JPH11141408A - Recycled exhaust gas cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device excellent in cooling performance, small and light, manufacturable at a low cost, and is excellent in durability, having excellent mounting property on a vehicle, in an EGR cooler which cools circulating exhaust gas to improve the volumetric efficiency of an engine and improves engine performance such as output and fuel consumption when exhaust gas is recycled, which is effective for reducing NOx in exhaust gas of a vehicular engine, especially, a diesel engine. SOLUTION: A ceramic cylindrical heat exchanging core member 36 having a plurality of passed passages having small cross sectional area, is arranged by being crossed an EGR gas passage 20 and a cooling fluid (normally air) passage 44, a belt groove 66 is arranged in the peripheral surface of a metallic casing 38 fitted around the core member 36 by shrinkage-fitting and the like, a belt 72 is wound between the belt groove 66 and a pulley 70 arranged on the output shaft 68 of an electric motor M, and the core member 36 and the metallic casing 38 are integrally rotated by a belt transmission device, thereby EGR gas is cooled.

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, if high-temperature exhaust gas is directly mixed 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. Burning deteriorates and N
_Causing an increase in other harmful components in the exhaust gas, such as an increase in Ox;
There are problems such as. 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) Hereinafter, sometimes referred to as an EGR cooler) has already been proposed and put to 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 cooler and increase the flow rate thereof, it is necessary to increase the cross-sectional area of the heat exchange tube. Therefore, there is a problem that the volume of the EGR cooler is further increased, the mountability on the vehicle is deteriorated, and the weight is further increased. In addition, the above plate fin type and multi-tube type EGR
Since the cooler always has EGR gas flowing in only one direction,
Unburned fuel adheres to the pipeline wall, and as the time of use elapses, the pipeline cross-sectional area decreases, and as the pressure loss increases,
There is a problem that heat exchange performance deteriorates.

[0006] On the other hand, although not related to an EGR cooler, conventionally, as a heat exchange element, a short columnar or disk-shaped outer shape is provided, and a large number of small cross-sectional areas substantially parallel to the center line are provided therein. A heat exchange device having a ceramic core member provided with a passage is disclosed in, for example, Japanese Utility Model Laid-Open No. 14570/1990.
No. 6,086,045. (Hereinafter, this type of heat exchange device is sometimes referred to as a previously proposed device)

[0007] The schematic structure of the above-mentioned proposed device will be described with reference to the conceptual configuration diagram of FIG. In the figure, reference numeral 010 generally indicates a heat exchange device, and the heat exchange device 010 includes a substantially cylindrical housing 012 and a housing 01.
2 is provided with a ceramic core member 014 housed so as to be freely rotatable around an axis OO.

The core member 014 has a short columnar or disk-like outer shape, and is provided therein with a number of small-section passages 016 parallel to the rotation axis OO.
A suitable bonding means 018 is attached to the outer periphery of the core member 014.
The ring gear 020 is mounted via the
20 meshes with the pinion 022.

Further, the core member 014 is rotatably supported by a support shaft 024 (shown by a two-dot chain line in the figure) coaxially arranged with respect to the center line OO of the housing 012. ing. The pinion 022 is connected to and driven by the output shaft 028 of the electric motor 026.

The end plate 030 of the housing 012 has half-moon or D-shaped openings 034 and 036 separated by a diametrically extending bridge portion 032, and one of the openings 0
34 has a passage 0 for a relatively low temperature fluid (usually air).
The other opening 036 communicates with a high-temperature gas passage 040 such as a high-temperature fluid such as exhaust gas of an engine or exhaust gas of an exhaust turbine.

In the above proposed device, when the electric motor 026 is energized during operation of the engine or the like, the output shaft 02
The ring gear 020 rotates at a low speed via the pinion 8 and the pinion 022, and the core member 014 rotates around the support shaft 024. High-temperature gas passage 0 accompanying rotation of core member 014
The high-temperature gas flows from 40 to a substantially half-moon core portion and the same core portion is heated, while a low-temperature fluid, such as air, flowing from the low-temperature fluid passage 038 to the substantially half-moon core portion contacts the heated core portion. Heated by heat exchange.

In the heat exchanger 010, when it is used as an EGR cooler, it is necessary to elastically support a metal ring gear 020 via a bonding means 018 outside the ceramic core member 014. ,
There is a disadvantage that the cost required for joining the ring gear 020 is extremely high. Further, since the gas sealing of the core member 014 is performed by a sliding member (not shown) on the outer peripheral portion of the end plate 030 which abuts on the axial end surface of the core member at the outer peripheral portion in the radial direction. There is a problem that the outer diameter of the core member 014 is increased, which leads to an increase in cost.

[0013]

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.

[0014]

SUMMARY OF THE INVENTION 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 and a cooling fluid passage. A heat exchange core member that cools the exhaust gas by passing the exhaust gas through a core portion cooled by the cooling fluid, and a metal member that is fitted around the outer peripheral surface of the core member so as to be relatively non-rotatable. And the core member is constituted by a ceramic columnar member having a large number of small cross-sectional area passages penetrating substantially parallel to the rotation axis thereof,
A recirculation exhaust gas cooling device is characterized in that a rotation mechanism for integrally rotating the casing and the core member around the rotation axis is provided in the metal casing.

In the present invention, it is preferable that the metal casing is fitted around the outer peripheral surface of the core member by press fitting or shrink fitting. Further, in the present invention, the core member and the metal casing are connected in a rotational direction by a torque transmission member extending in a substantially radial direction over an inner peripheral portion of the casing and an adjacent core portion of the core member. It is desirable. Further, in the present invention, the rotating mechanism is rotated by a driving device such as a belt groove provided on an outer peripheral surface of the metal casing, a belt fitted in the belt groove, and an electric motor. And a pulley for driving the belt.

[0016]

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.

[0017] The EGR valve 24, the load sensor of the temperature signal _{T w,} the engine 10 of the temperature sensor 28 for sensing rotational speed signal _{N c} of the rotational speed sensor 26 for detecting the rotational speed of the engine 10, a cooling water temperature of the engine 10 load signal _{L e} detected by 30, the intake pressure signal _{P 1} of the pressure sensor 32 for detecting the intake pressure in the intake passage 18, 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 is rotated by an electric motor M and a rotation mechanism described in detail later.
Heat exchange core member 36 which is rotationally driven around O at a slow speed
(Hereinafter simply referred to as a core member), and a metal casing 38 is fitted on the core member 36. A pair of first and second support plates 40 and 42 are disposed at both ends in the axial direction of the casing 38 and the core member 36, and the EGR passage 20 and the cooling fluid passage are respectively provided on the support plates 40 and 42. 44 are connected. A cooling gas such as air is preferably circulated through the cooling fluid passage 44 as shown by an arrow in the drawing, and the cooling air includes discharge air of a separately provided air compressor or blower or cooling of the engine 10. A traveling wind or the like passing through a radiator (not shown) for cooling water can be appropriately used.

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 cross-sectional view taken along the line III-III of FIG. 2.) It is formed from a columnar member that rotates around, preferably, a ceramic material such as cordierite, 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 a partially enlarged view of FIG. 4, a plurality of small cross-sectional through-passages 46 substantially parallel to the rotation axis OO. Are formed. In the illustrated case, the passage 46 has a square cross-sectional shape with a length h on one side, and the thickness t of the partition wall 46a that divides each passage 46 is within a range allowable 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 46a as small as possible, the aperture ratio of the core member 36, that is,
The ratio of the total cross-sectional area of the passage 46 to the cross-sectional area of the circle surrounded by the outer diameter of the core member 36 can be made sufficiently large, and a large heat exchange area can be ensured. The pressure loss of the fluid can be reduced and its flow rate can be increased.

The casing 38 externally fitted to the core member 36 is preferably a cylindrical member made of a metal material having excellent heat resistance such as SUS310 stainless steel, and having excellent stretchability and workability. It is shrink-fitted at about 900 ° C. and fixed to the outer peripheral surface of the core member 36. In the illustrated embodiment, the casing 38 and the core member 3
6 means that both end faces in the axial direction are the rotation axis O- of the core member.
It is formed so as to be included in the same plane perpendicular to O.

The core member 36 and the casing 3 fitted to the outer peripheral surface thereof, preferably by shrink fitting or press fitting.
In order to improve the bonding strength (particularly the bonding strength at a high temperature) with respect to the relative rotation about the rotation axis OO with the rotation axis 8,
As shown in FIG. 3, it is preferable to provide one or more blades or torque transmitting members 48 extending substantially radially from the inner peripheral portion of the casing 38 into the core member 36. As shown, the torque transmitting member 48 is connected to the rotation axis O.
The cross-section in a plane perpendicular to -O is rectangular or parallelogram-shaped, and is formed by a strip-shaped member extending in the direction of the rotation axis, and one end of each radially outer side is welded or a casing by appropriate fixing means. 38. On the other hand,
The groove or cavity 50 on the core member 36 side for receiving the torque transmitting member 48 can be formed at the same time as the extrusion of the core member 36, or can be formed on the outer peripheral portion of the core member 36 formed in a cylindrical shape. It can also be formed by processing.

On the axial end surface of the casing 38, an annular portion 52 and a diametrical bridge portion 54 having both ends fixed to the annular portion 52 are provided.
The first and second seal plates 56 and 58 having a front shape (hereinafter referred to as a θ-shape) in which a D-shaped or half-moon-shaped fluid passage is formed between the first and second seal plates 56 and 58 are arranged. First seal plate 5
6, in the illustrated embodiment, is directly interposed between one end face of the casing 38 and the first support plate 40, and
It is attached to the support plate 40 by a detent pin (not shown) or the like so as to prevent relative rotation. On the other hand, the second seal plate 58 is disposed between the other end surface of the casing 38 and the second support plate 42 via a seal diaphragm 60 made of a thin plate material such as a heat-resistant θ-shaped stainless steel material or Inconel. And is attached to the second support plate 42 by a rotation preventing pin (not shown) or the like so as to prevent relative rotation.

The first and second seal plates 56 and 58
Preferably, the inner diameter of each annular portion 52 is substantially equal to the inner diameter of the casing 38 and thus the E
It is formed so as not to reduce the passage area of the GR gas and the cooling fluid. When the core member 36 and the casing 38 rotate integrally around the rotation axis OO, the annular portions 52 of the first and second seal plates 56 and 58 are attached to the axial end surfaces of the casing 38. Since the bridge portion 54 slides while contacting, and the bridge portion 54 slides while contacting the axial end surface of the core member 36, it is desirable that the bridge portion 54 be made of a material having a small coefficient of friction at high temperature, for example, aluminum bronze.

Rollers for abutting the first and second support plates 40 and 42 on the outer peripheral surface of the casing 36 to rotatably support the casing 38 and the core member 36 about a rotation axis OO. A shaft 64 of 62 is preferably
Three or more rollers 62 are arranged at equal intervals in the circumferential direction, and a plurality (two in the illustrated case) of rollers 62 are arranged on each roller shaft 64 at intervals in the axial direction.

Further, on the outer peripheral surface of the casing 38,
One or more (one in the case shown) belt groove, preferably a belt groove 66 for a V-belt, having a center line in a plane orthogonal to the rotation axis OO is provided, and one of the belt grooves is supported. A pulley 70 having a belt groove cooperating with the belt groove 66 is mounted on an output shaft 68 of the electric motor M mounted on a plate, for example, the second support plate 42. V belt 72 between
Is wound. The belt groove 66, the V-belt 72, and the pulley 70 form a rotation mechanism that integrally rotates the casing 38 and the core member 36.

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. Controlled and flows through the EGR passage 20. On the other hand, the casing 38 and the core member 36 are rotated through the pulley 70 fixed to the output shaft 68 of the electric motor M and the V belt 72 wound around the belt groove 66 on the outer peripheral surface of the casing 38. It is gently rotated integrally.

Due to the rotation of the core member 36,
Axially penetrating passage 4 with a large number of small cross-sections
The cooling fluid from the cooling fluid passage 40 flows into almost half of the six,
The partition wall 46a is cooled. On the other hand, almost the remaining half of the passages 4
6, the EGR gas from the EGR passage 20 flows, so that the high-temperature EGR gas is cooled in contact with the partition wall 46a, and then supplied to the intake passage 18 of the engine 10, mixed with the intake air and mixed with the intake air. It is supplied to the combustion chamber. Since the cooled EGR gas is supplied to the combustion chamber of the engine together with the intake air will increase the volumetric efficiency, engine output, fuel efficiency is improved, and also improves the NO _x or the like exhaust emissions. At this time, the seal diaphragm 60 interposed between the second support plate 42 and the second seal plate 58 causes the cooling fluid and E
The leakage of the GR gas to the outside is prohibited, and the first seal plate 56 and the casing 38 are in airtight contact with each other by the elasticity of the seal diaphragm 60, so that the leakage of the cooling fluid and the EGR gas from this portion to the outside is also prevented. Effectively prevented.

The core member 36 has a heat exchange area per unit volume, that is, the total area of the partition walls 46a of the passages 46.
Since the width can be increased more than the conventional plate fin type EGR cooler, when compared with an EGR cooler having the same capacity, the size is extremely small and light, and the mountability to a vehicle or an engine can be effectively improved. The ceramic core member 36 has the advantage of being excellent in durability since rust is not generated and corrosion due to various components in the exhaust gas is small.

Further, as in the previously proposed device, a metal ring gear 0 is mounted on the outer periphery of a ceramic core member 014.
Filling the gap between the two to fill the elastomer and vulcanizing at a high temperature of about 200 ° C. to solidify, or inserting a spring into the gap between them and frictionally joining them using the spring force It does not require expensive bonding means 018 such as a method for performing the cutting operation, and further, does not need to provide a ring gear 020 or a pinion 022 which is expensive for gear cutting, and a metal casing 38 externally fitted to the outer peripheral surface of the core member 36. The belt 72 is provided with a simple belt groove, and the belt 72 is
This is very advantageous because a simple and inexpensive rotating mechanism for driving the casing 38 and rotating the casing 38 and the core member 36 integrally is used.

Further, the ring gear 0 mounted on the core member 014 via the bonding means 018 as in the previously proposed device.
The core member 36 is sealed on its outer peripheral surface by an externally fitted metal casing 38 without the need for a large-sized housing 012 having an outer peripheral seal for accommodating all the cooperating pinions 022.
Only the two end faces in the axial direction need to be sealed by the first and second seal plates 56 and 58 and the seal diaphragm 60, so that the structure can be made simple, compact, lightweight and inexpensive. Further, since the core member 36 rotates,
Since the EGR gas and the cooling fluid flow in the same passage, and the flow directions of the two are opposite, there is an advantage that clogging of the passage due to unburned matter can be effectively prevented.

In the above embodiment, a large number of passages 46 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 partitioned by an arbitrary number of radial partition walls 46a. In the above-described embodiment, the EGR gas and the cooling fluid are formed so as to flow through the passages 46 in a substantially semicircle in the opposite direction.
The six groups may have different cross-sectional areas, and the flow direction may be the same. Further, EG in FIG.
Some or all of the EGR gas cooled by the R cooler 22 may be supplied directly to the combustion chamber via an independent port formed in the cylinder head of the engine 10 without passing through the illustrated intake passage 18. it can.

In the above embodiment, the core member 3
6 and a metal casing 38 which is fitted to the outer peripheral surface by press-fitting or shrink-fitting, a substantially radially extending wing or torque transmitting member 48 is provided. Is compact and lightweight, and the torque required for driving is small. Therefore, when sufficient torque transmission is performed only by shrink-fitting the casing 38, the torque transmission member 48 can be omitted. In the illustrated embodiment, the V-belt is used to rotate the casing 38 integrally with the core member 36. However, since the transmission torque is sufficiently small as described above, a flat belt can be adopted. Further, the durability at high temperatures can be further improved by using a metal belt widely used for CVT, which is a kind of automobile transmission. Furthermore, in the illustrated embodiment, the seal diaphragm 60 is interposed only on the side of the second seal plate 58 that contacts one end of the core member 36 and the metal casing 38 in the axial direction, but the first diaphragm that contacts the other end thereof. A similar seal diaphragm can be arranged on the seal plate 56 side.

[0035]

As described above, the recirculation exhaust gas cooling apparatus according to the present invention includes an exhaust gas recirculation passage for recirculating a part of engine exhaust gas together with intake air into a cylinder of the engine and a cooling fluid passage. A heat exchange core member that is interposed and rotates and cools the exhaust gas by passing the exhaust gas through the core portion cooled by the cooling fluid, and is fitted around the outer peripheral surface of the core member so as to be relatively non-rotatable. A metal casing, and the core member is constituted by a ceramic columnar member having a large number of small cross-sectional area passages penetrating substantially parallel to the rotation axis thereof, A rotating mechanism for integrally rotating the casing and the core member around the rotation axis is provided in the metal casing, and the engine body is cooled by effectively cooling the EGR gas. Output improved efficiency, fuel consumption, exhaust emissions, etc. durability superior in a simple structure and small weight that can improve further the EG mountability is excellent in the vehicle
There is an advantage that the R cooler can be provided at low cost.

In the recirculating exhaust gas cooling device, the outer peripheral surface of the core member is easily and easily sealed by fitting the metal casing to the outer peripheral surface of the core member by shrink fitting or press fitting. There is an advantage that the two can be integrated to transmit the torque required for rotation of the core member to the core member via the casing. Further, it is preferable that the core member and the metal casing are connected in a rotational direction by a torque transmitting member extending in a substantially radial direction over an inner peripheral portion of the casing and an adjacent core portion of the core member. According to the configuration, there is an advantage that the integrity of the core member and the metal casing in the rotation direction can be ensured even at a high temperature. Also,
The rotating mechanism, a belt groove provided on the outer peripheral surface of the metal casing, a belt fitted in the belt groove,
It is preferable to comprise a pulley that is driven by a drive device such as an electric motor to drive the belt, and this configuration can provide a structurally extremely simple and inexpensive core member rotation mechanism. This has the advantage that the size and weight of the entire apparatus can be reduced.

[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 sectional view taken along the line III-III in FIG. 2;

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

FIG. 5 is a schematic configuration diagram showing a device already proposed.

[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 metal casing, 40 first support plate, 42 second
Supporting plate, 44: cooling fluid passage, 46: passage, 46a: partition wall of passage 46, 48: torque transmitting member, 56: first seal plate, 58: second seal plate, 60: seal diaphragm, 62: roller, 64: roller shaft, 70: pulley, 7
2: V belt, M: electric motor.

Claims (4)

[Claims] An exhaust gas recirculation passage for recirculating a part of the exhaust gas of an engine together with intake air into a cylinder of the engine and a cooling fluid passage are rotated, and a core portion cooled by the cooling fluid is exhausted. A heat exchange core member that cools the exhaust gas by passing the gas, and a metal casing that is externally fitted to the outer peripheral surface of the core member so as to be relatively non-rotatable, wherein the core member has a rotation axis thereof. On the other hand, it is composed of a ceramic columnar member having a large number of small cross-sectional area passages penetrating substantially in parallel,
A recirculation exhaust gas cooling device, wherein a rotating mechanism for integrally rotating the casing and the core member around the rotation axis is provided on the metal casing. 2. The recirculation exhaust gas cooling device according to claim 1, wherein the metal casing is fitted around the outer peripheral surface of the core member by press fitting or shrink fitting. 3. The method according to claim 1, wherein the core member and the metal casing are connected in a rotational direction by a torque transmitting member extending in a substantially radial direction over an inner peripheral portion of the casing and an adjacent core portion of the core member. Claim 1.
Or the recirculation exhaust gas cooling device according to claim 2. 4. A belt groove provided on an outer peripheral surface of the metal casing, a belt fitted in the belt groove, and a belt device which is rotated by a driving device such as an electric motor to rotate the belt. The recirculation exhaust gas cooling device according to claim 1, further comprising a pulley for driving the exhaust gas.