Exhaust heat recovery device

Abstract

An exhaust heat recovery device (1) comprises: a first flow path member (10) that has a first flow path in which exhaust gas flows; a second flow path member (20) that is adjacent to the first flow path member (10), that has a heat exchange part (30), and that has a second flow path; and a valve mechanism (40) that opens and closes the first flow path and that blocks or impedes the flow of the exhaust gas from the second flow path. The first flow path member (10) is provided, at at least a portion thereof upstream of the valve mechanism (40) in the flow direction of the exhaust gas, with a double wall part (19) having an inner wall part (17) that faces the first flow path and an outer wall part (18) that is positioned on the opposite side from the first flow path.

Description

Exhaust heat recovery device

[0001] The present invention relates to an exhaust heat recovery device.

[0002] JP2021-188567A discloses an exhaust heat recovery device having a first flow path member having a first flow path through which exhaust gas flows, a second flow path member provided adjacent to the first flow path and having a second flow path that bypasses the first flow path, and a heat exchange unit that exchanges heat between the exhaust gas and a refrigerant.

[0003] The exhaust heat recovery device described in JP2021-188567A has a butterfly valve that opens and closes the first flow path using a rotating shaft that is perpendicular to the flow direction of the exhaust gas in the first flow path, and a shutter unit that blocks the outlet from the second flow path, which is a bypass path, when the butterfly valve opens the first flow path, and opens the outlet when the butterfly valve blocks the first flow path, and is equipped with a valve mechanism that switches the flow path of the exhaust gas to the first flow path or the second flow path.

[0004] In the exhaust heat recovery device disclosed in JP2021-188567A, for example, when exhaust gas is diverted from the first flow path to the second flow path and heat exchange is performed in the heat exchange section, if the first flow path is blocked by a butterfly valve, the exhaust gas will remain in the blocked space created by the butterfly valve and the first flow path member and flow into the second flow path.

[0005] However, when the exhaust gas stagnates, the heat of the exhaust gas is conducted to the first flow path member and then released to the outside from the first flow path member, resulting in heat loss, which may decrease the temperature of the exhaust gas flowing through the heat exchange section and reduce the heat recovery efficiency.

[0006] An object of the present invention is to prevent a decrease in the temperature of exhaust gas flowing through a heat exchange section, and to prevent a decrease in heat recovery efficiency.

[0007] According to one aspect of the present invention, there is provided an exhaust heat recovery device that recovers heat from exhaust gases emitted from an engine by heat exchange with a fluid, the exhaust heat recovery device comprising: a first flow path member having a first flow path formed therein through which exhaust gases flow; a second flow path member provided adjacent to the first flow path member, having a second flow path formed therein that bypasses part of the first flow path and having a heat exchange section that exchanges heat between the exhaust gases flowing in the second flow path and the fluid; and a valve mechanism provided in the first flow path, wherein the valve mechanism opens the first flow path or closes the first flow path to guide the exhaust gases to the second flow path, and the first flow path member has a double wall portion, at least in a portion upstream of the valve mechanism in the flow direction of the exhaust gas, having an inner wall portion facing the first flow path and an outer wall portion located on the opposite side of the inner wall portion from the first flow path.

[0008] According to the present invention, it is possible to prevent a decrease in the temperature of the exhaust gas flowing through the heat exchange section, and to prevent a decrease in the heat recovery efficiency.

[0009] FIG. 1 is a perspective view illustrating an exhaust heat recovery device according to an embodiment of the present invention. FIG. 2 is a front view showing a portion of the exhaust heat recovery device according to the embodiment, with a cutaway view. FIG. 3 is a side view seen from the upstream side of a first flow path, illustrating the heat recovery state of the exhaust heat recovery device according to the embodiment. FIG. 4 is a perspective view illustrating a valve mechanism of the exhaust heat recovery device according to the embodiment. FIG. 5 is a front view showing a portion of the exhaust heat recovery device according to the embodiment, with a cutaway view. FIG. 6 is a side view seen from the upstream side of the first flow path, illustrating the heat non-recovery state of the exhaust heat recovery device according to the embodiment.

[0010] An exhaust heat recovery device 1 according to an embodiment of the present invention will be described below with reference to the drawings.

[0011] Fig. 1 is a perspective view illustrating an exhaust heat recovery device 1 according to an embodiment of the present invention. Fig. 2 is a front view showing a portion of the exhaust heat recovery device 1 in a cutaway state. Fig. 3 is a side view showing the heat recovery state of the exhaust heat recovery device 1 shown in Fig. 2 as viewed from the upstream side of a first flow path 14.

[0012] As shown in FIG. 1 , the exhaust heat recovery device 1 includes a first flow path member 10 , a second flow path member 20 , and a heat exchange section 30 .

[0013] The first flow path member 10 has a main body 11, a first inlet 12, and a first outlet 13. The main body 11 has a hollow structure, and a first flow path 14 through which exhaust gas flows is formed inside the main body 11.

[0014] The first inlet portion 12 is an opening on one side of the main body portion 11 and is connected to the flow path of exhaust gas from the engine. The first outlet portion 13 is an opening on the other side of the main body portion 11 and is connected to the flow path of exhaust gas. The first inlet portion 12 is located upstream of the first outlet portion 13 in the exhaust gas flow.

[0015] The main body 11 is formed with a first upstream opening 15 as an outlet through which exhaust gas flows from the first flow path 14 to the second flow path 24 (see Figure 2), and a first downstream opening 16 as an inlet through which exhaust gas flows from the second flow path 24 to the first flow path 14.

[0016] The first flow path member 10 includes a double wall portion 19 located upstream in the exhaust gas flow direction of a butterfly valve 41 ( FIG. 2 ) that opens and closes the first flow path 14. The double wall portion 19 has an inner wall portion 17 that faces the first flow path 14, and an outer wall portion 18 that is located on the opposite side of the inner wall portion 17 from the first flow path 14.

[0017] In this embodiment, the exhaust heat recovery device 1 includes an inner member 50 inside the first flow path member 10 that covers at least a part of the inner surface of the first flow path member 10 .

[0018] In this embodiment, the inner member 50 forms the inner wall portion 17, and the first flow path member 10 forms the outer wall portion 18. That is, the first flow path member 10 and the inner member 50 form a double wall portion 19.

[0019] The double wall portion 19 has a gap portion S1 between the inner wall portion 17 and the outer wall portion 18 , which is isolated from the first flow path 14 .

[0020] The inner member 50 has a joint portion 53 with the first flow path member 10 at a part of the upstream side or downstream side in the flow direction of the exhaust gas. In the present embodiment, the first flow path member 10 and the inner member 50 are connected by spot welding at the joint portion 53 located on the downstream side in the flow direction of the exhaust gas.

[0021] In the present embodiment, the inner member 50 has a first upright portion 51 that stands up toward the inside of the first flow path 14. The first upright portion 51 is located upstream of the first downstream opening 16 in the first flow path 14, and is formed across the first downstream opening 16 in a direction perpendicular to the flow direction of the exhaust gas.

[0022] The inner member 50 also has a second upright portion 52 that stands up toward the inside of the first flow path 14 on the inner surface opposite to the first upright portion 51. The second upright portion 52 is formed upstream of the butterfly valve 41 (valve body 43) when the valve mechanism 40 is in the heat recovery state, and is formed across a direction perpendicular to the flow direction of the exhaust gas.

[0023] The first upright portion 51 is formed so that its height H1 from the inner surface of the first flow path member 10 is larger than the gap D1 formed in the separation direction between the first downstream opening 16 and the valve mechanism 40 (shutter portion 42) when the valve mechanism 40 is in the heat non-recovery state (FIG. 5). Furthermore, the second upright portion 52 is formed so that its height H2 from the inner surface of the first flow path member 10 is larger than the gap D2 in the separation direction between the inner surface of the first flow path member 10 and the valve mechanism 40 (valve body 43) when the valve mechanism 40 is in the heat recovery state (FIG. 2).

[0024] The second flow path member 20 is provided adjacent to the first flow path member 10. The second flow path member 20 has a main body portion 21, a second upstream opening 22, and a second downstream opening 23.

[0025] The main body 21 has a hollow structure, and a second flow path 24 is formed inside the main body 21, through which exhaust gas that has bypassed a part of the first flow path 14 flows.

[0026] The second upstream opening 22 is located upstream of the second flow path 24, and takes in the exhaust gas that has bypassed a part of the first flow path 14 into the inside of the main body 21. The second downstream opening 23 allows the exhaust gas that has flowed inside the main body 21 to flow into the first flow path 14.

[0027] The second upstream opening 22 is connected to the first upstream opening 15 formed in the first flow path member 10 by a first communication portion 25. The second downstream opening 23 is connected to the first downstream opening 16 formed in the first flow path member 10 by a second communication portion 26.

[0028] The inside of the first communication portion 25 , the interior of the second flow path member 20 , and the inside of the second communication portion 26 form a second flow path 24 .

[0029] The above-described first flow path member 10 and second flow path member 20 allow exhaust gas to be diverted from the first flow path 14 to the second flow path member 20 through the first communicating portion 25. In addition, the exhaust gas that has flowed through the second flow path member 20 can be made to flow into the first flow path 14 through the second communicating portion 26.

[0030] The second flow path member 20 has a heat exchanger 30. The heat exchanger 30 has a refrigerant inlet 31, a heat exchanger main body 32, and a refrigerant outlet 33, and coolant flows through the heat exchanger 30 as a refrigerant. The heat exchanger 30 exchanges heat between the exhaust gas flowing through the second flow path 24 and the refrigerant.

[0031] The refrigerant inlet 31 is a hollow pipe-shaped section that connects a flow path (not shown) through which coolant flows before cooling the engine and the inside of the heat exchanger main body 32. The refrigerant inlet 31 allows the coolant supplied from the flow path to flow into the heat exchanger main body 32.

[0032] The refrigerant outlet 33 is a hollow tube-shaped section that connects the inside of the heat exchanger main body 32 to a flow path (not shown) that supplies cooling water to the engine. The refrigerant inlet 31 allows the cooling water that has flowed inside the heat exchanger main body 32 to flow out into the flow path.

[0033] When exhaust gas flows through the portion of the main body 21 of the second flow path member 20 surrounded by the heat exchanger main body 32 (the portion of the second flow path 24 surrounded by the heat exchanger main body 32), the heat exchanger 30 performs heat exchange between the exhaust gas and the cooling water flowing inside the heat exchanger main body 32, and transfers and recovers heat from the exhaust gas to the cooling water. Note that a state in which the valve mechanism 40 described below closes the first flow path 14 and the exhaust gas flows through the second flow path 24 to perform the heat exchange is called a heat recovery state. On the other hand, a state in which the valve mechanism 40 opens the first flow path 14 and the exhaust gas does not flow through the second flow path 24 is called a heat non-recovery state.

[0034] As shown in FIG. 2 , the exhaust heat recovery device 1 includes a valve mechanism 40 inside the first flow path member 10 .

[0035] FIG. 4 is a perspective view illustrating the valve mechanism 40 of the exhaust heat recovery system 1 shown in FIG.

[0036] The valve mechanism 40 has a butterfly valve 41 that opens and closes the first flow path 14, a shutter portion 42 that blocks or obstructs exhaust gas flowing from the second flow path 24 into the first flow path 14, and a valve body 43 that opens and closes the first flow path 14.

[0037] The valve mechanism 40 is provided at a part of the downstream side of the inner member 50 in the flow direction of the exhaust gas. In other words, the valve mechanism 40 is provided downstream of the double wall portion 19.

[0038] A rotary shaft 44 is connected to the valve body 43 and is rotatably supported within the first flow path 14. The rotary shaft 44 is connected to a drive shaft of an actuator (not shown) as a drive unit.

[0039] The valve element 43 of the butterfly valve 41 is a plate-shaped member formed to a length and width sufficient to close the first flow path 14. The valve element 43 can switch between opening and closing the first flow path 14 by rotating the rotary shaft portion 44.

[0040] The shutter 42 is provided on the valve body 43. The shutter 42 has a shutter main body 42a and a pair of connecting portions 42b. The shutter main body 42a opens and closes the first downstream opening 16.

[0041] The connecting portion 42b supports the shutter main body portion 42a by maintaining a distance from the valve body 43 that prevents the shutter main body portion 42a from contacting the inner wall portion (first downstream opening 16) of the first flow path member 10 and is capable of blocking the first downstream opening 16.

[0042] The shutter portion 42 has a protrusion 45 that protrudes outward in the direction of the rotation radius of the rotating valve mechanism 40. When the valve mechanism 40 is in the heat non-recovery state (FIGS. 5 and 6), the protrusion 45 abuts against the inner surface of the first flow path member 10 downstream of the first downstream opening 16 in the flow direction of the exhaust gas.

[0043] When the valve body 43 is in a non-heat recovery state, the end 43a of the valve body 43 upstream in the flow direction of the exhaust gas is configured to abut or come into close proximity with the first upright portion 51 when the valve mechanism 40 is in a heat recovery state, i.e., when the valve body 43 blocks the first flow path 14.

[0044] Furthermore, when the valve body 43 is in a non-heat recovery state, the end portion 43b of the valve body 43 downstream in the flow direction of the exhaust gas is configured to abut or come into close proximity with the second upright portion 52 when the valve mechanism 40 is in a heat recovery state, i.e., when the valve body 43 blocks the first flow path 14.

[0045] In this embodiment, the first upright portion 51 is formed larger than the gap D1 formed in the separation direction between the first downstream opening 16 and the shutter portion 42 when the valve mechanism 40 is in the heat non-recovery state (FIG. 5). Moreover, the second upright portion 52 is formed larger than the gap D2 in the separation direction between the inner surface of the first flow path member 10 and the valve when the valve mechanism 40 is in the heat recovery state (FIG. 2).

[0046] <Operation of Valve Mechanism and Flow of Exhaust Gas> Next, the operation of the valve mechanism 40 and the flow of exhaust gas in the exhaust heat recovery system 1 according to this embodiment will be described.

[0047] Fig. 5 is a partially cutaway front view of the exhaust heat recovery device 1. Fig. 6 is a side view of the exhaust heat recovery device 1 shown in Fig. 5 in a non-heat recovery state, as viewed from the upstream side of the first flow path 14.

[0048] The valve mechanism 40 in the exhaust heat recovery device 1 can be switched between a heat recovery state (Figures 2 and 3) in which the first downstream opening 16 is opened by the shutter portion 42 and the first flow path 14 is closed by the butterfly valve 41, and a non-heat recovery state (Figures 5 and 6) in which the first downstream opening 16 is closed by the shutter portion 42 and the first flow path 14 is opened by the butterfly valve 41.

[0049] In this embodiment, as shown in Figures 5 and 6, when the heat non-recovery state is entered, the valve mechanism 40 rotates so that the main surface of the valve body 43 of the valve mechanism 40 becomes parallel to the flow direction of the exhaust gas, and the tip of the end 42e of the shutter portion 42 abuts against the surface of the first upright portion 51 on the downstream side in the flow direction of the exhaust gas, and the convex portion 45 formed on the shutter portion 42 abuts against the inner surface of the first flow path member 10 downstream of the first downstream opening 16 in the flow direction of the exhaust gas.

[0050] In this state, the exhaust gas flows into the first flow path member 10 from the first inlet portion 12 , flows through the first flow path 14 formed inside the first flow path member 10 , and flows out from the first outlet portion 13 .

[0051] On the other hand, when the heat recovery state is not in progress, the end 43a of the valve body 43, which was located upstream in the flow direction, approaches the first raised portion 51, and the end 43b of the valve body 43, which was located downstream in the flow direction, rotates in a direction approaching the second raised portion 52, causing the valve mechanism 40 to rotate so that the main surface of the valve body 43 of the valve mechanism 40 is perpendicular to the flow direction of the exhaust gas, and the valve mechanism 40 transitions to the heat recovery state.

[0052] 2 and 3 , when the valve mechanism 40 is in the heat recovery state, the upstream surface of the first upright portion 51 in the flow direction comes into contact with the downstream surface of the end 43 a of the valve body 43. Also, the downstream surface of the second upright portion 52 in the flow direction comes into contact with the upstream surface of the end 43 b of the valve body 43 in the flow direction.

[0053] In this state, when exhaust gas flows into the first flow path member 10 from the first inlet portion 12, it remains in the space S2 formed by the valve body 43 and the first flow path member 10, and flows into the second flow path 24 from the first upstream opening 15.

[0054] The exhaust gas flows through the second flow path 24 inside the second flow path member 20, and exchanges heat with the refrigerant flowing through the heat exchange section 30. After flowing through the second flow path 24, the exhaust gas returns to the first flow path 14 from the first downstream opening 16, flows through the first flow path, and flows out from the first outlet section 13.

[0055] <Effects> The exhaust heat recovery device 1 according to this embodiment includes a first flow path member 10 having a first flow path 14 formed therein through which exhaust gas flows, a second flow path member 20 provided adjacent to the first flow path member 10 and having a second flow path 24 formed therein that bypasses part of the first flow path 14 and having a heat exchange section 30 that exchanges heat between the exhaust gas flowing through the second flow path 24 and the refrigerant, and a valve mechanism 40 that is disposed within the first flow path member 10 and has a butterfly valve 41 that opens and closes the first flow path 14 and a shutter section 42 that blocks or obstructs the flow of exhaust gas from the second flow path 24.

[0056] The first flow path member 10 is formed with a first upstream opening 15 as an outlet for exhaust gas from the first flow path 14 to the second flow path 24, and a first downstream opening 16 as an inlet for exhaust gas from the second flow path 24 to the first flow path 14.

[0057] The valve mechanism 40 is configured to be switched between a heat recovery state and a heat non-recovery state by rotation of a rotary shaft 44 that is perpendicular to the flow direction of exhaust gas in the first flow path 14. As described above, in the heat non-recovery state, the shutter 42 closes the first downstream opening 16, and the butterfly valve 41 opens the first flow path 14. In the heat recovery state, the shutter 42 opens the first downstream opening 16, and the butterfly valve 41 closes the first flow path 14.

[0058] In this embodiment, the first flow path member 10 is provided with a double wall portion 19 having an inner wall portion 17 facing the first flow path 14 and an outer wall portion 18 located on the opposite side of the inner wall portion 17 from the first flow path 14, located upstream in the flow direction of the exhaust gas from the butterfly valve 41 that opens and closes the first flow path 14.

[0059] The double wall portion 19 has a gap portion S1 formed between the inner wall portion 17 and the outer wall portion 18 and isolated from the first flow path 14 .

[0060] When heat exchange is performed in the exhaust gas heat exchange section 30, the exhaust gas remains in the space S2 of the first flow path member 10 created by the closed butterfly valve 41, and flows into the second flow path 24 from the first upstream opening 15 (see the arrow in Figure 2).

[0061] In such a case, in the double wall portion 19, the heat of the exhaust gas flowing through the first flow path 14 is conducted from the inner wall portion 17 to the outside via the outer wall portion 18, so that in the double wall portion 19, heat loss due to heat dissipation from the outer wall portion 18 to the outside of the first flow path member 10 can be suppressed.

[0062] Therefore, the exhaust heat recovery device 1 can prevent a decrease in the temperature of the exhaust gas flowing through the heat exchange section 30, and can prevent a decrease in the heat recovery efficiency.

[0063] In this embodiment, the double wall portion 19 has the gap portion S1, and therefore the gap portion S1 can prevent the heat conduction of the exhaust gas flowing through the first flow passage 14 formed inside the inner wall portion 17.

[0064] Therefore, the effect of suppressing heat loss due to heat radiation from the first flow path member 10 constituting the outer wall portion 18 to the outside of the first flow path member 10 can be enhanced.

[0065] In this embodiment, the inner member 50 is provided inside the first flow path member 10 and covers the inner surface of the first flow path member 10, with the inner member 50 constituting the inner wall portion 17 and the first flow path member 10 constituting the outer wall portion 18.

[0066] In this way, by forming the inner wall portion 17 using the inner member 50, it is possible to easily manufacture the double wall portion 19.

[0067] In this embodiment, the first flow path member 10 and the inner member 50 are connected by spot welding at a joint 53 located downstream in the flow direction of exhaust gas.

[0068] In this way, in this embodiment, the inner member 50 is joined to the first flow path member 10 on either the upstream or downstream side in the flow direction of the exhaust gas, and the other side, either the upstream or downstream side, that is not joined can be made a free end with respect to thermal expansion and contraction of the inner wall portion 17.

[0069] In particular, the outer wall portion 18 of the first flow path member 10 is connected to the second flow path member 20 at two locations. More specifically, the first communicating portion 25 of the second flow path member 20 is connected to the first upstream opening 15 of the first flow path member 10, and the second communicating portion 26 of the second flow path member 20 is connected to the first downstream opening 16 of the first flow path member 10. In the non-heat recovery state, high-temperature exhaust gas flows through the first flow path 14, and the first flow path member 10 tends to expand due to the heat of the exhaust gas. However, in the portion of the first flow path member 10 between the two connecting points with the second flow path member 20 as described above, the position is restricted by the second flow path member 20, and thermal stress occurs. In response to this, in the exhaust heat recovery device 1, the double wall portion 19 is disposed between the first upstream opening 15 and the first downstream opening 16 (i.e., the double wall portion 19 is disposed between two connecting points), and the inner wall portion 17 (inner member 50) that receives the heat of the exhaust gas is locally welded, with at least one end being a free end, thereby allowing thermal expansion of the inner wall portion 17. This makes it possible to improve the heat resistance of the exhaust heat recovery device 1.

[0070] [Other Embodiments] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0071] In the first embodiment, the fluid that cools the exhaust gas may be other than cooling water, and a medium such as a liquid or gas that is suitable for heat exchange can be applied.

[0072] In this embodiment, the valve mechanism 40 has a structure in which a pair of connecting portions 42b support both ends of the shutter main body 42a. However, for example, there may be one connecting portion 42b in the center of the shutter main body 42a. Alternatively, there may be a plurality of connecting portions 42b arranged in parallel, forming a so-called louver.

[0073] The inner member 50 provided inside the first flow path member 10 may be structured to be divided along a horizontal plane including the axis of the rotary shaft portion 44 of the valve mechanism 40. Alternatively, the inner member 50 may be structured to be divided along a plane perpendicular to the axis of the rotary shaft portion 44 of the valve mechanism 40.

[0074] This application claims priority based on Japanese Patent Application No. 2023-117582, filed with the Japan Patent Office on July 19, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. An exhaust heat recovery device that recovers heat from exhaust gas discharged from an engine by heat exchange with a fluid, comprising: a first flow path member having a first flow path formed therein through which exhaust gas flows; a second flow path member provided adjacent to the first flow path member, having a second flow path formed therein that bypasses part of the first flow path, and having a heat exchange section that exchanges heat between the exhaust gas flowing in the second flow path and the fluid; and a valve mechanism provided in the first flow path, wherein the valve mechanism opens the first flow path or closes the first flow path to guide the exhaust gas to the second flow path, and the first flow path member has a double wall portion, at least in a part upstream of the valve mechanism in the exhaust gas flow direction, having an inner wall portion facing the first flow path and an outer wall portion located on the opposite side of the first flow path of the inner wall portion.

2. An exhaust heat recovery device according to claim 1, wherein the double wall portion has a gap portion formed between the inner wall portion and the outer wall portion and isolated from the first flow path.

3. An exhaust heat recovery device as claimed in claim 1, further comprising an inner member disposed inside the first flow path member and covering at least a portion of the inner surface of the first flow path member, the inner member constituting the inner wall portion and the first flow path member constituting the outer wall portion.

4. An exhaust heat recovery device as described in claim 3, wherein the first flow path member is connected to the second flow path member at two locations, the double wall portion is provided in the first flow path member between the two connection points with the second flow path member, and the inner member has a joint with the first flow path member on either the upstream or downstream side in the flow direction of the exhaust gas, and the other upstream or downstream side not having the joint is a free end.

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