EP1975400B1 - Cooling device for recirculated exhaust gas - Google Patents

Description

The invention relates to a cooling device for cooling recirculated exhaust gas (EGR or EGR cooler, exhaust gas cooler) of an internal combustion engine. In this case, the cooling device is designed so that the flow direction of the exhaust gas is reversible by the cooling device. The invention also relates to a method for the regeneration of the cooling device.

The JP 10-281016 discloses a cooling device for cooling recirculated exhaust gases of an internal combustion engine, comprising at least one housing and at least one heat exchanger unit. The housing has a first and a second connection opening. In order to free the heat exchange unit of deposits, a second path is opened simultaneously to close a first path, so that the deposits are blown out.

The WO 01/63175 discloses cooling device (1) for cooling recirculated exhaust gas of an internal combustion engine, comprising at least a housing and at least one heat exchanger unit, wherein the housing has at least a first and a second connection opening, wherein the cooling device is configured such that the flow direction of the exhaust gas through the heat exchanger unit is reversible,

The recirculation of exhaust gas (EGR) into the combustion chamber (s) of an internal combustion engine for mixing with the combustion air or with the combustible air / fuel mixture has long been state of the art. Both in self-igniting internal combustion engines and in internal combustion engines with spark ignition, the recirculation of exhaust gas is used to lower the combustion temperatures and thus to reduce the emission of pollutants. It is advantageous in the recirculation of exhaust gas to additionally cool the exhaust gas before the return, as this can again reduce the combustion temperatures. Therefore, for some time cooling devices for recycled Exhaust gas known and used in various forms, for. B. in the form of Blechrippen- and multi-tube cooling devices.

Each exhaust contains a proportion of unburned, partially burned and / or auskondensierbaren substances. Since, of course, a cooling device for exhaust gas reduces the temperature of the exhaust gas, there is the problem that the above-mentioned components can at least partially condense and precipitate within the cooling device, for. B. in the form of soot deposits. The passages for the exhaust gas through the exhaust gas cooler are slowly added during the use of the cooler and can even block in extreme cases. As a result, the heat exchange or cooling capability is significantly reduced. In addition, the cross-section narrows and the pressure loss across the exhaust gas cooler increases.

The o. G. Deposits form predominantly in the colder part of the cooling device, d. H. near the outlet of the cooling device, since there the exhaust gas has already cooled and so the o. g. Could condense substances at least partially. In the inlet region of the cooling device, the exhaust gas temperature is usually so high that hardly any deposits can be found here.

The DE 198 48 564 discloses a way to counteract this problem of deposits. Shown is a cooling apparatus including a housing in which an exhaust gas recirculation pipe and a cooling fluid pipe are juxtaposed to be parallel with each other, and a heat exchange core member rotatably mounted in the housing and defining a plurality of ducts substantially parallel to the rotation axis of FIG Core element extend, as well as a rotating mechanism which rotates the core element. The plurality of lines of the core member communicates with both the exhaust gas recirculation line and the cooling fluid line. When the core member is rotated, the EGR gas flowing through the exhaust gas recirculation passage is cooled by means of a part of the passages of the core member which have been cooled by means of a cooling fluid flowing through the cooling fluid passage. Moreover, as the core member is rotated, the EGR gas and the cooling fluid flow in opposite directions through the same conduits of the core member, thereby clogging the core member Lines due to unburned substances of the fuel is prevented. The disadvantage here, however, that always residues of the coolant are taken into the exhaust gas circulation line.

It is also known to design cooling devices for exhaust gas recirculation systems switchable. So revealed the DE 10 2004 019 554 an exhaust gas recirculation system consisting of a housing in which a heat exchanger unit, and a bypass channel and a bypass flap are arranged. The housing in turn contains a water jacket, which ensures the cooling of the heat exchanger unit. By actuating the bypass flap, the recirculated exhaust gas flow can now optionally be passed through the heat exchanger unit or past the heat exchanger unit.

The invention is therefore based on the object to provide a cooling device for recirculated exhaust gas, in which the deposits of unburned fuel components within the cooling device can be significantly reduced or even avoided, d. H. There is a regeneration of the cooling device similar to a regeneration of a known particulate filter instead.

According to the invention, this object is achieved by a cooling device having the features of claim 1 or by a method of claim 9.

The cooling device for cooling recirculated exhaust gas of an internal combustion engine includes a housing and a heat exchanger unit. The housing has at least a first connection opening to the inlet of exhaust gas and a second connection opening to the outlet of the exhaust gas. The heat exchanger unit has a first end and a second end. Typically, the exhaust gas flows in a first flow direction through the first port of the housing into the first end of the heat exchanger unit and exits the heat exchanger unit at the second end to then exit through the second port opening the housing. Advantageously, the cooling device is designed such that the flow direction of the exhaust gas through the heat exchanger unit is reversible. By changing the direction of flow, the second end of the heat exchanger unit is now charged with the hot exhaust gases, ie the exhaust gases Now leave the heat exchanger through the first end, ie it is a second flow direction. The hot exhaust gases are now able to dissolve any deposits on the second end of the heat exchanger unit and take along.

Usually, cooling devices for cooling recirculated exhaust gas are designed as a structural unit, wherein the first and second connection openings in the housing are generally designed as flanges. The first port is therefore also called inlet flange (to the inlet of the hot exhaust gases) while the second port is called exhaust port (to the outlet of the then cooled exhaust gases). In addition, two nozzles are usually provided for the inlet and outlet of a coolant and often connected in one piece with the housing. Preferably, the cooling device is designed for cooling recirculated exhaust gas so that the first connection opening, ie the inlet flange for the entry of the exhaust gas into the housing and the second connection opening, ie the outlet flange for the outlet of the then cooled exhaust gas, are identically shaped or dimensioned in that the housing is dismantled, rotated and reassembled in the reverse (second) throughflow direction through the housing and heat exchanger unit.

Alternatively, the cooling device can also be designed such that means are provided for opening the housing in order to be able to remove or introduce the heat exchanger unit. Advantageously, the housing is then opened to reverse the direction of flow, the heat exchanger unit removed and with the reverse flow direction, d. H. returned to the housing with a second flow direction and the housing closed again.

The aforementioned advantageous embodiments are preferably used in so-called tubular heat exchangers or shell-and-tube heat exchangers, wherein these heat exchangers usually consist of a housing and a plurality of tubes through which the exhaust gas flows, wherein the tubes / tubes are surrounded by a coolant and the coolant flows past the tubes / pipes.

In a further preferred embodiment, the housing is double-walled, wherein between both walls, a coolant can flow (so-called water jacket), so that the housing can be cooled by this coolant. Within the housing is at least one heat exchanger, which dissipates the heat of the exhaust gas to the housing, wherein the housing can then conduct the heat to the cooling fluid. The at least one heat exchanger is z. B. a finned heat exchanger or as previously a tube bundle heat exchanger.

The at least one heat exchanger may also consist of segments, for. B. from two units of tube bundles or from two units of fin coolers. It can also z. B. also two or more segments to be integrally connected to a unit whereby it is also possible that a separation of the units z. B. is provided by a partition wall. The advantageous embodiment can also be applied to different types of housings or constructions of the cooling device. Common are z. B. linearly flowed through housing (I-cooler), in which the first connection opening are arranged on one side and the second connection opening on an opposite side of a housing.

Also common are cooling devices in which the first and second connection openings are arranged on a side of the housing, so-called U-cooler. In this case, the exhaust gas flow experiences a deflection within the cooling device. This is usually done by a heat exchanger element in U-shape, d. H. with deflection of the exhaust gas flow within the heat exchanger element achieved. Another variant provides two or more heat exchanger elements, wherein the deflection or reversal of the flow direction of the exhaust gas stream is provided at least partially outside the heat exchanger elements, for. B. by deflection of the exhaust gas flow through the wall of the housing. The two or more heat exchanger elements can be separated, z. B. by a partition. It is also conceivable to connect the two or more heat exchanger elements in one piece with or without a partition wall or walls.

In the variants of the advantageous cooling device described above, the reversal of the flow direction can be achieved by opening the respective housing, Remove the heat exchanger (s) and reinsert the heat exchanger (s) in reverse flow direction.

However, advantageous variants of the previously described cooling device configurations in which means are provided which are suitable for reversing the flow direction through the at least one heat exchanger, without the housing must be opened and without the cooling device dismantled and - as described above - with reverse Flow direction is reinstalled.

The above-mentioned means may, for. B. include at least one valve or a flap, wherein the means are suitably connected to one or more channels such that the flow direction can be reversed by the at least one heat exchanger.

Preferably, the aforementioned means for reversing the flow direction consist of two 4/2-way valves and two additional channels. Here are variants with manual adjustment of the valves as well as with external force actuated adjustment z. B. conceivable by at least one electric motor and / or at least one Vakuumaktuator.

It is also conceivable that a conventional electronic control for an internal combustion engine initiates or carries out a corresponding actuation of the valves, for. B. as described above after a certain period of operation or in vehicles after a certain distance.

In a particularly preferred variant of the invention, the cooling device consists of an at least predominantly cylindrical housing, wherein the housing has a water jacket for the passage of a cooling fluid as described above. Preferably, the first and second connection opening for the exhaust gas are arranged on a common housing side, so it is a cooling device of the U-type. The heat exchanger unit according to the invention consists of two or more segments which are arranged so that the exhaust gas stream entering through the first connection opening at least a first segment in one flows through the first direction and the exhaust gas flow exiting at the second connection opening has previously flowed through at least one second segment in a second flow direction opposite to the first segment. The segments may, as described above, be integrally connected to each other and may have partitions. According to the invention, the heat exchanger unit is designed at least predominantly as a cylinder and rotatably supported in the housing wherein the axis of rotation of the heat exchanger unit is generally parallel to the axis of the housing cylinder, so that one of the two base surfaces of the cylinder points in the direction of the first and second connection opening. Ideally, the axes of housing and heat exchanger unit coincide or are identical. Now, if the heat exchanger unit according to the invention described above consisting of two segments, which preferably each have approximately the shape of a longitudinally-cut half cylinder, rotated by 180 °, so swap the first and the second segment their position, so that as a result in both segments each reverses the flow direction of the exhaust gas.

Alternatively, heat exchanger units of three, four or more segments are conceivable, with a uniform division of the cylinder is advantageous. So z. b. in a heat exchanger unit consisting of 3 segments cover each segment 120 ° with respect to the base. A rotation of the heat exchanger unit to reverse the flow direction would then z. B. 120 ° or 240 ° on the assumption that a segment is temporarily not acted upon by the exhaust gas stream.

The rotation of the heat exchanger unit according to the invention z. B. manually after a certain time or vehicles z. B. done after a certain route.

For rotation of the heat exchanger unit according to the invention suitable means may be provided which allow rotation without the housing must be opened. These means can be operated manually, but it is also conceivable power-driven means. So z. B. an electric motor or a vacuum actuator perform this rotation.

It is also conceivable that a conventional electronic control for an internal combustion engine initiates or carries out a corresponding rotation of the heat exchanger unit, for. B. as described above after a certain period of operation or in vehicles after a certain distance.

In the preferred embodiments of the invention described above is to ensure good heat transfer and a certain ease between the heat exchanger unit and the coolant flowing through the housing, z. B. by application of suitable heat-transferring means between the heat exchanger unit and housing such. B. copper paste.

The invention also relates to a method for the regeneration of a cooling device. Regeneration is understood here as the dissolution or reduction of deposits from combustion residues, as described for. T. has already been described above.

• Bestimmung einer festgelegten Betriebdauer, Wegstrecke oder eines davon abhängigen Kennwertes
• Einleitung einer Drehung einer Wärmetauschereinheit einer Kühlvorrichtung um einen vorbestimmten Winkel nach Erreichen der festgelegten Betriebsdauer, Wegstrecke bzw. Kennwertes.

According to the invention, therefore, the following steps are carried out with one of the devices described above, in particular in the case of the cooling device according to the invention

• Determination of a defined operating time, distance or a dependent characteristic value
• Initiation of a rotation of a heat exchanger unit of a cooling device by a predetermined angle after reaching the specified operating time, distance or characteristic value.

As already shown in the description of the cooling device according to the invention, the direction of flow in individual segments of the heat exchanger unit can be reversed by the rotation of the heat exchanger unit and thus any deposits are dissolved or at least reduced. It is advantageous to carry out the rotation of the at least heat exchanger unit after a certain operating time or distance in order to prevent clogging of the at least one heat exchanger unit. It may also be useful to consider the load, the operating conditions and / or the environmental influences on the internal combustion engine and the rotation of the heat exchanger unit depending on these parameters. This can be z. B. done by forming a characteristic value from the aforementioned parameters wherein the rotation of the heat exchanger unit is initiated upon reaching a predetermined characteristic value.

Fig. 1

eine einfache Ausführung einer Kühlvorrichtung in I-Form zum wechselseitigen Einbau mit z. T. aufgeschnittenem Gehäuse

Fig. 2a, b

eine einfache Ausführung einer Kühlvorrichtung mit einer Wärmetauschereinheit bestehend aus zwei Segmenten in Seitenansicht und Draufsicht ebenfalls mit z. T. aufgeschnittenem Gehäuse

Fig. 3a

eine Ausführung der Kühlvorrichtung in I-Form mit Mitteln zur Umkehr der Durchströmungsrichtung durch die Wärmetauschereinheit mit Darstellung einer ersten Durchströmungsrichtung wobei das Gehäuse teilweise aufgeschnitten dargestellt ist

Fig. 3b

eine Ausführung der Kühlvorrichtung in I-Form mit Mitteln zur Umkehr der Durchströmungsrichtung durch die Wärmetauschereinheit mit Darstellung einer zweiten Durchströmungsrichtung. Das Gehäuse ist wiederum z. T. aufgeschnitten.

Fig. 4a, b

Kühlvorrichtung mit drehbarer Wärmetauschereinheit in Seitenansicht und die Darstellung des Schnittes A-A mit z. T. aufgeschnittenem Gehäuse

Fig. 5

Kühlvorrichtung mit drehbarer Wärmetauschereinheit mit 3 Segmenten im Schnitt A-A

wobei bei allen Figuren gleiche Teile mit den gleichen Bezugszeichen versehen sind.The figures attached to illustrate the invention show:

Fig. 1

a simple embodiment of a cooling device in I-shape for mutual installation with z. T. cut housing

Fig. 2a, b

a simple embodiment of a cooling device with a heat exchanger unit consisting of two segments in side view and top view also with z. T. cut housing

Fig. 3a

an embodiment of the cooling device in I-shape with means for reversing the flow direction through the heat exchanger unit with a representation of a first flow direction wherein the housing is shown partially cut away

Fig. 3b

an embodiment of the cooling device in I-shape with means for reversing the direction of flow through the heat exchanger unit with a representation of a second flow direction. The housing is in turn z. T. cut open.

Fig. 4a, b

Cooling device with rotatable heat exchanger unit in side view and the representation of the section AA with z. T. cut housing

Fig. 5

Cooling device with rotary heat exchanger unit with 3 segments in section AA

wherein in all figures the same parts are provided with the same reference numerals.

FIG. 1 shows the cooling device 1 in a simple embodiment. The cooling device 1 consists of a housing 2 containing a heat exchanger unit 3. Shown is a double-walled design of the housing 2 wherein between the two walls, a coolant can flow, ie the housing 2 is provided with a so-called water jacket 4. The Housing 2 has at the opposite ends in each case a connecting piece 5, 6, through which the coolant can flow or leave the housing again. The heat absorbed by the heat exchanger unit 3 is released to the housing 2 and transported away by the coolant 4. In the embodiment shown, the housing 2 has two ports 7, 8, 9, 10 for the inlet and outlet of exhaust gas in the form of exhaust pipes 7, 9, wherein each exhaust pipe 7, 9 ends in a flange 8, 10. By means of the flanges 8, 10, the cooling device 1 is connected to the exhaust system of an internal combustion engine (not shown), for. B. via screw or clamp connections (not shown). Advantageously, the flanges 8, 10 are now predominantly identically dimensioned or formed, so that the cooling device 1 can be dismantled, rotated and reassembled with the reverse flow direction.

A second, inventive embodiment is in FIG. 2 sketched, where FIG. 2a a side view and FIG. 2b represent a plan view of the cooling device 1 according to the invention. In the double-walled housing 2, that is provided with a cooling water jacket 4 housing 2, a heat exchanger unit 3 is spent, the heat exchanger unit 3 here consists of two segments 3a, 3b. The housing 2 has, as before at the opposite ends depending on a nozzle 5, 6, through which the coolant can flow or leave the housing again. In the embodiment shown, the housing 2 has two ports 7, 8, 9, 10 for the inlet and outlet of exhaust gas in the form of exhaust pipes 7, 9, wherein each exhaust pipe 7, 9 ends in a flange 8, 10. By means of the flanges 8, 10, the cooling device 1 is connected to the exhaust system of an internal combustion engine, wherein in the illustrated embodiment, the terminals 7, 8, 9, 10 are arranged on one side of the housing 2. The exhaust gas to be cooled flows in the illustration shown here through the first port 7, 8 in the cooling device 1, flows through the first segment 3a of the heat exchanger unit 3, is then deflected in an empty space 11 of the housing 2 by 180 °, to then through the second segment 3b of the heat exchanger 3 and the second terminal 9, 10, the cooling device 1 to leave again. Advantageously, the heat exchanger unit 3 can now be removed from the housing 2, rotated 180 ° and returned to the housing 2 to reverse the flow direction through the heat exchanger unit 3. The housing 2 has for this purpose a corresponding configuration (not shown here) z. B. by appropriate separation into two housing halves or housing parts and a detachable connection of the two housing halves or housing parts z. B. by screwing, clips or clamping elements.

The FIGS. 3a and 3b show a further embodiment. Again, the cooling device 1 again consists of a housing 2 containing a heat exchanger unit 3. The housing is again executed double-walled and has a cooling water jacket 4, wherein the nozzles 5, 6 ensure the supply and discharge of the coolant. The exhaust gas is as previously by the two exhaust ports 7, 8, 9, 10 of the cooling device 1 supplied or removed. In addition, means 13, 14, 15, 16 are provided to reverse the flow direction through the cooling device 1. Here, the exhaust gas flow to flow through the cooling device 1 in a first flow direction, starting from the exhaust pipe 17 directly through the valve 15 via the flange 8 and the exhaust pipe 7 is composed of two suitable valves 15, 16 and two additional exhaust ducts directed into the cooling device 1. Cooled down, the exhaust gas stream leaves the cooling device 1 through the exhaust pipe 9 via the valve 16 and the exhaust pipe 18. To reverse the flow direction (second flow direction) of the cooling device 1, the incoming exhaust gas flow from the valve 15 is deflected into the exhaust passage 13. From the exhaust duct 13, the valve 16 directs the exhaust gas flow through the flange 10 and the exhaust pipe 9 through the cooling device 1, which is now passed in a second flow direction. The exhaust gas leaves the cooling device through the exhaust pipe 7 and the flange 8 and is guided in the valve 15 in the second exhaust passage 14. The valve 16 then carries the exhaust gas into the exhaust pipe 18 to the engine. The valves 15, 16 can also be switched so that the exhaust gas flow first passes through the exhaust gas line 14 on the way to the cooling device, and then continues to be cooled down through the exhaust gas line 13.

FIG. 4 shows an embodiment of the cooling device 1 according to the invention, wherein the housing 2 houses a rotatable heat exchanger unit 3. The housing is again double-walled and has a cooling water jacket 4, wherein the Nozzle 5, 6 to ensure the supply and discharge of the coolant. The exhaust gas is as previously by the two exhaust ports 7, 8, 9, 10 of the cooling device 1 supplied or removed, wherein the second exhaust port 9, 10 is covered by the first exhaust port in the sketch. According to the invention, the heat exchanger unit 3 of at least two segments 3a, 3b, wherein the heat exchanger unit 3 is rotatably mounted about the axis 19 and wherein the axis 19 is identical here with the housing center line. A void 11 takes over - as before - the deflection of the exhaust stream from the first segment 3a in the second segment 3b of the heat exchanger unit 3. According to the invention, the heat exchanger unit is now rotated by 180 ° about the axis 19 for reversing the flow direction through the heat exchanger unit. As a result, the second segment 3b is now first flowed through by the exhaust gas, while the first segment 3a is now in the flow direction in second place.

FIG. 5 shows a section through an alternative embodiment of the cooling device 1 described above in which the heat exchanger unit consists of 3 segments 3a, 3b, 3c. Here, only two segments are flowed through during operation of the cooling device, while the third segment is not flowed through. A regeneration is then initiated by a rotation through 120 ° or 240 °, wherein, as before, the segments 3a, 3b, 3c change their flow direction or a previously flowed through segment is no longer flowed through.

LIST OF REFERENCE NUMBERS

1

cooler

2

casing

3

Heat exchanger unit (segments)

3a, 3b, 3c

Segments of the heat exchanger unit

4

coolant

5

Nozzle for coolant

6

Nozzle for coolant

7

exhaust pipe

8th

flange

9

exhaust pipe

10

flange

11

whitespace

12

arrow

13

channel

14

channel

15

Valve

16

Valve

17

exhaust pipe

18

exhaust pipe

19

Centerline / axis

Claims (9)

1. Cooling device (1) for cooling recirculated exhaust gas of an internal combustion engine, comprising at least one housing (2) and at least one heat exchanger unit (3), with the housing (2) having at least one first and one second connecting opening (8, 10), with the cooling device (1) being designed such that the throughflow direction of the exhaust gas through the heat exchanger unit (3) can be reversed,
   characterized in that
   the exhaust-gas flow which enters at a first connecting opening (8) flows through at least one first segment (3a) of the heat exchanger unit (3) in a first direction and the exhaust-gas flow which emerges at a second connecting opening (10) firstly flows through at least one second segment (3b) of the heat exchanger unit (3) in a second flow direction which is opposite to the first segment, with the heat exchanger unit (3) being arranged rotatably within the housing (2), and with the reversal of the throughflow direction of the exhaust gas through the heat exchanger unit (3) being effected by means of a rotation of the heat exchanger unit (3) within the housing (2).
2. Cooling device (1) according to Claim 1,
   characterized in that
   the heat exchanger unit (3) is designed at least predominantly as a cylinder and/or the housing (2) has at least predominantly the shape of a cylinder.
3. Cooling device (1) according to Claim 1 or 2,
   characterized in that
   the axes (18) of the predominantly cylindrical housing (2) and of the predominantly cylindrical heat exchanger unit (3) run predominantly parallel.
4. Cooling device (1) according to Claim 3,
   characterized in that
   the axes (19) of the predominantly cylindrical housing (2) and of the predominantly cylindrical heat exchanger unit (3) coincide with one another or are identical.
5. Cooling device (1) according to Claim 3,
   characterized in that
   means are provided for rotating the heat exchanger unit (3) without it being necessary for the housing (2) to be opened.
6. Cooling device (1) according to Claim 5,
   characterized in that
   the means are operated manually or by external force.
7. Cooling device (1) according to Claim 6,
   characterized in that
   the actuation by external force is initiated and/or carried out by a conventional electronic controller for an internal combustion engine.
8. Cooling device (1) according to one of the preceding claims,
   characterized in that
   the housing (2) is of double-walled design and has a cooling water jacket (4).
9. Method for regenerating a cooling device (1) for cooling exhaust gases of internal combustion engines, comprising at least one housing (2) and at least one heat exchanger unit (3), with the housing (2) having at least one first and one second connecting opening (8, 10), with the cooling device (1) being designed such that the throughflow direction of the exhaust gas through the heat exchanger unit (3) can be reversed, with the exhaust-gas flow which enters at a first connecting opening (8) flowing through at least one first segment (3a) of a heat exchanger unit (3) in a first direction and the exhaust-gas flow which emerges at a second connecting opening (10) firstly flowing through at least one second segment (3b) of a heat exchanger unit (3) in a second flow direction which is opposite to the first segment, with the heat exchanger unit (3) being arranged rotatably within the housing (2), and with the reversal of the throughflow direction of the exhaust gas through the heat exchanger unit (3) being effected by means of a rotation of the heat exchanger unit (3) within the housing (2), comprising the following steps:

   - determining a defined operating duration or distance

   - initiating the rotation of the heat exchanger unit (3) of the cooling device (1) by a predetermined angle after the defined operating duration or distance is reached.

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