JP6295792B2 - Engine exhaust system - Google Patents

Description

  The present invention relates to an engine exhaust device.

  Patent Document 1 discloses an exhaust device that includes an exhaust passage through which exhaust discharged from an engine flows, and an exhaust heat recovery unit that is provided in the exhaust passage and recovers the heat of the exhaust using cooling water. . The heat recovered by the exhaust heat recovery device is used for warming up or heating the engine.

JP 2011-169514 A

  The exhaust heat recovery device provided in the exhaust device described above is a device that uses cooling water to remove heat from the exhaust gas passing through the exhaust heat recovery unit. Therefore, the amount of exhaust heat recovered by the exhaust heat recovery device changes according to the flow rate of the exhaust gas passing through the exhaust heat recovery unit. In such an exhaust heat recovery device, it is desirable that the exhaust heat recovery efficiency be set as high as possible. However, in the exhaust heat recovery device, the exhaust heat recovery efficiency is set so that the cooling water temperature does not become too high even when the operation state with a large exhaust flow rate continues, and thus the operation state with a large exhaust flow rate is set. When the exhaust heat recovery efficiency is set as a reference, there is a problem that the exhaust heat recovery efficiency is lowered even in an operation state where the exhaust flow rate is small.

  Therefore, the present invention has been made in view of the above-mentioned problems, and while maintaining the exhaust heat recovery efficiency low in an operation state with a large exhaust flow rate, the exhaust heat recovery efficiency is higher than in the conventional case in an operation state with a low exhaust flow rate. Another object of the present invention is to provide an engine exhaust device that can be improved.

  The present invention is an engine exhaust apparatus that guides exhaust exhausted from an engine to the outside. The exhaust device includes a plurality of distribution passages that distribute and flow exhaust discharged from the engine, and an exhaust heat recovery unit that is provided in each of the plurality of distribution passages and collects the heat of the exhaust. The exhaust heat recovery unit is provided in the distribution passage, and includes a cylindrical exhaust heat recovery unit that recovers heat of exhaust gas that passes through, and a cooling unit that cools the exhaust heat recovery unit from the outer peripheral side via a cooling fluid. In addition, the diameter of the exhaust heat recovery unit is configured to be larger than the axial length of the exhaust heat recovery unit.

  According to the present invention, the exhaust device includes the exhaust heat recovery device in the distribution passage for distributing and flowing the exhaust discharged from the engine. The exhaust heat recovery part of the exhaust heat recovery device is configured such that its diameter is larger than the axial length. By forming the exhaust heat recovery unit in this manner, the exhaust heat recovery efficiency in the exhaust heat recovery unit becomes a characteristic that decreases exponentially as the exhaust gas flow rate passing through the exhaust heat recovery unit increases. By disposing an exhaust heat recovery unit with such characteristics in the distribution passage, the flow rate of exhaust gas passing through the exhaust heat recovery unit can be reduced. While maintaining the recovery efficiency low, the exhaust heat recovery efficiency in the exhaust heat recovery device can be increased as compared with the prior art in an operation state where the exhaust flow rate is small.

FIG. 1 is a schematic configuration diagram of an engine including an exhaust device according to the first embodiment. FIG. 2 is a cross-sectional view of an exhaust heat recovery device provided in the exhaust device. FIG. 3 is a side view of the exhaust heat recovery unit of the exhaust heat recovery device. FIG. 4A is a diagram illustrating an exhaust flow in an engine operating state in which the exhaust flow rate is large. FIG. 4B is a diagram illustrating an exhaust flow in an engine operating state in which the exhaust flow rate is small. FIG. 5 is a diagram showing the relationship between the exhaust flow rate and the exhaust heat recovery efficiency in the exhaust heat recovery device. FIG. 6 is a schematic configuration diagram of an engine including an exhaust device according to the second embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an engine 1 including an exhaust device 60 according to the first embodiment.

  An engine 1 shown in FIG. 1 is a V-type 6-cylinder internal combustion engine mounted on a vehicle, for example. The engine 1 includes a right bank 11 having first, third, and fifth cylinders, and a left bank 12 having second, fourth, and sixth cylinders. Further, the engine 1 is provided with an exhaust device 60 that guides the exhaust discharged from the engine 1 to the outside.

  The exhaust device 60 includes a first exhaust manifold 20R through which exhaust gas discharged from each cylinder of the right bank 11 flows, a first exhaust pipe 30R connected to the downstream end of the first exhaust manifold 20R, and each cylinder of the left bank 12. A second exhaust manifold 20L for flowing the discharged exhaust, a second exhaust pipe 30L connected to the downstream end of the second exhaust manifold 20L, and a junction pipe connected to the downstream ends of the first exhaust pipe 30R and the second exhaust pipe 30L 40.

  The first exhaust manifold 20R collects exhaust discharged from each cylinder of the right bank 11 and guides it to the first exhaust pipe 30R. The first exhaust manifold 20R is provided with a manifold catalytic converter 21 for purifying exhaust flowing in the manifold. In the first exhaust pipe 30R, an underfloor catalytic converter 31 that purifies the exhaust and an exhaust heat recovery unit 70 that recovers the heat of the exhaust are disposed in order from the upstream side.

  On the other hand, the second exhaust manifold 20L collects exhaust exhausted from the cylinders of the left bank 12 and guides it to the second exhaust pipe 30L. The second exhaust manifold 20L is provided with a manifold catalytic converter 21 for purifying exhaust flowing in the manifold. In the second exhaust pipe 30L, an underfloor catalytic converter 31 that purifies the exhaust and an exhaust heat recovery unit 70 that recovers the heat of the exhaust are disposed in order from the upstream side.

  The manifold catalytic converter 21 installed in the second exhaust manifold 20L is a catalytic converter having the same configuration as the manifold catalytic converter 21 installed in the first exhaust manifold 20R. The underfloor catalytic converter 31 and the exhaust heat recovery unit 70 installed in the second exhaust pipe 30L have the same configuration as the underfloor catalytic converter 31 and the exhaust heat recovery unit 70 installed in the first exhaust pipe 30R.

  The first exhaust pipe 30R and the second exhaust pipe 30L are configured such that their downstream ends meet. The merge pipe 40 is connected to the merge portion of the first exhaust pipe 30R and the second exhaust pipe 30L. The junction pipe 40 is provided with a muffler 41 for suppressing exhaust noise.

  The exhaust discharged from the right bank 11 of the engine 1 is purified by the manifold catalytic converter 21 provided in the first exhaust manifold 20R and the underfloor catalytic converter 31 provided in the first exhaust pipe 30R, and passes through the underfloor catalytic converter 31. After that, the exhaust heat is recovered by the exhaust heat recovery unit 70. Further, the exhaust discharged from the left bank 12 of the engine 1 is purified by the manifold catalytic converter 21 provided in the second exhaust manifold 20L and the underfloor catalytic converter 31 provided in the second exhaust pipe 30L, and the underfloor catalytic converter 31 is obtained. After passing through, the exhaust heat recovery unit 70 recovers the heat of the exhaust. The exhaust gas that has passed through the first exhaust pipe 30R and the second exhaust pipe 30L flows into the merge pipe 40, passes through the muffler 41, and is then discharged to the outside.

  The exhaust heat recovered by the two exhaust heat recovery devices 70 is used for warming up or heating the engine 1.

  In the exhaust device 60 of the engine 1 described above, the first exhaust manifold 20R and the first exhaust pipe 30R that flow the exhaust discharged from the right bank 11, the second exhaust manifold 20L that flows the exhaust discharged from the left bank 12, and the second exhaust manifold 20L. The two exhaust pipes 30L function as distribution exhaust passages that distribute and distribute exhaust discharged from the engine 1.

  Next, the configuration of the exhaust heat recovery device 70 will be described with reference to FIGS. 2 and 3. FIG. 2 is a sectional view of the exhaust heat recovery unit 70 along a direction orthogonal to the extending direction of the exhaust passage, and FIG. 3 is a side view of the exhaust heat recovery unit 71 constituting the exhaust heat recovery unit 70.

  As shown in FIG. 2, the exhaust heat recovery unit 70 includes an exhaust heat recovery unit 71 that recovers the heat of the exhaust, and a cooling unit 72 that takes the heat of the exhaust heat recovery unit 71 through the cooling water.

  The cooling unit 72 is a cylindrical member, and a cylindrical exhaust heat recovery unit 71 is disposed in the interior 72 </ b> D of the cooling unit 72. The inner diameter of the cooling unit 72 is formed to be slightly larger than the outer diameter of the exhaust heat recovery unit 71, and the exhaust heat recovery unit 71 is fitted in the cooling unit 72. The interior 72D of the cooling unit 72 is configured as a part of an exhaust passage through which exhaust flows.

  As shown in FIGS. 2 and 3, the exhaust heat recovery unit 71 includes a material having a higher thermal conductivity than the material forming the first and second exhaust manifolds 20R, 20L and the first and second exhaust pipes 30R, 30L, For example, it is made of silicon carbide (SiC). The exhaust heat recovery unit 71 is a lattice-shaped cylindrical member having a plurality of through holes 71A through which exhaust gas can pass, and the diameter (outer diameter) D of the exhaust heat recovery unit 71 is the axial length of the exhaust heat recovery unit 71 ( It is set larger than the length (L) of the passage extending direction. The through hole 71 </ b> A of the exhaust heat recovery unit 71 penetrates in the axial direction from the upstream end surface to the downstream end surface of the exhaust heat recovery unit 71.

  Note that the exhaust heat recovery unit 71 may be configured as a honeycomb structure in which the cross-sectional shape of the through hole 71A is a hexagon. The cross-sectional shape of the through hole 71A is not limited to a quadrangle or a hexagon, but may be other shapes such as a circle or a triangle.

  The exhaust heat recovery unit 71 configured as described above is heated by the exhaust gas passing through the through hole 71A. Therefore, the temperature of the exhaust after passing through the exhaust heat recovery unit 71 is lower than the temperature of the exhaust before passing.

  The cooling unit 72 is formed around the exhaust heat recovery unit 71. The cooling unit 72 includes an annular channel 72A formed along the outer periphery of the exhaust heat recovery unit 71, an inlet 72B for introducing cooling water into the annular channel 72A, and an exhaust for discharging cooling water from the annular channel 72A. And an outlet 72C. The introduction port 72 </ b> B and the discharge port 72 </ b> C are arranged 180 degrees apart in the circumferential direction of the exhaust heat recovery unit 71.

  Cooling water pumped by a water pump (not shown) of the engine 1 flows into the annular flow path 72A of the exhaust heat recovery device 70 through the introduction port 72B. The cooling water flows through the annular flow path 72A and cools the exhaust heat recovery unit 71 from the outer peripheral side. The cooling water that has passed through the annular flow path 72A is warmed by taking the heat of the exhaust heat recovery section 71, and is discharged from the exhaust heat recovery device 70 through the discharge port 72C. The cooling water discharged in this way is supplied to a water jacket formed in a cylinder block or the like of the engine 1 or a heating device (not shown), and is used for warming up the engine 1 or heating the passenger compartment.

  As described above, the exhaust heat recovery unit 71 that takes away the heat of the exhaust gas is configured such that the diameter D is larger than the axial length L. By configuring the exhaust heat recovery unit 71 in this way, the exhaust heat recovery efficiency in the exhaust heat recovery unit 70 has characteristics as shown in FIG. That is, as shown in FIG. 5, the exhaust heat recovery efficiency of the exhaust heat recovery unit 70 decreases exponentially as the flow rate of the exhaust gas passing through the exhaust heat recovery unit 71 increases.

  In the present embodiment, the exhaust device 60 is constructed using the exhaust heat recovery device 70 having the efficiency characteristics as shown in FIG. That is, in the conventional exhaust device, one exhaust heat recovery device is installed in the junction pipe where the exhaust gas is collected, but in this embodiment, the exhaust heat recovery device 70 is connected to the junction pipe 40 (exhaust gas) as shown in FIG. Are installed in each of the first exhaust pipe 30R and the second exhaust pipe 30L on the upstream side of the portion where the two are joined.

  With reference to FIG. 4A, FIG. 4B, and FIG. 5, the exhaust heat recovery efficiency in the exhaust heat recovery device 70 is demonstrated. FIG. 4A is a diagram for explaining the flow of exhaust in an engine operating state with a large exhaust flow rate, and FIG. 4B is a diagram for explaining the flow of exhaust in an engine operating state with a small exhaust flow rate.

  As shown in FIG. 4A, the exhaust discharged from the right bank 11 of the engine 1 flows into the merge pipe 40 through the first exhaust manifold 20R and the first exhaust pipe 30R, and the exhaust discharged from the left bank 12 of the engine 1 is the first exhaust. 2 Flow into the merging pipe 40 through the exhaust manifold 20L and the second exhaust pipe 30L. The exhaust discharged from the engine 1 in this manner is purified by the manifold catalytic converter 21 and the underfloor catalytic converter 31, and then the exhaust heat is recovered by the exhaust heat recovery unit 70.

  When the engine operating state is a high load and a high engine rotation speed as shown in FIG. 4A, that is, in an operating state where the flow rate of exhaust exhausted from the engine 1 is large, the exhaust heat recovery efficiency of the exhaust heat recovery unit 70 is as shown in FIG. As shown, it is lower than at low exhaust flow rates.

  If the engine operating state is a high load and a high engine speed, and the flow rate of the exhaust gas discharged from the engine 1 and passing through the first and second exhaust pipes 30R, 30L is R3, it flows through the junction pipe 40. The flow rate of the exhaust gas is R4, which is about twice that of R3. Since the exhaust heat recovery efficiency of the exhaust heat recovery unit 70 has the characteristics as shown in FIG. 5, the exhaust heat recovery efficiency in the exhaust heat recovery unit 70 is the first exhaust pipe 30R and the second exhaust flow rate R3. Even when the exhaust heat recovery unit 70 is arranged in the exhaust pipe 30L, the value is as low as when the exhaust heat recovery unit 70 is arranged in the merge pipe 40 where the exhaust flow rate is R4 as in the conventional method. .

  Therefore, even if the exhaust heat recovery device 70 is provided in each of the first exhaust pipe 30R and the second exhaust pipe 30L upstream of the merging pipe 40, the exhaust heat recovery efficiency in an operating state with a large exhaust flow rate. Can be kept low. Therefore, the temperature of the cooling water does not become too high even when the operating state of high load and high engine speed continues.

  On the other hand, when the engine operating state is a low load and a low engine speed, the flow rate of the exhaust gas discharged from the engine 1 is lower than that at a high load and a high engine speed. As described above, in the operation state where the flow rate of the exhaust gas discharged from the engine 1 is small, the exhaust heat recovery efficiency of the exhaust heat recovery unit 70 is higher than that at the time of a high exhaust gas flow rate as shown in FIG.

  When the engine operating state is a low load and a low engine speed, if the flow rate of the exhaust discharged from the engine 1 and passing through the first and second exhaust pipes 30R, 30L is R1, it flows through the merging pipe 40. The flow rate of the exhaust gas is R2, which is about twice that of R1. Since the exhaust heat recovery efficiency of the exhaust heat recovery unit 70 has characteristics as shown in FIG. 5, the exhaust heat recovery efficiency in the exhaust heat recovery unit 70 is the same as that of the conventional method. Compared to the case where the exhaust heat recovery device 70 is disposed in the first exhaust pipe 30R and the second exhaust pipe 30L having the low exhaust flow rate R1, the case where the exhaust heat recovery device 70 is disposed in the merge pipe 40 where R2 is R2 is higher.

  As described above, in this embodiment, the exhaust heat recovery device 70 is provided not in the merging pipe 40 but in the first exhaust pipe 30R and the second exhaust pipe 30L, so that the flow rate of the exhaust gas passing through the exhaust heat recovery device 70 at a low exhaust gas flow rate. Can be reduced. As a result, the exhaust heat recovery efficiency in the exhaust heat recovery unit 70 can be improved as compared with the conventional one in an operation state where the flow rate of the exhaust discharged from the engine 1 is small.

  According to the exhaust device 60 of the engine 1 described above, the following effects can be obtained.

  The exhaust device 60 of the engine 1 includes an exhaust heat recovery device 70 in the first and second exhaust pipes 30R and 30L that distribute and flow the exhaust discharged from the engine 1. The exhaust heat recovery unit 71 of the exhaust heat recovery unit 70 is configured such that its diameter D is greater than the axial length L. By forming the exhaust heat recovery unit 71 in this way, the exhaust heat recovery efficiency in the exhaust heat recovery unit 70 has a characteristic that decreases exponentially as the exhaust gas flow rate passing through the exhaust heat recovery unit 71 increases. By disposing the exhaust heat recovery device 70 having such characteristics in the first and second exhaust pipes 30R and 30L before the distributed exhaust gas joins, the flow rate of the exhaust gas passing through the exhaust heat recovery unit 71 is reduced. The exhaust heat recovery efficiency in the exhaust heat recovery unit 70 can be kept low in an operation state with a large exhaust flow rate, while the exhaust heat recovery efficiency in the exhaust heat recovery unit 70 can be improved in the operation state with a low exhaust flow rate. It becomes possible to raise. Moreover, since the exhaust heat recovery device 70 is disposed in each of the first and second exhaust pipes 30R and 30L, a small exhaust heat recovery device 70 can be employed.

  The exhaust heat recovery devices 70 arranged in the first and second exhaust pipes 30R, 30L have the same configuration, and the exhaust heat recovery unit 71 and the cooling unit 72 in the two exhaust heat recovery devices 70 have the same structure. is there. Accordingly, the exhaust heat recovery efficiency of the two exhaust heat recovery units 70 can be made uniform, and variations in the amount of exhaust heat recovery between the two exhaust heat recovery units 70 can be suppressed. Therefore, the temperature management etc. of the cooling water heated with the exhaust heat recovery device 70 become easy.

  The exhaust heat recovery unit 71 of the exhaust heat recovery unit 70 is preferably configured as a honeycomb structure in which the cross-sectional shape of the through hole 71A is a hexagon. With this configuration, the through holes 71A can be densely arranged in the exhaust heat recovery unit 71, and the exhaust heat recovery unit 71 can be downsized while maintaining the exhaust heat recovery efficiency characteristics. Therefore, the exhaust heat recovery device 70 can be reduced in size and weight, and the exhaust device 60 of the engine 1 can be configured compactly.

(Second Embodiment)
With reference to FIG. 6, the exhaust apparatus 60 of the engine 1 by 2nd Embodiment of this invention is demonstrated.

  The exhaust device 60 according to the second embodiment is different from the exhaust device according to the first embodiment in the arrangement of the exhaust heat recovery device 70. Note that in the following embodiments, the same reference numerals are used for configurations and the like that perform the same functions as those in the first embodiment, and repeated descriptions are omitted as appropriate.

  As shown in FIG. 6, in the exhaust device 60 according to the second embodiment, the junction pipe 40 includes distribution pipes 40 </ b> A and 40 </ b> B that distribute the exhaust gas flowing through the junction pipe 40. The distribution pipes 40 </ b> A and 40 </ b> B are configured to branch from the middle of the joining pipe 40 and join again on the downstream side. The passage after the merging of the distribution pipes 40A and 40B is configured as a merging pipe 40, and a muffler 41 is provided in the merging pipe 40.

  In the second embodiment, one exhaust heat recovery device 70 is provided for each of the distribution pipes 40A and 40B. The exhaust heat recovery unit 70 is configured to recover the heat of the exhaust heat recovery unit 71 heated by the exhaust gas flowing through the distribution pipes 40 </ b> A and 40 </ b> B by the cooling water flowing through the cooling unit 72. The exhaust heat recovery section 71 that takes away the heat of the exhaust gas is configured such that its diameter D is larger than the axial length L, and the exhaust heat recovery efficiency in the exhaust heat recovery device 70 is as shown in FIG. It has become.

  As described above, since the exhaust heat recovery unit 70 is provided in each of the distribution pipes 40A and 40B branched from the junction pipe 40, the flow rate of the exhaust gas passing through the exhaust heat recovery unit 71 of each exhaust heat recovery unit 70 is set to the junction pipe 40. The flow rate of the exhaust flowing through As a result, in the exhaust device 60 according to the second embodiment, similarly to the exhaust device according to the first embodiment, the exhaust heat recovery efficiency in the exhaust heat recovery device 70 is improved in an operation state where the flow rate of exhaust exhausted from the engine 1 is large. It is possible to increase the exhaust heat recovery efficiency in the exhaust heat recovery unit 70 as compared with the conventional one in an operation state where the exhaust flow rate is small while maintaining low.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The technical ideas in the first and second embodiments can be arbitrarily combined as necessary.

  In the exhaust device 60 according to the second embodiment, two distribution pipes 40 </ b> A and 40 </ b> B are branched from the merge pipe 40. However, the number of distribution pipes branched from the merge pipe 40 is not two but may be three or more. In this case, the exhaust heat recovery device 70 may be provided in each distribution pipe, or the exhaust heat recovery device 70 may be provided only in an arbitrary distribution pipe.

DESCRIPTION OF SYMBOLS 1 Engine 11 Right bank 12 Left bank 20R 1st exhaust manifold 20L 2nd exhaust manifold 30R 1st exhaust pipe 30L 2nd exhaust pipe 40 Merge pipe 40A Distribution pipe 60 Exhaust device 70 Waste heat recovery device 71 Waste heat recovery part 71A Through-hole 72 Cooling unit

Claims (4)

An exhaust system for an engine that guides exhaust discharged from the engine to the outside.
A plurality of distribution passages for distributing and flowing exhaust discharged from the engine;
An exhaust heat recovery device that is provided one by one in the plurality of distribution passages and recovers the heat of the exhaust; and
The exhaust heat recovery device is
A cylindrical exhaust heat recovery part that is provided in the distribution passage and recovers heat of exhaust passing therethrough;
A cooling unit that cools the exhaust heat recovery unit from the outer peripheral side via a cooling fluid, and
The diameter of the exhaust heat recovery unit is configured to be larger than the axial length of the exhaust heat recovery unit,
An exhaust system for an engine. The exhaust heat recovery unit is configured as a honeycomb structure having a plurality of through holes through which exhaust gas can pass.
The engine exhaust system according to claim 1. The exhaust heat recovery units provided for each of the distribution passages have the same configuration.
The engine exhaust system according to claim 1 or 2, wherein the engine exhaust system is provided. The engine is a V-type engine having two banks,
The distribution passage is a first exhaust passage for flowing exhaust discharged from one bank, and a second exhaust passage for flowing exhaust discharged from the other bank,
The exhaust heat recovery device is provided in each of the first exhaust passage and the second exhaust passage on the upstream side of a joining portion where the first exhaust passage and the second exhaust passage join.
The exhaust system for an engine according to any one of claims 1 to 3, wherein

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