JP6730175B2 - EGR cooler - Google Patents

Description

The present invention relates to an EGR cooler that cools EGR gas returned from an exhaust passage of an internal combustion engine to an intake passage.

Conventionally, when returning a part of exhaust gas as EGR gas from an exhaust passage of an internal combustion engine to an intake passage, an EGR cooler is provided in an EGR pipe through which the EGR gas flows, and the EGR gas is cooled downstream of the EGR cooler. A configuration is known in which a gas-liquid separation device that separates the liquid generated by doing so from a gas is provided (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

JP, 2016-031042, A JP, 2010-090806, A JP, 2012-062817, A

However, in the case where the EGR cooler and the gas-liquid separation device are independently installed as in the conventional device, a pipe connecting the EGR cooler and the gas-liquid separation device is required. Also, a space for installing the gas-liquid separation device must be secured. Therefore, there is a problem that the device becomes large.
On the other hand, as disclosed in Patent Document 1, the end portion of the swirl flow generation ribbon (the end portion on the outflow side of the gas-liquid two-phase fluid) has a linear edge along the radial direction of the pipe. If so, the liquid adhering to the swirl flow generation ribbon may be re-scattered in the gas at the end of the ribbon without flowing toward the inner peripheral surface of the pipe. Therefore, the liquid once separated mixes with the gas again and flows, which causes a problem that the liquid separation performance deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an EGR cooler capable of improving the separation performance of liquid contained in EGR gas while suppressing an increase in the size of the device. ..

In order to achieve the above object, the EGR cooler of the present invention includes a heat exchange section for exchanging heat between the EGR gas and the refrigerant returned from the exhaust passage of the internal combustion engine to the intake passage, and an intake passage of the exhaust passage and the heat exchange section. An inflow pipe communicating with the port and an outflow pipe communicating with the intake passage and the exhaust port of the heat exchange unit are provided.
The swirl flow generation ribbon that swirls the EGR gas along the inner peripheral surface is disposed inside the outflow pipe, and an exhaust port and a drain port are formed on the downstream side of the swirl flow generation ribbon.
The swirl flow generation ribbon is formed by a plate member that is spirally twisted, and has a first end point that is set at one of the radially outer ends of the swirl flow generation ribbon at the end portion facing the exhaust port. A second end point set on the other end of the radially outer end of the swirl flow generation ribbon, and on the axis of the swirl flow generation ribbon, closer to the heat exchange section than the first end point and the second end point. A center end point set at a position, a first end edge connecting the first end point and the center end point, and a second end edge connecting the second end point and the center end point, Are formed.
Then, a folded structure that is folded toward the EGR gas inflow side is formed at the first edge and the second edge.

Therefore, in the present invention, it is possible to prevent the liquid in the form of liquid droplets from flowing together with the gas when the gas-liquid two-phase fluid is swirled to separate the gas and the liquid while suppressing an increase in the size of the device. ..

1 is an overall system diagram showing an exhaust gas recirculation system for an internal combustion engine to which an EGR cooler of Example 1 is applied. 3 is a cross-sectional view showing an EGR cooler of Example 1. FIG. 5 is a perspective view showing a swirl flow generation ribbon of Example 1. FIG. 3 is a side view of a swirl flow generation ribbon of Example 1. FIG. FIG. 4 is a sectional view taken along line AA in FIG. 3. FIG. 5 is an explanatory diagram showing the flow of EGR gas and separated gas/liquid in the EGR cooler of the first embodiment. FIG. 5 is an explanatory diagram showing a flow of liquid adhering to the swirl flow generation ribbon at the ribbon end portion in the EGR cooler of the first embodiment.

Hereinafter, a mode for carrying out the EGR cooler of the present invention will be described based on Embodiment 1 shown in the drawings.

(Example 1)
First, the configuration of the EGR cooler according to the first embodiment will be described by dividing it into “the entire system configuration of the application example”, “the detailed configuration of the EGR cooler”, and “the detailed configuration of the swirling flow generating ribbon”.

[Overall system configuration of application example]
FIG. 1 is an overall system diagram showing an exhaust gas recirculation system of an internal combustion engine to which the EGR cooler of the first embodiment is applied. The overall system configuration of the application example of the first embodiment will be described below with reference to FIG.

The EGR cooler 20 of the first embodiment is applied to the exhaust gas recirculation system S of the internal combustion engine 1 shown in FIG. Here, the internal combustion engine 1 shown in FIG. 1 is a diesel engine mounted on a vehicle as a drive source for traveling, and has four cylinders (not shown). An intake passage 2 and an exhaust passage 3 are connected to each cylinder.

An intake port 2a is formed at an end of the intake passage 2, and an air cleaner 4 for filtering intake air, a compressor 5a of the turbocharger 5, an intercooler 6 for cooling intake air, and an intake air in order from the intake port 2a side. A throttle valve 7 for adjusting the amount is provided. The exhaust passage 3 is provided with a turbine 5b of the turbocharger 5, an exhaust purification catalyst 8 for purifying the exhaust, and an exhaust throttle valve 9 for adjusting the exhaust flow rate in this order from the internal combustion engine 1 side. A muffler 10 is provided on the downstream side of the exhaust throttle valve 9, and an exhaust port 3a is formed at the end thereof.

The intake passage 2 and the exhaust passage 3 are connected by a low pressure EGR passage 11 and a high pressure EGR passage 12. Here, “EGR (Exhaust Gas Recirculation)” is a technique for extracting a part of exhaust gas after combustion in the internal combustion engine 1 and re-intake it, and is also called exhaust gas recirculation.

The low-pressure EGR passage 11 connects the intake passage 2 upstream of the compressor 5a and the exhaust passage 3 downstream of the exhaust purification catalyst 8. On the other hand, the high pressure EGR passage 12 connects the intake passage 2 downstream of the compressor 5a and the exhaust passage 3 upstream of the turbine 5b.
As a result, in the low pressure EGR passage 11, the exhaust gas that has passed through the turbine 5b is returned to the intake air of the compressor 5a. Further, in the high-pressure EGR passage 12, the exhaust gas before being sucked into the turbine 5b is returned to the air that has passed through the compressor 5a.

An EGR cooler 20 for cooling the exhaust gas guided to the intake passage 2 is provided at an intermediate position of the low pressure EGR passage 11, and intake air is provided at a downstream position of the EGR cooler 20 via the low pressure EGR passage 11. A low pressure EGR valve 14 for adjusting the flow rate of exhaust gas (EGR gas) recirculated to the passage 2 is provided. A high pressure EGR valve 15 for adjusting the flow rate of exhaust gas recirculated to the intake passage 2 via the high pressure EGR passage 12 is provided at an intermediate position of the high pressure EGR passage 12.

[Detailed configuration of EGR cooler]
FIG. 2 is a sectional view showing the EGR cooler of the first embodiment. Hereinafter, the detailed configuration of the EGR cooler 20 according to the first embodiment will be described with reference to FIG.

The EGR cooler 20 of the first embodiment is provided at an intermediate position of the low pressure EGR passage 11 as described above. Here, the EGR pipe that constitutes the low-pressure EGR passage 11 is divided at the position where the EGR cooler 20 is arranged. As shown in FIG. 2, the EGR cooler 20 has an upstream EGR pipe 11a and a downstream EGR pipe 11a. It is interposed between the EGR pipe 11b. The EGR cooler 20 includes a heat exchange section 21, an inflow pipe 22, and an outflow pipe 23.

As shown in FIG. 2, the heat exchange section 21 has a shell 21a, a pair of core plates 21b and 21c, and a large number of tubes 21d.
The shell 21a is a cylindrical hollow tube whose both ends are open, and a pair of core plates 21b and 21c are attached so as to close the end surface of the shell 21a. Both ends of a large number of tubes 21d are fixed to the core plates 21b and 21c in a penetrating state, and the large number of tubes 21d extend axially inside the shell 21a. In addition, each tube 21d is a hollow tube whose both ends are open, and is arranged in a state in which a gap is formed between the tube 21d and another tube 21d.
Further, on the peripheral surface of the shell 21a, a refrigerant inlet 21e connected to the refrigerant introduction pipe 24a and a refrigerant outlet 21f connected to the refrigerant outlet pipe 24b are formed. The coolant introduction pipe 24a and the coolant discharge pipe 24b are pipes through which a coolant such as engine cooling water (LLC: Long Life Coolant) flows. The inner diameter of the shell 21a is larger than the inner diameter of the low pressure EGR passage 11.

The inflow pipe 22 is a hollow pipe whose both ends are open, and one end 22a is connected to the upstream EGR pipe 11a. The other end 22b of the inflow pipe 22 is formed in a bowl shape that covers the outer end surface of the one core plate 21b, and is connected to the end of the shell 21a on the EGR gas inflow side, that is, the intake port of the heat exchange section 21. Has been done.
As a result, the inflow pipe 22 communicates the exhaust passage 3 with the intake port of the heat exchange section 21.

The outflow pipe 23 is a medium space whose both ends are open, and has an inlet pipe 25, an inner pipe 26, and a drain pipe 27.

The inlet pipe 25 is a hollow pipe whose both ends are open, one end 25a is formed in a bowl shape that covers the outer end surface of the other core plate 21c, and the end of the shell 21a on the outflow side of the EGR gas, that is, heat exchange. It is connected to the exhaust port of the part 21. Further, one end 26a of the inner pipe 26 is inserted into the other end 25b of the inlet pipe 25. Further, a drain port 25c opened in the radial direction is formed on the peripheral surface of the other end 25b of the inlet pipe 25.
A swirl flow generation ribbon 30 that swirls the flow of the EGR gas along the inner peripheral surface 25d is disposed inside the inlet pipe 25. A taper surface 25e is formed on the inner peripheral surface 25d of the inlet pipe 25.
The liquid contained in the EGR gas can flow into the drain port 25c by the centrifugal force (swirl force) generated when the EGR gas swirls. Therefore, the opening direction of the drainage port 25c is not limited to the downward direction of the gravity direction, and may be opened in any direction.

The taper surface 25e is an inclined surface that gradually increases the inner diameter of the inlet pipe 25 toward the downstream side in the EGR gas flow direction, and is located downstream of the swirl flow generation ribbon 30 in the EGR gas flow direction. Is formed in. As a result, the inner diameter of the inlet pipe 25 is the smallest in the first region 25α, which is the upstream side of the tapered surface 25e in the EGR gas flow direction, and gradually increases in the second region 25β where the tapered surface 25e is formed. Therefore, the third region 25γ, which is the downstream side of the tapered surface 25e in the EGR gas flow direction, becomes the largest. The swirl flow generation ribbon 30 is arranged in the first region 25α, and the drain port 25c is formed in the third region 25γ.
The inner diameter of the first region 25α in which the swirl flow generation ribbon 30 is arranged is set to be smaller than the inner diameter of the heat exchange section 21.

The inner pipe 26 is formed of a straight pipe member having open outer ends having an outer diameter smaller than the minimum inner diameter of the third region 25γ of the inlet pipe 25. One end 26a is inserted into the other end 25b of the inlet pipe 25, It is installed coaxially with the inlet pipe 25. An exhaust port 26c opened in the axial direction of the inner pipe 26 is formed at the one end 26a. The other end 26b of the inner pipe 26 is connected to the tip of the EGR pipe 11b on the downstream side.
As a result, the outflow pipe 23 communicates the exhaust port of the heat exchange section 21 with the intake passage 2 via the inlet pipe 25 and the inner pipe 26.

A spacer 28 is fitted to the other end 25b of the inlet pipe 25 to seal a gap S1 formed between the inner peripheral surface 25d of the inlet pipe 25 and the inner pipe 26. The spacer 28 has a cylindrical shape surrounding the entire circumference of the inner pipe 26, the outer peripheral surface thereof contacts the inner peripheral surface 25 d of the inlet pipe 25 in an airtight state, and the inner peripheral surface thereof seals against the outer peripheral surface of the inner pipe 26. Are in contact with.
Further, in this spacer 28, the axial position of the end portion located inside the inlet pipe 25 matches the axial position of the most downstream portion of the peripheral portion of the drain port 25c. That is, the spacer 28 does not overlap with the opening area of the drainage port 25c, but is installed without opening a gap in the axial direction with the opening area of the drainage port 25c.

The drainage pipe 27 is formed by a so-called T-shaped pipe in which the second pipe member 27b is connected to the central portion in the axial direction of the first pipe member 27a so as to be orthogonal to each other, and the inlet pipe 25 penetrates the first pipe member 27a. There is. Further, the connection opening 27c formed in the connection portion between the first pipe member 27a and the second pipe member 27b faces the drainage port 25c, and the inlet pipe 25 and the drainage pipe are connected via the drainage port 25c and the connection opening 27c. The second pipe member 27 b of 27 communicates with the second pipe member 27 b. That is, as will be described later, the liquid separated from the EGR gas inside the inlet pipe 25 flows into the second pipe member 27b from the drain port 25c through the connection opening 27c.
Here, the inner diameter of the drain port 25c formed in the inlet pipe 25 is set to be equal to the inner diameter of the connection opening 27c of the drain pipe 27. Then, the second pipe member 27b extends downward in the direction of gravity with respect to the axial direction of the inlet pipe 25, and a tip opening 27e is formed in the tip portion 27d. Here, the “gravitational direction” is the downward direction in FIG. 2, and is the direction in which gravity acts.
The first pipe member 27a and the second pipe member 27b are not limited to circular pipes, and may be square pipes (square pipes) or the like. Further, in the second pipe member 27b shown in FIG. 2, the middle position is gradually tapered toward the tip portion 27d, and the opening area of the tip opening 27e is smaller than the opening area of the connection opening 27c. However, the tip opening 27e and the connection opening 27c may have the same size and can be set arbitrarily.

As shown in FIG. 2, a connection port 29a formed in the upper portion of the water storage tank 29 in the direction of gravity is connected to the tip portion 27d of the second pipe member 27b. Here, the water storage tank 29 is a tank installed below the second pipe member 27b in the direction of gravity, and stores the liquid that has flowed down the second pipe member 27b.
A drain opening (not shown) that can be opened and closed is formed in the lower portion of the water storage tank 29 in the direction of gravity. When the amount of the liquid stored in the water storage tank 29 reaches a certain amount, the stored liquid can be discharged to the outside of the tank through the drainage opening.

Further, in the first embodiment, the ventilation port 26d is formed on the side surface of the inner pipe 26 at the position protruding from the inlet pipe 25. The ventilation port 26d is an opening to which one end 29c of the bypass pipe 29b is connected, and is opened in the radial direction of the inner pipe 26 and downward in the gravity direction. A vent hole 29e is formed on the upper side surface of the water storage tank 29. The vent hole 29e is an opening to which the other end 29d of the bypass pipe 29b is connected.
Here, the bypass pipe 29b is a pipe member whose both ends are open, and the both ends 29c and 29d are connected to the ventilation port 26d and the ventilation port 29e, respectively, so that the space above the water storage tank 29 becomes larger. Communicate with the inside of.
In addition, in FIG. 2, the ventilation port 26d formed in the inner pipe 26 is opened downward in the direction of gravity, but this ventilation port 26d serves to make the water storage tank 29 have a negative pressure via the bypass pipe 29b. Since it is an opening, it may be opened in a direction other than the downward direction of gravity.

[Detailed structure of swirl flow generation ribbon]
FIG. 3 is a perspective view showing a swirl flow generation ribbon of Example 1, and FIG. 4 is a side view of the swirl flow generation ribbon. 5 is a sectional view taken along line AA in FIG. Hereinafter, the detailed configuration of the swirl flow generation ribbon according to the first embodiment will be described with reference to FIGS. 3 to 5.

The swirl flow generation ribbon 30 is formed of a strip-shaped plate member that is spirally twisted, and is arranged in the first region 25α of the inlet pipe 25. The swirl flow generation ribbon 30 has a radial dimension R (see FIG. 4) set to be equal to the inner diameter dimension of the first region 25α, is installed coaxially with the inlet pipe 25, and has a peripheral edge at the inlet pipe 25. Is in contact with the inner peripheral surface 25d.

The swirl flow generation ribbon 30 has a first end point 31a, a second end point 31b, and a center end point 31c at the end portion 31 on the EGR gas outflow side, and also has a first end edge 32a. The 2nd edge 32b is formed.
The first terminal point 31a is set at one of the radially outer ends of the swirling flow generating ribbon 30. The second end point 31b is set at the other end on the radially outer side of the swirl flow generation ribbon 30. Here, the axial position of the first terminal point 31a and the axial position of the second terminal point 31b match, and the terminal line L connecting the first terminal point 31a and the second terminal point 31b is It is orthogonal to the axis O of the flow generation ribbon 30.
The center end point 31c is set on the axis O of the swirl flow generation ribbon 30 and at a position closer to the EGR gas inflow side than the first end point 31a and the second end point 31b, that is, the heat exchange part 21. Has been done.

The first end edge 32a is an end edge of the swirl flow generation ribbon 30 that connects the first end point 31a and the center end point 31c. Further, the second end edge 32b is an end edge of the swirling flow generating ribbon 30 that connects the second end point 31b and the center end point 31c. That is, the end portion 31 of the swirling flow generating ribbon 30 is provided with a V-shaped space region surrounded by the first end edge 32a, the second end edge 32b, and the end line L.

The swirl flow generation ribbon 30 has a folded structure 33 that is folded back to the inflow side of the EGR gas at each of the first end edge 32a and the second end edge 32b.
As shown in FIG. 5, the folded structure 33 includes a first folded piece 33a in which the tips of the first end edge 32a and the second end edge 32b are folded back to one spiral surface 30a side of the swirl flow generation ribbon 30, and a first folded piece 33a. It has the 2nd folding piece 33b which turned back the tip of edge 32a and the 2nd edge 32b to the spiral surface 30b side of the opposite side.
The folded structure 33 is formed between the center terminal point 31c and the first terminal point 31a, and between the center terminal point 31c and the second terminal point 31b. As a result, a gap S2 is formed between the radial end portions of the folded structure 33 and the inner peripheral surface 25d of the inlet pipe 25 (see FIG. 2).

Further, although the swirl flow generation ribbon 30 is arranged in the first region 25α, at least the first end point 31a and the second end point 31b of the end portion 31 have the tapered surface 25e formed on the inner peripheral surface 25d. Area, that is, the second area 25β.

The starting end portion 34 of the swirl flow generating ribbon 30 on the EGR gas inflow side has a first starting end point 34a, a second starting end point 34b, and a central starting end point 34c.
The first start end point 34a is set at one of the start ends on the radially outer side of the swirling flow generating ribbon 30. The second start end point 34b is set to the other start end on the radially outer side of the swirl flow generation ribbon 30. The center start point 34c is on the axis O of the swirl flow generation ribbon 30, and the axial position of the center start point 34c coincides with that of the first start point 34a and the second start point 34b. That is, the center starting point 34c is set on the intersection of the starting line connecting the first starting point 34a and the second starting point 34b and the axis O, and the first and second starting points 34a, 34b and the central starting point 34c. Are arranged along the radial direction of the swirl flow generation ribbon 30. Further, the starting end portion 34 of the swirl flow generation ribbon 30 is erected in the gravity direction.

Next, the operation of the EGR cooler of the first embodiment will be described by dividing it into "EGR gas cooling operation", "gas-liquid separation and liquid re-scattering prevention operation", and "apparatus compaction operation".

[EGR gas cooling action]
FIG. 6 is an explanatory diagram showing flows of the gas-liquid two-phase fluid and the separated gas/liquid in the EGR cooler of the first embodiment. Hereinafter, the cooling operation of the EGR gas in the EGR cooler 20 according to the first embodiment will be described with reference to FIG.

In the exhaust gas recirculation system S shown in FIG. 1, a part of the exhaust gas discharged from the internal combustion engine 1 via the low pressure EGR passage 11 is recirculated from the exhaust passage 3 and is merged with the outside air sucked from the intake port 2a to generate a turbo excess. It is supplied to the compressor 5a of the feeder 5. At this time, if the high temperature EGR gas is recirculated, the filling efficiency of the EGR gas in the internal combustion engine 1 is reduced, and thus it is difficult to reduce the NOx emission amount. Therefore, before merging the EGR gas with the outside air, it is necessary to perform heat exchange between a coolant such as engine cooling water and the EGR gas to cool the recirculating EGR gas.

On the other hand, in the EGR cooler 20 of the first embodiment, as shown in FIG. 6, when a part of the exhaust gas flowing through the exhaust passage 3 flows into the low-pressure EGR passage 11, the EGR gas that is a part of the exhaust gas becomes , Flows into the inflow pipe 22 of the EGR cooler 20 from the upstream EGR pipe 11a. The other end 22b of the inflow pipe 22 is connected to the end of the shell 21a of the heat exchange part 21 on the inflow side of the EGR gas. The end of the shell 21a on the inflow side of the EGR gas is one core. The tube 21d is closed by the plate 21b, and a large number of tubes 21d pass through the one core plate 21b. The multiple tubes 21d extend axially inside the shell 21a and penetrate the other core plate 21c that closes the end of the shell 21a on the EGR gas outflow side.
Therefore, the EGR gas flowing into the inflow pipe 22 passes through the inside of the shell 21a by passing through the large number of tubes 21d, and from the end of the shell 21a on the outflow side of the EGR gas to the inlet pipe 25 of the outflow pipe 23. Is discharged to.

On the other hand, the shell 21a is formed with a refrigerant inlet 21e connected to the refrigerant introduction pipe 24a and a refrigerant outlet 21f connected to the refrigerant outlet pipe 24b. Therefore, the refrigerant flowing through the refrigerant introduction pipe 24a flows into the shell 21a from the refrigerant inlet 21e, flows inside the shell 21a, and flows out to the refrigerant outlet pipe 24b through the refrigerant outlet 21f.

As described above, while the EGR gas flows in the many tubes 21d, the refrigerant flows in the shell 21a having the tubes 21d built therein. Therefore, the EGR gas flows outside the tubes 21d while passing through the many tubes 21d. It is cooled by heat exchange with the flowing refrigerant. As a result, it is possible to prevent a decrease in the filling efficiency of the EGR gas in the internal combustion engine 1 and reduce the air ratio. Further, the combustion temperature in the internal combustion engine 1 can be lowered. As a result, the NOx emission amount can be reduced.

[Gas-liquid separation and liquid re-scattering prevention action]
Hereinafter, the gas-liquid separation and liquid re-scattering prevention actions in the EGR cooler 20 of the first embodiment will be described with reference to FIG.

As described above, the heat exchange section 21 cools the high temperature EGR gas. However, when the EGR gas is cooled, the water contained in the EGR gas becomes liquid as condensed water, and the EGR gas that returns to the intake passage 2 becomes a gas-liquid two-phase fluid in which the gas and the liquid are mixed. Become. In particular, when the heat exchange efficiency in the heat exchange section 21 is high and the cooling performance is good, the amount of condensed water is increased.
Then, when the liquid contained in this gas-liquid two-phase fluid flows into the downstream in the state of being a droplet of a certain size, it collides with the rotor blades of the compressor 5a of the turbocharger 5, May give shock.
On the other hand, in the EGR cooler 20 of the first embodiment, the swirling flow generation ribbon 30 is arranged inside the inlet pipe 25 of the outflow pipe 23 through which the EGR gas in the gas-liquid two-phase fluid flows.

Therefore, as shown in FIG. 6, when the EGR gas flowing into the inlet pipe 25 passes along the swirl flow generation ribbon 30 when passing through the first region 25α in which the swirl flow generation ribbon 30 is installed, the EGR gas swirls. It becomes a flow. Then, due to the centrifugal force imparted by the swirling flow, the liquid having a large mass contained in the EGR gas is guided toward the inner peripheral surface 25d of the inlet pipe 25.

Then, the liquid guided toward the inner peripheral surface 25d of the inlet pipe 25 aggregates into droplets, separates from the gas and remains attached to the inner peripheral surface 25d, and is swirled from the second region 25β from the second region 25β. It flows into the third region 25γ. Then, the liquid flowing into the third region 25γ flows into the drain port 25c formed in the third region 25γ, and flows down the second pipe member 27b through the connection opening 27c of the drain pipe 27 by its own weight. Then, the water flows from the tip opening 27e into the water storage tank 29 and is stored therein.

In the first embodiment, the inner pipe 26 and the water storage tank 29 communicate with each other via the bypass pipe 29b. Therefore, the inside of the water storage tank 29 can be made to have a negative pressure by the air flow flowing through the inner pipe 26, and the flow of the liquid flowing down the drainage pipe 27 can be made smooth. Further, the gas flowing into the water storage tank 29 together with the liquid can be returned to the low pressure EGR passage 11 via the bypass pipe 29b and the inner pipe 26.

Further, the gas flowing through the inlet pipe 25 flows into the inner pipe 26 through the exhaust port 26c opened in the axial direction. Then, this gas flows to the compressor 5 a of the turbocharger 5 via the inner pipe 26.
Here, the outer diameter dimension of the inner pipe 26 is smaller than the inner diameter dimension of the third region 25γ of the inlet pipe 25 because it is inserted into the inlet pipe 25. Therefore, it is possible to prevent the liquid attached to the inner peripheral surface 25d of the inlet pipe 25 from entering the inner pipe 26. Further, the other end 25b of the inlet pipe 25 is fitted with a spacer 28 that closes the gap S1 generated between the inlet pipe 25 and the inner pipe 26. Therefore, the gas can be prevented from leaking out from the other end 25b of the inlet pipe 25, and the gas separated from the gas-liquid two-phase fluid can smoothly flow into the inner pipe 26.

On the other hand, the spiral surfaces 30a and 30b of the swirling flow generating ribbon 30 have an angle with respect to the EGR gas flow direction. Therefore, the liquid contained in the EGR gas collides with the spiral surfaces 30a and 30b and becomes droplets and adheres to the spiral surfaces 30a and 30b. The liquid in a droplet state attached to the spiral surfaces 30a and 30b of the swirl flow generating ribbon 30 is pushed to the downstream side in the flow direction of the EGR gas by the flow of the swirl flow while being attached to the spiral surfaces 30a and 30b. The ribbon 30 flows outward in the radial direction of the swirl flow generation ribbon 30. Further, a part of the liquid in a droplet state moves to the terminal end portion 31 of the swirling flow generating ribbon 30 while being attached to the spiral surfaces 30a and 30b.

Then, when the liquid in a droplet state that has adhered to the spiral surfaces 30a and 30b and has moved to the terminal end portion 31 of the swirling flow generation ribbon 30, reaches the first edge 32a or the second edge 32b, it is indicated by an arrow in FIG. As shown, it flows toward the radially outer side of the swirl flow generating ribbon 30 along the first end edge 32a or the second end edge 32b, and is guided toward the inner peripheral surface 25d of the inlet pipe 25.

At this time, in the first end edge 32a, the first end point 31a located on the radially outer side of the swirl flow generation ribbon 30 is more likely to be discharged from the EGR gas than the center end point 31c located on the axis O of the swirl flow generation ribbon 30. It is located on the downstream side in the flow direction. In addition, in the second end edge 32b, the second end point 31b located on the outer side in the radial direction of the swirl flow generation ribbon 30 has a higher EGR gas level than the center end point 31c located on the axis O of the swirl flow generation ribbon 30. It is located on the downstream side in the flow direction.
On the other hand, the liquid attached to the spiral surfaces 30a and 30b of the swirl flow generation ribbon 30 flows outward in the radial direction of the swirl flow generation ribbon 30 while being swept to the downstream side in the EGR gas flow direction by the swirl flow. ..

Therefore, the extending direction of the first and second end edges 32a and 32b substantially coincides with the flow direction (moving direction) of the liquid pushed by the swirl flow while being attached to the swirl flow generating ribbon 30. As a result, in the end portion 31 of the swirl flow generating ribbon 30, the liquid attached to the spiral surfaces 30a and 30b remains in the state of adhering to the first and second end edges 32a and 32b. It moves radially outward and is guided to the inner peripheral surface 25d of the inlet pipe 25.
That is, even if the liquid is attached to the spiral surfaces 30a and 30b of the swirl flow generation ribbon 30 and separated from the gas, and is attached to the vicinity of the axis O when the liquid is moved to the terminal end portion 31 as it is, It can be guided to the inner peripheral surface 25d of the inlet pipe 25 while being attached to the two end edges 32a and 32b. As a result, it is possible to prevent the liquid separated from the gas from re-scattering from the terminal end portion 31 into the gas. Then, it is possible to improve the liquid separation performance and the liquid collection rate. Since a baffle, a filter, or the like is not used for separating the liquid, the gas flow is not hindered, and the increase in ventilation resistance can be suppressed.

In addition, in the first embodiment, the folded structure 33 is formed on both the first end edge 32a and the second end edge 32b so as to be folded back toward the EGR gas inflow side.
Therefore, the liquid that has adhered to the spiral surfaces 30a and 30b and has moved to the first end edge 32a or the second end edge 32b is separated from the spiral surfaces 30a and 30b by the folding structure 33 and is downstream in the EGR gas flow direction. It is prevented from scattering to the side. That is, the liquid is radially outward of the swirl flow generation ribbon 30 along the gap between the first end edge 32a and the first folded piece 33a or the gap between the second end edge 32b and the second folded piece 33b. It flows toward you.
As a result, the liquid can be guided to the inner peripheral surface 25d of the inlet pipe 25 while preventing the liquid from separating from the first and second end edges 32a and 32b, and the liquid is separated from the EGR gas. The performance can be further improved.

Further, in the first embodiment, the folded structure 33 has the first folded piece 33a folded back to the one spiral surface 30a side of the swirl flow generating ribbon 30 and the second folded piece 33a folded to the opposite spiral surface 30b side. And a piece 33b.
Therefore, it is possible to prevent the liquid from separating from the first and second end edges 32a and 32b regardless of which of the spiral surfaces 30a and 30b of the swirl flow generating ribbon 30 the liquid is attached to.

The folding structure 33 is formed between the center terminal point 31c and the first terminal point 31a, and between the center terminal point 31c and the second terminal point 31b. A gap S2 is formed between both ends in the radial direction and the inner peripheral surface 25d of the inlet pipe 25.
Therefore, the liquid that is prevented from flowing toward the downstream side in the EGR gas flow direction by the folding structure 33 flows toward the downstream side in the EGR gas flow direction through the gap S2 at both radial end portions of the folding structure 33. It becomes possible to flow out.
This prevents the liquid from collecting in the gap between the first end edge 32a and the first folded piece 33a and the gap between the second end edge 32b and the second folded piece 33b, and the inside of the inlet pipe 25 is prevented. The liquid can be promptly guided toward the peripheral surface 25d.

Further, in the first embodiment, the inner peripheral surface 25d of the inlet pipe 25 has the second region 25β in which the tapered surface 25e whose inner diameter gradually increases toward the downstream side in the EGR gas flow direction is formed. That is, at least the first end point 31a and the second end point 31b of the end portion 31 of the swirling flow generating ribbon 30 are inserted in the second area 25β which is an area where the tapered surface 25e is formed.
Therefore, the liquid that has flowed along the first and second end edges 32a and 32b to the first end point 31a and the second end point 31b will flow out onto the tapered surface 25e. As a result, the liquid guided to the inner peripheral surface 25d along the first and second end edges 32a and 32b can be smoothly discharged toward the drain outlet 25c, which promotes the guiding/separation of the liquid. be able to.

[Compactizing device]
Hereinafter, the compacting operation of the device in the EGR cooler 20 according to the first embodiment will be described with reference to FIG.

As shown in FIG. 2, the EGR cooler 20 of the first embodiment has a heat exchange section 21 that cools the EGR gas that is recirculated to the intake passage 2 by exchanging heat between the EGR gas and the refrigerant. Further, the EGR cooler 20 has a swirling flow generation ribbon 30 arranged inside an inlet pipe 25 of an outflow pipe 23 connected to an end of the shell 21 a which is an exhaust port of the heat exchange part 21 on the outflow side of EGR gas. At a position on the downstream side of the swirl flow generation ribbon 30, one end 26a of an inner pipe 26 having a drain port 25c and an exhaust port 26c is inserted.
That is, the EGR cooler 20 of the first embodiment has a heat exchange function of cooling the high temperature EGR gas and a gas-liquid separation function of separating the gas and the liquid from the EGR gas that has been cooled to become the gas-liquid two-phase fluid. ing.

Therefore, inside the outflow pipe 23 of the EGR cooler 20 that cools the EGR gas, it is possible to perform gas-liquid separation for separating the liquid from the EGR gas that has become the gas-liquid two-phase fluid. As a result, the piping required when the gas-liquid separator is independently provided for the EGR cooler can be eliminated, and it is not necessary to secure a space for installing the gas-liquid separator. It is possible to suppress downsizing and achieve compactness.

Further, in this EGR cooler 20, since the liquid can be separated from the EGR gas inside the outflow pipe 23, the liquid cooled to the condensed water in the heat exchange section 21 can be quickly separated from the gas and collected. can do. As a result, it is possible to prevent the liquid generated by condensing the EGR gas from being re-vaporized, and improve the removal rate of the liquid from the EGR gas.

Next, the effect will be described.
In the EGR cooler 20 of the first embodiment, the effects listed below can be obtained.

(1) A heat exchange section 21 for exchanging heat between the EGR gas returned from the exhaust passage 3 of the internal combustion engine 1 to the intake passage 2 and the refrigerant, and an intake port (shell of the exhaust passage 3 and the heat exchange section 21. 21a, which communicates with the EGR gas inflow side end portion 21a, and the intake passage 2 and the heat exchange portion 21 exhaust port (the shell 21a EGR gas outflow side end portion). An outflow pipe 23,
The outflow pipe 23 has a swirl flow generation ribbon 30 that swirls the EGR gas along the inner peripheral surface 25d, and has an exhaust port 26c and a drain port 25c on the downstream side of the swirl flow generation ribbon 30. Formed,
The swirl flow generation ribbon 30 is formed by a plate member that is twisted in a spiral shape, and is set at one end of the swirl flow generation ribbon 30 on the radially outer end of the end portion 31 facing the exhaust port 26c. A first end point 31a, a second end point 31b set on the other of the radially outer ends of the swirl flow generation ribbon 30, and an axis O of the swirl flow generation ribbon 30, and the first end point A center end point 31c set at a position closer to the heat exchange section 21 than the point 31a and the second end point 31b, and connecting the first end point 31a and the center end point 31c. One end edge 32a and a second end edge 32b connecting the second end point 31b and the center end point 31c are formed.
As a result, it is possible to improve the separation performance of the liquid contained in the EGR gas while suppressing the size increase of the device.

(2) The swirl flow generation ribbon 30 has a structure in which the first end edge 32a and the second end edge 32b have a folded structure 33 that is folded back toward the inflow side of the EGR gas.
As a result, in addition to the effect of (1) above, it is possible to make it difficult for the liquid to separate from the first and second end edges 32a and 32b, and to prevent the liquid attached to the swirl flow generation ribbon 30 from re-scattering in the gas. It can be prevented.

(3) The folded structure 33 is formed between the center terminal point 31c and the first terminal point 31a, and between the center terminal point 31c and the second terminal point 31b. It was composed.
As a result, in addition to the effect of (2) above, it is possible to prevent liquid from accumulating in the gap between the first end edge 32a and the first folded piece 33a and the gap between the second end edge 32b and the second folded piece 33b. While preventing, the liquid can be appropriately guided to the inner peripheral surface 25d of the inlet pipe 25.

(4) The inner peripheral surface 25d of the outflow pipe 23 is formed with a taper surface 25e whose inner diameter gradually increases along the EGR gas flow direction.
The swirl flow generation ribbon 30 is configured such that at least the first end point 31a and the second end point 31b are inserted into a region (second region 25β) in which the tapered surface 25e is formed.
Thereby, in addition to the effect of any of the above (1) to (3), the liquid guided to the inner peripheral surface 25d along the first and second end edges 32a and 32b is directed toward the drain outlet 25c. It can be discharged smoothly, and the induction/separation of liquid can be promoted.

(5) In the outflow pipe 23, the swirl flow generation ribbon 30 is arranged inside, and one end 25a is connected to the exhaust port of the heat exchange part 21 (the end of the shell 21a on the outflow side of the EGR gas). And an inner pipe 26 in which one end 26a is inserted into the other end 25b of the inlet pipe 25 and the exhaust port 26c is formed, and an inlet pipe 25 in which the drain port 25c is formed. did.
Thereby, in addition to the effect of any one of the above (1) to (4), it is possible to prevent the liquid attached to the inner peripheral surface 25d of the inlet pipe 25 from entering the inner pipe 26, and the separation performance between the gas and the liquid. Can be improved.

The EGR cooler of the present invention has been described above based on the first embodiment, but the specific configuration is not limited to this embodiment, and deviates from the gist of the invention according to each claim of the claims. Unless otherwise, design changes and additions are allowed.

In the first embodiment, an example is shown in which the folded structure 33 is formed on the first end edge 32a and the second end edge 32b of the terminal end portion 31 of the swirl flow generation ribbon 30. However, the structure is not limited to this, and the folded structure may not be formed in the terminal end portion 31.
Even in this case, the extending directions of the first and second end edges 32a and 32b are substantially the same as the flow direction of the liquid pushed by the swirl flow while being attached to the swirl flow generating ribbon 30. Therefore, at the end portion 31 of the swirl flow generation ribbon 30, the liquid can be guided toward the inner peripheral surface 25d of the inlet pipe 25 while being attached to the spiral surfaces 30a and 30b.

Further, in the first embodiment, the tapered surface 25e is formed on the inner peripheral surface 25d of the inlet pipe 25, and at least the first and second swirling flow generating ribbons 30 are formed in the second region 25β where the tapered surface 25e is formed. An example in which the end points 31a and 31b are inserted is shown. However, an inlet pipe in which the inner peripheral surface 25d does not have a tapered surface may be used.
Even in this case, the liquid separated from the gas-liquid two-phase fluid can flow into the drain port 25c by the swirling flow.

Further, the end portion 31 of the swirling flow generating ribbon 30 arranged in the first region 25α is extended until it is inserted into the third region 25γ of the inlet pipe 25, and the end portion 31 is close to the exhaust port 26c of the inner pipe 26. You may let me.

Further, the first and second end points 31a and 31b of the swirling flow generating ribbon 30 are inserted into the second region 25β where the tapered surface 25e is formed, and the first and second end edges 32a of the swirling flow generating ribbon 30 are inserted. Both ends in the radial direction of the folded structure 33 provided on the pipes 32b may be extended along the inner peripheral surface 25d of the inlet pipe 25. That is, an extension portion that is inserted into the third region 25γ of the inlet pipe 25 may be provided at both radial end portions of the folded structure 33. This extension is formed in a V-shaped cross section by the first and second folding pieces 33a and 33b.
At this time, by extending the tip of the extension portion to a position downstream of the exhaust port 26c of the inner pipe 26, the liquid flowing between the first folding piece 33a and the second folding piece 33b of the folding structure 33 is It can be guided to the inner peripheral surface 25d of the inlet pipe 25 without being scattered in the inner pipe 26.
Further, by maintaining the gap S2 generated between the extension of the folding structure 33 and the inner peripheral surface 25d of the inlet pipe 25, the liquid flowing along the folding structure 33 can be smoothly guided to the inner peripheral surface 25d. You can

Further, in the first embodiment, the starting end portion 34 of the swirling flow generating ribbon 30 is erected in the gravity direction. However, for example, the swirling flow generation ribbon 30 may be installed so that the starting end portion 34 is horizontal with respect to the gravity direction.
In this case, the liquid guided to the inner peripheral surface 25d inside the inlet pipe 25 can easily flow to the lower side of the pipe by its own weight, and the liquid separated from the gas can be effectively prevented from re-scattering. be able to.

Further, in the first embodiment, the shell 21a of the heat exchange section 21 is a cylindrical hollow tube. However, the shell 21a is not limited to this, and may be a rectangular hollow tube containing the laminated flat tubes. In this case, the other end 22b of the inflow pipe 22 and the one end 25a of the inlet pipe 25 of the outflow pipe 23 have a rectangular connecting portion with the shell 21a. In particular, in the inlet pipe 25, the downstream side from the first region 25α in which the swirl flow generation ribbon 30 is arranged needs to be cylindrical in order to make the EGR gas a swirl flow. Therefore, the one end 25a is formed to have a rectangular shape at the portion to be joined to the shell 21a, and also to have a cylindrical shape with the cross-sectional area being gradually reduced.

Further, in the first embodiment, an example in which the water storage tank 29 is connected to the drain pipe 27 and the liquid separated from the EGR gas that has become the gas-liquid two-phase fluid is stored is shown. However, the drain pipe 27 and the water storage tank 29 are It does not necessarily have to be installed. The liquid separated in the inlet pipe 25 and discharged from the drain port 25c may not be stored.

In the first embodiment, the first end edge 32a and the second end edge 32b are both linearly formed, and a V-shaped space region is generated in the terminal end portion 31 of the swirl flow generation ribbon 30. However, it is not limited to this. Since the center end point 31c is set on the inflow side of the gas-liquid two-phase fluid with respect to the first end point 31a and the second end point 31b, the first and second end edges 32a, 32b are curved, The end portion 31 of the swirl flow generation ribbon 30 may be U-shaped.

Furthermore, the axial position of the first end point 31a and the axial position of the second end point 31b do not necessarily have to match, and either one is closer to the gas-liquid two-phase fluid inflow side than the other. It may be set. At this time, the end line L does not have to be orthogonal to the axis O of the swirl flow generation ribbon 30. The center end point 31c may be set on the inflow side of the gas-liquid two-phase fluid with respect to the first end point 31a and the second end point 31b, so that the center end point 31c may extend radially from the axis O of the swirl flow generation ribbon 30. It may be set at a deviated position (a position near the axis O).
That is, the shape of the swirl flow generation ribbon 30 is not limited to that shown in the first embodiment. First and second end points 31a and 31b set at the radially outer ends of the swirl flow generation ribbon 30, and a center end point 31c set on the inflow side of the gas-liquid two-phase fluid. As long as it has the first and second edges 32a and 32b which are the edges connecting these, the setting positions of the end points and the start points and the shape of each edge can be arbitrarily set. You can

Then, in the first embodiment, an example in which the EGR cooler 20 is installed in a so-called horizontal direction in which the EGR gas flow direction is horizontal with respect to the gravity direction has been shown. However, the installation direction of the EGR cooler 20 of the present invention is not limited to this, and the installation direction may be appropriately set depending on the layout and the like in the exhaust gas recirculation system S.
Further, in the first embodiment, an example in which the starting end portion 34 of the swirling flow generating ribbon 30 is erected in the gravitational direction is shown. It is set appropriately according to the layout.

Further, in the first embodiment, the example in which the internal combustion engine 1 is a diesel engine mounted on a vehicle is shown, but the invention is not limited to this, and the EGR cooler of the present invention is applied even if the internal combustion engine 1 is a gasoline engine. It is possible.

Further, each pipe (inlet pipe 25 or the like), the shape of the shell 21a or the like of the heat exchange portion 21, the diameter dimension, the connection location of each member, or the like is not limited to that shown in the first embodiment, and may be arbitrarily set. be able to.

S exhaust gas recirculation system 1 internal combustion engine 2 intake passage 3 exhaust passage 5 turbocharger 11 low pressure EGR passage 12 high pressure EGR passage 20 EGR cooler 21 heat exchange section 22 inflow pipe 23 outflow pipe 25 inlet pipe 25c drain port 25d inner peripheral surface 26 Inner pipe 26c Exhaust port 27 Drain pipe 29 Water storage tank 30 Swirling flow generation ribbon 31 End portion 31a First end point 31b Second end point 31c Center end point 32a First end edge 32b Second end edge 33 Folded structure

Claims (4)

A heat exchange part for exchanging heat between the EGR gas returned from the exhaust passage of the internal combustion engine to the intake passage and the refrigerant; an inflow pipe communicating the exhaust passage with an intake port of the heat exchange part; And an outflow pipe that communicates with the exhaust port of the heat exchange unit,
The outflow pipe has a swirl flow generation ribbon that swirls the EGR gas along an inner peripheral surface, and an exhaust port and a drain port are formed on the downstream side of the swirl flow generation ribbon.
The swirl flow generation ribbon is formed by a plate member that is spirally twisted, and a first end point that is set at one end of the swirl flow generation ribbon on the radially outer side at the end portion facing the exhaust port. A second end point that is set on the other of the radially outer ends of the swirl flow generation ribbon, and on the axis of the swirl flow generation ribbon that is greater than the first end point and the second end point. A first end edge connecting the first end point and the center end point, and a second end point and the center end point, the center end point being set at a position close to the heat exchange portion. and a second edge connecting the door, is formed,
The EGR cooler is characterized in that a folding structure is formed at the first edge and the second edge so as to be folded toward the inflow side of the EGR gas . In the EGR cooler described in claim 1 ,
The EGR cooler is characterized in that the folded structure is formed between the center terminal point and before the first terminal point and between the center terminal point and before the second terminal point. In the EGR cooler according to claim 1 or 2 ,
The inner peripheral surface of the outflow pipe is formed with a tapered surface whose inner diameter gradually increases along the EGR gas flow direction.
In the swirl flow generating ribbon, at least the first end point and the second end point are inserted in a region where the tapered surface is formed. In the EGR cooler according to any one of claims 1 to 3 ,
The outflow pipe is provided with the swirl flow generation ribbon inside, one end of which is connected to an exhaust port of the heat exchange section, and the other end of the inlet pipe, in which the drain port is formed. An EGR cooler comprising: an inner pipe having one end inserted thereinto and the exhaust port formed therein.