JP2007285265A - Exhaust structure for exhaust system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust structure for an exhaust system capable of effectively activating a catalytic converter. <P>SOLUTION: This structure is provided with a first exhaust pipe 6 guiding exhaust gas discharged from a turbine wheel 45 of a turbocharger 4 to the catalytic converter 5, and a second exhaust pipe 7 guiding exhaust gas discharged from an engine 1 to the catalytic converter 5 with bypassing the turbine wheel 45 of the turbocharger 4. Diameter of the second exhaust pipe 7 is reduced to reduce surface area by dividing an exhaust pipe guiding exhaust gas discharged from the turbine wheel 45 to the catalyst, and an exhaust pipe guiding exhaust gas to the catalyst without making the same pass through the turbine wheel 45, drop of temperature of exhaust gas passing through the second exhaust pipe can be reduced. Consequently, the catalytic converter is quickly warmed up and is activated to accelerate purification of exhaust gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust structure mounted on a vehicle provided with an exhaust turbine drive supercharger (turbocharger). In particular, the present invention relates to a technology that promotes early activation of a catalyst and promotes purification of exhaust gas.

  An engine equipped with a turbocharger obtains a high output by driving a turbine of the turbocharger using the pressure of exhaust gas and supercharging intake air by a compressor connected to the turbine. In general, the turbocharger is provided with an exhaust bypass device, and when the supercharging pressure reaches a predetermined pressure, the waste gate valve is opened to release the exhaust gas pressure downstream of the turbine. Prevents excessive increase of supercharging pressure.

  In recent years, due to environmental considerations, efforts have been made to activate the catalytic converter immediately after the engine is started so as not to release harmful pollutants into the atmosphere. The conversion of pollutants by the catalytic converter is generally performed only when a sufficiently high temperature of 400 ° C. or higher is reached. For this reason, especially when the internal combustion engine is cold-started, the catalyst temperature does not reach a predetermined temperature, so that the pollutants released from the internal combustion engine remain untreated or are treated insufficiently. The discharged time will continue to some extent.

  As a piping configuration on the downstream side of the turbine, a configuration shown in Patent Document 1 is generally employed (see FIG. 1). The piping structure shown in FIG. 1 introduces exhaust gas 101 that has passed through the turbine to a bypass passage 100 for adjusting the supercharging pressure, and introduces the exhaust gas into the catalytic converter through a single pipe. When starting the engine, the gas introduction port 102 of the bypass passage 100 is largely opened so that most of the exhaust gas flows into the catalytic converter from the bypass passage 100, so that the catalyst can be activated early.

  In Patent Document 2, in a turbine housing that houses a turbine wheel, an exhaust gas inflow port and an outflow port are disposed close to each other, and preferably arranged on an extension line to each other. The length of the bypass conduit connecting to the turbine is very short, and a configuration is disclosed in which most of the exhaust gas passing through the turbine passes through the bypass conduit and is guided to the catalytic converter on the downstream side.

JP 2002-195046 A Special Table 2000-504803

  However, in a configuration in which the exhaust gas that has passed through the turbine and the exhaust gas that has passed through the bypass for adjusting the boost pressure flow in the same pipe, the pipe must be made thicker, and the heat capacity of the pipe becomes larger, resulting in a catalytic converter. There is a problem that the temperature of the exhaust gas is deprived before reaching the temperature and the temperature is lowered.

  In addition, the bypass conduit disclosed in Patent Document 2 must be provided with an expensive actuator such as a motor and a solenoid during normal times other than when the engine is started, and control for opening and closing the valve leading to the bypass conduit must be performed. There is a problem of becoming higher.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an exhaust structure of an exhaust system capable of efficiently activating a catalytic converter.

In order to achieve such an object, the exhaust structure of the exhaust system of the present invention includes a first exhaust pipe that guides exhaust gas discharged from a turbine of a supercharger to an exhaust purification catalytic device, and exhaust gas discharged from an internal combustion engine. And a second exhaust pipe that guides gas to the exhaust purification catalyst device by bypassing the turbine of the supercharger.
As described above, the present invention has divided the exhaust pipe for guiding the exhaust gas discharged from the turbine to the exhaust purification catalytic device and the exhaust pipe for guiding the exhaust gas to the exhaust purification catalytic device without passing through the turbine. Thus, the diameter of the second exhaust pipe can be reduced to reduce the surface area, and the temperature drop of the exhaust gas passing through the second exhaust pipe can be reduced. For this reason, the exhaust purification catalyst device can be quickly warmed and activated to promote the purification of exhaust gas.

In the exhaust structure of the exhaust system, the second exhaust pipe may be attached so as to guide the exhaust gas to substantially the center of the exhaust purification catalyst device.
Since the exhaust gas is led to substantially the center of the exhaust purification catalyst device, it is possible to reduce the temperature distribution of the catalyst of the exhaust purification catalyst device and prevent the exhaust purification catalyst device from cracking.

In the exhaust structure of the exhaust system, the second exhaust pipe may guide the exhaust gas through the first exhaust pipe to the substantial center of the exhaust purification catalyst device.
Therefore, the exhaust gas from the first exhaust pipe and the exhaust gas from the second exhaust pipe can be uniformly fed into the entire exhaust purification catalyst device. Furthermore, since high-temperature exhaust gas that does not pass through the turbine can be guided to the substantial center of the exhaust purification catalyst device, the temperature distribution of the catalyst of the exhaust purification catalyst device can be reduced to prevent cracking of the exhaust purification catalyst device. Can do.

In the exhaust structure of the exhaust system, the center of the joint between the first exhaust pipe and the exhaust purification catalyst device may coincide with the center of the joint between the second exhaust pipe and the exhaust purification catalyst device. .
Therefore, the exhaust gas can be uniformly fed into the entire exhaust purification catalyst device.

In the exhaust structure of the exhaust system, end portions of the first exhaust pipe and the second exhaust pipe on the exhaust purification catalyst device side may be aligned with a joint surface with the exhaust purification catalyst device.
Therefore, the flow rate of the exhaust gas flowing into the exhaust purification catalyst device can be made constant, and the temperature difference in the catalyst can be reduced as much as possible.

In the exhaust structure of the exhaust system, the second exhaust pipe may be cut at a joint surface with the first exhaust pipe.
Therefore, since the exhaust gas flowing through the second exhaust pipe flows through the first exhaust pipe having a large surface area from the middle, the flow rate of the exhaust gas flowing through the second exhaust pipe can be reduced. For this reason, it is possible to reduce the temperature distribution of the catalyst of the exhaust purification catalyst device and prevent the exhaust purification catalyst device from cracking.

  According to the present invention, the catalytic converter can be activated efficiently.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

First, the configuration of the present embodiment will be described with reference to FIG. FIG. 2 shows the configuration of the engine 1 and its peripheral part.
A turbocharger 4 as a supercharger is provided between the intake passage 2 and the exhaust passage 3 of the engine 1, and intake air is supercharged to each cylinder of the engine 1 by the turbocharger 4. A catalytic converter 5 for purifying NOx in the exhaust gas is provided downstream of the turbocharger 4 in the exhaust passage 3.

FIG. 3 shows the external shape of the turbocharger 4. The turbocharger 4 includes a center housing 41, a turbine housing 42, and a compressor housing 43.
In the turbine housing 42, a turbine wheel 45 that is rotated by exhaust gas fed from an exhaust manifold 31 that constitutes a part of the exhaust passage 3 is provided. The compressor housing 43 is provided with a compressor wheel 46 for forcibly sending the air in the intake passage 2 to the combustion chamber of the engine 1. The turbine wheel 45 and the compressor wheel 46 are connected via a rotor shaft 47 so as to be integrally rotatable. When exhaust gas is blown onto the turbine wheel 45 and the turbine wheel 45 rotates, the compressor wheel 46 also rotates, and the air in the intake passage 2 is forcibly sent into the combustion chamber of the engine 1.

  Further, the catalytic converter 5 is a carrier on which a NOx occlusion reduction type catalyst is supported, and occludes NOx in the exhaust when the air-fuel ratio of the exhaust is lean, and occluded NOx when the air-fuel ratio is rich. Is reduced and released.

  In the present embodiment, as shown in FIG. 2, the first exhaust pipe 6 that leads exhaust gas discharged from the turbine wheel 45 of the turbocharger 4 to the catalytic converter 5, and the exhaust gas discharged from the engine 1 is converted to the turbocharger 4. A second exhaust pipe 7 that bypasses the turbine wheel 45 and leads to the catalytic converter 5 is provided. By separating the exhaust pipe that guides the exhaust gas discharged from the turbine wheel 45 to the catalytic converter 5 and the exhaust pipe that guides the exhaust gas to the catalytic converter 5 without passing through the turbine wheel 45, the second exhaust pipe 7 is separated. The surface area can be reduced by reducing the diameter of the exhaust gas and the temperature drop of the exhaust gas passing through the second exhaust pipe 7 can be reduced. Since the exhaust gas passing through the second exhaust pipe 7 is a gas that does not pass through the turbine wheel 45, the exhaust gas is kept at a higher temperature than the exhaust gas that has worked on the turbine wheel 45. By guiding the temperature drop of the high-temperature gas to the catalytic converter 5 to the minimum, the catalytic converter 5 can be quickly warmed and activated, and exhaust gas purification can be promoted.

  FIG. 4A shows a configuration in which the first exhaust pipe 6 and the second exhaust pipe 7 are viewed from the exhaust gas inlet side. As shown in FIG. 4A, the first exhaust pipe 6 and the second exhaust pipe 7 have independent exhaust gas intakes, and the exhaust gas intake 61 of the first exhaust pipe 6 is shown in FIG. Is connected to the exhaust port of the turbocharger 4 as shown in FIG. The exhaust gas intake 71 of the second exhaust pipe 7 is connected to the exhaust passage 3 upstream of the turbine wheel 45 of the turbocharger 4. Further, exhaust flanges 60 are provided at the exhaust gas intakes 61 and 71 of the first exhaust pipe 6 and the second exhaust pipe 7. The exhaust flange 60 is provided with a bolt hole. The first exhaust pipe 6 and the turbocharger are fixed, and the second exhaust pipe 7 and the exhaust passage 3 are fixed by the bolts through the bolt holes.

  FIG. 4B shows a cross-sectional shape of the first exhaust pipe 6, the second exhaust pipe 7, and the catalytic converter 5 cut along the XY line shown in FIG. 4A. As shown in FIG. 4B, a valve 70 is provided in the vicinity of the exhaust gas inlet 71 of the second exhaust pipe 7. In this embodiment, the valve 70 is opened when the engine 1 is started so that the exhaust gas flows into the second exhaust pipe 7, and the motor is driven by electrical control, and the driving force of the motor is used. The valve 70 is opened and closed. In addition to this, a spring that opens the valve 70 may be provided, and the valve 70 may be opened using a spring force.

A detailed configuration of the first exhaust pipe 6 and the second exhaust pipe 7 will be described with reference to FIG. As shown in FIG. 5A, the second exhaust pipe 7 extends through the first exhaust pipe 6 to the boundary surface 8 with the catalytic converter 5. Further, when the first exhaust pipe 6 and the second exhaust pipe 7 are cut perpendicularly to the vertical direction, the second exhaust pipe 7 is placed in the first exhaust pipe 6 so that the centers of the respective cut surfaces substantially coincide with each other. Through. Therefore, the exhaust gas from the first exhaust pipe 6 and the exhaust gas from the second exhaust pipe 7 can be uniformly fed into the entire catalytic converter 5. Furthermore, since the high-temperature exhaust gas that does not pass through the turbine wheel 45 can be guided to the approximate center of the catalytic converter 5, the temperature distribution of the catalyst in the catalytic converter 5 can be reduced to prevent cracking of the catalytic converter 5. it can.
Further, by aligning the end portions of the first exhaust pipe 6 and the second exhaust pipe 7 in contact with the catalytic converter 5 at the boundary surface 8 with the catalytic converter 5, the flow velocity of the exhaust gas flowing into the catalytic converter 5 is constant. Thus, the temperature difference in the catalyst can be minimized.

  Moreover, you may cut the edge part of the 2nd exhaust pipe 7 in the intermediate part in the 1st exhaust pipe 6, without extending to the boundary surface 8, as shown in FIG.5 (B). Further, as shown in FIG. 5C, the second exhaust pipe 7 can be cut by the exhaust pipe surface of the first exhaust pipe 6. By adopting such a structure, the exhaust gas flowing through the second exhaust pipe 7 flows through the first exhaust pipe 6 having a large surface area from the middle, so the flow rate of the exhaust gas flowing through the second exhaust pipe 7 is reduced. Can be late. For this reason, it is possible to reduce the temperature distribution of the catalyst of the catalytic converter 5 and prevent the catalytic converter 5 from cracking.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

It is a figure which shows the structure of the conventional exhaust pipe. It is a figure which shows the whole structure of this invention. It is a figure which shows the external shape of a turbocharger. (A) is the block diagram which looked at the 1st exhaust pipe, the 2nd exhaust pipe, and the catalytic converter from the exhaust-gas inlet side, (B) is the structure of the cross section cut | disconnected by the XY line shown to (A). FIG. It is a figure which shows the cross-sectional shape of a 1st exhaust pipe and a 2nd exhaust pipe, (A) is the structure which extended the edge part of the 1st exhaust pipe to the boundary surface of a catalytic converter, (B) is 1st It is the structure which cut | disconnected the edge part of the exhaust pipe in the middle of the 2nd exhaust pipe, (C) is a figure which shows the structure which cut | disconnected the edge part of the 1st exhaust pipe by the piping surface of the 2nd exhaust pipe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake path 3 Exhaust path 4 Turbocharger 5 Catalytic converter 6 1st exhaust pipe 7 2nd exhaust pipe 8 Interface 41 Center housing 42 Turbine housing 43 Compressor housing 45 Turbine wheel 46 Compressor wheel

Claims (6)

A first exhaust pipe for guiding exhaust gas discharged from a turbocharger turbine to an exhaust purification catalyst device;
An exhaust structure of an exhaust system, comprising: a second exhaust pipe that guides exhaust gas discharged from an internal combustion engine to the exhaust purification catalyst device by bypassing a turbine of the supercharger.   2. The exhaust structure of the exhaust system according to claim 1, wherein the second exhaust pipe is attached so as to guide the exhaust gas to a substantially center of the exhaust purification catalyst device.   3. The exhaust structure of an exhaust system according to claim 1, wherein the second exhaust pipe guides the exhaust gas to the substantial center of the exhaust purification catalyst device through the first exhaust pipe.   The center of the joint port between the first exhaust pipe and the exhaust purification catalyst device is aligned with the center of the joint port between the second exhaust pipe and the exhaust purification catalyst device. Exhaust structure of the exhaust system.   5. The exhaust system according to claim 3, wherein ends of the first exhaust pipe and the second exhaust pipe on the exhaust purification catalyst device side are aligned with a joint surface with the exhaust purification catalyst device. Exhaust structure. The exhaust structure of the exhaust system according to claim 1, wherein the second exhaust pipe is cut at a joint surface with the first exhaust pipe.

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