WO2008017365A1

WO2008017365A1 - Heat exchanger for a motor vehicle

Info

Publication number: WO2008017365A1
Application number: PCT/EP2007/006328
Authority: WO
Inventors: Thomas Holzbaur; Eike Willers; Thomas Heckenberger
Original assignee: Behr Gmbh & Co. Kg; Behr Thermot-Tronik Gmbh
Priority date: 2006-08-10
Filing date: 2007-07-17
Publication date: 2008-02-14
Also published as: DE102006037640B4; DE102006037640A1

Abstract

The invention relates to a heat exchanger for a motor vehicle, comprising an inlet region (14) for supplying and an outlet region (6) for discharging an exhaust gas flow of a heat source, an exchanger region (1) through which the exhaust gas can flow, wherein a coolant can flow around at least one exchanger duct of the exchanger region and, for heat exchange, the exhaust gas flow can flow through said at least one exchanger duct of the exchanger region, a bypass duct (2), wherein the exhaust gas in the bypass duct is in considerably reduced heat exchange with the coolant than the exchanger duct, and an actuating element (5), which is arranged in one of both the inlet region (14) or outlet region (6), for distributing the exhaust gas flow between the bypass duct (2) and the exchanger region (1), wherein the actuating element (5) can be adjusted by means of a thermostat (8) which is in thermal contact with the coolant and has a movable actuating element (9).

Description

Heat exchanger for a motor vehicle

The present invention relates to a heat exchanger for a motor vehicle according to the preamble of claim 1.

DE 102 03 003 A1 describes an exhaust gas heat exchanger for cooling an exhaust gas flow recirculated to an internal combustion engine. The heat exchanger comprises a bundle of exchanger tubes and a bypass channel, in which a comparison with the exchanger channels significantly reduced heat exchange with a heat exchanger flowing through the coolant. By means of an input side rotatably mounted Stellkiappe the Abgasström can be distributed to exchanger tubes and bypass channel. The adjustment of the butterfly valve by means of a vacuum box, the vacuum box is controlled via valves and control electronics in response to sensory control data. Such control of the valve is expensive, prone to failure and costly.

It is the object of the invention to provide a heat exchanger for a motor vehicle, in which the distribution of an exhaust gas flow to exchanger channels and a bypass channel takes place in a reliable and simple manner. This object is achieved according to the invention for a heat exchanger mentioned above with the characterizing features of claim 1. By using a thermostat for adjusting the actuating element as a function of a temperature of the coolant, a cost-effective and reliable component is used, wherein basically a change in the heat exchanger performance by means of an actuating element as a function of the coolant temperature is realized largely independent of control electronics. In addition to low costs, a high degree of operational reliability is thus given.

In a preferred embodiment of the invention, the exhaust gas flow at a high temperature of the coolant through the actuator is primarily passed through the bypass channel and passed at a low temperature primarily through the exchanger area. In such a designed heat exchanger, the heat energy of the exhaust gas flow is used to heat the coolant. Possible applications for this are a coupling of the exhaust gas flow to an interior heating of the vehicle, a faster startup of the vehicle drive from a cold state to operating temperature and the like. Applications of exhaust gas recirculation of internal combustion engines are regularly not provided in this preferred embodiment, since the diversion of the exhaust stream to the bypass channel primarily at low coolant temperatures (cold start) and a diversion via the exchanger channels with warm coolant (exhaust gas recirculation only at operating temperature).

Generally, the heat source may be a fuel cell, in particular a solid oxide fuel cell (SOFC). In this type of energy suppliers for vehicle drives occur hot exhaust gas streams, which are previously discharged substantially unused. By means of the heat exchanger according to the invention, a connection of the waste heat, for example of an SOFC, to a coolant circuit, for example the coolant circuit of a vehicle heater, is made possible in a simple and reliable manner. Alternatively or additionally, the heat source may also be an internal combustion engine of a vehicle. Particularly advantageously, the coolant is then the coolant of a main cooling circuit of the internal combustion engine. In principle, the term "heat source" in the sense of the invention means any suitable heat source located in a vehicle if there is a need for heat coupling between the heat source and a particularly liquid coolant of the vehicle.

In a preferred embodiment, the exhaust gas stream is not returned to the engine after leaving the outlet region. In such use of the heat exchanger, the efficiency consists primarily in a heating of the coolant and not a cooling of the exhaust ses, so that in terms of reliability simplified and possibly more cost-effective designs can be used. In comparison, in the case of heat exchangers for exhaust gas recirculation, the risk of coolant entering the exhaust gas flow must be avoided under all circumstances, because this regularly causes the immediate destruction of the internal combustion engine. In particular with regard to the sealing of moving parts and other interfaces between the exhaust gas flow and the coolant area, greater freedom of design is thus possible in the case of non-recirculation of the exhaust gas.

Generally, the exchanger channel and the bypass channel are preferably arranged in a common housing. This allows a total of compact and inexpensive construction of the heat exchanger. Particularly preferably, the heat exchanger is basically constructed according to the concept of document DE 102 03 003 A1. This basic concept relates to the construction of bypass duct and exchanger tubes as juxtaposed elements, which are integrated in a common housing through which coolant flows, and the rotatably mounted control flap arranged on an input side of the housing. Regarding the nature and function of the drive of the butterfly valve, the present invention differs from the named document.

In an advantageous embodiment, the thermostat is arranged on a housing of the heat exchanger, wherein the actuator of the thermostat is guided in an outdoor area and is mechanically connected from the outside via a passage with the control element. In this way, a indirect transition of a movable part of the coolant area in the exhaust area avoided. In particular, when using the heat exchanger in the course of exhaust gas recirculation to an internal combustion engine so the risk of water ingress into the intake of the engine is significantly reduced in a simple manner.

In the sense of a rapid response of the heat exchanger to changed temperatures, parts of the thermostat flow around the coolant in a generally advantageous manner. In a preferred embodiment, the movement of the actuator of the thermostat is thereby transferred by means of an elastic, in particular metallic membrane coolant-tight. Such a membrane, the z. B. may also be formed as a corrugated or bellows, performs essentially the same function as a slide-sealed in a bushing rod, the reliability of the seal in particular between see coolant area and exhaust area is improved.

In a further preferred embodiment, a flow of the coolant through the exchanger area is adjustable by a temperature-dependent movement of the actuator of the thermostat. Particularly advantageously, the actuator comprises a linearly movable valve spool, wherein a passage cross-section for the coolant in dependence on a position of the valve spool is variable. Thus, the existing in the heat exchanger coolant volume can be heated depending on the operating conditions without recirculation, which is a heat storage. For example, the coolant may be part of a vehicle heater, which can provide an increased amount of heat available by the heat reservoir thus created in case of sudden request of heating power. The control of the coolant flow and the adjustment of the adjusting element can be carried out with delay depending on the requirements with respect to a movement of the actuator. The order of operation depending on the temperature profile of the coolant can depend on the particular requirements. In general, such delayed actuation can be easily accomplished by a two-stage piston of the actuator, a delayed-action driver, or other known mechanical solutions. Alternatively or additionally, the flow of the coolant be adjustable by the exchanger area by means of a barrier independently controllable by the thermostat, in particular by means of a second thermostat. With mostly increased structural complexity, such a solution offers greater flexibility in the separate control of exhaust gas flow and coolant flow.

In an inexpensive and reliable embodiment, the thermostat comprises an expansion element. In this case, a continuously rigid wall is preferably provided between the expansion element and the coolant. In particular expansion elements can be encapsulated at the same time large contact surface for rapid heat exchange in a closed sleeve. In an exemplary embodiment, this sleeve can at the same time constitute a hermetic separation without a sliding seal between the coolant area and the outer area or the exhaust area, ie a sealed housing within the heat exchanger housing through which the coolant flows. In principle, a thermostat in the sense of the invention can also be constructed on the basis of bimetal elements, memory metals or other known realizations of mechanical thermostats. It is advantageously provided that the thermostat comprises an electrical control, wherein a control characteristic of the thermostat by the e- lectric control is variable. Below are u. a. So-called map thermostats to understand in which a conventional, z. B. provided with a wax-expansion element mechanical thermostat has an additional electric heater, by means of the targeted heat in the expansion element can be introduced. As a result, the response point and the control characteristics of the thermostat can be influenced by the additional local, electrically controllable heat source. For example, this allows a particularly early reaction to changed operating conditions of an internal combustion engine, for example rapid release of coolant due to sudden full load operation, to be achieved, whereas the thermal reaction of the coolant would only occur much later.

In a simple and cost-effective design, the actuating element preferably comprises a rotatably mounted adjusting flap. To ensure a reliable function, the adjustment of the actuating element is subjected to force in at least one direction by a spring. In this way, the fact is taken into account in particular that thermostats can, due to their construction, usually apply a greater force in one direction of movement than in the other direction of movement. This is especially true for thermostats with expansion element in which in the expansion direction of the expansion material regularly a greater force is exercised than in the opposite direction, in which the force is limited by an external pressure.

In a simple, space-saving and cost-effective design of a heat exchanger, the at least one exchanger channel and the bypass channel are arranged in a common housing through which the coolant can flow, whereby the bypass channel and the exchanger channel are accommodated at the ends in common head pieces delimiting the housing. For such a construction reference is made by way of example to the already mentioned DE 102 03 003 A1.

Further advantages and features of a heat exchanger according to the invention will become apparent from the embodiments described below and from the dependent claims.

Hereinafter, several preferred embodiments of a heat exchanger according to the invention are described and explained in more detail with reference to the accompanying drawings.

Fig. 1 shows a schematic representation of a first embodiment of a heat exchanger according to the invention. Fig. 2 shows a second embodiment of a heat exchanger with two thermostats.

Fig. 3 shows a third embodiment of a heat exchanger. 4 shows a fourth embodiment of a heat exchanger. Fig. 5 shows a fifth embodiment of a heat exchanger in a plan view from the side. Fig. 6 shows the heat exchanger of Fig. 5 in a plan view from above. Fig. 7 shows a sixth embodiment of a heat exchanger. Fig. 8 shows a seventh embodiment of a heat exchanger.

A heat exchanger according to the invention comprises an exchanger region 1 in which at least one, but regularly a plurality of exchanger channels are arranged for the passage of an exhaust gas flow. A bypass channel 2 is arranged parallel to the exchanger channels, wherein the exhaust gas stream, symbolized in FIG. 1 to FIG. 4 by wide arrows, can flow through both the bypass channel 2 and the exchanger channels 1. At least the exchanger channels 1 are surrounded by a liquid coolant which flows via an inlet 3 into a housing of the heat exchanger and exits the housing via an outlet 4.

An adjusting element 5 is arranged in a presently outlet-side region 6 of the exhaust gas flow and designed as a rotary valve 7 rotatably mounted via a rotary valve. A thermostat 8 is disposed on the housing of the heat exchanger and is in thermal communication with the coolant. An actuator 9 of the thermostat 8 is mechanically connected via a lever 10 to the rotary shaft 7 of the butterfly valve 5 so that a movement of the actuator 9 caused by the thermostat 8 effects an adjustment of the actuator 5. Depending on the position of the actuating element 5, the exhaust gas flow is primarily conducted through the exchanger channels or primarily through the bypass channel 2. In the position shown in FIG. 1, the exhaust gas flow is conducted exclusively through the bypass channel 2. It is understood that the adjusting element 5 can also be arranged in an inlet region of the heat exchanger.

In the present embodiment, heating of the coolant leads to an expansion of an expansion element, not shown, in the thermostat 8, as a result of which the rod-like actuator 9 is pushed out of the thermostat 8. A heating of the coolant thus leads to an adjustment of the control element 5 in the clockwise direction of FIG. 1 and thus to a passage of the exhaust gas flow through the exchanger region 1 and the exchanger channels not shown in detail. At more complete Adjustment of the butterfly valve flows the exhaust stream only through the exchanger channels. In this functionality, the heat exchanger of FIG. 1 z. B. are used as exhaust gas cooler for exhaust gas recirculation of an internal combustion engine. In such exhaust gas coolers, the bypass channel is used, for example, to avoid excessive condensation of the exhaust gas during cold start of the internal combustion engine, with exhaust gas recirculation often only taking place when the engine is hot. By correspondingly reversed mechanical connection of the thermostat 8 to the adjusting element 5, the exhaust gas flow with heated coolant would be directed primarily through the bypass channel. As a result, a heat exchanger is provided, which heats the primarily in the cold state by means of the heat of the exhaust gas stream. Such an arrangement uses a heat source of the vehicle for the targeted heating of a coolant, for example a heating system of the vehicle.

2 shows a second embodiment of a modification of the heat exchanger of FIG. 1, in which a second thermostat 11 is arranged in the region of the coolant outlet 4, through which a gate valve 12 in response to the temperature of the coolant can be actuated. Depending on the position of the second thermostat 11, the coolant flow through the exchanger region 1 can thus be prevented or completely or partially released. The gate valve 12 is provided with a spring 12a. As a result, an overpressure valve in the area of the shut-off is realized at the same time, so that uncontrolled boiling of the coolant or excessive pressure increase is avoided. In the arrangement of two thermostats according to FIG. 2, it is possible in a particularly simple way, the adjustment of the control element 5 and the adjustment of the gate valve 12 with respect to the temperature curve delayed to interpret each other, with an opening sequence can be arbitrary depending on requirements.

In the third embodiment shown in FIG. 3, in contrast to the second embodiment, a gate valve 12 with a spring means 12 a as well as the actuator 5 is connected to only a single thermostat 8. Again, a delayed adjustment of actuator element 5 and gate valve 12 possible, which is shown schematically in Fig. 3 by the shape of the actuator 9 as a double piston.

In the fourth embodiment according to FIG. 4, a spring 5a which prestresses this in one direction is arranged on the adjusting element 5, whereby a secure actuation of the actuating element is ensured in both directions. In this way, the fact is taken into account that, in particular, thermostats with an expansion element can apply a greater force in one direction of actuation than in the other direction of actuation.

Fig. 5 and Fig. 6 show a fifth embodiment, in which the thermostat 8 is arranged in a separate additional housing 13 a laterally on the housing 13 of the heat exchanger, wherein the thermostat 8 is sufficiently flowed around by the coolant. In the case of the fifth embodiment, the adjusting element 5 is arranged in an inlet region 14 of the heat exchanger.

The actuator 9 of the thermostat 8 is slidably guided by a wall of the housing 13 a to the outside, wherein the sliding seal is not in contact with the coolant. For this purpose, an expansion element of the thermostat together with the actuator 9 is accommodated in a sleeve which is fixed on the inside coolant-tight to the thermostat housing 13a. The actuator 9 initially leads into the outer space, wherein the driven via the lever 10 rotary shaft 7 is performed by a wall in the exhaust gas flowed inlet portion 14.

The heat exchanger of Fig. 5 and Fig. 6 is a detailed construction in particular a heat exchanger, which is described in its construction in the document DE 102 03 003 A, wherein instead of a z. B. in Fig. 5a shown pressure cell 65 a according to FIG. 5 and FIG. 6 arranged thermostat 8 is provided. In such a heat exchanger, a plurality of narrow exchanger channels designed as flat tubes and a bypass channel of larger cross-section are welded together in end-side headers. The head pieces take a housing wall between them. tion with connections for the coolant. On one of the head pieces of the Aulassbereich is welded and on the other head piece of the inlet portion with the rotatably mounted flap.

In the sixth embodiment of FIG. 7, in contrast to the embodiment of FIG. 5, the thermostat 8 is a so-called map thermostat. This has an additional electrical heating means 16, which is connected via contact wires with control electronics. By means of the electric heating means 16, an expansion element of the thermostat 8 is influenced in superposition with the temperature of the coolant, so that the regulation characteristic of the thermostat 8 can be selectively changed depending on the operating conditions and requirements.

In the embodiment of FIG. 8, the actuator 9 of the thermostat 8 is provided with a valve spool 17. The coolant flow in this case runs from an inlet 3 on the housing 13 through the exchanger area to a passage 18 from the exchanger area into the housing 13a of the thermostat 8. The coolant outlet 4 of the heat exchanger is likewise arranged on the housing 13a of the thermostat 8, so that the coolant flow the valve spool 17 must pass. Depending on the position of the valve slide 17 relative to a valve seat 19 arranged in the housing 13a, the coolant flow through the heat exchanger is thus regulated. Depending on the requirements, the passage for the coolant can also be completely closed.

It is understood that the special features of the different embodiments can be reasonably combined depending on the requirements.

Claims

Patent claims

1. A heat exchanger for a motor vehicle, comprising an inlet region (14) for supplying and an outlet region (6) for discharging an exhaust gas stream of a heat source, an exchanger region (1) through which the exhaust gas can flow, wherein at least one exchange channel of the exchanger region can be flowed around by a coolant and for the heat exchange can be flowed through by the exhaust gas flow, a bypass channel (2), wherein the exhaust gas in the bypass channel is in a relation to the exchanger passage considerably less heat exchange with the coolant, and in one of the two, inlet region (14) or outlet region (6) , arranged adjusting element (5) for distributing the exhaust gas flow to the bypass channel (2) and the exchanger region (1), characterized in that the adjusting element (5) by a standing with the coolant in thermal contact thermostat (8) with a movable actuator

(9) is adjustable.

2. Heat exchanger according to claim 1, characterized in that the exhaust gas stream at a high temperature of the coolant through the actuating element (5) is primarily in the bypass channel (2) and is conducted at a low temperature primarily in the exchanger area (1).

3. Heat exchanger according to claim 1 or 2, characterized in that the heat source is a fuel cell, in particular a solid oxide fuel cell (SOFC).

4. Heat exchanger according to claim 1 or 2, characterized in that the heat source is an internal combustion engine.

5. Heat exchanger according to claim 4, characterized in that the exhaust gas flow after leaving the outlet region (6) is not returned to the internal combustion engine.

6. Heat exchanger according to one of the preceding claims, characterized in that the exchanger channel (1) and the bypass channel (2) are arranged in a common housing.

7. Heat exchanger according to one of the preceding claims, characterized in that the thermostat (8) is arranged on a housing (13) of the heat exchanger, wherein the actuator (9) of the thermostat out in an outdoor area and from the outside via a passage with the adjusting element (5) is mechanically connected.

8. Heat exchanger according to one of the preceding claims, characterized in that parts of the thermostat (8) are flowed around by the coolant.

9. Heat exchanger according to claim 8, characterized in that the movement of the actuator (9) of the thermostat by means of an elastic, in particular metallic membrane is coolant-tight transmits gene.

10. Heat exchanger according to one of the preceding claims, characterized in that by a temperature-dependent movement of the actuator (9) of the thermostat, a flow of the coolant through the exchanger region (1) is adjustable.

11. Heat exchanger according to claim 10, characterized in that the actuator (9) comprises a linearly movable valve slide (17), wherein a passage cross section for the coolant in dependence on a position of the valve slide (17) is variable.

12. Heat exchanger according to claim 10 or 11, characterized in that the adjustment of the coolant flow and the movement of the adjusting element (5) with respect to a movement of the actuator (9) are delayed relative to each other.

13. Heat exchanger according to one of claims 1 to 9, characterized in that a flow of the coolant through the exchanger area (1) by means of one of the thermostat (8) independently controllable barrier (12), in particular by means of a second thermostat

(11), is adjustable.

14. Heat exchanger according to one of the preceding claims, characterized in that the thermostat (8) comprises an expansion element.

15. Heat exchanger according to claim 14, characterized in that a consistently rigid wall is provided between the expansion element and the coolant.

16. Heat exchanger according to one of the preceding claims, characterized in that the thermostat (8) comprises an electrical control (16), wherein a control characteristic of the thermostat (8) by the electrical control (16) is variable.

17. Heat exchanger according to one of the preceding claims, characterized in that the adjusting element (5) comprises a rotatably mounted adjusting flap.

18. Heat exchanger according to one of the preceding claims, characterized in that the adjustment of the actuating element (5) in at least one direction by a spring (5a) is subjected to force.

19. Heat exchanger according to one of the preceding claims, characterized in that the bypass channel (2) and the at least one exchanger channel in a common, can be flowed through by the coolant housing (13), said bypass channel (2) and exchange channel end in common, the Housing (13) limiting head pieces are added.