JP2006250524A - Multi-pipe type heat recovery apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve heat recovery efficiency with a simple structure in a flow passage switch type multi-pipe type heat recovery apparatus. <P>SOLUTION: In this multi-pipe type heat recovery apparatus, an annular cooling medium passage 9 extending to an axial direction is constituted by an intermediate cylinder 4 fixed to an inner surface of an outer cylinder. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a multi-tube heat recovery device that is provided in an exhaust passage of an internal combustion engine or the like and exchanges heat between exhaust gas and a cooling medium, and in particular, includes an annular passage that circulates during heat exchange and a bypass passage that passes through the center The present invention relates to a multi-tube heat recovery device that can be selectively switched.

  Conventionally, a heat exchanger (hereinafter referred to as a heat recovery unit) that is provided in the middle of an exhaust pipe of an internal combustion engine, a combustion apparatus or the like, switches the internal flow path when necessary, and recovers the heat of the exhaust gas to a gaseous medium or a liquid medium. )It has been known. The recovered heat is delivered to a necessary location such as a vehicle via a medium (hereinafter referred to as a cooling medium), or is subjected to secondary heat exchange with another cooling medium on the way, and finally heated. It is also used for warming up various devices and heating oils and fats. On the other hand, when heat recovery is unnecessary, the flow path in the heat recovery unit is switched to guide the exhaust gas to the bypass flow path, and the exhaust gas is discharged straight without going through the heat exchanging portion, thereby suppressing an increase in pressure loss. Therefore, at the time of bypass, it is desirable that the bypass channel is thick and straight, as well as not having a heat exchanger in the channel.

  As a structure of this type of flow path switching type heat recovery device, a so-called multi-tube type in which an annular gap between a plurality of tubes arranged coaxially is used as a flow path is common. As the structure of the multi-tube heat recovery device, the structure described in Japanese Utility Model Laid-Open No. 63-110615 is known, and FIG. 10 shows a typical structure described in the same publication. The outer cylinder 101, the intermediate cylinder 103, and the inner cylinder 102 are coaxially arranged, and the inner cylinder 102 has a first exhaust passage 106, and the inner cylinder 102 and the intermediate cylinder 103 have a gap between the second exhaust passage 107 and the middle. A gap between the cylinder 103 and the outer cylinder 101 is defined in the cooling medium passage 108. Further, on the upstream side thereof, a valve body 104 that can open and close substantially at the front end of the inner cylinder 106 is provided. When closed, exhaust gas is mainly guided to the second exhaust passage 107 serving as a heat recovery passage, and then the small hole group 105 is provided. To return to the first exhaust passage and discharge. On the other hand, at the time of opening, the exhaust gas is mainly guided and discharged to the first exhaust passage 106 serving as a bypass flow path. The valve body 104 is opened and closed according to the necessity of heat recovery, and the flow path is appropriately selected.

  Another structure of the multi-tube heat recovery device is known as described in Japanese Utility Model Laid-Open No. 63-115520, and FIG. 11 shows a typical structure described in the same publication. The outer cylinder 201 and the inner cylinder 202 are coaxially arranged. The inner cylinder 202 is defined by a first exhaust passage 205, and the gap between the inner cylinder 202 and the outer cylinder 201 is defined by a second exhaust passage 206. A cooling medium passage 207 of a helical tube is provided in the second exhaust passage 206. A valve body 203 is disposed in the downstream end of the inner cylinder 202 so as to be openable and closable, and a small hole group 204 is formed in the upstream end of the inner cylinder 202. With such a configuration, when the valve body 203 is closed, the exhaust gas is mainly guided to the second exhaust passage 206 serving as a heat recovery path, and is applied to the spiral tubular cooling medium path 207 to perform heat recovery.

Japanese Utility Model Publication No. 63-110615 Japanese Utility Model Publication No. 63-115520

  However, in the multi-tube heat recovery device described in Patent Document 1, since the intermediate tube 103 bears the structural strength, it is inevitable to increase the thickness. However, in order to improve heat exchange efficiency, the intermediate tube 103 is a heat transfer wall. It is difficult to obtain an efficient and high-strength heat recovery device that has the contradiction that the tube 103 must be thinned.

  Moreover, although the multi-tube heat recovery device described in Patent Document 2 has a simple double-pipe structure, it has a problem because the cooling medium passage 207 is a spiral tube. That is, the high-temperature exhaust gas hits the uppermost (first winding) spiral, but after that it is difficult to hit the entire surface, so the heat exchange efficiency is low. Therefore, in this cooling medium passage, there is a problem that desired heat recovery is difficult even if the spiral length and thickness are increased. Furthermore, it is very difficult to manufacture the spiral tube so that it does not interfere with the annular second exhaust passage 206, and the both ends penetrate the outer tube 207, and the structure in which the spring-like material is exposed to the pulsating fluid. May cause vibration damage.

  In order to solve the above-described problems, the present invention provides a multi-tube heat recovery device provided in an exhaust passage for exchanging heat between exhaust gas and a cooling medium, as described in claim 1, wherein In selecting the flow path and changing the heat recovery state, an intermediate cylinder is disposed between the outer cylinder and the inner cylinder, and this intermediate cylinder is fixed to the inner surface of the outer cylinder and constitutes a passage for the cooling medium.

  Further, as described in claim 2, a second intermediate cylinder may be provided on the outer surface of the inner cylinder to add another cooling medium passage, and the exhaust gas flow path may be surrounded by the inner and outer cooling medium passages. .

  Further, as described in claim 3, it is preferable that the surface of the intermediate cylinder is provided with irregularities such as spiral streaks, protrusions, and undulations to promote heat exchange with the fluid.

  Further, as described in claim 4, the multi-tube heat recovery device, the catalytic converter and / or the silencer may be integrally formed in the outer cylinder.

  According to the first aspect of the present invention, the annular cooling medium passage extending in the axial direction is formed on the inner surface of the outer tube of the double tube by the thin intermediate tube, so that the high heat recovery efficiency is maintained. Thus, it is possible to realize a multi-tube heat recovery device that is lightweight, has a simple structure, and is easy to manufacture.

  According to the second aspect of the present invention, the exhaust passage is surrounded by the further expansion of the cooling medium passage, so that the heat recovery efficiency is improved.

  According to the third aspect of the present invention, both the exhaust gas, which is a fluid, and the cooling medium increase the contact area with the intermediate cylinder, improve the contact at the boundary surface, and further improve the heat recovery efficiency.

  According to the fourth aspect of the present invention, it is possible to save weight and space as compared to connecting a separate exhaust gas purifier and / or a silencer via an exhaust pipe, and also improve durability. .

  The best mode for carrying out the present invention will be described based on the embodiment shown in FIGS. In the first embodiment shown in FIGS. 1 and 2, the heat recovery unit 1 has an outer shell composed of an outer cylinder 2 mainly responsible for the structural strength, and tapered necking portions are integrally formed at both ends of the outer cylinder 2. ing. The introduction port 5 and the discharge port 6 for the cooling medium are fitted and fixed, respectively. The inner cylinder 3 is fitted and fixed to the upstream necking portion of the outer cylinder 2, and the inner cylinder 3 extends into the outer cylinder 2. A downstream component such as the exhaust pipe 16 is fitted and fixed to the downstream necking portion of the outer cylinder 2. A valve body 10 that is opened and closed by exhaust gas pressure is pivotally supported via a bracket 11 at the downstream end of the inner cylinder 3, and the rear end of the inner cylinder 3 is normally closed by a biasing means (not shown). . Further, a small hole group 12 is formed on the upstream side of the inner cylinder 3, and when the rear end of the inner cylinder 3 is closed by the valve body 10, exhaust gas is positively passed from the first exhaust passage 7 to the second exhaust passage 8. Are derived. The above constituent members are all made of metal having corrosion resistance. The upstream end of the inner cylinder 3 is usually fitted and connected to the upstream exhaust pipe, but the upstream exhaust pipe may be the inner cylinder 3 or a fastening flange may be externally fitted.

  The valve body 10 that opens and closes by the exhaust gas pressure is a so-called dynamic pressure variable valve that is well-known in the exhaust system, and will not be described in detail. However, the valve body 10 is closed when the exhaust gas pressure (or flow rate) in the inner cylinder 3 is below a certain level. It begins to open against the bias at a certain value or more, and the opening degree increases as the dynamic pressure increases. Accordingly, when the valve body 10 is opened, the main flow changes from the second exhaust passage 8 to the first exhaust passage 7 and shifts from the heat recovery direction to the exhaust gas outflow (passage) direction. Accordingly, while the heat recovery is fundamental, it is possible to bypass the heat recovery and pass the exhaust gas with low resistance when the internal combustion engine or the like is at a high output (at a high flow rate). Further, when it is desired to perform the switching control arbitrarily without depending on the exhaust gas pressure, the drive shaft of the valve body 10 is airtightly extended to the outside of the outer cylinder 2 and the forced drive control by a known motor or actuator is used. May be. According to the forced opening and closing, the work for opening the valve body as the exhaust gas is a dynamic pressure becomes unnecessary, which is more suitable for the low pressure loss requirement at the time of bypass. Moreover, what is necessary is just to use well-known valve systems, such as a butterfly type, a slide type, and a closing body fitting type, for the valve body 10 in addition to a flap type for both the dynamic pressure type and the forced open / close type. Furthermore, with regard to actuators, electric, hydraulic, pneumatic, etc. are well known, but thermowax or shape memory alloy that strokes in response to heat is combined with a dynamic pressure variable valve to respond to the temperature of exhaust gas or refrigerant. Auxiliary control may be added.

  The intermediate cylinder 4 is installed on the inner surface of the outer cylinder 2 so as to define an annular cooling medium passage 9 extending in the axial direction, and the close contact portions 13 and 14 at both ends thereof are airtight to the inner surface of the outer cylinder 2. It is fixed. Since it is such a structure, since the intermediate cylinder 4 can be set thin regardless of the overall strength, the heat transfer efficiency can be improved. The cooling medium (water) flowing in from the introduction port 5 fills the cooling medium passage (water jacket) 9, exchanges heat with the exhaust gas while flowing upstream, and flows out from the discharge port 6 with heat. In order to secure a larger heat exchange area in the process of heat recovery in this way, the intermediate cylinder 4 is formed with spiral groove irregularities 15 in the tube axis direction. Turbulence occurs in the gas and activates the boundary layer, further promoting heat exchange.

  Since it comprised as mentioned above, desired heat recovery amount can be achieved with a lightweight and simple structure. In addition, since the intermediate cylinder 4 is attached to the inner surface of the outer cylinder 2 that bears the structural strength, it is possible to pursue a reduction in thickness and eventually heat exchange efficiency without fear of damage due to external force. Furthermore, the degree of freedom in setting the shape and area of the intermediate cylinder 4 such as the addition of irregularities is great.

  In addition, the cross-sectional shape of each pipe | tube is not restricted to a circle | round | yen, Arbitrary irregular cross-sections may be sufficient, and not only a coaxial arrangement | positioning but eccentricity (offset) arrangement | positioning mutually may be sufficient. Further, when both ends necking is integrally formed on the outer cylinder 2, a known plastic working method such as spinning or swaging may be applied after the interior is inserted. Further, a separate necking portion may be integrated by welding or the like, or the entire outer cylinder 2 may be used as a welded assembly of a pressed part. When applying the spinning process, it is preferable to use the eccentric spinning process of Patent Registration No. 2957153 or the inclined spinning process of Patent Registration No. 2957154. Similarly, the intermediate cylinder 4 may be integrally formed or a separate assembly. However, in the fixing to the outer cylinder 2, the contact portions 13 and 14 need to be hermetically welded and fixed. It is good to apply. Alternatively, in order to absorb the difference in relative thermal expansion in the axial direction, a part of the outer cylinder 2 and / or the intermediate cylinder 4 may have a bellows structure, or an airtight buffer member may be fitted to the contact portion 13 or 14. May be.

  Further, the irregularities provided on the surface of the intermediate cylinder 4 may have any shape, arrangement, and size, such as a spiral groove or the like, protrusions, dimples, and gentle undulations. What is necessary is just to set so that the tradeoff of heat exchange promotion and fluid resistance increase may be balanced appropriately.

  The basic configuration of the second embodiment shown in FIG. 3 is the same as that of the first embodiment, but the shape of the intermediate cylinder 20 is different. The inner surface of the intermediate cylinder 20 is tapered along the axial direction (left-right direction in the figure), and accordingly, the cross-sectional areas of the cooling medium passage 21 and the second exhaust passage 22 gradually change in the axial direction. Is made. Thereby, since exhaust gas and a cooling medium contact | abut to a taper surface strongly, heat exchange is accelerated | stimulated. When the above-described irregularities are combined with this structure, the heat exchange efficiency is further improved. The taper may be inclined in the opposite direction, or a curved surface may be used in combination.

  In the third embodiment shown in FIG. 4, a further heat recovery amount is intended, and a cooling medium passage (water jacket) is also added to the outer periphery of the inner cylinder. As described above, the intermediate cylinder 32 forms the cooling medium passage 36 on the inner surface of the outer cylinder 30. Similarly, the second intermediate cylinder 31 is also fixed to the outer peripheral surface of the inner cylinder 3, and the second cooling medium passage 37 is configured independently. That is, the second exhaust passage 35 is surrounded by the inner surface of the intermediate cylinder 32 and the outer surface of the second intermediate cylinder 31. Then, the cooling medium passage 36 and the second cooling medium passage 37 are fixed to each other through thin tubular communication pipes 33 and 34 so that the cooling medium can communicate freely. The number and arrangement of communication pipes are arbitrary.

  The cooling medium flowing into the cooling medium passage 36 from the introduction port 5 flows in the cooling medium passage 36 and also flows into the second cooling medium passage 37 via the communication pipe 34 and flows therein. The cooling medium collected by the communication pipe 33 is discharged from the discharge port 6. Since the second exhaust passage 35 is formed between the intermediate cylinder 32 and the second intermediate cylinder 31, that is, between the cooling medium passage 36 and the second cooling medium passage 37, heat exchange is performed by being surrounded by both. The heat exchange rate is further improved. Of course, the intermediate cylinder 32 and the second intermediate cylinder 31 may be tapered or uneven as described above. In the present embodiment, a metal cushioning member 39 is sandwiched between the straight tube portion 38 that is the front end portion of the outer tube 30 and the inner tube 3, and due to a temperature difference between the outer tube 30 and the inner tube 3. Although it is possible to follow a relative difference in thermal expansion, this mechanism may be used as appropriate.

  In the fourth embodiment shown in FIG. 5, a catalytic converter unit 50 as an exhaust gas purifier is provided upstream of the heat recovery unit of the first embodiment, and a silencer unit 51 is integrally provided downstream. The upstream end of the outer cylinder 40 extended to the upstream side and the downstream side has an inclined necking portion 46, the downstream end has a coaxial necking portion 47, and the heat recovery device of the first embodiment at the intermediate portion. Decorated. The front end of the inner cylinder 41 is integrally formed with a flare portion 42 whose diameter is increased in a tapered shape, and is fixed to the inner surface of the outer cylinder. A plurality of through holes 43 are formed in the flare portion 42 so that upstream exhaust gas can be introduced into the second exhaust passage 45. A catalyst carrier 48 is sandwiched between the inner surface of the outer cylinder 40 via a holding member 49 upstream of the flare portion 42. On the other hand, on the downstream side of the valve body 10, a separator 52 that defines the silencer portion 51 is fixed to the inner surface of the outer cylinder 40, and an outlet pipe 53 is fitted in the center of the separator 52. The space surrounded by the separator 52, the outlet pipe 53, and the outer cylinder 40 is filled with glass wool as a sound deadening material 55 at a constant density, and cooperates with the small hole group 54 formed in the outlet pipe 53. It functions as a resonance type silencer.

  Such integration not only has advantages in terms of weight, space, and manufacturing cost, but also improves durability by improving overall strength, compared to connecting separate devices with exhaust pipes. The heat dissipation loss is minimized by reducing the surface area. Furthermore, since the exhaust gas heated to a high temperature by a chemical reaction at the catalyst carrier can be recovered immediately, there is no loss in heat recovery. Further, even when high-frequency abnormal noise is generated by the concave and convex second exhaust passage 45 or the valve body 10, it is surely silenced by the resonance type silencer immediately after that.

  In addition, the presence or absence, the number, and the arrangement order of the catalytic converter and / or the silencer combined with the heat recovery unit are arbitrary. In addition, all known types and manufacturing methods may be applied to the catalytic converter and the silencer. In particular, in a catalytic converter, a so-called sizing method is suitable in which the outer cylinder 40 is reduced in diameter after the catalyst carrier 48 and the holding material 49 are inserted, and the holding material 49 (buffer mat) is compressed. Further, not only the ceramic carrier but also a metal carrier may be installed without a holding material, or directly welded to the outer cylinder end. The muffler portion may be provided with a large space inevitably generated between the valve body 10 and the separator 52 and used as an expansion chamber 56 for noise reduction. Moreover, you may combine with exhaust gas purifiers other than these, for example, a diesel particulate filter (DPF), a reformer, etc. Furthermore, in this embodiment, the outer cylinder 40 is formed from a single cylinder, but an outer cylinder in which a plurality of parts are assembled by welding or the like may be used.

  In the fifth embodiment shown in FIG. 6, a third intermediate cylinder 68 is added between the inner cylinder 3 and the second intermediate cylinder 31 of the heat recovery apparatus in the third embodiment, and the stress relaxation using the buffer member 39 is performed. The position of the mechanism is changed. The third intermediate cylinder 68 sandwiches the buffer member 39 with the inner cylinder 3 and is closely fixed to the second intermediate cylinder 62 to form an inner peripheral wall of the second cooling medium passage 66. The buffer member 39 made of a metal wire mesh is fixed to the inner cylinder 3 by spot welding. With such a configuration, even if an axial relative stress caused by a difference in thermal expansion occurs between the inner cylinder 3 and the third intermediate cylinder 68, the buffer member 39 slides on the surface of the inner cylinder 3, so that the stress is reduced. It is open and there is no fear of damage. Further, at the time of bypass, a large amount of high-temperature exhaust gas passes through the inner cylinder 3 and the inner cylinder 3 is overheated. However, in the space surrounded by the third intermediate cylinder 68 and both the buffer members 39, high heat is generated by the cooling medium and the intermediate cylinder. It also functions as a heat barrier layer that avoids transmission to The buffer member may be fixed to the third intermediate cylinder 68 instead of the inner cylinder 3, and is not limited to a wire mesh but may be any sliding member. Further, the inner cylinder 3 may be perforated and the space surrounded by the third intermediate cylinder 68 and the image buffer member 39 may be used as a resonance silencer as in the fourth embodiment.

  In the sixth embodiment shown in FIG. 7, the introduction port 5 and the discharge port 6 of the heat recovery unit in the third embodiment are changed. The leading end of the introduction port 72 faces the communication pipe 34 or the second cooling medium passage 37, the cooling medium is preferentially guided to the second cooling medium passage 37, and the discharge port 73 is arranged at a position substantially opposite to the introduction port 72. To do. With such a configuration, the cooling medium first flows in the second cooling medium passage 37 on the inner peripheral side, then flows into the cooling medium passage 36 on the outer peripheral side via the communication pipe 33, and reversely flows down to the discharge port 73. Discharged from. Since the cooling medium flows through two paths in different directions, the residence time becomes longer and the heat recovery efficiency is improved.

  The seventh embodiment shown in FIG. 8 is a cross-sectional view of the heat recovery device, and the cross-sectional position is the same as that of the first embodiment (FIG. 1). In the third embodiment, fins 80 that are undulated radially are provided over almost the entire area of the second exhaust passage between the intermediate cylinder 32 and the second intermediate cylinder 31 of the heat recovery device. The fins 80 are integrally formed by bending a thin metal plate, and the inner side folding is welded to the second intermediate cylinder 31, and the outer diameter folding is welded to the intermediate cylinder 32. The cross section is a so-called petal shape, and this cross section extends in the axial direction. As a result, the exhaust gas flowing down in the second exhaust passage comes into contact with the entire surface of the fin 80, and the heat received by the fin 80 is reliably transmitted to the intermediate cylinder 32 and the second intermediate cylinder 31, thereby further improving the heat recovery efficiency. To do. However, since the fin 80 is a fluid resistance for the exhaust gas, it is necessary to consider the increase in the back pressure due to the pressure loss as a contradiction.

  The so-called petal fin 80 of the present embodiment is well known in heat exchangers, but other well-known cross-sectional shapes may be applied, twisted around the axis, multilayered, or axial May exist intermittently in the direction. The fixing method may be any method such as welding, brazing, caulking, etc., and may be clamped without fixing using the spring back of the fin itself. If further improvement in the heat recovery rate is desired, fins may be additionally installed in the first exhaust passage 7 serving as a bypass passage. Of course, you may provide in each exhaust passage of 1st Example or 2nd Example.

  The eighth embodiment shown in FIG. 9 is a longitudinal sectional view of a heat recovery device 98 and its intermediate assembly 81 manufactured by two types of rotational plastic working. First, in the step (a), an outer cylinder 85 having an introduction port 85 and a discharge port 86 fixed in the same manner as in the first embodiment is prepared, and an intermediate cylinder 84 made of an integral pipe is inserted and fixed therein. An intermediate assembly 81 is obtained. A plurality of spiral grooves 83 continuous in the tube axis direction are formed in the central portion of the intermediate cylinder 84 by a known roller rolling method or the like, and this contributes to the promotion of heat exchange like the unevenness of the first embodiment. . Both ends of the intermediate cylinder 84 are enlarged in diameter, and are welded all around with a laser or the like in a state where the outer surfaces of the enlarged diameter parts 89 and 90 and the inner surface of the outer cylinder 82 are in close contact with each other to form airtight welds 87 and 88. The As a result, a cooling medium passage 85 defined by the outer cylinder 82 and the intermediate cylinder 84 is formed. In this state, it is preferable to fill the cooling medium passage 85 with a fluid and confirm the liquid tightness.

  Next, in step (b), the inner cylinder 3 having the small hole group 12, the valve body 10, and the bracket 11 is inserted into the intermediate assembly 81 in the same manner as in the first embodiment, and the upstream end portion 91 and the downstream end portion 92 are inserted. Then, an upstream necking portion 93 and a downstream necking portion 94 having arbitrary shapes are obtained by performing known spinning processing. The spinning process is performed by the spinning roller 97 that revolves and contacts the outer cylinder 82 relatively, but a method of revolving the spinning roller 97 with the outer cylinder fixed in a non-rotating state is preferable. The heat recovery device 98 is obtained through such steps.

  As in the first embodiment, the heat recovery device 98 is closed when the exhaust gas pressure (or flow rate) in the inner cylinder 84 is a predetermined value or less, and opens against a bias at a certain value or more. First, the opening is increased as the dynamic pressure increases. Accordingly, when the valve element 10 is opened, the main flow changes from the second exhaust passage 96 to the first exhaust passage 95 and shifts from the heat recovery direction to the outflow (passage) direction of the aeration gas. As described above, since the heat recovery device having the same function as that of the first embodiment can be formed by two types of rotary plastic processing, the processing time and processing cost can be reduced, and the outer cylinder 82 and the intermediate cylinder 84 are integrally formed from the pipe material. Since it can be formed, durability and reliability are improved. Further, since the degree of freedom in setting the shape is large because of the rotational plastic working, it is more advantageous in the integration with the exhaust gas purifier and the silencer.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and design changes within a range not departing from the gist of the present invention are also included in the present invention. It is not limited to a heat recovery device (heat collector) in a narrow sense that mainly recovers heat to the cooling medium, but is also used for heat exchangers (such as oil worms) for the purpose of heating the cooling medium and cooling exhaust gas The heat exchanger (exhaust cooler, etc.) is also included as a heat recovery device. The cooling medium is not limited to water, and an optimal liquid or gas may be used as appropriate. Furthermore, it includes not only the attachment to the main exhaust pipe but also the application to a side flow (branch flow) exhaust pipe such as an EGR cooler. The application target is not limited to an internal combustion engine such as a vehicle, but can be applied to an exhaust system of any exhaust gas generator such as a general-purpose engine or a stationary combustion device.

It is a schematic sectional drawing which shows the heat recovery device of a 1st Example. It is AA sectional drawing of a 1st Example. It is a schematic sectional drawing which shows the heat recovery device of a 2nd Example. It is a schematic sectional drawing which shows the heat recovery device of a 3rd Example. It is a schematic sectional drawing which shows the heat recovery device of a 4th Example. It is a schematic sectional drawing which shows the heat recovery device of a 5th Example. It is a schematic sectional drawing which shows the heat recovery device of a 6th Example. It is a schematic sectional drawing which shows the heat recovery device of a 7th Example. It is a schematic sectional drawing which shows the heat recovery device of an 8th Example. It is a schematic sectional drawing which shows the heat recovery device of a prior art example. It is a schematic sectional drawing which shows the heat recovery device of a prior art example.

Explanation of symbols

1,98 Heat recovery device 2, 30, 40, 71, 82 Outer cylinder 3, 41 Inner cylinder 4, 20, 32, 84 Intermediate cylinder 31 Second intermediate cylinder 5, 72, 85 Inlet ports 6, 73, 86 Discharge Ports 7, 44, 95 First exhaust passages 8, 35, 45, 67, 96 Second exhaust passages 9, 21, 36, 65, 85 Cooling medium passages 37, 66 Second cooling medium passages 33, 34, 63, 64 Communication pipe 10 Valve body 11 Brackets 12 and 54 Small hole groups 13 and 14 Adhering part 15 Concavity and convexity 38 Straight pipe part 39 Buffer member 42 Flare part 43 Through hole 46 and 47 Necking part 48 Catalyst carrier 49 Holding material 50 Catalytic converter part 51 Silencer part 52 Separator 53 Outlet pipe 55 Silencer 68 Third intermediate cylinder 80 Fin 81 Intermediate assembly 83 Spiral groove 87, 88 Welding part 89, 90 Expanded part 91 Upstream end 92 Downstream end 93 Upstream side necking part 94 Downstream side necking part 97 Spinning roller

Claims (4)

A multi-tube heat recovery device provided in the exhaust passage for exchanging heat between the exhaust gas and the cooling medium, wherein the exhaust gas flow path is selected by the included switching means and the heat recovery state is changed. A multi-tube heat recovery device, wherein an intermediate tube is disposed between the tubes, and the intermediate tube is fixed to the inner surface of the outer tube to form a passage for a cooling medium. A second intermediate cylinder that is fixed to the outer surface of the inner cylinder and forms a passage for the cooling medium is provided. The second intermediate cylinder and the intermediate cylinder are communicated with each other so that the cooling medium can flow therethrough, and are surrounded by both intermediate cylinders. The multi-tube heat recovery device according to claim 1, wherein an exhaust gas flow path is formed. The multi-tube heat recovery device according to claim 1, wherein at least the intermediate tube is provided with irregularities. The multi-pipe heat recovery device according to claim 1, 2 or 3, wherein the exhaust gas purifier and / or the silencer are integrally formed.

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