Engine exhaust structure

Abstract

A temperature regulating material 31 for regulating a temperature of an exhaust manifold 11 is provided such that individual parts of the exhaust manifold 11 are uniformed in temperature. Heat transfer materials 31A with high thermal conductivity are layered as the temperature regulating material 31 on a cover member 25 at an area corresponding to a high-temperature area HT of the exhaust manifold 11. Heat shield materials 31B are layered as the temperature regulating material 31 on the cover member 25 at an area corresponding to the low-temperature area LT of the exhaust manifold 11. A heat dissipation material 31C as the temperature regulating material 31 coats an outer surface of the area of the cover member 25 corresponding to the high-temperature area of the exhaust manifold 11.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an engine exhaust structure.

2. Description of the Related Art

At a middle portion of exhaust passage in an automobile engine, an exhaust manifold, a catalytic converter and a muffler are intervened in this order from the upstream side. Exhaust gases from the engine are collected in the exhaust manifold, purified through the catalytic converter, muffed by the muffler, and then emitted to the outside.

Many mainstream catalytic converters purify exhaust gases by means of a three-way catalyst. However, those catalytic converters using a three-way catalyst have a problem that unpurified exhaust gases are emitted to the outside unless a catalyst temperature reaches an active temperature or higher.

For this reason, there have been proposed engine exhaust structures to shorten the time between when an engine is started and when a catalyst reaches an active temperature or higher, in which a catalyst converter is provided as closely to the collecting part of an exhaust manifold as possible to facilitate a catalyst temperature rise, or in which a flow path of exhaust gases in an exhaust manifold has a two-tiered structure with an inner member and an outer member to form a heat shield space between the two members for prevention of a temperature decrease of exhaust gases in the exhaust manifold (refer to Patent Document 1, for example).

Additionally, there is proposed a sound insulation cover attached to an exhaust manifold (for example, refer to Patent Document 2). The invention described in Patent Document 2 is intended to cut noise from an engine and protect electronic devices and their harnesses disposed in an engine room from an exhaust manifold at a high temperature. Noise-absorbing materials are layered on the sound insulation cover and act as a heat shield. This accelerates an increase in an ambient temperature in the surroundings of the exhaust manifold, thereby promoting the activation of the catalyst.

Patent Document 1 Japanese Patent Application No. 2005-76605

Patent Document 2 Japanese Patent Application No. 7-119458

An exhaust manifold is not at a uniform temperature in the whole. For example, the collecting part and its nearby areas become at higher temperature than the other areas because exhaust gases are collected in those areas from individual cylinders. For this reason, an exhaust manifold is designed to offer thermal resistance with reference to temperatures of the collecting part and its nearby areas. However, this design requires the use of highly heat-resistant and expensive metal materials even for areas at low temperatures as well as the collecting part and its nearby areas, although the areas at low temperature are not needed to be as heat-resistant as the areas at high temperatures. This causes higher costs of manufacturing exhaust manifolds. In particular, if the collecting part and the branched pipe are two-tiered or are covered with a cover member for facilitation of the catalyst temperature during a warm-up and higher performance of exhaust gas purification as with the inventions described in Patent Documents 1 and 2, the performance of exhaust gas purification will be enhanced during the warm-up. Instead, the whole exhaust manifold needs to be formed from highly nickel-containing stainless, for example, which is excellent in heat resistance but is very expensive, because the collecting part and its nearby areas are excessively become high in temperature after the warm-up. This leads to a significant increase in costs of manufacturing exhaust manifolds.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an engine exhaust structure which contributes to a decrease in manufacturing costs of exhaust manifolds while offering sufficient heat-resistant properties of an exhaust manifold, by regulating uniformly the temperatures of individual parts of the exhaust manifold.

An engine exhaust structure in the present invention is provided with a temperature regulating material for regulating a temperature of an exhaust manifold such that individual parts of the exhaust manifold are uniformed in temperature.

In the exhaust structure, the temperature regulating material regulates a temperature of an exhaust manifold in such a manner that individual parts of the exhaust manifold are uniformed in temperature, thereby preventing a local temperature rise in the exhaust manifold. Accordingly, with lower requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from a metal material which is somewhat less heat-resistant but is available at an inexpensive price, resulting in a decrease in costs of manufacturing exhaust manifolds.

In a preferred embodiment, a cover member may be provided to cover the exhaust manifold, and heat transfer materials with high thermal conductivity may be layered as the temperature regulating material on the cover member at an area corresponding to a high-temperature area of the exhaust manifold. In this case, heat from the area of the cover member corresponding to the high-temperature area of the exhaust manifold is efficiently transferred by the heat transfer materials to an outer panel side of the cover member, thereby facilitating heat dissipation from the area to the outside. This retards the increase of an ambient temperature in the surroundings of the high-temperature area of the exhaust manifold, which prevents a local temperature rise in the whole exhaust manifold. By the prevention of local temperature elevation, it is possible to form an exhaust manifold from an inexpensive metal material, which leads to a reduction in manufacturing costs of exhaust manifolds, as stated above. Further, since the exhaust manifold is covered with the cover member, a temperature rise in the whole exhaust manifold is facilitated, a temperature rise in a catalyst in a catalytic converter is accelerated, and the time required for the catalyst to reach an active temperature or more can be shortened to improve the performance of exhaust gas purification.

In another preferred embodiment, a cover member may be provided to cover the exhaust manifold, and heat shield materials may be layered as the temperature regulating material on the cover member at an area corresponding to a low-temperature area of the exhaust manifold. In this case, the heat shield materials prevent the dissipation of heat to the outside from the area of the cover member corresponding to the low-temperature area of the exhaust manifold. This facilitates a raise in an ambient temperature in the surroundings of the low-temperature area of the exhaust manifold, and regulates uniformly the temperatures of the individual parts of the exhaust manifold, thereby preventing a local temperature rise in the whole exhaust manifold. Accordingly, it is possible to form an exhaust manifold from an inexpensive metal material and to reduce the costs of manufacturing exhaust manifolds, as stated above. Further, since the exhaust manifold is covered with the cover member, a temperature rise in the whole exhaust manifold is facilitated, a temperature rise in the catalyst of the catalytic converter is accelerated, and the time required for the catalyst to reach an active temperature or more can be shortened to improve the performance of exhaust gas purification. Moreover, the prevention of heat dissipation from the cover member by the heat shield materials allows the exhaust manifold to be regulated in temperature. This causes the heat of exhaust gases to efficiently act on the catalytic converter, thereby accelerating a temperature rise in the catalyst.

In another preferred embodiment, a cover member may be provided to cover the exhaust manifold, and temperature regulating materials may be layered as the temperature regulating material on the cover member, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold. In this case, the temperature regulating materials facilitate heat dissipation to the outside from the outer panel of the cover member at a high-temperature area, and suppress heat dissipation to the outside from the outer panel of the cover member at a low-temperature area. This regulates uniformly an ambient temperature in the surroundings of the exhaust manifold with further efficiency, regulates uniformly the temperatures of the individual parts of the exhaust manifold, and prevents a local temperature rise in the exhaust manifold. Accordingly, it is possible to form the exhaust manifold from an inexpensive metal material and reduce the costs of manufacturing exhaust manifolds, as stated above. Further, since the exhaust manifold is covered with the cover member, a temperature rise in the whole exhaust manifold is facilitated, a temperature rise in the catalyst in the catalytic converter is accelerated, and the time required for the catalyst to reach an active temperature or more can be shortened to improve the performance of exhaust gas purification.

In another preferred embodiment, a cover member may be provided to the exhaust manifold and a heat dissipation material as the temperature regulating material may coat an outer surface of the area of the cover member corresponding to the high-temperature area of the exhaust manifold. In this case, heat from the area of the cover member corresponding to the high-temperature area of the exhaust manifold is efficiently dissipated to the outside by the heat dissipation material. This suppresses an increase in an ambient temperature in the surroundings of the high-temperature area of the exhaust manifold, regulates uniformly the temperatures of the individual parts of the exhaust manifold, and prevents a local temperature rise in the exhaust manifold. Accordingly, with lower requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from an inexpensive metal material, resulting in a decrease in costs of manufacturing exhaust manifolds, as described above.

In another preferred embodiment, a cover member may be provided to cover the exhaust manifold, and heat transfer materials with high thermal conductivity may be layered as the temperature regulating material between the cover member and the high-temperature area of the exhaust manifold. In this case, heat from the high-temperature area of the exhaust manifold is efficiently transferred to the cover member side by the heat transfer materials, regulates uniformly temperatures of the individual parts of the exhaust manifold, and prevents a local temperature rise in the exhaust manifold. Accordingly, with lower requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from an inexpensive metal material, resulting in a decrease in costs of manufacturing exhaust manifolds, as stated above.

In another preferred embodiment, a cover member may be provided to cover the exhaust manifold, and heat shield materials may be layered as the temperature regulating material on the area of the cover member corresponding to the low-temperature area of the exhaust manifold. In this case, the heat shield materials prevent the dissipation of heat to the outside from the area of the cover member corresponding to the low-temperature area of the exhaust manifold. This facilitates a rise in an ambient temperature in the surroundings of the low-temperature area of the exhaust manifold, and regulates uniformly the temperatures of the individual parts of the exhaust manifold, thereby preventing a local temperature rise in the exhaust manifold. Accordingly, with lower requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from an inexpensive metal material and reduce the costs of manufacturing exhaust manifolds, as stated above.

In another preferred embodiment, a cover member may be provided to cover the exhaust manifold, and temperature regulating materials may be layered as the temperature regulating material between the cover member and the exhaust manifold, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold. In this case, the temperature regulating materials facilitate heat transfer from the exhaust manifold to the cover member at the high-temperature area, and suppress heat transfer from the exhaust manifold to the cover member at the low-temperature area. This regulates uniformly temperatures of the individual parts of the exhaust manifold, and prevents a local temperature rise in the exhaust manifold. Accordingly, with low requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from an inexpensive metal material, resulting in a decrease in costs of manufacturing exhaust manifolds, as stated above.

In another preferred embodiment, the exhaust manifold may have a two-tiered structure with an inner member and an outer member in part or in all, and heat transfer materials with high thermal conductivity may be layered as the temperature regulating material on the high-temperature area of the exhaust manifold between the inner member and the outer member. In this case, at the high-temperature area of the exhaust manifold, the heat transfer materials transfer heat from the inner member to the outer member, facilitate the heat dissipation from the outer member, regulate uniformly the temperatures of the individual parts of the exhaust manifold, and prevent a local temperature rise in the exhaust manifold. Accordingly, with lower requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from an inexpensive metal material, resulting in a decrease in costs of manufacturing exhaust manifolds, as stated above. Further, since the exhaust manifold has a two-tiered structure with the inner member and the outer member, a temperature rise in the whole inner member is facilitated, a temperature rise in the catalyst in the catalytic converter is accelerated, and the time required for the catalyst to reach an active temperature or more can be shortened to improve the performance of exhaust gas purification.

In another preferred embodiment, the exhaust manifold may have a two-tiered structure with an inner member and an outer member in part or in all, and heat shield materials may be layered as the temperature regulating material on the low-temperature area of the exhaust manifold between the inner member and the outer member. In this case, at the low-temperature area of the exhaust manifold, the heat shield materials block heat from the inner member to suppress heat transfer to the outer member, regulate uniformly the temperatures of the individual parts of the exhaust manifold, and prevent a local temperature rise in the exhaust manifold. Accordingly, with lower requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from an inexpensive metal material, resulting in a decrease in costs of manufacturing exhaust manifolds, as stated above. Further, since the exhaust manifold has a two-tiered structure with the inner member and the outer member, a temperature rise in the whole inner member is facilitated, a temperature rise in the catalyst in the catalytic converter is accelerated, and the time required for the catalyst to reach an active temperature or more can be shortened to improve the performance of exhaust gas purification. Moreover, since the prevention of heat dissipation from the inner member by the heat shield materials allows the exhaust manifold to be regulated in temperature, it is possible to cause the heat of exhaust gases to efficiently act on the catalytic converter, thereby accelerating a temperature rise in the catalyst.

In another preferred embodiment, the exhaust manifold may be a two-tiered structure with an inner member and an outer member in part or in all, and temperature regulating materials may be layered as the temperature regulating material between the inner member and the outer member, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold. In this case, the temperature regulating materials facilitate heat dissipation from the inner member to the outer member at the high-temperature area, and suppress heat dissipation from the inner member to the outer member at a low-temperature area. This regulates uniformly the temperatures of the individual parts of the exhaust manifold more effectively, thereby preventing a local temperature rise in the exhaust manifold. Accordingly, with low requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from an inexpensive metal material and reduce the costs of manufacturing exhaust manifolds, as stated above. Further, since the exhaust manifold is covered with the cover member, a temperature rise in the whole exhaust manifold is facilitated, a temperature raise in the catalyst in the catalytic converter is accelerated, and the time required for the catalyst to reach an active temperature or more can be shortened to improve the performance of exhaust gas purification.

In another preferred embodiment, the high-temperature area of the exhaust manifold is an area that contains at least the collecting part. The collecting part of the exhaust manifold becomes high in temperature due to exhaust gases collected from the individual cylinders of an engine. Therefore, when the area containing the collecting part is set as the high-temperature area and the remaining branched area is set as the low-temperature area, the temperatures of the two areas can be regulated uniformly.

According to an engine exhaust structure in the present invention, the temperature regulating materials regulate a temperature of the exhaust manifold in such a manner that temperatures of the individual parts of the exhaust manifold are uniformed, thereby preventing a local temperature rise in the exhaust manifold. Accordingly, with lower requirements for the heat-resistant properties of an exhaust manifold, it is possible to form an exhaust manifold from a metal material which is somewhat less heat-resistant but is available at an inexpensive price, resulting in a decrease in costs of manufacturing exhaust manifolds.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of main components of an engine exhaust structure;

FIG. 2 is a front view of an exhaust manifold;

FIG. 3 is a cross-sectional view of the exhaust manifold in FIG. 2 with a cover member and without temperature regulating materials, taken along line III-III;

FIG. 4 is a view of the exhaust manifold with temperature regulating materials, which is equivalent to FIG. 3; and

FIG. 5 is a front view of an exhaust manifold of another configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, a basic configuration of an automobile engine exhaust structure will be discussed.

An engine 10 shown in FIG. 1 is an automobile inline four-cylinder engine. At a middle portion of an exhaust passage in the engine 10, an exhaust manifold 11, a catalytic converter 12 and a muffler (not shown) are intervened in this order from the upstream side. Exhaust gases from the engine 10 are collected in the exhaust manifold 11, purified through the catalytic converter 12, muffed by the muffler, and then emitted to the outside.

As shown in FIGS. 1 to 3, the exhaust manifold 11 includes four branched pipes 15 connected respectively to four exhaust ports 14 formed in a cylinder head 13, a collecting pipe 16 aggregating downstream ends of the four branched pipes 15, and outer members 17 each covering a pair of the adjacent branched pipes 15.

A first tubular clearance 18 of 1.0 to 4.0 mm in thickness, for example, is provided between the outer members 17 and the branched pipes 15 along the almost full lengths thereof. Each of the outer members 17 is formed from an upper surface plate 17U and a lower surface plate 17L. The outer member 17 is assembled in such a manner as to surround the branched pipe 15 by combining the upper surface plate 17U and the lower surface plate 17L with the branched pipes 15 inside thereof and welding the two plates together in a butt joint. Provided at an upstream end of each of the outer members 17 is a bifurcated part 17a that is branched into two. Upstream ends of the branched pipes 15 are individually fitted into the bifurcated part 17a of the outer member 17. Provided at an upstream end of the exhaust manifold 11 is an overlaid part 17b in which the upstream end of the bifurcated part 17a is reduced in diameter and overlaid on the upstream end of the branched pipe 15. An attachment sheet 19 is provided at the upstream end of the exhaust manifold 11 for attachment to the cylinder head 13. The attachment sheet 19 is provided with four through-holes 20 corresponding to the exhaust ports 14. By inserting and welding the overlaid parts 17b individually into the four through-holes 20, the four branched pipes 15 and the two outer members 17 are combined via the attachment sheet 19. A downstream end of the outer member 17 is welded into the collecting pipe 16. A spacer member 21 for preventing vibrations of the branched pipe 15 is intervened between the downstream end of the branched pipe 15 and the downstream end of the outer member 17. In addition, a flange member 22 is welded into a downstream end of the collecting pipe 16 for connection to an exhaust pipe on the downstream side.

Provided at both upper and lower sides of the exhaust manifold 11 are cover members 25 for blocking noise and heat from the exhaust manifold 11. The upper and lower cover members 25 are each fixed to the exhaust manifold 11 by means of a bracket member 26 provided on the exhaust manifold 11. A second clearance 27 is provided between the exhaust manifold 11 and the cover member 25. However, the lower cover member 25 may be eliminated.

The upper and lower cover members 25 each include an outer panel 28 disposed on the outer surface side and an inner panel 29 disposed on the exhaust manifold 11 side. A third clearance 30 is provided between the outer panel 28 and the inner panel 29. In the third clearance 30, sound-absorbing materials or temperature regulating materials 31 to be discussed below are layered in close contact with the outer panel 28 and the inner panel 29. The outer panel 28 and the inner panel 29 are made by press-molding metal plates of stainless steel or the like. However, the inner panel 29 may be formed from general-purpose punching metal or mesh for higher sound-absorbing quality.

The present invention is characterized in that, in an exhaust structure of the engine 10 formed basically as described above, temperature regulating materials are disposed as shown in FIG. 4, for example, for regulating uniformly temperatures of the individual parts of the exhaust manifold 11.

The exhaust manifold 11 becomes higher in temperature from the cylinder head 13 side to the collecting pipe 16 side. It is impossible to specify a boundary B between the low-temperature area LT and the high-temperature area HT as shown in FIG. 4. However, assuming that a pipe length between the upstream end of the branched pipe 15 and the boundary B is L1, and that a pipe length between the boundary B and the downstream end of the collecting pipe 16 is L2, the boundary B can be set within a range that L1/(L1+L2) becomes 20 to 35%.

As the temperature regulating material 31, a heat transfer material 31A is tightly arranged in the high-temperature area(s) HT of one or more selected from the first clearance 18, the second clearance 27 and the third clearance 30. In addition, a heat shield material 31B is tightly arranged in the low-temperature area(s) LT of one or more selected from the first clearance 18, the second clearance 27 and the third clearance 30. Further, a heat dissipation material 31C may coat the outer surface of at least one of the high-temperature area HT of the exhaust manifold 11 and the high-temperature area HT of the cover member 25. However, the first clearance 18 between the branched pipe 15 and the outer member 17 acts as a heat insulating space, and therefore the heat shield material 31B for the low-temperature area LT may be eliminated. Additionally, if the heat transfer material 31A is provided in the high-temperature area HT of the second clearance 27, a coating of the heat dissipation material 31C to the outer surface of the high-temperature area HT of the exhaust manifold 11 may be eliminated. Further, if the heat transfer material 31A or the heat shield material 31B is not provided in the third clearance 30, a sound-absorbing material is to be provided in the location instead. The temperature regulating material 31 is only needed to be provided such that temperatures of the individual parts of the exhaust manifold 11, in particular, temperatures of the branched pipes 15 and the collecting pipe 16 are uniformly regulated. The temperature regulating material 31 may be provided to at least one of the above-described areas.

In particular, as shown in FIG. 4, the heat transfer materials 31A are provided to the high-temperature area HT of the first clearance 18 and the high-temperature area HT of the second clearance 27, the heat dissipation material 31C coats the outer surface of the cover member 25, and the heat shield materials 31B are provided to the low-temperature area LT of the second clearance 27. Accordingly, the heat transfer materials 31A transfer efficiently heat from the high-temperature area HT of the exhaust manifold 11 to the cover member 25, and then the heat dissipation material 31C dissipates heat from the outer surface of the cover member 25 to the outside. Accordingly, it is possible to prevent excessively high temperatures of the downstream portions of the branched pipes 15 and the collecting pipe 16 with most strict requirements for heat resistance, and to improve the heat-retaining properties of the upstream sides of the branched pipes 15 for accelerating a temperature rise. This allows the branched pipes 15 and the collecting pipe 16 to be regulated in temperature uniformly as a whole.

The heat shield material 31B may use preferably a mat formed from inorganic fibers such as glass fibers, rock wool fibers, ceramic fibers or potassium titanate fibers, or organic fibers such as poly-phenylene-benzobisoxazole (PBO) fibers.

The heat transfer material 31A may use a mat formed from metal fibers such as stainless fibers, steel fibers, copper fibers, brass fibers, bronze fibers or aluminum fibers, or carbon fibers such as pitch-based carbon fibers or PAN-based carbon fibers, or metal plating fibers. In addition, to seal the first clearance 18 between the outer member 17 and the branched pipe 15 and the third clearance 30 between the outer panel 28 and inner panel 29 of the cover member 25, these clearances 18 and 30 may be filled with one or a mixture of any combination of carbon powder, graphitic powder, aluminum powder, copper powder, brass powder, and bronze powder. Further, any of the above-mentioned fiber materials may support any of the above-mentioned powders when it is formed into a mat.

The heat dissipation material 31C may appropriately use a ceramic-based heat dissipation coating material, for example, Cooltech (made by Okitsumo Incorporated). Alternatively, a silicon- or acryl-based heat dissipation sheet may be stuck as the heat dissipation material 31C.

The temperature regulating materials 31 to be attached to different areas may be formed from a material of the same kind or from materials of different kinds. In this embodiment, the exhaust manifold 11 is divided into two segments of low-temperature area LT and high-temperature area HT. Alternatively, the exhaust manifold 11 may be divided into three segments of high-temperature area, medium-temperature area and low-temperature area, or more segments, such that the individual parts of the exhaust manifold 11 are uniform in temperature. Further, the temperature regulating material 31 may change gradually or continuously in heat shield properties and/or heat transfer properties to regulate a temperature of the exhaust manifold 11 in a more detailed manner.

The present invention is also applicable to an exhaust structure for the engine 10 without the outer member 17 and an exhaust structure for the engine 10 without the cover member 25. For an exhaust structure without the outer member 17, the heat shield material 31B or heat transfer material 31A is disposed in at least one of the second clearance 27 between the cover member 25 and the branched pipe 15 and the third clearance 30 between the outer panel 28 and inner panel 29 of the cover member 25. Alternatively, the heat dissipation material 31C coats the outer surfaces of the branched pipe 15 and collecting pipe 16, or the outer surface of the cover member 25 at the high-temperature area HT. For an exhaust structure without the cover member 25, the heat shield material 31B or the heat transfer material 31A is disposed in the first clearance 18 between the outer member 17 and the branched pipe 15, the heat dissipation material 31C is disposed on the outer surfaces of the outer member 17 and collecting pipe 16. Further, if the cover member 25 is a cover member without the third clearance 30 formed between the outer panel 28 and the inner panel 29, or if the cover member 25 is a cover member formed from a single panel, the heat shield material 31B or the heat transfer material 31A is disposed in the first clearance 18 between the outer member 17 and the branched pipe 15 and is disposed in the second clearance 27 between the cover member and the branched pipe 15, and the heat dissipation material 31C coats the outer surface of the exhaust manifold 11 or the outer surface of the cover member at the high-temperature area HT.

The present invention is applicable to any configuration of the exhaust manifold 11. For example, as shown in FIG. 5, the present invention may be applied to an exhaust manifold 41 including four branched pipes 40 of different lengths. Additionally, the present invention can be applied to an exhaust manifold with the outer member 17 surrounding the individual branched pipes 15. For provision of such an outer member surrounding the individual branched pipes 15, the outer member may be formed by welding the upper surface plate and the lower surface plate together, or the outer member 17 formed from a pipe member larger in diameter than the branched pipe 15 may be attached to the outside of the branched pipe 15. Moreover, the present invention can be applied to exhaust structures for inline multi-cylinder engines and V-type multi-cylinder engines as well as those for the inline four-cylinder engine 10.

Claims

1. An engine exhaust structure provided with a temperature regulating material for regulating a temperature of an exhaust manifold such that individual parts of the exhaust manifold are uniformed in temperature.

2. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and heat transfer materials with high thermal conductivity are layered as the temperature regulating material on the cover member at an area corresponding to a high-temperature area of the exhaust manifold.

3. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and heat shield materials are layered as the temperature regulating material on the cover member at an area corresponding to a low-temperature area of the exhaust manifold.

4. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and temperature regulating materials are layered as the temperature regulating material on the cover member, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold.

5. The engine exhaust structure according to claim 1, wherein a cover member is provided to the exhaust manifold and a heat dissipation material as the temperature regulating material coats an outer surface of the area of the cover member corresponding to the high-temperature area of the exhaust manifold.

6. The engine exhaust structure according to claim 1, wherein a cover is provided to cover the exhaust manifold, and heat transfer materials with high thermal conductivity are layered as the temperature regulating material between the cover member and the high-temperature area of the exhaust manifold.

7. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and heat shield materials are layered as the temperature regulating material on an area of the cover member corresponding to a low-temperature area of the exhaust manifold.

8. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and temperature regulating materials are layered as the temperature regulating material between the cover member and the exhaust manifold, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold.

9. The engine exhaust structure according to claim 1, wherein the exhaust manifold has a two-tiered structure with an inner member and an outer member in part or in all, and heat transfer materials with high thermal conductivity are layered as the temperature regulating material on the high-temperature area of the exhaust manifold between the inner member and the outer member.

10. The engine exhaust structure according to claim 1, wherein the exhaust manifold has a two-tiered structure with an inner member and an outer member in part or in all, and heat shield materials are layered as the temperature regulating material on the low-temperature area of the exhaust manifold between the inner member and the outer member.

11. The engine exhaust structure according to claim 1, wherein the exhaust manifold has a two-tiered structure with an inner member and an outer member in part or in all, and temperature regulating materials are layered as the temperature regulating material between the inner member and the outer member, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold.

12. The engine exhaust structure according to claim 1, wherein the high-temperature area of the exhaust manifold is an area that contains at least the collecting part.