JP2010037979A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device reducing consumption of electric power and reducing freezing of urea water at a urea water passage part without causing generation of noise. <P>SOLUTION: The exhaust emission control device 10 is provided with a sub tank 15 at a lower part of the urea water passage part 13 in a vertical direction. A solenoid controlled valve 16 provided in a branch passage part 31 branching downward off of the urea water passage part 13 opens the branch passage part 31 when operation of an internal combustion engine 21 stops. Consequently, urea water residing in the urea water passage part 13 is collected to the sub tank 15 by self weight without requiring power after stop of operation of the internal combustion engine 21. As a result, electric power consumption is reduced, and freezing of urea water in the urea water passage part 13 is prevented with less noise generation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust purification device, and more particularly to an exhaust purification device that reduces nitrogen oxide (NOx) contained in exhaust gas.

  An SCR (Selective Catalytic Reduction) system is known as an exhaust purification device that reduces NOx discharged from an internal combustion engine, particularly a diesel engine. An exhaust gas purification apparatus using an SCR system selectively reduces NOx contained in exhaust gas to nitrogen or water by, for example, injecting urea water as a reducing agent. The urea water is stored in a urea water tank and is supplied to the injection unit provided in the exhaust passage by the urea water pump. By the way, urea water as a reducing agent is an aqueous solution of urea. For this reason, when the outside air temperature decreases, the urea water remaining in the urea water passage section connecting the urea water tank and the injection section may be frozen. Therefore, conventionally, when the internal combustion engine stops operating, the urea water remaining in the urea water passage is returned to the urea water tank by reversing the urea water pump (see Patent Document 1).

However, in the case of Patent Document 1, the urea water pump is driven after the internal combustion engine stops operating. Therefore, there is a problem that power stored in the battery is consumed. Further, when the urea water pump is driven while the operation of the internal combustion engine is stopped, there is a problem in that sound is generated.
JP 2008-101564 A

  Therefore, the present invention has been made in view of the above problems, and its purpose is to reduce power consumption and to reduce freezing of urea water in the urea water passage without causing sound generation. An object is to provide an exhaust emission control device.

  In the first aspect of the present invention, the sub tank is connected to the urea water passage. The urea water passage part and the sub tank are opened and closed by a valve part. Therefore, the urea water remaining in the urea water passage portion is collected into the sub tank when the valve portion is opened. As a result, the urea water remaining in the urea water passage portion can be recovered only by opening the valve portion. Therefore, power consumption is reduced, and freezing of urea water in the urea water passage can be reduced without causing sound.

In the invention according to claim 2 or 3, the first sub pump returns the urea water collected from the urea water passage portion and stored in the sub tank to the urea water tank or the urea water passage portion. Thereby, the urea water collected in the sub tank is supplied again from the urea water tank to the injection unit. Therefore, waste of urea water can be reduced.
In the invention according to claim 4, the sub tank is provided below the urea water passage portion in the vertical direction. Therefore, when the valve portion provided between the urea water passage portion and the sub tank is opened, the urea water remaining in the urea water passage portion flows out to the sub tank by its own weight. Thereby, the power for recovering the urea water remaining in the urea water passage portion is unnecessary. Therefore, power consumption is reduced, and freezing of urea water in the urea water passage can be reduced without causing sound.

  In the invention according to claim 5, the valve portion opens between the urea water passage portion and the sub tank when the operation of the internal combustion engine is stopped. Therefore, the urea water remaining in the urea water passage portion after the operation of the internal combustion engine stops is recovered to the sub tank by opening the valve portion. Therefore, power consumption is reduced, and freezing of urea water in the urea water passage can be reduced without causing sound.

  In the invention described in claim 6, a purge valve is provided in the urea water passage. The purge valve opens the urea water passage to atmospheric pressure. Therefore, when the valve portion is opened and urea water flows out from the urea water passage portion to the sub tank, the atmosphere is introduced into the urea water passage portion via the purge valve. Thereby, the urea water remaining in the urea water passage portion quickly flows out to the sub tank. Therefore, the remaining urea water in the urea water passage can be reduced, and freezing of the urea water can be reduced.

  In the invention according to claim 7, the sub tank is connected to the lowermost point of the urea water passage portion below the urea water pump and the injection portion in the vertical direction. For example, the urea water passage portion connecting the urea water tank and the injection portion may have a complicated shape due to a spatial restriction of a portion where the exhaust purification device is mounted. In such a case, the urea water remaining in the urea water passage portion may not sufficiently flow out to the sub tank simply by providing the sub tank below the urea water passage portion. Therefore, by connecting the sub tank below the urea water pump and the injection unit to the lowest point of the urea water passage portion, the urea water remaining in the urea water passage portion is reliably recovered to the sub tank by gravity. . Therefore, freezing of urea water in the urea water passage portion can be reduced.

Hereinafter, a plurality of embodiments of an exhaust emission control device according to the present invention will be described with reference to the drawings. Note that, in a plurality of embodiments, substantially the same components are denoted by the same reference numerals, and description thereof is omitted.
(First embodiment)
An exhaust emission control device according to a first embodiment of the present invention is shown in FIGS. The exhaust purification device 10 includes a urea water tank 11, an injector 12 as an injection unit, a urea water passage unit 13, a urea water pump 14, a sub tank 15, an electromagnetic valve 16 as a valve unit, and a sub pump 17. The exhaust gas purification apparatus 10 uses the urea water injected from the injector 12 to reduce NOx contained in the exhaust gas flowing through the exhaust passage 22 of the internal combustion engine 21 as shown in FIG. As the internal combustion engine 21, for example, a diesel engine, a gasoline engine, a gas turbine engine, or the like is applied. The exhaust pipe portion 23 is formed in a cylindrical shape and forms an exhaust passage 22. One end of the exhaust passage 22 is connected to the internal combustion engine 21. Further, the end of the exhaust passage 22 opposite to the internal combustion engine 21 is open to the atmosphere. The exhaust purification device 10 has an SCR catalyst 24 on the side closer to the atmosphere than the injector 12. As a result, the urea water injected from the injector 12 is mixed with the exhaust gas flowing through the exhaust passage 22 and flows into the SCR catalyst 24. In the SCR catalyst 24, NOx contained in the exhaust is reduced using urea water injected from the injector 12. The exhaust purification apparatus 10 includes a DPF (Diesel Particulate Filter) 25 and an oxidation catalyst 26 in order from the internal combustion engine 21 side in addition to the SCR catalyst 24. The SCR catalyst 24, the DPF 25, and the oxidation catalyst 26 are all provided in the exhaust passage 22. The exhaust purification device 10 is not limited to the above-described filter and catalyst, and various filters and catalysts such as a three-way catalyst and an ammonia oxidation catalyst may be provided. Exhaust gas discharged from the internal combustion engine 21 sequentially passes through the DPF 25, the oxidation catalyst 26, and the SCR catalyst 24, and then is discharged to the atmosphere.

  As shown in FIGS. 1 and 2, the urea water tank 11 stores urea water, that is, an aqueous solution of urea. The injector 12 is attached to the exhaust pipe portion 23, and an unillustrated nozzle hole provided at the tip is exposed to the exhaust passage 22. The urea water passage portion 13 connects the urea water tank 11 and the injector 12. The urea water pump 14 supplies urea water stored in the urea water tank 11 to the injector 12. The injector 12 injects urea water supplied from the urea water tank 11 into the exhaust gas flowing through the exhaust passage 22.

  As shown in FIG. 1, in the urea water passage portion 13, a branch passage portion 31 branches downward from the urea water tank 11 to the injector 12 in the gravity direction. The branch passage portion 31 connects the urea water passage portion 13 and the sub tank 15. The sub tank 15 is connected to the lower end of the branch passage portion 31 that branches downward from the urea water passage portion 13. The branch passage 31 is preferably branched from the lowermost part in the gravity direction in the urea water passage 13 connecting the urea water tank 11 and the injector 12. That is, it is desirable that the sub tank 15 be positioned below the urea water pump 14 and the injector 12. The branch passage 31 is provided with an electromagnetic valve 16. The electromagnetic valve 16 opens and closes the branch passage portion 31 and intermittently connects between the urea water passage portion 13 and the sub tank 15. By providing the sub tank 15 below the urea water passage portion 13, when the electromagnetic valve 16 opens the branch passage portion 31, the urea water in the urea water passage portion 13 is collected in the sub tank 15.

  As shown in FIG. 2, the exhaust purification device 10 includes a control unit 32 such as an ECU (Electronic Control Unit). The control unit 32 has a microcomputer including a CPU, a ROM, and a RAM (not shown). The control unit 32 is connected to, for example, an accelerator opening sensor that detects the opening of an accelerator pedal (not shown) and a rotation speed sensor that detects the rotation speed of the internal combustion engine 21. The control unit 32 detects the operating state of the internal combustion engine 21 based on signals output from the accelerator opening sensor and the rotation speed sensor. The control unit 32 controls the urea water pump 14 and the injector 12 based on the detected operating state of the internal combustion engine 21. Thus, the control unit 32 controls the pressure of the urea water supplied from the urea water tank 11 to the injector 12 based on the operating state of the internal combustion engine 21. Further, the control unit 32 intermittently connects the urea water passage unit 13 and the sub tank 15 by outputting a control signal to the electromagnetic valve 16.

  The sub tank 15 has a temperature sensor 33 and a liquid amount sensor 34. The temperature sensor 33 detects the temperature of the urea water collected from the urea water passage portion 13 and stored in the sub tank 15. The temperature sensor 33 outputs the detected temperature of the urea water to the control unit 32 as an electrical signal. The liquid amount sensor 34 detects the amount of urea water stored in the sub tank 15. In the case of the first embodiment, the liquid quantity sensor 34 is a liquid level sensor that detects the liquid level position of the urea water stored in the sub tank 15. The liquid amount sensor 34 outputs the detected amount of urea water to the control unit 32 as an electrical signal. The liquid amount sensor 34 is not limited to the detection of the liquid surface position by the liquid surface sensor, and may detect the liquid amount by other means such as detecting the liquid amount from the weight of urea water.

  As shown in FIGS. 1 and 2, the sub tank 15 and the urea water pump 14 are connected by a return passage portion 35. A sub pump 17 is provided in the return passage portion 35. The sub pump 17 discharges the urea water collected in the sub tank 15 to the urea water tank 11. The controller 32 drives the sub-pump 17 when the urea water collected in the sub-tank 15 exceeds a preset amount. As a result, the urea water collected in the sub tank 15 is returned to the urea water tank 11 by the sub pump 17 via the return passage portion 35. As described above, the sub pump 17 constitutes the first sub pump in the claims. The sub pump 17 may be provided inside the sub tank 15 or in the middle of the return passage portion 35 outside the sub tank 15.

Next, the operation of the exhaust emission control device 10 having the above configuration will be described with reference to FIG.
When the internal combustion engine 21 is started (S101), the control unit 32 closes the electromagnetic valve 16 (S102). That is, the control unit 32 closes the solenoid valve 16 to shut off the urea water passage unit 13 and the sub tank 15. Thereby, the urea water flowing through the urea water passage portion 13 is supplied to the injector 12 without flowing into the sub tank 15.

  When the controller 32 closes the electromagnetic valve 16 in step S102, the controller 32 starts the operation of the urea water pump 14 (S103). The control unit 32 operates the urea water pump 14 by supplying power to the urea water pump 14 from a battery (not shown). As a result, the urea water stored in the urea water tank 11 is discharged to the urea water passage portion 13 by the urea water pump 14.

  The controller 32 activates the urea water pump 14 in step S103 and injects urea water from the injector 12 (S104). The urea water discharged from the urea water pump 14 is supplied to the injector 12 via the urea water passage portion 13. The controller 32 intermittently injects urea water from a nozzle hole (not shown) of the injector 12 by driving a solenoid valve (not shown) of the injector 12. As a result, the urea water supplied via the urea water passage portion 13 is injected from the injection hole of the injector 12 into the exhaust gas flowing through the exhaust passage 22. The injector 12 is not limited to intermittently injecting urea water by driving the electromagnetic valve by the control unit 32. For example, the injector 12 may intermittently inject the urea water from the nozzle hole by the pressure of the urea water supplied by the urea water pump 14.

  When the urea water is injected into the exhaust gas in step S104, the control unit 32 determines whether the temperature of the urea water stored in the sub tank 15 and the position of the liquid level are equal to or higher than a preset threshold value. (S105). In the sub tank 15, urea water is recovered from the urea water passage portion 13. On the other hand, the capacity of the sub tank 15 is finite. Therefore, when the urea water recovered in the sub tank 15 exceeds a predetermined amount, that is, when the position of the urea water level exceeds a preset threshold value, the urea water recovered in the sub tank 15 is stored in the urea water tank 11. Returned to Further, the urea water collected in the sub tank 15 may be frozen when the elapsed time from the start of the internal combustion engine 21 is short. Therefore, the control unit 32 determines whether or not the temperature of the urea water stored in the sub tank 15 is equal to or higher than a preset threshold value.

The control unit 32 acquires the temperature of the urea water stored in the sub tank 15 from the temperature sensor 33 provided in the sub tank 15. In addition, the control unit 32 acquires the amount of urea water stored in the sub tank 15 from the liquid amount sensor 34 provided in the sub tank 15. The controller 32 compares the acquired urea water temperature and urea water amount with a preset threshold value.
In step S105, the control unit 32 operates the sub pump 17 when the amount and temperature of the urea water stored in the sub tank 15 are equal to or higher than a preset temperature (S106). When the amount of urea water stored in the sub tank 15 is equal to or greater than the threshold value, the urea water may overflow from the sub tank 15 if the recovery of the urea water from the urea water passage portion 13 is continued. On the other hand, when the temperature of the urea water stored in the sub tank 15 is lower than the threshold value, the urea water may be frozen and hinder the operation of the sub pump 17. Therefore, the control unit 32 drives the sub pump 17 when the amount of urea water stored in the sub tank 15 is equal to or higher than the threshold and the temperature is also equal to or higher than the threshold. Thereby, the urea water collected in the sub tank 15 is returned to the urea water tank 11 via the return passage portion 35. The melting point of urea water, which is an aqueous solution of urea, is about −10 ° C. Therefore, in the first embodiment, the sub pump 17 is driven when the temperature of the urea water becomes 5 ° C. or higher including safety. Further, by providing the sub tank 15 in the vicinity of the internal combustion engine 21 or the exhaust pipe portion 23, heating of the urea water stored in the sub tank 15 by heat generated from the internal combustion engine 21, that is, thawing is promoted. As a result, the urea water collected in the sub tank 15 is quickly returned to the urea water tank 11 after the internal combustion engine 21 is started.

  When the control unit 32 determines in step S105 that the amount or temperature of the urea water in the sub tank 15 is smaller than a predetermined threshold, and after driving the sub pump 17 in step S106, the operation of the internal combustion engine 21 is stopped ( S107), the electromagnetic valve 16 is opened (S108). When the internal combustion engine 21 is in operation, urea water is continuously injected into the exhaust gas flowing through the exhaust passage 22. Therefore, the branch passage portion 31 that connects the urea water passage portion 13 and the sub tank 15 is blocked by the electromagnetic valve 16. On the other hand, when the operation of the internal combustion engine 21 is stopped, the urea water injection and the urea water pump 14 are also stopped, and the urea water flow in the urea water passage portion 13 is also stopped. Furthermore, when the operation of the internal combustion engine 21 that is a heat source is stopped, the temperature of the urea water passage portion 13 decreases. Therefore, when the operation of the internal combustion engine 21 is stopped, the control unit 32 opens the electromagnetic valve 16 of the branch passage unit 31.

  When the electromagnetic valve 16 is opened, the urea water passage portion 13 and the sub tank 15 are connected via the branch passage portion 31. Therefore, the urea water remaining in the urea water passage portion 13 after the internal combustion engine 21 is stopped flows out to the sub tank 15 via the branch passage portion 31 by its own weight. The branch passage portion 31 connected to the sub tank 15 branches from the lowest point located below the urea water pump 14 and the injector 12 of the urea water passage portion 13 in the vertical direction. Thereby, the urea water remaining in the urea water passage portion 13 is quickly recovered to the sub tank 15 by its own weight. By providing the urea water pump 14 above the urea water tank 11 in the vertical direction, the urea water remaining between the urea water tank 11 and the urea water pump 14 also flows out to the urea water tank 11 by its own weight. As a result, the residual urea water is reduced between the urea water tank 11 and the injector 12.

  In the first embodiment described above, the sub tank 15 is provided below the urea water passage portion 13 in the vertical direction. And the solenoid valve 16 provided in the branch passage part 31 branched from the urea water passage part 13 downward in the vertical direction opens the branch passage part 31 when the internal combustion engine 21 stops its operation. As a result, the urea water remaining in the urea water passage portion 13 after the internal combustion engine 21 stops operating flows out to the sub tank 15 due to its own weight. Therefore, the urea water remaining in the urea water passage portion 13 after the operation of the internal combustion engine 21 is stopped is reduced. Further, when the electromagnetic valve 16 opens the branch passage portion 31, the urea water remaining in the urea water passage portion 13 flows out to the sub tank 15. Therefore, the power for discharging the urea water in the urea water passage portion 13 to the sub tank 15 is not necessary. That is, the urea water remaining in the urea water passage 13 is recovered in the sub tank 15 by opening and closing the electromagnetic valve 16 after the operation of the internal combustion engine 21 is stopped. Therefore, power consumption can be reduced and freezing of urea water in the urea water passage portion 13 can be prevented with little generation of sound.

  In the first embodiment, the urea water collected in the sub tank 15 is returned to the urea water tank 11 by the sub pump 17 when the amount stored in the sub tank 15 exceeds a predetermined amount. At this time, the sub pump 17 is operated when the operation of the internal combustion engine 21 is started and the temperature of the urea water stored in the sub tank 15 becomes equal to or higher than a predetermined temperature. Therefore, the urea water is thawed as the internal combustion engine 21 is operated, and then returned from the sub tank 15 to the urea water tank 11 during the operation of the internal combustion engine 21. Therefore, when the urea water is returned from the sub tank 15 to the urea water tank 11, the sound generated from the sub pump 17 can be made difficult to leak outside. Further, by returning the urea water collected in the sub tank 15 to the urea water tank 11, the returned urea water is supplied to the injector 12 again. Therefore, waste of urea water can be reduced.

(Second Embodiment)
An exhaust emission control device according to a second embodiment of the present invention is shown in FIG.
In the case of the second embodiment, the exhaust purification device 10 includes a sub pump 41 as shown in FIG. The sub pump 41 is provided in a return passage portion 42 that connects the sub tank 15 and the urea water passage portion 13 separately from the branch passage portion 31. The sub pump 41 discharges the urea water collected in the sub tank 15 to the urea water passage portion 13. That is, the urea water recovered in the sub tank 15 is returned to the urea water tank 11 in the first embodiment, whereas the urea water recovered in the sub tank 15 is returned to the urea water passage portion 13 in the second embodiment. The return passage portion 42 is provided with a check valve 43 that restricts the flow of urea water from the urea water passage portion 13 to the sub tank 15 side. The sub pump 41 constitutes the second sub pump in the claims. The sub pump 41 may be provided not only in the sub tank 15 but also in the return passage portion 42 outside the sub tank 15.

  In the second embodiment, similarly to the first embodiment, when the operation of the internal combustion engine 21 is stopped, the electromagnetic valve 16 of the branch passage portion 31 is opened. Therefore, the urea water remaining in the urea water passage portion 13 is collected in the sub tank 15 by its own weight. On the other hand, when the amount of the urea water collected in the sub tank 15 increases, the temperature of the urea water rises, and then the urea water in the sub tank 15 is returned to the urea water passage portion 13 by the sub pump 41. Therefore, freezing of urea water in the urea water passage portion 13 can be prevented. Further, in the second embodiment, the return passage portion 42 connects the sub tank 15 and the urea water passage portion 13. Therefore, the total length of the return passage portion 42 can be shortened.

(Third embodiment)
An exhaust emission control device according to a third embodiment of the present invention is shown in FIG.
In the case of the third embodiment, as shown in FIG. 5, the exhaust gas purification apparatus 10 includes a purge valve 51 and a purge valve 52 in the urea water passage portion 13. The purge valve 51 is provided close to the injector 12 in the urea water passage portion 13. In other words, the purge valve 51 is provided on the urea water tank 11 side of the injector 12, that is, on the urea water inlet side of the injector 12. The purge valve 52 is provided in the urea water passage portion 13 in the vicinity of the urea water pump 14. In other words, the purge valve 52 is provided on the injector 12 side of the urea water pump 14, that is, on the urea water outlet side of the urea water pump 14.

  When the internal combustion engine 21 is stopped, the electromagnetic valve 16 of the branch passage portion 31 is opened. Therefore, the urea water remaining in the urea water passage portion 13 flows out to the sub tank 15 due to its own weight. In the third embodiment, by providing the urea water passage portion 13 with the purge valve 51 and the purge valve 52, the atmosphere is introduced into the urea water passage portion 13 via the purge valve 51 and the purge valve 52. When the internal combustion engine 21 is stopped, the control unit 32 opens both the electromagnetic valve 16 of the branch passage unit 31 and the purge valve 51 and the purge valve 52 of the urea water passage unit 13. Thus, the urea water remaining in the urea water passage portion 13 flows out from the urea water passage portion 13 to the sub tank 15 more quickly by opening the purge valve 51 and the purge valve 52.

In the third embodiment, by providing the urea water passage portion 13 with the purge valve 51 and the purge valve 52, the atmosphere is introduced into the urea water passage portion 13 when the electromagnetic valve 16 is opened. Therefore, the discharge of urea water from the urea water passage portion 13 to the sub tank 15 can be further promoted.
In the third embodiment, the example in which the two purge valves 51 and 52 are provided in the urea water passage portion 13 has been described. However, one or three or more purge valves may be provided in the urea water passage portion 13. .

  The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

The schematic diagram which shows the exhaust gas purification apparatus by 1st Embodiment of this invention. 1 is a block diagram showing an exhaust emission control device according to a first embodiment of the present invention. Schematic which shows the flow of an operation | movement of the exhaust gas purification apparatus by 1st Embodiment of this invention. The schematic diagram which shows the exhaust gas purification device by 2nd Embodiment of this invention. The schematic diagram which shows the exhaust gas purification device by 3rd Embodiment of this invention.

Explanation of symbols

  In the drawings, 10 is an exhaust purification device, 11 is a urea water tank, 12 is an injector (injection part), 13 is a urea water passage part, 14 is a urea water pump, 15 is a sub tank, 16 is a solenoid valve (valve part), 17 Denotes a sub pump (first sub pump), 21 denotes an internal combustion engine, 22 denotes an exhaust passage, 41 denotes a sub pump (second sub pump), and 51 and 52 denote purge valves.

Claims (7)

A urea water tank for storing urea water;
An injection unit that is provided in an exhaust passage through which exhaust gas of the internal combustion engine flows, and injects urea water into the exhaust;
Connecting the urea water tank and the injection unit, a urea water passage part through which urea water flows,
A urea water pump that is provided in the urea water passage section and supplies urea water stored in the urea water tank to the injection section;
A sub-tank connected to the urea water passage,
A valve portion that opens and closes between the urea water passage portion and the sub tank;
An exhaust emission control device comprising:   The exhaust emission control device according to claim 1, further comprising a first sub pump for returning the urea water stored in the sub tank to the urea water tank.   The exhaust emission control device according to claim 1 or 2, further comprising a second sub pump for returning the urea water stored in the sub tank to the urea water passage portion.   The exhaust purification device according to claim 1, 2, or 3, wherein the sub tank is provided below the urea water passage portion in a vertical direction.   5. The exhaust gas purification according to claim 1, wherein the valve portion opens between the urea water passage portion and the sub tank when the operation of the internal combustion engine is stopped. 6. apparatus.   6. The exhaust emission control device according to claim 1, further comprising a purge valve that is provided in the urea water passage portion and opens the urea water passage portion to an atmospheric pressure.   The sub-tank is below the urea water pump and the injection unit in the top-and-bottom direction, and is connected to the lowest point of the urea water passage unit. The exhaust emission control device according to item.

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