JP2007278156A - Engine exhaust system - Google Patents

Abstract

The present invention relates to an exhaust system for a multi-cylinder engine that collects exhaust gas discharged from a plurality of cylinders, for example, by an exhaust manifold and guides the exhaust gas to a downstream exhaust pipe or the like. An exhaust system for an engine having excellent exhaust purification performance and exhaust purification efficiency is provided by preventing the exhaust temperature from decreasing as much as possible.
An exhaust system for an engine in which an exhaust manifold is connected to an exhaust port in the cylinder head by attaching an end of the exhaust manifold on the engine side to a cylinder head via a flange joint. The exhaust guide cylinder 20 covering the inner peripheral surface of the flange joint 16 is provided in the exhaust passage extending from the exhaust port 3 into the exhaust manifold 5 so as to be separated from the inner peripheral surface of the flange joint. Features.
[Selection] Figure 3

Description

  The present invention relates to an exhaust system for an engine such as an automobile diesel engine or a gasoline engine, and more particularly to an exhaust system for a multi-cylinder engine that collects exhaust gas discharged from a plurality of cylinders by an exhaust manifold and guides it to a downstream exhaust pipe. .

  Conventionally, in a multi-cylinder engine having a plurality of cylinders, exhaust discharged from each cylinder is generally collected by an exhaust manifold and guided to a silencer or the like via an exhaust pipe connected to the downstream side thereof. As the exhaust manifold as described above, ones made of cast metal have been conventionally used as disclosed in Patent Document 1 below.

  Recently, however, especially in automobile engines, exhaust gas regulations have recently become more and more strict, and more excellent exhaust gas purification measures and aftertreatments are required. For example, efficient purification measures using a catalytic converter using a selective reduction type NOx catalyst, an oxidation catalyst, etc., and in the case of a diesel engine, particulate matter (PM) with carbon as a main component by DPF (diesel particulate removal device) ) Is more effectively removed.

  In order to efficiently perform the above-described purification measures and after-treatment, a large amount of heat energy is required. In particular, the exhaust gas emitted from the engine does not decrease in temperature as much as possible until it reaches the catalytic converter or DPF. It is desirable to do so. However, the casting exhaust manifold as described above is heavy and heat mass is high. Therefore, a large amount of heat is lost in the process of exhaust passing through the exhaust manifold, and the exhaust temperature tends to decrease.

  Therefore, it has been proposed to form a double exhaust manifold as shown in Patent Document 2 below to prevent the exhaust temperature flowing through the manifold from decreasing as much as possible. Is generally attached to the engine with bolts or the like through a thick metal flange joint provided integrally therewith, and a part of the exhaust when flowing from the engine into the manifold is part of the flange joint. There was a problem that the exhaust temperature was lowered due to direct or almost direct contact with the inner peripheral surface.

Japanese Patent Laid-Open No. 7-83048 JP-A-8-338240

  The present invention has been proposed in view of the above problems, and provides an exhaust system for an engine having excellent exhaust purification performance and exhaust purification efficiency by preventing a decrease in exhaust temperature at the end of the exhaust manifold on the engine side as much as possible. The purpose is to do.

In order to achieve the above object, an exhaust system for an engine according to the present invention has the following configuration. That is, in an exhaust system of an engine in which the exhaust manifold is connected to the exhaust port in the cylinder head by attaching the end of the exhaust manifold on the engine side to the cylinder head via a flange joint, the exhaust manifold is connected to the exhaust manifold. An exhaust guide cylinder that covers the inner peripheral surface of the flange joint is provided in the exhaust passage leading to the inner space, spaced apart from the inner peripheral surface of the flange joint.

  As described above, the exhaust guide cylinder that covers the inner peripheral surface of the flange joint is provided in the exhaust passage extending from the exhaust port into the exhaust manifold so as to flow from the engine into the manifold. It is possible to prevent as much as possible that a part of the exhaust at that time is in direct or almost direct contact with the inner peripheral surface of the flange joint as in the prior art and the exhaust temperature is lowered at the end. As a result, exhaust gas is introduced into a catalytic converter or DPF disposed downstream of the exhaust manifold at a relatively high temperature state so that exhaust gas purification can be performed efficiently and satisfactorily. An engine exhaust device having excellent exhaust purification efficiency can be provided.

  Hereinafter, the present invention will be specifically described based on embodiments shown in the drawings. FIG. 1 is a perspective view showing an embodiment of an exhaust system for an engine according to the present invention, FIG. 2 is an AA enlarged sectional view in FIG. 1, and FIG.

  The present embodiment is applied to an exhaust device of a multi-cylinder engine for automobiles, particularly an in-line 6-cylinder diesel engine 1, and exhausts from a combustion chamber 2 of each cylinder to an exhaust port 4 through two exhaust valves 3 and 3, respectively. After the collected exhaust gas is gathered by the exhaust manifold 5, the exhaust gas is led to a silencer or the like omitted in the drawing through an exhaust pipe 6 connected to the downstream side of the exhaust manifold 5. Although a catalytic converter and a DPF are also provided on the downstream side of the exhaust pipe 6, they are omitted in the drawing. In the figure, 8 is an intake valve, 9 is an intake port, 10 is a cylinder head, 11 is a cylinder, and 12 is a piston.

  In the present embodiment, the exhaust manifold 5 is formed into an inner / outer duplex over substantially the entire length, and in the case of the figure, the inner / outer duplex is composed of a branch-like inner tube 51 and an outer tube 52 covering the branch inner tube 51. The heat insulating space (air heat insulating layer) S having a predetermined interval is formed between the inner tube 51 and the outer tube 52. The inner tube 51 and the outer tube 52 do not necessarily have a tubular shape. For example, the inner tube 51 and the outer tube 52 may be formed such that a pair of halves having a semicircular cross section face each other. In the figure, reference numeral 15 denotes a flexible tube made of a bellows tube or the like for absorbing expansion and contraction and vibration due to heat of the exhaust manifold 5, and the flexible tube 15 is also formed in an inner and outer double, but is not shown in the drawing. did.

  As shown in FIGS. 2 and 3, the end on the upstream side of the exhaust manifold 5 composed of the inner and outer pipes 51 and 52, that is, the end on the engine 1 side, enlarges the inner pipe 51 or shrinks the outer pipe 52. The end portions 51a and 52a of the inner and outer pipes 51 and 52 are overlapped with each other, and the flange joint 16 made of a ring-shaped thick metal plate is fitted to the outside of the overlapping portion and integrated by welding or the like. The flange joint 16 is connected and fixed to the cylinder head 10 of the engine 1 with a stat bolt 17 or a nut 18 so that the exhaust port 4 of each cylinder is connected to the exhaust manifold 5. Has been.

  As shown in FIGS. 2 and 3, the present invention provides an exhaust guide cylinder 20 covering the inner peripheral surface of the flange joint 16 in the exhaust passage extending from the exhaust port 4 to the exhaust manifold 5. The exhaust guide cylinder 20 is provided with a distance from the inner peripheral surface. The length of the exhaust guide cylinder 20 is appropriate, but in this embodiment, the inner peripheral surface of the flange joint 16 and the upstream of the inner pipes 51 on both sides thereof. The side end 51 a and a length covering a part of the downstream end of the exhaust port 4 are formed.

  The exhaust guide cylinder 20 is appropriately attached. For example, the downstream end of the cylinder 20 may be fixed to the exhaust manifold 5 by welding or the like. The end portion 20a on the downstream side of the exhaust guide cylinder 20 is fixed to the inner peripheral surface of the end portion of the inner pipe 51 on the engine side by spot welding or the like. The upstream end 20b of the exhaust guide cylinder 20 is configured to protrude into the exhaust port 4 through the inside of the flange joint 16 in the figure, and the exhaust guide cylinder 20 and the flange joint 16 are projected. The exhaust port 4 and the exhaust port 4 are in a non-contact state by being separated from each other at a predetermined interval.

  The exhaust port 11 side end 20b of the exhaust guide cylinder 20 may be expanded in a gentle trumpet shape as necessary. In the case of the figure, the end of the exhaust guide cylinder 20 on the exhaust port 4 side is preferred. The portion is formed into a curved surface that is gently curved outward in the radial direction, and the tip is cut by a substantially cylindrical surface concentric with the exhaust guide cylinder 20. Even in this case, it is desirable that the end portion 20 b on the exhaust port 4 side of the exhaust guide cylinder 20 is not in contact with the inner surface of the exhaust port 4.

  In the figure, 21 and 22 are flange joints for connecting the exhaust manifold 5 and the exhaust pipe 6, and the flange joints 21 and 22 are integrally fixed to the ends of the exhaust manifold 5 and the exhaust pipe 6 by welding or the like. The joints 21 and 22 are connected by bolts and nuts, but are not shown in the figure. In the present embodiment, the exhaust pipe 6 is also formed as an inner / outer double pipe.

  In the above configuration, the exhaust gas flowing into the exhaust port 4 from the combustion chamber 2 of each cylinder through the exhaust valve 3 during operation of the engine 1 is guided into the exhaust guide cylinder 20. At that time, if the end on the upstream side of the exhaust guide cylinder 20, that is, the end 20 a on the exhaust port 11 side is expanded in a gentle trumpet shape as described above, the exhaust guide cylinder 20 is exhausted into the exhaust guide cylinder 20. Can flow smoothly. Then, the exhaust gas flowing into the exhaust guide cylinder 20 is guided into the exhaust manifold 5 through the cylinder 20, and at this time, the exhaust gas hardly contacts the flange joint 16 directly or indirectly. Therefore, a decrease in exhaust temperature is suppressed.

  In particular, in the illustrated embodiment, only one end of the exhaust guide cylinder 20 is in contact with a very small part of the inner pipe 51 of the exhaust manifold 5 formed by the inner and outer pipes 51 and 52. In other respects, the exhaust guide cylinder 20 is not in contact with the outer pipe 52 and the exhaust port 4 as well as the flange joint 16, so that the exhaust temperature can be largely prevented from decreasing.

  In the above-described embodiment, the exhaust guide cylinder 20 that covers the inner peripheral surface of the flange joint 16 is formed separately from the exhaust manifold 5. However, the exhaust manifold 5 is composed of the inner pipe 51 and the outer pipe 52 as shown in the illustrated example. For example, the end of the inner pipe 51 on the engine side is extended into the exhaust port 4 as shown in FIG. 4, for example, thereby extending the extended protrusion 51b. May also serve as the exhaust guide cylinder 20. That is, the extension protrusion 51b may cover the inner peripheral surface of the flange joint 16 in a state of being separated from the inner peripheral surface of the flange joint 16.

  By configuring as described above, the extension protrusion 51b exhibits the same function as the exhaust guide cylinder 20 without lowering the exhaust temperature without providing the exhaust guide cylinder 20 separately as in the above embodiment. Can be prevented. In this case as well, the upstream end 51c of the extended projection 51b of the inner pipe 51 that also serves as the exhaust guide cylinder 20 has a gentle trumpet shape like the upstream end 20b of the exhaust guide cylinder 20. When expanded, the exhaust gas can smoothly flow into the inner pipe 51 from the exhaust port 4. In the figure, reference numeral 53 denotes a ring-shaped interval holding spacer for holding the inner tube 51 and the outer tube 52 at a predetermined interval.

  The exhaust gas introduced into the exhaust manifold 5 through the exhaust guide cylinder 20 or the extended projection 51b of the inner pipe 51 also serving as the exhaust guide cylinder 20 as described above is continuously omitted through the exhaust pipe 6 in the drawing. The catalyst is guided to the catalytic converter or DPF to be purified by the catalyst or remove the particulate matter. At that time, as described above, the exhaust temperature is suppressed from being lowered, and the catalyst converter or DPF is guided to a relatively high temperature. Therefore, the purification process can be performed efficiently. In particular, the selective reduction type NOx catalyst, the oxidation catalyst, and the like have not always been sufficiently purified at the conventional relatively low exhaust temperature, but in the present invention, the exhaust temperature is made as high as possible by adopting the configuration as described above. Therefore, in the case of using DPF, particulate matter and the like can be efficiently removed at an exhaust temperature as high as possible.

  Each of the above embodiments has been described by way of an example in which exhaust gas is guided from the exhaust manifold 5 to the catalytic converter or the DPF via the exhaust pipe 6. However, the exhaust manifold 5 does not pass through the exhaust pipe 6 and the catalytic converter is used. It can also be applied to a structure that leads directly to the DPF or via a silencer.

  As described above, according to the exhaust system for an engine according to the present invention, the temperature of the exhaust gas emitted from the engine can be led to a catalytic converter, a DPF, etc. without being reduced as much as possible. Etc. can be performed efficiently. As a result, a relatively high exhaust temperature can be obtained without using a separate heating means or heat energy to increase the exhaust temperature, and it is possible to easily and inexpensively respond to exhaust gas regulations that have recently become increasingly strict. Become.

The top view which shows one Embodiment of the exhaust apparatus of the engine by this invention. The AA expanded sectional view in FIG. FIG. 3 is an enlarged view of a part of FIG. 2. Sectional drawing which shows other embodiment of the exhaust apparatus of the engine by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Combustion chamber 3 Exhaust valve 4 Exhaust port 5 Exhaust manifold 51 Inner pipe 52 Outer pipe 6 Exhaust pipe 8 Intake valve 9 Intake port 10 Cylinder head 11 Cylinder 12 Piston 15 Flexible pipe 16 Flange joint 17 Stud bolt 18 Nut 20 Exhaust Guide cylinder

Claims (3)

  In an exhaust system of an engine in which the exhaust manifold is connected to the exhaust port in the cylinder head by attaching the end of the exhaust manifold on the engine side to the cylinder head via a flange joint, the exhaust port is connected to the exhaust manifold from the exhaust port. An exhaust system for an engine, wherein an exhaust guide cylinder covering the inner peripheral surface of the flange joint is provided in the exhaust passage to be spaced apart from the inner peripheral surface of the flange joint.   2. The engine exhaust system according to claim 1, wherein the exhaust manifold is formed by an inner pipe and an outer pipe so as to be doubled inside and outside, and the exhaust guide cylinder is provided in an exhaust passage extending from the inner pipe to the exhaust port.   The exhaust manifold is formed by an inner pipe and an outer pipe in an inner and outer double, and an end of the inner pipe on the engine side extends and protrudes into the exhaust port so that the extended protrusion also serves as the exhaust guide cylinder. The engine exhaust system according to claim 1, wherein the engine exhaust system is configured as described above.

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