JP2005048713A - Exhaust manifold for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust manifold capable of being properly arranged in a small space near an internal combustion engine for compatibly attaining the output performance of the internal combustion engine and the efficiency of exhaust emission control. <P>SOLUTION: The exhaust manifold comprises a first manifold unit 1 formed with first and second exhaust flow paths (branches 21, 22) as one unit connected in communication with first and second adjacent exhaust ports 11, 12, respectively, and a second manifold unit 2 formed with third and fourth exhaust flow paths (branches 23, 24) as one unit connected in communication with third and fourth adjacent exhaust ports 13, 14, respectively, in rearward order of the serial four-cylinder internal combustion engine. The lengths of the first to fourth exhaust flow paths are formed almost equal to one another and their exhaust holes are connected in communication with a single exhaust port (a connection case 3). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust manifold for an internal combustion engine, and more particularly to an exhaust manifold for an in-line four-cylinder internal combustion engine.

  The exhaust manifold collects exhaust discharged from each cylinder of the multi-cylinder internal combustion engine and guides the exhaust to an exhaust pipe, a catalytic converter, or the like. For an exhaust manifold for an inline 4-cylinder internal combustion engine, for example, As described in Patent Document 1, a distinction is made between an in-line four-cylinder single port type in which the outlets of the branches forming each exhaust passage are gathered in one place, and an in-line four-cylinder dual port type in which the exhaust ports are separated into two. . In the latter dual port type, in order to avoid exhaust interference, when the first to fourth cylinders are arranged in order from the front of the internal combustion engine, the exhaust port of the first cylinder and the exhaust port of the fourth cylinder are assembled to Generally, the exhaust port and the exhaust port of the second cylinder and the exhaust port of the third cylinder are gathered together to form the other exhaust port.

  For example, in Patent Document 1 below, in an exhaust manifold of a multi-cylinder internal combustion engine, it is specified which exhaust port of the internal combustion engine the inlet of each branch (exhaust flow path) is connected to. An exhaust manifold of an internal combustion engine is illustrated. Patent Document 1 is characterized in that a front half and a back half that are curved in a three-dimensional direction are made by pressing a sheet metal, and both halves are faced and welded to form a double exhaust pipe. ing. Further, Patent Document 4 specifies a pair of branch pipes 4-1 and 4-4; 4-2 and 4-3 respectively connected to exhaust ports of a pair of cylinders that do not overlap in the exhaust stroke, After the branch pipes 4-1 and 4-4 and the branch pipes 4-2 and 4-3 are combined into the collecting pipes 5-1 and 5-2, respectively, the whole is covered with a sheet metal case. .

  On the other hand, in Patent Document 2 below, it is contemplated that the exhaust manifold has a double-pipe structure in view of heat retention, and each branch (exhaust flow) is connected to the exhaust ports of a pair of cylinders in order from the front of the internal combustion engine. An exhaust manifold is disclosed in which the inlet of the (way) is connected. Patent Document 3 below also discloses an exhaust manifold having a double-pipe structure, which includes one or more first inner pipes, one or more second inner pipes, a lower case, an intermediate case, and an upper case. It is described that the structure is a double pipe structure and the number of parts is reduced as much as possible to reduce cost and weight. The exhaust manifold described in Patent Document 4 also has a double pipe structure as described above.

JP-A-4-265418 Japanese Patent Laid-Open No. 10-252457 JP 2000-337143 A JP 2000-27642 A “Automotive Technology Handbook”, Volume 2, Design, Japan Society for Automotive Engineers, June 15, 1992, p. 90-91

  As described in Patent Documents 1, 3 and 4 described above, in an exhaust manifold for an in-line four-cylinder internal combustion engine, a branch of the first cylinder and a branch of the fourth cylinder are assembled in order to effectively use the exhaust pulsation. At the same time, the so-called 4-2-1 type, in which the branch of the second cylinder and the branch of the third cylinder are gathered (4 → 2) and then gathered into one exhaust pipe (2 → 1), becomes the mainstream. ing. This is because, in an in-line four-cylinder internal combustion engine, the explosion strokes are performed in the order of the first cylinder, the second cylinder, the fourth cylinder, and the third cylinder. The exhaust gas of the first cylinder and the fourth cylinder, and the exhaust gas of the second cylinder and the third cylinder are gathered so as not to deteriorate the output performance of the engine. The exhaust gas gathered in this way is usually configured to be purified by a catalytic converter interposed in an exhaust pipe below the internal combustion engine.

  On the other hand, in order to meet the recent demand for improved exhaust gas purification performance, particularly early activation of the catalyst during warm-up, it is necessary to dispose the catalytic converter in the vicinity of the internal combustion engine. However, it is not easy to arrange the exhaust manifold of the 4-2-1 type as described above in a narrow space between the internal combustion engine and the catalytic converter. In particular, it is extremely difficult to bend a metal tube to form a three-dimensional branch because there are various restrictions such as restrictions on the bending (plastic deformation) of the metal. Furthermore, in order to meet the demand for improving the exhaust gas purification efficiency of the catalyst, an outer shell (outer pipe) is disposed outside the exhaust pipe from the internal combustion engine to the catalytic converter, and a heat insulating layer (usually in the exhaust passage to the catalytic converter) The air layer) is required to be provided, and the establishment of the 4-2-1 format becomes more difficult due to such a large diameter of the branch.

  For this reason, instead of the above 4-2-1 type, a so-called 4-1 type exhaust manifold in which four branches are gathered immediately before the catalytic converter has attracted attention. Compared to the 4-2-1 type, the output in the middle and low rotation range of the internal combustion engine is slightly inferior in terms of exhaust pulsation utilization, but it is superior in output in the high rotation range. By overall tuning (matching) with the pipe, the engine output performance equivalent to that of the 4-2-1 type can be obtained as a whole exhaust system. Moreover, since four branches can be assembled immediately before the catalytic converter, it is easy to realize a three-dimensional layout even in a narrow arrangement space and when a heat insulating layer is provided outside. . However, to prevent exhaust interference and noise, it is necessary to make the lengths of the four branches equal. Therefore, the difference between the longest and shortest branch lengths (path lengths) should be compared with the optimal path length (target value). The error is preferably within 10%. For example, if the optimum length is 30 cm, it is desirable that the difference between the longest and shortest is within 3 cm.

  By the way, in the above-mentioned Patent Document 2, a catalytic converter is arranged on the side portion of the internal combustion engine through an exhaust manifold having a double pipe structure in a 4-2-1 format. In order to adopt the 4-2-1 type in such a narrow space, the branch of the first cylinder and the branch of the second cylinder are forcibly merged, and the branch of the third cylinder and the branch of the fourth cylinder are merged (4 → 2), the rear end of each merging portion is opened (2 → 1) into the upper cone of the catalytic converter. That is, the exhaust manifold (integrated with a catalytic converter) is configured in the 4-2-1 format in view of the purification efficiency, but the branch connection between the first cylinder and the second cylinder and the third cylinder that may cause exhaust interference. Since the fourth cylinder has a branch connection and the four branch lengths on the internal combustion engine side are extremely short and unequal, there is a risk that exhaust efficiency (output performance of the internal combustion engine) will be significantly deteriorated. is there.

  In addition, when the 4-2-1 type is configured by a branch connection of a general first cylinder and a fourth cylinder and a branch connection of a second cylinder and a third cylinder, a branch as described in Patent Document 4 described above is also used. Since the length is extremely short and unequal, the same problem as in Patent Document 1 is included. After all, in the 4-2-1 type exhaust manifold, it is extremely difficult to ensure both the output performance required for the recent internal combustion engine and the exhaust purification efficiency.

  On the other hand, in the above-mentioned Patent Document 3, an exhaust manifold having a heat insulating air layer is proposed substantially in the 4-1 format, and the double pipe structure described above is configured. However, the branches of the first cylinder and the fourth cylinder are equal in length, and the branches of the second cylinder and the third cylinder are also approximately equal in length, but the path difference between the former and the latter units increases. This is a configuration unique to an in-line four-cylinder internal combustion engine in which the exhaust ports of the adjacent second cylinder and the third cylinder exist from the center, whereas the exhaust ports of the first cylinder and the fourth cylinder exist outside. Due to Therefore, although the path length of the four branches can be sufficiently secured, the exhaust interference due to the path difference still cannot be dealt with. Furthermore, since a press product covering from the first cylinder to the fourth cylinder at both ends is essential, a huge press die is required, which causes a cost increase. This also applies to Patent Document 4.

  As described above, in particular, in an exhaust manifold (or an exhaust manifold incorporating a catalytic converter, a so-called maniverter) in which the catalytic converter is disposed in the vicinity of the internal combustion engine and connected between the two, There is an urgent need for both ensuring the output performance and ensuring the exhaust purification efficiency of the exhaust purification means disposed on the downstream side, but this cannot be satisfied by some conventional exhaust manifolds.

  Accordingly, an object of the present invention is to provide an exhaust manifold that can be appropriately disposed in a narrow space near the internal combustion engine and can ensure both the output performance of the internal combustion engine and the exhaust purification efficiency. .

  In order to achieve the above object, according to the present invention, the exhaust manifold of an in-line four-cylinder internal combustion engine as described in claim 1, the first, second, third, and The first and second inlets communicating with each of the first and second exhaust ports of the fourth exhaust ports and the independent first and second exhaust ports respectively. A first manifold unit formed by forming the first and second exhaust passages as one unit, and third and fourth inlets communicating with each of the third and fourth exhaust ports; A second manifold unit formed by forming independent third and fourth exhaust passages having independent third and fourth exhaust ports as a unit, and the first and second exhaust flows; Path and third and fourth exhaust streams With substantially equal forming a path length of, in which the first and second outlet and the third and fourth outlet and to communicatively connected to a single exhaust port.

  For example, as described in claim 2, by relatively changing the distance to the internal combustion engine at the center of each of the first and second exhaust flow paths and the third and fourth exhaust flow paths, The path lengths of the first and second exhaust flow paths and the third and fourth exhaust flow paths may be formed substantially equal.

  Alternatively, as described in claim 3, the opening positions of the first and second discharge ports and the third and fourth discharge ports in the discharge port are relatively changed to change the first and second discharge ports. The path lengths of the second exhaust flow path and the third and fourth exhaust flow paths may be formed to be substantially equal.

  Furthermore, as described in claim 4, while the relative distance to the internal combustion engine at the center of each path in the first and second exhaust flow paths and the third and fourth exhaust flow paths is changed, The opening positions of the first and second discharge ports and the third and fourth discharge ports in the discharge port are relatively changed, so that the first and second exhaust flow paths and the third and third discharge ports are changed. The path lengths of the four exhaust flow paths may be formed to be substantially equal.

  In the exhaust manifold of the internal combustion engine, as described in claim 5, the first manifold unit is formed so as to include each of the first and second exhaust passages through a gap. The second manifold unit may be formed so as to include each of the third and fourth exhaust flow paths via a gap.

  In the exhaust manifold of the internal combustion engine, as described in claim 6, the first and second exhaust ports and the third and fourth exhaust ports are placed in the exhaust port via a buffer member. It is good to support. The first to fourth exhaust passages may be formed by metal pipes or may be formed by joining halves of a press-processed product.

  Since this invention is comprised as mentioned above, there exist the following effects. That is, according to the exhaust manifold of the internal combustion engine according to the first aspect, the first and second inlets communicating with the first and second exhaust ports adjacent to each other and the first and second inlets independent of each other are provided. And a first manifold unit formed by forming independent first and second exhaust flow paths having two discharge ports as one unit, and connected to each of the adjacent third and fourth exhaust ports. A second manifold unit formed by forming the third and fourth inlet ports and the independent third and fourth exhaust passages having independent third and fourth exhaust ports as a unit. Provided, the first and second exhaust passages and the third and fourth exhaust passages have substantially the same path length, and the first and second exhaust ports and the third and fourth exhaust ports are simply provided. Configured to communicate with one discharge port Because it is also in a narrow space of the internal combustion engine near can be properly arranged, it is possible to achieve both the ensuring of the exhaust gas purification efficiency and output performance of the internal combustion engine.

  For example, as described in claim 2, by changing the distance of the center of each path in each exhaust passage relative to the internal combustion engine to form the path lengths of each exhaust passage substantially equal, While ensuring the output performance, it can be properly and reliably disposed in a narrow space.

  Further, as described in claim 3, the path lengths of the respective exhaust passages can be easily formed to be substantially equal by changing the opening positions of the respective outlets in the discharge port relatively.

  Furthermore, if constituted as described in claim 4, the path lengths of the respective exhaust passages can be more easily formed to be substantially equal, and the exhaust manifold can be appropriately and reliably disposed in a narrow space. .

  Further, as described in claim 5, the first manifold unit is formed so as to contain each of the first and second exhaust flow paths via a gap, and the second manifold unit is formed in the first manifold unit. By forming each of the third and fourth exhaust flow paths through a gap, it is possible to secure good heat insulation and easily ensure the output performance of the internal combustion engine and the exhaust purification efficiency. Both can be achieved.

  According to the sixth aspect of the present invention, if each discharge port is configured to be supported in the discharge port via the buffer member, the first and second manifold units are appropriately and reliably placed in the exhaust manifold. Can be held.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 to 7 show an exhaust manifold of an internal combustion engine according to a first embodiment of the present invention, and FIGS. 8 to 10 show an exhaust manifold according to a second embodiment of the present invention. A general exhaust manifold is composed of an inlet side and an outlet side flange and a branch connecting between them, and is also called an exhaust manifold, but the flange is not necessarily required, and its structure is composed of welded pipes. There are various types such as those formed by integral casting of castings, or combinations thereof. In general, the downstream side of the exhaust manifold is connected to the catalytic converter, but the one in which the catalytic converter is accommodated in the exhaust manifold is particularly called a maniverter, and this is also included in the exhaust manifold in a broad sense. Hereinafter, the configuration of the exhaust manifold according to the first embodiment of the present invention will be described, and after comparing the exhaust manifold with the conventional structure, a so-called maniverter will be described as the exhaust manifold according to the second embodiment.

  1 and 2 show an exhaust manifold according to a first embodiment of the present invention. A head flange 10 bolted to an in-line four-cylinder internal combustion engine (not shown) has a head flange 10 as shown in FIG. First to fourth exhaust ports 11 to 14 are formed adjacent to each other in order from the front (left side in FIG. 1) of the internal combustion engine (11 to 14 strictly communicate with the exhaust port of the internal combustion engine). Although it is a hole, it is described here as an exhaust port). A first branch 21 is connected in communication with the first exhaust port 11, and a first introduction port is formed by an opening on the connection side, and a first discharge port is formed by an opening on the other side. A first exhaust passage is formed in one branch 21. Similarly, a second branch 22 is connected in communication with the second exhaust port 12, and a second introduction port is formed by the opening on the connection side, and a second discharge port is formed by the opening on the other side. In addition, a second exhaust flow path is configured in the second branch 22. Then, the upper case 1a and the lower case 1b are welded and joined so as to surround the first branch 21 and the second branch 22 via a predetermined gap, and a first manifold having a so-called monaca structure (shell structure). Unit 1 is formed. The discharge port side end portions of the first and second branches 21 and 22 are supported in the upper case 1a and the lower case 1b via metal cushioning members (wire mesh) 25a and 25b shown in FIG. Yes.

  Thus, the first and second branches 21 and 22 are supported with a certain distance from the inner peripheral surfaces of the upper case 1a and the lower case 1b, and the discharge port side end portions of the respective branches are the upper case 1a and the lower case. It is supported (so-called floating support) so as to be allowed to move relative to 1b. Such relative movement occurs when each branch is expanded by being heated by high-temperature exhaust gas, but the amount and direction of thermal expansion depend on the path length and path shape of each branch, so there are individual differences. Resulting in relative movement between the branches. Further, relative movement also occurs with respect to the upper case 1a and the lower case 1b whose temperature is relatively lower than that of each branch. Therefore, buffer members 25a and 25b that allow relative movement are required between the branches and between each branch and the upper case 1a and the lower case 1b.

  The third branch 23 is connected to the third exhaust port 13, and the third introduction port is formed by the opening on the connection side, and the third discharge port is formed by the opening on the other side. A third exhaust passage is formed in the third branch 23. Similarly, a fourth branch 24 is connected to the fourth exhaust port 14, and a fourth introduction port is formed by the opening on the connection side, and a fourth discharge port is formed by the opening on the other side. In addition, a fourth exhaust flow path is configured in the fourth branch 24. Then, the upper case 2a and the lower case 2b are welded and joined so as to surround the third branch 23 and the fourth branch 22 via a predetermined gap to form the second manifold unit 2 having a monaca structure. The Further, the discharge port side end portions of the third and fourth branches 23 and 24 are also supported in the upper case 2a and the lower case 2b via buffer members (wire mesh) 26a and 26b shown in FIG.

  The first to fourth branches 21 to 24 are, for example, stainless steel pipes, and are formed so that the path lengths of the first to fourth exhaust flow paths formed by the branches are substantially equal. That is, in FIG. 1 in plan view, the first and second adjacent ones in the exhaust passages of the first to fourth branches 21 to 24 are changed so that the distance to the internal combustion engine is relatively changed. The first and second branches 21 and 22 connected in communication with the exhaust ports 11 and 12 are combined to form the first manifold unit 1 as one unit, and the third and fourth exhaust ports adjacent to each other. The third and fourth branches 23 and 24 that are connected in communication with 13 and 14 are collected to form the second manifold unit 2 as one unit, and the first manifold unit 1 and the second The manifold unit 2 is formed as shown in a side view in FIG. The details will be described later with reference to FIGS. Then, the upper case 1a and the lower case 1b that house the first and second branches 21 and 22 and the third and fourth branches 23 and 24 to form the first manifold unit 1 and the second manifold unit 2, respectively. The upper case 2a and the lower case 2b are also made of metal, and predetermined gaps are formed in the first and second branches 21 and 22 and the third and fourth branches 23 and 24 formed as described above. It is press-molded into a half-shell (half shell) with an inner surface shape.

  As for the 1st manifold unit 1 comprised as mentioned above, the discharge port side edge part of the 1st and 2nd branch 21 and 22 is the 3rd and 4th branch 23 of the 2nd manifold unit 2, respectively. And 24 are arranged so as to face the discharge port side end portions (see FIG. 4), and the upper case 3a and the lower case 3b of the connection case 3 are welded and joined so as to surround these discharge port side end portions. It becomes. Thus, the connecting case 3 and the cases of the first and second manifold units 1 and 2 bear the strength of the exhaust manifold as outer shells (that is, each branch does not bear the strength). The open end of the connection case 3 is fitted into the connection pipe 32 and welded. Thus, the first and second discharge ports and the third and fourth discharge ports are connected in communication with a single discharge port (open end of the connection case 3). Further, a downstream flange 30 is welded to the connection pipe 32, and a bracket 33 is welded to the flange 30. The connecting case 3 does not have the so-called monaca structure of the upper case 3a and the lower case 3b, but may be an integral part or may be formed integrally with the connecting pipe 32.

  5 and 6 show another example of the discharge port side end structure of the first and second manifold units 1 and 2, and as is apparent from FIG. 6, the first and second branches 21 are shown. 3 and 4, the third and fourth branches 23 and 24 are formed longer. That is, as described above, in addition to being configured such that the distances to the internal combustion engine at the center of each path in the first and second exhaust flow paths and the third and fourth exhaust flow paths change relatively, By being configured as shown in FIG. 6, the first and second exhaust passages and the third and fourth exhaust passages are formed to have substantially the same path length. For example, the first and second branches 21 and 22 are inserted 8 mm from the opening end of the upper case 3c, and the third and fourth branches 23 and 24 are respectively inserted 13 mm from the opening end of the lower case 3d. That is, fine adjustment is performed by providing a path difference in the exhaust flow path according to the difference in opening position. Further, if necessary, path difference adjustment in each manifold unit, that is, adjustment of insertion allowance between the first and second branches 21 and 22, and insertion allowance between the third and fourth branches 23 and 24 are performed. The path lengths of the four branches can be individually adjusted.

  As shown in FIGS. 5 and 6, the discharge port side end portions of the first and second branches 21 and 22 are supported in the upper case 1a and the lower case 1b via the buffer members 27a and 27b. The discharge port side end portions of the third and fourth branches 23 and 24 are also supported in the upper case 2a and the lower case 2b via the buffer members 28a and 28b. The buffer members 27a and 27b and 28a and 28b are formed by integrating the buffer members of FIG. 4 in a large size, and are divided into two parts. However, the buffer members 27a and 27b may be provided over the entire circumference of the end of each branch. Good. In addition to the wire mesh, any member may be applied as long as the member has heat resistance, a buffer function, and a certain degree of airtightness. Further, in this embodiment, the side end portion of the lower case 3d is combined with the side end portion of the upper case 3c so that the fillet welding is performed at the overlap portion LW, so that butt welding on a horizontal plane is possible. Compared to welding workability and reliability.

  Alternatively, the discharge port side end portions of the first and second branches 21 and 22 and the discharge port side end portions of the third and fourth branches 23 and 24 are connected to the upper case 1a and the lower case as shown in FIG. You may comprise so that it may each extend from the front-end | tip of 1b, and the front-end | tip of upper case 2a and lower case 2b. Then, as shown in FIG. 7, the discharge port side ends of the first and second branches 21 and 22 and the discharge port side ends of the third and fourth branches 23 and 24 are connected to the buffer members 27c and 28c. You may comprise so that it may mutually support via. That is, the discharge port side ends of the first and second branches 21 and 22 are supported on the inner surface of the upper case 3c via the buffer member 27c, and the discharge port side ends of the third and fourth branches 23 and 24 are supported. The discharge port side end portions of the third and fourth branches 23 and 24 are supported on the inner surface of the lower case 3d via the buffer member 28c, and the discharge ports of the first and second branches 21 and 22 are supported. It can comprise so that it may support in a side edge part. The buffer members 27c and 28c are integrally formed over the entire circumference of the end of each branch, but each may be divided into two or more.

  When the schematic configuration of the first embodiment is shown in a plan view, it is as shown in FIG. 11B, but when the configuration that is symmetrical in plan view is a basic configuration, it is as shown in FIG. . In FIG. 11A, the first branch B1 (corresponding to 21 in FIG. 1) and the second branch B2 (corresponding to 22 in FIG. 1) constituting the adjacent first and second exhaust flow paths. A first manifold unit U1 (corresponding to 1 in FIG. 1) is formed, and third branches B3 (corresponding to 23 in FIG. 1) and fourth constituting adjacent third and fourth exhaust flow paths are formed. The second manifold unit U2 (corresponding to 2 in FIG. 1) is formed by the branch B4 (corresponding to 24 in FIG. 1). The discharge ports of the first and second manifold units U1 and U2 are connected in communication with a single discharge port (formed on the connection flange CF on the downstream side in FIG. 11). The first and second branches B1 and B2 are connected to the adjacent first and second exhaust ports (formed in the head flange HF in FIG. 11), and are connected to the third and fourth branches B3 and B3. Since B4 is connected to the adjacent third and fourth exhaust ports (head flange HF), the first to fourth branches B1 to B4 are formed, as is apparent from FIG. The path lengths of the first to fourth exhaust flow paths are substantially equal.

  On the other hand, in FIG. 11B, which is a schematic configuration of the first embodiment of the present invention, the discharge port (connection flange CF in FIG. 11) is one side (for example, an internal combustion engine) with respect to the left-right symmetry axis in plan view. (Front side) is biased by a distance α. Therefore, the path lengths of the exhaust flow paths of the third and fourth branches B3 and B4 (hereinafter simply referred to as path lengths) are longer than the path lengths of the first and second branches B1 and B2. On the other hand, first, in the first manifold unit U1, the first and second branches B1 and B2 are connected to the adjacent first and second exhaust ports to form adjacent exhaust flow paths. Therefore, the difference in path length can be minimized, and the same is true in the second manifold unit U2.

  Next, the path difference between the first and second manifold units U1 and U2 in FIG. 11B inevitably occurs due to the deviation of the distance α. In this embodiment, the exhaust flow The path difference is minimized by adjusting the path three-dimensionally. That is, as shown in FIG. 12 which is a schematic diagram of FIG. 2, the shorter first and second branches B1 and B2 in the plan view (FIG. 11B) are moved in the β direction (horizontal direction) by the path difference and It is adjusted so that the lengths of the exhaust passages are substantially equal by bending in the γ direction (vertical direction). Furthermore, even when the path difference between the branches in the first and second manifold units U1 and U2 is large, the shorter branch is bent in the β direction and / or the γ direction in FIG. Are adjusted to be substantially equal in length. Even when the discharge port (connection flange CF) is biased toward the rear side of the internal combustion engine, the length of the exhaust passage can be adjusted similarly.

  Thus, also in the first embodiment of the present invention schematically shown in FIGS. 11B and 12, each exhaust from each exhaust port (head flange HF) to a single exhaust port (connection flange CF). The lengths of the flow paths are substantially equal, and can be within 10% of the error that is ideal for the above-described 4-1 type exhaust manifold. If it is necessary to adjust the length of the exhaust flow path with better accuracy, as shown in FIGS. 6 and 7, the difference in the opening position of each branch causes a path difference in the exhaust flow path. It is sufficient to make fine adjustments.

  13 (a) to 13 (c) show schematic configurations of Patent Documents 1 to 3 described above, respectively, and the difference becomes clear when compared with the schematic configuration of the first embodiment of the present invention. The specific effect of the first embodiment becomes clearer. In FIGS. 13A and 13B, Y-shaped exhaust passages are formed in (A) and (B), and the above-described 4-2-1 type exhaust manifold is configured. In (B) and (C), a double pipe is configured. In (B), units Ua and Ub are arranged in parallel, and in (C) there are a plurality of cases. The units are superposed to form a unit Uc and are combined into a common discharge port. In (a), a double pipe is not constructed.

  In (A) and (C), the first branch B1 and the fourth branch B4 are combined so that they merge, and the second branch B2 and the third branch B3 are combined so that they merge. This is a configuration generally performed in an in-line four-cylinder internal combustion engine from the past, and has a large exhaust path difference and is difficult to adjust. On the other hand, in (b), the Y-shaped exhaust flow path where the adjacent first and second branch parts Ba and Bb merge together and the adjacent third and fourth branch parts Bc and Bd merge. Although it has a letter-shaped exhaust flow path, it is basically of the 4-2-1 format, and the path of each branch part Ba to Bd is extremely short and can be compared with the exhaust flow path in other aspects. is not.

  On the other hand, FIG. 13 (a) shows that the first branch B1 and the fourth branch B4 are combined so that the first branch B1 and the fourth branch B4 merge in the above-described 4-2-1 type exhaust manifold, and the second branch B2 and the third branch B3. A method of approximating the length of the exhaust passage is disclosed with respect to the configuration of a conventional in-line four-cylinder internal combustion engine that is integrated so that the branches B3 merge together. This is illustrated in FIGS. There is no necessity to apply to (c), and (b) and (c) cannot be applied as they are because they are double pipes. In particular, (c) is characterized in that a plurality of cases are superposed and integrated, so it is very difficult to adjust the length of the exhaust passage.

  Next, an exhaust manifold according to a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment as well, as in the first embodiment described above, the first and second manifold units 1 and 2 are three-dimensionally configured so that the path lengths of the exhaust passages are substantially equal. The first and second manifold units 1 and 2 are formed in a monaca structure by an upper case 1c and a lower case 1d, and an upper case 2c and a lower case 2d, which are press-formed products. As shown in the CC cross section of FIG. 8 in FIG. 9, a monaca structure (so-called θ pipe structure) in which an upper case 4 a and a lower case 4 b are joined via a partition plate 4 c in the first manifold unit 1. Inner case is housed. Thereby, the 1st and 2nd exhaust flow paths 41 and 42 are formed in the both sides of the partition plate 4c, and the 1st and 2nd branch is comprised, respectively. Similarly, in the second manifold unit 2, as is clear from the DD cross section of FIG. 8 shown in FIG. 10, the inner case of the monaca structure in which the upper case 4 d and the lower case 4 e are joined via the partition plate 4 f. A case is accommodated, and third and fourth exhaust passages 43 and 44 are formed on both sides of the partition plate 4f, and third and fourth branches are formed, respectively.

  As shown in FIG. 10 (DD cross section in FIG. 8), the opening end portions of the first and second manifold units 1 and 2 are each formed in a semicircular cross section, and the plane portions (lower case 1d and upper case) In a state where the case 2 c) is in close contact and has a so-called θ pipe structure with a substantially circular cross section, it is fitted into the straight pipe portion 51 at one end of the catalytic converter 50 and welded to the straight pipe portion 51. Thus, the straight pipe portion 51 constitutes a gathering portion in the above-described 4-1 format, and a space from the tapered portion 52 continuing to the straight pipe portion 51 of the catalytic converter 50 to the inlet of the catalyst carrier (not shown) is provided. An opening space is formed, and each branch (exhaust flow path) is opened in this space. The upper case 4a, the lower case 4b, the upper case 4d, and the lower case 4e are disposed in the opening end portions of the first and second manifold units 1 and 2 in the range where the straight pipe portion 51 is fitted and inserted. 46 is fitted. The buffer members 45 and 46 may be any members as long as they have heat resistance, a buffer function, and a certain degree of airtightness, and may be wire meshes as in the first embodiment.

  In the body of the catalytic converter 50 shown in FIG. 8, a ceramic catalyst carrier (not shown) is held via a buffer mat. A necking portion 53 (consisting of a straight tube portion 51 and a taper portion 52) and a necking portion 56 (consisting of a straight tube portion 54 and a taper portion 55) are integrally formed at both ends of the catalytic converter 50 by spinning. Yes. In the present embodiment, the downstream necking portion 56 is formed by so-called inclined spinning so that the axis of the straight pipe portion 54 is inclined with respect to the axis of the body of the catalytic converter 50. In addition, about the process of both necking parts 53 and 56 of the catalytic converter 50, the spinning process by at least one of a coaxial, eccentricity, an inclination, and a twist can be applied, and it can be set as arbitrary shapes.

  As described above, in the second embodiment, both the outer manifold unit and the inner case forming the exhaust passage have a monaca structure, so that the degree of freedom in shape is greater than that of the first embodiment. In the narrow space, it is easy to equalize the exhaust flow path when realizing the above-mentioned 4-1 format. Further, since the variable cross section can be set freely, it is possible to set an exhaust flow path shape with a small flow path resistance. Furthermore, the shape of the half-divided body (half-shell) can be freely set, and any means such as TIG, MIG, laser, brazing, etc. may be used as the welding means.

  In this embodiment, the straight pipe portion 54 of the catalytic converter 50 may be welded to a component to be connected (downstream exhaust pipe or the like), or the straight pipe portion 54 may be flanged, a universal joint, a wake exhaust pipe, or the like. It is good also as fitting (not shown). Alternatively, the body of the catalytic converter 50 may be replaced with a metal carrier (not shown). In that case, an outer cylinder of the metal carrier is sandwiched between both end cones (not shown) and fixed by welding. The Alternatively, a silencer (not shown) such as a sub muffler or a pre-muffler may be provided instead of the catalytic converter 50, and the silencer and the catalytic converter 50 may be provided side by side. Furthermore, a silencer structure (expansion, resonance, sound absorption structure) may be formed in the space in the catalytic converter 50.

It is a front view which shows the exhaust manifold which concerns on 1st Example of this invention. It is a side view which shows the exhaust manifold which concerns on 1st Example of this invention. It is a front view which shows the head flange in 1st Example of this invention. FIG. 3 is a cross-sectional view showing a cross section taken along line AA of FIG. 2 in the cross section of the discharge port side end portion of the first and second manifold units in the first embodiment of the present invention. It is sectional drawing which shows the other example of the discharge port side edge part structure of a 1st and 2nd manifold unit. It is sectional drawing which shows the BB line cross section of FIG. 5 in the other example of the discharge port side edge part structure of a 1st and 2nd manifold unit. It is sectional drawing corresponding to the BB line cross section of FIG. 5 in the further another example of the discharge port side edge part structure of a 1st and 2nd manifold unit. It is a front view which shows the exhaust manifold which concerns on 2nd Example of this invention. It is sectional drawing which shows the CC line cross section of FIG. It is sectional drawing which shows the DD sectional view of FIG. It is a top view which shows schematic structure of the exhaust manifold which concerns on 1st Example of this invention. 1 is a side view showing a schematic configuration of an exhaust manifold according to a first embodiment of the present invention. 5 is a plan view showing a schematic configuration of an exhaust manifold described in Patent Documents 1 to 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st manifold unit 2 2nd manifold unit 3 Connection case 10 Head flange 11 1st exhaust port 12 2nd exhaust port 13 3rd exhaust port 14 4th exhaust port 21 1st branch 22 2nd Branch 23 third branch 24 fourth branch 30 connecting flange 50 catalytic converter

Claims (6)

  In the exhaust manifold of the in-line four-cylinder internal combustion engine, the first and second exhaust ports of the first, second, third, and fourth exhaust ports adjacent to each other in order from the front of the internal combustion engine communicate with each other. A first manifold unit formed by forming the first and second inlets connected to each other and the first and second exhaust passages having independent first and second outlets as a unit. Each of the third and fourth exhaust ports communicating with each of the third and fourth exhaust ports and having independent third and fourth exhaust ports, respectively. A second manifold unit formed by forming the exhaust flow path as a unit, and the path lengths of the first and second exhaust flow paths and the third and fourth exhaust flow paths are substantially equal, The first and second outlets The third and the exhaust manifold of an internal combustion engine, wherein a fourth outlet for communicatively connected to a single exhaust port each time.   The first and second exhaust flow paths and the first and second exhaust flow paths and the third and fourth exhaust flow paths are changed by relatively changing the distances to the internal combustion engine. 2. An exhaust manifold for an internal combustion engine according to claim 1, wherein the third and fourth exhaust passages have substantially the same path length.   The opening positions of the first and second discharge ports and the third and fourth discharge ports in the discharge port are relatively changed, so that the first and second exhaust flow paths and the third and third discharge ports are changed. 4. An exhaust manifold for an internal combustion engine according to claim 1, wherein the lengths of the four exhaust flow paths are formed to be substantially equal.   The distance between the center of each of the first and second exhaust flow paths and the third and fourth exhaust flow paths with respect to the internal combustion engine is changed relatively, and the first and second exhaust ports and The opening positions of the third and fourth exhaust ports in the exhaust port are relatively changed so that the path lengths of the first and second exhaust flow paths and the third and fourth exhaust flow paths are substantially equal. 2. An exhaust manifold for an internal combustion engine according to claim 1, wherein the exhaust manifold is formed.   The first manifold unit is formed so as to contain each of the first and second exhaust flow paths via a gap, and the third and second exhaust passages are formed in the second manifold unit via a gap. 5. The exhaust manifold for an internal combustion engine according to claim 1, wherein the exhaust manifold is formed so as to include each of the four exhaust passages. The said 1st and 2nd discharge port and the 3rd and 4th discharge port are supported in the said discharge port via a buffer member, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. An exhaust manifold for internal combustion engines.

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