JP2007092592A - Egr gas mixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize an EGR gas mixing device capable of suitably mixing a large amount of exhaust gas in intake air without causing rise of manufacturing cost. <P>SOLUTION: In the EGR gas mixing device having a venturi part 2 formed in a middle of an intake pipe 1 and provided with an annular chamber 3 on an outer circumference of the venturi part 2, having an EGR pipe taking part of exhaust gas 4 from an exhaust side and leading the same to the annular chamber 3 connected thereon, having an annular slit 6 establishing communication between an inside of the annular chamber 3 and an inside of the intake pipe 1 formed in the venturi part 2, and having the venturi part 2 divided into a upstream side shrinking part 7 and an downstream expansion part 8, an start end of the expansion part 8 is shifted in a radial direction outside in relation to an terminal end of the shrinking part 7 of the venturi part 2 to form a eight difference G. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an EGR gas mixing device.

  2. Description of the Related Art Conventionally, in an automobile engine or the like, a part of exhaust gas is extracted from the exhaust side and returned to the intake side, and combustion of fuel in the engine is suppressed by the exhaust gas returned to the intake side so that the combustion temperature is increased. So-called exhaust gas recirculation (EGR), which reduces the generation of NOx by lowering, is performed. Generally, when this type of exhaust gas recirculation is performed, an exhaust manifold is used. An appropriate position of the exhaust passage extending from the exhaust pipe to the exhaust pipe and an intake pipe near the inlet of the intake manifold are connected by an EGR pipe, and the exhaust gas is recirculated through the EGR pipe.

  However, simply connecting the EGR pipe to the side surface of the intake pipe makes it difficult to uniformly mix the exhaust gas with the intake air flowing through the intake pipe. Furthermore, there is an opening at the connection portion of the EGR pipe to the intake pipe. Due to the narrowness, there is a disadvantage that the mixing ratio of the exhaust gas to the intake air cannot be increased rapidly.

In order to improve such inconvenience, for example, the following Patent Document 1 has already been proposed. In such a Patent Document 1, a venturi portion for narrowing the flow of intake air is formed in the middle of the intake pipe, and the Venturi There has been proposed a structure in which a plurality of EGR gas inlet passages are connected so as to introduce exhaust gas from the direction transverse to the main intake air flow direction and the tangential direction of the venturi portion.
JP 2003-003910 A

  However, as shown in Patent Document 1, in the structure in which the EGR gas inlet passage is connected to the venturi portion from the tangential direction, the suction action of sucking the exhaust gas from the EGR pipe into the intake pipe by the action of the venturi portion. However, even if a plurality of EGR gas inlet passages are provided, there is a problem that it is not possible to cope with a demand for instantaneously mixing a large amount of exhaust gas into the intake air. .

  Therefore, as shown in FIGS. 2 and 3, the present inventor forms a venturi portion 2 in the middle of the intake pipe 1, and provides an annular chamber 3 on the outer periphery of the venturi portion 2. EGR pipe 5 is connected to an EGR pipe 5 that extracts and guides a part of the exhaust gas 4 from the venturi section 2, and an annular slit 6 that connects the interior of the annular chamber 3 and the interior of the intake pipe 1 is formed in the throat section of the venturi section 2 The device was invented (see Japanese Patent Application No. 2004-320348).

  Here, the annular slit 6 has an inner diameter of the venturi portion 2 due to the end of the upstream reduced diameter portion 7 and the start end of the downstream enlarged diameter portion 8 divided by the annular slit 6. Each of the reduced diameter portion 7 and the enlarged diameter portion 8 facing each other with the annular slit 6 interposed therebetween is formed on the downstream side (the enlarged diameter portion 8 side) with respect to the smallest smallest inner diameter portion position X. These end surfaces form inclined surfaces 7a and 8a whose diameter is reduced toward the downstream side (the enlarged diameter portion 8 side).

  In this way, the exhaust gas 4 guided to the annular chamber 3 by the EGR pipe 5 flows into the intake pipe 1 from the entire circumference through the annular slit 6 formed in the venturi part 2, and the exhaust gas 4 of the venturi part 2 Since the exhaust gas 4 in the annular chamber 3 is satisfactorily sucked by the negative pressure portion generated on the enlarged diameter portion 8 side, a large amount of the exhaust gas 4 is well mixed with the intake air 9 in the intake pipe 1. Can do.

  That is, as schematically shown in FIG. 4, in the venturi portion 2, the negative pressure portion A is generated downstream of the minimum inner diameter portion position X of the venturi portion 2 (the enlarged diameter portion 8 side) due to the flow of the intake air 9. Therefore, the annular slit 6 is formed on the downstream side (the enlarged diameter portion 8 side) with respect to the minimum inner diameter portion position X, and the end surfaces of the reduced diameter portion 7 and the enlarged diameter portion 8 of the venturi portion 2 are arranged on the downstream side (expanded portion). If the inclined surfaces 7a and 8a are reduced in diameter toward the radial portion 8 side, the negative pressure portion A can easily enter the inside of the annular slit 6 to increase the suction action of the exhaust gas 4, and the exhaust gas 4 This effectively improves the mixing property.

  However, although the above-described structure with good mixing properties was found after various experiments, in this type of EGR gas mixing device, the venturi portion 2 including the annular chamber 3 and the annular slit 6 is integrated by casting. Since it is generally manufactured, there is a problem that the work of post-processing the inclined surfaces 7a, 8a at the end of the reduced diameter portion 7 and the start end of the enlarged diameter portion 8 after casting is technically difficult. There was a risk that the manufacturing cost would be significantly increased because it was necessary to take measures such as giving up the integral production by casting 2 and adopting a split structure.

  The present invention has been made in view of such circumstances, and an object thereof is to realize an EGR gas mixing device that can mix a large amount of exhaust gas into intake air without causing an increase in manufacturing cost.

  The present invention forms a venturi part in the middle of the intake pipe and provides an annular chamber on the outer periphery of the venturi part, and connects an EGR pipe for extracting and guiding a part of the exhaust gas from the exhaust side to the annular chamber, An EGR gas mixing device in which an annular slit is formed in the venturi portion to communicate the inside of the annular chamber and the inside of the intake pipe, and the venturi portion is divided into an upstream reduced diameter portion and a downstream enlarged portion, A step is formed by shifting the starting end of the enlarged diameter portion radially outward with respect to the end of the reduced diameter portion of the venturi portion.

  Thus, in this way, by forming the step by shifting the starting end of the enlarged diameter portion radially outward with respect to the end of the reduced diameter portion of the venturi portion, the minimum inner diameter position of the venturi portion (reduced diameter portion) The negative pressure portion generated on the downstream side (expanded portion side) is more likely to enter the inside of the annular slit, which is different from the case where the inclined surface is post-processed on the respective end surfaces of the reduced diameter portion and the expanded diameter portion. Thus, the exhaust gas guided to the annular chamber by the EGR pipe is satisfactorily mixed with the intake air in the intake pipe from the entire circumference through the annular slit of the venturi portion.

  According to the EGR gas mixing device of the present invention, the diameter of the diameter-reduced portion and the diameter-expanded portion is increased from the initial production stage with respect to the end of the diameter-reduced portion of the venturi portion without post-processing the inclined surface. Since a high suction action can be obtained simply by shifting the starting end of the section radially outward to form a step, an EGR gas mixing device that can mix a large amount of exhaust gas into the intake air has increased production costs. An excellent effect that it can be realized without inviting can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of an embodiment for carrying out the present invention, and the same reference numerals as those in FIGS. 2 to 4 denote the same components.

  As shown in FIG. 1, in this embodiment, a venturi portion 2 is formed in the middle of the intake pipe 1 as in the case of the EGR gas mixing device previously shown in FIGS. An annular chamber 3 is provided on the outer periphery of the throat portion 2 and an EGR pipe 5 (see FIG. 2) for extracting and guiding a part of the exhaust gas 4 from the exhaust side to the annular chamber 3 is connected to the venturi. An annular slit 6 that communicates the inside of the annular chamber 3 and the inside of the intake pipe 1 is formed in the part 2, and the venturi part 2 is divided into a reduced diameter part 7 on the upstream side and an enlarged diameter part 8 on the downstream side. Instead of post-processing the inclined surfaces on the respective end surfaces of the reduced diameter portion 7 and the enlarged diameter portion 8, the starting end of the enlarged diameter portion 8 is radially outward with respect to the end of the reduced diameter portion 7 of the venturi portion 2. A structure in which a step G is formed by shifting is employed.

  Here, the venturi part 2 provided with the annular chamber 3 and the annular slit 6 is integrally manufactured by casting, and the thickness of the terminal end of the reduced diameter part 7 and the starting end of the enlarged diameter part 8 is about about the hot water flow. The radial step G between the terminal end of the reduced diameter portion 7 and the start end of the enlarged diameter portion 8 is at least reduced in diameter, about 5 mm (each root portion of the reduced diameter portion 7 and the enlarged diameter portion 8 is about 8 mm). The thickness is preferably about the thickness of the end of the portion 7, and the width W of the annular slit 6 between them is preferably at least about 10 mm.

  Thus, by forming the step G by shifting the starting end of the enlarged diameter portion 8 radially outward relative to the end of the reduced diameter portion 7 of the venturi portion 2, the minimum inner diameter portion of the venturi portion 2 is formed. The negative pressure portion generated on the downstream side (the enlarged diameter portion 8 side) from the position X (the end position of the reduced diameter portion) can easily enter the inside of the annular slit 6, and the respective end surfaces of the reduced diameter portion 7 and the enlarged diameter portion 8. The suction action is the same as when the inclined surface is post-processed, and the exhaust gas 4 guided to the annular chamber 3 by the EGR pipe 5 (refer to FIG. 2) passes through the annular slit 6 of the venturi section 2 all around. Therefore, it is well mixed with the intake air 9 in the intake pipe 1.

  Therefore, according to the above-described embodiment, the end face of the reduced diameter portion 7 of the venturi portion 2 can be compared with the end of the reduced diameter portion 7 from the initial production stage without post-processing the inclined surfaces on the end surfaces of the reduced diameter portion 7 and the enlarged diameter portion 8. Since a high suction action can be obtained simply by shifting the starting end of the enlarged diameter portion 8 radially outward to form the step G, an EGR gas mixing device that can mix a large amount of exhaust gas 4 into the intake air 9 well Can be realized without causing an increase in production cost.

  Note that the EGR gas mixing device of the present invention is not limited to the above-described embodiments, and is not limited to the preferred dimensional values used in the description of the embodiments. Of course, various changes can be made without departing from the scope of the invention.

It is sectional drawing which expands and shows the principal part of an example of embodiment which implements this invention. It is sectional drawing which shows a prior art example. It is sectional drawing which expands and shows the principal part of FIG. It is explanatory drawing which shows typically about the effect | action of a venturi part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Intake pipe 2 Venturi part 3 Annular chamber 4 Exhaust gas 5 EGR pipe 6 Annular slit 7 Reduced diameter part 8 Expanded part 9 Intake G step

Claims (1)

  A venturi is formed in the middle of the intake pipe, and an annular chamber is provided on the outer periphery of the venturi, and an EGR pipe for extracting and guiding a part of the exhaust gas from the exhaust side is connected to the annular chamber, and the venturi is connected to the venturi. An EGR gas mixing device in which an annular slit that communicates the inside of an annular chamber and the inside of an intake pipe is formed to divide the venturi part into an upstream reduced diameter part and a downstream enlarged diameter part. An EGR gas mixing apparatus characterized in that a step is formed by shifting the starting end of the enlarged diameter portion radially outward with respect to the end of the diameter portion.

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