Exhaust system for internal combustion engines

Abstract

To provide an exhaust device of an internal combustion engine, which is capable of warming-up of a catalyst and detection of an air-fuel ratio.SOLUTION: An exhaust device of an internal combustion engine comprises a first exhaust passage 34 on which a turbine housing 12 of a supercharger is provided, a first bypass passage and a second bypass passage 42, which bypass the turbine housing, are located upstream of the first exhaust passage in a flow direction of exhaust gas, and are connected to the first exhaust passage, and a valve 50 which is provided at a portion of the first exhaust passage where the first bypass passage and the second bypass passage are connected, opens and closes the first bypass passage and the second bypass passage. The first bypass passage is connected near the wall of the first exhaust passage as compared with the second bypass passage, and the second bypass passage is connected near the center of the first exhaust passage as compared with the first bypass passage. An inclination angle of the first bypass passage with respect to the extension direction of the first exhaust passage is smaller than an inclination angle of the second bypass passage with respect to the extension direction of the first exhaust passage.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an exhaust system for an internal combustion engine. [Background technology]

[0002] BACKGROUND ART Internal combustion engines equipped with a supercharger are known (for example, Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-156958 Summary of the Invention [Problem to be solved by the invention]

[0004] The turbocharger operates when exhaust gas is introduced into the turbine of the turbocharger. A bypass passage that bypasses the turbine is provided in the exhaust passage. The flow of exhaust gas from the bypass passage is controlled by opening and closing a valve (WGV). An air-fuel ratio sensor and a catalyst that purifies the exhaust gas are provided in the exhaust passage. Concentrating the exhaust flow in the center of the exhaust passage promotes catalyst warm-up. Meanwhile, to detect the air-fuel ratio, the air-fuel ratio sensor is exposed to the exhaust. To be able to detect the air-fuel ratio from the exhaust gas flowing in the center, the air-fuel ratio sensor is made large and protrudes to the center of the exhaust passage. The increased size of the air-fuel ratio sensor increases weight and costs. Therefore, an object of the present invention is to provide an exhaust system for an internal combustion engine that is capable of warming up the catalyst and detecting the air-fuel ratio. [Means for solving the problem]

[0005] The object of the present invention is to provide an exhaust system including a first exhaust passage provided with a turbine housing of a turbocharger, a first bypass passage and a second bypass passage that bypass the turbine housing and are located upstream of the first exhaust passage in an exhaust flow direction and are connected to the first exhaust passage, a valve that is provided in a portion of the first exhaust passage where the first bypass passage and the second bypass passage are connected and that opens and closes the first bypass passage and the second bypass passage, a catalyst that is provided in the first exhaust passage and is located downstream of the valve, and a catalyst that is provided in the first exhaust passage and is located downstream of the valve. and upstream of the catalyst an air-fuel ratio sensor located at, wherein the first bypass passage is connected closer to a wall of the first exhaust passage than the second bypass passage, the second bypass passage is connected closer to a center of the first exhaust passage than the first bypass passage, and an inclination angle of the first bypass passage with respect to an extension direction of the first exhaust passage is smaller than an inclination angle of the second bypass passage with respect to the extension direction of the first exhaust passage. The inclination angle of the second bypass passage is 10° or more, and the valve body of the valve moves to open and close the valve, and when the valve is open, exhaust gas flowing through the second bypass passage collides with the valve body. This can be achieved by the exhaust system of the internal combustion engine.

[0006] The aforementioned When the valve is open, the valve element may be positioned relative to the first bypass passage and the second bypass passage in a direction that intersects with a direction in which the first bypass passage and the second bypass passage are aligned.

[0007] The first exhaust passage may have a connecting portion that is inclined from an extension direction of the first exhaust passage, the first bypass passage and the second bypass passage may be connected to the connecting portion, and the valve body may be provided at the connecting portion.

[0008] The exhaust gas supply system may include a second exhaust passage and a third exhaust passage, the first bypass passage being connected to the second exhaust passage and the first exhaust passage, and the second bypass passage being connected to the third exhaust passage and the first exhaust passage. [Effects of the Invention]

[0009] It is possible to provide an exhaust system for an internal combustion engine that is capable of warming up a catalyst and detecting an air-fuel ratio. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating an engine system according to an embodiment. [Figure 2] FIG. 2 is an enlarged view of the exhaust passage. [Figure 3] FIG. 3 is a cross-sectional view illustrating an example of an exhaust device. [Figure 4] FIG. 4 is a cross-sectional view illustrating an example of an exhaust device. DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 1 is a schematic diagram illustrating an engine system 100 according to an embodiment. The engine system 100 includes an internal combustion engine 10, two superchargers, and two exhaust systems 20. The internal combustion engine 10 is, for example, a V8 engine having eight cylinders #1 to #8. Cylinders #1, #3, #5, and #7 are arranged on the left bank of the internal combustion engine 10. Cylinders #2, #4, #6, and #8 are arranged on the right bank. An intake passage (not shown) is connected to the eight cylinders of the internal combustion engine 10.

[0012] The illustration shows a turbine housing 12 of the turbocharger. The turbine is housed in the turbine housing 12. The compressor housing and other components are omitted.

[0013] One of the two exhaust systems 20 is designated as exhaust system 20a, and the other is designated as exhaust system 20b. The exhaust system 20a discharges exhaust gas from cylinders #1, #3, #5, and #7 of the internal combustion engine 10. The exhaust system 20b discharges exhaust gas from cylinders #2, #4, #6, and #8 of the internal combustion engine 10. The exhaust systems 20 will be described below using the exhaust system 20a as an example.

[0014] One exhaust system 20 has exhaust passages 30, 32, and 34, bypass passages 40 and 42, an air-fuel ratio sensor 36, a catalyst 38, and a wastegate valve (WGV) 50 (valve). The exhaust passages 30 and 32 are connected between the turbine housing 12 and the internal combustion engine 10. The exhaust passage 30 (second exhaust passage) is connected to cylinders #1 and #3 of the internal combustion engine 10. The exhaust passages 30 merge into one and are connected to the turbine housing 12. The exhaust passage 32 (third exhaust passage) is connected to cylinders #5 and #7. The exhaust passages 32 merge into one and are connected to the turbine housing 12.

[0015] An exhaust passage 34 (first exhaust passage) is connected to the turbine housing 12. An air-fuel ratio sensor 36 and a catalyst 38 are provided in the exhaust passage 34. The air-fuel ratio sensor 36 detects the air-fuel ratio. The catalyst 38 is located downstream of the air-fuel ratio sensor 36 and is, for example, a three-way catalyst, which purifies the exhaust gas.

[0016] The exhaust system 20 has bypass passages 40 and 42. The bypass passages 40 and 42 are located downstream of the exhaust passages 30 and 32 and upstream of the exhaust passage 34. The bypass passage 40 (first bypass passage) is connected to the exhaust passage 30 downstream of the junction position, and is connected to the exhaust passage 34 upstream of the air-fuel ratio sensor 36 and the catalyst 38. The bypass passage 42 (second bypass passage) is connected to the exhaust passage 32 downstream of the junction position, and is connected to the exhaust passage 34 upstream of the air-fuel ratio sensor 36 and the catalyst 38. In the exhaust passage 34, from upstream to downstream of the exhaust, the connection portions with the bypass passages 40 and 42, the air-fuel ratio sensor 36, and the catalyst 38 are arranged in this order.

[0017] A WGV 50 is provided in the portion of the exhaust passage 34 where the bypass passages 40 and 42 are connected. The WGV 50 opens and closes the bypass passages 40 and 42 to control the exhaust flow rate. When the WGV 50 is open, the exhaust flows through the bypass passages 40 and 42 and is introduced into the exhaust passage 34. When the WGV 50 is closed, more exhaust is introduced into the turbine housing 12 than when the WGV 50 is open. A control device such as an ECU (Electronic Control Unit) (not shown) controls the opening degree of the WGV 50.

[0018] In the exhaust system 20b, an exhaust passage 30 is connected to cylinders #2 and #6, and an exhaust passage 32 is connected to cylinders #4 and #8. The rest of the configuration is the same as that of the exhaust system 20a.

[0019] FIG. 2 is an enlarged view of the exhaust passage 34. The Z axis indicates the direction in which the exhaust passage 34 extends. The X axis indicates the direction across the exhaust passage 34 and is perpendicular to the Z axis. The Y axis indicates the direction across the exhaust passage 34 and is perpendicular to the Z axis and X axis. Line C in FIG. 2 indicates the center of the exhaust passage 34 in the X axis direction.

[0020] The exhaust passage 34 has a connection part 35. The connection part 35 is located in the exhaust passage 34 downstream of the turbine housing 12 and upstream of the air-fuel ratio sensor 36 and the catalyst 38. The connection part 35 is positioned offset to one side (the left side in FIG. 2) from the center of the exhaust passage 34 in the X-axis direction.

[0021] The bypass passages 40 and 42 are connected to the exhaust passage 34 at a connection portion 35. The portion where the bypass passage 40 and the connection portion 35 are connected is an inlet 40a from the bypass passage 40 to the exhaust passage 34. The portion where the bypass passage 42 and the connection portion 35 are connected is an inlet 42a from the bypass passage 42 to the exhaust passage 34. The bypass passages 40 and 42 are aligned in the X-axis direction. The bypass passage 40 is located outside the bypass passage 42 and is closer to the wall 34a of the exhaust passage 34. The bypass passage 42 is located inside the bypass passage 40 and is closer to the center of the exhaust passage 34.

[0022] 3 and 4 are cross-sectional views illustrating the exhaust device 20. FIG. 3 illustrates a cross section including the bypass passage 40. FIG. 4 illustrates a cross section including the bypass passage 42. As shown in FIGS. 3 and 4, the connection portion 35 is a slope inclined from the extension direction (Z-axis direction) of the exhaust passage 34, and is located between the Z-axis direction and the Y-axis direction. A valve element 52 of the WGV 50 is provided at the connection portion 35. When the valve element 52 comes into contact with the wall of the connection portion 35, the WGV 50 closes. When the valve element 52 moves away from the wall, the WGV 50 opens. FIGS. 3 and 4 illustrate the open state. The valve element 52 is located in the Y-axis direction relative to the bypass passages 40 and 42.

[0023] As shown in Figure 3, the inclination angle of the bypass passage 40 with respect to the extension direction of the exhaust passage 34 is θ1. As shown in Figure 4, the inclination angle of the bypass passage 42 with respect to the extension direction of the exhaust passage 34 is θ2. The angle θ1 is smaller than the angle θ2. The angle θ1 may be, for example, 10° or less. The angle θ2 may be, for example, 10° or more, 20° or more, or 30° or more.

[0024] As shown in Figure 3, the angle θ1 is small. Therefore, the extension direction of the bypass passage 40 is close to the extension direction of the exhaust passage 34. The direction of the exhaust gas flowing through the bypass passage 40 (arrow A1) is close to the direction of the exhaust gas flowing through the exhaust passage 34 (arrow A2). The exhaust gas is less likely to collide with the valve body 52. ​​The bypassed exhaust gas flows near the center of the exhaust passage 34. The exhaust gas hits the center of the catalyst 38, which promotes warming up of the catalyst 38. Warming up the catalyst 38 improves purification performance.

[0025] As shown in Figure 4, the angle θ2 is large. The extension direction of the bypass passage 42 becomes farther away from the extension direction of the exhaust passage 34. The end of the bypass passage 42 faces the valve body 52 of the WGV 50. The exhaust gas flowing through the bypass passage 42 (arrow A3) collides with the valve body 52 and diffuses (arrow A4). The exhaust gas diffuses and flows up to the vicinity of the wall 34a of the exhaust passage 34.

[0026] The air-fuel ratio sensor 36 is attached to the wall 34a of the exhaust passage 34. The air-fuel ratio sensor 36 is inserted into the wall 34a from the outside and protrudes into the inside of the exhaust passage 34. The exhaust gas that flows through the bypass passage 42 diffuses and flows near the wall 34a. Therefore, the air-fuel ratio sensor 36 is exposed to the exhaust gas and can measure the air-fuel ratio. In other words, the protrusion amount L of the air-fuel ratio sensor 36 from the wall 34a can be reduced. The air-fuel ratio sensor 36 does not need to protrude near the center of the exhaust passage 34, as long as it protrudes close to the wall 34a.

[0027] According to this embodiment, bypass passages 40 and 42 are connected to the exhaust passage 34. As shown in Fig. 2, the bypass passage 40 is closer to the wall 34a of the exhaust passage 34 than the bypass passage 42. The bypass passage 42 is closer to the center of the exhaust passage 34 than the bypass passage 40. The inclination angle θ1 of the bypass passage 40 shown in Fig. 3 is smaller than the inclination angle θ2 of the bypass passage 42 shown in Fig. 4.

[0028] Because the inclination angle θ1 of the bypass passage 40 is small, the extension direction of the bypass passage 40 is close to the extension direction of the exhaust passage 34. The exhaust gas introduced from the bypass passage 40 is less likely to collide with the valve body 52 of the WGV 50 and is more likely to concentrate at the center of the exhaust passage 34. The exhaust gas hitting the center of the catalyst 38 allows the catalyst 38 to warm up.

[0029] Because the inclination angle θ2 of the bypass passage 42 is large, the exhaust gas introduced from the bypass passage 42 collides with the valve body 52 of the WGV 50. The collision with the valve body 52 causes the exhaust gas to diffuse. The exhaust gas spreads from the bypass passage 42, which is connected to the inside of the exhaust passage 34, to the vicinity of the wall 34a of the exhaust passage 34. The air-fuel ratio sensor 36 provided on the wall 34a is exposed to the exhaust gas and can detect the air-fuel ratio. Because this provides high detection capability, the air-fuel ratio sensor 36 need only protrude close to the wall 34a rather than to the center of the exhaust passage 34. The protrusion amount L may be, for example, half or less of the diameter of the exhaust passage 34, or may be one-third or less, one-quarter or less, of the diameter.

[0030] As shown in Figure 2, the bypass passages 40 and 42 are aligned in the X-axis direction. As shown in Figures 3 and 4, the WGV 50 opens and closes as the valve element 52 of the WGV 50 moves. When the WGV 50 is open, the valve element 52 is positioned in a direction that intersects with the X-axis direction relative to the bypass passages 40 and 42. The valve element 52 may be positioned in the Y-axis direction, or in a direction other than the Y-axis direction. It is sufficient that the valve element 52 is not aligned with the bypass passages 40 and 42 in the X-axis direction. Exhaust gas flowing through the bypass passage 42 collides with the valve element 52, making it more likely to be dispersed.

[0031] The exhaust passage 34 has a connection portion 35. The connection portion 35 is inclined from the extension direction (Z-axis direction) of the exhaust passage 34. The bypass passages 40 and 42 are connected to the connection portion 35. Because the connection portion 35 is inclined, it is possible to connect a bypass passage 40 with a small inclination angle. The valve body 52 of the WGV 50 is provided at the connection portion 35. The exhaust gas flowing through the bypass passage 42 can be diffused by colliding with the valve body 52.

[0032] The bypass passage 40 is connected to the exhaust passage 30. The bypass passage 42 is connected to the exhaust passage 32. The exhaust gas that bypasses the turbine housing 12 allows the catalyst 38 to be warmed up and the air-fuel ratio sensor 36 to detect the air-fuel ratio.

[0033] In the example of FIG. 1, the internal combustion engine 10 is an eight-cylinder engine. The engine system 100 has two exhaust devices 20. The exhaust passage 30 of the exhaust device 20a is connected to cylinders #1 and #3. The exhaust passage 32 of the exhaust device 20a is connected to cylinders #5 and #7. The exhaust passage 30 of the exhaust device 20b is connected to cylinders #2 and #6. The exhaust passage 32 of the exhaust device 20b is connected to cylinders #4 and #8. The combination of exhaust passages and cylinders may be changed. The internal combustion engine 10 may be a four-cylinder engine other than an eight-cylinder engine. A four-cylinder engine only needs to be provided with one exhaust device 20.

[0034] Although the preferred 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 variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0035] 10 Internal combustion engine 12 Turbine housing 20, 20a, 20b Exhaust system 30, 32, 34 Exhaust passage 35 Connection 36 Air-fuel ratio sensor 38 Catalyst 40, 42 Bypass passage 40a, 42a entrance 50 Wastegate valve 52 Valve body 100 Engine System

Claims

1. a first exhaust passage provided with a turbine housing of the turbocharger; a first bypass passage and a second bypass passage that bypass the turbine housing, are located upstream of the first exhaust passage in the exhaust flow direction, and are connected to the first exhaust passage; a valve provided in a portion of the first exhaust passage where the first bypass passage and the second bypass passage are connected, the valve opening and closing the first bypass passage and the second bypass passage; a catalyst provided in the first exhaust passage and located downstream of the valve; an air-fuel ratio sensor provided in the first exhaust passage, the air-fuel ratio sensor being located downstream of the valve and upstream of the catalyst; the first bypass passage is connected closer to a wall of the first exhaust passage than the second bypass passage, the second bypass passage is connected closer to the center of the first exhaust passage than the first bypass passage, an inclination angle of the first bypass passage with respect to the extension direction of the first exhaust passage being smaller than an inclination angle of the second bypass passage with respect to the extension direction of the first exhaust passage and being equal to or smaller than 10°; The inclination angle of the second bypass passage is 10° or more, The valve body of the valve moves to open and close the valve, When the valve is opened, exhaust gas flowing through the second bypass passage collides with the valve body.

2. An exhaust device for an internal combustion engine as described in claim 1, wherein when the valve is open, the valve body is positioned in a direction relative to the first bypass passage and the second bypass passage that intersects with the direction in which the first bypass passage and the second bypass passage are aligned.

3. the first exhaust passage has a connection portion; the connecting portion is inclined with respect to the extension direction of the first exhaust passage, the first bypass passage and the second bypass passage are connected to the connection portion, 3. The exhaust system for an internal combustion engine according to claim 2, wherein the valve body is provided at the connecting portion.

4. a second exhaust passage and a third exhaust passage; the first bypass passage is connected to the second exhaust passage and the first exhaust passage, 3. An exhaust system for an internal combustion engine according to claim 1, wherein the second bypass passage is connected to the third exhaust passage and the first exhaust passage.

Images