Method for operating a heating device for a fluid circuit of a motor vehicle and corresponding heating device

Abstract

The invention relates to a method for operating a heating device (9) for a fluid circuit (2) of a motor vehicle (1), wherein the heating device (9) comprises a heating element (10) connected to a first electrical connection (12) and a control unit (11) connected to a second electrical connection (13) for controlling the heating element (10), wherein the control unit (11) establishes a first electrical connection between the first electrical connection (12) and the heating element (10) at least temporarily for heating the fluid circuit (2). It is provided that if a temperature threshold is exceeded, a second electrical connection between the second electrical connection (13) and the control unit (11) is interrupted to switch off the heating element (10). The invention further relates to a heating device (9) for a fluid circuit (2) of a motor vehicle (1).

Description

[0001] The invention relates to a method for operating a heating device for a fluid circuit of a motor vehicle, wherein the heating device comprises a heating element connected to a first electrical connection and a control unit connected to a second electrical connection for controlling the heating element, wherein the control unit establishes at least a temporary first electrical connection between the first electrical connection and the heating element for heating the fluid circuit. The invention further relates to a heating device for a fluid circuit of a motor vehicle.

[0002] For example, the prior art document EP 4 145 575 A1 describes a fuel cell system and a method for controlling a heating device of the same system. The fuel cell system comprises a cathode oxygen depletion heater (COD heater) arranged in a line through which cooling water circulates in a fuel cell stack, heating the cooling water or consuming residual power from the fuel cell stack, and a controller that determines the power input according to a set heating quantity of the COD heater and controls the operation of the COD heater based on the determined power input.

[0003] Furthermore, EP 4 215 411 A1 discloses a thermal management system and an electric vehicle. The thermal management system comprises a compressor, a water-cooled condenser, a battery cooler, a valve body assembly, a first water pump, a second water pump, and a third water pump, arranged in a centralized manner.

[0004] This arrangement allows for a more compact installation of the various components, and the pipe runs between components are as short as possible. This not only helps to reduce the space required by the thermal management system, but can also reduce the pressure drop of the fluid as it circulates along a pipe, as well as improve the cooling or heating efficiency of the thermal management system.

[0005] Furthermore, the thermal management system can separately operate a cooling circuit for the passenger compartment, a heating circuit for the passenger compartment, a cooling circuit for the battery, a heating circuit for the battery, and a cooling circuit for the electric driver, allowing the passenger compartment, the battery, or the electric driver to be cooled or heated. In this way, temperatures at all points within the electric vehicle can be flexibly controlled.

[0006] The object of the invention is to present a method for operating a heating device for a fluid circuit of a motor vehicle which has advantages over known methods, in particular reliably and with little effort prevents excessive heating of a fluid present in the fluid circuit.

[0007] This is achieved by a method for operating a heating device for a fluid circuit of a motor vehicle with the features of claim 1. It is provided that, if a temperature threshold is exceeded, a second electrical connection between the second power supply and the control unit is interrupted to switch off the heating element.

[0008] Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments described in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are possible.

[0009] The method serves to operate the heating device, which is preferably part of the vehicle's fluid circuit. However, the heating device can, of course, also be separate from the fluid circuit, up to the point of being mounted on or within the fluid circuit. Similarly, the fluid circuit can be part of the vehicle or be arranged separately from it. The fluid circuit serves to regulate the temperature of a device requiring temperature control, for example, a battery, preferably a high-voltage battery of the vehicle. A high-voltage battery is understood to be a battery characterized by a comparatively high nominal voltage, preferably a nominal voltage of at least 100 V, at least 200 V, at least 400 V, or at least 800 V.

[0010] Temperature control comprises at least the supply of heat to the device to be temperature controlled via the fluid circuit. Optionally, heat can also be temporarily removed from the device to be temperature controlled. In this case, heat is thus temporarily supplied to and temporarily removed from the device to be temperature controlled, namely via the fluid circuit. For temperature control of the device to be temperature controlled, the fluid in the fluid circuit is preferably circulated within the fluid circuit at least temporarily.

[0011] The fluid circuit includes a heating element to supply heat to the equipment being heated. This heating element is designed and configured to supply heat to the fluid circuit and the fluid within it, which is then transferred to the equipment being heated. For this purpose, the heating element has an electric heating element that is electrically powered, for example, using electrical energy drawn from a battery. In addition to the heating element, the heating element also includes a control unit.

[0012] The heating element is connected to the first power supply, and the control unit to the second. The control unit has a switch that can be used to turn the heating element on or off. The switch is preferably an electrically operated switch that is normally open (normally de-energized). This means that the switch keeps the heating element on as long as it is energized. If the power supply to the electrically operated switch is interrupted, it turns the heating element off.

[0013] To activate the heating element, the control unit establishes, at least temporarily, the first electrical connection between the first power terminal and the heating element, so that the heating element is supplied with electrical current from the first power terminal and operates to heat the fluid circuit. The control unit is powered by electrical current supplied at the second power terminal. For example, the first and second power terminals may have different voltage levels. In particular, the first power terminal supplies electrical current at a voltage higher than the voltage supplied at the second power terminal.

[0014] The electrical voltage present at the first terminal can also be referred to as the first voltage, and the electrical voltage present at the second terminal as the second voltage. Preferably, the first voltage is higher than the second voltage by a factor of at least 2, at least 4, or at least 8. For example, the first voltage corresponds approximately to or exactly with the nominal voltage of the battery, i.e., at least 100 V, at least 200 V, at least 400 V, or at least 800 V. The second voltage, on the other hand, is at most 48 V, at most 24 V, or at most 12 V.

[0015] The aforementioned battery, when used in the motor vehicle, serves to supply at least one electrical component with electrical energy. This electrical component is, for example, a control unit, preferably a control unit of a driver assistance system. The driver assistance system, and thus the control unit, are particularly preferably designed and configured to enable at least partially or fully autonomous driving of the motor vehicle. This means that the driver assistance system takes over longitudinal and / or lateral control of the motor vehicle, at least temporarily, independently of a driver.

[0016] Longitudinal control refers to setting the vehicle's speed, while lateral control refers to steering the vehicle. Speed ​​is set, for example, by controlling a drive system and / or a braking system. The braking system serves to propel the vehicle and thus, at least temporarily, to provide drive torque for propelling the vehicle. The braking system also serves to decelerate the vehicle, preferably using a service brake.

[0017] The lateral control and steering of the vehicle is achieved primarily through the operation of the vehicle's steering system, specifically by adjusting the steering angle. This results in high safety requirements for the driver assistance system and its control unit, particularly according to ASIL D. Therefore, consistently reliable operation of the electrical system must be ensured, especially a reliable supply of electrical energy from the battery.

[0018] For this reason, thermal overload of the battery must be avoided. Such overload can occur, for example, if the heating element or a control unit controlling the heating element malfunctions. The heating element is preferably designed to heat the fluid to a temperature of at least 60 °C, at least 80 °C, or at least 100 °C if it is operated continuously. This can lead to excessively high battery temperatures. Preferably, the battery is equipped with over-temperature protection, which, if the battery temperature exceeds a certain threshold, electrically disconnects the battery from any circuit connected to it. For example, the aforementioned electrical device is connected to this circuit, so disconnecting the battery from the circuit also interrupts the power supply to the electrical device.

[0019] To avoid this situation, the heating device should be designed and / or operated in such a way that it reliably shuts down if the temperature exceeds the threshold value. This can be achieved, firstly, by appropriately upgrading the heating device's control unit. However, it is also desirable to retrofit an existing heating device without the described protective measure with such a feature. For this reason, according to the invention, the second electrical connection between the second power supply and the control unit is interrupted as soon as the temperature exceeds the threshold value, i.e., is higher than this value.

[0020] By interrupting the second electrical connection, i.e., by electrically disconnecting the control unit from the second power supply, the control unit prevents the heating element from being activated, and the heating element is reliably switched off if it was previously switched on. This ensures that no further heat is introduced into the fluid circuit from the heating element. The described procedure also has the advantage of avoiding direct switching of the heating element; rather, the first electrical connection between the first power supply and the heating element is not interrupted directly, but only indirectly, by interrupting the power supply to the control unit. Consequently, in the event of a control unit malfunction or faulty control of the control unit, the heating element will no longer be activated.

[0021] The described procedure can easily be retrofitted to existing heating systems, allowing the reliability of the power supply to the electrical equipment to be increased with relatively simple design measures. This is primarily due to the fact that the power supply to the control unit is interrupted, and thus indirectly also the power supply to the heating element. A direct interruption of the heating element's power supply and the associated switching at high electrical loads is therefore avoided, thus minimizing the necessary circuitry.

[0022] A further development of the invention provides that the interruption of the second electrical connection between the second power supply and the control unit can be reversible or irreversible. Reversible interruption of the second electrical connection means that, after interruption, the second electrical connection is either automatically re-established as soon as the temperature falls below the threshold value, or that the second electrical connection can be re-established by manually operating a control element of the heating device. Thus, reversible interruption occurs in such a way that no component of the heating device needs to be replaced to restore the second electrical connection.

[0023] Irreversible interruption of the second electrical connection, on the other hand, is achieved in such a way that the second electrical connection can only be restored by replacing a component of the heating device. Specifically, irreversible interruption is accomplished through an irreversible chemical, physical, and / or mechanical alteration of the component through which the control unit is electrically connected to the second power supply. Reversible interruption is achieved, for example, using a thermal switch, while irreversible interruption is achieved using a thermal fuse. In either case, the aforementioned advantages are reliably achieved.

[0024] A further development of the invention provides that the first electrical connection is a connection of a first circuit connected to a first battery, and the second electrical connection is a connection of a second circuit connected to a second battery. In other words, the first battery and the second battery are present, with the first battery being electrically connected to the first circuit and the second battery being electrically connected to the second circuit. The first electrical connection is part of the first circuit and thus electrically connected to the first battery; the second electrical connection is part of the second circuit and consequently electrically connected to the second battery.

[0025] This means that the heating element is powered by electrical energy drawn from the first circuit or battery, while the control unit is powered by electrical energy drawn from the second circuit or battery. It is possible that the two batteries, and therefore the two circuits, have different voltage levels. This has already been mentioned. In particular, the first battery is a high-voltage battery and the second battery is a low-voltage battery; the first battery therefore has a higher nominal voltage than the second battery.

[0026] In particular, the voltage levels of the two batteries differ by one of the factors already mentioned and / or correspond to one of the voltages already mentioned. It is particularly preferred that the two circuits are electrically connected to each other, especially via a voltage converter. Preferably, the second battery is charged, at least temporarily, with electrical energy drawn from the first circuit via the voltage converter. Due to the different batteries and the different circuits, the advantages described above can be realized particularly effectively.

[0027] A further development of the invention provides that the first battery has a higher nominal voltage than the second battery. This has already been mentioned. The nominal voltage of the first battery is preferably higher than the nominal voltage of the second battery by one of the aforementioned factors. The nominal voltage of the first battery and / or the nominal voltage of the second battery can each correspond to one of the aforementioned voltages; in particular, the nominal voltage of the first battery is at least 100 V, at least 200 V, at least 400 V, or at least 800 V, and the nominal voltage of the second battery is at most 48 V, at most 24 V, or at most 12 V. This also serves to realize the advantages explained above.

[0028] A further development of the invention provides that the heating device is used, at least temporarily, to heat the first battery. This has already been mentioned. The first battery is thermally connected to the fluid circuit so that heat introduced into the fluid circuit by the heating device is at least partially supplied to the first battery. This is particularly relevant at low ambient temperatures, where the temperature of the first battery is raised towards its operating temperature to ensure efficient operation. Using the described method, the first battery is protected particularly effectively from excessive thermal stress.

[0029] A further development of the invention provides that the heating element is connected to the first power terminal via an electrical switch controlled by the control unit. The electrical switch is preferably in the form of a transistor, particularly a power transistor. The electrical switch is especially preferably implemented as a MOSFET or power MOSFET, or as an insulated-gate bipolar transistor (IGBT). In each case, the electrical switch is controlled by the control unit, so that when the second electrical connection between the second power terminal and the control unit is interrupted, the control unit effectively prevents the electrical switch from being activated, or the first electrical connection is interrupted by means of the switch.

[0030] A further development of the invention provides that a normally open (NO) switch is used as the electrical switch. In a first switching state, the electrical switch interrupts the first electrical connection between the first power supply and the heating element, and in a second switching state, it establishes this connection. The control unit selects a switching state from the first and second switching states and sets this state on the electrical switch to control the heating element. The first switching state exists as long as the electrical switch is not energized, i.e., de-energized. The second switching state is only achieved by energizing the electrical switch.

[0031] By interrupting the second electrical connection between the second power supply and the control unit, the electrical switch is ultimately disconnected from the second power supply and thus de-energized. This means that by interrupting the second electrical connection between the second power supply and the control unit, the electrical switch is set to its first switching state and held in this state. This reliably switches off the heating element and prevents any heat from entering the fluid circuit from the heating element.

[0032] A further development of the invention provides that the interruption of the second electrical connection between the second power terminal and the control unit is effected by means of an over-temperature switch or a thermal fuse. The over-temperature switch is a temperature switch that interrupts the second electrical connection when the temperature exceeds a certain threshold and re-establishes it when the temperature falls below the threshold. For example, the over-temperature switch is designed as a bimetallic switch or as a liquid-filled temperature switch. The over-temperature switch is characterized by the fact that it reversibly interrupts the second electrical connection between the second power terminal and the control unit.

[0033] The thermal fuse, for example, has a metallic or organic melting element that melts when the temperature exceeds a certain threshold, thereby interrupting the second electrical connection between the second power supply and the control unit. The thermal fuse is characterized by the fact that the interruption of the second electrical connection is irreversible. To restore the second electrical connection, the thermal fuse must be replaced. In any case, the aforementioned advantages are achieved.

[0034] A further development of the invention provides that, when the temperature threshold is exceeded, a fluid pump used at least temporarily to circulate a fluid in the fluid circuit is also switched off. The fluid pump serves to circulate the fluid in the fluid circuit. This means that it pumps the fluid from the heating element to the device being cooled. To prevent fluid that has already been heated to an unacceptably high temperature from reaching the device being cooled, it is provided that not only the heating element but also the fluid pump is switched off.

[0035] For this purpose, a third electrical connection between one of the power terminals and the fluid pump is interrupted as soon as the temperature reaches or exceeds the threshold. For example, the fluid pump and the control unit are connected to the second power terminal, so that interrupting the second electrical connection between the second power terminal and the control unit simultaneously interrupts the third electrical connection between the second power terminal and the fluid pump. This measure provides particularly reliable protection for the equipment being temperature-controlled.

[0036] The invention further relates to a heating device for a fluid circuit of a motor vehicle, in particular for carrying out the method according to the explanations in this description, wherein the heating device comprises a heating element connected to a first electrical connection and a control unit connected to a second electrical connection for controlling the heating element, wherein the control unit is provided and configured to establish a first electrical connection between the first electrical connection and the heating element for heating the fluid circuit, at least temporarily. The heating device is provided and configured to interrupt a second electrical connection between the second electrical connection and the control unit to switch off the heating element when a temperature threshold is exceeded.

[0037] The advantages of such a design of the heating system and such a procedure have already been mentioned. Both the heating system and the method for operating it may be further developed as explained in this description, and reference is made to these explanations in that regard.

[0038] The features and combinations of features described in the description, in particular those described in the following figure description and / or shown in the figures, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. Thus, embodiments that are not explicitly shown or explained in the description and / or the figures, but which emerge from or can be derived from the explained embodiments, are also to be considered as encompassed by the invention.

[0039] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without limiting the invention. The only embodiment shown is... Fig. 1 A schematic representation of an area of ​​a motor vehicle, in particular showing a fluid circuit and a device to be tempered by means of the fluid circuit.

[0040] The Fig.Figure 1 shows a section of a motor vehicle 1, in particular a part of a drive system of the motor vehicle 1. The motor vehicle 1 has a fluid circuit 2 by means of which a first battery 3 is at least temporarily heated or cooled. The first battery 3 is part of a first electrical circuit 4, which is only shown here in a very schematic way. The first electrical circuit 4 is connected via a voltage converter 5 to a second electrical circuit 6, which is connected to a second battery 7. This connection can, of course, also be omitted.

[0041] The first battery 3 is thermally connected to the fluid circuit 2, and the fluid circuit 2 is operated, at least intermittently, to maintain the temperature of the first battery 3. For this purpose, a fluid is circulated in the fluid circuit by means of a fluid pump 8. In addition to the fluid pump 8, a heating device 9 is present in the fluid circuit 2, for example, fluidically located between the fluid pump 8 and the first battery 3. This means that the fluid pumped by the fluid pump 8 towards the first battery 3 first flows through the heating device 9. The heating device 9 heats the fluid, at least intermittently, before it reaches the first battery 3. For this purpose, the heating device 9 has a heating element 10, which is controlled by a control unit 11 of the heating device 9.

[0042] To operate the heating element 10, it is supplied with electrical energy from the first circuit 4. For this purpose, the control unit 11 temporarily establishes a first electrical connection between the first circuit 4, in particular a first terminal 12 of the first circuit 4, and the heating element 10. The control unit 11 preferably has a switch, in particular an electrical switch, for this purpose. In a first switching position of the switch, the first electrical connection between the first terminal 12 and the heating element 10 is interrupted, whereas in a second switching position it is established.

[0043] The control unit 11 is operated with electrical energy drawn from the second circuit 6, specifically from a second power connection 13. To prevent the first battery 3 from being exposed to fluid at an unacceptably high temperature, the second electrical connection between the second power connection 13 and the control unit 11 is interrupted when a temperature threshold is exceeded, thus switching off the heating element 10. The term "temperature" refers in particular to the temperature of the fluid circuit, preferably the fluid temperature itself, or at least a temperature dependent on the fluid temperature.

[0044] To interrupt the second electrical connection, the control unit 11 is electrically connected to the second power terminal 13 via an over-temperature switch 14 or, alternatively, via a thermal fuse. The over-temperature switch is arranged such that it switches according to the temperature, in particular the temperature of the fluid circuit, namely to interrupt the second electrical connection between the second power terminal 13 and the control unit 11. The control unit 11 is designed such that when its power supply is interrupted, i.e., when the second electrical connection between the second power terminal 13 and the control unit 11 is interrupted, the first electrical connection between the first power terminal 12 and the heating element 10 is also interrupted. For this purpose, the aforementioned switch is preferably designed as an electrical switch, more precisely as a normally open electrical switch.

[0045] Additionally, the fluid pump 8, together with the control unit 11, can be electrically disconnected from the second power connection 13, thus stopping the flow of fluid through the fluid circuit 2. This ensures particularly reliable protection of the first battery 3 against excessively high temperatures. At the same time, the described procedure can be implemented with simple means and is particularly suitable for retrofitting an existing motor vehicle 1. Furthermore, it avoids the direct switching of large electrical loads. REFERENCE MARK LIST: 1 motor vehicle 2 Fluid circuit 3 1. Battery 4 1. Circuit 5 voltage converters 6 2nd circuit 7 2nd battery 8 Fluid pump 9 Heating system 10 heating elements 11 Control unit 12 1. Power connection 13 2. Power connection 14 Over-temperature switches QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 4 145 575 A1

[0002] EP 4 215 411 A1

[0003]

Claims

[1] Method for operating a heating device (9) for a fluid circuit (2) of a motor vehicle (1), wherein the heating device (9) comprises a heating element (10) connected to a first electrical connection (12) and a control unit (11) connected to a second electrical connection (13) for controlling the heating element (10), wherein the control unit (11) establishes at least temporarily a first electrical connection between the first electrical connection (12) and the heating element (10) for heating the fluid circuit (2), characterized by , that if a temperature threshold is exceeded, a second electrical connection between the second power connection (13) and the control unit (11) is interrupted to switch off the heating element (10). [2] Method according to claim 1, characterized by that the interruption of the second electrical connection between the second power connection (13) and the control unit (11) is reversible or irreversible. [3] Method according to any one of the preceding claims, characterized by , that the first power connection (12) is a power connection of a first circuit (4) connected to a first battery (3) and the second power connection (13) is a power connection of a second circuit (6) connected to a second battery (7). [4] Method according to any one of the preceding claims, characterized by , that the first battery (3) is a battery which has a higher nominal voltage than the second battery (7). [5] Method according to any one of the preceding claims, characterized by , that the heating device (9) is operated at least temporarily to heat the first battery (3). [6] Method according to any one of the preceding claims, characterized by , that the heating element (10) is connected to the first power connection (12) via an electrical switch controlled by the control unit (11). [7] Method according to any one of the preceding claims, characterized by , that a normally open switch is used as the electrical switch. [8] Method according to any one of the preceding claims, characterized by , that the interruption of the second electrical connection between the second power connection (13) and the control unit (11) is carried out by means of an over-temperature switch (14) or a thermal fuse. [9] Method according to any one of the preceding claims, characterized by , that if the temperature exceeds the threshold value, a fluid pump (8) used at least temporarily to pump a fluid in the fluid circuit (2) is also switched off. [10] Heating device (9) for a fluid circuit (2) of a motor vehicle (1), in particular for carrying out the method according to one or more of the preceding claims, wherein the heating device (9) has a heating element (10) connected to a first electrical connection (12) and a control unit (11) connected to a second electrical connection (13) for controlling the heating element (10), wherein the control unit (11) is provided and configured to establish at least temporarily a first electrical connection between the first electrical connection (12) and the heating element (10) for heating the fluid circuit (2), characterized by , that the heating device (9) is designed and configured to interrupt a second electrical connection between the second power connection (13) and the control unit (11) to switch off the heating element (10) when a temperature threshold is exceeded.

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