Electrothermal converter, brake energy recuperation system, method for manufacturing an electrothermal converter

Abstract

Electrothermal converter (ETC) for converting electrical energy into thermal energy, comprising: - a heat sink (CC) with at least one cooling channel (CC) for passing a cooling medium or at least one heat dissipation surface for transferring heat to a cooling medium that passes by the at least one heat dissipation surface; - an electrical insulating layer formed on a surface (OF1) of the heat sink (KK); - at least one heating conductor (HL) which is formed by thermal spraying on a surface (OF2) of the insulating layer facing away from the heat sink (KK); - at least two connection frames (AR1, AR2) for electrically connecting the at least one heating conductor (HL), which are spatially separated from each other and are electrically and physically connected to the at least one heating conductor (HL), characterized in that - the at least one heating conductor (HL) through thermal spraying and subsequent laser trimming is formed, and contains a chromium-nickel alloy; - where the chromium-nickel alloy contains nickel in a mass fraction of less than 10%.

Description

Technical area:

[0001] The present invention relates to an electrothermal converter and a braking energy recuperation system comprising such an electrothermal converter. Furthermore, the invention relates to a method for producing such an electrothermal converter. State of the art and task of the invention:

[0002] Modern vehicles, especially hybrid electric / electric vehicles, are equipped with a function that allows the vehicles to convert the resulting kinetic braking energy into electrical energy during braking and store it in an on-board electrical energy storage unit for later use. Braking energy recuperation is achieved using a generator, which is located, for example, on a vehicle's drive axle. During braking, this generator converts the resulting kinetic braking energy into electrical energy, thereby decelerating the vehicle.

[0003] If the energy storage device used to store the recuperated braking energy is defective or fully charged, the braking energy can no longer be recuperated in subsequent braking operations.

[0004] This leads to a waste of braking energy or to overheating of the braking systems or (brake) generators of the vehicles.

[0005] The object of the present invention is therefore to provide a possibility with which the braking energy of a vehicle can be recuperated more efficiently.

[0006] A generic electrothermal converter can be found in DE 10 2010 064 596 B3. Description of the invention:

[0007] This problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0008] According to a first aspect of the invention, an electrothermal converter for converting electrical energy into thermal energy is provided.

[0009] The converter comprises a heat sink with at least one cooling channel for passing a cooling medium or at least one heat dissipation surface for dissipating heat to a cooling medium which is guided past the at least one heat dissipation surface.

[0010] The converter further comprises a thermally highly conductive electrical insulating layer formed on a surface of the heat sink and configured to electrically insulate and thermally connect at least one heating conductor, to be described below, from said heat sink. The insulating layer consists, for example, of a thermally highly conductive and simultaneously electrically insulating ceramic.

[0011] The converter further comprises said at least one heating conductor, which is formed on a surface of the insulating layer facing away from the heat sink by thermal spraying and subsequent laser trimming and is configured to convert electrical energy into thermal energy.

[0012] The converter further comprises at least two connection frames for electrically connecting the at least one heating conductor, for example to an electrical energy source, such as to current outputs of a generator, wherein the at least two connection frames are spatially separated from one another and are electrically and physically connected to the at least one heating conductor.

[0013] The invention is based on the idea of ​​converting the electrical energy obtained by recuperation, which cannot be stored in the energy storage device due to a defect or a full charge state of the electrical energy storage device, into thermal energy, which can then be used, for example, to heat the interior of the vehicle, a (traction) battery or a combustion engine of the vehicle.

[0014] To convert the electrical energy obtained through recuperation into thermal energy, an electrothermal converter is required.

[0015] It was also recognized that during vehicle braking, large amounts of kinetic energy (over several hundred kilowatts) and thus large amounts of electrical energy are released in a short period of time, which must be immediately converted into thermal energy and consumed. To quickly convert large amounts of electrical energy into thermal energy, a correspondingly powerful electrothermal converter is required. The converter should be as compact and lightweight as possible to avoid excessive strain on the vehicle's limited space and to keep the vehicle's weight as low as possible.

[0016] Converter systems with wires embedded in sand as heating resistors and a cooling medium that dissipates heat from the wires are bulky and heavy. Furthermore, such systems are too slow to convert the large amounts of kinetic or electrical energy into thermal energy in such a short time.

[0017] Based on these findings, the previously described electrothermal transducer was provided.

[0018] By thermally connecting the heating conductor to the heat sink, or rather to the cooling medium flowing through or past the heat sink, only via a thermally conductive insulating layer, the heat generated by the heating conductor can be quickly dissipated to the cooling medium. Because the heating conductor is manufactured by thermal spraying and subsequent laser trimming, the specific resistance of the heating conductor and thus the efficiency of the electrothermal conversion can be adapted to the requirements of braking energy recuperation.

[0019] This provides a way to recover a vehicle’s braking energy more efficiently.

[0020] Because the heating conductor is formed on the heat sink and the heat sink with a high cooling performance can also be manufactured in a compact design, the above-mentioned converter can be manufactured in a space-saving and weight-saving manner.

[0021] Cooling water, for example, can be used as a cooling medium to dissipate the thermal energy gained from kinetic braking energy. The thermal energy dissipated by the cooling medium can be used to heat the vehicle's interior, a (traction) battery, or a vehicle's combustion engine, for example.

[0022] For example, the at least two lead frames are formed by thermal spraying. The at least two lead frames are formed, for example, by thermal spraying on a surface of the at least one heating conductor facing away from the heat sink.

[0023] For example, the at least one heating conductor has a specific resistance of between 2 and 6 Ω*mm 2 / m, especially between 3 to 5 Ω*mm 2 / m, especially 4 Ω*mm 2 / m, on.

[0024] At least one heating conductor contains a chrome-nickel alloy which has a high specific resistance.

[0025] At least one heating conductor contains a chromium-nickel alloy with nickel in a mass fraction of less than 10%, in particular less than 7%, and especially between 5 and 5.5%. Specifically, at least one heating conductor consists of NiCr20 with nickel in a mass fraction of approximately 5.34%.

[0026] For example, the insulating layer is also formed by thermal spraying.

[0027] The insulating layer contains, for example, a ceramic, electrically insulating material.

[0028] For example, the heat sink is made of a metallic material, in particular aluminum or an aluminum alloy.

[0029] According to a further aspect of the invention, a braking energy recuperation system for a vehicle, in particular a hybrid electric / electric vehicle, is provided.

[0030] The system includes a generator for generating electrical energy from braking energy when the vehicle brakes.

[0031] The system further comprises an electrical energy storage device for storing the electrical energy generated by the generator.

[0032] The system further comprises an electrothermal converter as described above.

[0033] The system further comprises a controllable switching unit having a center terminal, a first switch terminal, and a second switch terminal. The switching unit is electrically connected to the generator via the center terminal. The switching unit is electrically connected to the energy storage device via the first switch terminal. The switching unit is also electrically connected to the converter via the second switch terminal.

[0034] The system further comprises a control arrangement for controlling the switching unit. The control arrangement comprises a detection unit configured to detect the state, in particular the state of charge, of the energy storage device. The control arrangement further comprises a control unit for controlling the switching unit, wherein the control unit is configured to control the switching unit depending on the state of the energy storage device detected by the detection unit such that the switching unit electrically connects the generator or its current outputs selectively to the energy storage device or to the converter.

[0035] For example, the control unit controls the switching unit to electrically connect the generator to the energy storage device if the detection unit detects that the energy storage device is not fully charged (state of charge: Not fully charged) or that the condition, such as the aging state (in English "State of Health (SoH)") of the energy storage device is good. In this case, the energy storage device is charged with electricity from the generator, which the generator generates by converting the kinetic braking energy into electrical energy.

[0036] If, however, the detection unit detects that the energy storage device is fully charged (state of charge: Fully charged) or the condition of the energy storage device is poor, such as aging, the control unit controls, for example, the switching unit such that it electrically connects the generator to the electrothermal converter. In this case, the converter receives current from the generator, which the generator generates by converting the kinetic braking energy into electrical energy. The converter converts this current into heat, which is used by the vehicle, for example, to air condition the vehicle interior.

[0037] According to a third aspect of the invention, a method of manufacturing a transducer as described above is provided.

[0038] According to the method, a heat sink is provided with at least one cooling channel for conducting a cooling medium or with at least one heat dissipation surface for dissipating heat to a cooling medium that is guided past the at least one heat dissipation surface. The heat sink is made, for example, from a metal, in particular aluminum or an aluminum alloy, or a thermally highly conductive ceramic.

[0039] A thermally conductive electrical insulating layer is formed on a surface of the heat sink facing away from the cooling channel or the heat dissipation surface.

[0040] Furthermore, at least one heating conductor is formed on a surface of the insulating layer facing away from the heat sink by thermal spraying and subsequent laser trimming.

[0041] At least two connection frames for electrically connecting the at least one heating conductor are then formed on the at least one heating conductor, wherein the at least two connection frames are spatially separated from one another and are electrically and physically connected to the at least one heating conductor.

[0042] For example, the at least two lead frames are also formed by thermal spraying.

[0043] For example, the at least one heating conductor is formed on the surface of the insulating layer as follows: First, a heat-conducting layer is formed on the surface of the insulating layer using thermal spraying. Then, the electrical resistance is measured at a predetermined section of the heat-conducting layer. While the electrical resistance is being measured, material is removed from the heat-conducting layer using laser trimming. The material is removed until a predetermined electrical resistance is reached for this section.

[0044] Advantageous embodiments of the electrothermal converter described above are, as far as possible, transferable to the above-mentioned braking energy recuperation system or the above-mentioned method, and are also to be regarded as advantageous embodiments of the braking energy recuperation system or the method. Short description of the drawing:

[0045] In the following, exemplary embodiments of the invention are explained in more detail with reference to the accompanying drawings. In the drawings: Fig. 1 shows a schematic representation of a vehicle with a brake energy recuperation system according to an embodiment of the invention; Fig. 2 shows a schematic plan view of an electrothermal converter of the type shown in Fig. 1 shown braking energy recuperation system; and Fig. 3 shows a schematic side view of the electrothermal converter from Fig. 2. Detailed description of the drawing:

[0046] Fig. 1 shows a schematic representation of a vehicle FZ with a brake energy recuperation system according to an embodiment of the invention.

[0047] The brake energy recuperation system according to a generator GN of known type for generating electrical energy during a braking process of the vehicle FZ.

[0048] The brake energy recuperation system according to further comprises an electrical energy storage device ES for storing electrical energy, which in this embodiment is designed as a traction battery for the electrical drive, for example for a stop-start function, of the vehicle FZ.

[0049] The braking energy recuperation system further comprises an electrothermal converter WD for converting electrical energy into thermal energy.

[0050] The braking energy recuperation system further comprises a controllable switching unit US, which comprises a controllable changeover switch with a center terminal MA, a first switching terminal SA1, and a second switching terminal SA2. The switching unit US is electrically connected to the generator GN or its positive-voltage-side power connection via the center terminal MA. The switching unit US is electrically connected to the energy storage device ES or its positive-voltage-side power connection via the first switching terminal SA1. The switching unit US is further electrically connected to the converter WD or its positive-voltage-side power connection via the second switching terminal SA2.

[0051] The braking energy recuperation system further comprises a control arrangement SA for controlling the switching unit US, which comprises a detection unit EE for detecting the aging state and the charge state of the energy storage device ES, as well as a control unit SE for controlling the switching unit US.

[0052] The control unit SE is configured to control the switching unit US depending on the ageing and charge state (in English “State of Charge (SoC)”) of the energy storage device ES recorded by the recording unit EE in such a way that the switching unit US electrically connects the generator GN or its positive voltage side power connection optionally to the energy storage device ES or its positive voltage side power connection or to the converter WD or its positive voltage side power connection.

[0053] If the detection unit EE detects an aging and charge level of the energy storage device ES, which indicate a fault-free and (heavily) discharged state of the energy storage device ES, it sends a signal to the downstream control unit SE, causing it to control the switching unit US in such a way that it electrically connects the generator GN to the energy storage device ES. If the energy storage device ES is electrically connected to the generator GN, it is charged with electricity from the generator GN during a subsequent braking process, which the generator GN generates by converting the kinetic braking energy of the vehicle FZ into electrical energy.

[0054] If, however, the detection unit EE detects a critical aging condition or a fully charged charge level of the energy storage device ES, it sends a signal to the downstream control unit SE, causing it to control the switching unit US in such a way that it electrically connects the generator GN to the converter WD. If the converter WD is electrically connected to the generator GN, the converter WD receives current from the generator GN during the subsequent braking process of the vehicle FZ. The converter WD converts this current into heat, which is used by an air conditioning system KA of the vehicle FZ, which is thermally coupled to the converter WD, for example, to air-condition the interior of the vehicle FZ.

[0055] Fig. 2 and Fig. 3 show in a schematic top view and a schematic side view, respectively, the Fig. 1 shown electrothermal converter WD.

[0056] The converter WD comprises an aluminum heat sink KK with a cooling channel KN for the passage of a cooling medium. The heat sink KK includes an inlet EL for the flow of the cooling medium into the cooling channel KN and an outlet AL for the flow of the cooling medium out of the cooling channel KN. The heat sink and the cooling channel KN are fluidly connected to a heat exchanger of the air conditioning system KA via the inlet and outlet EL, AL.

[0057] The converter WD further comprises an electrical insulating layer formed on a surface OF1 of the heat sink KK facing away from the cooling channel KN. The insulating layer is formed by thermal spraying on the surface OF1 of the heat sink KK.

[0058] The converter WD further comprises a substantially strip-shaped heating conductor HL, which is formed on a surface OF2 of the insulating layer facing away from the heat sink KK and runs parallel to one another.

[0059] The HL heating element consists of a chromium-nickel alloy with nickel in a mass fraction of between 5.2% and 5.5%, particularly between 5.3% and 5.4%, preferably between 5.34% and 5.35%, especially at approximately 5.3425%, and is formed by thermal spraying and subsequent laser trimming. The chromium-nickel alloy has a specific resistance of approximately 4 Ω*mm. 2 / m on.

[0060] The converter WD further comprises two terminal frames AR1, AR2 for electrically connecting the heating conductor HL to the second switching terminal SA2 of the switching unit US or to a ground terminal. The two terminal frames AR1, AR2 are spatially separated from each other on a surface OF3 of the heating conductor HL facing away from the heat sink KK and are electrically and physically connected to the heating conductor HL. The two terminal frames AR1, AR2 are formed by thermal spraying.

[0061] The WD converter is manufactured as follows: First, a heat sink (KK) is made from aluminum, with a channel (KN) for the passage of the cooling medium. The heat sink (KK) can be easily manufactured by die casting or extrusion.

[0062] On a surface OF1 of the heat sink KK facing away from the cooling channel KN, where the heating conductor HL is formed, an insulating layer made of a thermally conductive and electrically insulating ceramic is formed. The insulating layer is formed on the surface OF1 by thermal spraying.

[0063] On a surface OF2 of the insulating layer facing away from the heat sink KK, heating conductors HL are formed from a chromium-nickel alloy with nickel in a mass fraction of between 5.2% and 5.5%, in particular between 5.3% and 5.4%, preferably between 5.34% and 5.35%, especially at approximately 5.3425%. The heating conductors HL are formed by further thermal spraying and subsequent laser trimming.

[0064] The heating conductor HL is designed as follows: First, a heating conductor layer is formed on the surface OF2 of the insulating layer by thermal spraying of the aforementioned chromium-nickel alloy.

[0065] The heating conductor layer is then partially removed by laser trimming in order to achieve a predetermined resistance value for the heating conductor.

[0066] For this purpose, measuring contacts are applied to measure the electrical resistance across the heating conductor layer or across a defined length of the heating conductor layer. While the electrical resistance is measured at the heating conductor layer, the heating conductor layer is partially removed by laser trimming. This creates a surface geometry for the heating conductor layer that achieves the predetermined electrical resistance value for the heating conductor.

[0067] The laser beam for laser trimming is controlled in such a way that the predetermined electrical resistance value can be achieved with a small tolerance of less than 10% of the total resistance value.

[0068] Subsequently, two electrical connection frames AR1, AR2 for electrically connecting the heating conductor HL are formed on a surface OF3 of the heating conductor HL facing away from the heat sink KK.

[0069] The connection frames AR1, AR2 are formed spatially separated from one another at opposite ends of the heating conductor HL by thermal spraying from a metal or a metal alloy, such as copper or a copper alloy.

[0070] To generate electrical resistance in a control circuit, it is advantageous to apply electronic switching elements and discrete components. For this purpose, conductor tracks can be applied in another material such as aluminum, aluminum alloy, copper, or copper alloy. These tracks are also formed by thermal spraying and cover the heating conductor, thus establishing electrical contact with it. This type of construction allows for the implementation of various thermal load circuits on a single heat sink.

[0071] Initial calculations show that with the above-mentioned converter, a heating load of 200 kilowatts with a heating conductor area of ​​less than 1 m2 is feasible.

Claims

[1] Electrothermal converter (WD) for converting electrical energy into thermal energy, comprising: - a heat sink (KK) with at least one cooling channel (KN) for passing a cooling medium or at least one heat dissipation surface for dissipating the heat to a cooling medium which is guided past the at least one heat dissipation surface; - an electrical insulating layer formed on a surface (OF1) of the heat sink (KK); - at least one heating conductor (HL) which is formed by thermal spraying on a surface (OF2) of the insulating layer facing away from the heat sink (KK); - at least two connection frames (AR1, AR2) for electrically connecting the at least one heating conductor (HL), which are spatially separated from each other and are electrically and physically connected to the at least one heating conductor (HL), characterized by , that - at least one heating conductor (HL) is produced by thermal spraying and subsequent laser trimming and contains a chromium-nickel alloy; - where the chromium-nickel alloy contains nickel in a mass fraction of less than 10%. [2] Converter (WD) according to claim 1, wherein the two lead frames (AR1, AR2) are formed by thermal spraying. [3] Converter (WD) according to claim 1 or 2, wherein the at least one heating conductor (HL) has a specific resistance of between 2 and 6 Ω*mm 2 / m. [4] Converter (WD) according to one of the preceding claims, wherein the insulating layer is formed by thermal spraying. [5] Converter (WD) according to one of the preceding claims, wherein the heat sink (KK) is formed from a metallic material. [6] Brake energy recuperation system for a vehicle, comprising: - a generator (GN) for generating electrical energy when the vehicle brakes; - an electrical energy storage device (ES) for storing electrical energy; - a converter (WD) according to one of the preceding claims; - a controllable switching unit (US) which is electrically connected to the generator (GN) via a central connection (MA), to the energy storage device (ES) via a first switching connection (SA1) and to the converter (WD) via a second switching connection (SA2); - a control arrangement (SA) for controlling the switching unit (US), which comprises a detection unit (EE) for detecting the state of the energy storage device (ES) and a control unit (SE) for controlling the switching unit (US), wherein the control unit (SE) is designed to control the switching unit (US) depending on the state of the energy storage device (ES) detected by the detection unit (EE) in such a way that the switching unit (US) electrically connects the generator (GN) optionally to the energy storage device (ES) or to the converter (WD). [7] Method for producing a converter (WD) according to one of claims 1 to 5, comprising steps: - Providing a heat sink (KK) with at least one cooling channel (KN) for passing a cooling medium; - forming an electrical insulating layer on a surface (OF1) of the heat sink (KK); - forming at least one heating conductor (HL) on a surface (OF2) of the insulating layer facing away from the heat sink (KK) by thermal spraying and subsequent laser trimming; - Forming at least two connection frames (AR1, AR2) for electrically connecting the at least one heating conductor (HL), wherein the at least two connection frames (AR1, AR2) are spatially separated from one another and are electrically and physically connected to the at least one heating conductor (HL). [8] The method according to claim 7, wherein the insulating layer and / or the two lead frames (AR1, AR2) are formed by thermal spraying. [9] Method according to claim 7 or 8, wherein for forming the at least one heating conductor (HL) on the surface (OF2) of the insulating layer: - a heating conductor layer is formed by thermal spraying; - the electrical resistance of a predetermined section of the heating conductor layer is recorded; - while the electrical resistance is being measured, material is removed from the heating conductor layer by laser trimming until a predetermined electrical resistance for this section is reached.

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