Exhaust structure for internal combustion engine

Abstract

An exhaust structure for an internal combustion engine is provided with: a turbine and a catalyst converter provided in an exhaust passage; a bypass passage that merges with the exhaust passage via a substantially circular port; the air-fuel ratio sensor is provided with an elliptical portion and a narrowed portion in an exhaust passage between the catalyst converter and the port. The elliptical portion is similar to an imaginary elliptical shape including the port and a substantially circular first cross-section of the exhaust passage between the turbine and the port, and has an elliptical second cross-section in which the long axis and short axis directions substantially coincide with the imaginary elliptical shape. The reduced portion reduces the passage area of the exhaust toward the elliptical portion, and the imaginary elliptical shape has a center located on a straight line connecting the center of the port and the center of the first cross-section and a long axis extending in the direction of the straight line. The air-fuel ratio sensor is provided in the elliptical portion at a position closer to one end of the short axis of the second cross-section than one end of the long axis of the second cross-section.

Description

Technical Field

[0001] This invention relates to the exhaust structure of an internal combustion engine. Background Technology

[0002] Regarding the exhaust structure of internal combustion engines, for example, Patent Document 1 describes an exhaust system for an engine equipped with a turbocharger, an air-fuel ratio sensor, and a catalyst.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-227930 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the exhaust passage of an internal combustion engine, the detection accuracy of the air-fuel ratio sensor decreases when a sufficient amount of exhaust gas does not reach the top of the sensor. Therefore, a recessed portion forming a smaller cross-sectional area in the exhaust passage is considered, and the air-fuel ratio sensor is installed in this recessed portion. However, in this case, exhaust gas is more likely to hit the inner wall of the exhaust passage, thus increasing pressure loss and potentially worsening fuel economy. Furthermore, in this situation, exhaust heat diffuses from the inner wall of the exhaust passage, preventing sufficient preheating and activation of the downstream catalyst, potentially reducing the catalyst's exhaust purification performance.

[0008] Therefore, the present invention was made in view of the above-mentioned problems, and its object is to provide an exhaust structure for an internal combustion engine that can fully ensure the detection accuracy of the air-fuel ratio sensor and improve the exhaust purification performance and pressure loss.

[0009] Methods for solving problems

[0010] The exhaust structure of the internal combustion engine of the present invention comprises: a turbocharger having a turbine disposed in the exhaust passage of the internal combustion engine; a catalytic converter disposed in the exhaust passage downstream of the turbine; a bypass passage branching from the exhaust passage upstream of the turbine, bypassing the turbine, and merging with the exhaust passage upstream of the catalytic converter via a generally circular port; and an air-fuel ratio sensor for detecting the air-fuel ratio from exhaust gas in the exhaust passage. The exhaust passage between the catalytic converter and the port has an elliptical portion and a narrowed portion, the elliptical portion being connected to the exhaust passage including the port and the turbine. The exhaust passage between the wheel and the port has a first cross-section that is approximately circular in shape, similar to an imaginary ellipse, and a second cross-section that is elliptical in shape with the major and minor axes substantially aligned with the imaginary elliptical shape. The narrowed portion reduces the exhaust passage area towards the elliptical portion. The imaginary elliptical shape has a center located on a straight line connecting the center of the port and the center of the first cross-section, and a major axis extending in the direction of the straight line. The air-fuel ratio sensor is positioned on the elliptical portion closer to the end of the minor axis of the second cross-section than to the end of the major axis of the second cross-section.

[0011] In the exhaust structure described above, the air-fuel ratio sensor may also be located at one end of the short axis of the second cross section in the elliptical portion.

[0012] In the exhaust configuration described above, the air-fuel ratio sensor may also be positioned with its top facing the inlet of the catalyst converter.

[0013] Invention Effects

[0014] According to the present invention, exhaust purification performance and pressure loss can be improved while ensuring the detection accuracy of the air-fuel ratio sensor. Attached Figure Description

[0015] Figure 1 This is a structural diagram representing an example of a vehicle system.

[0016] Figure 2 This is a cross-sectional view that roughly represents an example of the exhaust structure of an engine.

[0017] Figure 3 It is along Figure 2 A cross-sectional view of the exhaust structure of the AA line.

[0018] Figure 4 This is a schematic diagram illustrating an example of an imaginary elliptical shape representing the cross-section of the outlet port and the second passage, and an elliptical shape representing the cross-section of the fifth passage. Detailed Implementation

[0019] (Structure of the vehicle system)

[0020] Figure 1 This is a structural diagram illustrating an example of a vehicle system S. The vehicle system S includes a supercharger 1 comprising a compressor 31 and a turbine 41, an engine 2 (an example of an internal combustion engine), an intake passage 3, an exhaust passage 4, a bypass passage 5, an air filter 30, and a catalytic converter 40. In the intake passage 3, air flows toward the cylinders (combustion chamber) of the engine 2. Exhaust gas, generated by the combustion of a fuel-air mixture in the combustion chamber, flows in the exhaust passage 4.

[0021] An air filter 30 is installed at the uppermost position of the air intake passage 3. The air filter 30 removes dust and other contaminants from the air by filtering it.

[0022] In the air intake passage 3, a compressor 31 is provided downstream of the air filter 30. The compressor 31 has an impeller 14 and a housing 15. The impeller 14 is housed in the housing 15. By rotating the impeller 14, the compressor 31 compresses air.

[0023] In the intake passage 3, a throttle valve 6 is provided downstream of the compressor 31. The opening degree of this throttle valve 6 is controlled, for example, by the ECU (Electronic Control Unit) based on the load required by the engine 2 based on factors such as the driver's accelerator input. As a result, the amount of air supplied to the cylinder (intake volume) is appropriately adjusted.

[0024] A turbine 41 is located at the upstream end of the exhaust passage 4. The turbine 41 has a housing 11 and an impeller 12. The impeller 12 is housed in the housing 11. The impeller 12 rotates due to the flow of exhaust gas. The rotating shafts of the impeller 12 of the turbine 41 and the impeller 14 of the compressor 31 are connected to each other by a connecting shaft 13. Thus, the impeller 12 of the turbine 41 and the impeller 14 of the compressor 31 rotate together.

[0025] In the exhaust passage 4, a catalyst converter 40 is installed downstream of the turbine 41. The catalyst converter 40 holds a catalyst carrier (such as palladium) that carries the catalyst for purifying the exhaust gas inside a housing not shown. As an example, the catalyst carrier of the catalyst converter 40 is formed of porous ceramic or the like, creating multiple lattice-like passages. The exhaust gas purified by the catalyst converter 40 is discharged outside the vehicle. It should be noted that other catalyst converters (not shown) may also be installed downstream of the catalyst converter 40.

[0026] An air-fuel ratio sensor 42 is provided in the exhaust passage 4, downstream of the turbine 41 and upstream of the catalytic converter 40. The air-fuel ratio sensor 42 detects the air-fuel ratio from the exhaust gas in the exhaust passage 4. The air-fuel ratio sensor 42 is provided for each cylinder (not shown) of the engine 2 and is used to determine the imbalance of the air-fuel ratio between cylinders.

[0027] Additionally, a bypass passage 5, bypassing the turbine 41, is connected to the exhaust passage 4. An exhaust gas bypass valve 43 is located downstream of the bypass passage 5. The bypass passage 5 branches off from the exhaust passage 4 upstream of the turbine 41, bypasses the turbine 41, and merges with the exhaust passage 4 upstream of the catalytic converter 40 via the outlet port 51 of the exhaust gas bypass valve 43. The cross-sectional area of ​​the flow path in the bypass passage 5 varies depending on the opening degree of the outlet port 51 of the exhaust gas bypass valve 43. It should be noted that the outlet port 51 is normally kept fully open. The exhaust flow Db flowing through the bypass passage 5 merges with the exhaust flow Da from the turbine 41 and flows into the catalytic converter 40.

[0028] Figure 2 This is a cross-sectional view that roughly represents an example of the exhaust structure E of engine 2. Figure 2 A cross-section of the exhaust passage 4 along the flow of exhaust gas is shown. This cross-section also extends inward into the exhaust passage 4 along the top 42a of the air-fuel ratio sensor 42.

[0029] in addition, Figure 3 It is along Figure 2 A cross-sectional view of the exhaust structure E along line AA. Figure 3 It shows the relationship with Figure 2 The cross-section of the exhaust passage 4 shown is a cross-section in the orthogonal direction.

[0030] The exhaust passage 4 includes a first passage 4a, a second passage 4b, a third passage 4c, a fourth passage 4d, and a fifth passage 4e, each with a generally circular cross-section. The generally circular shape includes, for example, a perfect circle, an ellipse, and a polygon approximating a perfect circle or an ellipse. The first passage 4a, the second passage 4b, the third passage 4c, the fourth passage 4d, and the fifth passage 4e are arranged sequentially from upstream to downstream.

[0031] A first passage 4a is provided between the engine 2 and the turbine 41. Exhaust gas flows from the engine 2 through the first passage 4a and enters the turbine 41. An inlet 50 leading to a bypass passage 5 is provided midway through the first passage 4a. A portion of the exhaust gas flows from the first passage 4a through the inlet 50 to the bypass passage 5, and the remaining portion of the exhaust gas flows to the turbine 41.

[0032] The second passage 4b ​​and the third passage 4c are integrally formed and disposed downstream of the turbine 41. The outlet port 51 of the exhaust bypass valve 43 is disposed in the second passage 4b. The outlet port 51 is inclined at a predetermined angle relative to the direction of extension of the second passage 4b ​​and is connected to the bypass passage 5. The outlet port 51 has a generally circular shape in frontal view. Here, the generally circular shape includes, for example, a perfect circle, an ellipse, and a polygon approximating a perfect circle or an ellipse. The bypass passage 5 near the outlet port 51 is disposed generally parallel to the second passage 4b.

[0033] The exhaust gas flowing through bypass passage 5 flows into third passage 4c via outlet port 51. Therefore, the exhaust gas flowing from turbine 41 through second passage 4b ​​flows into third passage 4c, merging with the exhaust gas from outlet port 51. It should be noted that outlet port 51 is an example of a port.

[0034] The third passage 4c is connected to the fourth passage 4d, for example, via a clamp 7. The clamp 7 connects the third passage 4c and the fourth passage 4d by clamping in the outer edges 4c1 protruding outward from the end of the third passage 4c and 4d1 protruding outward from the end of the fourth passage 4d. The cross-sectional shape of the passage between the third passage 4c and the fourth passage 4d is, for example, circular. The fourth passage 4d is formed such that the passage area expands from the outlet of the third passage 4c toward the connection with the fourth passage 4d.

[0035] The fourth passage 4d and the fifth passage 4e are integrally formed and disposed downstream of the third passage 4c. Exhaust gas enters the catalytic converter 40 through the fourth passage 4d and the fifth passage 4e. The fourth passage 4d is configured such that the exhaust gas passage area decreases from the connection portion with the third passage 4c toward the fifth passage 4e. An inner wall 4d2 is formed in the fourth passage 4d in a manner opposite to the direction of exhaust gas flow from the third passage 4c.

[0036] The fifth passage 4e is disposed adjacent to the inlet (input surface) 40a of the catalytic converter 40. An air-fuel ratio sensor 42 is disposed in the fifth passage 4e. The air-fuel ratio sensor 42 is mounted on a mounting base 4e1 disposed on the inner wall of the fifth passage 4e. The air-fuel ratio sensor 42 is positioned with its tip 42a facing the inlet 40a of the catalytic converter 40. The air-fuel ratio sensor 42 detects the air-fuel ratio by the exhaust gas hitting the tip 42a. Therefore, the more exhaust gas hits the tip 42a, the higher the accuracy of the air-fuel ratio detection.

[0037] The fifth passage 4e has an elliptical cross-section Wb that is similar in shape to the imaginary elliptical cross-section Wa, which includes the outlet port 51 and the second passage 4b. The directions of the major and minor axes of the imaginary elliptical shape are substantially the same as the directions of the major and minor axes of the elliptical cross-section Wb. Therefore, as indicated by reference numeral F in the attached drawing, the exhaust gas flowing from the outlet port 51 and the second passage 4b ​​is hardly obstructed by the inner wall 4d1 of the fourth passage 4d and flows smoothly from cross-section Wa to cross-section Wb. Since the fifth passage 4e is elliptical, the resistance to the flow of exhaust gas is reduced, for example, compared to a rectangular passage.

[0038] It should be noted that the fifth passage 4e is an example of an elliptical section, and the cross-section Wa of the second passage 4b ​​is an example of a first cross-section. Here, the cross-section Wa of the second passage 4b ​​is defined as a surface parallel to the exhaust outlet surface of the turbine 41 and passing through the center 51c of the outlet port 51. Furthermore, the fourth passage 4d is an example of a reduced section, and the cross-section Wb of the fifth passage 4e is an example of a second cross-section. The cross-section Wb of the fifth passage 4e is defined as a surface passing through the mounting base 4e of the air-fuel ratio sensor 42 and parallel to the inlet 40a of the catalytic converter 40.

[0039] Figure 4 This is a schematic diagram illustrating an example of the imaginary elliptical shape Wc of the cross-section Wa of the outlet port 51 and the second passage 4b, and the elliptical shape of the cross-section Wb of the fifth passage 4e. The cross-sections Wa of the outlet port 51 and the second passage 4b, and the cross-section Wb of the fifth passage 4e, are shown in the main view in the direction opposite to the exhaust flow. For example, the imaginary elliptical shape Wc is connected to two points Pa and Pb on the outer edge of the cross-section Wb of the fifth passage 4e, and two points Pc and Pd on the outer edge of the outlet port 51.

[0040] The center Ca of the imaginary elliptical shape Wc lies on the straight line Lc connecting the center 51c of the outlet port 51 and the center 4bc of the cross section Wa of the second passage 4b. Furthermore, the major axis Mc of the imaginary elliptical shape Wc extends along the direction of the straight line Lc between the centers 51c and 4bc. Additionally, the minor axis Sc of the imaginary elliptical shape Wc extends from the center Ca in a direction orthogonal to the major axis Mc.

[0041] The major axis Mc of the imaginary elliptical shape Wc is longer than the sum of the diameter R1 of the outlet port 51 and the diameter R2 of the cross section Wb of the fifth passage 4e. Furthermore, the minor axis Sc of the imaginary elliptical shape Wc is longer than the diameter R1 of the outlet port 51 and longer than the diameter R2 of the cross section Wb of the fifth passage 4e.

[0042] The cross-section Wb of the fifth path 4e is similar to the imaginary elliptical shape Wc. That is, if the lengths of the major axis Mb and minor axis Sb of the elliptical shape of the cross-section Wb of the fifth path 4e are set as L1x and L1y respectively, and the lengths of the major axis Mc and minor axis Sc of the imaginary elliptical shape Wc are set as L2x and L2y respectively, then the relationship L1x / L1y = L2x / L2y or L1x / L1y ≈ L2x / L2y holds. The relationship between the areas of the cross-section Wb of the fifth path 4e and the imaginary elliptical shape Wc is not limited.

[0043] Furthermore, the directions of the major axis Mb and minor axis Sb of the cross section Wb of the fifth passage 4e are substantially consistent with the directions of the major axis Mc and minor axis Sc of the imaginary elliptical shape Wc. That is, the major axes Mb and Mc are substantially parallel to each other, and the minor axes Sb and Sc are substantially parallel to each other. Therefore, the shapes of the exhaust inlet and outlet of the section from the second passage 4b ​​to the fifth passage 4e are similar and have the same direction. It should be noted that the major axes Mb and Mc are substantially parallel to each other. Figure 2 The paper is perpendicular to the surface, and Figure 3 The plane of the paper is parallel. Additionally, the minor axes Sb and Sc are parallel to the plane of the paper. Figure 2 Parallel to the paper surface, and Figure 3 The paper is perpendicular.

[0044] Thus, the cross-section Wb of the fifth passage 4e and the imaginary elliptical shape Wc are similarly oriented in the same direction. Therefore, the exhaust flow F1 from the outlet port 51 and the exhaust flow F2 from the second passage 4b ​​merge and flow smoothly into the fifth passage 4e, which has a curved inner wall. As such, as described above, the pressure drop and heat loss of the exhaust gas caused by the inner wall 4d2 of the fourth passage 4d can be reduced. Since the heat loss of the exhaust gas is reduced, the exhaust heat can be used to fully preheat and activate the catalyst converter 40, thereby improving the purification performance.

[0045] Furthermore, the air-fuel ratio sensor 42 is disposed at one end E1s of the short axis of the cross section Wb of the fifth passage 4e. Therefore, the top end 42a of the air-fuel ratio sensor 42 is positioned closer to the center Cb of the cross section Wb than when it is disposed at one end E1m or E2m of the long axis Mb of the cross section Wb. Since the exhaust flows F1 and F2 are narrowed by the fourth passage 4d, the closer the sensor is to the center Cb of the cross section Wb, the greater the exhaust flow. Therefore, the top end 42a of the air-fuel ratio sensor 42 contacts the amount of exhaust sufficient to detect the air-fuel ratio, thus ensuring sufficient detection accuracy of the air-fuel ratio sensor 42. It should be noted that the air-fuel ratio sensor 42 can also be disposed at the other end E2s of the short axis Sb.

[0046] Furthermore, the air-fuel ratio sensor 42 is not limited to one end E1s of the minor axis of the cross section Wb of the fifth passage 4e. It can also be positioned at a position Px on the outer edge of the cross section Wb, between one end E2m of the major axis Mb and one end E1s of the minor axis Sb, as shown by the dashed line. Position Px is an example where, within the elliptical shape of the cross section Wb, it is closer to the end E1s of the minor axis Sb than the ends E1m and E2m of the major axis Mb. In this case, the top end 42a of the air-fuel ratio sensor 42 is positioned closer to the center Cb of the cross section Wb than when it is positioned closer to the ends E1m and E2m of the major axis Mb, thus ensuring sufficient detection accuracy of the air-fuel ratio sensor 42. However, it is preferable that the air-fuel ratio sensor 42 is positioned at one end E1s of the minor axis of the cross section Wb of the fifth passage 4e, which is closer to the center Cb of the cross section Wb.

[0047] Furthermore, the air-fuel ratio sensor 42 is positioned with its tip 42a facing the inlet 40a of the catalytic converter. Therefore, the air-fuel ratio sensor 42 can improve its contact with the exhaust gas flowing into the catalytic converter 40. It should be noted that the air-fuel ratio sensor 42 can also be positioned differently, parallel to the inlet 40a of the catalytic converter 40.

[0048] The above-described embodiments are preferred embodiments of the present invention. However, they are not limited thereto, and various modifications can be made without departing from the spirit of the present invention.

Claims

1. An exhaust structure for an internal combustion engine, comprising: A turbocharger is a turbine located in the exhaust passage of an internal combustion engine. A catalyst converter is located in the exhaust passage downstream of the turbine; A bypass passage branches off from the exhaust passage upstream of the turbine, bypasses the turbine, and merges with the exhaust passage upstream of the catalytic converter via a generally circular port. and The air-fuel ratio sensor detects the air-fuel ratio from the exhaust gas in the exhaust passage. In the exhaust passage between the catalyst converter and the port, an elliptical portion and a narrowing portion are provided. The elliptical portion is similar to an imaginary elliptical shape of a first cross-section comprising the port and the exhaust passage between the turbine and the port, which is approximately circular. It also has a second cross-section of an elliptical shape whose major and minor axes are substantially aligned with the imaginary elliptical shape. The narrowing portion faces the elliptical portion, thus reducing the exhaust passage area. The hypothetical elliptical shape has a center located on a straight line connecting the center of the port and the center of the first cross-section to each other, and a major axis extending in the direction of the straight line. The air-fuel ratio sensor is positioned on the elliptical portion closer to the short axis of the second cross section than to one end of the major axis of the second cross section.

2. The exhaust structure of the internal combustion engine according to claim 1, wherein, The air-fuel ratio sensor is located at one end of the short axis of the second cross section in the elliptical portion.

3. The exhaust structure of the internal combustion engine according to claim 1 or 2, wherein, The air-fuel ratio sensor is positioned with its top facing the inlet of the catalyst converter.

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