EXHAUST GAS TREATMENT DEVICE

Abstract

An exhaust gas treatment device (1) is provided with: a catalyst carrier (25) inside of which exhaust gas introduced from an end surface (26) flows; an inner case (20) that holds the side surface of the catalyst carrier (25); and an outer case (10) that is provided so as to form a first gap (41) between the outer case (10) and the side surface of the inner case (20), and to form a second gap (42) between the outer case (10) and the end surface (26) of the catalyst carrier (25), and that accommodates at least a part of the catalyst carrier (25) and the inner case (20). The outer case (10) has an exhaust gas introduction path (15) through which exhaust gas introduced from the outside passes. At least one of the outer case (10) and the inner case (20) has guide parts (18, 12a) that guide the exhaust gas introduced from the exhaust gas introduction path (15) into the first gap (41) toward the end surface (26) of the catalyst carrier (25).

Description

Exhaust gas treatment device

[0001] The present invention relates to an exhaust gas treatment device.

[0002] JP2015-180818A discloses a configuration in which exhaust gas that has passed through a first exhaust gas treatment unit (catalyst carrier) passes outside the housing of a second exhaust gas treatment unit (catalyst carrier) and then passes through the second exhaust gas treatment unit, thereby keeping the second exhaust gas treatment unit warm with the exhaust gas that has passed through the first exhaust gas treatment unit.

[0003] In order to increase the activity of the catalyst and improve purification efficiency during cold start of an internal combustion engine, it is necessary to quickly raise the temperature of the catalyst carrier. Therefore, instead of the configuration described in JP2015-180818A, the present inventors conceived of a configuration in which the temperature of the catalyst carrier is raised by circulating exhaust gas emitted from the internal combustion engine outside the catalyst carrier. However, the present inventors discovered a problem with such a configuration: it is difficult to ensure that exhaust gas flows evenly around the catalyst carrier.

[0004] An object of the present invention is to provide an exhaust gas treatment device that can improve the efficiency of purifying exhaust gas even during cold start.

[0005] According to one aspect of the present invention, an exhaust gas treatment device comprises a catalyst carrier through which exhaust gas introduced from an end face flows, an inner case that holds the side of the catalyst carrier, and an outer case that houses the catalyst carrier and at least a portion of the inner case, with a first gap between the inner case and the side of the inner case and a second gap between the outer case and the end face of the catalyst carrier, wherein the outer case has an exhaust gas inlet passage through which exhaust gas introduced from the outside passes, and at least one of the outer case and the inner case has a guide portion that guides exhaust gas introduced from the exhaust gas inlet passage into the first gap toward the end face of the catalyst carrier.

[0006] In the above embodiment, the exhaust gas introduced through the exhaust gas inlet passage is guided by the guide portion toward the end face of the catalyst carrier, so that the heat of the exhaust gas is efficiently transferred to the catalyst carrier, allowing the catalyst carrier to be heated quickly, thereby improving the efficiency of exhaust gas purification even during cold starts.

[0007] Fig. 1 is a perspective view of an exhaust gas treatment device according to an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along the radial direction of the exhaust gas treatment device, and Fig. 3 is a cross-sectional view taken along the axial direction of the exhaust gas treatment device.

[0008] Hereinafter, an exhaust gas treatment device 1 according to an embodiment of the present invention will be described with reference to the drawings.

[0009] First, the overall configuration of an exhaust gas treatment device 1 will be described with reference to Fig. 1. Fig. 1 is a perspective view of an exhaust gas treatment device 1 according to an embodiment of the present invention.

[0010] The exhaust gas treatment device 1 is provided in an exhaust system of an internal combustion engine mounted on a vehicle, for example, and purifies exhaust gas generated by the internal combustion engine by the action of a catalyst.

[0011] The exhaust gas treatment device 1 is configured to include a cylindrical outer case 10 and an inner case 20 (see FIG. 2 ) housed in the outer case 10. The inner case 20 holds a catalyst carrier 25. The outer case 10 and the inner case 20 are made of a metal such as aluminum or steel. In the following, the direction along the central axis of the cylindrical catalyst carrier 25 will be referred to as the "axial direction," and the radial direction will be referred to as the "radial direction."

[0012] The outer case 10 is composed of a cylindrical portion 11 and a bottom portion 12, and one end of the cylindrical portion 11 (the right side in FIG. 1 ) is covered by the bottom portion 12. The other end of the cylindrical portion 11 (the left side in FIG. 1 ) is connected to the exhaust gas outlet passage 30. The cylindrical portion 11 is provided with an exhaust gas inlet passage 15 that introduces exhaust gas into the interior of the outer case 10. The exhaust gas inlet passage 15 extends vertically from the side surface of the cylindrical portion 11 radially outward and is curved along the way. A flange 15 a is provided at the end of the exhaust gas inlet passage 15.

[0013] A plurality of ribs 18 are formed on the cylindrical portion 11 so as to protrude axially toward the inner peripheral surface. The ribs 18 are arranged for the purpose of guiding exhaust gas from the cylindrical portion 11 toward the bottom portion 12.

[0014] A bottom portion 12 is provided on one end side of the cylindrical portion 11. The cylindrical portion 11 has a curved portion 11a that curves in a curved shape toward the bottom portion 12 at one end side of the cylindrical portion 11 and connects the cylindrical portion 11 and the bottom portion 12. A convex portion 12a that protrudes toward the end surface 26 of the catalyst carrier 25 is formed in the center of the bottom portion 12. The bottom portion 12 is provided with an annular bulge portion 12b that is formed continuously from the curved portion 11a and bulges outward so as to connect the curved portion 11a and the convex portion 12a in a curved shape.

[0015] Next, the configuration of the exhaust gas treatment device 1 will be described in detail with reference to FIGS.

[0016] FIG. 2 is a cross-sectional view showing a cross section along the radial direction of the exhaust gas treatment device 1, and FIG. 3 is a vertical cross-sectional view showing a cross section along the axial direction of the exhaust gas treatment device 1.

[0017] 2, the inner case 20 is housed inside the outer case 10 with a first gap 41 between its side surface and the cylindrical portion 11 of the outer case 10. The inner case 20 houses the catalyst carrier 25 inside and holds the side surface of the catalyst carrier 25.

[0018] The catalyst carrier 25 has a cylindrical shape and is fitted inside the inner case 20 and held by the inner case 20. The catalyst carrier 25 is made of a ceramic or metal honeycomb with a catalyst supported on its surface. The catalyst carrier 25 purifies the exhaust gas passing through it by catalytic action. The catalyst is made of a three-way catalyst containing a precious metal. The exhaust gas that has passed through the catalyst carrier 25 is discharged to the outside of the exhaust gas treatment device 1 via the exhaust gas outlet-side passage 30 (see FIG. 1).

[0019] Ribs 18 are provided on the cylindrical portion 11 of the outer case 10. A total of six ribs 18 are formed on the cylindrical portion 11, starting from the point where the exhaust gas introduction passage 15 is connected to the outer case 10: three ribs 18 (18a, 18b, 18c) in the clockwise direction and three ribs 18 (18d, 18e, 18f) in the counterclockwise direction. The ribs 18 are recessed into the inner circumferential surface of the cylindrical portion 11. At the points where the ribs 18 are arranged, the gap between the cylindrical portion 11 and the inner case 20 is narrower than the first gap, and has a directional component along the flow direction of exhaust gas within the catalyst carrier 25. The ribs 18 are formed from the cylindrical portion 11 to the curved portion of the bottom portion 12.

[0020] The rib 18 may not be formed so as to protrude from the outer case 10 towards the inner case 20, but may be provided on the inner case 20 and formed so as to protrude from the inner case 20 towards the outer case 10.

[0021] 3, one end of the inner case 20 is configured as an exhaust gas inlet 20a that opens facing the bottom 12. An end face 26 of the catalyst carrier 25 is disposed at the exhaust gas inlet 20a, with a second gap 42 between the end face 26 of the catalyst carrier 25 and the bottom 12. Exhaust gas inside the outer case 10 flows into the catalyst carrier 25 from the exhaust gas inlet 20a. The other end of the inner case 20 is fixed to the cylindrical portion 11 by being inscribed in the cylindrical portion 11. Parts of the inner case 20 and the catalyst carrier 25 may extend outside the outer case 10 (to the exhaust gas outlet-side passage 30).

[0022] Next, the operation of the exhaust gas treatment device 1 configured as above will be described.

[0023] 2, the exhaust gas that has flowed into the exhaust gas treatment device 1 from the exhaust gas inlet passage 15 vertically collides with the outer peripheral surface of the inner case 20 at a position facing the exhaust gas inlet passage 15 of the inner case 20. As a result, the exhaust gas is divided into two parts, one in the clockwise direction in the circumferential direction and the other in the counterclockwise direction in the circumferential direction, and each part flows into a first gap 41 between the outer case 10 and the inner case 20.

[0024] The exhaust gas flowing clockwise from the exhaust gas introduction passage 15 heads in the circumferential direction of the inner case 20, and first passes near the rib 18a, whereby a portion of the exhaust gas changes direction along the rib 18a that protrudes from the inner peripheral surface of the outer case 10 and flows toward one end. The exhaust gas that passes in the circumferential direction through the gap between the rib 18a and the inner case 20 then passes near the rib 18b, whereby a portion of the exhaust gas similarly changes direction along the rib 18b and flows toward one end. Furthermore, at the rib 18c, a portion of the exhaust gas similarly changes direction along the rib 18c and flows toward one end.

[0025] In this way, most of the exhaust gas is guided to flow toward one end by these ribs 18. A portion of the exhaust gas flows in the circumferential direction up to near the bottom of the inner case 20.

[0026] Similarly, exhaust gas flowing counterclockwise from the exhaust gas inlet passage 15 passes circumferentially through ribs 18d, 18e, and 18f, and most of the gas is guided to change direction along these ribs 18 and flow toward one end.

[0027] Furthermore, the exhaust gas that has passed through rib 18c in the clockwise direction and the exhaust gas that has passed through rib 18f ​​in the counterclockwise direction reach the vicinity of the bottom of inner case 20, which is on the opposite side of exhaust gas introduction path 15. No rib 18 is provided at this location, and the exhaust gases flowing from the clockwise and counterclockwise directions collide with each other, causing the flows to head towards one end.

[0028] In this way, the exhaust gas that flows from the exhaust gas inlet passage 15 between the outer case 10 and the inner case 20 flows circumferentially around the inner case 20, and also flows axially due to the presence of the ribs 18.

[0029] As a result, the exhaust gas introduced into the exhaust gas treatment device 1 is encouraged to flow evenly around the inner case 20, so that the heat of the exhaust gas can raise the temperature of the catalyst carrier 25 housed in the inner case 20 evenly from the circumferential direction.

[0030] Next, the exhaust gas that flows from the inner case 20 toward one end passes between the inner case 20 and the outer case 10 and heads toward the bottom 12, as shown in FIG. 3 . At the bottom 12, the exhaust gas is guided to flow from the radially outer side to the radially inner side along its curved shape. The exhaust gas that has headed toward the radially inner side of the bottom 12 is further guided to flow axially toward the exhaust gas inlet 20a of the inner case 20 along the shape of the protrusion 12a. As a result, the exhaust gas flows from the exhaust gas inlet 20a to the end face 26 of the catalyst carrier 25.

[0031] The catalyst carried on the surface of the catalyst carrier 25 purifies the passing exhaust gas into carbon dioxide and water, carbon monoxide into carbon dioxide, and nitrogen oxides into nitrogen. The purified exhaust gas passes through the exhaust gas outlet passage 30 and is discharged to the outside of the exhaust gas treatment device 1.

[0032] In this way, the rib 18 is configured as a guide portion that guides the exhaust gas that has flowed radially from the exhaust gas introduction passage 15 into the outer case 10 so that it flows in the axial direction. Furthermore, the bottom portion 12 and the protrusion 12a are configured as guide portions that guide the exhaust gas so that it flows toward the exhaust gas inlet 20a of the catalyst carrier 25.

[0033] As described above, the exhaust gas treatment device 1 of this embodiment includes the catalyst carrier 25 through which exhaust gas introduced from the end face 26 flows, the inner case 20 that holds the side surface of the catalyst carrier 25, and the outer case 10 that is provided with a first gap 41 between it and the side surface of the inner case 20 and a second gap 42 between it and the end face 26 of the catalyst carrier 25 and that houses at least a portion of the catalyst carrier 25 and the inner case 20. The outer case 10 has an exhaust gas inlet passage 15 through which exhaust gas introduced from the outside passes, and at least one of the outer case 10 and the inner case 20 includes a guide portion (rib 18, protrusion 12a) that guides the exhaust gas introduced from the exhaust gas inlet passage 15 to the first gap 41 toward the end face 26 of the catalyst carrier 25.

[0034] With this configuration, exhaust gases that flow into outer case 10 can be directed along the outer peripheral surface of inner case 20 toward end face 26 of catalyst carrier 25. As a result, even when the temperature of catalyst carrier 25 is low, such as during a cold start, heat from the exhaust gases is efficiently transferred from the surface of inner case 20 to catalyst carrier 25, allowing catalyst carrier 25 to be heated quickly, thereby improving catalyst efficiency.

[0035] In addition, in this embodiment, the outer case 10 has a bottom 12 that faces the end face 26 of the catalyst carrier 25 at a predetermined distance, and the guide portion (18) guides the exhaust gas introduced from the exhaust gas inlet passage 15 into the first gap 41 so that it flows toward the bottom 12.

[0036] In this configuration, the exhaust gas that flows into the outer case 10 can be directed from the first gap 41 to the bottom 12 by the guide portion formed by the rib 18, so that the heat of the exhaust gas can be efficiently transferred from the surface of the inner case 20 to the catalyst carrier 25.

[0037] In this embodiment, the guide portion (protrusion 12 a ) guides the exhaust gas, which has been guided to flow toward the bottom portion 12 , toward the end surface 26 .

[0038] In this configuration, the exhaust gas flowing toward the bottom portion 12 is guided to the end surface 26 of the catalyst carrier 25 , so that the exhaust gas can be appropriately introduced into the catalyst carrier 25 .

[0039] In addition, in this embodiment, the guide portion is a rib 18 that protrudes from at least one of the outer case 10 and the inner case 20 into the first gap 41 and has a directional component along the flow direction of the exhaust gas within the catalyst carrier 25.

[0040] In this configuration, the rib 18 as a guide portion has a directional component along the flow direction of the catalyst carrier 25, so that the exhaust gas is caused to flow along the catalyst carrier 25 outside the catalyst carrier 25, thereby efficiently transferring the heat of the exhaust gas to the catalyst carrier 25.

[0041] In this embodiment, the rib 18 is provided on one of the outer case 10 and the inner case 20 and is spaced apart from the other of the outer case 10 and the inner case 20 .

[0042] In this configuration, the outer case 10 and the inner case 20 are spaced apart and a rib 18 is provided between them, so that exhaust gas can be introduced around the inner case 20 and the heat of the exhaust gas can be efficiently transferred to the catalyst carrier 25.

[0043] In addition, in this embodiment, the exhaust gas introduced from the exhaust gas inlet passage 15 into the first gap 41 branches into two circumferential directions through the first gap 41, and the ribs 18 are provided on both the circumferential directions, but not on the circumferential opposite side of the exhaust gas inlet passage 15.

[0044] In this configuration, the exhaust gas introduced into the first gap 41 from the exhaust gas inlet passage 15 flows evenly around the inner case 20 and then directed toward the bottom 12, so that the heat of the exhaust gas can be transferred more efficiently to the catalyst carrier 25.

[0045] In this embodiment, the bottom portion 12 has a protrusion 12 a that protrudes toward the center of the end surface 26 of the catalyst carrier 25 .

[0046] In this configuration, the exhaust gas flowing toward the bottom portion 12 is guided to the end surface 26 of the catalyst carrier 25 by the protrusions 12 a, so that the exhaust gas can be introduced into the catalyst carrier 25 appropriately.

[0047] In addition, in this embodiment, the outer case 10 further has a cylindrical portion 11 that covers the outer periphery of the inner case 20 to form the first gap 41 and is connected to the bottom portion 12, and the guide portion has a curved portion 11a that connects the cylindrical portion 11 and the bottom portion 12 in a curved shape, and an annular bulge portion 12b that is formed on the bottom portion 12 continuously from the curved portion 11a and bulges outward to connect the curved portion to the convex portion 12a.

[0048] In this configuration, the exhaust gas flowing from the inner case 20 to one end is guided along the curved shape from the curved portion 11a to the bulging portion 12b of the bottom 12, and is further guided toward the convex portion 12a, allowing the exhaust gas to flow smoothly from the first gap 41 to the end face 26 of the catalyst carrier 25.

[0049] In this embodiment, the rib 18 is formed from the cylindrical portion 11 to the curved portion of the bottom portion 12 .

[0050] In this configuration, exhaust gas flowing from the inner case 20 toward one end is guided smoothly along the shape of the inner peripheral surface of the bottom portion 12 toward the exhaust gas inlet 20 a of the inner case 20 .

[0051] In this embodiment, the exhaust gas introduction passage 15 extends radially outward from the outer case 10 .

[0052] In this configuration, the exhaust gas collides vertically from the exhaust gas inlet passage 15 with the outer peripheral surface of the inner case 20, causing the exhaust gas to flow around the inner case 20 splitting into two directions, clockwise and counterclockwise, so that the heat of the exhaust gas can be efficiently transferred from the surface of the inner case 20 to the catalyst carrier 25.

[0053] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0054] This application claims priority from Japanese Patent Application No. 2024-028201, filed with the Japan Patent Office on February 28, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. An exhaust gas treatment device comprising: a catalyst carrier through which exhaust gas introduced from an end face flows; an inner case that holds the side of the catalyst carrier; and an outer case that houses the catalyst carrier and at least a part of the inner case, with a first gap between it and the side of the inner case and a second gap between it and the end face of the catalyst carrier, wherein the outer case has an exhaust gas inlet passage through which exhaust gas introduced from outside passes, and at least one of the outer case and the inner case has a guide portion that guides exhaust gas introduced from the exhaust gas inlet passage into the first gap toward the end face of the catalyst carrier.

2. An exhaust gas treatment device according to claim 1, wherein the outer case has a bottom that faces the end face of the catalyst carrier at a predetermined distance, and the guide portion guides the exhaust gas introduced from the exhaust gas introduction path into the first gap so that it flows toward the bottom.

3. An exhaust gas treatment device according to claim 2, wherein the guide portion guides the exhaust gas, which has been guided to flow toward the bottom portion, toward the end surface.

4. An exhaust gas treatment device according to claim 3, wherein the guide portion is a rib that protrudes from at least one of the outer case and the inner case into the first gap and has a directional component that is aligned with the flow direction of the exhaust gas within the catalyst carrier.

5. An exhaust gas treatment device according to claim 4, wherein the rib is provided on one of the outer case and the inner case, and the other of the outer case and the inner case is spaced apart.

6. An exhaust gas treatment device according to claim 4, wherein the exhaust gas introduced from the exhaust gas introduction passage into the first gap branches off into one side and the other side in the circumferential direction and flows through the first gap, and the rib is provided on each side in the circumferential direction, but is not provided on a position opposite the exhaust gas introduction passage in the circumferential direction.

7. An exhaust gas treatment device according to any one of claims 4 to 6, wherein the bottom portion has a protrusion that protrudes toward the center of the end face of the catalyst carrier.

8. An exhaust gas treatment device as set forth in claim 7, wherein the outer case further has a cylindrical portion that covers the outer periphery of the inner case so as to form the first gap and is connected to the bottom, and the guide portion has: a curved portion that connects the cylindrical portion and the bottom in a curved surface; and an annular bulging portion that is formed on the bottom continuing from the curved portion and bulges outward so as to connect to the convex portion in a curved surface.

9. An exhaust gas treatment device according to claim 8, wherein the rib is formed from the cylindrical portion to the curved portion.

10. An exhaust gas treatment device according to claim 1, wherein the exhaust gas introduction passage extends radially outward from the outer case.