JP3532852B2 - EGR device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an EGR device.

[0002]

2. Description of the Related Art Conventionally, in an automobile engine or the like, a part of exhaust gas is extracted from the exhaust side and returned to the intake side.
The exhaust gas returned to the intake side suppresses the combustion of fuel in the engine to lower the combustion temperature and NOx.
So-called exhaust gas recirculation (EGR) that reduces the generation of (nitrogen oxides)
n) has been done.

Generally, when this kind of exhaust gas recirculation is carried out, between an appropriate position of the exhaust passage extending from the exhaust manifold to the exhaust pipe and an appropriate position of the intake passage extending from the intake pipe to the intake manifold. It is connected by an EGR pipe, and exhaust gas is recirculated through the EGR pipe.

The exhaust gas recirculated to the engine is EG
Cooling in the middle of the R pipe lowers the temperature of the exhaust gas and reduces its volume, so that the combustion temperature is lowered and the NOx is effectively reduced without reducing the output of the engine so much.
Since it is possible to reduce the occurrence of the above, some engines are equipped with a water-cooled EGR cooler in the middle of the EGR pipe that recirculates exhaust gas.

FIG. 3 shows an example of the EGR device for performing the above-mentioned exhaust gas recirculation. In the figure, 1 shows an engine which is a diesel engine, and the engine 1 is equipped with a turbocharger 2. The intake air 4 guided from the air cleaner 3 is sent to the compressor 2a of the turbocharger 2 through the intake pipe 5, the intake air 4 pressurized by the compressor 2a is sent to the intercooler 6 to be cooled, and the intercooler 6 is further cooled. The intake air 4 is guided to the intake manifold 7 and distributed to each cylinder of the engine 1.

The exhaust gas 8 discharged from each cylinder of the engine 1 is sent to the turbine 2b of the turbocharger 2 through an exhaust manifold 9, and the exhaust gas 8 that drives the turbine 2b is exhausted through an exhaust pipe 10 to the outside of the vehicle. It is designed to be discharged to.

An EGR pipe 11 connects between one end of the exhaust manifold 9 in the direction of arrangement of the cylinders and one end of the intake pipe 5 connected to the intake manifold 7. A part of the exhaust gas 8 can be extracted and guided to the intake pipe 5.

In the EGR pipe 11, the E
An EGR valve 12 that appropriately opens and closes the GR pipe 11, and
EGR cooler 1 for cooling the recirculated exhaust gas 8
In the EGR cooler 13, the temperature of the exhaust gas 8 can be lowered by exchanging heat between the cooling water 14 and the exhaust gas 8.

[0009]

However, in such a conventional EGR device, a part of the cooling water 14 used for cooling the engine 1 is extracted from the outlet side of the radiator 15 and cooled by the EGR cooler 13. Used for the EG
The cooling water 14 that has been heated by exchanging heat with the exhaust gas 8 in the R cooler 13 and has been heated by cooling the engine 1
Since the heat is absorbed by the radiator 15, not only the amount of heat collected by the engine 1 but also the amount of heat collected by the EGR cooler 13 must be released to the atmosphere. There is a problem that the size of the radiator must be significantly increased to improve the cooling capacity, while the radiator 1
There was a trade-off problem that the increase in size of 5 deteriorates the mountability on the vehicle.

The present invention has been made in view of the above-mentioned circumstances, and makes it possible to cool the exhaust gas recirculated to the intake side without water cooling with cooling water, thereby increasing the size of the radiator and accompanying it. It aims to avoid the problem of deterioration of vehicle mountability at the same time.

[0011]

The present invention relates to an EGR device in which a part of exhaust gas is extracted from the exhaust passage side through an EGR pipe and is recirculated to the intake passage side. A heat radiating portion is provided at a position where the exhaust temperature is relatively low in the exhaust passage downstream of the exhaust gas extraction point, and the heat radiating portion and the heat absorbing portion are connected by a heat pipe. It is what

Thus, in this way, the heat held by the exhaust gas recirculated to the intake side through the EGR pipe is absorbed by the heat absorbing portion, and the absorbed heat is transferred to the heat radiating portion through the heat pipe. Since it is possible to transport the heat and release it to the exhaust gas passing through the heat radiating portion, the exhaust gas recirculated to the intake side can be cooled without water cooling with cooling water.

This makes it possible to eliminate the need for a water-cooled EGR cooler, or to reduce the amount of heat collected by the EGR cooler even when a water-cooled EGR cooler is used together. It is possible to reduce the load on the radiator and avoid a large increase in the size of the radiator.

Further, in the present invention, in constructing the heat absorbing portion and the heat radiating portion, at least one of them is provided with the end portion of the heat pipe exposed to the flow of exhaust gas and the outer peripheral surface of the end portion. It is also possible to increase the heat exchange area with the exhaust gas by the fins and to realize efficient heat absorption or heat dissipation.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show an example of an embodiment for carrying out the present invention, and the same reference numerals as those in FIG. 3 represent the same parts.

As shown in FIG. 1, in the EGR device of this embodiment, the EGR cooler 13 in the EGR pipe 11 is used.
Is provided on the upstream side of the turbocharger 2, and the heat radiating section 17 is provided on the exhaust pipe 10 downstream of the turbine 2b of the turbocharger 2 at a position where the exhaust temperature is relatively low. The space between them is connected by a heat pipe 18.

Here, as shown in FIG. 2, the heat pipe 18 is a wick 19 made of a porous material having a capillary action (for example, a braid of fine metal wires or a sintered metal).
Is a conventionally well-known one in which a volatile working fluid (heat transport medium) is enclosed in a pipe container 20 in which is fitted, and the inside of the pipe container 20 is filled only with the working fluid and its saturated vapor, Non-condensable gases such as air are completely removed.

Further, the heat absorbing portion 16 in the middle of the EGR pipe 11
Is formed on one end of the heat pipe 18 inserted from a direction substantially orthogonal to the axis of the EGR pipe 11 so as to be exposed to the flow of the exhaust gas 8 and on the outer peripheral surface of the one end of the heat pipe 18. It is possible to apply various shapes to the fins 21. However, regarding the heat transfer surface formed by the fins 21, the exhaust gas 8 of the EGR pipe 11 is It follows the flow.

On the other hand, the heat radiating portion 17 in the middle of the exhaust pipe 10 has substantially the same structure as the heat absorbing portion 16, and is inserted from a direction substantially orthogonal to the axial center of the exhaust pipe 10 and exposed to the flow of the exhaust gas 8. The other end of the heat pipe 18
The heat pipe 18 is composed of a large number of fins 22 formed on the outer peripheral surface of the other end of the heat pipe 18, and the heat transfer surface formed by the fins 22 is arranged to follow the flow of the exhaust gas 8 in the exhaust pipe 10.

If the EGR device is constructed in this way, the heat held by the exhaust gas 8 that is recirculated to the intake side through the EGR pipe 11 is retained by the fins 21 in the heat absorbing portion 16 in the middle of the EGR pipe 11. Is absorbed by one end of the heat pipe 18 via the above, the working fluid is evaporated at one end of the heat pipe 18, and this evaporation causes a pressure difference between the one end side and the other end side of the heat pipe 18, As shown by an arrow A in FIG. 2, the vapor of the working fluid moves toward the heat radiating portion 17 which is the other end portion side of the heat pipe 18.

Then, the vapor that has moved to the heat radiating portion 17 in the middle of the exhaust pipe 10 condenses in the heat radiating portion 17 to release latent heat, and the exhaust gas 8 flowing through the exhaust pipe 10 is passed through the fins 22 and the like. As a result of giving heat, the exhaust gas 8 recirculated to the intake side is cooled.

As shown by arrow B in FIG. 2, the condensate of the working fluid in the heat radiating portion 17 is circulated to the heat absorbing portion 16 by the capillary action of the wick 19, and further evaporation and condensation are repeated. .

Further, particularly in the present embodiment, regarding the engine 1 provided with the turbocharger 2, since the heat radiating portion 17 is provided in the exhaust pipe 10 on the downstream side of the turbine 2b of the turbocharger 2, the turbine 2b is provided. Is expanded by about 100 to 2 from the inlet side of the turbine 2b.
The heat is emitted to the exhaust gas 8 whose temperature has dropped by about 00 ° C., and it is between the exhaust temperature of the heat absorbing portion 16 and the exhaust temperature of the heat radiating portion 17, which can be regarded as substantially equal to the exhaust temperature on the inlet side of the turbine 2b. It is possible to set a sufficiently large temperature difference so that reliable heat transfer by the heat pipe 18 can be performed.

Therefore, according to the above embodiment, the heat held by the exhaust gas 8 that is recirculated to the intake side through the EGR pipe 11 is absorbed by the heat absorbing portion 16, and the absorbed heat is passed through the heat pipe 18. The heat is transferred to the heat radiating portion 17 and the heat radiating portion 1
Since it is designed to release the exhaust gas 8 passing through 7,
The exhaust gas 8 recirculated to the intake side can be cooled without cooling with the cooling water 14.

That is, since the temperature of the exhaust gas 8 of the EGR pipe 11 is reduced as much as possible by heat absorption and then introduced into the EGR cooler 13, the amount of heat collected in the EGR cooler 13 can be reduced, so that the radiator 15 can be reduced. The load can be reduced, and the radiator can be prevented from significantly increasing in size, thereby avoiding deterioration in mountability on the vehicle.

In this embodiment, the EGR cooler 1
Although the case where 3 is used in combination is explained, when the heat absorption by the heat pipe 18 can be expected to absorb sufficient heat, the EGR cooler 13 is unnecessary and the load of the radiator 15 is further reduced. You can also

Further, in the EGR device shown here, in constructing the heat absorbing portion 16 and the heat radiating portion 17, the end portion of the heat pipe 18 exposed to the flow of the exhaust gas 8,
The fins 21 and 22 formed on the outer peripheral surface of the end portion increase the heat exchange area with the exhaust gas 8 by the fins 21 and 22 to efficiently absorb or radiate heat. It is possible to realize the highly practical heat absorbing portion 16 and the heat radiating portion 17 with a simple device configuration so as to reliably perform the above.

The EGR device of the present invention is not limited to the above embodiment, and exhaust gas is extracted from the exhaust manifold in the drawing, but exhaust gas is extracted from the middle of the exhaust pipe. However, the exhaust gas may be returned to the intake manifold, and although one heat pipe is illustrated in the figure for convenience of description, the number of heat pipes used is the target heat exchange amount. , The structure of the heat absorption part and the heat dissipation part is not limited to the example shown in the figure, and further, even in a naturally aspirated engine without a turbocharger, the heat absorption part and the heat dissipation part Similarly, by appropriately setting the temperature difference of the exhaust gas in and
It is needless to say that the device can be applied and various changes can be made without departing from the scope of the present invention.

[0030]

According to the EGR device of the present invention described above,
Various excellent effects as described below can be obtained.

(I) According to the invention described in claim 1 of the present invention, the heat held by the exhaust gas recirculated to the intake side through the EGR pipe is absorbed by the heat absorbing portion, and the absorbed heat is absorbed. Since the heat is transferred to the heat radiating portion via the heat pipe and released to the exhaust gas passing through the heat radiating portion, the exhaust gas recirculated to the intake side can be cooled without water cooling with cooling water. Even if the water-cooled EGR cooler is unnecessary, or even if the water-cooled EGR cooler is used together, the heat collection amount in the EGR cooler can be reduced to reduce the load on the radiator. It is possible to avoid a significant increase in the size of the vehicle, and it is possible to avoid deterioration of vehicle mountability.

(II) According to the second aspect of the present invention, the fins increase the heat exchange area with the exhaust gas to ensure efficient heat absorption or heat dissipation. A high heat absorption part and a high heat dissipation part can be realized with a simple device configuration.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment for carrying out the present invention.

FIG. 2 is a sectional view schematically showing a basic structure of the heat pipe of FIG.

FIG. 3 is a schematic view showing a conventional example.

[Explanation of symbols]

5 Intake pipe (intake passage) 7 Intake manifold (intake passage) 8 exhaust gas 9 Exhaust manifold (exhaust passage) 10 Exhaust pipe (exhaust passage) 11 EGR pipe 16 Heat absorption part 17 Heat sink 18 heat pipe 21 fins 22 fins

Continuation of the front page (56) Reference JP 62-43024 (JP, A) JP 9-32653 (JP, A) JP 57-159909 (JP, A) JP 59-147812 (JP , A) JP-A-8-177486 (JP, A) JP-A-60-125704 (JP, A) JP-A-52-39018 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB) Name) F02M 25/07 580 F02D 21/08 F01P 3/18 F01P 3/20 F01N 3/02

Claims (2)

(57) [Claims] 1. An EGR device in which a part of exhaust gas is extracted from the exhaust passage side through an EGR pipe and recirculated to the intake passage side, and a heat absorbing portion is provided in the middle of the EGR pipe, and the exhaust passage is provided. In the EGR device, a heat radiating portion is provided at a position where the exhaust gas temperature is relatively low downstream of the exhaust gas extraction point in, and the heat radiating portion and the heat absorbing portion are connected by a heat pipe. 2. At least one of a heat absorbing portion and a heat radiating portion is constituted by an end portion of a heat pipe exposed to a flow of exhaust gas and fins formed on an outer peripheral surface of the end portion. The EGR device according to claim 1, wherein: