lower pressure and opens when the hydraulic pressure is higher than a certain value (such as injection pressure) to allow some liquid to overflow back to the urea tank. Moreover, the overflow rate is proportional to the pressure value exceeded.

[0044] The normally open vent valve 800 opens when the pressure is below a certain value, allowing the pump 100 to smoothly discharge air through the valve during venting. After venting is complete, liquid enters the urea pump 100, inlet pipe 200, injection pipe 400, and return pipe 600, causing the pressure to rise and close the normally open vent valve 800.

[0045] The normally closed relief valve 900 opens when the liquid level is above a certain value and closes when the level is below a certain value, thereby reducing pressure fluctuations caused by the opening and closing of the nozzle 500.

[0046] The complete system of the urea injection system of the present invention includes: a urea pump 100, which is connected to a urea tank through an inlet pipe 200, and the urea pump is also connected to a nozzle 500 through an injection pipe 400; a return pipe 600, which is connected to the injection pipe 400 and the urea tank respectively; and a filter 300, which is disposed on the inlet pipe 200, the injection pipe 400, or inside the urea pump 100.

[0047] like Figure 1 As shown, one end of the urea pump 100 is connected to the urea filter 300 through the inlet pipe 200 to draw urea from the urea tank (not shown in the figure), and the other end is connected to the urea nozzle 500 through the urea injection pipe 400 to deliver urea at a certain pressure to the nozzle 500; there is a return channel between the outlet of the urea pump 100 and the inlet of the nozzle 500, and excess urea can be returned to the urea tank (not shown in the figure) through the return pipe 600.

[0048] If necessary, an additional filter (not shown) can be added between the urea pump 100 and the nozzle 500 to further filter the urea. In some applications, the filter 300 can also be arranged inside the urea pump 100, or the filter 300 can be used as a primary filter, and then a fine filter (not shown) can be added between the filter 300 and the urea pump 100.

[0049] This invention describes three specific forms of the integrated overflow valve 700.

[0050] Example 3

[0051] like Figures 3 to 5 As shown, the integrated overflow valve includes: a first housing 10, which is hollow inside and has an inlet and an outlet 15 that pass through the interior, respectively. The interior of the first housing 10 is divided into an external groove and an internal channel by a cylindrical partition with openings at both the top and bottom. The lower end of the cylindrical partition is integrally formed with the first housing 10, and the upper end is spaced from the inlet. The internal channel is connected to the outlet 15 and forms a stepped channel that is wider at the top and narrower at the bottom; a first exhaust valve core 20, which is disposed inside the first housing 10, exactly against the inner wall of the first housing 10. The first exhaust valve core 20 is provided with a vertical first through hole 25. The first exhaust valve core 20 is supported by a first spring 30. The first spring 30 is fixed to the bottom of the external groove, and the upper end of the first spring 30 is fixed to the bottom end of the first exhaust valve core 20. The first overflow valve core 40 is set close to the inner channel wall. The first overflow valve core 40 has a plurality of vertical second through holes 45 arranged around its circumference. The first overflow valve core 40 is supported by the second spring 50. The lower end of the second spring 50 is fixed to the step of the stepped channel, and the upper end of the second spring 50 is fixed to the bottom end of the first overflow valve core 40. The first through hole 25 and the second through hole 45 are not vertically connected, the second through hole 45 and the outlet 15 are not vertically connected, the first through hole 25 and the outlet 15 are vertically connected, and the second through hole 45 and the outlet 15 are connected.

[0052] The aforementioned integrated overflow valve 700, as shown Figures 3-5As shown, a first vent valve core 20 that can slide up and down is installed inside the first housing 10. The first vent valve core 20 has a first through hole 25 in the middle, allowing air or urea solution to pass through it. The first vent valve core 20 can move downward under the pressure of the urea liquid above, and can move upward under the drive of the first spring 30. Below the first vent valve core 20, another first overflow valve core 40 that can slide up and down is arranged at the bottom of the first housing 10. The first overflow valve core 40 has many second through holes 45 around its periphery, allowing air or urea solution to pass through it. The first overflow valve core 40 can move downward under the pressure of the urea liquid above, and can move upward under the drive of the second spring 50. When the first vent valve core 20 moves to the lower stop point and is in close contact with the first overflow valve core 40 (e.g. Figure 4 As shown), the integrated relief valve 700 is in a fully closed state, preventing any gas or liquid from passing through it. At any time, when there is a gap between the first exhaust valve core 20 and the first relief valve core 40 (e.g., ...), Figure 3 and 5 As shown, the integrated relief valve 700 is in the open state, and gas or liquid can pass through the integrated relief valve 700.

[0053] The first spring 30 that drives the first exhaust valve core 20 to move upward can be designed such that when the pressure on the first exhaust valve core 20 is less than a certain value, it keeps the first exhaust valve core 20 in its highest position (e.g., Figure 3 As shown in the figure), the valve opens, allowing air or liquid to pass through the first exhaust valve core 20 and the lower first overflow valve core 40, and finally exit from the bottom of the integrated overflow valve 700 through the outlet 15 into the urea tank (not shown in the figure). When the pressure on the first exhaust valve core 20 exceeds a certain value, it overcomes the resistance of the first spring 30 and drives the first exhaust valve core 20 downward to the lowest (lower stop) position. At this time, if the pressure on the first overflow valve core 40 is insufficient to overcome the downward movement of the second spring 50, the lower surface of the first exhaust valve core 20 is in close contact with the upper surface of the first overflow valve core 40 (e.g., ...). Figure 4 As shown in the figure, the valve is closed, meaning that neither air nor liquid can pass through the integrated relief valve 700.

[0054] The second spring 50, which drives the first overflow valve core 40 to move upward, can be designed such that when the pressure on the first overflow valve core 40 is less than a certain value, it keeps the first overflow valve core 40 in its highest position (e.g., when the pressure on the first overflow valve core 40 is less than a certain value). Figure 3 or Figure 4 (as shown); at this time, when the first exhaust valve core 20 is also in the highest position, air and urea can pass through the first exhaust valve core 20 and the first overflow valve core 40 (as shown); Figure 3As shown), however, when the first exhaust valve core 20 is in the lowest position, i.e., the valve is closed, neither air nor liquid can pass through the valve (as shown). Figure 4 (As shown); when the pressure on the first relief valve core 40 exceeds a certain value, it overcomes the resistance of the second spring 50 and drives the first relief valve core 40 to move downward, so that even if the first exhaust valve core 20 is in the lowest position, the valve will still open (as shown). Figure 5 As shown in the figure, the liquid can pass through the first exhaust valve core 20 and the first overflow valve core 40, pass through the outlet 15 from the bottom of the overflow valve, and return to the urea tank (not shown in the figure).

[0055] With the above arrangement, when the urea pump 100 starts, the pump, inlet pipe 200, injection pipe 400, and return pipe 600 are all filled with air. At this time, the urea pump needs to expel the air from the above-mentioned devices as quickly as possible to draw in the urea solution. For most liquid pumps, the efficiency and pressure of pumping out air are much lower than the efficiency and pressure of pumping out liquid. Therefore, during the entire purging process, the air pressure will remain in a very low range before the liquid is drawn in. If the force of the first spring 30 driving the first exhaust valve core 20 upward is greater than the downward driving force caused by the air pressure, the valve will remain in the open state (e.g., Figure 3 (As shown), this allows air to pass smoothly through the first exhaust valve core 20 and the first overflow valve core 40, and is eventually discharged from the urea pump.

[0056] During the above purging process, if the urea nozzle 500 is opened, some air will also be discharged from the nozzle 500, which helps to shorten the purging time.

[0057] After the air is purged, the liquid enters the urea pump, then flows through the return pipe 600 and the injection pipe 400, ultimately reaching the urea nozzle 500 and the integrated overflow valve 700. As the liquid pressure continuously increases, when the pressure exerted by the liquid on the first vent valve core 20 is sufficient to overcome the resistance generated by the first spring 30, the first vent valve core 20 will move downwards until it is completely closed (e.g., Figure 4 (As shown). At this time, the urea nozzle 500 can also be closed, and all liquid outlets are blocked. This will cause the internal pressure of the urea pump 100, inlet pipe 200, injection pipe 400, and return pipe 600 to rise rapidly. When the hydraulic pressure reaches the injection pressure required by the nozzle 500, the urea injection system is ready and enters normal operation.

[0058] At this point, if the hydraulic pressure continues to rise, when the fluid exceeds a certain value, it will be sufficient to drive the first relief valve core 40 to overcome the second spring 50 and move downwards, and the entire integrated relief valve 700 will be in the open state again (e.g., Figure 5As shown in the diagram, the liquid returns to the urea tank (not shown) through the overflow valve. The higher the liquid pressure, the further the first overflow valve core 40 moves downwards, the larger the opening, and the greater the overflow flow. As the overflow flow increases and the liquid pressure decreases, the first overflow valve core 40 moves upwards under the drive of the second spring 50, and the overflow flow decreases accordingly. Thus, the integrated overflow valve 700's ability to adjust the overflow flow according to the pressure can play a stabilizing role.

[0059] Clearly, the overflow rate is not only directly proportional to the liquid pressure, but also inversely proportional to the spring constant K of the second spring 50. The softer the spring, the larger the overflow rate, and vice versa. Therefore, we can adjust the overflow opening pressure and overflow rate by selecting the spring constant K of the second spring 50.

[0060] Especially at the moment the urea nozzle 500 opens, causing a drop in liquid pressure, the integrated relief valve 700 quickly responds by closing or reducing the overflow. Conversely, at the moment the urea nozzle 500 closes, causing a rise in hydraulic pressure, the integrated relief valve 700 quickly responds by opening or increasing the overflow. In this way, the pressure regulation function of the integrated relief valve 700 can significantly reduce the hydraulic fluctuations caused by the opening and closing of the urea nozzle 500. Ideally, when the relief valve 700 is properly designed and its overflow is adjusted to precisely compensate for (follow) the changes in liquid output caused by the opening and closing of the nozzle 500, it can achieve a very good pressure stabilization effect.

[0061] The response time of the aforementioned relief valve (following the nozzle switch) is determined by factors such as the elastic coefficient K of the second spring 50, the mass of the relief valve core, and the viscosity of the fluid medium. Therefore, the design of this valve also needs to take into account an appropriate natural frequency.

[0062] Finally, because the throttling effect of the integrated overflow valve 700 can minimize the overflow, it also reduces the total liquid output of the urea pump, reduces energy consumption, and extends the service life of the urea pump.

[0063] Example 4

[0064] like Figures 7 to 9As shown, the integrated overflow valve includes: a second housing 11, which is hollow inside and has an inlet and an outlet 15 that pass through the interior, respectively. The interior of the second housing 11 is divided into an outer groove and an inner channel by a cylindrical partition with openings at both the top and bottom. The lower end of the cylindrical partition is integrally formed with the second housing 11, and the upper end is spaced from the inlet. The inner channel is connected to the outlet 15 and forms a stepped channel that is wider at the top and narrower at the bottom. A second exhaust valve core 21 is disposed inside the second housing 11, which is exactly close to the inner wall of the second housing 11. The second exhaust valve core 21 has multiple vertical third through holes 26 and multiple vertical fourth through holes 27 arranged along different circumferential directions. The second exhaust valve core 21 is supported by a first spring 30. The lower end of the first spring 30 is fixed to the bottom of the outer groove, and the upper end of the first spring 30 is fixed to the bottom end of the second exhaust valve core 21. The bottom end of the core 21 is recessed upward to form a concave hole, and the fourth through hole 27 communicates with the concave hole. The third through hole 26 is located outside the concave hole. The second overflow valve core 41 is located inside the concave hole and is set close to the wall of the concave hole. The second overflow valve core 41 is configured to move freely up and down in the internal channel. The second overflow valve core 41 is provided with a vertical fifth through hole 46. The second overflow valve core 41 is also supported by a second spring 50. The lower end of the second spring 50 is fixed to the step of the stepped channel, and the upper end of the second spring 50 is fixed to the bottom end of the second overflow valve core 41. The third through hole 26 does not communicate with the internal channel in the vertical direction, and the fifth through hole 46 does not communicate with the fourth through hole 27 in the vertical direction. The fifth through hole 46 communicates with the outlet 15 in the vertical direction. The third through hole 26 only communicates with the outlet 15 when there is a gap between the second exhaust valve core 21 and the top of the above-mentioned cylindrical partition.

[0065] The integrated overflow valve 700 structure shown in Embodiment 4 is similar to that shown in Embodiment 3, except that the opening positions on the exhaust valve core and the overflow valve core are different, and there are also some differences in the relative installation positions and the installation positions of the springs. In fact, the overflow valve core is embedded in the exhaust valve core, and the specific positional relationship is shown in the attached drawings. The first spring 30 and the second spring 50 are designed to achieve the same function as in Embodiment 3, which is to ensure that the entire device has three different working states under different conditions, realizing the functions of venting and stabilizing pressure.

[0066] Example 5

[0067] like Figures 10 to 12As shown, the integrated overflow valve includes: a third housing 12, which is hollow inside and has an inlet and an outlet 15 extending through the interior, respectively, and an annular partition is fixed to the inner wall of the third housing 12; a third overflow valve core 42, which is disposed inside the third housing 12 and below the annular partition, and has multiple vertical sixth through holes 47 arranged around its circumference. The third overflow valve core 42 also has a vertical seventh through hole 48 inside the sixth through holes 47, which is a stepped shape, larger at the top and smaller at the bottom. The third overflow valve core 42 is supported by a second spring 50. The second spring 50 is fixed at its lower end inside the third outer shell 12, and at its upper end to the bottom end of the third overflow valve core 42. The third exhaust valve core 22 is supported by the first spring 30 and is located inside the annular partition, forming an annular eighth through hole 28 between it and the annular partition. The lower end of the first spring 30 is fixed on the step of the seventh through hole 48, and the upper end of the first spring 30 is fixed to the bottom end of the third exhaust valve core 22. The sixth through hole 47 and the eighth through hole 28 are not vertically connected, and the eighth through hole 28 and the seventh through hole 48 are also not vertically connected. The sixth through hole 47 and the outlet 15 are vertically connected.

[0068] The integrated relief valve 700 structure shown in Embodiment 5 differs from those shown in Embodiments 3 and 4. In this embodiment, the exhaust valve core is mounted on top of the relief valve core, and the first spring 30 driving it is embedded in the relief valve core, as shown in the attached drawings for the specific positional relationship. The function of the first spring 30 and the second spring 50 is exactly the same as in Embodiment 3, which is to ensure that the entire device has three different working states under different conditions, realizing the functions of venting and stabilizing pressure.

[0069] In fact, the integrated relief valve 700 is not limited to the three types listed above, and can have many different structural forms, which will not be listed one by one in this article.

[0070] As described above, since urea is prone to crystallization in a dehydrated state or in cold weather, which can cause valve failure, the normally open exhaust valve 800, normally closed relief valve 900, and the two-in-one integrated relief valve 700 are best used while immersed in the urea tank to avoid failure due to urea crystallization.

[0071] Clearly, considering both reliability and manufacturing costs and space constraints, an integrated relief valve is the preferred option.

[0072] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A urea injection system for a diesel engine aftertreatment system, characterized in that, include: The valve, which has both venting and pressure stabilizing functions, is located inside the urea tank and is immersed in the urea solution; the valve is installed on the return pipe, and the valve is an integrated relief valve that integrates two one-way valves that open under low pressure but close under high pressure and close under low pressure but open under high pressure. The integrated relief valve includes: The third outer shell is hollow inside and has an inlet and an outlet that pass through the interior, respectively, at the top and bottom. An annular partition is fixed to the inner wall of the third outer shell. The third overflow valve core is located inside the third housing and below the annular partition, with multiple vertical sixth through holes arranged along its circumference. The third overflow valve core also has a vertical seventh through hole inside the sixth through hole, which is a stepped shape with a larger top and a smaller bottom. The third overflow valve core is supported by a second spring, with the lower end of the second spring fixed inside the third housing and the upper end of the second spring fixed to the bottom end of the third overflow valve core. The third exhaust valve core is supported by the first spring and is located inside the annular partition, forming an annular eighth through hole with the annular partition. The lower end of the first spring is fixed on the step of the seventh through hole, and the upper end of the first spring is fixed on the bottom end of the third exhaust valve core. Among them, the sixth through hole and the eighth through hole are not connected vertically, the eighth through hole and the seventh through hole are not connected vertically, and the sixth through hole and the outlet are connected vertically.

2. The urea injection system for a diesel engine aftertreatment system as described in claim 1, characterized in that, Also includes: A urea pump, which is connected to a urea tank via an inlet pipe, and the urea pump is also connected to a nozzle via an injection pipe; The return pipe connects to the injection pipe and the urea tank respectively; A filter is installed on the inlet pipe, the injection pipe, or inside the urea pump.

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