Engine exhaust purification system

Abstract

The objective is to provide an engine exhaust purification device that suppresses the deterioration of exhaust emissions. [Solution] An engine exhaust gas purification device comprising: a first catalytic converter including a first case and a first catalytic carrier held within the first case; a second catalytic converter located downstream of the first catalytic converter, including a second case and a second catalytic carrier held within the second case; and a connecting pipe connected between the first case and the second case, with a curved central axis, wherein the first catalytic carrier has a downstream end face, the first case has a downstream end protruding downstream of the downstream end face, and the second catalytic carrier has an upstream end face, with a clearance set between the downstream end and the upstream end face in a direction perpendicular to the downstream end face.

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification device for an engine.

Background Art

[0002] There is an exhaust gas purification device for an engine that includes a first catalytic converter and a second catalytic converter disposed downstream of the first catalytic converter (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] If the exhaust gas passing through the first catalytic converter flows unevenly into the second catalytic converter, the exhaust gas purification performance of the second catalytic converter may not be fully exhibited. As a result, there is a risk of deterioration of exhaust emissions.

[0005] Therefore, an object of the present invention is to provide an exhaust gas purification device for an engine in which deterioration of exhaust emissions is suppressed.

Means for Solving the Problems

[0006] The above objective can be achieved by an engine exhaust gas purification device comprising: a first catalytic converter including a first case and a first catalytic carrier held within the first case; a second catalytic converter located downstream of the first catalytic converter, including a second case and a second catalytic carrier held within the second case; and a connecting pipe connected between the first case and the second case, with a curved central axis, wherein the first catalytic carrier has a downstream end face, the first case has a downstream end protruding downstream of the downstream end face, and the second catalytic carrier has an upstream end face, with a clearance set between the downstream end and the upstream end face in a direction perpendicular to the downstream end face.

[0007] The connecting pipe is equipped with a gas sensor that detects the state of exhaust gas, the connecting pipe having an upstream section, a downstream section, and a constricted section located between the upstream section and the downstream section, wherein the cross-sectional area perpendicular to the central axis at the constricted section is smaller than the cross-sectional area perpendicular to the central axis at the upstream section and the downstream end, respectively, and the detection part of the gas sensor may be located in the constricted section.

[0008] A portion of the downstream end may be located in the throttling portion, and the detection portion of the gas sensor may face the downstream end surface in a direction perpendicular to the downstream end surface.

[0009] A portion of the first catalyst support may be located inside the connecting pipe.

[0010] The downstream end may overlap the second case in a direction parallel to the downstream end face. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an engine exhaust purification device that suppresses deterioration of exhaust emissions. [Brief explanation of the drawing]

[0012] [Figure 1] This is an external view of the exhaust gas purification system. [Figure 2] This is a cross-sectional view of an exhaust gas purification device. [Modes for carrying out the invention]

[0013] Figure 1 is an external view of the exhaust gas purification device 1. The exhaust gas purification device 1 is located on the exhaust passage connected to the engine 100 and purifies the exhaust gas from the engine 100. The exhaust gas purification device 1 and the engine 100 are located, for example, in the engine compartment of a vehicle. The engine 100 may be a gasoline engine or a diesel engine. The exhaust gas purification device 1 has a first catalytic converter 10, a second catalytic converter 30, and a connecting pipe 50.

[0014] The first catalytic converter 10 has a first case 12 and a first catalyst support 14. The first catalyst support 14 holds the first case 12. The first case 12 is cylindrical. The first catalyst support 14 is cylindrical with an outer diameter smaller than the inner diameter of the first case 12. The second catalytic converter 30 has a second case 32 and a second catalyst support 34. The second catalyst support 34 holds the second case 32. The second case 32 is cylindrical. The second catalyst support 34 is cylindrical with an outer diameter smaller than the inner diameter of the second case 32. The first catalytic converter 10 and the second catalytic converter 30 are arranged in close proximity via a connecting pipe 50.

[0015] The first catalyst carrier 14 is, for example, a three-way catalyst that has oxygen storage capacity and purifies NOx, HC, and CO. The second catalyst carrier 34 is, for example, a filter that collects particulate matter (hereinafter referred to as PM) in the exhaust, on which a catalyst that promotes the combustion of PM is supported. The upstream end 121 of the first case 12 is connected to the exhaust pipe 91. The exhaust pipe 91 is connected to the engine 100 via an exhaust manifold on the upstream side. The downstream end 322 of the second case 32 is connected to the exhaust pipe 92.

[0016] The connecting pipe 50 is connected between the first catalytic converter 10 and the second catalytic converter 30. The connecting pipe 50 is manufactured by press forming a metal sheet. An air-fuel ratio sensor 70 is provided in the connecting pipe 50. The air-fuel ratio sensor 70 is inserted into an opening provided in the connecting pipe 50. A detection unit 72 is provided at the tip of the air-fuel ratio sensor 70. The detection unit 72 is located inside the connecting pipe 50 and is exposed to the exhaust gas passing through the connecting pipe 50. The air-fuel ratio sensor 70 detects the air-fuel ratio of the exhaust gas as the state of the exhaust gas. A control device that controls the operation of the engine 100 is electrically connected to the air-fuel ratio sensor 70. The control device controls the engine 100 based on the value detected by the air-fuel ratio sensor 70.

[0017] Figure 2 is a cross-sectional view of the exhaust gas purification device 1. Figure 2 shows a cross-section parallel to the plane of paper in Figure 1. A sheet member 18 is positioned between the inner surface of the first case 12 of the first catalytic converter 10 and the outer surface of the first catalytic carrier 14. The sheet member 18 holds the first catalytic carrier 14 while ensuring exhaust gas sealing. A sheet member 38 is positioned between the inner surface of the second case 32 of the second catalytic converter 30 and the outer surface of the second catalytic carrier 34. The sheet member 38 holds the second catalytic carrier 34 while ensuring exhaust gas sealing.

[0018] The downstream end 122 of the first case 12 of the first catalytic converter 10 protrudes slightly downstream from the downstream end face 142 of the first catalyst carrier 14. In other words, the downstream end 122 protrudes into the connecting pipe 50 beyond the downstream end face 142. The upstream end 321 of the second case 32 of the second catalytic converter 30 protrudes slightly upstream from the upstream end face 341 of the second catalyst carrier 34. In other words, the upstream end 321 protrudes into the connecting pipe 50 beyond the upstream end face 341.

[0019] The downstream end face 142 of the first catalyst carrier 14 and the upstream end face 341 of the second catalyst carrier 34 are not parallel. The angle θ between the downstream end face 142 and the upstream end face 341 is set to an angle between 60 and 120 degrees. Therefore, the central axis A of the connecting pipe 50 is not straight but curved.

[0020] In the vertical direction D1, which is perpendicular to the downstream end face 142, a predetermined clearance C is set between the downstream end 122 and the upstream end face 341. In other words, the downstream end 122 does not overlap the upstream end face 341 in the direction parallel to the downstream end face 142. Thereby, the exhaust gas that passes through the first catalyst carrier 14 and is discharged from the downstream end 122 flows uniformly into the upstream end face 341. For example, if such a clearance C is not set and the downstream end 122 overlaps the upstream end face 341 in the direction parallel to the downstream end face 142, there is a possibility that the exhaust gas does not flow sufficiently in the region of the upstream end face 341 that overlaps the downstream end 122. In this embodiment, since the clearance C is set as described above, the exhaust gas flows uniformly into the upstream end face 341. Thereby, the exhaust gas purification performance of the second catalyst carrier 34 is sufficiently exerted, and the deterioration of exhaust emissions is suppressed.

[0021] The connecting pipe 50 includes an upstream portion 52, a downstream portion 54, and a throttle portion 56. The upstream portion 52 is connected to the first catalyst converter 10. The downstream portion 54 is connected to the second catalyst converter 30. The throttle portion 56 is located between the upstream portion 52 and the downstream portion 54. Specifically, the throttle portion 56 is located substantially at the center of the length of the central axis A from the upstream portion 52 to the downstream portion 54. The cross-sectional area S6 perpendicular to the central axis A at the throttle portion 56 is smaller than the cross-sectional areas S2 and S4 perpendicular to the central axis A in the upstream portion 52 and the downstream portion 54, respectively.

[0022] As shown in FIG. 2, a part of the downstream end 122 of the first case 12 of the first catalyst converter 10 is located at the throttle portion 56. Thereby, the exhaust gas that has passed through the downstream end 122 passes through a part of the throttle portion 56. Therefore, among the cross-sectional area S6 of the throttle portion 56, the passage cross-sectional area S61 through which the exhaust gas passes is smaller than the cross-sectional area S6. Therefore, the flow velocity of the exhaust gas passing through the passage cross-sectional area S61 is faster than the flow velocities of the exhaust gas passing through the upstream portion 52 and the downstream portion 54, respectively. Thus, the flow velocity of the exhaust gas passing through the throttle portion 56 is maintained at a certain value or more.

[0023] The detection unit 72 of the air-fuel ratio sensor 70 faces the downstream end face 142 in the vertical direction D1 and is located within the cross-sectional area S61 where the flow velocity is high as described above. As a result, variations in the detection value of the air-fuel ratio sensor 70 due to fluctuations in the flow velocity of the exhaust gas passing around the detection unit 72 are suppressed, and the detection accuracy of the air-fuel ratio sensor 70 is improved.

[0024] As shown in FIG. 2, a part of the downstream side of the first catalytic converter 10 is inserted into the upstream part 52. This suppresses the first catalyst carrier 14 from dropping below the activation temperature due to the outside air. As a result, the exhaust gas purification performance of the first catalyst carrier 14 is fully exhibited, and the deterioration of exhaust emissions is suppressed.

[0025] The downstream end portion 122 overlaps the upstream end portion 321 of the second case 32 in the parallel direction D2, which is a direction parallel to the downstream end face 142. In this way, the first catalytic converter 10 and the second catalytic converter 30 are arranged close to each other, and the exhaust gas purification device 1 is miniaturized. Therefore, as described above, it becomes easy to arrange the exhaust gas purification device 1 even in, for example, the engine compartment of a vehicle.

[0026] Further, the connecting pipe 50 has a rounded portion 51r inside the curved connecting pipe 50. Since the downstream side of the first catalytic converter 10 is inserted into the rounded portion 51r, it is allowed to form a large curvature for the rounded portion 51r. As a result, it becomes easy to form the connecting pipe 50 by press working.

[0027] In the above embodiment, the air-fuel ratio sensor 70 has been described as an example of the gas sensor, but the gas sensor is not limited to this. For example, the gas sensor may be a sensor that detects the concentration of oxygen, carbon dioxide, NOx, or PM in the exhaust gas. Further, the gas sensor may be a sensor that detects the temperature, flow rate, or pressure of the exhaust gas.

[0028] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of reference numerals

[0029] 1. Exhaust purifying device 10. First catalytic converter 12. Case 1 122 Downstream end 14. First catalyst support 142 Downstream end face 30. Second catalytic converter 32 Case 2 321 Upstream end 34 Second catalyst support 341 Upstream end face 50 connecting pipes 52 Upstream section 54 Downstream 56 Aperture section A Center axis S2, S4, S6 cross section S61 Passage cross section D1 vertical direction D2 parallel direction

Claims

1. A first catalytic converter comprising a first case and a first catalyst support held within the first case, A second catalytic converter comprising a second case and a second catalyst support held within the second case, located downstream of the first catalytic converter, A connecting pipe, which is connected between the first case and the second case and has a curved central axis, is provided, The first catalyst support has a downstream end face, The first case has a downstream end that protrudes downstream from the downstream end face, The second catalyst support has an upstream end face, An engine exhaust purification device wherein a clearance is set between the downstream end and the upstream end in a direction perpendicular to the downstream end.

2. The connecting pipe is equipped with a gas sensor that detects the state of exhaust gas, The connecting pipe has an upstream section, a downstream section, and a constricted section located between the upstream section and the downstream section. The cross-sectional area perpendicular to the central axis at the constricted portion is smaller than the cross-sectional area perpendicular to the central axis at the upstream and downstream ends, respectively. The detection unit of the gas sensor is located in the throttled portion, as described in claim 1 of the engine exhaust purification device.

3. A portion of the downstream end is located in the constricted section, The engine exhaust purification device according to claim 2, wherein the detection unit of the gas sensor faces the downstream end face in a direction perpendicular to the downstream end face.

4. The exhaust gas purification device for an engine according to claim 3, wherein a portion of the first catalyst carrier is located inside the connecting pipe.

5. The exhaust gas purification device for any of claims 1 to 4, wherein the downstream end overlaps the second case in a direction parallel to the downstream end face.

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