JPH0828256A - Exhaust double pipe - Google Patents

Abstract

PURPOSE:To reduce cost and increase durability through simple constitution and to perform cooling of exhaust gas during high load running. CONSTITUTION:An exhaust double pipe comprises a gas inflow port 18 which is formed in the wall surface of an inner pipe 15 in the vicinity of an exhaust gas inflow port and through which exhaust gas flows in a gap 16; an expansion part 15a arranged on the exhaust gas outflow port side of the inner pipe 15 and increasing an outside diameter toward the exhaust gas outflow port side; and an expansion part 13a arranged on the exhaust gas outflow port side of an outer pipe 13 and increasing an inside diameter toward the exhaust gas outflow port side. Thus, when an exhaust gas temperature is low and the inner pipe 15 is contacted, the expansion part 15a and the outer pipe 13 are forced into contact with each other to close a part of the gap 16. When an exhaust gas temperature is high and the inner pipe 15 is elongated, the expansion part 15a and the outer pipe 13 are separated away from each other to release a part of closed gap 16.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】この発明は，エンジンの排気ガス
温を昇温させて排気エミッション性能を向上させる排気
二重管に関し，特に，高負荷走行条件下において排気管
出口温度の低下を図った排気二重管に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust double pipe for raising exhaust gas temperature of an engine to improve exhaust emission performance, and particularly to reduce the exhaust pipe outlet temperature under high load running conditions. Regarding exhaust double pipe.

【０００２】[0002]

【従来の技術】一般に，車両用エンジンから排出される
排気ガスは，排気マンホールで集合し，排気管により触
媒に導かれ，触媒によって排気ガス中の有害成分が除去
される。このとき，排気ガスと触媒が充分に反応するた
めには，触媒本体の温度が所定の活性温度まで昇温して
いる必要がある。ところが，エンジンの低温始動時のよ
うに排気ガスの温度が低い場合は，触媒の温度も活性温
度以下になって化学変化が起こらず，排気ガス内未燃焼
成分（有害成分）を充分に除去できない状況が発生す
る。2. Description of the Related Art Generally, exhaust gas discharged from a vehicle engine is collected in an exhaust manhole and guided to a catalyst by an exhaust pipe, and the catalyst removes harmful components from the exhaust gas. At this time, in order for the exhaust gas and the catalyst to sufficiently react with each other, the temperature of the catalyst body needs to be raised to a predetermined activation temperature. However, when the temperature of the exhaust gas is low, such as when starting the engine at a low temperature, the temperature of the catalyst also falls below the activation temperature and chemical changes do not occur, and unburned components (toxic components) in the exhaust gas cannot be sufficiently removed. The situation arises.

【０００３】これを解決するためには，高価な大容量の
触媒を使用したり，触媒を排気系上流の排気マニホール
ド直下に装着することが提案されているが，大容量の触
媒を使用した場合には，コストが上昇するという不具合
が発生し，また，排気マニホールド直下に触媒を装着し
た場合には，周囲の部品に対する熱的悪影響を回避する
ために，遮熱板の大型化，冷却ファンの大容量化等の対
処を行う必要があるという不具合が発生する。In order to solve this, it has been proposed to use an expensive large-capacity catalyst or to mount the catalyst just below the exhaust manifold upstream of the exhaust system. However, when a large-capacity catalyst is used However, if the catalyst is installed directly below the exhaust manifold, in order to avoid adverse thermal effects on surrounding parts, the heat shield plate must be large and the cooling fan There is a problem that it is necessary to take measures such as increasing the capacity.

【０００４】このため，高価な大容量の触媒を使用した
り，触媒を排気系上流の排気マニホールド直下に装着す
ることに代えて，排気管により排気ガス温度を昇温して
触媒の活性化を高める方法として，例えば，排気管を外
管と内管から成る二重管で構成し，外管によって構造上
の強度を保ち，内管は熱容量を小さくし，かつ，外部と
の熱的接触を断つように形成した排気二重管が提案され
ている。この排気二重管によると，外管と内管の間の間
隙を有効に利用することで，排気ガス温度を適正に調整
できることが期待される。Therefore, instead of using an expensive large-capacity catalyst or mounting the catalyst directly below the exhaust manifold upstream of the exhaust system, the exhaust gas temperature is raised by an exhaust pipe to activate the catalyst. As a method of increasing, for example, the exhaust pipe is composed of a double pipe consisting of an outer pipe and an inner pipe, the outer pipe maintains structural strength, the inner pipe has a small heat capacity, and thermal contact with the outside is made. An exhaust double pipe formed so as to be cut off has been proposed. According to this exhaust double pipe, it is expected that the exhaust gas temperature can be properly adjusted by effectively utilizing the gap between the outer pipe and the inner pipe.

【０００５】上記排気二重管としては，例えば，実開昭
６３−１７０５１９号公報「二重エキゾーストパイプの
端部構造」に開示されているものがある。この技術を，
図４により詳細に説明すると，外管１３のエンジン側の
一端において，外管１３と内管１２の一端を閉じて接合
し，かつ内管１２および外管１３をフランジ９に結合
し，さらに外管１３の他端では内管１２が金属メッシュ
１８により摺動可能に保持され，熱的接触を少なくする
と共に，内管１２が外管１３よりも高温になることによ
る熱膨張差を吸収している。An example of the above-mentioned exhaust double pipe is disclosed in Japanese Utility Model Laid-Open No. 63-170519, "End structure of double exhaust pipe". This technology
In more detail with reference to FIG. 4, one end of the outer pipe 13 and the inner pipe 12 are closed and joined at one end of the outer pipe 13 on the engine side, and the inner pipe 12 and the outer pipe 13 are joined to the flange 9, At the other end of the pipe 13, the inner pipe 12 is slidably held by the metal mesh 18 to reduce the thermal contact and absorb the difference in thermal expansion caused by the inner pipe 12 having a higher temperature than the outer pipe 13. There is.

【０００６】ところが，この排気二重管によれば，内管
１２と外管１３の間の間隙によって保温効果が高まり，
排気ガス温度を昇温して触媒の活性化を高めることがで
きるものの，排気ガス温度の高い高負荷走行では，排気
ガス等の温度が高くなり過ぎて，排気二重管の下流に位
置する部品，例えば，触媒や排気管マウントゴム等の部
品の熱性能，熱信頼性を確保することが難しくなるとい
う不具合がある。However, according to this exhaust double pipe, the heat retaining effect is enhanced due to the gap between the inner pipe 12 and the outer pipe 13,
Although the temperature of the exhaust gas can be raised to increase the activation of the catalyst, the temperature of the exhaust gas etc. becomes too high during high-load running where the exhaust gas temperature is high, and it is a part located downstream of the exhaust double pipe. However, for example, there is a problem that it becomes difficult to secure the thermal performance and thermal reliability of parts such as a catalyst and exhaust pipe mount rubber.

【０００７】したがって，排気二重管を効果的に使用す
るためには，排気ガス温度の高い高負荷走行時における
排気ガスの冷却に関する対処が必要であり，これを解決
するものとして，実開平２−１１２９２６号公報に開示
されている「内燃機関のエグゾストマニホールド」のよ
うに，内管の一部に運転状況に応じて開閉可能な仕切部
材を設け，内管と外管の間の間隙に排気ガスを流通させ
て，高負荷走行時における排気ガスの冷却を可能とした
排気二重管が提案されている。Therefore, in order to effectively use the exhaust double pipe, it is necessary to deal with the cooling of the exhaust gas at the time of running under high load where the exhaust gas temperature is high. As in the "exhaust manifold of an internal combustion engine" disclosed in Japanese Patent Laid-Open No. 112926, a partition member that can be opened and closed according to operating conditions is provided in a part of the inner pipe, and a gap between the inner pipe and the outer pipe is provided. An exhaust double pipe has been proposed that allows the exhaust gas to flow and cool the exhaust gas during high-load traveling.

【０００８】[0008]

【発明が解決しようとする課題】しかしながら，上記実
開平２−１１２９２６号公報によれば，排気ガスが高温
時に，仕切部材を開いて内管と外管の間の間隙に排気ガ
スを流通させることにより，冷却効果を高めることがで
きるものの，仕切部材を開閉するための開閉機構が必要
となるため，構成が複雑になり，コスト高になるという
問題点や，開閉機構が高温の排気ガスに曝されるため，
耐久性の確保が困難であるという問題点があった。However, according to the above Japanese Utility Model Laid-Open No. 2-112926, when the exhaust gas has a high temperature, the partition member is opened to allow the exhaust gas to flow through the gap between the inner pipe and the outer pipe. Although the cooling effect can be enhanced, an opening / closing mechanism for opening / closing the partition member is required, which complicates the configuration and increases the cost, and the opening / closing mechanism is exposed to high-temperature exhaust gas. Because
There is a problem that it is difficult to secure durability.

【０００９】この発明は，上記に鑑みてなされたもので
あって，簡単な構成・低価格・高耐久性で，高負荷走行
時における排気ガスの冷却を可能とした排気二重管を提
供することを目的とする。The present invention has been made in view of the above, and provides an exhaust double pipe which has a simple structure, low cost, and high durability, and which is capable of cooling exhaust gas during high load traveling. The purpose is to

【００１０】[0010]

【課題を解決するための手段】この発明は，上記目的を
達成するために，請求項１に係る排気二重管は，排気ガ
ス通路を形成する内管と，前記内管の排気ガス流入口側
において内管の一端を支持・固定し，排気ガス流出口側
において内管を摺動可能に保持し，かつ，前記内管との
間に間隙を形成して前記内管を収納する外管とを有した
排気二重管において，前記排気ガス流入口近傍の内管の
壁面に設けられ，排気ガスを前記間隙へ流入させる開口
部と，前記内管の排気ガス流出口側に設けられ，排気ガ
ス流出口側に向かって外径を拡大させた内管拡大部と，
前記外管の排気ガス流出口側に設けられ，排気ガス流出
口側に向かって内径を拡大させた外管拡大部とを備え，
排気ガスの温度が低くて前記内管が収縮した場合に，前
記内管拡大部と外管が当接して前記間隙の一部を塞ぎ，
排気ガスの温度が高くて前記内管が伸長した場合に，前
記内管拡大部と外管が離間して間隙が形成されるもので
ある。In order to achieve the above-mentioned object, the present invention provides an exhaust double pipe according to claim 1, wherein an inner pipe forming an exhaust gas passage, and an exhaust gas inlet of the inner pipe. Outer pipe for supporting and fixing one end of the inner pipe on the side, holding the inner pipe slidably on the exhaust gas outlet side, and forming a gap between the inner pipe and the inner pipe In an exhaust double pipe having, an opening portion which is provided on a wall surface of the inner pipe near the exhaust gas inlet port and allows exhaust gas to flow into the gap, and an exhaust gas outlet port side of the inner pipe, An inner pipe expansion part whose outer diameter is expanded toward the exhaust gas outlet side,
The outer pipe is provided on the exhaust gas outlet side of the outer pipe, and has an outer pipe enlarged portion whose inner diameter is enlarged toward the exhaust gas outlet side,
When the temperature of the exhaust gas is low and the inner pipe contracts, the inner pipe enlarged portion and the outer pipe come into contact with each other to partially close the gap,
When the temperature of the exhaust gas is high and the inner pipe is expanded, the inner pipe expansion portion and the outer pipe are separated from each other to form a gap.

【００１１】また，請求項２に係る排気二重管は，前記
内管拡大部の外径が前記外管の内径と略同一寸法であ
り，前記内管が収縮した場合に，前記内管拡大部が前記
外管に嵌合して前記間隙の一部を塞ぎ，前記内管が伸長
した場合に，前記内管拡大部が前記外管から外れて間隙
を形成するものである。Also, in the exhaust double pipe according to claim 2, the outer diameter of the inner pipe expanding portion is substantially the same as the inner diameter of the outer pipe, and when the inner pipe contracts, the inner pipe expanding When the inner pipe expands, the inner pipe expanded portion is disengaged from the outer pipe to form a gap when the portion fits into the outer pipe to close a part of the gap.

【００１２】[0012]

【作用】この発明の排気二重管（請求項１）は，エンジ
ン運転時に排気ガスが，常に内管等を通って触媒等に導
入される。そして排気ガス温度が低い場合には内管が収
縮し，内管拡大部と外管が当接して内管と外管との間の
間隙の一部が自動的に閉じることで，開口部から流入し
た排気ガスが間隙に封じ込まれて断熱層として作用する
ので，内管を通る排気ガスが有効に昇温される。また，
排気ガスの温度が高い場合には内管が伸長し，内管拡大
部と外管が離間して間隙が自動的に開き，開口部から流
入した排気ガスが間隙を通過して温度の低い外管で冷却
され，排気ガス流出口側へ到達するので，排気ガス流出
口側のガス温度が低く保たれる。In the exhaust double pipe of the present invention (claim 1), the exhaust gas is always introduced into the catalyst or the like through the inner pipe or the like during engine operation. Then, when the exhaust gas temperature is low, the inner pipe contracts, the inner pipe expansion portion and the outer pipe contact each other, and a part of the gap between the inner pipe and the outer pipe is automatically closed, so that The inflowing exhaust gas is confined in the gap and acts as a heat insulating layer, so that the exhaust gas passing through the inner pipe is effectively heated. Also,
When the temperature of the exhaust gas is high, the inner pipe expands, the inner pipe expansion part and the outer pipe are separated from each other, and the gap automatically opens, and the exhaust gas flowing from the opening passes through the gap and the outside temperature is low. Since it is cooled by the pipe and reaches the exhaust gas outlet side, the gas temperature on the exhaust gas outlet side is kept low.

【００１３】また，この発明の排気二重管（請求項２）
は，内管拡大部の外径が外管の内径と略同一寸法であ
り，内管が収縮した場合に，内管拡大部が外管に嵌合す
るため，例えば，組付け誤差等により内管の収縮状態が
変動しても，間隙が確実に閉じられる。The exhaust double pipe of the present invention (claim 2)
Is that the outer diameter of the enlarged inner pipe is approximately the same as the inner diameter of the outer pipe, and when the inner pipe contracts, the enlarged inner pipe fits into the outer pipe. Even if the contraction state of the pipe fluctuates, the gap is closed securely.

【００１４】[0014]

【実施例】以下，この発明の一実施例を図面に基づいて
詳細に説明する。図１は排気二重管の縦断面図を示し，
図２は図１のＡ−Ａ断面図を示す。これらの図におい
て，排気二重管１０は，その一端がエンジン１側のフラ
ンジ１１に固定されており，他端が触媒２側のフランジ
１２に固定されている。排気二重管１０はエンジン１か
らの排気ガスを矢印のガス流れ方向に導いて触媒２に導
入する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. Figure 1 shows a vertical cross section of an exhaust double pipe,
FIG. 2 is a sectional view taken along line AA of FIG. In these drawings, the exhaust double pipe 10 has one end fixed to a flange 11 on the engine 1 side and the other end fixed to a flange 12 on the catalyst 2 side. The exhaust double pipe 10 guides the exhaust gas from the engine 1 in the gas flow direction indicated by the arrow and introduces it into the catalyst 2.

【００１５】また，排気二重管１０は，筒状の外管１３
の軸方向略全域の内部に，排気ガス通路１４を備えた内
管１５が，所定の間隙１６を有して二重に挿入される。
外管１３は，肉厚が厚くて構造上の強度を有するように
形成され，この外管１３の両端にフランジ１１，１２が
一体結合される。内管１５は，肉厚が薄くて熱容量が小
さくなるように形成されており，その壁温を瞬時に上昇
させて排気ガス温度の昇温が迅速に行えるように構成さ
れている。Further, the exhaust double pipe 10 has a cylindrical outer pipe 13
An inner pipe 15 having an exhaust gas passage 14 is doubly inserted with a predetermined gap 16 inside substantially the entire axial direction.
The outer tube 13 is formed to have a large wall thickness and structural strength, and the flanges 11 and 12 are integrally connected to both ends of the outer tube 13. The inner pipe 15 is formed so as to have a small wall thickness and a small heat capacity, and is configured so that the wall temperature of the inner pipe 15 can be instantly increased to quickly raise the exhaust gas temperature.

【００１６】また，内管１５は，ガス流れ方向上流端部
（図１の右側）の外周の全域に，多数のＶ字形金具１７
が等間隔に取付けられている。この金具１７は，外管１
３のガス流れ方向上流端部に内接してスポット溶接等に
より固定されている。これにより内外管１３，１５の間
に間隙１６と連通するガス流入口１８を均一に形成して
一体結合される。したがって，間隙１６に常に排気ガス
を導入することが可能となる。さらに，内管１５の端部
には金属メッシュ１９が取付けられており，この金属メ
ッシュ１９を外管１３に移動可能に摺接して，熱膨張差
を吸収する構成である。Further, the inner pipe 15 has a large number of V-shaped metal fittings 17 all over the outer circumference of the upstream end (right side in FIG. 1) in the gas flow direction.
Are installed at equal intervals. This metal fitting 17 is an outer tube 1
It is inscribed in the upstream end of the gas flow direction 3 and is fixed by spot welding or the like. As a result, the gas inlet 18 communicating with the gap 16 is uniformly formed between the inner and outer pipes 13 and 15 and integrally coupled. Therefore, it is possible to always introduce the exhaust gas into the gap 16. Further, a metal mesh 19 is attached to the end portion of the inner pipe 15, and the metal mesh 19 is slidably slidably contacted with the outer pipe 13 to absorb the difference in thermal expansion.

【００１７】また，外管１３のガス流れ方向下流側（図
１の左側）の部位に径の大きい拡径部１３ａが，テーパ
部１３ｂを介して徐々に拡径するように形成されてい
る。同様に内管１５にも，拡径部１５ａがテーパ部１５
ｂを介して形成される。内管１５の拡径部１５ａは，間
隙１６の幅だけ拡径され，拡径部１５ａの外径Ｄ１が外
管１３の内径Ｄ２と略同一寸法に設定される。このた
め，ガス温度が低くて内管１５が収縮する場合は，内管
１５の拡径部１５ａが外管１３に略緊密に嵌合して間隙
１６の一部を閉じる。これにより間隙１６が断熱層とし
て作用して排気ガスを昇温する昇温機能を備える。Further, a diameter-expanded portion 13a having a large diameter is formed on the downstream side (left side in FIG. 1) of the outer tube 13 in the gas flow direction so that the diameter is gradually increased via the tapered portion 13b. Similarly, the inner pipe 15 also has the enlarged diameter portion 15a and the tapered portion 15a.
It is formed via b. The enlarged diameter portion 15a of the inner pipe 15 is enlarged by the width of the gap 16, and the outer diameter D1 of the enlarged diameter portion 15a is set to be substantially the same as the inner diameter D2 of the outer pipe 13. Therefore, when the gas temperature is low and the inner tube 15 contracts, the enlarged diameter portion 15a of the inner tube 15 fits the outer tube 13 in a substantially tight manner to close a part of the gap 16. As a result, the gap 16 acts as a heat insulating layer and has a temperature raising function of raising the temperature of the exhaust gas.

【００１８】また，ガス温度が高くて内管１５が伸長す
ると，内管１５の拡径部１５ａが外管１３から触媒２側
に離脱して前記閉じていた間隙１６の一部を開く（開放
する）。これによりガス流入口１８から間隙１６に流入
した排気ガスが，間隙１６および金属メッシュ１９を通
過して触媒２側へ送出される。このとき排気ガスは温度
の低い外管１３により冷却される。Further, when the gas temperature is high and the inner tube 15 expands, the enlarged diameter portion 15a of the inner tube 15 is separated from the outer tube 13 toward the catalyst 2 side to open a part of the closed gap 16 (open). To). As a result, the exhaust gas flowing from the gas inlet 18 into the gap 16 passes through the gap 16 and the metal mesh 19 and is delivered to the catalyst 2 side. At this time, the exhaust gas is cooled by the outer pipe 13 having a low temperature.

【００１９】次に，この実施例の動作について説明す
る。エンジン運転時にエンジン１から排出する排気ガス
が，常に排気二重管１０の内管１５の排気ガス通路１４
等を通り触媒２に導入される。そこでエンジン１の低温
始動時のように排気ガス温度が低い場合は，内管１５が
収縮してその拡径部１５ａが，図１のように外管１３に
略緊密に嵌合する。このため内外管１３，１５の間の間
隙１６の一部（下流側）が自動的に閉じて，排気ガスが
間隙１６に封じ込まれ，この間隙１６が断熱層として作
用して内管１５が温度の低い外管１３から熱的に遮断さ
れる。このため内管１５の排気ガス通路１４を通る排気
ガスは，有効に昇温されて触媒２に導入される。したが
って，触媒２は早期に活性温度に達し，排気エミッショ
ンが向上する。Next, the operation of this embodiment will be described. Exhaust gas exhausted from the engine 1 during engine operation is always exhaust gas passage 14 of the inner pipe 15 of the exhaust double pipe 10.
And the like and are introduced into the catalyst 2. Therefore, when the temperature of the exhaust gas is low such as when the engine 1 is started at a low temperature, the inner pipe 15 contracts and the expanded diameter portion 15a thereof is fitted into the outer pipe 13 in a substantially tight fit as shown in FIG. Therefore, a part (downstream side) of the gap 16 between the inner and outer pipes 13 and 15 is automatically closed and the exhaust gas is confined in the gap 16, and the gap 16 acts as a heat insulating layer to form the inner pipe 15. The outer tube 13 having a low temperature is thermally cut off. Therefore, the exhaust gas passing through the exhaust gas passage 14 of the inner pipe 15 is effectively heated and introduced into the catalyst 2. Therefore, the catalyst 2 reaches the activation temperature early and the exhaust emission is improved.

【００２０】この場合において，内管１５の拡径部１５
ａがそのまま外管１３に嵌合するため，組付け誤差等に
より，多少内管１５の収縮状態（収縮・伸長による変動
長さ）が変動しても，間隙１６の一部を確実に閉じるこ
とができる。In this case, the expanded diameter portion 15 of the inner pipe 15
Since a is directly fitted to the outer tube 13, even if the contracted state of the inner tube 15 (variable length due to contraction / expansion) fluctuates due to an assembly error or the like, a part of the gap 16 can be surely closed. You can

【００２１】また、エンジン高負荷の走行時のように排
気ガス温度が高くなると，そのガス温度により内管１５
が熱せられて伸長する。すると内管１５の拡径部１５ａ
が，図３のように外管１３から離脱して間隙１６の一部
（下流側）が自動的に開く。この場合は，ガス流入口１
８から間隙１６に入った排気ガスがその間隙１６を通過
するようになり，このとき温度の低い外管１３により間
隙１６の排気ガスを冷却するように熱交換される。そし
て間隙１６を通過した低温のガスが出口側で再び主流の
排気ガス通路１４の排気ガスと混合する。したがって，
排気二重管１０の出口側のガス温度が低く保たれ，排気
二重管１０の下流の種々の部品の熱性能を損なうことが
防止される。When the exhaust gas temperature rises, such as when the engine is running under a high load, the inner pipe 15 is affected by the gas temperature.
Is heated and expands. Then, the expanded diameter portion 15a of the inner pipe 15
However, as shown in FIG. 3, it separates from the outer tube 13 and a part (downstream side) of the gap 16 automatically opens. In this case, gas inlet 1
The exhaust gas that has entered the gap 16 from 8 passes through the gap 16, and at this time, the outer pipe 13 having a low temperature is heat-exchanged so as to cool the exhaust gas in the gap 16. Then, the low temperature gas that has passed through the gap 16 mixes again with the exhaust gas in the main exhaust gas passage 14 on the outlet side. Therefore,
The gas temperature on the outlet side of the exhaust double pipe 10 is kept low, and the thermal performance of various parts downstream of the exhaust double pipe 10 is prevented from being impaired.

【００２２】なお，内管の拡径部の径を上記実施例の場
合より大きくしてそのテーパ部を，外管のテーパ部の角
部に接離させることにより，内管・外管の間隙を開閉す
るように構成することもできる。また，排気二重管はス
トレートのみならず，曲っている場合にも適応できるの
は勿論である。It should be noted that the diameter of the expanded portion of the inner pipe is made larger than that in the above-mentioned embodiment, and the taper portion is brought into contact with and separated from the corner portion of the taper portion of the outer pipe, whereby the gap between the inner pipe and the outer pipe is increased. Can also be configured to open and close. In addition, the exhaust double pipe can be applied not only to a straight pipe but also to a bent pipe.

【００２３】[0023]

【発明の効果】以上説明した通り，請求項１に係る排気
二重管は，排気ガス流入口近傍の内管の壁面に設けら
れ，排気ガスを間隙へ流入させる開口部と，内管の排気
ガス流出口側に設けられ，排気ガス流出口側に向かって
外径を拡大させた内管拡大部と，外管の排気ガス流出口
側に設けられ，排気ガス流出口側に向かって内径を拡大
させた外管拡大部とを備え，排気ガスの温度が低くて内
管が収縮した場合に，内管拡大部と外管が当接して間隙
の一部を塞ぎ，排気ガスの温度が高くて内管が伸長した
場合に，内管拡大部と外管が離間して間隙が形成される
ため，低温始動時には従来の排気二重管と同様に排気昇
温性能を確保できると共に，簡単な構成・低価格・高耐
久性で，高負荷走行時における排気ガスの冷却が可能と
なる。As described above, the exhaust double pipe according to claim 1 is provided on the wall surface of the inner pipe in the vicinity of the exhaust gas inlet, and has an opening for allowing the exhaust gas to flow into the gap and the exhaust of the inner pipe. The inner pipe expansion part, which is provided on the gas outlet side and whose outer diameter is enlarged toward the exhaust gas outlet side, and the outer pipe is provided on the exhaust gas outlet side, and the inner diameter is increased toward the exhaust gas outlet side. When the inner pipe contracts when the temperature of the exhaust gas is low and the inner pipe contracts, the inner pipe enlarged part and the outer pipe contact and partially close the gap, and the exhaust gas temperature rises. When the inner pipe is extended, the inner pipe expansion and the outer pipe are separated from each other to form a gap. The configuration, low cost, and high durability enable exhaust gas cooling during high-load running.

【００２４】また，請求項２に係る排気二重管は，内管
拡大部の外径が外管の内径と略同一寸法であり，内管が
収縮した場合に，内管拡大部が外管に嵌合して間隙の一
部を塞ぎ，内管が伸長した場合に，内管拡大部が外管か
ら外れて間隙を形成する構成であるため，組付け誤差等
により内管の収縮状態が変動しても，間隙を常に確実に
閉じることができ，動作性も良い。Further, in the exhaust double pipe according to the second aspect, the outer diameter of the inner pipe enlarged portion is substantially the same as the inner diameter of the outer pipe, and when the inner pipe contracts, the inner pipe enlarged portion has the outer pipe. When the inner tube expands when the inner tube expands, the inner tube expansion part separates from the outer tube to form a gap. Even if it fluctuates, the gap can always be closed reliably and the operability is good.

【図面の簡単な説明】[Brief description of drawings]

【図１】この発明に係る排気二重管の実施例を示す縦断
面図である。FIG. 1 is a vertical sectional view showing an embodiment of an exhaust double pipe according to the present invention.

【図２】図１のＡ−Ａ断面図である。FIG. 2 is a sectional view taken along line AA of FIG.

【図３】排気ガス温度が高い場合の排気二重管の状態を
示す縦断面図である。FIG. 3 is a vertical cross-sectional view showing a state of an exhaust double pipe when the exhaust gas temperature is high.

【図４】従来の排気二重管の断面図である。FIG. 4 is a cross-sectional view of a conventional exhaust double pipe.

【符号の説明】[Explanation of symbols]

１０ 排気二重管 １３ 外管 １３ａ 拡径部 １５ 内管 １５ａ 拡径部 １６ 間隙 １９ 金属メッシュ 10 Exhaust Double Pipe 13 Outer Pipe 13a Expanded Part 15 Inner Tube 15a Expanded Part 16 Gap 19 Metal Mesh

Claims (2)

【特許請求の範囲】[Claims] 【請求項１】 排気ガス通路を形成する内管と，前記内
管の排気ガス流入口側において内管の一端を支持・固定
し，排気ガス流出口側において内管を摺動可能に保持
し，かつ，前記内管との間に間隙を形成して前記内管を
収納する外管とを有した排気二重管において，前記排気
ガス流入口近傍の内管の壁面に設けられ，排気ガスを前
記間隙へ流入させる開口部と，前記内管の排気ガス流出
口側に設けられ，排気ガス流出口側に向かって外径を拡
大させた内管拡大部と，前記外管の排気ガス流出口側に
設けられ，排気ガス流出口側に向かって内径を拡大させ
た外管拡大部とを備え，排気ガスの温度が低くて前記内
管が収縮した場合に，前記内管拡大部と外管が当接して
前記間隙の一部を塞ぎ，排気ガスの温度が高くて前記内
管が伸長した場合に，前記内管拡大部と外管が離間して
間隙が形成されることを特徴とする排気二重管。1. An inner pipe forming an exhaust gas passage, and one end of the inner pipe is supported and fixed on the exhaust gas inlet side of the inner pipe, and the inner pipe is slidably held on the exhaust gas outlet side. And an exhaust double pipe having an outer pipe for accommodating the inner pipe with a gap formed between the inner pipe and the inner pipe, the exhaust gas being provided on a wall surface of the inner pipe in the vicinity of the exhaust gas inlet. To the gap, an inner pipe expansion portion provided on the exhaust gas outlet side of the inner pipe and having an outer diameter enlarged toward the exhaust gas outlet side, and an exhaust gas flow of the outer pipe. An outer pipe expanding portion provided on the outlet side and having an inner diameter enlarged toward the exhaust gas outlet side, and when the inner pipe contracts due to a low exhaust gas temperature, the inner pipe expanding portion and the outer pipe expand When the tubes come into contact with each other to block a part of the gap and the temperature of the exhaust gas is high and the inner tube extends, An exhaust double pipe, wherein the inner pipe enlarged portion and the outer pipe are separated from each other to form a gap. 【請求項２】 前記内管拡大部は，その外径が前記外管
の内径と略同一寸法であり，前記内管が収縮した場合
に，前記内管拡大部が前記外管に嵌合して前記間隙の一
部を塞ぎ，前記内管が伸長した場合に，前記内管拡大部
が前記外管から外れて間隙を形成することを特徴とする
請求項１記載の排気二重管。2. The inner pipe enlarging portion has an outer diameter substantially the same as an inner diameter of the outer pipe, and when the inner pipe contracts, the inner pipe enlarging portion fits into the outer pipe. 2. The exhaust double pipe according to claim 1, wherein when the inner pipe expands, a part of the gap is closed, and the inner pipe expansion portion separates from the outer pipe to form a gap.