JP3497392B2 - Heated exhaust pipe for engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin inner pipe and a thick outer pipe which are arranged inside and outside of a tubular heat insulating space. The present invention relates to a warmed exhaust pipe for an engine, wherein the exhaust pipes are fixed to each other and the other end of an inner pipe is slidably supported on an inner peripheral surface of an outer pipe. 2. Description of the Related Art Such a heat-insulating exhaust pipe for an engine is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-189681.
Already known. [0003] In such a warmed exhaust pipe for an engine, the inner pipe that directly contacts the exhaust gas of the engine and the outer pipe that directly touches the outside air have a particularly large thermal expansion amount in the axial direction. The inner pipe expands more in the axial direction than the outer pipe, and the difference in the amount of expansion is absorbed by sliding between the other ends of the inner pipe and the outer pipe. In addition, since the inner tube is thin, the heat mass is small, it is heated by the high-temperature exhaust gas flowing inside it, and the temperature rises quickly. It guides to the downstream exhaust purification device and contributes to the promotion of its activation. By the way, during the warm-up operation of the engine, it is necessary to enhance the heat retention of the inner pipe by the heat insulating space to promote the activation of the exhaust gas purification device. After the warm-up, the exhaust gas passing through the inner pipe is required. Properly radiating the heat of the inner tube is effective in preventing overheating of the inner tube and ensuring its durability. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has a simple structure, which enhances the heat retention of an inner pipe by an adiabatic space during warm-up operation of an engine, and passes through the inner pipe after warm-up. The heat release of exhaust gas can be promoted appropriately.
An object of the present invention is to provide a warmed exhaust pipe for the engine. [0006] In order to achieve the above object, the present invention provides a thin inner pipe and a thick outer pipe which are arranged inside and outside with a tubular heat insulating space interposed therebetween. With one end fixed to each other, the other end of the inner pipe is slidably supported on the inner peripheral surface of the outer pipe, in a warmed exhaust pipe for an engine, facing the other end of the inner pipe, the gap between it and integrally connected to the outer tube a gap adjusting step portion to narrow in response to the inner tube thermally expands in the larger axially than the outer tube, the gap adjustment
One end of the nodal step is fixed to the outer peripheral surface of the other end of the outer tube
One piece of the second inner tube is formed integrally with the second inner tube.
At the end, the second inner side of the second heat insulating space is sandwiched.
One end of a second outer tube disposed outside the tube is fixed . According to this feature, during warm-up of the engine,
Since the inner tube having a small thickness and a small heat mass is quickly heated by exhaust gas passing through the inside, the inner tube expands more in the axial direction than the outer tube, and the difference in the amount of thermal expansion between the inner tube and the outer tube in the axial direction is reduced. Absorbed. Such a difference in the amount of thermal expansion between the inner pipe and the outer pipe in the axial direction is the largest during the warm-up operation of the engine, so that the gap between the other end face of the inner pipe and the gap adjusting step facing the inner pipe has this difference. Sometimes narrowed most. As a result, the exhaust gas that has passed through the inner pipe is minimized from entering the heat insulating space around the outer circumference of the inner pipe due to the narrowed gap, so that the heat insulating effect of the heat insulating space on the inner pipe is reliably exhibited. After the engine is warmed up, the outer pipe is also sufficiently heated by the radiant heat from the inner pipe, and the difference in the amount of thermal expansion between the inner pipe and the outer pipe is reduced. The gap with the gap adjusting step portion is enlarged. as a result,
Part of the exhaust gas that has passed through the inner pipe relatively easily enters the heat insulating space around the inner pipe from the gap, and the heat release of the exhaust gas is appropriately promoted, so that overheating of the inner pipe is avoided. Embodiments of the present invention will be described below based on embodiments of the present invention shown in the accompanying drawings. FIG. 1 is a side view showing an exhaust manifold provided with a heat retaining type exhaust pipe according to the present invention when the exhaust manifold is attached to an engine.
FIG. 2 is a perspective view of the exhaust manifold, FIG. 3 is a partially longitudinal front view of the exhaust manifold, FIG. 4 is an enlarged view of a part of FIG. 3 (engine stopped state), and FIG. , FIG. 6 is an explanatory view corresponding to FIG. 4 after the engine warm-up operation, and FIG. 7 is an explanatory view corresponding to FIG.
8 is a sectional view taken along line 7-7 (in an engine stopped state), FIG. 8 is an explanatory diagram of the operation corresponding to FIG. 7 during the engine warm-up operation, and FIG. 9 corresponds to FIG. 7 after the engine warm-up operation. FIG. 10 is a sectional view taken along line 10-10 of FIG. [0011] First, in FIGS. 1 to 3, 4 to the front surface of the cylinder head 1 of cylinder engine E, and then the exhaust port _{21 to 24} is the opening of the four corresponding to the cylinders, these exhaust ports 2 insulation type exhaust manifold M to induce exhaust gas discharged from 21 _{to 24} is mounted by a plurality of stud bolts 3 and nuts 4 on the cylinder head 1. The exhaust manifold M, the four exhaust ports 2 ₁ to 2
₄ includes four exhaust single pipe 5 ₁ to 5 ₄ for communicating individually upper end, the first to fourth from the upstream end left them in FIG. 3
I will call it a single exhaust pipe. [0012] The first to the first to the upper flange 7 is connected to the fourth upstream end of the exhaust monotube 5 ₁ to 5 _4, the downstream end of the second and third exhaust monotube 5 _2, 5 ₃ exhaust collecting pipe ₆₁ is connected, the second to the downstream end of the first and fourth exhaust monotube 5 ₁ 5 ₄
Exhaust collecting pipe 6 ₂ are connected. A lower flange 8 is connected to downstream ends of the first and second exhaust manifolds 6 ₁ , 6 ₂ . The upper flange 7 is provided with the stud bolt 3.
And a nut 4 fixed to a vertical mounting surface formed on the front surface of the cylinder head 1. Each exhaust single pipes 5 ₁ -
5 _4, extends from the upper flange 7 in the front bend portion 9 bent in the range of approximately 90 ° downward is formed in the middle portion, which lower flange 8 by is arranged downward. An intermediate exhaust pipe 21 connected to a common catalytic converter (exhaust gas purification device) (not shown) arranged under the floor of the vehicle is connected to the lower flange 8. The lower flange 8
, The above-mentioned catalytic converter can be directly connected. [0014] Each exhaust monotube 5 ₁ to 5 _4, made of an inner monotube 10 and the outer collecting pipe 11 disposed inside and outside double,
A cylindrical heat insulating space 1 is provided between the inner and outer collecting pipes 10 and 11.
2 are formed. The inner single pipe 10 is made of a thin stainless steel pipe, and the outer collecting pipe 11 is also made of a stainless steel pipe, but is thicker than the inner single pipe 10. As shown in FIG. 1, the upstream end of the outer collecting pipe 11 is reduced in diameter so as to fit on the outer peripheral surface of the upstream end of the inner single pipe 10, and their upstream ends are formed in the upper part. Flange 7
Of, connected to corresponding exhaust ports ₂₁ to ₂₄ through-holes 13 ₁
To 13 together are fitted to _4, the through hole _131-134
Is fixed by welding to the inner peripheral surface. As shown in FIG. 3 and FIG.
An annular projection 14 is formed on the outer peripheral surface of the downstream end of the inner tube 10, and the downstream end of the inner single pipe 10 is slidably supported on the inner peripheral surface of the downstream end of the outer collecting pipe 11 via the projection 14. You. In FIGS. 3, 4, 7 and 10, each of the exhaust manifolds 6 ₁ and 6 ₂ comprises an inner manifold 15 and an outer manifold 16 arranged in an inner and outer doubly. A heat insulating space 17 is also formed between the collecting pipes 15 and 16. At the upstream end of the inner collecting pipe 15, an inner forked pipe 1 is provided.
8 and 18 are formed, into which the downstream ends of the two corresponding outer collecting pipes 11 and 11 are fitted. The inner collecting pipe 15 is composed of a pair of inner collecting pipe halves 15 made of a thin stainless steel plate divided in the radial direction.
A and 15b are formed by overlapping opposing ends and welding the entire overlapping end. The outer collecting pipe 16 is also formed by overlapping opposing ends of a pair of outer collecting pipe halves 16a and 16b made of a stainless steel plate and welding the entire overlapped portion. Is thicker than the inner collecting pipe 15. At the upstream end of the outer collecting pipe 16, outer bifurcated pipes 19, 19 respectively covering the inner bifurcated pipes 18, 18 are formed. The distal ends of the outer forked pipes 19, 19 are connected to the inner forked pipes 18, 18, respectively.
Are fitted to the outer peripheral surfaces of the downstream ends of the corresponding two outer collecting pipes 11, 11 by welding. The lower flange 8 is fixed to the downstream end of the outer collecting pipe 16 by welding. In addition, the outer collecting pipe 16
An annular split mesh member 20 formed by knitting a stainless steel wire is attached to the inner peripheral surface of the downstream end portion by welding, and the inner collecting pipe 15 is attached to the inner peripheral surface of the mesh member 20.
Are slidably fitted at the downstream end. Thus, the downstream end of the inner collecting pipe 15 is slidably supported by the outer collecting pipe 16 via the mesh member 20. As shown in FIGS. 3 and 4, the upstream end of the inner collector pipe 15, the inner single tube 10 across the lower opening of the heat insulation space 12 of the exhaust monotube 5 ₁ to 5 ₄ A gap adjusting step 23 facing the downstream end face of the first member is integrally and continuously provided.
The gap adjusting step portion 23 defines a predetermined gap 25 between the inner single pipe 10 and the downstream end face thereof.
The inner pipe 10 is configured to be throttled as the inner single pipe 10 thermally expands more in the axial direction than the outer collecting pipe 16. [0022] As shown in FIG. 7, the lower flange 8, gap adjustment facing the downstream end face of the inner collecting pipe 15 across the lower opening of the exhaust collecting pipe 6 _and 62 of the heat insulation space 17 The step portion 24 is integrally connected. The gap adjusting step portion 24 defines a predetermined gap 26 between the inner collecting pipe 15 and the downstream end face. The gap 26 is formed such that the inner single pipe 10 is larger than the outer collecting pipe 16 in the axial direction. It is squeezed according to thermal expansion. [0023] In the above, the exhaust monotube 5 ₁ to 5 ₄ and the exhaust collecting pipe 6 _and 62 respectively correspond to the insulation type exhaust pipe of the present invention, also the inner monotube 10 and the inner collector pipe 15 each The outer single pipe 11 and the outer collecting pipe 16 correspond to the inner pipe of the present invention, respectively, and correspond to the outer pipe of the present invention, respectively. Next, the operation of this embodiment will be described. [0025] During operation of the engine E, an exhaust port 2 ₁ of the exhaust gas is four, ₂ 2, 2 _4, 2 ₃ from the first exhaust monotube 5 _1,
Second exhaust monotube 5 _2, fourth exhaust monotube 5 _4, the third exhaust monotube 5
_It is sequentially discharged to ₃ . The exhaust gas which has passed through the first and fourth exhaust monotube 5 _1, 5 ₄ merged in the first exhaust collecting pipe _61, which has passed through the second and third exhaust monotube 5 _2, 5 ₃ and the second merge at an exhaust merging pipe 6 _2, then the exhaust gas is guided to a common catalytic converter (not shown) while being further joined at the intermediate exhaust pipe 21, it is purified. By the way, the exhaust monotube 5 ₁ to 5 ₄ are composed of an inner monotube 10 and outer collector pipes 11 of the inner and outer double arrangement, inside the single tube 10 is formed into a thin, inner and outer sets A heat insulating space 12 is formed between the pipes 10 and 11, and each of the exhaust collecting pipes 6 ₁ and 6 ₂ is also composed of an inner collecting pipe 15 and an outer collecting pipe 16 arranged in an inner and outer double arrangement. Since the heat insulating space 17 is formed between the inner and outer collecting pipes 15 and 16 while being formed thin, the inner single pipe 10 and the inner collecting pipe 1 having a small heat mass are formed.
5 is heated by the high-temperature exhaust gas flowing through the inside thereof and quickly rises in temperature, which is kept insulated by the heat insulating spaces 12 and 17. Therefore, it is possible to guide the subsequent exhaust gas to the catalytic converter while suppressing the temperature decrease thereof, to promote its activation, and to increase the purification efficiency of the exhaust gas. [0027] Meanwhile, in the exhaust monotube 5 ₁ to 5 _4, inner single tube 10 in direct contact with the exhaust gas is thermally expanded to increase the axial direction than the outer collector pipes 11 in direct contact with the outside air, its thermal expansion Accordingly, the annular projections 14 on the outer peripheral surface of the downstream end portion of the inner single pipe 10 slide with respect to the inner peripheral surface of the outer collecting pipe 11 that supports them, and the thermal expansion in the axial direction of the inner and outer collecting pipes 10 and 11 occurs. The difference in volume is absorbed. The inner single pipe 10 has an upstream end fixed to the outer collecting pipe 11 and a downstream end slidably supported by the outer collecting pipe 11, so that the inner single pipe 10 is supported in a double-supported manner. In other words, the support can be stabilized, and the generation of vibration noise can be prevented. On the other hand, in each of the exhaust manifolds 6 ₁ and 6 ₂ , thermal expansion in the axial direction of the inner manifold 15 is larger than that of the outer manifold 16. The side end slides with respect to the mesh member 20 supported by the outer collecting pipe 16, and the inner and outer collecting pipes 1
The difference in the amount of thermal expansion in the axial direction of 5 and 16 is absorbed. [0030] Thus, in thermal insulation type exhaust manifold M, the downstream end of each exhaust monotube 5 ₁ to 5 ₄ a sliding portion for absorbing the difference in axial thermal expansion of the inner and outer double wall and the exhaust by providing divided into the downstream end of the collecting pipe 6 _and 62, it is possible to set a sliding stroke in the sliding portions small, sliding process, the inclination to the sliding portion mutually Is less likely to occur, and it is possible to effectively prevent the occurrence of thermal distortion in each part of the exhaust manifold M, and to improve the durability thereof. By the way, the downstream end face of the inner single pipe 10
The gap 25 between the gap adjusting step 23 formed on the inner collecting pipe 15 and the gap 26 between the downstream end face of the inner collecting pipe 15 and the gap adjusting step 24 formed on the lower flange 8 are:
The largest in the cold state where the operation of the engine is stopped (FIG. 4
And FIG. 7). However, when the engine is started and the warm-up operation is started, the inner single pipe 10 and the inner collecting pipe 15 are thin and have a relatively small heat mass, and are in direct contact with the exhaust gas, and the outer collecting pipe 16 and the outer collecting pipe 16 are thick. Since the meat has a relatively large heat mass and is in direct contact with the outside air, the inner single pipe 10 and the inner collecting pipe 15 thermally expand in the axial direction particularly larger than the outer collecting pipe 16 and the outer collecting pipe 16. Accordingly, the downstream end faces of the inner single pipe 10 and the inner collecting pipe 15 approach the gap adjusting step portions 23 and 24, respectively, so that the gaps 25 and 26 are reduced to the minimum (see FIGS. 5 and 8). ). As a result, the inner single pipe 10 and the inner collecting pipe 1
Exhaust gas passing through each of the narrowed gaps 2
Due to 5, 26, entry into the heat insulating spaces 12, 17 on the outer periphery of the inner single pipe 10 and the inner collecting pipe 15 is suppressed as much as possible. Is reliably exerted, the reduction of exhaust gas can be effectively suppressed, the activation of the downstream catalytic converter can be promoted, and the exhaust gas purification efficiency can be improved. After the engine is warmed up, the outer collecting pipe 16 and the outer collecting pipe 16 are also heated by radiant heat from the inner single pipe 10 and the outer collecting pipe 16, and the inner single pipe 10 and the outer collecting pipe 1 are heated.
6. Since the difference in the amount of thermal expansion between the inner collecting pipe 15 and the outer collecting pipe 16 is reduced, the gap adjusting steps 23 and 24 are separated from the downstream end faces of the inner single pipe 10 and the inner collecting pipe 15. To enlarge the gaps 25 and 26 (see FIGS. 6 and 9). As a result, a part of the exhaust gas passing through the inner single pipe 10 and the inner collecting pipe 15 is separated by the gaps 25 and 26.
Heat insulation space 1 around the inner single pipe 10 and the inner collecting pipe 15
The inner pipes 2 and 17 are relatively easily introduced, and the heat release of the exhaust gas is appropriately promoted. Therefore, overheating of the inner single pipe 10 and the inner collecting pipe 15 is avoided and their durability is secured. Although the embodiments of the present invention have been described in detail, various design changes can be made in the present invention without departing from the gist thereof. As described above, according to the present invention, one ends of a thin inner pipe and a thick outer pipe which are arranged inside and outside doubly with a tubular heat insulating space therebetween are fixed to each other. At the same time, in a warmed exhaust pipe for an engine, in which the other end of the inner pipe is slidably supported on the inner peripheral surface of the outer pipe, a gap with the other end face of the inner pipe is formed inside the exhaust pipe. A gap adjustment step that narrows as the pipe thermally expands in the axial direction larger than the outer pipe is integrally connected to the outer pipe, so during warm-up operation of the engine,
By utilizing the large difference in the amount of thermal expansion between the inner pipe and the outer pipe in the axial direction, by narrowing the gap, the exhaust gas passing through the inner pipe is prevented from entering the heat-insulated space, and the heat-insulating effect of the heat-insulated space on the inner pipe. , The activation of the exhaust gas purification device located downstream can be promoted, and after the engine is warmed up, the difference in the amount of thermal expansion between the inner pipe and the outer pipe is reduced to enlarge the gap, By allowing a part of the exhaust gas to enter the heat-insulating space through the gap and appropriately promoting heat radiation of the exhaust gas, overheating of the inner pipe can be avoided and its durability can be ensured. Further, no special actuator is required for adjusting the gap, and the structure is extremely simple. The gap adjusting step is provided at the other end of the outer tube.
Formed integrally with the second inner tube whose one end is fixed to the outer peripheral surface
And one end of the second inner tube is provided with a cylindrical second heat insulating member.
A second outer tube disposed outside the second inner tube across a space;
One end of the side tube is fixed .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing an exhaust manifold provided with a heat-retaining exhaust pipe of the present invention in a state where the exhaust manifold is attached to an engine. FIG. 2 is a perspective view of the exhaust manifold. FIG. 3 is a partial vertical front view of the exhaust manifold. FIG. 4 is an enlarged view of a part 4 in FIG. 3 (engine operation stopped state). FIG. 5 is an operation explanatory view corresponding to FIG. 4 during an engine warm-up operation; FIG. 6 is an operation explanatory view corresponding to FIG. 4 after an engine warm-up operation; FIG. 7 is a sectional view taken along the line 7-7 in FIG. 1 (engine stopped state). FIG. 8 is an operation explanatory view corresponding to FIG. 7 during an engine warm-up operation; FIG. 9 is an operation explanatory view corresponding to FIG. 7 after an engine warm-up operation; FIG. 10 is a sectional view taken along line 10-10 of FIG. 7; As exhaust monotube 6 _1, 6 ₂ ... insulation type exhaust pipe as [Reference Numerals] E · · · · · · engine M · · · · · · exhaust manifold 5 ₁ to 5 ₄ ... insulation-type exhaust pipe The exhaust collecting pipe 10 of the inner pipe 11 as the inner pipe. The outer single pipe 12 as the outer pipe. The heat insulating space 15 as the second inner pipe. outer collector pipes 17 ----- second insulation space 2 3 as an outer tube of the inner collector pipe 16 ----- second ----- gap adjusting step part 2 5 ----- gap

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Hashimoto 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside of Honda R & D Co., Ltd. (72) Kazuo Ishii 1-4-1 Chuo, Wako-shi, Saitama Stock Koichi Fujimori, inventor of Honda R & D Co., Ltd. (1-2) 1-4-1, Chuo, Wako-shi, Saitama, Japan Stock Company Seiji Kato (72) Inventor of Honda R & D Co., Ltd. 1-4-1, Chuo, Wako, Saitama Co., Ltd. Inside the Technical Research Institute (72) Inventor Kiyotaka Oshio 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda Technical Research Institute Co., Ltd. (56) References JP-A-8-121158 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) F01N 7/08 F01N 7/10 F01N 7/14

Claims (1)

(57) Patent Claims 1. A tubular insulating space (1 2) interposed therebetween thin inner tube arranged inside and outside double (1 0) and the outer tube of the thick (1 1 ) Are fixed to each other and the inner tube (1)
The other end of the 0) becomes slidably is supported on the inner peripheral surface of the outer tube (1 1), the thermal insulation type exhaust pipe for an engine, so as to face the other end surface of the inner tube (1 0), the same Gap (2
5), integrally continuously provided inner tube (1 0) is gap adjusting step portion to narrow in response to thermal expansion in the larger axially than the outer tube (1 1) and (2 3) in the outer tube (1 1) and, the gap adjusting step portion (23), the other end portion of the outer tube (11)
A second inner tube (1) having one end fitted and fixed to the outer peripheral surface
5) and formed integrally with one of its second inner tubes (15).
At the end, the second heat insulating space (17) is sandwiched.
A second outer tube (1) disposed outside the second inner tube (15).
(6) A heat retaining type exhaust pipe for an engine , wherein one end of the exhaust pipe is fixed .