WO2008049797A2

WO2008049797A2 - Cooling system for the demand-dependent cooling of an internal combustion engine

Info

Publication number: WO2008049797A2
Application number: PCT/EP2007/061259
Authority: WO
Inventors: Michael Hirschler
Original assignee: Avl List Gmbh
Priority date: 2006-10-25
Filing date: 2007-10-22
Publication date: 2008-05-02
Also published as: WO2008049797A3; DE112007002482A5

Abstract

The invention relates to a cooling system (1) for the demand-dependent cooling of an internal combustion engine (2). In order to reduce fuel consumption, it is provided that the internal combustion engine (2) can be connected to at least one ceramic heat store element (3) by means of at least one first heat conductor (4), wherein a thermal first switchgear (5) is arranged in the thermal first heat conductor.

Description

COOLING SYSTEM FOR REQUIRED COOLING OF AN INTERNAL COMBUSTION ENGINE

The invention relates to a cooling system for demand-dependent cooling of an internal combustion engine. Furthermore, the invention relates to a method for demand-dependent cooling of an internal combustion engine. Furthermore, the invention relates to a preheating device for a flowing medium, in particular fuel, with a PTC radiator.

It is known that there is a high potential in the demand-controlled engine cooling for reducing the fuel consumption by rapid heating of the internal combustion engine. To exploit this potential is in the journal MTZ 3/2005, Volume 66, pages 184 to 191 in the article "Demand-dependent controlled engine cooling", Gerald Eifler et al. proposed a cooling system with liquid cooling and an electrically driven water pump and a liquid cooler, wherein for a quick heating of the engine, the engine cooling can be switched off completely with the engine running. To detect the engine temperature, temperature sensors were used in the area of the cylinder head gasket. The disadvantage, however, is that only the circulation of water can be stopped, but the system itself has a high thermal inertia.

However, a significant reduction in fuel consumption can only be achieved if the cooling circuit is completely switched off and the thermal inertia can be minimized.

In diesel fuels precipitate at ambient temperatures below 0 ⁰ C paraphines, which makes the fuel viscous and can only pass through the filter bad. Due to increasing demands on the filter units in modern common rail injectors precise diesel fuel preheating is required especially in the commercial vehicle sector.

Such Kraftstoffvorwärmeinrichtungen were previously built by monolithic (homogeneously pressed ceramic) ceramic plates of PTC (PTC thermistor) - ceramic, which were stretched in varying numbers in a metallic frame, usually an extruded aluminum profile. They are electrically and mechanically contacted by springs, so that they begin to heat by applying voltage, the platelets are designed so that they have the largest possible surface in relation to their volume, so as much heat to the metal frame and with it to the flowing through and fuel to be heated can be coupled. On the one hand, this structure requires a correspondingly large number of ceramic platelets, which are very thin and fragile, and, on the other hand, correspondingly elaborate building frames in which these particles can be clamped, so that reliable electrical contacting is provided with adequate installation effort. Since the PTC elements can not be made arbitrarily thin (a breakage may cause a short circuit in the fuel), they represent an increased resistance to fuel flow in the aluminum profile. A fuel preheating device of this kind is known for example from JP 59-218355 A2.

The object of the invention is to substantially reduce fuel consumption by improving the cooling system. Another object of the invention is to reduce the flow resistance in the preheating of a flowing medium, such as fuel.

According to the invention this is achieved in that the internal combustion engine is connectable to at least one ceramic heat storage element via at least one first heat conductor, wherein preferably in the first heat conductor, a thermal first switching device is arranged.

It when the ceramic heat storage element is thermally connectable to a heat exchanger, wherein preferably in a second heat conductor between the ceramic heat storage element and the heat exchanger, a thermal second switching device is arranged is particularly advantageous.

By using ceramic as a storage medium for thermal energy, this can be performed via metallic heat conductors from the internal combustion engine, wherein the heat storage element via the switching means of the internal combustion engine and the heat exchanger can be separated, so that the connection and disconnection takes effect without delay.

Since ceramic has a high thermal energy storage capacity in terms of volume, it can also be isolated from the environment much better than conventional storage elements.

If both the connections to the engine, as well as the heat exchanger separated, the engine heat can be stored for a long time and the internal combustion engine can be heated up quickly.

In a further embodiment of the invention can be provided that the ceramic heat storage element contains pyroelectric ceramic or PTC ceramic. When using PTC ceramic, the internal combustion engine by electrical Energy to be heated, when using pyroelectric ceramic can be recovered from the heat storage electrical energy.

Ceramic stores much more heat per unit volume than water, but its low thermal conductivity is usually not a suitable medium for quickly adding or removing heat. This changes, however, when the ceramic is no longer heated as a monolithic block, but in many thin layers, in which the heat is introduced by metallic spacers. Such multilayer structures of alternating metallic and ceramic layers are already used commercially for the storage of electrical energy for ceramic capacitors.

The structure of a ceramic heat storage element is realized by multilayer technology, as used, inter alia, for the production of ceramic capacitors. It is preferably provided that the ceramic heat storage element are constructed from a sequence of ceramic and metallic and / or metal-containing layers, wherein a first group of metallic and metal-containing layers are connected to each other by a first Sammelther-, which thermally connected to the first heat conductor is. A simple connection to a heat exchanger is possible if a second group of metallic and metal-containing layers are connected to each other by a second Sammelthermode, which is thermally connected to the second heat conductor. The term "thermode" is used in this context for the thermal connection of the heat storage element.

In order to reduce the flow resistance in the preheating of a flowing medium, it is provided that the PTC radiator has a ceramic multilayer heating element, wherein preferably the ceramic multilayer heating element is composed of a sequence of ceramic and metallic and / or metal-containing layers.

In a particularly advantageous embodiment of the invention it is provided that a first group of metallic or metal-containing layers is connected to a first electrode and a second group of metallic or metal-containing layers to a second electrode, wherein between each of a metallic or metal-containing layer of the first group and a metallic or metal-containing layer of the second group, a ceramic layer is disposed, wherein preferably the metallic or metal-containing layers of the first or second group are at different electrical potentials. In this case, the heat of the ceramic multilayer heating element via at least one metallic or metal-containing part, preferably via at least one metallic or metal-containing layer, are derived.

A significant reduction of the flow resistance can be achieved if the PTC radiator is connected via a heat conductor with a protruding into the flowing medium, preferably formed by a metal profile heating register, preferably arranged in the heat conductor between the PTC radiator and the heating coil, a thermal switch is and when at least one PTC radiator is arranged directly in contact with a formed by a metal profile heating coil. The heating register itself may have a streamlined shape. In this case, it is advantageous for achieving a low flow resistance if the heating register consists of a plurality of parallel heating plates, which are preferably connected to one another in a heat-conducting manner via at least one distributor plate. The plates of the heating register are arranged substantially parallel to the flow direction.

The invention will be explained in more detail below with reference to FIGS. Show it :

1 is a schematic diagram of a cooling system according to the invention with a ceramic heat storage element in a first embodiment;

2 shows the circuit of a ceramic heat storage element in a second embodiment;

3 shows the circuit of a ceramic heat storage element in a third embodiment;

4 shows a preheating device according to the invention in a first embodiment;

Fig. 5 shows an alternative embodiment of a heating register; and

Fig. 6 is a preheating device according to the invention in a further embodiment.

1 shows a cooling system 1 for an internal combustion engine 2. The cooling system 1 has a ceramic heat storage element 3, which is thermally connected via a metallic heat conductor 4 to the internal combustion engine 2. In the first heat conductor 4, a first switching device 5 is arranged, via which the ceramic heat storage element 3 can be switched on or off. The ceramic heat storage element consists in the embodiment of pyroelectric ceramic, whereby a usable voltage source 6 is formed. With U the tapped voltage is designated. The ceramic heat storage Element 3 is further connected via a metallic second heat conductor 7, in which a second switching device 8 is arranged, with a heat exchanger 9. Via the second switching device 8, the ceramic cooling device 8 can be selectively connected to the heat exchanger 9 or switched off. In the exemplary embodiment illustrated in FIG. 1, the ceramic heat storage element has two collecting thermodes 3a, 3b, which are each connected to a group A, B of thin metal-containing layers of the heat storage element 3. The heat storage element 3 consists of many thin ceramic layers 11, in which the heat is introduced through metallic layers 10a, 10b. The metallic layers 10a, 10b are metallically connected directly to the first and second heat conductors 4, 7, respectively.

By the switching devices 5, 8, the ceramic heat storage element 3 can be switched as an electrical line. So it is possible to heat the engine without having to miterwärmen a cooling medium immediately. On the other hand, it is also possible to heat the ceramic heat storage element 3 faster by the connection with the heat exchanger 9 is interrupted. If both first and second switching devices 5, 8 are separated, and if the ceramic heat storage element 3 is well insulated, the heat can be stored for a relatively long time, for example overnight, and used to heat the internal combustion engine before the next start. Since the heat is very evenly distributed by the metallic layers 10a, 10b, no water pump is necessary.

Additional benefit can be achieved by the type of ceramic used:

With PTC ceramic, as used for example for heater in air and diesel heaters, the ceramic heat storage element can be heated by applying an external voltage U to operating temperature. When using pyroelectric ceramics, the waste heat is converted to 5% to 10% into electrical energy, which can be fed into the battery. In this case, layers of metallic layers 10a, 10b are connected to each other with the same electrical potential.

The construction of ceramic multilayer components can be carried out by producing films made of ceramic, to which the metallic or metal-containing layers are applied by screen printing or another method (eg offset printing). Alternatively, both ceramic and metal-containing layers can be applied alternately by screen printing. For this structure, a direct use of metal foils is possible. The films are then pressed, the individual components punched or sawn, the Ceramic sintered and the inner electrodes forming metallic layers connected to an outer electrode.

In the embodiment of a ceramic heat storage element 3 shown in FIG. 2, the metallic layers 10a are combined to form a single thermode 3a. The supply and discharge of heat in this case takes place via the same thermode 3 a, which is connected both to the first metallic heat conductor 4 and to the second metallic heat conductor 7, which is connected to the internal combustion engine 2 or the heat exchanger 9 via switching devices (not shown) to lead.

Fig. 3 shows a further embodiment of the invention, wherein the ceramic heat storage element 3 has two thermodes 3a, 3b. The first thermode 3a is connected to the first metallic heat conductor 4, the second thermode 3b is in direct contact with the heat exchanger. 9

By using metallic heat conductors and the ceramic heat storage element 3, water can be omitted as an intermediate storage medium in the cooling circuit.

The preheating device 101 consists of a PCT heating element 102, which has a ceramic multilayer heating element 103. The PTC radiator 102 is connected in the embodiment shown in Fig. 4 via a heat conductor 104 with a heating coil 105 which is arranged projecting in a medium flow 106. 107, the cross section of a flow path, for example, a fuel line is indicated.

In the heat conductor 104 between the PTC heating element 102 and the heating coil 105, a thermal switch 108 is arranged, via which the heat supply to the heating coil can be switched on or off.

The ceramic multilayer heating element 103 has two groups A, B of metallic or metal-containing layers 109, 110, which are arranged alternately parallel to one another, wherein between each two metallic or metal-containing layers 109, 110 a ceramic layer 111 is arranged. Each of the groups A, B of metallic or metal-containing layers 109, 110 can be acted upon by an electrode 112, 113 with different electrical potential. Reference numeral 114 indicates a voltage source.

The plates 105a of the heating profile 105 formed by a metal profile are arranged parallel to each other in the flow medium 106 in a streamlined manner in order to minimize the flow losses. Fig. 5 shows an embodiment of a heating register 105 with mutually parallel metallic heating plates 105a, which are interconnected by a metallic manifold 105b.

FIG. 6 shows a further embodiment variant of a preheating device 101, in which the PTC heating elements 102 are in direct contact with a heating register 105, which projects into a medium flow 106 of a flow path 107 of rectangular cross-section.

It is essential that only the heating coil 105 formed by a metal profile must remain in the medium flow 106, if so much heat is developed by the PTC heating element 102 that a metallic connection can supply sufficient heat. As a result, the flow resistance of the medium is reduced. Due to the omission of a spring construction for connecting the PTC radiator 102 to the heating register 105, there is no risk of a short circuit due to broken PTC plates. To realize this, the PTC radiator 105 is no longer formed by a monolithic, ie internally homogeneous component, but in multilayer technology (as used for example for the production of ceramic capacitors) is constructed. The internal structure thus consists alternately of ceramic and metallic or metal-containing layers 111, 109, 110. The thickness of these layers 111, 109, 110 can be between a few μm and up to 102 mm. As a ceramic layer 111, a PTC material, as has already been used in previous solutions, can be used. As metal all metallic materials as they are used in known Vielschichtkonden- sators are suitable. In any case, the different electrodes 112, 113 are set to different electrical potentials, so that a voltage is applied to the ceramic layer 111 lying therebetween, which leads to a current flow and thus to a heating of this ceramic layer 111.

The metallic or metal-containing layers 109, 110 are also used to dissipate the thermal energy, for which purpose either the metallic layers 109, 110 of the electrically contacting electrodes 112, 113 or separate metallic or metal-containing layers can be used. It is also important here that in this case only those layers which are at the same electrical potential are connected to one another in an electrically conductive manner, that is to say normally the heat-dissipating electrode with ground potential. As a result, the heat dissipating surface can be increased by a multiple, more conventional ceramic plates can be replaced by a multilayer heating element 103, which is also no longer as thin as in previous preheating and thus essential designed to be less sensitive. The dissipation of heat takes place through the heating coil 105, which by a metallic Frame is formed and which is arranged in the medium flow. Due to the omission of the spring terminals for the components, the preheating device 101 according to the invention is much easier to design and manufacture.

The construction of ceramic multilayer components is nowadays usually carried out by producing films made of ceramic, to which the metallic or metal-containing layers are then applied by screen printing or another method (for example offset printing). Alternatively, both ceramic and metal-containing layers can be applied alternately by screen printing. The foils are then pressed, the individual components punched out or sawed, the ceramic sintered and the inner electrodes of the same design connected to an outer electrode.

The fuel preheating device according to the invention is suitable for flowing, liquid and gaseous media, and can be used particularly advantageously for heating fuel.

Claims

1. Cooling system (1) for demand-dependent cooling of an internal combustion engine (2), characterized in that the internal combustion engine (2) with at least one ceramic heat storage element (3) via at least one first heat conductor (4) is connectable.

2. Cooling system (1) according to claim 1, characterized in that in the first heat conductor, a thermal first switching device (5) is arranged.

3. Cooling system (1) according to claim 1 or 2, characterized in that the ceramic heat storage element (3) with a heat exchanger (9) is thermally connectable.

4. Cooling system (1) according to one of claims 1 to 3, characterized in that in a second heat conductor (7) between the ceramic heat storage element (3) and the heat exchanger (9), a thermal second switching device (5) is arranged.

5. Cooling system (1) according to one of claims 1 to 4, characterized in that the ceramic heat storage element (3) contains pyroelectric ceramic and is designed as an electrical energy source.

6. Cooling system (1) according to one of claims 1 to 5, characterized in that the heat storage element (3) contains PTC ceramic and can be heated by applying an electrical voltage (U).

7. Cooling system (1) according to one of claims 1 to 6, characterized in that the ceramic heat storage element (3) from a sequence of ceramic (11) and metallic and / or metal-containing layers (10a, 10b) are constructed.

8. Cooling system (1) according to claim 7, characterized in that a first group (A) of metallic and metal-containing layers (10a) by a first Sammelthermode (3a) are interconnected, which is thermally connected to the first heat conductor (4) ,

9. Cooling system (1) according to claim 7 or 8, characterized in that a second group (B) of metallic and metal-containing layers (10b) by a second Sammelthermode (3b) are interconnected, which with the second heat conductor (7) thermally connected is.

10. A method for demand-dependent cooling of an internal combustion engine (2) with a cooling system (1) according to one of claims 1 to 9, characterized in that the internal combustion engine (2) via a thermal first switching device (5) with at least one ceramic heat storage element (3) optionally thermally connected or thermally separated from it.

11. The method according to claim 10, characterized in that the ceramic heat storage element (3) is selectively connected via a thermal second switching device (8) with a heat exchanger (9) or separated from it.

12. preheating device (101) for a flowing medium, in particular fuel, with a PTC radiator (102), characterized in that the PTC radiator (102) comprises a ceramic multilayer heating element (103).

13. preheating device (101) according to claim 12, characterized in that the ceramic multilayer heating element (103) from a sequence of ceramic and metallic and / or metal-containing layers (111, 109, 110) is constructed.

14. preheating device (101) according to claim 13, characterized in that a first group (A) of metallic or metal-containing layers (109) having a first electrode (112) and a second group (B) of metallic or metal-containing layers (110). is connected to a second electrode (113), wherein between each of a metallic or metal-containing layer (109) of the first group (A) and a metallic or metal-containing layer (110) of the second group (B) a ceramic layer (111) is arranged ,

15. preheating device (101) according to claim 13 or 14, characterized in that the metallic or metal-containing layers (109, 110) of the first and second group (A, B) are at different electrical potentials.

16. preheating device (101) according to any one of claims 13 to 15, characterized in that via at least one metallic or metal-containing part, preferably via at least one metallic or metal-containing layer (109, 110), heat from the multilayer heating element (103) is derivable.

17 preheating device (101) according to one of claims 12 to 16, characterized in that the PTC heating element (102) via a heat conductor (104) with a projecting into the flowing medium, preferably formed by a metal profile heating coil (105) is connected , wherein particularly preferably in the heat conductor (104) between the PTC radiator (102) and the heating coil (105), a thermal switch is arranged.

18. preheating device (101) according to any one of claims 12 to 17, characterized in that at least one PTC heating element (102) is arranged directly in contact with a preferably formed by a metal profile heating register (105).

19. preheating device (101) according to any one of claims 12 to 18, characterized in that the multilayer element (103) outside the medium stream (106) is arranged.

20. preheating device (101) according to any one of claims 12 to 19, characterized in that the heating register (105) consists of a plurality of parallel heating plates (105a), which are preferably connected via at least one distributor (105b) heat-conducting together.