JP4930404B2 - Exhaust device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a support structure of a valve element 52 with respect to an arm 55 so as to improve reliability and stability. <P>SOLUTION: The exhaust device for the internal combustion engine is provided with the valve element 52 for opening and closing an upstream side main passage connected to respective cylinders so that exhaust delivered from the respective cylinders flows into a bypass passage having a bypass catalyst converter, and a flow passage switching valve 4 for shutting off communication between the upstream side main passages during closing. In the flow passage switching valve 4, a supporting pin 22 erected from the valve element 52 is supported on an end of the arm 55 extending radially from a rotating shaft 53. The supporting pin 22 is in an almost rod shape, and includes a neck part 24 of which diameter is partially reduced with respect to a general part 23. The arm 55 includes two split bodies 26 and 27 fastening the neck part in an assembly state. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an exhaust device for an internal combustion engine that performs exhaust gas purification using a catalytic converter, and more particularly, to an improvement of the flow path switching valve.

  As conventionally known, in a configuration in which the main catalytic converter is disposed relatively downstream of the exhaust system such as under the floor of a vehicle, the temperature of the catalytic converter rises and is activated after a cold start of the internal combustion engine. In the meantime, a sufficient exhaust purification action cannot be expected. On the other hand, the closer the catalytic converter is to the upstream side of the exhaust system, that is, the internal combustion engine side, the lower the durability due to thermal degradation of the catalyst.

Therefore, as disclosed in Patent Document 1, a bypass flow path is provided in parallel with the upstream portion of the main flow path including the main catalytic converter, and another bypass catalytic converter is interposed in the bypass flow path. However, an exhaust device has been conventionally proposed in which exhaust gas is guided to the bypass flow path side immediately after the cold start by a switching valve for switching between the two. In this configuration, the bypass catalytic converter is positioned relatively upstream of the main catalytic converter in the exhaust system and is activated relatively early, so that exhaust purification can be started from an earlier stage. it can.
JP-A-5-321644

  For example, as shown in the reference example of FIG. 5, such a flow path switching valve has a rod-like support pin 104 erected from the valve body 103 at the distal end portion of the arm 102 extending in the radial direction from the rotating shaft 101. It is fixed and supported using a nut 106 provided with a washer 105 in a state in which the tip end portion thereof is penetrated. The rotary shaft 101 is fitted into a cylindrical shaft support portion 107 of the arm 102, and the rotary shaft 101 and the arm 102 are fixed by welding at a portion of a welding window 108 drilled in the shaft support portion 107. The

  However, the flow path switching valve is exposed to high-temperature and high-pressure exhaust gas including the above-mentioned fixed portion, and in the direction along the axial direction of the support pin when opening and closing the valve body, that is, in the direction separating the valve body and the arm. Since a large load repeatedly acts, even if the nut is fixed using the nut as in the above-mentioned reference example, or even if the support pin and the arm of the valve body are fixed by welding, the nut may fall off or be welded off. It was very difficult to stably support and fix the valve body to the arm.

  An exhaust system for an internal combustion engine according to the present invention includes an upstream main passage for each cylinder connected to each cylinder, a downstream main passage formed by joining the upstream main passages of a plurality of cylinders, and the downstream main passage. A main catalytic converter interposed in a passage or a flow path downstream thereof, a bypass passage branched from the upstream main passage and provided with a bypass catalytic converter, and exhaust exhausted from each cylinder is bypassed by the bypass A valve body that opens and closes the upstream main passage so as to flow to the passage is provided, and a flow path switching valve that blocks communication between the upstream main passages when closed. In the flow path switching valve, a support pin rising from the valve body is supported at the tip of an arm extending in the radial direction from the rotating shaft. In the present invention, the support pin has a substantially rod-like shape having a neck part that is partially reduced in diameter relative to the general part, and the arm is constituted by a plurality of divided bodies that sandwich the neck part in an assembled state. ing.

  Since the valve body is supported by the arm by sandwiching the neck portion of the support pin of the valve body by the divided body of the arm, there is no risk of the nut dropping or welding peeling as described above. Since there is no need to provide a fixed part such as a nut or welding in the axial direction of the pin, even if a large load repeatedly acts in the axial direction of the support pin, which is the opening and closing direction of the valve body, due to high-temperature and high-pressure exhaust gas The body can be stably supported by the arm, and the reliability and durability can be greatly improved.

  Hereinafter, an example in which the present invention is applied as an exhaust device of an in-line four-cylinder internal combustion engine will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory view schematically showing the piping layout of the exhaust device. First, the configuration of the entire exhaust device will be described with reference to FIG.

  An upstream main passage 2 is connected to each cylinder 1 including # 1 cylinder to # 4 cylinder arranged in series. Among the four cylinders, the upstream main passage 2 of the # 1 cylinder and the upstream main passage 2 of the # 4 cylinder where the exhaust stroke is not continuous merge as one intermediate main passage 3, and the exhaust stroke is similarly performed. The upstream main passage 2 of the # 2 cylinder and the upstream main passage 2 of the # 3 cylinder are joined together as one intermediate main passage 3. Here, the flow path switching valve 4 is provided in the junction where the two upstream main passages 2 join each other. The switching valve 4 is closed when it is cold. When the switching valve 4 is closed, the upper and lower communication between the upstream main passage 2 and the intermediate main passage 3 is blocked and the two upstream main passages 2 are connected. It is the structure which makes a communication state non-communication between. In particular, as will be described later, the flow path switching valve 4 is configured such that the pair of valve bodies are seated from the upstream side on the seating portion at the periphery of the valve opening, and therefore the vertical pressure difference due to the exhaust flow is received in the closing direction. It has become. The pair of flow path switching valves 4 are configured as one valve unit 5. The two intermediate main passages 3 positioned downstream of the valve unit 5 merge with each other at a junction 6 to form one downstream main passage 7. A main catalytic converter 8 serving as a second catalytic converter is interposed in the middle of the downstream main passage 7. The catalyst in the main catalytic converter 8 includes a three-way catalyst and an HC trap catalyst. The main catalytic converter 8 has a large capacity arranged under the floor of the vehicle. The upstream main passage 2, the intermediate main passage 3, the downstream main passage 7, and the main catalytic converter 8 constitute a main passage through which exhaust flows during normal operation. This main flow path has a piping layout that is gathered in the well-known “4-2-1” form in an in-line four-cylinder internal combustion engine, and therefore, an improvement in charging efficiency utilizing the exhaust dynamic effect is realized.

  On the other hand, an upstream bypass passage 11 is branched from each of the upstream main passages 2 as bypass passages. The upstream bypass passage 11 has a sufficiently smaller passage cross-sectional area than the upstream main passage 2, and the branch point 12 serving as the upstream end of the upstream bypass passage 11 is set at a position as upstream as possible in the upstream main passage 2. Has been. The upstream bypass passage 11 of the # 1 cylinder and the upstream bypass passage 11 of the # 2 cylinder, which are adjacent to each other, merge with each other as a single intermediate bypass passage 14 at the merge point 13. The upstream bypass passage 11 of the # 3 cylinder and the upstream bypass passage 11 of the # 4 cylinder which are adjacent to each other join each other as a single intermediate bypass passage 14 at the junction 13. In FIG. 1 schematically showing each passage, each upstream bypass passage 11 is drawn relatively long, but in practice it is as short as possible. In other words, it merges as the intermediate bypass passage 14 with the shortest distance. The two intermediate bypass passages 14 join each other as one downstream bypass passage 16 at the junction 15. The downstream end of the downstream bypass passage 16 joins the downstream main passage 7 at a junction 17 upstream of the main catalytic converter 8 in the downstream main passage 7. In the middle of the downstream bypass passage 16, a bypass catalytic converter 18 using a three-way catalyst is interposed. The bypass catalytic converter 18 is disposed as upstream as possible in the bypass flow path. That is, the intermediate bypass passage 14 is as short as possible.

  In the above example, in order to shorten the passage length of the entire bypass passage (the sum of the bypass passages of each cylinder) and reduce the heat capacity of the pipe itself and the heat radiation area for the outside air, four upstream bypass passages are provided. 11 are combined into two intermediate bypass passages 14 on the upstream side without being routed for a long time, but such a configuration is arbitrary, for example, when the bypass catalytic converter 18 is biased to one side of the cylinder row For example, the entire passage length can be shortened by connecting the upstream bypass passages of the remaining cylinders at substantially right angles to the upstream bypass passage extending linearly from the other end cylinder.

  The bypass catalytic converter 18 includes two monolith catalyst carriers, that is, a first catalyst 18a and a second catalyst 18b, which are divided in the front and rear directions. One end of the exhaust gas recirculation passage 20 is connected to the gap 19 between the first catalyst 18a and the second catalyst 18b. The other end of the exhaust gas recirculation passage 20 extends to the engine intake system via an exhaust gas recirculation control valve (not shown). That is, the gap 19 serves as a recirculation exhaust outlet. The bypass catalytic converter 18 has a small capacity as compared with the main catalytic converter 8, and a catalyst excellent in low temperature activity is desirably used. In particular, in the present invention, a catalyst carrier having a relatively large pressure loss is selected so that the ventilation resistance is increased to some extent.

  In the exhaust system configured as described above, at the stage where the engine temperature or the exhaust temperature after the cold start is low, the flow path switching valve 4 is closed via an appropriate actuator, and the main flow path is shut off. Therefore, the entire amount of exhaust discharged from each cylinder 1 flows from the branch point 12 to the bypass catalytic converter 18 through the upstream bypass passage 11 and the intermediate bypass passage 14. Since the bypass catalytic converter 18 is located upstream of the exhaust system, that is, close to the cylinder 1 and is small in size, the bypass catalytic converter 18 is activated quickly and exhaust purification is started at an early stage. At this time, the flow path switching valve 4 is closed, so that the upstream main passages 2 of the cylinders 1 are not in communication with each other. Therefore, a phenomenon in which the exhaust discharged from a certain cylinder wraps around the upstream main passage 2 of the other cylinder is prevented, and a decrease in the exhaust gas temperature due to this wraparound is surely avoided.

  On the other hand, when the engine warm-up proceeds and the engine temperature or the exhaust temperature becomes sufficiently high, the flow path switching valve 4 is opened. As a result, the exhaust discharged from each cylinder 1 mainly passes from the upstream main passage 2 through the intermediate main passage 3 and the downstream main passage 7 and through the main catalytic converter 8. At this time, the bypass flow path side is not particularly blocked, but the bypass flow path side has a smaller passage cross-sectional area than the main flow path side, and the bypass catalytic converter 18 is interposed. Most of the exhaust flow passes through the main flow path side and hardly flows into the bypass flow path side. Therefore, the thermal deterioration of the bypass catalytic converter 18 is sufficiently suppressed. In addition, since the bypass flow path side is not completely cut off, a part of the exhaust flow flows through the bypass flow path side at a high speed and high load where the exhaust flow rate becomes large, so that a reduction in charging efficiency due to back pressure can be avoided.

  Further, as described above, the main flow path side has a “4-2-1” piping layout in consideration of avoidance of exhaust interference, so that it is possible to obtain an effect of improving the filling efficiency by the exhaust dynamic effect. Here, the bypass channel side communicates and aggregates in a manner that does not particularly consider exhaust interference avoidance, but by making the cross-sectional area of the upstream bypass passage 11 sufficiently small, exhaust by communication of each cylinder is achieved. Interference can be reduced to a level that is substantially negligible.

  Next, a schematic configuration of the flow path switching valve 4 will be described with reference to FIGS. 2 and 3. 2 to 4 schematically show the schematic configuration of the flow path switching valve 4, and a specific structure will be described later with reference to FIG. FIG. 2 shows the overall configuration of the valve unit 5, and FIG. 3 shows the cross-sectional shape of one of the flow path switching valves 4. As shown in the figure, a valve opening 51 is provided for each cylinder, and a disk-like valve body 52 is opened and closed from the upstream side. That is, at the end of the upstream main passage 2 of each cylinder, a seating portion 54 is formed in an annular shape over the entire circumference of the pipe constituting the upstream main passage 2, and the inner periphery thereof is the valve opening. 51. The seating surface 54 a of the seating portion 54 forms a tapered surface with which the outer peripheral edge of the valve body 52 is in contact. The valve body 52 is attached to the tip of an arm 55 that swings together with the rotary shaft 53, and the outer peripheral edge thereof has a tapered shape corresponding to the seating surface 54a. In addition, as shown in FIG. 3, the recessed part 56 for accommodating the valve body 52 in an open position is formed in the side wall 2A of the upstream main channel | path 2. As shown in FIG.

  As shown in FIG. 2, the rotation shaft 53 is common to two cylinders, and two valve bodies 52 are attached to one rotation shaft 53. Therefore, the entire valve unit 5 includes two rotating shafts 53. The two rotating shafts 53 are interlocked with each other via an interlocking mechanism (not shown) such as an appropriate link mechanism, and are simultaneously opened and closed symmetrically by a single actuator (not shown). That is, the four valve bodies 52 open and close all at once.

  Here, when the main flow path is closed, the valve body 52 is seated from the upstream side to the downstream side with respect to the tapered seating surface 54a. When the valve body 52 closes the main flow path in this way, a pressure difference is generated above and below the valve body 52 due to the exhaust flow, and the valve body 52 is further pressed against the seating surface 54a by this vertical pressure difference. That is, as shown in the explanatory diagram of FIG. 4, the bypass cross-sectional area is small on the bypass flow path side, and the pressure loss of the bypass catalytic converter 18 is added, so that the ventilation resistance of the bypass flow path becomes relatively large. The pressure P1 on the upstream side greatly increases compared to the pressure P2 on the downstream side of the valve body 52, and the valve body 52 is urged in the closing direction to press against the seating surface 54a. Therefore, combined with the close contact between the tapered surfaces, a good sealing property can be obtained. Even if the exhaust pulsation of each cylinder acts on the valve body 52 from the upstream side, the valve body 52 does not open. In particular, the bypass catalytic converter 18 reduces the amplitude of the pulsation of the downstream pressure P2, and the valve bodies 52 of two cylinders having different pulsation phases are connected to the common rotating shaft 53. The difference reliably prevents opening and closing due to pulsation. Therefore, when the flow path switching valve 4 is closed immediately after a cold start or the like, leakage on the main flow path side is prevented, and the entire amount of exhaust gas is reliably guided to the bypass flow path side. Thereby, the early temperature rise of the bypass catalytic converter 18 becomes more reliable.

  FIGS. 6A and 6B show the flow path switching valve 4 according to the first embodiment of the present invention, in which FIG. 6A is an assembly explanatory diagram, and FIG. 6B is a cross-sectional view after assembly. As shown in the figure, the arm 55 is separate from the rotary shaft 53, has a cylindrical shaft support portion 21 with which the rotary shaft 53 is fitted, and extends radially from the shaft support portion 21. It extends in a plate shape. A support pin 22 formed integrally with the valve body 52 is supported at the tip of the arm 55. The support pin 22 stands substantially perpendicularly along the axial direction of the valve body 52 from the center of the back surface of the valve body 52, and is part of the intermediate portion in the axial direction with respect to the columnar general portion 23. It has a substantially rod shape with a neck portion with a reduced diameter. That is, the support pin 22 has a shape in which the neck 24 is partially constricted, and is provided with a tapered portion 25 having an inclined surface that gradually decreases in diameter from the general portion 23 toward the neck 24.

  The arm 55 includes two first divided bodies 26 and a second divided body 27 that sandwich the neck 24 in the assembled state. The first divided body 26 has a substantially straight plate shape, and the second divided body 27 has a substantially U shape in which a slit 28 into which the first divided body 26 is fitted is formed. A portion of a pin hole 29 having a substantially circular cross section that sandwiches the neck portion 24 is formed in a half shape at the distal end portion of the first divided body 26 and the root portion of the slit 28 of the second divided body 27 facing the first divided body 26. Is formed. The pin hole 29 is provided with a small-diameter portion 30 and an inclined surface portion 31 corresponding to the neck portion 24 and the taper portion 25 of the support pin 22, and with the neck portion 24 and the taper portion 25 of the support pin 22 corresponding in the assembled state. The diameter is set equal to or slightly larger than the general portion 23 of the support pin 22. At the time of assembly, the valve body 52 can be easily assembled to the arm 55 by inserting the first divided body 26 into the slit 28 of the second divided body 27 through the neck portion 24 of the support pin 22.

  FIG. 7 shows a first example of the fixing structure of the arm 55 and the rotating shaft 53 shown in FIG. 6, and (B) is a sectional view taken along line BB in (A). The arm 55 and the rotating shaft 53 are double-fixed by first fixing means by welding and second fixing means using the fixing ring 33. Specifically, a substantially rectangular welding window 32 facing the rotation shaft 53 is formed on the cylindrical shaft support portion 21 of the arm 55 to which the rotation shaft 53 is fitted, from the first divided body 26 to the second divided body. 27, the peripheral edge of the welding window 32 and the outer periphery of the arm 55 are fixed by welding. In addition, the pair of fixing rings 33 are substantially C-shaped C-rings, and the pair of radial protrusions 34 projecting radially inward are fitted in the positioning grooves 35 of the rotation shaft 53. It is assembled to the outer periphery and rotates integrally with the rotating shaft 53. The fixing ring 33 holds both side surfaces of the arm 55 in a state in which the axial projection 36 protruding in the axial direction is fitted in the positioning recess 37 provided in the side surface of the arm 55. 33, the arm 55 is fixed so as to rotate integrally with the rotary shaft 53.

  FIG. 8 shows a second example of the fixing structure of the arm 55 and the rotating shaft 53 shown in FIG. 6, and (B) and (C) are the BB line and CC line of (A), respectively. FIG. In this example, instead of fixing by welding in FIG. 7 as the first fixing means, the divided body 26 is more simply provided so that the opposed surfaces 38 that face each other in the rotation direction of the rotary shaft 53 are provided. , 27 are set. Specifically, a wide portion 39 that is partially wide is set at an end portion near the shaft support portion 21 in the slits 28 of the first divided body 26 and the second divided body 27. As a result, the step surface between the wide portion 39 and the other narrow portion 40 is formed as an opposing surface 38 that faces each other in the rotational direction of the rotary shaft 53. In this way, the two divided bodies 26 and 27 face each other in the direction of rotation of the rotary shaft 53 on the facing surface 38, so that the relative rotation of the two divided bodies 26 and 27 is restricted, and the two 26 and 27 are integrally formed. It is configured to rotate. The fixing structure by the fixing ring 33 as the second fixing means is the same as the example of FIG.

  FIG. 9 shows a flow path switching valve 4 according to a second embodiment of the present invention. In the second embodiment, the arm 55 includes two first divided bodies 41 and a second divided body 42 that are divided into two in the axial direction of the rotation shaft. A part of the pin hole 29 having a substantially circular cross section that sandwiches 24 is recessed in a halved shape. Similar to the first embodiment shown in FIG. 6, the pin hole 29 is provided with a small diameter portion 30 and an inclined surface portion 31 corresponding to the neck portion 24 and the tapered portion 25 of the support pin 22, and corresponds in an assembled state. The diameter is set to be equal to or slightly larger than the neck portion 24 and the tapered portion 25 of the support pin 22 and smaller than the general portion 23 of the support pin 22 (see FIG. 6).

  FIG. 10 shows an example of a fixing structure of the arm 55 and the rotating shaft 53 of FIG. In this example, the arm 55 and the rotating shaft 53 are doubly fixed by the first fixing means by welding and the second fixing means using the temporary fixing pins 44. Specifically, in the first fixing means by welding, as in the example of FIG. 7 described above, the welding window 32 facing the rotating shaft 53 is formed on the shaft support portion 21 of the arm 55 to which the rotating shaft 53 is fitted. A hole is formed from the first divided body 26 to the second divided body 27, and the periphery of the welding window 32 and the outer periphery of the arm 55 are fixed by welding.

  The temporary fixing pin 44 projects integrally from the outer periphery of the arm 55 outward in the radial direction through the welding window 32. Therefore, even if the fixation by welding is released due to welding peeling or the like, the arm 55 is supported by the rotating shaft 53 without dropping by the temporary fixing pin 44 abutting and engaging with the peripheral edge of the welding window 32. The That is, the movable range of the temporary fixing pin 44 is restricted within the circumferential direction range 32A of the welding window 32, and the rotary shaft 53 and the arm 55 are temporarily fixed in a state in which they can be relatively rotated by the minute section 32A.

  Referring to FIG. 11, the rotating shaft 53 is disposed in the vicinity of the side wall 2 </ b> A of the upstream main passage 2, and as shown in FIG. The body 52 is retracted along the side wall 2A of the upstream main passage 2 and is accommodated in a recess 56 that is recessed outward from the side wall 2A of the upstream main passage 2 so as not to hinder the flow of exhaust. . On the other hand, when the fixing by welding is released and the temporary fixing state by the temporary fixing pin 44 is established, the temporary fixing pin 44 can be relatively rotated within the circumferential range of the welding window 32 as shown in FIG. In the state where there is a predetermined play, the arm 55 is temporarily fixed without falling off from the rotating shaft 53, and compared with the retracted posture in the fixed state by welding, the relative rotation of the arm 55 with respect to the rotating shaft 53 is in a fully opened state. The rotation angle in the fully open direction of the valve body 52 is insufficient, and the valve body 52 protrudes obliquely from the recess 56 toward the upstream main passage 2 side. For this reason, since the flow of exhaust gas is slightly hindered, the back pressure on the upstream side of the valve body is increased as compared with the fixed state by welding. It should be noted that the amount of protrusion of the valve body 52 toward the upstream main passage 2 is slight, and is set so that the flow of exhaust gas is not significantly hindered to adversely affect operability.

  Accordingly, whether the back pressure ΔP on the upstream side of the valve body 52 is detected or estimated, and based on the back pressure ΔP in the fully open state of the valve body 52, is the temporarily fixed state by the temporary fixing pin 44 (second fixing means)? Can be determined. Specifically, as shown in FIG. 12, when the back pressure ΔP is higher than a reference value corresponding to a fixed state by welding (first fixing means), the welding is unfixed due to welding peeling or the like. Thus, it can be determined that the temporary fixing pin 44 (second fixing means) is in a temporarily fixed state. When it is determined that the vehicle is temporarily fixed, inspection / repair can be promoted by notifying the driver that the vehicle has been fixed by a warning light or a warning sound. The back pressure ΔP may be detected directly using, for example, a pressure sensor, or may be more simply estimated from the engine operating state such as the exhaust temperature.

  13 and 14 show another example of the fixing means. In the example of FIG. 13, as the second fixing means, the inner peripheral surface 21 </ b> A of the shaft support portion 21 of the arm 55 and the outer peripheral surface 53 </ b> A of the rotating shaft 53 facing this are formed in a similar polygonal shape. Yes. A predetermined gap (play) 45 is secured between the inner peripheral surface 21A of the shaft support portion 21 and the outer peripheral surface 53A of the rotating shaft 53, whereby the rotating shaft 53 and the arm 55 are fixed to each other. Are temporarily fixed in a state where relative rotation is possible only in the minute section. In the example of FIG. 14, the arm 55 is formed in a plate shape without a shaft support portion, and an arm slit 46 formed through the rotation shaft 53 in the radial direction through the end portion on the rotation shaft side of the arm 55. As shown by reference numeral 47, the protruding end is fixed to the rotating shaft 53 by welding (first fixing means). In addition, a predetermined gap (play) 48 is secured between the arm slit 46 and the rotary shaft 53 penetrating the slit 46, so that the rotary shaft 53 and the arm 55 are relative to each other by a predetermined minute interval. Temporarily fixed in a rotatable state (second fixing means).

  15 to 19 are a plan view (A) and a front view (B) showing still other examples of the fixing means, respectively. As shown in FIGS. 15 to 18, a concave and convex stepped portion 43 </ b> A that fits with each other is set on the mating surface portion 43 so that the divided bodies 41 and 42 rotate integrally. In addition, also in what is shown in FIGS. 6-13 mentioned above, you may make it provide such a level | step-difference part 43A in a mating surface part.

  In the example of FIG. 15, as first fixing means, both side edges of the divided bodies 41 and 42 of the arm 55 through which the rotating shaft 53 is inserted and the outer periphery of the rotating shaft 53 are fixed by welding as indicated by reference numeral 49. And as the 2nd fixing means, as shown to the code | symbol 50, the front-end | tips of the division bodies 41 and 42 of the arm 55 are being fixed by welding. In the example of FIG. 16, the above-described fixing ring 33 is used as the first fixing means (see FIGS. 7 and 8). In the example of FIG. 17, welding is performed by the above-described welding window 32 as the first fixing means (see FIG. 5 and the like). In the example of FIG. 18, the welding window 32 </ b> B is set in a vertically long shape that extends to the vicinity of the support pin 22 along the mating surface portion 43 of the divided body in order to increase the fixing force of the divided bodies 41 and 42. In the example of FIG. 18, in addition to the welding window 32 </ b> B of FIG. 17, an auxiliary welding window 32 </ b> C is further formed along the mating surface portion 43 on the tip side of the support pin 22.

  As described above, the present invention has been described based on specific embodiments. However, the present invention is not limited to the above-described illustrated embodiments, and includes various modifications and changes without departing from the spirit of the present invention. It is a waste. For example, although an example in which the present invention is applied to an in-line four-cylinder internal combustion engine has been described, the present invention is applied as an exhaust device for various types of internal-combustion engines such as an in-line multi-cylinder internal combustion engine other than an in-line four-cylinder engine or a V-type multi-cylinder internal combustion engine. Is possible.

  The characteristic technical ideas that can be grasped from the above description are listed below.

  (1) An upstream main passage 2 for each cylinder connected to each of the cylinders # 1 to # 4, a downstream main passage 7 formed by joining the upstream main passages 2 of a plurality of cylinders, and the downstream main passage A main catalytic converter 8 interposed in the passage 7 or a flow path downstream thereof, bypass passages 11, 14, 16 branched from the upstream main passage 2 and provided with a bypass catalytic converter 18; A valve body 52 that opens and closes the upstream main passage 2 is provided so that the exhaust discharged from the cylinder flows to the bypass passages 11, 14, and 16, and the flow that shuts off the communication between the upstream main passages 2 when closed. A path switching valve 4.

  In this exhaust system, at least the upstream side portions of the bypass passages 11, 14, 16 are the same number of passages as the number of cylinders, and are upstream of the main flow path, that is, the junction 13 of the upstream main path 2. At the position, the main branch 2 branches from the upstream main passage 2. Therefore, the bypass catalytic converter 18 can be arranged on the upstream side without being restricted by the position of the junction 13 of the main flow path. Further, since the point 12 branching to the bypass flow path side is a position close to each cylinder, the exhaust gas flows into the bypass flow path side relatively without being cooled by the heat capacity of the main flow path immediately after the cold start.

  That is, immediately after the cold start or the like, the flow path switching valve 4 is closed, and the upstream main passage 2 and the downstream main passage 7 are shut off. Thereby, the exhaust discharged from each cylinder flows through the bypass passage provided with the bypass catalytic converter 18. At the same time, the flow path switching valve 4 individually closes the valve openings 51 of the plurality of upstream main passages 2, so that the mutual communication of the upstream main passages 2 of the respective cylinders is blocked. If the upstream main passages 2 are in communication with each other when the flow path switching valve 4 is in the closed state, the exhaust strokes sequentially arrive at each cylinder, and therefore, from the upstream main passage 2 of one cylinder to the other A phenomenon occurs in which the exhaust gas flows into the upstream main passage 2 of the cylinder. Therefore, heat easily escapes to the outside, and the temperature rise of the bypass catalytic converter 18 is hindered. By causing the upstream main passages 2 to be out of communication with each other when the flow path switching valve 4 is closed, this wraparound phenomenon can be avoided.

  As shown in FIGS. 6 to 11 and the like, in the flow path switching valve 4, the support pin 22 rising from the valve body 52 is supported at the tip of an arm 55 that extends in the radial direction from the rotation shaft 53. The support pin 22 has a substantially rod shape having a neck portion 24 partially reduced in diameter relative to the general portion 23, and the arm 55 has a plurality of divided bodies 26 and 27 (41) that sandwich the neck portion 24 in an assembled state. , 42).

  As described above, since the valve body 52 can be supported by the arm 55 by sandwiching the neck portion 24 between the divided bodies 26 and 27 (41 and 42) of the arm 55, Compared to fixing the arm using a nut or fixing by welding, the number of work steps is small and the manufacturing cost can be greatly reduced. Further, since the general portion 23 on the tip side of the neck portion 24 which is a part of the support pin 22 functions as a nut, a large load is repeatedly applied along the axial direction of the support pin 22 when the valve body 52 is opened and closed. However, unlike the above-described reference example, there is no possibility that a separate nut will come off or the valve body will drop off due to welding peeling, and the valve body 52 can be stably supported by the arm 55. Durability is significantly improved.

  (2) The support pin 22 is provided with a taper portion 25 that gradually decreases in diameter from the general portion 23 toward the neck portion 24. The pin hole 29 of the arm 55 through which the support pin 22 penetrates is provided with a small diameter portion 30 and an inclined surface portion 31 corresponding to the neck portion 24 and the taper portion 25 of the support pin 22. By providing such a tapered portion 25, stress concentration due to corners (edges) is alleviated, and a slight swinging operation of the valve body 52 with respect to the arm 55, a so-called swinging operation is allowed. For this reason, the valve body 52 can be satisfactorily brought into close contact with the valve opening 51 regardless of assembly errors or dimensional variations, and the sealing performance is improved.

  (3) For example, as shown in the first embodiment shown in FIG. 6 or the like, the arm 55 has a simple structure constituted by a minimum of two divided bodies. In other words, the first divided body 26 having a linear shape and the second divided body 27 in which a slit 28 into which the first divided body 26 is fitted are formed. A part of the pin hole 29 that sandwiches the neck portion 24 is formed in a halved shape at the distal end portion of the first divided body 26 and the base portion of the slit 28 facing the first divided body 26. According to this configuration, the valve body 52 can be easily assembled to the arm 55 by inserting the first divided body 26 into the slit 28 of the second divided body 27 with the neck 24 interposed therebetween, and the first divided body Since the body 26 is fitted in the slit 28 of the second divided body 27, the both 26 and 27 do not move in the axial direction of the rotating shaft 53, and both the 26 and 27 are connected using welding or a fixture. There is no need to restrict the movement in the axial direction.

  As shown in (4) or the second embodiment shown in FIG. 9 and the like, the arm 55 is composed of two divided bodies 41 and 42 that are divided into two in the axial direction of the rotating shaft 53. A part of the pin hole 29 that sandwiches the neck portion 24 is formed in the mating surface portion 43 so as to be halved. Even in this configuration, the arm 55 can be configured by a minimum of two members.

  (5) The rotating shaft 53 and the arm 55 are separated from each other due to the attachment of the plurality of arms 55 to the rotating shaft 53, assembling and manufacturability requirements. The first fixing means for fixing the rotating shaft 53 and the arm 55, and the second fixing means for fixing the rotating shaft 53 and the arm 55 separately from the first fixing means. It has a fixed structure. For this reason, even if the fixing by the first fixing means is released, the fixed state can be maintained by the second fixing means, and the reliability is excellent.

  (6) In the fixed state by the first fixing means, as shown in FIG. 11 (A), the rotary shaft is set so that the valve body 52 in the fully opened state assumes a retracted posture along the side wall 2A of the upstream main passage 2. 53 is disposed in the vicinity of the side wall 2A of the upstream main passage 2, and the second fixing means is configured such that when the fixing by the first fixing means is released, the rotating shaft 53 and the arm 55 are in a very small section. The rotating shaft 53 and the arm 55 are temporarily fixed in a state where only the relative rotation is possible. In this case, when the fixing by the first fixing means is disengaged for some reason and the temporary fixing state by the second fixing means is reached, the valve body 52 in the fully opened state is relatively compared to the fixing state by the first fixing means. As shown in FIG. 12B, the back pressure ΔP on the upstream side of the valve body 52 rises as shown in FIG. 12 (B). Therefore, based on the back pressure ΔP on the upstream side of the valve body, it is possible to easily determine whether or not the temporarily fixed state by the second fixing means. In the temporarily fixed state, it is possible to notify the driver that the fixing by the first fixing means has been released, for example, by a warning light or a warning sound, and to prompt inspection and repair.

  (7) As shown in FIG. 10, for example, the first fixing means includes a peripheral portion of the welding window 32 formed in the shaft support portion 21 of the arm 55 with which the rotary shaft 53 is fitted, and the welding window 32. The second fixing means includes a temporary fixing pin 44 extending in the radial direction from the outer peripheral surface of the rotating shaft 53 through the welding window 32. It is. According to this configuration, when fixing by welding, which is the first fixing means, is disengaged, the arm 55 is temporarily fixed to the rotary shaft 53 in a range in which the temporary fixing pin 44 can move in the circumferential range 32A of the welding window 32. Is done. As described above, the second fixing means can be realized with a simple configuration in which the temporary fixing pin 44 is erected on the rotating shaft 53 by using the welding window 32 used in the first fixing means.

The structure explanatory view showing an example of the exhaust device concerning the present invention. The top view which shows the structure of the whole valve unit. Sectional drawing which shows the flow-path switching valve of one cylinder. Explanatory drawing of the up-and-down pressure difference added to a valve body. The top view (A) and sectional drawing (B) which show the reference example of a flow-path switching valve. Assembly explanatory drawing (A) and sectional drawing (B) which show the fixing structure of the support pin of the flow-path switching valve concerning 1st Example of this invention. The top view (A) and sectional drawing (B) which show an example of the fixed structure of the rotating shaft and arm of the flow-path switching valve of FIG. The top view (A) and sectional drawing (B), (C) which show the other example of the fixed structure of the rotating shaft and arm of a flow-path switching valve. Assembly explanatory drawing which shows the fixing structure of the support pin of the flow-path switching valve concerning 2nd Example of this invention. The top view (A) and sectional drawing (B) which show an example of the fixed structure of the rotating shaft and arm of the flow-path switching valve of FIG. Explanatory drawing which shows the retracted position in the fully open state in the fixed state (A) by welding, and the temporary fixed state (B) by a temporary fixing pin. The characteristic view which shows the change of the back pressure upstream of a valve body according to a fixed state and a temporary fixed state. The top view (A) and sectional drawing (B) which show the other example of the fixed structure of the rotating shaft and arm of a flow-path switching valve. The top view (A) and sectional drawing (B) which show another example of the fixed structure of the rotating shaft and arm of a flow-path switching valve. The top view (A) and front view which show the further another example of the fixed structure of the rotating shaft and arm of a flow-path switching valve. The top view (A) and front view which show the further another example of the fixed structure of the rotating shaft and arm of a flow-path switching valve. The top view (A) and front view which show the further another example of the fixed structure of the rotating shaft and arm of a flow-path switching valve. The top view (A) and front view which show the further another example of the fixed structure of the rotating shaft and arm of a flow-path switching valve. The top view which shows the further another example of the fixed structure of the rotating shaft and arm of a flow-path switching valve.

Explanation of symbols

2 ... Upstream main passage 3 ... Intermediate main passage 4 ... Flow path switching valve 7 ... Downstream main passage 8 ... Main catalytic converter 11 ... Upstream bypass passage 14 ... Intermediate bypass passage 16 ... Downstream bypass passage 18 ... Bypass catalytic converter DESCRIPTION OF SYMBOLS 21 ... Shaft support part 22 ... Support pin 23 ... General part 24 ... Neck part 25 ... Tapered part 26 ... 1st division body 27 ... 2nd division body 28 ... Slit 29 ... Pin hole 32 ... Welding window (1st fixing means)
33. Fixing ring (second fixing means)
DESCRIPTION OF SYMBOLS 41 ... 1st division body 42 ... 2nd division body 43 ... Matching surface part 44 ... Temporary fixing pin 52 ... Valve body 53 ... Rotating shaft 55 ... Arm

Claims (7)

An upstream main passage for each cylinder connected to each cylinder;
A downstream main passage formed by joining upstream main passages of a plurality of cylinders;
A main catalytic converter interposed in the downstream main passage or a downstream passage, and
A bypass passage branched from the upstream main passage and having a bypass catalytic converter interposed therebetween;
A valve switching element that opens and closes the upstream main passage so that the exhaust discharged from each cylinder flows to the bypass passage, and a flow path switching valve that shuts off communication between the upstream main passages when closed. ,
In the flow path switching valve, a support pin standing from the valve body is supported at the tip of an arm extending in the radial direction from the rotation shaft,
This support pin has a substantially rod shape having a neck portion partially reduced in diameter relative to the general portion,
The exhaust device for an internal combustion engine, wherein the arm is constituted by a plurality of divided bodies that sandwich a neck portion in an assembled state.   The exhaust device for an internal combustion engine according to claim 1, wherein the support pin is provided with a tapered portion that gradually decreases in diameter from the general portion toward the neck portion.   The arm is composed of a first divided body having a linear shape, and a second divided body in which a slit into which the first divided body is fitted, and a distal end portion of the first divided body, 3. The exhaust system for an internal combustion engine according to claim 1, wherein a part of a pin hole for sandwiching the neck portion is formed in a half shape at a base portion of a slit facing the slit portion.   The arm is composed of two divided parts that are divided into two in the axial direction of the rotating shaft, and a part of the pin hole that sandwiches the neck part is recessed in a half shape on the mating surface part of both divided parts. The exhaust system for an internal combustion engine according to claim 1 or 2, wherein the exhaust system is provided. The rotating shaft and the arm are separate bodies,
First fixing means for fixing the rotating shaft and the arm;
Separately from the first fixing means, second fixing means for fixing the rotating shaft and the arm;
The exhaust device for an internal combustion engine according to any one of claims 1 to 4, further comprising: In the fixed state by the first fixing means, the rotating shaft is disposed in the vicinity of the side wall of the upstream main passage so that the valve body in the fully opened state is in a retracted posture along the side wall of the upstream main passage. ,
The second fixing means temporarily fixes the rotating shaft and the arm in a state where the rotating shaft and the arm can be relatively rotated by a minute section when the fixing by the first fixing means is released. 6. The exhaust system for an internal combustion engine according to claim 5, wherein the exhaust system is an internal combustion engine. The first fixing means fixes, by welding, a peripheral portion of a welding window drilled in a shaft support portion of an arm to which the rotary shaft is fitted, and an outer peripheral portion of the rotary shaft facing the welding window. Is,
The exhaust device for an internal combustion engine according to claim 6, wherein the second fixing means includes a temporary fixing pin extending in a radial direction from the outer peripheral surface of the rotating shaft through the welding window.

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