MOTOR VEHICLE WITH FUEL CELL PROPULSION

Abstract

In a motor vehicle with a fuel cell (2), a first cooling circuit (5) for cooling the fuel cell (2), a battery (3) and a second cooling circuit (12) for cooling the battery (3), the first and second cooling circuits (5, 12) are thermally coupled via a heat exchanger (11).

Description

[0001] The present invention relates to a motor vehicle with a fuel cell that supplies electrical energy for operating a drive motor of the vehicle, and a battery for temporarily storing the electrical energy. Both the fuel cell and the battery generate waste heat during operation and require cooling.

[0002] From KR 10-2022-0 0039913 A, a motor vehicle with a fuel cell and battery is known, each cooled by dedicated cooling circuits. The evaporator of the battery cooling circuit and a cooler of the fuel cell circuit are arranged in series in a shared cooling air flow. If the waste heat output of the fuel cell threatens to exceed the output of the cooler, the output of the fuel cell must be throttled to prevent overheating. Particularly on longer journeys with high power requirements, such as uphill driving or driving at sustained high speeds, this can lead to the required drive power no longer being provided even with the battery connected, and the cruising speed must be reduced.While one could attempt to dimension the radiator generously so that its performance would meet all requirements, such a radiator would be bulky and expensive, and its heavy weight would negatively impact the vehicle's fuel consumption and range.

[0003] One object of the invention is to provide a motor vehicle with a fuel cell drive in which, even without an oversized radiator, the risk of a permanently high power requirement not being met is low.

[0004] According to one aspect of the invention, this object is achieved by thermally coupling the first and second cooling circuits via a heat exchanger in a motor vehicle with a fuel cell, a first cooling circuit for cooling the fuel cell, a battery, and a second cooling circuit for cooling the battery. Since the heat exchanger allows the second cooling circuit to be used to dissipate heat load, particularly peak loads, from the fuel cell, a cooler for the first cooling circuit can be compactly dimensioned.

[0005] While the operating temperature of the battery is close to room temperature, that of the fuel cell is considerably higher, which also affects the temperatures in the coolant circuits. To accommodate this and protect the battery from excessively high temperatures, if the first cooling circuit comprises a cold branch, in which a heat transfer medium flows from a cooler to the fuel cell, and a warm branch, in which the heat transfer medium flows from the fuel cell to the cooler, a heat-absorbing side of the heat exchanger is located in the cold branch.

[0006] The second cooling circuit typically comprises a cold branch, in which a heat transfer fluid flows from a radiator to the battery, and a hot branch, in which the heat transfer fluid flows from the battery to the radiator. To ensure that the battery is not exposed to heat transfer fluid heated in the heat exchanger without prior cooling, a heat-dissipating side of the heat exchanger should be located in the hot branch of the second cooling circuit or in a shunt line connecting the hot and cold branches in parallel with the battery.

[0007] To ensure that the second cooling circuit is only used to support cooling of the fuel cell in the event of power peaks, the second cooling circuit should have a directional valve for selectively supplying the battery or the heat exchanger with heat transfer medium.

[0008] Alternatively, it is possible to use a thermosiphon as a heat exchanger and to prevent the circulation of a phase change heat transfer fluid in the thermosiphon, as long as the first cooling circuit alone is powerful enough to dissipate the waste heat from the fuel cell.

[0009] A control unit may be provided to control the directional control valve (or the circulation of the phase change heat transfer fluid in the thermosiphon) based on a current or predicted power of the fuel cell and / or an operating temperature measured at the first cooling circuit.

[0010] The forecast makes it possible, in particular, to proactively cool the fuel cell when high power requirements are expected. The forecast can be based, in particular, on information regarding the geographical position of the vehicle. For example, an upcoming incline on a road the vehicle is currently traveling on or is about to travel according to a route plan, or the designation of such a road as suitable for high speeds, can be used as a trigger for proactive cooling.

[0011] According to a further aspect of the invention, the object is achieved by a computer program product comprising computer-executable instructions that enable a computer to operate as a control unit in a motor vehicle as described above

[0012] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figure. It shows: Fig. 1 a block diagram of a motor vehicle according to the invention.

[0013] Fig.1 shows a motor vehicle with a drive motor 1 acting on a chassis and a fuel cell 2 that supplies electrical energy for operating the motor 1. A battery 3 is provided to temporarily store electrical energy from the fuel cell when the power of the fuel cell 1 temporarily exceeds the power consumption of the motor 2, or to supplement the power of the fuel cell 1 when the motor 1 briefly demands more power than the fuel cell 2 supplies. An on-board computer 4 is provided to control the power of the motor 2 based on short-term changes in a driver's requirements and to adjust the power of the fuel cell 2 over the long term, taking into account the charge level of the battery 3.

[0014] A first cooling circuit 5 comprises a heat exchanger 6 in contact with the fuel cell 2, a cooler 7, a hot branch 8, through which heat transfer fluid heated at the fuel cell 2 flows to the cooler 7, and a cold branch 9, through which the heat transfer fluid cooled in the cooler 7 flows back to the heat exchanger 6. A circulation pump 10 is provided on the cold branch 9. A section of the cold branch 9 runs through an internal heat exchanger 11.

[0015] A second cooling circuit 12 comprises a heat exchanger 13 in contact with the battery 3, a radiator 14, a hot branch 15, in which heat transfer fluid heated at the battery 3 flows to the radiator 14, and a cold branch 16, in which the heat transfer fluid cooled in the radiator 14 flows back to the heat exchanger 13. A circulation pump 17 is provided on the cold branch 15 or, as shown in the figure, on the warm branch 15. A shunt line 18, parallel to the heat exchanger 13, runs through the internal heat exchanger 11.

[0016] The on-board computer 4 controls the operation of the circulation pumps 10 and 17 and the position of a valve 19 in order to direct the heat transfer medium of the second cooling circuit 12 through the heat exchanger 13 or via the shunt line 18 through the internal heat exchanger 11 or possibly to distribute it between both.

[0017] Due to the different operating temperatures of the fuel cell 2 and the battery 3, the cold branch 9 of the first cooling circuit 5 is significantly warmer during operation than the warm branch 15 of the second cooling circuit 12, so that when heat transfer fluid circulates in the shunt line 18, heat flows from the first cooling circuit 5 into the second cooling circuit 12 via the internal heat exchanger 11. An exchange of heat transfer fluid between the circuits 5 and 12 does not occur.

[0018] The on-board computer 4 monitors the temperatures of the fuel cell 2 and the battery 3 and, based on the monitoring results, controls the operation of the circulation pumps 10, 17 assigned to them. Under normal operating conditions, this control occurs independently for both coolant circuits 5, 12. If the average power of the pump 10 exceeds a predetermined threshold and, at the same time, the temperature of the fuel cell 2 exceeds a safety threshold, the on-board computer 4 detects that normal operating conditions no longer exist, but rather high-performance operation. If, at the same time, the temperature of the battery 3 is at a tolerance threshold that should not be exceeded, and the circulation pump 17 is running at full load, the power of the fuel cell 2 must be throttled.If this is not the case, an interruption or reduction in battery cooling can be tolerated; in this case, the on-board computer 4 increases the power of pump 17 and switches the directional control valve 19 to a position in which the heat exchanger 13 is decoupled from the heat transfer medium flow, and the heat transfer medium instead flows through the bypass line 18 and the internal heat exchanger 11. This increases the cooling capacity available for the fuel cell 2.

[0019] Since the internal heat exchanger 11 is located in the first refrigerant circuit 5 behind the cooler 7, the temperature to which it is exposed is significantly lower than that of the fuel cell 2, so that the occurrence of critically high temperatures for the battery 3 in the second cooling circuit can be avoided.

[0020] Since battery 3 is no longer cooled in the now set position of directional control valve 19, its temperature rises. When it reaches the tolerance threshold, directional control valve 19 is switched again to cool battery 3 again. If the temperature of fuel cell 2 then remains below the safety threshold, the power peak has been successfully absorbed and a throttling of the fuel cell power has been avoided, and the power of pump 17 can be reduced again. If, however, the temperature of fuel cell 2 rises back to the safety threshold, directional control valve 19 is switched again, and the process described above is repeated.

[0021] According to a preferred further development, the on-board computer is connected to a known navigation system 20 and receives information from it about upcoming road conditions. This information may, for example, be an indication of an incline on an upcoming section of a road currently being traveled by the vehicle. Based on the length and gradient of the section or the elevation difference to be overcome and the expected time required for this, the on-board computer 4 estimates the resulting heat load for the fuel cell 2 and increases the cooling capacity for the fuel cell 2 before the incline is reached.This increase in cooling capacity can consist in simply increasing the power of the pump 10 in order to delay the point in time at which the second cooling circuit 12 must be used for support while driving uphill; however, the second cooling circuit 12 can also be used right from the start, as described above.

[0022] If the navigation system 20 provides information about a planned route, even more proactive cooling planning is possible. For example, it is possible to predict an upcoming long motorway journey which will require high power from the fuel cell 2, but at the same time, since the power fluctuates only slightly, places little strain on the battery 3. Since the battery 3 consequently generates little or no waste heat, its cooling circuit 12 is permanently available to support the cooling circuit 5, and the threshold for the average power of the pump 10, above which the cooling circuit 12 is activated, can be set lower than in a case where no information about the upcoming route is available or where normal load on the battery 3 is to be expected. Reference symbol 1 engine 2 fuel cells 3 Battery 4 on-board computers 5 Cooling circuit 6 heat exchangers 7 coolers 8 warm branch 9 cold branch 10 Circulation pump 11 internal heat exchanger 12 second cooling circuit 13 heat exchangers 14 coolers 15 warm branch 16 cold branch 17 Circulation pump 18 shunt line 19 Valve 20 Navigation system QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] KR 10-2022-0 0039913 A

[0002]

Claims

[1] Motor vehicle with a fuel cell (2), a first cooling circuit (5) for cooling the fuel cell (2), a battery (3) and a second cooling circuit (12) for cooling the battery (3), characterized by that the first and second cooling circuits (5, 12) are thermally coupled via a heat exchanger (11). [2] Motor vehicle according to claim 1, wherein the first cooling circuit (5) comprises a cold branch (9) in which a heat transfer medium flows from a cooler (7) to the fuel cell (2), and a warm branch (8) in which the heat transfer medium flows from the fuel cell (2) to the cooler (7), and wherein a heat-absorbing side of the heat exchanger (11) is arranged in the cold branch (9). [3] Motor vehicle according to claim 1 or 2, in which the second cooling circuit (12) comprises a cold branch (16) in which a heat transfer medium flows from a radiator (14) to the battery (3), and a hot branch (15) in which the heat transfer medium flows from the battery (3) to the radiator (14), and in which a heat-emitting side of the heat exchanger (11) is arranged in the hot branch (15) or in a shunt line (18) which connects the hot and cold branches (15, 16) in parallel to the battery (3). [4] Motor vehicle according to claim 1 or 2, wherein the second cooling circuit (12) has a directional control valve (19) for selectively supplying the battery (3) or the heat exchanger (11) with heat transfer medium. [5] Motor vehicle according to claim 4, comprising a control unit for controlling the directional control valve (19) based on a current or predicted power of the fuel cell (2) and / or an operating temperature measured at the first cooling circuit (5). [6] Motor vehicle according to claim 5, wherein the control unit is arranged to predict the performance of the fuel cell (2) based on information concerning the geographical position of the motor vehicle. [7] A computer program product comprising computer-executable instructions enabling a computer (4) to operate as a control unit in a motor vehicle according to claim 5 or 6.

Images