JPH11132112A - Recirculation exhaust gas cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a cooling performance, form a device in a compact size, lighten a weight, reduce costs, improve durability, and improve a performance for loading the device on a vehicle, in an EGR cooler for cooling circulating exhaust gas, in the case where exhaust gas is recirculated efficiently for reducing NOx in exhaust gas of an engine. SOLUTION: A ceramic made cylindrical heat exchange core member 36 provided with many penetrating passages 42 having a small cross section crossing an EGR gas passage 20 and a cooling fluid passage 40, is arranged, and is rotated loosely. A passage part cooled by the cooling fluid is cooled by bypassing EGR gas, and thereby, the volumetric efficiency of an engine is increased. The core member 36 is formed as a ceramic material such as cordierite whose passage opening rate is 50 to 80%, hydraulic diameter of a passage is 0.3 to 1.0 mm, porosity is 20 to 30%, and sliding members 56, 62 arranged on an end wall side of a housing which is brought into sliding-contact with the core member is formed as a solid lubricating material such as copper, carbon, fluoride, and oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recirculation exhaust gas cooling system for a diesel engine mounted on an engine, particularly a truck or the like.

[0002]

2. Description of the Related Art Conventionally, in order to reduce nitrogen oxide (NO _x ), which is a harmful component in exhaust gas discharged from a diesel engine for vehicles such as trucks, a part of the exhaust gas of the engine is taken into the intake air of the engine. Exhaust gas recirculation devices that are mixed into the exhaust gas to suppress the combustion temperature and pressure are known. (Hereinafter, in some cases, this device is referred to as an EGR device, and the exhaust gas that is recirculated is referred to as an EGR gas.)

[0003] In the engine with the EGR device, by mixing high-temperature exhaust gas into the intake air, the intake air temperature rises and the volume efficiency decreases, so that the performance of the engine, such as output and fuel efficiency, deteriorates. In addition, there is a problem that combustion deteriorates to cause an increase in other harmful components in exhaust gas such as an increase in black smoke. Therefore, various recirculation exhaust gas cooling devices (which reduce the intake air temperature by cooling the EGR gas, thereby relatively improving the volumetric efficiency, and improving the engine output, fuel consumption and exhaust gas performance) Less than,
In some cases, referred to as an EGR cooler) has already been proposed and put into practical use.

In the conventional EGR coolers, plate fin type and multi-tube type cooling devices having a structure essentially similar to a radiator for cooling engine cooling water are widely used. There is a problem that the pressure loss at the time of passing through the EGR is large, and the volume and weight of the EGR cooler required to supply a required amount of cooled EGR gas to the engine become relatively large.

Further, in order to reduce the NO _x in the exhaust gas even when attempting to increase the recirculation amount of EGR gas further particularly high intake air pressure in an engine with a supercharger, the EGR gas intake passage In order to reduce the pressure loss of the exhaust gas passing through the plate fin type and the multi-tube type EGR coolers and increase the flow rate thereof, the pipe cross-sectional area of the heat exchanger (core portion) is required. Since it is necessary to increase the EGR cooler, the volume of the EGR cooler is further increased, so that the mountability on the vehicle is deteriorated and the weight is further increased. In addition, the plate fin type and the multi-tube type E
In the GR cooler, the EGR gas always flows in only one direction, so that unburned fuel or the like adheres to the pipeline wall, and as the usage time elapses, the pipeline cross-sectional area decreases, the pressure loss increases, and heat exchange occurs. There is a problem that the performance, that is, the cooling performance is deteriorated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a good cooling performance and a small pressure loss of exhaust gas passing therethrough.
It is an object of the present invention to provide an EGR cooler which is small and lightweight, can easily secure a GR gas flow rate, has excellent mountability on a vehicle, is inexpensive and has excellent durability.

[0007]

In order to achieve the above object, the present invention provides an exhaust gas recirculation passage for recirculating a part of exhaust gas of an engine together with intake air into a cylinder of the engine.
A heat exchange core member that rotates while being interposed across the exhaust gas recirculation passage and the cooling fluid passage, and cools the exhaust gas by passing the exhaust gas through a core portion cooled by the cooling fluid. Another object of the present invention is to provide a recirculation exhaust gas cooling device constituted by a ceramic cylindrical member having a large number of small cross-sectional area passages penetrating substantially parallel to its rotation axis.

According to the above construction, the core member made of a ceramic cylindrical member having excellent heat resistance and capable of securing a sufficiently large heat exchange area per unit volume is provided with an exhaust gas recirculation passage of an engine and a cooling fluid. By arranging and rotating over the passage, a small-sized EGR cooler capable of effectively cooling the EGR gas and having excellent heat exchange efficiency can be provided at low cost.

In the present invention, the opening ratio of the core member is preferably 50 to 80%. By setting the opening ratio in the above range, the pressure loss of the exhaust gas and the cooling fluid flowing in the core member is reduced. , The cooling efficiency of the EGR gas is increased, and the flow rate of the EGR gas, that is, the amount of the EGR gas supplied to the engine, can be increased.

In the present invention, the hydraulic diameter of the passage formed in the core member is desirably 0.3 to 1.0 mm, and the cross-sectional shape of the EGR gas passage is set in the above range. , The EGR gas and the cooling fluid, in particular, the pressure loss of the former is reduced to increase the heat exchange efficiency and to effectively cool the EGR gas.
The R cooler can supply a sufficient amount of EGR gas to the engine. Further, in the present invention, the porosity of the ceramic material forming the core member is 10 to 30.
%. By setting the porosity of the ceramic material in the above range, the core member can be inexpensively manufactured by using a ceramic carrier manufacturing technology and equipment widely used for purifying exhaust gas of a vehicle engine. It will be available.

In the present invention, the sliding member which slides on the passage opening end of the core member in the housing for accommodating the core member is a solid lubricating material such as a copper-based, carbon-based, fluoride-based or oxide-based solid member. It is desirable to be made of wood. By using a copper-based, carbon-based, fluoride-based and oxide-based solid lubricant, particularly aluminum bronze, as the sliding member that slides on the end face of the rotating ceramic core member, friction at high temperatures can be reduced. The capacity of the driving device can be reduced, and breakage such as loss of the end surface of the core member can be effectively prevented. In addition, the passage of the EGR gas and the cooling fluid passage are the same as the core member rotates, and the passage of the EGR gas and the cooling fluid in the opposite directions causes clogging of the passage due to unburned fuel. Can be prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. First, in the schematic configuration diagram of FIG. 1, reference numeral 10 denotes a four-cycle multi-cylinder diesel engine (four cylinders in the illustrated case) for a vehicle, and the engine 10 includes an exhaust passage 1 including an exhaust manifold 12.
4 and an intake passage 18 including an intake manifold 16. In addition, an exhaust gas recirculation passage 20 (hereinafter, sometimes referred to as an EGR passage) having an upstream end communicating with an appropriate position of the exhaust passage 14 and an downstream end communicating with an appropriate position of the intake passage 18 is provided. The EGR passage 20 is provided with an EGR cooler generally indicated by reference numeral 22, and a variable opening EGR valve 24 for controlling the flow rate of recirculated exhaust gas upstream of the EGR cooler 22 in the EGR passage 20. Is interposed.

The EGR valve 24 is provided with a rotation speed signal Ne of a rotation speed sensor 26 for detecting the rotation speed of the engine 10, a water temperature signal Tw of a temperature sensor 28 for detecting the cooling water temperature of the engine 10, and a load sensor 30 of the engine 10. The detected load signal Le, the intake pressure signal Pi of the pressure sensor 32 for detecting the intake pressure in the intake passage 18, and the other engine 10
Is received by the control unit 34, which sets the appropriate amount of EGR gas supplied to the engine 10 and sets the valve opening according to the amount of EGR gas.

The EGR cooler 22 includes a heat exchange core member 36 (hereinafter, simply referred to as a core member) that is driven to rotate around a rotation center line OO at a slow speed by a driving device such as an electric motor. And a housing 38 in which the EGR passage 20 communicates and a cooling fluid passage 40 communicates with the housing 38. In the cooling fluid passage 40, a cooling gas such as air is preferably circulated as indicated by an arrow in the drawing, and the cooling air includes discharge air of a separately provided air compressor or blower or cooling water of the engine 10. A traveling wind or the like passing through a radiator (not shown) that cools the air can be used as appropriate.

The detailed structure of the EGR cooler 22 is shown in a sectional view of FIG. 2, a front view of FIG. 3, and a partially enlarged view of FIG. (Note that FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 3, and FIG. 3 is a front view viewed from the EGR gas inlet side.) The core member 36 is arranged around a center line OO. It is formed of a rotating cylindrical member, preferably, cordierite, by a ceramic material such as β-spodumene,
It is manufactured by, for example, an extrusion molding method, similarly to a carrier of a catalytic converter widely used for purifying exhaust gas of a conventional vehicle engine.

Inside the core member 36, as shown in the partially enlarged view of FIG. 4, a plurality of small cross-sectional through-passages 42 substantially parallel to the rotation axis OO. Are formed. In the illustrated case, the passage 42 has a square cross-sectional shape with a length h on one side, and the thickness t of the partition wall 44 that divides each passage 42 is within an allowable range in terms of processing technology and strength of the core member 36. The thickness is formed as thin as possible, for example, t = 0.1 mm.

By setting the thickness t of the partition wall 44 as small as possible, the opening ratio of the core member 36, that is, the total sectional area of the passage 42 with respect to the sectional area of a circle surrounded by the outer diameter of the core member 36, is determined. The ratio can be made sufficiently large, and as described later, the pressure loss of the EGR gas and the cooling fluid passing through the core member 36 can be reduced, and the flow rate can be increased.

The core member 36 is accommodated in a cylindrical housing 38 to which ducts or ducts 20 'and 40' for limiting the EGR passage 20 and the cooling passage 40 are connected to both end faces in the direction of the axis OO. Have been. The above housing 3
8 includes a cylindrical outer peripheral wall 48 and end plates 50 and 52 at both ends in the axial direction. As shown in FIG. 3, the end plate 52 on the downstream side of the EGR passage has an annular outer frame portion 52a. And a diametrical bridge portion 52b (hereinafter referred to as a θ-shaped shape).
Is detachably fixed to a flange 48a formed at the end of the outer peripheral wall 48 by a number of bolts 54. On the other hand, the end plate 50 on the upstream side of the EGR passage has the same θ-shape as the end plate 52 at the other end, and is fixed to the other end opening of the outer peripheral wall 48 by welding or the like.

The EGR passage 20 is connected to one of the half-moon-shaped openings of the end plates 50 and 52 having the θ-shape, and the cooling fluid passage 40 is connected to the other half-moon-shaped passage. Between the end plate 50 on the upstream side of the EGR passage and the opposite end face of the core member 36, a θ-shaped shape made of a solid lubricant such as a copper-based, carbon-based, fluoride-based, or oxide-based material, preferably made of aluminum bronze. The sliding member 56 is pressed against the upstream end face of the core member 36 by a sealing diaphragm 58 made of a thin plate material such as heat-resistant stainless steel or Inconel. The seal diaphragm 58 blocks communication between the annular space 60 between the outer peripheral wall 48 of the housing 38 and the outer peripheral surface of the core member 36 and the EGR passage 20.

Similarly, between the end plate 52 on the downstream side of the EGR passage 20 and the opposing end face of the core member 36, a sliding member 62 preferably made of aluminum bronze having a .theta. And a seal diaphragm 64 made of a thin plate material such as stainless steel or Inconel made of a thin plate material such as stainless steel or Inconel and having a D-shape in front view and provided on the EGR passage side.
Thus, the core member 36 is pressed against the downstream end of the core member 36. The seal diaphragm 64 blocks communication between the annular space 60 and the EGR passage 20. An appropriate number of ventilation holes 66 are formed in the outer peripheral wall 48 so that the annular space 60 communicates with the atmosphere, and the temperature of the space is prevented from rising.

At the center of the sliding members 56 and 62, core support plates 68 and 70, which are formed in a disk shape coaxially with the core member 36, are fitted to be rotatable relative to each other. In 70, one or more (two in the illustrated case) pre-formed eccentrically arranged eccentrically arranged in the core member 36 and fitted to a cylindrical space 72 penetrating in the axial direction are provided for driving assistance. Support shafts 76 projecting from both ends of the pipe member 74 are fitted respectively.

In addition, any one of the support plates,
One end of a drive shaft 78 is screwed and fixed to the core support plate 70 on the downstream side of the EGR passage. The other end of the drive shaft 78 is driven by a key 80 for driving an electric motor with a speed reducer (not shown). It is connected to the output shaft 82 of the device. Note that FIG.
In FIG. 3, reference numeral 84 denotes the end plates 50 and 52 and the seal plates 5 to prevent the seal plates 56 and 62 from rotating together with the rotation of the core member 36.
6 and 62 are detent pins interposed respectively.

In the above configuration, during the operation of the engine 10, a part of the exhaust gas discharged into the exhaust passage 14 has a flow rate controlled by the EGR valve 24 whose opening is controlled by the control unit 34 in accordance with the operating state of the engine 10. Controlled and flows through the EGR passage 20. On the other hand, the output shaft 82 is gently rotated by the drive device, and the core support plate 70 is rotated at the same angular velocity via the key 80 and the drive shaft 78. The rotation of the support plate 70 is transmitted to the core member 36 via the pipe member 74 and the core support plate 68, and the core member 36
Rotates slowly.

By rotation of the core member 36, in the case shown in FIG.
Axially penetrating passage 4 with a large number of small cross-sections
The cooling fluid from the cooling fluid passage 40 flows through approximately half of the two,
The partition wall 44 is cooled. On the other hand, approximately half of the remaining passages 42
Since the EGR gas flows from the EGR passage 20 through the EGR passage 20, the high-temperature EGR gas is cooled in contact with the partition wall 44, and then supplied to the intake passage 18 of the engine 10 and mixed with the intake air to combust the engine 10. Supplied to the room.

Since the cooled EGR gas is supplied to the combustion chamber of the engine together with the intake air, the volumetric efficiency is increased, the output and fuel consumption of the engine are improved, and the performance of exhaust gas such as black smoke is improved.

As described above, since the ceramic core member 36 is driven at the central portion through the core support plates 70 and 68 and the pipe member 74, the core member 36 is formed despite the inherent brittleness of the ceramic material. The member 36 can be rotated safely and reliably while enduring the load of the driving torque, and can be driven by a small, lightweight, and inexpensive driving structure. Further, the sliding members 56 and 62 slidingly contacting both end surfaces in the axial direction with the rotation of the core member 36 are made of a copper-based, carbon-based, fluoride-based or oxide-based solid lubricant, particularly preferably aluminum bronze. , The coefficient of friction under high temperature is sufficiently small,
There is an advantage that the end face is not damaged, and further, since casting is possible, it is easy to form a complicated shape.

Next, the core member 36 is made of a ceramic material, in particular, cordierite or β-spodumée, and has a porosity of 10 to 30%, so that it has been widely used as a catalytic converter for exhaust gas purification of a vehicle engine. The core member 36 having a large number of passages 42 having a small cross-sectional area and the cylindrical space 72 is easily and inexpensively manufactured by extrusion molding by applying the manufacturing technology of the catalyst carrier which is mass-produced. There are benefits to gain.

Further, the heat exchange capacity of the core member 36 having a given volume suitable for mounting on a vehicle with the EGR gas and the cooling fluid, particularly the former, is a heat exchange area in contact with the EGR gas or the like, that is, Partition wall 4 that limits many passages 42
4 and the pressure loss of the EGR gas flowing through the passage 42, that is, the flow rate of the EGR gas flowing through the core member 36. In particular, in the case of an engine equipped with a turbocharger that drives a gas turbine using exhaust gas from the engine as a working medium and drives an air compressor that pressurizes intake air with the turbine, the intake pressure in the intake passage 18 Is higher, the differential pressure between the exhaust gas pressure and the intake pressure becomes smaller,
Essentially, the amount of supply of the EGR gas to the engine 10 tends to be reduced. Therefore, the reduction of the pressure loss is particularly important in securing the flow rate of the EGR gas.

FIG. 5 is a cross in the plan view of an aperture ratio [delta] _c% (i.e. a number of core members 36 a cross-sectional area in a plane perpendicular to the rotational axis O-O of the passage 42 of the core member 36 of the core member 36 The figure shows the correlation between the value obtained by dividing the area by 100 and multiplying by 100) and the increase / decrease in the pressure loss rate, that is, the change in the pressure loss when the opening ratio is set to 10%. The figure shows
C = 16F (α) LνGρ / (πD ² ), that is, the passage 42
, And the diameter of a circle having a cross-sectional area equivalent to the cross-sectional area of the passage 42, that is, the hydraulic diameter D _h = 1 mm. As can be seen, the pressure loss with increasing aperture ratio [delta] _c increases rapidly, from the relationship between the strength of the partition walls 44 partitioning the passages 42, shown in vertical line Z ₁ and Z ₂ in FIG. As described above, it is clear that the region of 50% or more and 80% or less is practically suitable. In the equation representing the constant C, F (α)
Is a function of the passage shape that determines the friction coefficient of the passage 42, L is the axial length of the passage 42, ν is the kinematic viscosity coefficient of the EGR gas or the cooling fluid, G is the flow rate of the EGR gas or the cooling fluid, ρ
Is the density of the EGR gas or the cooling fluid, and D is the outer diameter of the core member 36.

Next, FIG. 6 shows C = 1 as in FIG.
(Constant number), the passage 42 under the condition of the opening ratio δ _c = 10%.
FIG. 4 is a diagram showing the hydraulic diameter D _h (mm) of the graph as abscissa and the increase / decrease (fold) of the pressure loss rate as ordinate. As shown, the hydraulic diameter _{D h} is 0.3mm or more 1mm range of vertical lines _{Z 3} was confirmed to be good.

FIG. 7 shows the hydraulic diameter D _h (m) on the horizontal axis.
m) and temperature efficiency (%) on the vertical axis, constant C ′ = (λN _u D ² ) / (8 cpG) = 0.01 [where λ is the thermal conductivity of EGR gas or cooling fluid. , _Nu is E
Nusselt number of GR gas or cooling fluid, D is core member 36
, Cp is the specific heat of EGR gas or cooling fluid, G is E
Indicates the flow rate of GR gas or cooling fluid. Β = passage 42
FIG. 4 is a diagram illustrating a relationship between a hydraulic diameter _Dh and a temperature efficiency (%) under a condition of a heat transfer area per unit volume (m ² / m ³ ) = 1000. As indicated by a vertical line Z ₄ in the drawing, when the hydraulic diameter less than 1mm passage 42, the temperature efficiency is obvious that a good efficiency is obtained in 90%.

FIG. 8 shows the constant C 'as in FIG.
= 0.01 and hydraulic diameter D _h = 0.5 mm, unit heat transfer area β (m ² / m ³ ) and temperature efficiency (%)
Those of examining the relationship between, as shown in the vertical line Z ₅ in the figure, the heat transfer area β in a unit volume was found to be good temperature efficiencies of more than about 95% over 1000 to obtain .

Comprehensively observing the diagrams shown in FIGS. 5 to 8, it is advantageous that the opening ratio of the core member 36 is 50 to 80%, and the passage 42 provided in the core member 36 is advantageous.
It has been confirmed that the hydraulic diameter is advantageously 0.3 to 1.0 mm, whereby the pressure loss is small, the EGR gas cooling performance is excellent, the compactness and weight are excellent, the mountability is excellent, the durability and It became clear that an EGR cooler with excellent reliability was obtained.

In the above embodiment, a large number of passages 42 provided in the core member 36 are formed so as to have a square cross section in a plane perpendicular to the core member axis OO. Rectangular cross-sectional shape with different side lengths,
Alternatively, the passage may have a polygonal cross section of an arbitrary shape such as a regular pentagon or a regular hexagon, and may be a concentrically arranged passage having a fan-shaped cross section defined by an arbitrary number of radial partition walls 44. Further, in the above embodiment, the EGR gas and the cooling fluid are formed so as to flow through the passages 42 in a substantially semicircle in the facing direction, respectively.
The cross-sectional areas of the groups may be different areas, and the flow directions may be the same. Further, as the driving means of the core member 36, the driving shaft 78 may be driven via a gear or a belt interlocking with the crankshaft of the engine 10. Further, a part or all of the EGR gas cooled by the EGR cooler 22 in FIG. 1 is directly passed through an independent port formed in the cylinder head of the engine 10 without passing through the illustrated intake passage 18. Can also be supplied.

[0035]

As described above, the recirculation exhaust gas cooling device according to the present invention has an exhaust recirculation passage for recirculating a part of the engine exhaust gas together with intake air into a cylinder of the engine, and an exhaust recirculation passage. And a heat exchange core member that rotates while being interposed across the cooling fluid passage and that cools the exhaust gas by passing the exhaust gas through a core portion cooled by the cooling fluid, wherein the core member has a rotation axis thereof. Characterized in that it is constituted by a ceramic columnar member having a large number of small cross-sectional area passages penetrating substantially in parallel with each other and effectively cooling the EGR gas to combust the engine. E that can be supplied to the room, improve the volumetric efficiency of the engine and improve the output, fuel efficiency, exhaust gas performance, etc., is small and light, has excellent durability, and is excellent in mounting on vehicles. There is an advantage that can provide R cooler inexpensively.

In the recirculating exhaust gas cooling device, by setting the opening ratio of the core member to 50 to 80%, the pressure loss of the EGR gas and the cooling fluid is small, and the core member having a given volume has a large amount. There is an advantage that a good and sufficiently cooled EGR gas flow rate can be obtained. Further, by setting the hydraulic diameter of the passage formed in the core member to 0.3 to 1.0 mm, the EG is improved.
It is possible to achieve both a reduction in the pressure loss of the R gas and the cooling fluid and an increase in the heat exchange efficiency.
The cooler has the advantage that a large amount of sufficiently cooled EGR gas can be supplied to the engine. Further, by setting the porosity of the ceramic material forming the core member to 10 to 30%, a core member made of cordierite, β-spodumene, or the like, which is widely used as a carrier of an exhaust gas purifying catalytic converter, can be used. There is an effect that the carrier can be manufactured at low cost by utilizing the manufacturing technology and equipment. Further, a sliding member that slides on a passage opening end of the core member in the housing that houses the core member is a copper-based, carbon-based,
The frictional resistance between the sliding member and the ceramic core member at high temperatures is small due to the fact that it is made of a solid lubricant such as fluoride or oxide, and damage such as chipping at the end of the core member may occur. And the torque required for rotating the core member is small, and the capacity of the drive unit can be reduced. Further, since the sliding member can be formed by casting, the manufacturing cost can be reduced. is there.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram of an entire engine including a recirculation exhaust gas cooling device according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the EGR cooler 22 in FIG. 1 (a cross-section taken along line II-II in FIG. 3).

FIG. 3 is a front view of the EGR cooler 22 shown in FIG.

FIG. 4 is a partially enlarged front view of a core member 36 in FIG.

FIG. 5 is a diagram showing a relationship between an opening ratio of the core member 36 and a pressure loss rate.

FIG. 6 is a diagram showing a relationship between a hydraulic diameter of a passage 42 of a core member 36 and a pressure loss rate.

FIG. 7 is a diagram showing a relationship between a hydraulic diameter of a passage 42 of a core member 36 and temperature efficiency.

FIG. 8 is a diagram showing a relationship between a unit heat transfer area of the core member 36 and temperature efficiency.

[Explanation of symbols]

10 engine, 14 exhaust passage, 18 intake passage, 2
0: exhaust gas recirculation passage (EGR passage), 22: recirculating exhaust gas cooling device (EGR cooler), 24: EGR valve, 3
4 ... Control unit, 36 ... Heat exchange core member, 3
8 housing, 40 cooling fluid passage, 42 passage, 4
4. Partition wall of passage, 48 ... outer peripheral wall of housing, 50 and 52 ... end plate, 56 and 62 ... sliding member, 5
8 seal diaphragm, 68 and 70 core support plate
Reference numeral 72 denotes a cylindrical space, 74 denotes a drive assisting pipe member, 78 denotes a drive shaft, and 82 denotes an output shaft.

Claims (5)

[Claims] An exhaust recirculation passage for recirculating a part of the exhaust gas of the engine together with intake air into a cylinder of the engine;
A heat exchange core member that rotates while being interposed across the exhaust gas recirculation passage and the cooling fluid passage, and cools the exhaust gas by passing the exhaust gas through a core portion cooled by the cooling fluid. A recirculation exhaust gas cooling device comprising a ceramic cylindrical member having a large number of small cross-sectional area passages penetrating substantially parallel to the rotation axis thereof. 2. The recirculation exhaust gas cooling device according to claim 1, wherein an opening ratio of the core member is 50 to 80%. 3. The recirculation exhaust gas cooling device according to claim 1, wherein a hydraulic diameter of the passage formed in the core member is 0.3 to 1.0 mm. 4. The recirculation exhaust gas cooling device according to claim 1, wherein the porosity of the ceramic material forming the core member is 10 to 30%. 5. A sliding member which slides on a passage opening end of the core member in the housing for accommodating the core member is made of a solid lubricant such as a copper-based, carbon-based, fluoride-based or oxide-based lubricant. The recirculation exhaust gas cooling device according to any one of claims 1 to 4, wherein: