JPH1054230A - Exhaust gas heat recovery device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To absorb heat from exhaust gas when the water temperature or oil temperature of the engine is low, and to cut off the heat absorption from the exhaust gas when the water temperature and oil temperature of the engine are sufficiently high. SOLUTION: An exhaust gas heat recovery apparatus 10 of the present invention is provided with an exhaust pipe 11 inside an outer pipe 14 with a gap 16 between an outer pipe 14 and an inner wall 15 of the outer pipe 14. Tauchi tube 1
7, a communication part 29 provided on the upstream side in the flow direction of the exhaust gas to communicate the gap 16 with the inside of the inner pipe, and to allow the exhaust gas to flow into the gap 16; When the exhaust gas is lower than a predetermined temperature, the gap 16 communicates with the inside of the inner pipe 17 when the exhaust gas is lower than a predetermined temperature. There is an opening / closing section 30 that is cut off from the inside of the pipe 17 and shuts off the gap 16 and the inside 28 of the inner pipe 17 again when the temperature of the cooling water becomes higher than a sufficiently high predetermined temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas heat recovery apparatus for absorbing heat of exhaust gas flowing inside an exhaust pipe for a vehicle into engine cooling water.

[0002]

2. Description of the Related Art When an engine of an automobile is started, the temperature of the cooling water of the engine and the temperature of the engine oil are low, so that the oil viscosity at the sliding portion inside the engine is high and the friction loss is large. Therefore, since a large amount of fuel is required to obtain sufficient power, it is necessary to raise the water temperature and oil temperature of the engine at an early stage.

[0003] Further, when the outside air temperature is low in a cold region or in winter, the amount of heat required for heating the vehicle interior cannot be sufficiently obtained from the engine cooling water.

In order to cope with this, a passage for cooling water is formed around the exhaust pipe, which becomes hot, and in the wall of the exhaust pipe, and heat from exhaust gas discharged from the engine is absorbed by the engine cooling water. It has been proposed. In such a structure, the surface temperature of the exhaust pipe is about 400 in a normal running state.
Since the temperature is in the range of about 600 ° C. to about 600 ° C., a large amount of heat of the exhaust gas is absorbed by the low-temperature cooling water flowing in the cooling water passage formed on the wall surface of the exhaust pipe, and as a result, the temperature of the cooling water increases quickly.

[0005] On the other hand, in order to prevent overheating due to boiling of the cooling water and to prevent burning in the sliding portion of the engine due to a high temperature of the engine oil, it is necessary to keep the temperature of the engine cooling water and the engine oil at appropriate temperatures. .

However, in the structure in which the cooling water flowing in the cooling water passage formed in the wall surface of the exhaust pipe absorbs heat from the exhaust gas, even if the cooling water temperature becomes as high as about 100.degree. The large temperature difference between this and will cause a large amount of heat to be absorbed. For this reason, when the cooling water temperature becomes sufficiently high, it is necessary to suppress heat absorption from the exhaust pipe surface, and such an example is shown in FIGS. 12 and 13.

FIG. 12 shows a first exhaust pipe 3 provided with a cooling water passage 2 for absorbing heat of exhaust gas on the surface of the exhaust pipe 1 and a second exhaust pipe 3 provided with no cooling water passage. A structure is shown in which the exhaust gas is divided into an exhaust pipe 4 and an exhaust valve 6 for switching the flow of exhaust gas by an external controller 5 is provided in a divided portion between the first exhaust pipe 3 and the second exhaust pipe 4.

FIG. 13 shows a part of an exhaust manifold 7 described in Japanese Utility Model Laid-Open Publication No. Sho 62-12730.
In this exhaust manifold 7, a water jacket 9 in which cooling water flows is formed inside a wall surface 8 of the exhaust manifold 7, and the exhaust manifold 7 is formed.
The structure is such that a control valve is provided in a cooling water passage to the water jacket 9 in the inside.

[0009]

In the exhaust gas heat recovery structure shown in FIG. 12, the exhaust pipe 1 is formed as a double of the first exhaust pipe 3 and the second exhaust pipe 4. , 4
A lot of space is required in the engine room and at the bottom of the vehicle to install the vehicle.

Further, the exhaust valve 6 for exhaust gas must have a structure in which exhaust gas does not leak from the inside of the exhaust pipe 1, and must be resistant to high-temperature exhaust gas. Becomes

Further, even when the temperature of the cooling water becomes high and the flow of the exhaust gas to the first exhaust pipe 3 is shut off by the exhaust valve 6, the flow of the exhaust gas and the Due to the conduction from the high-temperature second exhaust pipe 4 flowing, the surface temperature is increased, and in addition to the double exhaust pipe surface area, the amount of heat discharged from the exhaust pipe surface into the engine room increases. As a result, the temperature of parts constituting the engine room and parts installed in the engine room rises.

In the exhaust gas heat recovery structure shown in FIG. 13 in which a water jacket 9 is formed inside the wall surface 8 of the exhaust pipe, the exhaust gas temperature is highest immediately after the engine exit, so that the exhaust gas is absorbed into the cooling water. The heat generated is large and the cooling water temperature rises early. On the other hand, when the cooling water temperature is sufficiently high, the cooling water flowing into the water jacket 9 in the exhaust manifold 7 is stopped by the control valve, but the cooling water remaining in the water jacket 9 is removed from the exhaust manifold 7. Due to the high-temperature exhaust gas flowing through the gas, the temperature rises further, causing the internal pressure to rise due to boiling.

For this reason, some structures have been proposed in which the cooling water is withdrawn from the water jacket 9 or the cooling water piping while the flow of the cooling water is stopped, but all of these structures are complicated and expensive. .

In addition, Japanese Patent Application Laid-Open No. Hei 1-35164 discloses a method in which a power generating element is attached to the surface of an exhaust pipe to absorb energy as electricity from a high-temperature exhaust pipe. Can not get enough electricity to raise the power.

In consideration of the above circumstances, the present invention absorbs heat from exhaust gas when the water temperature or oil temperature of the engine is low,
Cooling water at a site that raises the engine water temperature and oil temperature early, shuts off heat absorption from exhaust gas when the engine water temperature and oil temperature are sufficiently high, and absorbs heat from exhaust gas. It is an object of the present invention to provide an exhaust gas heat recovery device that prevents boiling of gas.

[0016]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to claim 1 includes an exhaust pipe through which exhaust gas from an engine flows, and an exhaust pipe wound around the exhaust pipe.
A heat receiving pipe through which cooling water for cooling the engine flows, wherein the heat of the exhaust gas flowing in the exhaust pipe is absorbed by the cooling water in the heat receiving pipe. A pipe and an inner pipe disposed inside the outer pipe with a gap between the inner pipe and the inner wall of the outer pipe are formed in a double structure, and the inner pipe is located on the upstream side in the exhaust gas flow direction. A communication portion that communicates with the gap and the inside of the inner pipe and that allows exhaust gas to flow into the gap; and a communication portion that is provided on the downstream side in a flow direction of exhaust gas and has a gap with the gap when the exhaust gas is lower than a predetermined temperature. The inside of the inner pipe is shut off, and when the exhaust gas becomes higher than a predetermined temperature, the gap communicates with the inside of the inner pipe. Having an opening and closing part for shutting off the gap and the inside of the inner pipe, To have.

In this exhaust gas heat recovery apparatus, when the temperature of the exhaust gas is lower than a predetermined temperature at the time of starting the engine or the like, the gap between the inner pipe and the outer pipe and the inside of the inner pipe are cut off to exhaust gas to the gap. Shut off gas flow. This allows the cooling water to flow the exhaust gas to a catalyst or the like disposed downstream in the flow direction of the exhaust gas without recovering the heat of the exhaust gas. As a result, the temperature of the exhaust gas can be raised early. For example, when the catalyst is arranged on the downstream side in the flow direction of the exhaust gas, the catalyst can be activated early.

When the temperature of the exhaust gas becomes higher than a predetermined temperature, the opening / closing portion communicates the gap with the inside of the inner pipe. As a result, the exhaust gas flows into the gap from the communicating portion, and the temperature of the outer tube rises due to the heat of the exhaust gas. When the temperature of the outer tube rises, its surface temperature rises, so that the temperature of the heat receiving pipe wound around the outer tube also rises, and the temperature of the cooling water flowing inside rises. Therefore, the temperature of the cooling water can be raised early. Also, when the temperature of the cooling water becomes equal to or higher than a sufficiently high predetermined temperature, the opening / closing section shuts off the gap between the inside of the inner pipe and stops the flow of exhaust gas into the gap. As a result, since no exhaust gas flows into the gap, the surface temperature of the outer tube is reduced, and the heat transfer from the outer tube to the cooling water is reduced, so that an excessive rise in the temperature of the cooling water can be suppressed.

Further, in the present invention, since the cooling water always flows through the heat receiving pipe, the cooling water does not stay in the heat receiving pipe, and the heat receiving pipe is damaged due to boiling caused by the cooling water remaining in the heat receiving pipe. Is prevented.

According to a second aspect of the present invention, there is provided the exhaust gas heat recovery apparatus according to the first aspect, wherein the exhaust pipe is provided between an engine and a catalyst for purifying exhaust gas from the engine. Are provided on the heat receiving pipe side and the catalyst side, respectively, and have first and second expandable portions that can expand and contract in the axial direction of the outer tube, and the opening and closing portion of the inner tube controls the temperature and cooling of the exhaust gas. Exhaust gas temperature detection that is disposed near the inlet of exhaust gas to the catalyst and detects the temperature of exhaust gas by opening and closing the gap and the inside of the inner tube by contacting and separating with the inner wall of the outer tube according to the temperature of water Means, cooling water temperature detecting means arranged downstream of the heat receiving pipe in the flow direction of the cooling water to detect the temperature of the cooling water in the heat receiving pipe, and connecting the first and second telescopic portions to the outer pipe. The inner wall of the outer pipe is connected to the opening / closing part of the inner pipe by A closing drive unit for opening and closing between the interior of the inner tube and the gap is based on the detection result of said coolant temperature detecting means and the exhaust gas temperature detecting means,
Activating the opening / closing drive means, and when the exhaust gas temperature is lower than the activation temperature of the catalyst, causes the inner wall of the outer pipe to abut against the opening / closing section to shut off the gap from the inside of the inner pipe, When the temperature is higher than the activation temperature of the catalyst, the inner wall of the outer tube is separated from the opening / closing portion to communicate the gap with the inside of the inner tube, and the temperature of the cooling water is higher than a predetermined temperature. When the height of the inner tube is increased, the inner wall of the outer tube is brought into contact with the opening / closing portion to control the gap and the inside of the inner tube.

In this exhaust gas heat recovery apparatus, when the exhaust gas is lower than a predetermined temperature at the time of starting the engine or the like, this temperature is detected by the exhaust gas temperature detecting means. Based on this result, the control means drives the opening / closing drive unit,
The first expandable portion is contracted and the second expandable portion is expanded, and the inner wall of the outer tube is brought into contact with the opening / closing portion to block the gap from the inside of the inner tube. Therefore, the flow of the exhaust gas into the gap is blocked, so that the cooling water does not recover the heat of the exhaust gas, and the exhaust gas flows to the catalyst. As a result, the heat of the exhaust gas is not taken away by others, so that the temperature of the exhaust gas can be raised at an early stage, and the catalyst can be quickly activated.

When the temperature of the exhaust gas becomes higher than the activation temperature of the catalyst, the control means drives the opening / closing drive section to extend the first expansion / contraction section, and contracts the second expansion / contraction section to contact the inner wall of the outer tube. Open between the opening and closing part. Therefore, the exhaust gas flows from the communicating portion into the gap, and the temperature of the outer tube rises due to the heat of the exhaust gas. When the temperature of the outer tube increases, the surface temperature increases, so that the temperature of the heat receiving pipe wound around the outer tube increases, and the temperature of the cooling water flowing in the heat receiving pipe increases. Therefore, the temperature of the cooling water can be raised early.

When the temperature of the cooling water is detected by the cooling water temperature detecting means and the detected result becomes higher than a predetermined temperature, the control means drives the opening / closing drive section to contract the first expansion / contraction section. The inner wall of the outer tube is brought into contact with the opening / closing portion by extending the second expandable / contracting portion, thereby blocking the gap from the inside of the inner tube. Therefore, the flow of the exhaust gas into the gap is stopped. As a result, the surface temperature of the outer tube is reduced and the heat transfer from the outer tube to the cooling water is reduced, so that an excessive rise in the cooling water temperature can be suppressed.

According to a third aspect of the present invention, there is provided the exhaust gas heat recovery apparatus according to the first aspect, wherein the exhaust pipe is disposed downstream of a catalyst for purifying exhaust gas from the engine in the exhaust gas flow direction, The heat receiving pipe is wound around the entire area in the axial direction of the exhaust pipe, and when the exhaust gas is lower than a predetermined temperature, the opening / closing section separates from the inner wall of the outer pipe to communicate the gap with the inside of the inner pipe. When the exhaust gas becomes higher than a predetermined temperature, the exhaust gas thermally expands and comes into close contact with the inner wall of the outer tube to shut off the gap from the inside of the inner tube.

In this exhaust gas heat recovery apparatus, when the exhaust gas from the engine is lower than a predetermined temperature, the opening / closing portion is separated from the inner wall of the outer tube to communicate the gap with the inside of the inner tube.
For this reason, the temperature of the outer tube rises due to the heat of the exhaust gas, and the surface temperature rises. As a result, heat is transmitted to the cooling water in the heat receiving pipe wound around the outer tube, and the temperature of the cooling water rises early. In this case, since the heat receiving pipe is wound around the entire area in the axial direction of the exhaust pipe, the amount of heat transferred from the exhaust gas to the cooling water increases, and the cooling water temperature is promptly increased.

When the temperature of the exhaust gas rises, the opening / closing section thermally expands and comes into close contact with the inner wall of the outer tube to shut off the gap from the inside of the inner tube. For this reason, the flow of the exhaust gas into the gap is stopped, the temperature of the outer pipe is reduced, the amount of heat transferred to the cooling water flowing in the heat receiving pipe is reduced, and an excessive rise in the temperature of the cooling water is suppressed.

[0027] The invention of claim 4 is the invention of claims 1 to 3.
The exhaust gas heat recovery device according to any one of the above,
The heat receiving pipe branches off from the part wrapped around the exhaust pipe in the flow direction of the cooling water into a main body passage and a bypass passage branched from the main body passage and again communicating with the main body passage. When a cooling water temperature is higher than a predetermined temperature at a branch portion between the main body passage and the bypass passage, the cooling water is guided into the bypass passage and flows into the heat exchanger, and the cooling water temperature is reduced. A valve for guiding cooling water into the main body passage when the temperature is lower than a predetermined temperature.

In this exhaust gas heat recovery apparatus, when the temperature of the cooling water raised by the heat of the exhaust gas becomes higher than a predetermined temperature which is sufficiently high, the valve body operates to guide the cooling water into the bypass passage to exchange heat. Flow into the vessel and release the heat of the cooling water to the outside air. When the cooling water temperature is lower than a sufficiently high predetermined temperature, the valve guides the cooling water into the main body passage.

The invention according to claim 5 is the invention according to claims 1 to 4.
The exhaust gas heat recovery device according to any one of the above,
An upstream side of the inner pipe is held on an inner wall of the outer pipe via a plurality of inner pipe holding members, and the communicating portion is provided between the plurality of inner pipe holding members.

In this exhaust gas heat recovery device, when the exhaust gas from the engine starts flowing in the exhaust pipe, the exhaust gas is
It flows into the gap through the communicating portion and flows into the inner pipe. In this case, when the opening / closing portion is in contact with the inner wall of the outer pipe to block the gap from the inside of the inner pipe, the exhaust gas flowing into the gap does not flow, and the exhaust gas that has flowed first does not flow. It stays in the gap. Also, the exhaust gas flowing into the inner pipe flows downstream as it is.

When the opening / closing part is separated from the inner wall of the outer tube, the gap communicates with the inside of the inner tube, so that the exhaust gas flowing into the gap flows into the inner tube, and the exhaust gas flows into the gap. It flows in from the communication part.

The invention of claim 6 is the first to fifth aspects of the present invention.
The exhaust gas heat recovery device according to any one of the above,
The opening / closing portion is formed of a bellows provided on the downstream side of the inner pipe and capable of extending and contracting in the axial direction of the inner pipe, and a downstream end portion of the bellows has a contact surface capable of closely contacting the inner wall of the outer pipe. It is characterized by having.

In this exhaust gas heat recovery apparatus, when the tip of the opening / closing section comes into contact with the inner wall of the outer tube, for example, the first expanding / contracting section is contracted by the opening / closing drive section, and the second expanding / contracting section is extended to extend the outside. When the tip of the opening / closing portion comes into contact with the inner wall of the tube, the bellows contracts and comes into close contact with the inner wall of the outer tube. Thereby, the gap and the inside of the inner pipe can be reliably shut off.

According to a seventh aspect of the present invention, in the first aspect, the insertion portion is formed between a plurality of inner tube holding members for holding the upstream side of the inner tube on the inner wall of the outer tube. The opening / closing part is provided on the downstream side of the inner pipe and is made of a bellows which can be extended and contracted in the axial direction of the inner pipe, and the downstream end of the bellows has a contact surface which can be in close contact with the inner wall of the outer pipe. Wherein the first and second extendable portions are formed in a flexible tube structure from a bellows portion which is extendable and contractible in the axial direction of the outer tube, and an extendable outer plate which covers the bellows portion, and the opening / closing drive portion is provided. A supporting member fixed to the outer periphery on the downstream side of the outer tube,
And a drive unit for driving the support member in the axial direction of the outer tube.

In this exhaust gas heat recovery apparatus, the inner wall of the outer tube comes into contact with the tip of the opening / closing section by contracting the first expanding / contracting section and expanding the second expanding / contracting section. In this case, the opening / closing portion is made of a bellows, and the tip of the bellows has a contact surface capable of closely contacting the inner wall of the outer tube, so that the gap and the inside of the inner tube can be reliably shut off. it can.

Further, the inner wall of the outer tube is separated from the contact surface of the opening / closing part by the first expanding part expanding and the second expanding part contracting.

The invention of claim 8 is the first to seventh aspects of the present invention.
The exhaust gas heat recovery device according to any one of the above,
A second inner pipe having the same material, the same thickness, and the same amount of expansion and contraction as the opening / closing section is provided inside the opening / closing section.

In the exhaust gas heat recovery apparatus, when the temperature of the exhaust gas is low, the temperature of the exhaust gas at the opening / closing section can be prevented from lowering, and the temperature of the exhaust gas can be increased quickly.

[0039]

According to the first aspect of the present invention, when the cooling water temperature or the oil temperature of the engine is low, the heat from the exhaust gas can be absorbed and the engine water temperature can be raised at an early stage. When the oil temperature becomes sufficiently high, absorption of heat from the exhaust gas is stopped, and cooling water does not stagnate in the heat receiving pipe, so that damage due to boiling of the cooling water in the portion where the cooling water flows can be prevented. it can.

According to the second aspect of the invention, in addition to the effect of the first aspect, the exhaust pipe is disposed between the engine and the catalyst, and when the temperature of the exhaust gas is lower than the activation temperature of the catalyst. When the temperature of the exhaust gas is higher than the activation temperature of the catalyst without transferring the heat of the exhaust gas to the cooling water, heat is transferred to the cooling water. It can be activated early.

If the temperature of the cooling water becomes too high,
Since the heat transfer from the exhaust gas to the cooling water is reduced, an excessive rise in the temperature of the cooling water can be suppressed.

According to the third aspect of the invention, in addition to the effect of the first aspect, the heat transfer pipe is wound around the entire area of the exhaust pipe in the axial direction. And the early rise of the cooling water temperature can be promoted.

According to the fourth aspect of the present invention, in addition to the effect of any one of the first to third aspects, when the temperature of the cooling water becomes excessively high, the cooling water is supplied to the bypass passage. Since the coolant flows and the heat of the coolant is released to the outside air by the heat exchanger, the coolant of the engine can be kept at a predetermined temperature or lower.

According to the fifth aspect of the present invention, in addition to the effects of the first aspect of the present invention, the inner pipe is formed on the inner wall of the outer pipe by a plurality of inner pipe holding members. By holding the inner tube, the inner tube can be reliably held on the inner wall of the outer tube.

According to the sixth aspect of the present invention, in addition to the effects of the first aspect of the present invention, since the opening and closing portion is formed of a bellows, the opening and closing portion is in close contact with the inner wall of the outer tube. When the inner wall of the outer tube comes into contact with the opening / closing part, the gap can be reliably shut off from the inside of the inner tube by contact.
The bellows can absorb the impact at the time of contact.

According to the seventh aspect of the present invention, in addition to the effect of the first aspect of the present invention, the opening / closing portion is made of a bellows, and a contact surface following the inner wall of the outer tube is provided at the tip of the bellows. When the inner wall of the outer tube is in contact with the contact surface, the gap can be reliably shut off from the inside of the inner tube.

According to the invention of claim 8, in addition to the effect of the invention of any one of claims 1 to 7, in addition to the provision of the second inner pipe, the exhaust gas can be opened and closed. This prevents the exhaust gas from directly touching, thereby preventing the temperature of the exhaust gas from lowering and promoting the early temperature rise of the exhaust gas.

[0048]

Embodiments of an exhaust gas heat recovery apparatus according to the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 to 5 show an exhaust gas heat recovery apparatus 10 according to a first embodiment.
Is shown. As shown in FIG. 1, this exhaust gas heat recovery device 1
Numeral 0 denotes an exhaust pipe 11 through which exhaust gas flows from the engine, and a heat receiving pipe 12 wound around the exhaust pipe 10 and through which cooling water for cooling the engine flows. Heat is heat receiving pipe 1
2 to be absorbed by the cooling water.

As shown in FIG. 2, the exhaust pipe 11 is provided between the engine and a catalyst 13 for purifying exhaust gas from the engine, and includes an outer pipe 14 and an inner wall 15 of the outer pipe 14.
And the inner tube 17 disposed inside the outer tube with a gap 16 between the two. Since the outer pipe 14 and the inner pipe 17 are exposed to high-temperature exhaust gas, it is necessary to prevent deterioration due to oxidation and corrosion. Therefore, the outer pipe 14 and the inner pipe 17 are formed using a stainless steel material. ), And the outer tube 14 is formed to be thick (for example, 1.2 to 3 mm).

The outer pipe 14 has an upstream outer pipe 18 on the engine side.
And a downstream outer tube 21 having one side connected to the upstream outer tube via the flange portion 19 and the other side connected to the catalyst 13.

The upstream outer tube 18 has a first expandable portion 23 formed on the winding portion 22 side of the heat receiving pipe 12, and a second expandable portion 24 formed on the downstream outer tube 21 on the catalyst 13 side. I have. These first and second telescoping portions 23 and 24 are formed by a telescopic bellows 25 formed by waving a thin plate and a telescopic outer blade 26 that covers the outside of the bellows 25. For this reason, the first and second telescopic parts 2
When 3, 3 expands and contracts, the flange portion 1 of the upstream outer pipe 18
The moving outer pipe 27 on the 9 side and the flange section 19 side of the downstream outer pipe 21 move along the axial direction of the exhaust pipe 11. Further, an inner pipe 17 is disposed inside the upstream outer pipe 18 with a predetermined gap 16 between the inner pipe 18 and the inner wall 18a of the upstream outer pipe 18.

The inner pipe 17 is provided on the upstream side in the flow direction of the exhaust gas and communicates with the gap 16 and the inside 28 of the inner pipe 17 to communicate the exhaust gas into the gap. When the exhaust gas is lower than a predetermined temperature, the gap 16 communicates with the inside 28 of the inner pipe 17, and when the exhaust gas becomes higher than a predetermined temperature, the gap 16 is provided.
And the inside 28 of the inner pipe 17 are shut off, and when the temperature of the cooling water becomes higher than a predetermined temperature, the gap 16 and the inside 28 of the inner pipe 17 are shut off again.

A plurality of inner tube holding members 31 are welded and fixed at predetermined intervals in the circumferential direction of the inner tube at the upstream end of the inner tube 17 in the exhaust gas flow direction. This inner tube holding member 3
1 is fixed to the inner wall of the outer tube, thereby holding the upstream end of the inner tube 17 on the inner wall 14 a of the outer tube 14. And
The communicating portion 29 is provided between the plurality of inner tube holding members 31. Exhaust gas from the engine flows into the gap 16 from the communication portion 29.

The opening / closing section 30 provided on the downstream side of the inner pipe 17 is provided with an elastic bellows 3 having a thin plate formed in a wavy shape.
2 are formed. The tip of the bellows 32 is provided with a contact surface 33 that can be in close contact with the inner wall 14a of the movable outer tube 14. The contact surface 33 is formed in accordance with the shape of the inner wall of the movable outer tube 27, and the bellows 32 expands toward the inner wall side of the movable outer tube 27 due to thermal expansion.
3 comes into close contact with the inner wall of the movable outer tube 27.

A plurality of meshes 34 are provided at the downstream end of the inner pipe 17. This mesh 34
Holds the downstream end of the inner pipe 17 on the inner wall 14 a of the outer pipe 14. For this reason, the inner tube 17 is prevented from shifting in the radial direction due to vibration. This mesh 34 is formed by being woven with metal fibers.

The opening and closing of the inner wall 27a of the movable outer tube 27 by expanding and contracting the first expansion and contraction portion 23 and the second expansion and contraction portion 24 with respect to the opening and closing portion 30 at the downstream end of the inner tube 17. The drive unit 35 is provided on the outer periphery of the movable outer tube 27. The opening / closing drive unit 35 includes a support member 36 fixed to the flange 19 of the movable outer tube 27, and a drive unit 37 that drives the support member 36 along the axial direction of the movable outer tube 27.

On the other hand, the heat receiving pipe 12 is
At the downstream side in the flow direction of the cooling water from the winding portion 22, the main body passage 38 and a bypass passage 39 that branches off from the main body passage 38 and communicates with the main body passage 38 again. A heat exchanger 40 is provided in the middle of the bypass passage 39, and a thermostat (valve element) 41 is provided at a branch portion between the main body passage 38 and the bypass passage 39. The heat exchanger 40 is of a radiator type having small louver type fins or a disk-shaped fin mounted on a pipe.

The thermostat 42 guides the cooling water into the bypass passage 39 when the temperature of the cooling water is higher than a predetermined temperature, and sends the cooling water to the main body passage when the temperature of the cooling water is lower than the predetermined temperature. Lead into 38. Further, a water temperature sensor 42 as cooling water temperature detecting means for detecting the temperature of the cooling water is attached between the winding part 22 of the heat receiving pipe 12 around the upstream outer pipe 18 and the thermostat 41. The water temperature sensor 42 includes a control device (control means) 4
3 is connected.

In addition to the water temperature sensor 42, an exhaust temperature sensor 44 attached to the outer periphery of the downstream outer pipe 21 on the catalyst 13 side to detect the temperature of exhaust gas is connected to the control device 43. Further, a drive unit 37 is connected to the control device 43. When the exhaust gas temperature is lower than the activation temperature of the catalyst 13, the driving unit 37 is operated to
7 is brought into contact with the contact surface 33 of the opening / closing section 30 to shut off the gap 16 and the inside of the inner pipe 17. When the exhaust gas temperature becomes higher than the activation temperature of the catalyst 13, the movable outer pipe 27
The inner wall 27a is separated from the contact surface 33 of the opening / closing section 30 to allow communication between the gap 16 and the inner pipe 17. Further, when the cooling water temperature becomes higher than a predetermined temperature, the inner wall 27a of the movable outer tube 27 is brought into contact with the contact surface 33 of the opening / closing section 30 to shut off the gap 16 from the inside of the inner tube 17.

Next, the operation of the exhaust gas heat recovery apparatus 10 of the above embodiment will be described with reference to the control flowchart of the control apparatus shown in FIG.

First, the start of the engine will be described.

Except immediately after the engine is stopped, the temperatures of the outer pipe 14, the inner pipe 17, and the heat receiving pipe 12 of the exhaust pipe 11 are the same as the outside air temperature. After starting the engine, the control valve is closed in step S1. That is, as shown in FIG. 5, the movable outer tube 27 is positioned on the upstream side in the exhaust gas flow direction by the opening / closing drive unit 35, and the bellows 32 of the opening / closing unit 30 is moved.
The inner wall 27a of the movable outer tube 27 is in close contact with the abutting surface 33, and the gap 16 and the inside 28 of the inner tube 17 are shut off.

In this state, the exhaust gas from the engine flows through the inner pipe 17 to the catalyst 13 side, and a part of the exhaust gas flows from the communicating portion 29 to the inner pipe 17 and the inner wall of the outer pipe 14. It flows into the gap 16 between them. At this time, since the inner wall of the movable outer tube 27 is in close contact with the contact surface 33, the exhaust gas flowing into the gap 16 does not flow to the catalyst 13 side but stays in the gap 16. In addition, inner pipe 1
The inner pipe 17 is heated by the heat of the exhaust gas passing through the inside 7.

In this case, in this embodiment, since the inner tube 17 is formed of a thin plate, the heat capacity of the inner tube is small, and the temperature of the inner tube 17 rises early. Therefore, the amount of heat transfer from the exhaust gas to the inner pipe 17 is suppressed low, and a decrease in the temperature of the exhaust gas is suppressed. As a result, since the temperature of the exhaust gas flowing into the catalyst 13 does not decrease much, as shown in FIG. 7B, it is possible to raise the temperature of the exhaust gas earlier to the activation temperature of the catalyst as compared with the conventional case. it can.

Next, in step S2, it is determined whether or not the exhaust gas has become higher than the activation temperature of the catalyst. If the exhaust gas is not higher than the activation temperature of the catalyst, step S1
Is continuously executed. When the exhaust gas becomes higher than the activation temperature of the catalyst, the control valve is opened in step S3.
That is, the movable outer pipe 27 is moved to the downstream side in the flow direction of the exhaust gas by the opening / closing drive unit 35 so that the inner wall 27 a of the movable outer pipe 27 is separated from the contact surface 33, and the gap 16 and the inside 28 of the inner pipe 17 are separated. Is communicated.

As a result, a part of the exhaust gas flowing into the gap 16 from the communication portion 29 is
7 and flows into the inside of the inner tube 17. Therefore, the outer pipe 14 rises due to the heat of the exhaust gas, and the wall temperature of the outer pipe 14 rises from 400 ° C. to about 500 ° C. Outer tube 14
When the wall temperature of the heat receiving pipe 12 rises,
The heat of the outer tube 14 is transmitted to the cooling water flowing inside, and the temperature of the cooling water rises. As a result, as shown in FIG. 7A, the temperature of the cooling water rises earlier than in the prior art.

In this case, since the cooling water of the engine always flows through the heat receiving pipe 12 connected to the cooling water passage of the engine, the cooling water flows through the heat receiving pipe from the outer pipe 14 of the exhaust pipe 11 having a high temperature. A large amount of heat is transmitted to the cooling water and the temperature of the cooling water rises early. At this time, since the thermostat 41 installed on the downstream side of the heat receiving pipe 12 has a sufficiently high valve opening temperature, the cooling water received by the heat receiving pipe 12 flows to the engine through the main body passage 38. The water flows into the engine while maintaining the water temperature without releasing heat at 40 in the heat exchanger. As a result, heat is transferred from the high-temperature cooling water to the engine oil, the oil temperature of the engine also rises early, the oil viscosity at the sliding portion inside the engine decreases, friction loss is reduced, and fuel efficiency is improved. Further, even in a situation where the outside air temperature is low such as in a cold region or winter season and heating is required in the vehicle cabin, the amount of heat required for heating can be sufficiently obtained from the engine cooling water.

Next, at step S4, it is determined whether or not the temperature of the cooling water in the heat receiving pipe 12 is higher than the operating temperature (valve opening temperature) of the thermostat 41. When the temperature of the cooling water in the heat receiving pipe 12 is higher than the valve opening temperature of the thermostat 41, the open / close drive unit 35 is operated in step S5 to move the movable outer pipe 27 to the upstream side in the flow direction of the exhaust gas. The inner wall 27 of the movable outer tube 27 is provided on the contact surface 33 of the opening / closing section 30.
a is brought into close contact. As a result, the flow of the exhaust gas in the gap 16 is stopped. At the same time, the thermostat 41 operates to flow the cooling water into the bypass passage 39, and heat is released by the heat exchanger to suppress an excessive rise in the temperature of the cooling water.

If the temperature of the cooling water in the heat receiving pipe 12 is lower than the operating temperature of the thermostat 41 in step S4, the temperature of the cooling water is set between the water jacket of the engine and the radiator in step S6. A thermostat, i.e., a valve that opens and closes according to the temperature of the cooling water to send only the cooling water having a predetermined temperature or less into the engine, and sends the cooling water having a predetermined temperature or less into the engine. It is determined whether it is high. If the temperature of the cooling water is higher than the thermostat operating temperature, step S5 is executed, and if the temperature of the cooling water is lower than the operating temperature of the thermostat 41, steps S2 and subsequent steps are executed again.

In the exhaust gas heat recovery apparatus according to the present embodiment, the cooling water temperature obtained from a water temperature sensor used for controlling the engine, which is usually installed near the thermostat disposed between the engine and the water jacket, is used as the thermostat 41. When the temperature becomes higher than the valve opening temperature, the moving outer pipe 27 of the exhaust pipe 11 moves to the upstream side as shown in FIG. 5 by the control device 43, and the contact surface 33 comes into contact with and closely contacts the inner wall 27a.
At this time, the exhaust gas stops flowing into the gap 16, so that the wall temperature of the outer pipe 14 of the exhaust pipe 11 becomes 150 ° C. to 200 ° C.
To about ℃. Therefore, the outer pipe 14 and the heat receiving pipe 1
2, the amount of heat received from the outer pipe 14, and eventually the exhaust gas to the cooling water in the heat receiving pipe 12 is reduced, and the rise in water temperature is suppressed. At this time, the amount of heat that is slightly absorbed due to the temperature difference between the outer pipe 14 and the heat receiving pipe 12 is released by the heat exchanger 40 installed downstream of the heat receiving pipe 12, so that the water temperature in the heat receiving pipe 12 rises. Is suppressed.

Further, in a situation where heating is not necessary in a vehicle compartment such as a hot spot or summertime, that is, when the heater switch is turned off, the temperature of exhaust gas flowing into the catalyst 13 is detected by the exhaust temperature sensor 44. When the temperature rises above the activation temperature,
The control by the control device 43 is stopped. For this reason, when the exhaust gas temperature becomes equal to or higher than the activation temperature of the catalyst 13, the gap 16
Exhaust gas flows into the inside, heat is transferred from the outer pipe 14 to the cooling water in the heat receiving pipe, and the water temperature rises.

On the other hand, when the exhaust gas temperature becomes sufficiently high,
The inner pipe 17 and the bellows 32, which are heated by the exhaust gas temperature and become high temperature, thermally expand and the contact surface 33 at the tip of the bellows 32 comes into close contact with the inner wall 27 a, so that the exhaust gas flowing through the gap 16 is shut off, and The temperature of the pipe 14 decreases, the amount of heat transferred to the cooling water in the heat receiving pipe 12 decreases, and the rise in water temperature is suppressed. As described above, by stopping the control by the control device 43, the power used for the control can be reduced, and the control device 4 can be controlled.
3 can be prevented from deteriorating.

In the exhaust gas heat recovery apparatus 10 of this embodiment, when the cooling water temperature is low at the time of starting the engine or the like, the heat of the exhaust gas is transferred to the cooling water in the heat receiving pipe wound around the exhaust pipe having the double structure. By transmitting the transmission, the water temperature of the engine can be raised early, as shown in FIG.

Further, in the exhaust gas heat recovery apparatus 10 of the present embodiment, since the cooling water flows in the heat receiving pipe, the temperature of the cooling water does not excessively rise and boil, so that the heat receiving pipe 12 is not damaged.

Further, the exhaust gas heat recovery apparatus 10 of the present embodiment
Since the heat of the exhaust gas flows through the catalyst 13 without being transmitted to the cooling water until the temperature of the exhaust gas reaches the activation temperature of the catalyst, as shown in FIG. And the temperature can be raised earlier than the activation temperature of the catalyst.

When the temperature of the exhaust gas becomes high during running in an urban area or at a high speed, the exhaust gas flowing into the gap 16 is controlled by the dual-structure exhaust pipe 11 regardless of whether the control device 43 controls or not. Because of the cutoff, the amount of heat released by the radiation and convection from the surface of the exhaust pipe 11 to the engine room is reduced, and the temperature rise of the components that make up the engine room and the components installed in the engine room is reduced. The risk of accelerating thermal deterioration can be prevented.

Second Embodiment Next, an exhaust gas heat recovery device 50 according to a second embodiment will be described.
This will be described with reference to FIGS. FIG. 8 is an external view of an exhaust gas heat recovery device 50 of the second embodiment, and FIG.
1 shows a cross-sectional view of a double-structured exhaust pipe. The same components as those described above are denoted by the same reference numerals in the drawings, and redundant description will be omitted.

The exhaust gas heat recovery device 50 of the present embodiment
The exhaust pipe 51 is disposed downstream of the catalyst 13 that purifies exhaust gas from the engine in the exhaust gas flow direction, and the heat receiving pipe 52 is wound around the entire exhaust pipe 51 in the axial direction.

As shown in FIG. 9, the exhaust pipe 51 of the present embodiment has a double structure including an outer pipe 53 and an inner pipe 55 provided with a gap 54 inside the outer pipe 53. Have been. The upstream side of the outer pipe 53 in the exhaust gas flow direction is connected to the catalyst 13 via a flange 56, and the downstream side is connected to a downstream outer pipe 58 via a flange 57. Inner tube 5
5 is a flange portion 5 having a plurality of inner pipe holding members 31 whose upstream end in the exhaust gas flow direction is the same as that of the first embodiment.
6 is held. A communication portion 63 is formed between the inner tube holding members 31 to communicate the gap 54 and the inside of the inner tube 55.

An opening / closing portion 59 is provided downstream of the inner tube 55. The opening / closing portion 59 is formed of a bellows 60 similar to the opening / closing portion 30 of the first embodiment. The distal end portion of the bellows 60 is provided with a contact surface 61 formed following the downstream inner wall 53 a of the outer tube 53. As shown in FIG. 10, the bellows 60 expands to the downstream side of the exhaust gas flow by thermal expansion, so that the contact surface 61 comes into close contact with the downstream inner wall 53 a of the outer pipe 53. .

The heat receiving pipe 52 of the present embodiment has the same configuration as that of the first embodiment on the downstream side in the flow direction of the cooling water from the winding portion 62 around the outer tube 53.

In the exhaust gas heat recovery apparatus 50 of this embodiment, when the exhaust gas temperature at the time of engine start is low, the contact surface 61 of the bellows 60 of the inner pipe 55 is separated from the downstream inner wall 53 a of the outer pipe 53. doing. Therefore, the gap 5
4 and the inside of the inner tube 55 are communicated. After passing through the catalyst, the exhaust gas from the engine flows into the exhaust pipe 51, flows through the inner pipe 55, flows into the downstream outer pipe, and
A part of the exhaust gas flows into the gap 54 from the communication portion 63, enters the inner pipe 55 again from between the contact surface 61 and the downstream inner wall 53 a of the outer pipe 53, and flows to the downstream outer pipe 58.

At this time, the wall temperature of the outer tube 53 rises due to the exhaust gas flowing into the gap 54, and transfers heat to the cooling water flowing through the winding portion 62 of the heat receiving pipe 52. For this reason, the cooling water rises early. Therefore, the heat receiving pipe 52
The temperature of the cooling water in the tank rises immediately after the engine is started by receiving heat from the exhaust pipe 51.

In this case, the temperature of the cooling water is
When the temperature becomes higher than the operating temperature, the cooling water flowing in the winding portion 63 of the heat receiving pipe 52 is guided into the bypass passage 39, flows into the heat exchanger 40, and releases heat to the outside.

When the exhaust gas temperature becomes sufficiently high, the inner pipe 55
Then, the bellows 60 on the downstream side of the inner pipe 55 expands due to the heat of the exhaust gas and extends toward the inner wall 53 a on the downstream side of the outer pipe 53.
Then, the contact surface 61 comes into close contact with the inner wall 53 a of the outer tube 53, and shuts off the gap 54 and the inside of the inner tube 55. As a result, the exhaust gas flowing into the gap 54 does not flow again into the inner pipe 55, so that the exhaust gas does not flow through the gap, heat transfer of the cooling water at the winding portion is reduced, and the water temperature rises. Is suppressed.

According to the exhaust gas heat recovery device 50 of the present embodiment, the winding portion 6 around the outer periphery of the outer tube 53 of the heat receiving pipe 52
Since the area of 2 is large, the cooling water temperature rises faster than in the first embodiment, and the cooling water temperature can be raised earlier.

Further, in this embodiment, since the exhaust pipe 51 is disposed behind the catalyst 13, it is not necessary to control the exhaust gas in accordance with the activation temperature of the catalyst 13. , A simple structure that does not require the second expandable portion.

Third Embodiment Next, an exhaust gas heat recovery apparatus 70 according to a third embodiment will be described with reference to FIG. FIG.
1 shows a cross section of the exhaust gas heat recovery device 70 of the third embodiment. Inside the bellows 32 behind the inner pipe 17 of the exhaust pipe 11 having a double structure, a second inner pipe 71 made of the same material and having the same thickness as the inner pipe 17 covers the bellows 32 so as to cover the bellows 32. The structure is welded and fixed to the pipe 17.

In the exhaust gas heat recovery apparatus 70 of this embodiment, the bellows 32 having a large area exposed to the exhaust gas is
Since the exhaust gas is prevented from escaping to the bellows 32 because it is covered with the thin second inner pipe 71, the temperature of the exhaust gas flowing into the catalyst can be quickly reduced when the temperature of the exhaust gas is low immediately after the start of the engine. Can be raised.

[Brief description of the drawings]

FIG. 1 is an external view showing a first embodiment of an exhaust gas heat recovery device according to the present invention.

FIG. 2 is a cross-sectional view showing the inside of the exhaust pipe of the first embodiment.

FIG. 3 is a view showing a holding structure of the inner pipe to the outer pipe in the exhaust pipe of the first embodiment, and is a view as seen in the direction of arrow P in FIG. 2;

FIG. 4 is a cross-sectional view showing a state in which the inner wall of the outer pipe is in close contact with the opening and closing part in the exhaust pipe of the first embodiment.

FIG. 5 is a cross-sectional view showing a state in which the bellows of the opening / closing section is expanded in the exhaust of the first embodiment.

FIG. 6 is a flowchart illustrating control of a control device of the exhaust gas heat recovery device of the first embodiment.

FIGS. 7A and 7B show a change in cooling water temperature and a change in exhaust gas temperature of the exhaust gas heat recovery device of the first embodiment, FIG. 7A is a diagram showing a rising curve of cooling water temperature with respect to time, and FIG. FIG. 4 is a diagram showing the temperature of exhaust gas with respect to FIG.

FIG. 8 is an external view showing a second embodiment of the exhaust gas heat recovery device according to the present invention.

FIG. 9 is a cross-sectional view showing the inside of an exhaust pipe according to a second embodiment.

FIG. 10 is a cross-sectional view showing a state in which the inner wall of the outer pipe is in close contact with the bellows in the exhaust pipe of the second embodiment.

FIG. 11 is an external view showing a third embodiment of the exhaust gas heat recovery device according to the present invention.

FIG. 12 is a schematic configuration diagram showing a conventional exhaust pipe.

FIG. 13 is a schematic configuration diagram showing another conventional exhaust pipe.

[Explanation of symbols]

 10, 50, 70 Exhaust gas heat recovery device 11, 51 Exhaust pipe 12, 52 Heat receiving pipe 13 Catalyst 14, 53 Outer pipe 15 Inner wall 16, 54 Gap 17, 55 Inner pipe 23 First telescopic part 24 Second telescopic part 28 Inside 29, 63 Communication part 30, 59 Opening / closing part 31 Inner tube holding member 32, 60 Bellows 33, 61 Contact surface 35 Opening / closing driving part 38 Main body passage 39 Bypass passage 40 Heat exchanger 41 Thermostat 42 Water temperature sensor 43 Control device 44 Exhaust temperature sensor 71 2nd inner tube

Claims (8)

[Claims] An exhaust pipe through which exhaust gas from an engine flows, and a heat receiving pipe wrapped around the exhaust pipe and through which cooling water for cooling the engine flows, wherein heat of the exhaust gas flowing through the exhaust pipe is provided. Is an exhaust gas heat recovery device that is absorbed by cooling water in a heat receiving pipe, wherein the exhaust pipe is disposed inside the outer pipe with a gap between the outer pipe and an inner wall of the outer pipe. A communication section through which the inner pipe is provided on the upstream side in the flow direction of the exhaust gas to communicate the gap and the inside of the inner pipe, and the exhaust gas flows into the gap. The exhaust pipe is provided on the downstream side in the flow direction of the exhaust gas to shut off the gap and the inside of the inner pipe when the exhaust gas is lower than a predetermined temperature, and to close the gap when the exhaust gas becomes higher than a predetermined temperature. Communicates with the inside of the pipe,
An exhaust gas heat recovery device, comprising: an opening / closing unit that shuts off the gap and the inside of the inner pipe again when the temperature of the cooling water becomes higher than a sufficiently high predetermined temperature. 2. The exhaust gas heat recovery apparatus according to claim 1, wherein the exhaust pipe is provided between an engine and a catalyst for purifying exhaust gas from the engine, and the outer pipe is on a side of the heat receiving pipe. And a first and a second expansion and contraction portion respectively provided on the catalyst side and capable of expanding and contracting in the axial direction of the outer tube, wherein the opening and closing portion of the inner tube is externally controlled by the temperature of the exhaust gas and the temperature of the cooling water. An exhaust gas temperature detecting unit that is disposed near the inlet of exhaust gas to the catalyst and detects the temperature of the exhaust gas by opening and closing the gap between the inside of the inner tube and the inner wall of the tube by contacting and separating from the inner wall of the tube; Cooling water temperature detecting means disposed downstream of the pipe in the flow direction of the cooling water to detect the temperature of the cooling water in the heat receiving pipe; and expanding and contracting the first and second expandable portions in the axial direction of the outer pipe. Then, the inner wall of the outer tube is brought into contact with and separated from the opening / closing portion of the inner tube, and And the opening and closing drive unit for opening and closing between the interior of the inner tube, on the basis of the detection result of said coolant temperature detecting means and the exhaust gas temperature detection means, by operating the opening and closing drive means,
When the temperature of the exhaust gas is lower than the activation temperature of the catalyst, the inner wall of the outer tube is brought into contact with the opening / closing portion to shut off the gap and the inside of the inner tube, and the temperature of the exhaust gas is higher than the activation temperature of the catalyst. When the temperature rises, the inner wall of the outer tube is separated from the opening / closing part to communicate the gap with the inside of the inner tube, and when the temperature of the cooling water becomes higher than a sufficiently high predetermined temperature, the inner wall of the outer tube is raised. Control means for contacting the opening / closing part to cut off the gap and the inside of the inner pipe. 3. The exhaust gas heat recovery device according to claim 1, wherein the exhaust pipe is disposed downstream of a catalyst for purifying exhaust gas from an engine in a flow direction of the exhaust gas, and the heat receiving pipe is connected to the exhaust pipe. When the exhaust gas is lower than a predetermined temperature, the opening / closing portion is separated from the inner wall of the outer pipe to communicate the gap with the inside of the inner pipe when the exhaust gas is lower than a predetermined temperature. An exhaust gas heat recovery device characterized in that when the temperature of the exhaust gas becomes higher than the temperature of the exhaust gas, it thermally expands and comes into close contact with the inner wall of the outer pipe to block the gap from the inside of the inner pipe. 4. The exhaust gas heat recovery apparatus according to claim 1, wherein the heat receiving pipe is provided on a downstream side in a flow direction of the cooling water from a portion wrapped around the exhaust pipe. Branching into a main body passage and a bypass passage branching from the main body passage and communicating with the main body passage again, a heat exchanger is provided in the middle of the bypass passage, and cooling is performed at a branch portion between the main body passage and the bypass passage. When the water temperature is higher than a sufficiently high predetermined temperature, the cooling water is guided into the bypass passage and flows into the heat exchanger, and when the cooling water temperature is lower than the sufficiently high predetermined temperature, the cooling water is guided into the main body passage. An exhaust gas heat recovery device provided with a valve element. 5. The exhaust gas heat recovery device according to claim 1, wherein an upstream side of the inner pipe is connected to an outer pipe of the outer pipe via a plurality of inner pipe holding members. An exhaust gas heat recovery device, which is held on an inner wall and between the plurality of inner tube holding members is the communication portion. 6. The exhaust gas heat recovery device according to claim 1, wherein the opening / closing portion is provided downstream of the inner pipe and extends in an axial direction of the inner pipe. An exhaust gas heat recovery apparatus comprising an expandable and contractable bellows, wherein a downstream end of the bellows has a contact surface capable of closely contacting an inner wall of an outer tube. 7. The invention according to claim 1, wherein the insertion portion is formed between a plurality of inner tube holding members for holding an upstream side of the inner tube on an inner wall of an outer tube, and the opening / closing portion is provided. A bellows provided on the downstream side of the inner tube and capable of extending and contracting in the axial direction of the inner tube, the downstream end of the bellows having a contact surface capable of closely contacting the inner wall of the outer tube; The first and second extendable portions are formed in a flexible tube structure from a bellows portion that can extend and contract in the axial direction of the outer tube and an extendable outer plate that covers the bellows portion. An exhaust gas heat recovery device comprising: a support member fixed to a side outer periphery; and a drive unit that drives the support member in an axial direction of an outer tube. 8. The exhaust gas heat recovery device according to claim 1, wherein the opening / closing portion has the same material, the same thickness, and the same amount of expansion and contraction inside the opening / closing portion. The second with
An exhaust gas heat recovery device characterized by having an inner pipe.