JP2009068381A - Exhaust passage for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust passage for an internal combustion engine capable of suppressing noise while making appropriate quantity of exhaust gas flow out from an upstream side of an exhaust throttle valve to a downstream side thereof through a bypass passage. <P>SOLUTION: The exhaust passage 15 is provided with the exhaust throttle valve 30, a bypass passage 34 communicating to a section at an upstream side and a section at a downstream side of the valve 30, a waste gate valve 35 changing passage cross section of the passage 34. The exhaust throttle valve 30 is driven and closed so as to make a gap between a valve element 32 of the exhaust throttle valve 30 and an inner wall of the exhaust passage 15 smaller at a section near a rotation center L1 of a rotation shaft 31 of the exhaust throttle valve 30 and larger at a section far from the rotation center L1, and the waste gate valve 35 is opened. The bypass passage 34 opens only on a surface at a side where an end part at an downstream side thereof crosses the rotation center L1 out of the inner wall surface of the exhaust passage 15, is set in a shape of which length of an opening in a direction perpendicularly crossing a direction of exhaust gas flow becomes short as the shape of opening section goes more downstream side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust passage of an internal combustion engine provided with an exhaust throttle valve that changes the passage cross-sectional area and a bypass passage that bypasses the exhaust throttle valve.

  Conventionally, an exhaust throttle valve is provided in the middle of an exhaust passage of an internal combustion engine (see, for example, Patent Document 1). As this exhaust throttle valve, a so-called butterfly type that includes a rotational shaft that is rotationally driven and a valve body that is integrally formed with the rotational shaft is usually employed.

  For example, the exhaust throttle valve is driven to open at a normal time and is driven to close when the temperature of the internal combustion engine or the temperature of the exhaust gas purification device provided in the exhaust passage is to be raised early. The When the exhaust throttle valve is closed in this way, the passage cross-sectional area of the exhaust passage becomes very small, and thereafter the pressure upstream of the exhaust throttle valve in the exhaust flow direction (hereinafter simply “upstream side”). As the fuel consumption increases, the pumping loss of the internal combustion engine increases and the fuel consumption increases. As a result, it is possible to obtain an effect that the temperature of the internal combustion engine and the temperature of the exhaust gas purification device quickly rise.

  In addition, the cross-sectional area of the bypass passage and the bypass passage communicating with the exhaust passage of the internal combustion engine through the upstream portion of the exhaust throttle valve and the downstream portion in the exhaust flow direction (hereinafter simply referred to as “downstream side”) is changed. It has been proposed to provide a wastegate valve. In such a device, the waste gate valve is opened when the pressure on the upstream side of the exhaust throttle valve may become excessively high as the exhaust throttle valve is closed. As a result, exhaust gas flows through the bypass passage so as to bypass the exhaust throttle valve, and an excessive increase in pressure on the upstream side of the exhaust throttle valve is avoided.

If the exhaust passage is completely closed when the exhaust throttle valve is closed in the exhaust passage, the pressure on the upstream side of the exhaust throttle valve may increase at an excessively high speed. is there. Therefore, in the exhaust passage, in order to avoid such a sudden rise in pressure, a slightly opened position is set as the valve closing position of the exhaust throttle valve. As a result, even when the exhaust throttle valve is closed, a slight amount of exhaust gas leaks downstream from the gap between the exhaust throttle valve body and the inner wall of the exhaust passage. The rise of the side pressure at an excessively high speed can be suppressed.
JP-A-11-82070

  In the exhaust passage of the internal combustion engine described above, even when the exhaust throttle valve is closed, the exhaust is ejected downstream from the gap between the valve body of the exhaust throttle valve and the inner wall of the exhaust passage. Therefore, if the downstream end of the bypass passage is simply connected to a portion downstream of the exhaust throttle valve in the exhaust passage, the exhaust throttle valve is closed and the waste gate valve is opened. Disturbance occurs due to interference between the leaked exhaust flow and the exhaust flow flowing from the bypass passage into the exhaust passage. If such disturbance occurs, not only will it cause an unnecessary decrease in the amount of outflow when exhaust flows from the upstream side to the downstream side of the exhaust throttle valve through the bypass passage, but if the disturbance is large, The generation of a loud noise (noise) from the wall surface of the exhaust passage.

  The present invention has been made in view of such circumstances, and an object thereof is an internal combustion engine capable of suppressing the generation of noise while allowing an appropriate amount of exhaust gas to flow out from the upstream side to the downstream side of the exhaust throttle valve through the bypass passage. It is to provide an exhaust passage for the engine.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
The invention according to claim 1 is a butterfly type on-off valve comprising a rotary shaft that is rotationally driven and a valve body that is integrally formed with the rotary shaft, and changes the cross-sectional area of the exhaust passage of the internal combustion engine. An exhaust throttle valve, a bypass passage communicating the upstream portion and the downstream portion in the exhaust flow direction of the exhaust throttle valve in the exhaust passage, and a waste gate valve that changes the passage cross-sectional area of the bypass passage As an operation mode of the exhaust throttle valve and the waste gate valve, the gap between the valve body and the inner wall of the exhaust passage is reduced in a portion near the rotation center of the rotation shaft and in a portion far from the rotation center. The opening of the exhaust throttle valve is changed to an opening that increases, and the opening of the waste gate valve is changed to an opening that allows the communication through the bypass passage. In the exhaust passage of the internal combustion engine in which the specific operation mode is set, the bypass passage is a surface on the side where the end on the downstream side in the exhaust flow direction intersects the rotation center of the inner wall surface of the exhaust passage The shape of the downstream portion in the exhaust flow direction in the opened portion is set to a shape in which the opening length in the direction orthogonal to the exhaust flow direction is shorter in the downstream portion. The gist.

  In the above configuration, when the operation mode of the exhaust throttle valve and the waste gate valve is set to the specific operation mode, the amount of exhaust ejected from the gap between the valve body of the exhaust throttle valve and the inner wall of the exhaust passage is the same as that of the exhaust throttle valve. It is small in the portion near the rotation center of the rotation shaft, and increases in a portion far from the rotation center. Therefore, by rotating the end of the bypass passage on the downstream side in the exhaust flow direction (hereinafter simply referred to as “downstream”) in the portion near the rotation center of the rotation shaft of the exhaust throttle valve on the inner wall surface of the exhaust passage, Compared with the case of opening at a portion far from the center, it is possible to suppress the turbulence caused by the interference between the exhaust flow flowing out from the bypass passage and the exhaust flow leaking from the gap.

  In this respect, according to the above-described configuration, the bypass passage is formed on the inner wall surface of the exhaust passage that intersects the rotation center of the rotation shaft of the exhaust throttle valve, that is, on the portion where the amount of exhaust leaking from the gap is small. Since the downstream end is opened, the occurrence of turbulence due to interference of the exhaust flow can be suppressed.

  Further, in the above configuration, when the operation mode of the exhaust throttle valve and the waste gate valve is set to the specific operation mode, the vicinity of the surface far from the rotation center of the rotation shaft of the exhaust throttle valve on the inner wall surface of the exhaust passage , The flow rate of the exhaust gas ejected from the gap increases and the flow velocity increases. Therefore, it can be said that the flow rate of exhaust gas ejected from the gap is small and the flow rate is low in a portion (specific portion) sandwiched between portions where the flow rate of exhaust gas is high and the flow rate is high. Here, since the exhaust gas leaked from the gap is ejected so as to spread in a wider range toward the downstream side, the specific portion is a portion extending from the exhaust throttle valve to the starting point and narrower toward the downstream side. In addition, a portion (specific wall surface) in contact with the specific portion on the inner wall surface of the exhaust passage has a shape extending from the exhaust throttle valve as a starting point, and a shape having a shorter length in a direction orthogonal to the exhaust flow direction toward the downstream side. Become. In order to suppress the occurrence of turbulence due to the interference of the exhaust flow described above, the end portion on the downstream side of the bypass passage in the specific wall surface, in other words, the portion where the flow rate of the exhaust gas ejected from the gap is small and the flow velocity is low. It is desirable to make it open.

  In this regard, according to the above configuration, the shape of the downstream portion of the opening portion of the bypass passage on the downstream side of the exhaust throttle valve can be a shape corresponding to the specific wall surface, and the exhaust flow rate is large and the flow rate is high. While suppressing the opening of the bypass passage in the high portion, i.e., the portion where the turbulence caused by the interference of the exhaust flow is likely to increase when the downstream end of the bypass passage is opened, the opening area is reduced. It becomes possible to enlarge.

  Therefore, according to the above configuration, it is possible to suppress the generation of noise while allowing an appropriate amount of exhaust gas to flow out from the upstream portion in the exhaust flow direction of the exhaust throttle valve to the downstream portion through the bypass passage.

  According to a second aspect of the present invention, in the exhaust passage of the internal combustion engine according to the first aspect, the shape of the entire opened portion of the bypass passage is orthogonal to the exhaust flow direction as the downstream portion in the exhaust flow direction. The gist is that the opening length in the direction is set to a short shape.

According to the above configuration, it is possible to further increase the opening area of the exhaust passage while suppressing the opening of the bypass passage at a portion where the flow rate of exhaust gas is high and the flow velocity is high.
According to a third aspect of the present invention, in the exhaust passage of the internal combustion engine according to the first or second aspect, the exhaust passage is provided with an exhaust purification device for purifying exhaust gas passing through the interior thereof, and the exhaust throttle valve and The gist of the wastegate valve is that it is provided downstream of the exhaust purification device in the exhaust flow direction.

  According to the above configuration, in the device in which the exhaust throttle valve is provided on the downstream side of the exhaust purification device in order to quickly raise the temperature of the exhaust purification device, the generation of noise can be suitably suppressed.

Hereinafter, an embodiment in which an exhaust passage of an internal combustion engine according to the present invention is embodied will be described.
FIG. 1 shows a schematic configuration of an internal combustion engine to which an exhaust passage according to the present embodiment is applied.

  As shown in FIG. 1, the internal combustion engine 10 is provided with a fuel injection valve 12 that injects fuel directly into the combustion chamber 11. Fuel is supplied to the fuel injection valve 12 from a fuel tank 14 through a fuel pump 13.

  An exhaust gas purification device 20 for purifying exhaust gas is provided in the exhaust passage 15 of the internal combustion engine 10. This exhaust purification device 20 includes an oxidation catalytic converter 21 that oxidizes and purifies hydrocarbons (HC) and carbon monoxide (CO) in exhaust gas, and a filter 22 that collects particulate matter (PM) in exhaust gas. I have.

  The exhaust passage 15 is provided with a fuel addition valve 23 for adding fuel into the exhaust gas at a position upstream of the exhaust purification device 20 in the exhaust flow direction (hereinafter simply “upstream side”). The fuel pump 13 is communicated with the fuel addition valve 23 through a communication pipe 24, and fuel is supplied from the fuel tank 14 through the fuel pump 13.

  Further, an exhaust throttle valve 30 for changing the cross-sectional area of the exhaust passage 15 is provided in the exhaust passage 15 at a position downstream of the exhaust purification device 20 in the exhaust flow direction (hereinafter simply “downstream side”). Is provided. The exhaust throttle valve 30 is a so-called butterfly on-off valve configured by a rotational shaft 31 that is rotationally driven and a disc-shaped valve body 32 that is integrally formed with the rotational shaft 31. An actuator 33 is connected to the rotation shaft 31 of the exhaust throttle valve 30. The operating state of the exhaust throttle valve 30 through the driving of the actuator 33 changes to one of a state where the passage cross-sectional area of the exhaust passage 15 is large (valve open state) and a state where the passage cross-sectional area is very small (valve closed state). Can be switched.

  The exhaust passage 15 is provided with a bypass passage 34 that communicates the upstream portion and the downstream portion of the exhaust throttle valve 30, and a waste gate valve 35 is provided in the bypass passage 34. Yes. The waste gate valve 35 is a self-regulating valve, and is automatically activated when the pressure difference between a portion upstream of the exhaust throttle valve 30 and a portion downstream of the exhaust throttle valve 30 in the exhaust passage 15 exceeds a predetermined value. Open. By providing the bypass passage 34 and the waste gate valve 35, when the exhaust throttle valve 30 is closed and the upstream pressure becomes high, the waste gate valve 35 is opened to bypass the exhaust throttle valve 30. Thus, the exhaust gas flows and the pressure on the upstream side of the exhaust throttle valve 30 is prevented from becoming excessively high.

  The intake passage 16 of the internal combustion engine 10 is provided with an intake air amount sensor 41 for detecting the amount of air taken into the combustion chamber 11 (intake air amount GA). A rotation speed sensor 42 for detecting the rotation speed of the output shaft 17 (engine rotation speed NE) is provided in the vicinity of the output shaft 17 of the internal combustion engine 10.

  The electronic control unit 40 includes a drive circuit for driving the fuel injection valve 12, the fuel addition valve 23, the actuator 33, and the like in addition to the CPU, ROM, and RAM. The electronic control unit 40 takes in output signals from various sensors and performs various calculations, and controls the driving of the fuel injection valve 12, the fuel addition valve 23, and the exhaust throttle valve 30 (specifically, the actuator 33) based on the calculation results. To do.

  The drive control of the fuel injection valve 12 is basically executed to adjust the output torque of the internal combustion engine 10. Specifically, a control target value (target injection amount) for the fuel injection amount is obtained based on the intake air amount GA and the engine rotational speed NE at that time, and the target injection amount and the actual fuel injection amount are obtained. The fuel injection valve 12 is driven to open so as to match.

  The drive control of the fuel addition valve 23 is executed to remove PM accumulated on the filter 22. Specifically, the fuel addition valve 23 is intermittently opened for a predetermined period. Then, by executing the process for opening the fuel addition valve 23 (PM removal process) as described above, the fuel is continuously added to the exhaust gas, and the temperature of the filter 22 is increased by oxidizing the fuel. Become. As a result, the PM deposited on the filter 22 burns and becomes carbon dioxide (CO 2) and water (H 2 O) and is discharged outside the exhaust passage 15.

The drive control of the exhaust throttle valve 30 is executed in order to properly remove PM in the PM removal process.
When the operating region of the internal combustion engine 10 is a low load region where the amount of intake air is small, the amount of exhaust discharged from the combustion chamber 11 to the exhaust passage 15 is small, and the heat that the exhaust passing through the exhaust passage 15 per unit time has. The total amount of is also small. Therefore, the temperature of the filter 22 may not be sufficiently increased when the fuel is added to the exhaust gas through the valve opening drive of the fuel addition valve 23.

  In view of this point, in the present embodiment, the exhaust throttle valve 30 is driven to be closed when the operation region of the internal combustion engine 10 is a low load region during execution of the PM removal process. Since the exhaust throttle valve 30 is driven to close in this manner, the pressure in the portion upstream of the exhaust throttle valve 30 in the exhaust passage 15 is increased and the pumping loss of the internal combustion engine 10 is increased. The amount of fuel injected from the fuel injection valve 12 increases in order to compensate for the decrease in the engine output accompanying this. As a result, the total amount of heat of the exhaust exhausted from the combustion chamber 11 to the exhaust passage 15 per unit time increases, and the temperature of the filter 22 quickly rises, and the PM accumulated in the filter 22 Is properly removed.

  On the other hand, even when the PM removal process is being executed, the exhaust throttle valve 30 is driven to open when the operating range of the internal combustion engine 10 is in the middle and high load range. This is because the total amount of heat of the exhaust gas discharged from the combustion chamber 11 to the exhaust passage 15 per unit time is large at this time, and the temperature of the filter 22 is sufficiently increased without the exhaust throttle valve 30 being driven to close. Because it is possible. The exhaust throttle valve 30 is also driven to open when the PM removal process is not executed.

  In the present embodiment, when the exhaust throttle valve 30 is driven to be closed, a small amount of exhaust gas leaks from the gap between the valve body 32 of the exhaust throttle valve 30 and the inner wall of the exhaust passage 15. It has become. This is to prevent the pressure in the upstream portion from rising at an excessively high speed immediately after the exhaust throttle valve 30 is closed.

  FIG. 2 schematically shows a cross-sectional structure of the exhaust passage 15 in the portion where the exhaust throttle valve 30 is disposed. 2A shows a cross-sectional shape in a direction along the extending direction of the exhaust passage 15, and FIG. 2B shows a cross-sectional shape in a direction orthogonal to the extending direction.

  As shown in FIG. 2, the structure in which a small amount of exhaust gas leaks from the gap is slightly larger than the operating position of the exhaust throttle valve 30 where the gap becomes uniform around the valve body 32 (position indicated by the broken line in FIG. 2). This is realized by setting the operating position (the position indicated by the solid line in FIG. 2) at the opening as the operating position of the exhaust throttle valve 30 when the valve is closed.

  Thus, in the present embodiment, when the exhaust throttle valve 30 is closed, the gap between the valve body 32 of the exhaust throttle valve 30 and the inner wall of the exhaust passage 15 is the rotational center of the rotary shaft 31 of the exhaust throttle valve 30. It becomes small in a portion close to L1 and large in a portion far from the rotation center L1. In order to facilitate understanding in FIG. 2, the gap between the valve body 32 of the exhaust throttle valve 30 and the inner wall of the exhaust passage 15, or the portion near the rotation center L1 and the portion far from the rotation center L1. The difference from the gap is exaggerated.

Hereinafter, the opening shape of the downstream end portion of the bypass passage 34 on the inner wall surface of the exhaust passage 15 will be described with reference to FIG. 3.
FIG. 3 shows a cross-sectional structure of the exhaust passage 15 in the vicinity of the portion where the exhaust throttle valve 30 is disposed and the periphery thereof. In FIG. 3, the operating position of the exhaust throttle valve 30 when the valve is closed is indicated by a solid line, and the operating position of the exhaust throttle valve 30 when the valve is opened is indicated by a two-dot chain line. Show.

  As shown in FIG. 3, the downstream end of the bypass passage 34 is a surface on the inner wall surface of the exhaust passage 15 that is far from the rotation center L1 of the rotation shaft 31 of the exhaust throttle valve 30 (in FIG. 3). The upper and lower portions are not opened, but are opened on the surface (the central portion in the vertical direction in FIG. 3) on the side that intersects with the rotation center L1 of the rotation shaft 31. That is, the downstream end of the bypass passage 34 is opened only on the surface of the inner wall surface of the exhaust passage 15 that intersects the rotation center L1.

  Moreover, the opening shape in the exhaust passage 15 at the downstream end of the bypass passage 34 is gradually shortened in the direction (vertical direction in FIG. 3) perpendicular to the exhaust flow direction toward the downstream portion. It is set to a substantially trapezoidal shape. Incidentally, in the present embodiment, the inner wall of the downstream portion of the bypass passage 34 is formed in a shape having no corners for processing reasons, and the four openings in the substantially trapezoidal shape as described above are formed. Each of the corners has a curved shape.

Hereinafter, the effect | action by setting the opening shape of the downstream edge part of the bypass channel 34 in the exhaust channel 15 in this way is demonstrated.
In the exhaust passage 15 of the internal combustion engine 10, when the exhaust throttle valve 30 is closed, the gap between the valve body 32 of the exhaust throttle valve 30 and the inner wall of the exhaust passage 15 is rotated by the rotation shaft 31 of the exhaust throttle valve 30. It becomes small in a portion near the center L1 and large in a portion far from the rotation center L1.

  For this reason, when the exhaust throttle valve 30 is driven to close and the waste gate valve 35 is opened, the amount of exhaust gas ejected from the gap is determined by the rotation shaft 31 of the exhaust throttle valve 30. In the portion close to the rotation center L1, and increases in the portion far from the rotation center L1.

  Accordingly, by opening the downstream end of the bypass passage 34 in the portion near the rotation center L1 on the inner wall surface of the exhaust passage 15, the bypass passage is compared with the case of opening the portion far from the rotation center L1. It is possible to suppress the turbulence caused by the interference between the flow of exhaust gas flowing out from 34 and the flow of exhaust gas leaking from the gap.

  In the exhaust passage 15, the downstream end portion of the bypass passage 34 is opened only on the surface of the inner wall surface that intersects the rotation center L <b> 1, that is, in the portion where the amount of exhaust leaking from the gap is small. . Therefore, it is possible to suppress the occurrence of turbulence due to interference between the flow of exhaust flowing out of the bypass passage 34 and the flow of exhaust leaking from the gap.

  Further, in the exhaust passage 15 of the internal combustion engine 10, in the vicinity of the surface on the far side from the rotation center L <b> 1 of the rotation shaft 31 of the exhaust throttle valve 30 on the inner wall surface of the exhaust passage 15 when the specific operation state is reached. The flow rate of the exhaust gas ejected from the gap increases and the flow velocity increases. Therefore, it can be said that the flow rate of the exhaust gas ejected from the gap is small and the flow velocity is low in a portion (specific portion) sandwiched between portions where the flow rate of the exhaust gas is high and the flow velocity is high.

FIG. 4 schematically shows the cross-sectional structure of the exhaust passage 15 around the exhaust throttle valve 30 and the state of the exhaust flow.
As indicated by arrows in FIG. 4, the exhaust gas leaking from the gap between the valve element 32 of the exhaust throttle valve 30 and the inner wall of the exhaust passage 15 is ejected so as to spread in a wider range toward the downstream side. The portion of the flow of exhaust gas that is ejected and that has a high flow rate and a high flow velocity also has a shape that spreads in a wider range toward the downstream side. Further, the specific portion, which is a portion sandwiched between portions where the flow rate of exhaust gas is large and the flow velocity is high, has a shape extending from the exhaust throttle valve 30 as a starting point, and becomes narrower toward the downstream side. Furthermore, the specific wall surface that is a portion in contact with the specific portion of the inner wall surface of the exhaust passage 15 (portion “A” sandwiched by a chain line in FIG. 4) extends from the exhaust throttle valve 30 to the downstream side. As it goes to the side, the length in the direction (vertical direction in FIG. 4) orthogonal to the exhaust flow direction becomes shorter.

  Here, in order to suppress the occurrence of turbulence due to interference between the flow of the exhaust gas flowing out of the bypass passage 34 and the flow of the exhaust gas leaking from the gap, the gap is not limited to the specific wall surface (in other words, the inner wall surface of the exhaust passage 15. It is desirable to open the downstream end portion of the bypass passage 34 in a portion where the flow rate of the exhaust gas ejected from the pipe is small and the flow velocity is low.

  In the present embodiment, the shape of the opening portion of the bypass passage 34 on the downstream side of the exhaust throttle valve 30 is shorter in the direction orthogonal to the exhaust flow direction toward the downstream side, that is, the shape corresponding to the specific wall surface. Is formed. Therefore, when setting the portion where the downstream end of the bypass passage 34 is opened, the opening portion is substantially rectangular or square, or the shape that is longer in the direction orthogonal to the exhaust flow direction toward the downstream side. Compared with the case where it forms, the opening part can be easily accommodated in the part which hits the said specific wall surface. Therefore, in the portion where the flow rate of the exhaust gas is high and the flow velocity is high (that is, the portion where the turbulence generated by interference of the exhaust flow is likely to increase when the downstream end of the bypass passage 34 is opened), the bypass passage 34. It is possible to increase the opening area while suppressing the opening.

  As described above, according to the present embodiment, the occurrence of turbulence due to the interference between the exhaust flow flowing out of the bypass passage 34 and the exhaust flow leaking from the gap is suppressed, and the bypass passage 34 on the downstream side of the exhaust throttle valve 30 is suppressed. The opening area of the opening portion can be increased. Therefore, when the operation modes of the exhaust throttle valve 30 and the waste gate valve 35 are the specific operation modes, an appropriate amount of exhaust gas is discharged from the upstream portion of the exhaust throttle valve 30 to the downstream portion through the bypass passage 34. Generation of noise can be suppressed while flowing out.

  By the way, when the exhaust throttle valve 30 is in a closed state, portions along the portion where the flow rate of exhaust gas leaking from the gap is high and the flow velocity is high (the portion indicated by “A” and the portion indicated by “B” in FIG. 4). The pressure on the “A” side portion at the boundary of In the present embodiment, since the shape of the opening portion of the bypass passage 34 on the downstream side of the exhaust throttle valve 30 is formed in a shape having a shorter length in the direction orthogonal to the exhaust flow direction as it goes downstream, The edge part of a part can be arrange | positioned in the position along the part which the exhaust_gas | exhaustion mentioned above flows at high speed. Therefore, it is possible to open the downstream end of the bypass passage 34 at a portion where the pressure is relatively low in the exhaust passage 15, and the downstream portion from the upstream portion of the exhaust throttle valve 30 through the bypass passage 34. It becomes possible to allow the exhaust gas to smoothly flow into the portion.

  Incidentally, when the distance between the opening portion of the bypass passage 34 on the downstream side of the exhaust throttle valve 30 and the above-described portion where the flow rate of exhaust gas is large and the flow velocity is high, the exhaust passage flows into the opening portion of the bypass passage 34. It is also conceivable that turbulence may occur due to interference between the exhaust gas flowing through the exhaust gas 15 and the exhaust gas flowing from the gap and having a high flow rate and a high flow velocity. Here, since the passage sectional area of the bypass passage 34 is smaller than the passage sectional area of the exhaust passage 15, the flow velocity of the exhaust gas flowing into the exhaust passage 15 from the opening portion of the bypass passage 34 is highest in the vicinity of the opening portion. , It decreases rapidly as it goes downstream from the opening. Therefore, by forming the opening portion of the bypass passage 34 at a position that is moderately separated from the portion where the flow rate of exhaust gas is high and the flow velocity is high, the exhaust gas flowing from the opening portion and flowing through the exhaust passage 15 flows at the flow velocity. After the air flow becomes very low, the flow rate of the exhaust gas flowing out of the gap and interfering with the flow rate is high. Therefore, by forming the opening portion of the bypass passage 34 at a position that is moderately separated from the portion where the flow rate is high and the flow velocity is high, the exhaust gas flowing from the opening portion and flowing through the exhaust passage 15 is ejected from the gap. Therefore, even when the exhaust flowing in the air interferes with the exhaust gas, it is possible to avoid the occurrence of a large disturbance due to the interference.

As described above, according to the present embodiment, the effects described below can be obtained.
The generation of noise can be suppressed while allowing an appropriate amount of exhaust gas to flow from the upstream portion of the exhaust throttle valve 30 to the downstream portion through the bypass passage 34.

The embodiment described above may be modified as follows.
In the above-described embodiment, a process for performing so-called post-injection, in which fuel is injected from the fuel injection valve 12 during the expansion stroke or exhaust stroke of the internal combustion engine 10 separately from fuel injection for generating torque, is referred to as PM removal processing. It can also be applied to an executing engine system. In such a configuration, the fuel addition valve 23 and the communication pipe 24 can be omitted.

  If the opening shape in the exhaust passage 15 at the downstream end of the bypass passage 34 is a shape in which the opening length becomes shorter toward the downstream portion, for example, the exhaust flow direction toward the downstream portion The shape can be arbitrarily changed, such as a shape in which the opening length in the orthogonal direction becomes shorter stepwise.

  -Of the opening portions in the exhaust passage 15 at the downstream end of the bypass passage 34, only the downstream portion may be formed in a shape such that the opening length becomes shorter toward the downstream side. It can be said that the portion on the downstream side of the exhaust throttle valve 30 is a portion suitable for forming the opening portion because the flow velocity of the exhaust gas ejected from the gap becomes lower. On the other hand, since the specific wall surface (portion indicated by “A” in FIG. 4) becomes narrower at a portion downstream from the exhaust throttle valve 30, it is difficult to secure a space for forming the opening portion. It can be said that it is a part. According to the said structure, the space for forming the said opening part in such a downstream part can be ensured suitably.

  The present invention can also be applied to an exhaust passage provided with an exhaust throttle valve upstream from the exhaust purification device. The point is that the present invention is an exhaust passage provided with a bypass passage communicating the upstream portion and the downstream portion of the exhaust throttle valve in the exhaust passage and a waste gate valve for changing the passage sectional area of the bypass passage. Is applicable. As an exhaust throttle valve provided upstream of the exhaust purification device, an exhaust throttle valve for quickly increasing the temperature by closing when the temperature of the internal combustion engine is low, or when decelerating the internal combustion engine By closing the valve, an exhaust throttle valve for enhancing the effect of so-called engine braking can be exemplified.

1 is a block diagram showing a schematic configuration of an internal combustion engine to which an exhaust passage according to an embodiment embodying the present invention is applied. (A) And (b) The schematic which shows typically the cross-section of the exhaust passage in the arrangement | positioning part of an exhaust throttle valve. Sectional drawing which shows the cross-sectional structure of the exhaust passage in the arrangement | positioning part of an exhaust throttle valve, and its periphery. 1 is a schematic view schematically showing a cross-sectional structure of an exhaust passage around an exhaust throttle valve and a state of exhaust flow.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Combustion chamber, 12 ... Fuel injection valve, 13 ... Fuel pump, 14 ... Fuel tank, 15 ... Exhaust passage, 16 ... Intake passage, 17 ... Output shaft, 20 ... Exhaust purification device, 21 ... Oxidation Catalytic converter, 22 ... filter, 23 ... fuel addition valve, 24 ... communication pipe, 30 ... exhaust throttle valve, 31 ... rotating shaft, 32 ... valve element, 33 ... actuator, 34 ... bypass passage, 35 ... waste gate valve, 40 ... an electronic control unit, 41 ... an intake air amount sensor, 42 ... a rotational speed sensor.

Claims (3)

A butterfly-type on-off valve comprising a rotary shaft that is rotationally driven and a valve body integrally formed with the rotary shaft, and an exhaust throttle valve that changes a cross-sectional area of the exhaust passage of the internal combustion engine; A bypass passage communicating the upstream portion and the downstream portion of the exhaust throttle direction with respect to the exhaust throttle valve; and a waste gate valve that changes a cross-sectional area of the bypass passage; and the exhaust throttle valve and the waste gate As one mode of operation of the valve, the exhaust throttle valve is adjusted so that a gap between the valve body and the inner wall of the exhaust passage is reduced in a portion near the rotation center of the rotation shaft and increased in a portion far from the rotation center. The specific operation mode is set such that the opening of the waste gate valve is changed to an opening that allows the communication through the bypass passage. In an exhaust passage of an internal combustion engine comprising been,
The end of the bypass passage on the downstream side in the exhaust flow direction is opened only on the surface of the inner wall surface of the exhaust passage that intersects the rotation center, and the downstream portion in the exhaust flow direction in the opened portion. An exhaust passage for an internal combustion engine, characterized in that the opening portion in the direction orthogonal to the exhaust flow direction is set to be shorter in the shape of the downstream portion. In the exhaust passage of the internal combustion engine according to claim 1,
The exhaust of the internal combustion engine characterized in that the bypass passage is set such that the shape of the entire opened portion is shorter in the direction orthogonal to the exhaust flow direction toward the downstream side of the exhaust flow direction. aisle. The exhaust passage of the internal combustion engine according to claim 1 or 2,
The exhaust passage is provided with an exhaust purification device that purifies the exhaust passing through the interior,
The exhaust passage of an internal combustion engine, wherein the exhaust throttle valve and the waste gate valve are provided downstream of the exhaust purification device in the exhaust flow direction.

Images