exhaust purification device

Abstract

Proposed is an exhaust purification device that increases a swirling flow in a mixing pipe and makes it easier to mix exhaust gas and urea water. Specifically, a reducing agent supply section (10) for supplying a reducing agent is provided in the upstream end portion of a mixing pipe (11), a notch (12) is formed in the upstream end of the mixing pipe (11), the upstream end of the mixing pipe where the notch (12) is not provided is fixedly abutted against the inner surface of a casing (14) that forms a communication path (7), a first opening part (15) is formed by the casing (14) and the notch (12), a second opening part (18) and a guide fin (19) are provided to the side surface of the mixing pipe (11), and the second opening part (18) and the guide fin (19) cause exhaust gas to swirl within the mixing pipe (11).

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification device. [Background technology]

[0002] In a conventional exhaust gas purification system for an internal combustion engine, a urea water addition device is provided in a flow path between a particulate filter and a selective catalytic reduction catalyst provided downstream thereof, and the urea water addition device sprays urea water into the flow path. A mixing pipe is provided downstream of the urea water addition device so as to cover the spray from the urea water addition device, and a swirling flow generated in the mixing pipe agitates and mixes the spray from the addition device.

[0003] The mixing pipe is formed with fins on the side wall and a side wall opening, and these fins and side wall opening are arranged and formed so that the exhaust gas discharged from the particulate filter is guided into the mixing pipe and a swirling flow is generated with the injection part of the urea water addition device as the swirl center (see, for example, Patent Documents 1, 2 and 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4928409 [Patent Document 2] Patent No. 5619430 [Patent Document 3] Patent No. 5985822 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above patent document, the mixing pipe is attached to the casing by welding the upstream end of the mixing pipe to the casing, so the upstream end of the mixing pipe in the axial direction is blocked by the casing.

[0006] Because the upstream side of the mixing pipe is blocked in this way, exhaust gas remains between the spray section of the urea water addition device and the side wall opening without actively flowing in. In addition, the exhaust gas flowing in from the side wall opening pushes back the sprayed urea water, which may cause uneven distribution of the urea water in the mixing pipe and result in insufficient mixing of the exhaust gas and the urea water.

[0007] Therefore, an object of the present invention is to provide an exhaust gas purification device that increases the swirling flow in the mixing pipe and makes it easier to mix exhaust gas and urea water than the structure of the above patent document. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides an exhaust gas control system including a particulate filter, a selective reduction catalyst provided downstream of the particulate filter, and a communication passage for guiding exhaust gas discharged from the particulate filter to the selective reduction catalyst, a changeover section for changing the flow of exhaust gas discharged from the particulate filter to a direction substantially perpendicular to the flow of exhaust gas from the particulate filter is formed on the upstream side of the communication passage; Applicable Conversion section A mixing pipe is provided inside the particulate filter, and the exhaust gas discharged from the particulate filter is passed through the mixing pipe from the side of the mixing pipe. Conversion section so that it flows into a reducing agent supply section for supplying a reducing agent is provided within an upstream end of the mixing pipe; a notch is formed in the upstream end of the mixing pipe, and the upstream end of the mixing pipe where the notch is not formed is fixedly abutted against the inner surface of a casing that forms the communication passage, and a first opening is formed by the casing and the notch; A side surface of the mixing pipe is cut or folded in a plurality of times to provide second openings and guide fins, and the second openings and guide fins cause the exhaust gas to swirl inside the mixing pipe, a bypass passage through which exhaust gas flows is formed between the mixing pipe and the communication passage; At the upstream end of the mixing pipe, a side wall that is not provided with a notch is arranged facing the upstream side, thereby suppressing the exhaust gas discharged from the particulate filter from directly impinging on a spray portion of the reducing agent supply unit, The total opening area of ​​the first openings is 1% to 10% of the total opening area of ​​the second openings.

[0013] A suppression member for suppressing the inflow of the exhaust gas into the bypass flow passage may be provided downstream of the guide fin of the mixing pipe.

[0014] In this specification, "upstream (upstream side)" refers to the inlet side of the exhaust gas emitted from an internal combustion engine, etc., in the exhaust flow path in which the exhaust purification device is installed, and "downstream (downstream side)" refers to the outlet side of the exhaust gas. [Effects of the Invention]

[0015] In the present invention, a notch is formed in the upstream end of the mixing pipe, and the upstream end of the mixing pipe without the notch is fixedly abutted against the inner surface of a casing that forms a communicating passage, thereby forming a first opening together with the casing and the notch. In the present invention, a second opening and a guide fin are provided on the side surface of the mixing pipe, and these second opening and guide fin cause the exhaust gas to swirl inside the mixing pipe. This makes it possible to prevent the accumulation of reducing agent near the spray portion of the reducing agent supply unit by the exhaust gas flowing into the mixing pipe from the first opening.

[0016] Furthermore, the flow of exhaust gas flowing in from the first opening can prevent the reducing agent from being pushed back by the exhaust gas flowing in from the second opening, preventing uneven dispersion of the reducing agent within the mixing pipe and strengthening the swirling flow generated within the mixing pipe, thereby enabling stronger stirring and mixing of the reducing agent and exhaust gas than in the above-mentioned prior art. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of an exhaust gas purification device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a longitudinal cross-sectional view of the main part of FIG. 1. [Figure 3] FIG. 2 is a perspective view of a mixing pipe used in the first embodiment of the present invention. [Figure 4] Side view of Figure 3. [Figure 5] Cross-sectional view of line AA in Figure 3. [Figure 6] FIG. 5 is a vertical cross-sectional view of a main part of an exhaust gas purification device according to a second embodiment of the present invention. [Figure 7] Cross-sectional view of line BB in Figure 6. [Figure 8] FIG. 10 is a perspective view of a mixing pipe used in a second embodiment of the present invention. [Figure 9] Side view of Figure 8. [Figure 10] FIG. 10 is a perspective view of a suppression member used in a second embodiment of the present invention. [Figure 11] Bottom view of Figure 10. [Figure 12] Cross-sectional view of line CC in Figure 11. [Figure 13] FIG. 5 is a schematic diagram of an exhaust gas purification device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings.

[0019] [Example 1] 1 is a schematic diagram showing an exhaust gas purification device 1 according to a first embodiment of the present invention. The exhaust gas purification device 1 is mounted on a vehicle such as a diesel engine, and purifies exhaust gas emitted from the internal combustion engine.

[0020] The exhaust purification device 1 is provided in an exhaust flow path 2 through which exhaust gas flows. As shown in Fig. 1, an oxidation catalyst (DOC) 3 that oxidizes and purifies HC and CO contained in the exhaust gas is arranged upstream of the exhaust purification device 1, and a particulate filter (DPF) 4 that collects particulates (fine particles) in the exhaust gas is arranged downstream of the oxidation catalyst (DOC) 3.

[0021] A selective reduction catalyst (SCR) 5 that selectively reduces NOx in the exhaust gas is disposed downstream of the particulate filter (DPF) 4. In this embodiment, a selective reduction catalyst that causes a reaction between NOx in the exhaust gas and ammonia is used as the selective reduction catalyst. An ammonia slip catalyst (ASC) 6 is disposed downstream of the selective reduction catalyst. The ammonia slip catalyst oxidizes and decomposes ammonia remaining in the exhaust gas, thereby preventing ammonia from being emitted into the atmosphere.

[0022] As shown in Fig. 1, a communication passage 7 is provided that guides the exhaust gas discharged from the particulate filter 4 to the selective reduction catalyst 5. A turning section 8 that turns the flow of the exhaust gas discharged from the particulate filter 4 at a substantially right angle is formed on the upstream side of this communication passage 7, and a reducing agent supply section 10 that supplies a liquid reducing agent such as a urea aqueous solution is provided within this turning section 8.

[0023] 2, a cylindrical mixing pipe 11 is provided in the conversion section 8 so that its axis XX is approximately perpendicular to the axis YY of the particulate filter 4. In this embodiment, a urea aqueous solution is used as the reducing agent, a urea aqueous solution injector is used as the reducing agent supply section 10, and the injection angle of the reducing agent from the urea aqueous solution injector is set to fall within the mixing pipe 11.

[0024] As shown in Figures 2 to 4, two notches 12 are formed in the circumferential direction at the upstream end 11a in the axial direction of the peripheral wall 13 of the mixing pipe 11. The notches 12 are formed so as to be open on both the front and back sides of the peripheral wall 13 of the mixing pipe 11 and on the upstream side. The number of notches 12 and the distance between the notches 12 can be set as desired.

[0025] 2, the upstream end 11a of the mixing pipe 11 in the axial direction has a peripheral wall 13a without a notch 12, which is fixed by welding or the like to the inner surface of a casing 14 that constitutes a conversion section 8 that is part of the communicating passage 7. As a result, a first opening 15 is formed by the inner surface of the casing 14 and the notch 12.

[0026] 2, it is preferable to arrange the notches 12 at the upstream end 11a in the axial direction of the mixing pipe 11 and in the peripheral wall 13a where no notches 12 are provided, so that the exhaust gas discharged from the particulate filter 4 does not directly impinge on the spray section of the reducing agent supply section 10. This reduces the effect of the exhaust gas on the state of spray of the reducing agent from the reducing agent supply section 10 into the mixing pipe 11, prevents uneven dispersion of the reducing agent inside the mixing pipe 11, and enables stronger stirring and mixing of the reducing agent and exhaust gas.

[0027] 3 to 5, the peripheral wall 13 of the mixing pipe 11 is cut and raised in multiple positions in the circumferential direction to form second openings 18 and guide fins 19. In this embodiment, the number of second openings 18 and the number of guide fins 19 are three, but the number can be set to any number.

[0028] The total opening area of ​​first openings 15 is preferably 1% to 10% of the total opening area of ​​second openings 18. Furthermore, first openings 15 and second openings 18 are formed so as not to be continuous with each other.

[0029] The exhaust gas discharged from the particulate filter 4 flows from the side of the mixing pipe 11 into the conversion section 8 provided on the upstream side of the communication passage 7, and then flows into the mixing pipe 11 through the first opening 15 and the second opening 18. The exhaust gas that has flowed into the mixing pipe 11 generates a swirling flow within the mixing pipe 11 due to the respective openings 15, 18 and the guide fins 19, and travels in the axial direction of the mixing pipe 11, and the flow direction of the exhaust gas discharged from the particulate filter 4 is changed at approximately a right angle.

[0030] Furthermore, in the conversion section 8, a swirling space 8a is formed on the upstream side of the mixing pipe 11, in which the exhaust gas can swirl outside the mixing pipe.

[0031] Further, the reducing agent supply unit 10 is provided in the mixing pipe 11 so that the spray portion of the reducing agent supply unit 10 is located near the center of the swirling flow.

[0032] The second openings 18 and the guide fins 19 can be formed in any shape as long as they are capable of generating a swirling flow within the mixing pipe 11. In this embodiment, the guide fins 19 are formed by cutting and raising the peripheral wall 13 so as to protrude radially outward from the peripheral wall 13, but the guide fins 19 may also be formed by folding the peripheral wall 13 inward.

[0033] The downstream end of the mixing pipe 11 is fitted and connected to the inner surface of the communication passage 7, and the exhaust gas is configured so that only the exhaust gas that has passed through the mixing pipe 11 is supplied to the selective reduction catalyst 5.

[0034] At the downstream end 11b in the axial direction of the peripheral wall 13 of the mixing pipe 11, a large number of arc-shaped downstream notches 20 that open to the downstream side are formed in the circumferential direction of the downstream end 11b, thereby forming a wavy shape at the downstream end 11b of the peripheral wall 13. By forming the downstream end 11b of the mixing pipe 11 in a wavy shape, the reducing agent adhering to the inner surface of the peripheral wall 13 is more likely to be released from the downstream end into the exhaust gas by atomization, vaporization, or the like.

[0035] By forming the first opening 15 at the upstream end 11a in the axial direction of the mixing pipe 11, the exhaust gas flowing into the mixing pipe 11 from the first opening 15 can prevent the reducing agent from accumulating near the spray section of the reducing agent supply section 10. Furthermore, the flow of exhaust gas flowing in from the first opening 15 can prevent the reducing agent from being pushed back by the exhaust gas flowing in from the second opening 18, thereby preventing uneven dispersion of the reducing agent in the mixing pipe 11. At the same time, the swirling flow generated in the mixing pipe 11 can be strengthened, allowing the stirring and mixing of the reducing agent and exhaust gas to be stronger than in the prior art.

[0036] Furthermore, by setting the total opening area of ​​the first openings 15 to be 1% or more and 10% or less of the total opening area of ​​the second openings 18, it is possible to prevent the reducing agent from accumulating near the spray section of the reducing agent supply section 10. At the same time, the exhaust gas flowing in from the first openings 15 can be efficiently guided downstream of the mainstream of the exhaust gas flowing in from the second openings, and the state of stirring and mixing of the reducing agent and exhaust gas can be more balanced than in the prior art.

[0037] [Example 2] In the above-described first embodiment, the downstream end of the mixing pipe 11 is fitted and connected to the inner surface of the communicating passage 7, so that only the exhaust gas that has passed through the mixing pipe 11 flows through. However, as in the second embodiment, a bypass flow path 22 may be formed between the downstream portion 11c of the mixing pipe 21 and the communicating passage 7.

[0038] 7 to 9, the downstream portion 11c of the mixing pipe 21 downstream of the guide fin 19 is formed to have a smaller diameter than the upstream portion thereof. In addition, the downstream portion of the mixing pipe 21 and the communication passage 7 are configured as a double pipe, as shown in FIG. 6, and a bypass flow path 22 is formed between the downstream portion of the mixing pipe 21 and the communication passage 7.

[0039] At the upstream end in the axial direction of the mixing pipe 11, the peripheral wall 13a without the notch 12 is fixedly attached to the inner surface of the casing 14 of the conversion section 8 by welding or the like, and the downstream side of the mixing pipe 11 is attached and fixed to the communicating passage 7 by a retaining metal fitting 23. Note that the retaining metal fitting 23 does not have to be provided, and the downstream side of the mixing pipe 11 may be fixed to the communicating passage 7 by another method.

[0040] As shown in FIG. 6, downstream of the guide fin 19 of the mixing pipe 21, a suppression member 25 having a flange 27 for suppressing the inflow of exhaust gas into the bypass flow passage 22 is provided.

[0041] 6 and 10 to 12, the suppression member 25 has a cylindrical mounting portion 26 that fits into the inner circumferential surface of the communicating passage 7, and a flange portion 27 that increases in diameter from the downstream side to the upstream side is formed on a part of the downstream side in the circumferential direction of the mounting portion 26. In this Example 2, as shown in FIGS. 10 and 11, the flange portion 27 is provided on approximately half of the circumferential direction of the mounting portion 26.

[0042] As shown in FIG. 6, the flange portion 27 is provided on the particulate filter 4 side of the suppression member 25, but is not provided on the opposite side.

[0043] The flange portion 27 can prevent the reducing agent supplied from the reducing agent supply portion 10 from adhering to the downstream wall surface of the communication passage 7 and then returning to the particulate filter 4 side. In addition, the flange portion 27 can prevent the reducing agent that has leaked out of the mixing pipe 11 from the second opening 18 from returning to the particulate filter 4 side, and can also guide the reducing agent to flow into the bypass flow passage 22.

[0044] In addition, the flange portion 27 prevents the exhaust gas flowing in from the particulate filter 4 from directly entering the bypass flow path 22, and promotes the exhaust gas to flow into the mixing pipe 21 through each of the openings 15, 18, while also acting as a straightening plate.

[0045] By forming the bypass flow path 22 between the downstream side of the mixing pipe 21 and the communication path 7, the back pressure can be reduced more than in the first embodiment.

[0046] The rest of the structure is the same as in the first embodiment, so a description thereof will be omitted.

[0047] The second embodiment also provides the same effects as the first embodiment.

[0048] [Example 3] In the above-mentioned first and second embodiments, the mixing pipes 11, 21 are arranged upstream of the communication passage 7 and inside the turning section 8 that turns the flow of exhaust gas discharged from the particulate filter 4 into a direction at a substantially right angle, but the exhaust purification device 31 of this third embodiment employs a configuration as shown in Fig. 13. That is, in the present invention, a first turning section 33 that turns the flow of exhaust gas discharged from the particulate filter 4 at a substantially right angle is provided in the communication passage 32, and a second turning section 34 that turns the flow of the exhaust gas at a substantially right angle is formed downstream of the first turning section 33, and the mixing pipes 11, 21 may be arranged inside this second turning section 34.

[0049] Also in this embodiment 3, the exhaust gas discharged from the particulate filter 4 flows into the second conversion section 34 from the side of the mixing pipes 11, 21, and then flows into the mixing pipes 11, 21 through the first opening 15 and the second opening 18. The inflowing exhaust gas generates a swirling flow in the mixing pipes 11, 21 due to the respective openings 15, 18 and the guide fins 19, and travels in the axial direction of the mixing pipes 11, 21, and the flow direction of the exhaust gas discharged from the particulate filter 4 is changed at a substantially right angle.

[0050] The rest of the structure is the same as in the first and second embodiments, so a description thereof will be omitted.

[0051] The third embodiment also provides the same effects as the first and second embodiments. [Explanation of symbols]

[0052] 1,31 Exhaust gas purification device 4 Particulate filter 5. Selective reduction catalyst 7,32 Communication path 10 Reducing agent supply unit 11 Mixing Pipe 12 Cutout 15 First opening 18 Second Opening 19 Guide fin 22 Bypass flow path 25 Restraining member

Claims

1. a particulate filter; a selective reduction catalyst provided downstream of the particulate filter; and a communication passage for guiding exhaust gas discharged from the particulate filter to the selective reduction catalyst, a changeover section for changing the flow of exhaust gas discharged from the particulate filter to a direction substantially perpendicular to the flow of exhaust gas from the particulate filter is formed on the upstream side of the communication passage; A mixing pipe is provided in the conversion section, and the exhaust gas discharged from the particulate filter flows into the conversion section provided with the mixing pipe from a side of the mixing pipe, a reducing agent supply section for supplying a reducing agent is provided within an upstream end of the mixing pipe; a notch is formed in the upstream end of the mixing pipe, and the upstream end of the mixing pipe where the notch is not formed is fixedly abutted against the inner surface of a casing that forms the communication passage, and a first opening is formed by the casing and the notch; a plurality of cuts or bends are made on the side surface of the mixing pipe to provide second openings and guide fins, and the second openings and guide fins cause the exhaust gas to swirl inside the mixing pipe; a bypass passage through which exhaust gas flows is formed between the mixing pipe and the communication passage; At the upstream end of the mixing pipe, a side wall that is not provided with a notch is arranged facing the upstream side, thereby suppressing the exhaust gas discharged from the particulate filter from directly impinging on a spray portion of the reducing agent supply unit, An exhaust gas purification device, wherein a total opening area of ​​the first openings is 1% to 10% of a total opening area of ​​the second openings.

2. 2. The exhaust gas purification device according to claim 1, further comprising a suppression member for suppressing the inflow of exhaust gas into the bypass passage, the suppression member being provided downstream of the guide fin of the mixing pipe.

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