EP3085942B1 - Exhaust gas recirculation module with replaceable heat exchanger cassette - Google Patents

Description

The invention relates to an exhaust gas recirculation module for an internal combustion engine, in particular of a motor vehicle, with an exhaust gas recirculation valve, with which a volumetric flow of rückzuführendem exhaust gas can be determined, and a heat exchanger in which the recirculated exhaust gas can be cooled, wherein the heat exchanger comprises a replaceable heat exchanger cassette and the heat exchanger a heat exchanger housing having an access opening closed by a valve housing of the exhaust gas recirculation valve, the heat exchanger cassette being inserted through the access opening into the heat exchanger housing, wherein the valve housing is connected to the heat exchanger housing by a flange connection, clamped, caulked or crimped thereto.

In internal combustion engines, exhaust gas is usually taken from the exhaust pipe and admixed with the combustion air. This is for the reduction of nitrogen oxides (NOx) and compliance with emission limits in accordance with applicable regulations.

The exhaust gas can for example be taken directly from the exhaust manifold and be reintroduced on the intake side of the internal combustion engine. Depending on the conditions, the exhaust gas is either cooled before it is supplied to the combustion air, or it is supplied uncooled.

In order to cool the exhaust gas, the exhaust gas recirculation module has an exhaust gas cooler through which the exhaust gas can be passed. If the exhaust gas is to be supplied uncooled, a bypass is opened (for example, by a vacuum box that opens or closes a bypass flap valve), so that the exhaust gas flows through a bypass channel and bypasses the heat exchanger. The amount of exhaust gas that is recycled as a whole, is controlled by a control valve that allows, for example, map-controlled the desired volume flow rate.

Steadily increasing environmental regulations and associated, reduced emission limits require new, higher-quality control systems in the exhaust gas recirculation area. Depending on the engine variant (engines with three, four, six, ... cylinders), the recirculating volume flow of exhaust gas is different.

So far, however, in the prior art, the heat exchanger for the cooling of the recirculated exhaust gas is designed for the most powerful engine variant, and this heat exchanger is then installed in low-performance engines. The reason for this is that different variants lead to additional development costs. Furthermore, it should be noted that the individual components of the heat exchanger have quite high material and processing costs (stainless steels, cast stainless steel, sheets with high degree of deformation, furnace soldering with temperatures above 1000 ° C).

The EP 0 930 429 A2 shows an exhaust gas recirculation device comprising an exhaust gas cooler with a cooling insert, which is arranged in a channel through which the cooling liquid flows. This cooling insert can be made in the manner of a cartridge and is inserted through an opening, which is then closed by a housing.

The DE 10 2006 039 497 A1 , which is considered as the closest prior art, shows an exhaust gas cooler, which is part of an exhaust gas recirculation system. The exhaust gas cooler has a cooler cassette, which is inserted into a housing, which is then closed by a housing part, in which an exhaust valve is arranged.

The DE 10 2010 014 843 A1 shows an exhaust gas recirculation module, which consists of a total of four different housing parts. The cooling module here two exhaust ducts are arranged to return sufficient amounts of exhaust gas in large-volume engines

The object of the invention is to optimize the exhaust gas recirculation module to the effect that lower total costs result even taking into account the development effort.

This object is achieved by the subject of the independent claim. Advantageous embodiments are the subject of the dependent claims.

To achieve this object, the invention provides an exhaust gas recirculation module of the type mentioned above, that the heat exchanger cassette is provided with a sealing flange which is clamped between the heat exchanger housing and the valve housing, and that the heat exchanger cassette is provided on the exhaust gas downstream side with a plug connection. Furthermore, the invention provides a modular system for a heat exchanger of an exhaust gas recirculation module for internal combustion engines of the aforementioned type, with a Heat exchanger housing, a valve housing and a plurality of heat exchanger cassettes, which differ in terms of their heat exchanger capacity, wherein in the heat exchanger housing that heat exchanger cassette is installed, which is adapted to the heat exchanger requirements of the respective internal combustion engine. The invention is based on the idea to use a largely standardized heat exchanger, which is used with one and the same heat exchanger housing and with the same valve housing for different internal combustion engines, ie for internal combustion engines, which differ in terms of volume flow of rückzuführendem exhaust. Depending on the volume flow, however, a suitable heat exchanger cassette is inserted into the heat exchanger housing, that is, in the case of a large volume flow, a cassette with a greater heat exchanger capacity than at a smaller volume flow. This has the advantage that in terms of the heat exchanger housing and the valve housing large quantities are possible, resulting in lower unit costs. In addition, different EGR valves need not be designed and designed. However, material costs can be saved by using adapted heat exchanger cassettes. It should be noted that the "largest" engine variant, for which the exhaust gas recirculation module is basically designed, usually has a rather small share of the sales figures. For the majority of the exhaust gas recirculation modules actually used, a "smaller" heat exchanger cassette may be used which requires less material for heat exchanger plates, exhaust ducts, etc. There is no need for a separate housing cover or closure element to close the heat exchanger housing after the heat exchanger cassette is inserted; For closing the exhaust gas recirculation valve, which is anyway attached to the heat exchanger housing, is used. The flange connection makes it possible to connect the valve housing in a technically simple and robust manner to the heat exchanger housing, for example by a plurality of fastening screws, clamps, by caulking, by crimping, etc. Due to the sealing flange, the heat exchanger cassette automatically ensures the seal between the heat exchanger housing and the valve housing, so no additional seals are necessary. The plug connection allows a tight connection without further measures between the exhaust gas outlet side of the heat exchanger cassette and the heat exchanger housing.

Furthermore, the invention provides that the sealing flange is provided with a recess through which a coolant from the valve housing to the heat exchanger housing can be passed. This allows an integrated cooling water supply of the exhaust gas recirculation valve and the heat exchanger can be achieved without external hoses or pipes are necessary.

The heat exchanger housing may be made of plastic, an aluminum alloy or steel sheet. Such comparatively inexpensive materials can be used in particular because the heat exchanger housing itself is cooled.

The different heat exchanger cassettes may differ in the area of the heat transfer elements and / or in the type of heat transfer elements used. For example, a heat exchanger cassette for a "smaller" internal combustion engine can use a heat exchanger cassette in which the heat exchanger package is made shorter inside than in a variant for a "large" internal combustion engine. Different heat exchanger capacities can also be achieved by using, if necessary, more complex solutions with better heat transfer coefficients. Thus, one cassette may contain a tube bundle cooler while another cassette contains a plate cooler. The cassettes may also differ in that turbulence liners are provided in one type, while no turbulence liners are used in the other type.

• Figur 1 in einer perspektivischen Explosionsansicht einen Zylinderkopf mit Abgasrückführungsmodul;
• Figur 2 den Zylinderkopf von Figur 1 mit Abgasrückführungsmodul in einer ersten perspektivischen Ansicht;
• Figur 3 in einer perspektivischen Explosionsansicht den Wärmetauscher des in den Figuren 1 und 2 gezeigten Abgasrückführungsmoduls;
• Figur 4 eine perspektivische, teilgeschnittene Ansicht des Wärmetauschers von Figur 3; und
• Figur 5 schematisch ein Abgaswärmetauschergehäuse und ein Ventilgehäuse zusammen mit verschiedenen Wärmetauscherkassetten.

The invention is explained below with reference to various embodiments, which are illustrated in the accompanying drawings. In these show:

• FIG. 1 in a perspective exploded view of a cylinder head with exhaust gas recirculation module;
• FIG. 2 the cylinder head of FIG. 1 with exhaust gas recirculation module in a first perspective view;
• FIG. 3 in a perspective exploded view of the heat exchanger in the Figures 1 and 2 shown exhaust gas recirculation module;
• FIG. 4 a perspective, partially sectioned view of the heat exchanger of FIG. 3 ; and
• FIG. 5 schematically an exhaust heat exchanger housing and a valve housing together with various heat exchanger cassettes.

Based on Figures 1 and 2 will now be explained the basic structure of an exhaust gas recirculation module, as embodied in the context of the present invention.

It can be seen a cylinder head 10, which serves in a conventional manner to supply intake air to a plurality of cylinders of an internal combustion engine and to remove combustion gases from the cylinders. The intake air is provided via an intake system 12, and the combustion gases are exhausted via an exhaust manifold 14.

In certain operating conditions, a part of the exhaust gas can be taken from the exhaust line of the internal combustion engine and returned to the intake side. For this purpose, two different flow paths are possible.

A first flow path passes through a heat exchanger 16, in which heat can be withdrawn from the exhaust gas. For this purpose, a coolant inlet 18 and a coolant outlet 20 are provided. In order to control or regulate the volume flow through the heat exchanger 16, an exhaust gas recirculation valve 22 is provided.

A second flow path extends through a bypass channel 24, through which exhaust gas can be passed directly from the exhaust gas to the suction side, bypassing the heat exchanger 16. The bypass channel 24 is associated with a bypass valve 26, with which the volume flow through the bypass channel can be controlled or regulated.

The heat exchanger 16 has a heat exchanger housing 50, which may consist of plastic, an aluminum alloy or steel sheet.

The heat exchanger housing 50 is provided with a mounting flange 52 which surrounds an access opening to the interior of the heat exchanger housing 50.

On the mounting flange 52 of the heat exchanger housing 50, a valve housing 60 of the exhaust gas recirculation valve 22 is mounted. The valve housing 60 is also provided with a mounting flange, here designated by the reference numeral 62 is. To connect the two mounting flanges 52, 62 together, mounting screws 64 may be used.

As an alternative to the screw solution, the interface can also be crimped or crimped with brackets or, in the case of a heat exchanger housing which consists of sheet metal.

The valve housing 60 of the exhaust gas recirculation valve 22 is provided with an internal cooling passage 66 through which a coolant flowing from the coolant inlet 18 through the valve housing 60 of the exhaust gas recirculation valve 22 and then through the heat exchanger housing 50 to the coolant outlet 20. The transfer of the coolant from the cooling channel 66 in the interior of the valve housing 60 of the exhaust gas recirculation valve 22 to the heat exchanger housing 50 is effected by a plug connection 68 which is integrated into the connection surfaces of the mounting flanges 52, 62.

In the interior of the heat exchanger housing 50, a heat exchanger cassette 70 is arranged, the function of which is to ensure a reliable seal between the exhaust gas flowing through the heat exchanger 16 and the coolant also flowing through the heat exchanger 16 and, on the other hand, to allow good heat transfer from the exhaust gas to the coolant , For this purpose, a plurality of heat transfer elements 72 are arranged inside the heat exchanger cassette 70, which consist of a good heat-conducting and corrosion-resistant material, usually stainless steel.

The heat exchanger cassette 70 is provided with a sealing flange 74 which is clamped between the two mounting flanges 52, 62. The sealing flange 74 may be associated with different seals, for example here a circumferential elastomeric seal 76 on the side of the heat exchanger housing 50 and a gasket 78 on the side of the valve housing 60th

On the side facing away from the sealing flange 74, the heat exchanger cassette 70 is provided with a plug connection 80 which engages in a plug-in receptacle 82 when the heat exchanger cassette 70 is mounted inside the heat exchanger housing 50.

The volume flow of exhaust gas to be passed through the heat exchanger 16 enters the valve housing 60 via an inlet 84, to which a valve seat 86 and a valve element 88 of the exhaust gas recirculation valve 22 are connected. Depending on the position of the exhaust gas recirculation valve 22, a more or less large flow cross section for the recirculated exhaust gas is released.

When a flow area is released, the exhaust gas flows in the direction of the arrow P through the valve seat 86 and enters the heat exchange cassette 70. There it can deliver a portion of the entrained heat via the heat transfer elements 72 to the coolant and finally pass via the plug connection 80 to a port 90, from which it is supplied to the intake system.

In FIG. 5a schematically the heat exchanger housing 50 and the valve housing 60 of the exhaust gas recirculation valve 22 are shown. Further, it can be seen that there is an access opening Z to the interior of the heat exchanger housing 50 when the valve housing 60 is not yet secured to the mounting flange 62 of the heat exchanger housing 50.

In the heat exchanger housing 50 different heat exchanger cassettes can be used, which in the Figures 5b, 5c and 5d are indicated schematically. In this way, a modular system is created, which makes it possible to use 60 different heat exchanger cassettes 70 between the same heat exchanger housing 50 and the same valve housing. As a result, with little effort, the exhaust gas recirculation module and in particular the heat exchanger 16 can be adapted to different volume flows of exhaust gas to be recirculated and to different required heat transfer capacities.

The difference between those in the FIGS. 5b and 5c shown heat exchanger cassettes, is that different heat transfer elements 72 are used. These may differ in terms of their geometric design, their material, their packing density, their area and / or other parameters.

In FIG. 5d a heat exchanger cassette 70 is shown, which in terms of their length of the in the FIGS. 5b and 5c shown heat exchanger cassettes 70 different. The cartridge according to 5d is suitable for "smaller" engines in which a lower volume flow of exhaust gas must be recycled. Accordingly, a smaller amount of heat within the heat exchanger 16 must be removed. It can be seen that the distance to the plug-in receptacle 82 of the heat exchanger housing 50 at the in FIG. 5d shown heat exchanger cassette 70 can be bridged with little effort, that the connector 80 is made longer.

Claims (7)

1. An exhaust-gas recirculation module for an internal combustion engine, especially of a motor vehicle, with an exhaust-gas recirculation valve (22) with which a volumetric flow of exhaust which is to be recirculated can be determined, and with a heat exchanger (16) in which the exhaust which is to be recirculated can be cooled, wherein the heat exchanger (16) has a replaceable heat-exchanger cassette (70) and the heat exchanger has a heat-exchanger housing (50) which has an access opening (Z) which is closed by a valve housing (60) of the exhaust-gas recirculation valve (22), wherein the heat-exchanger cassette (70) is inserted into the heat-exchanger housing (50) through the access opening (Z), wherein the valve housing (60) is connected to the heat-exchanger housing (50) by a flange connection (52, 62) or is cramped, caulked or crimped thereto, characterised in that the heat-exchanger cassette (70) is provided with a sealing flange (74) which is clamped between the heat-exchanger housing (50) and the valve housing (60), and in that the heat-exchanger cassette (70) is provided with a plug-in connection (80) on the downstream exhaust side,
   wherein the sealing flange (74) is provided with a cutout (68) through which a coolant can be passed from the valve housing (60) to the heat-exchanger housing (50).
2. An exhaust-gas recirculation module according to one of the preceding claims, characterised in that the heat-exchanger housing (50) comprises plastics material, an aluminium alloy or steel sheet.
3. A modular system for a heat exchanger of an exhaust-gas recirculation module for internal combustion engines according to one of the preceding claims, with a heat-exchanger housing (50), a valve housing (60) and a plurality of heat-exchanger cassettes (70) which differ with regard to their heat-exchange capacity, wherein that heat-exchanger cassette (70) which is adapted to the heat-exchanger requirement of the respective internal combustion engine is installed in the heat-exchanger housing.
4. A modular system according to Claim 3, characterised in that the different heat-exchanger cassettes (70) differ with regard to the surface area of the heat transfer elements (72).
5. A modular system according to Claim 3 or Claim 4, characterised in that the different heat-exchanger cassettes (70) differ with regard to the type of heat transfer elements (72) used.
6. A modular system according to Claim 5, characterised in that one type of heat transfer elements (72) contains tubes, whereas another type contains plates.
7. A modular system according to Claim 5 or Claim 6, characterised in that one type of heat transfer elements (72) contains turbulence inserts.

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