Method and system for detecting a mechanical force acting on a vehicle battery

Abstract

The present invention relates to a method for detecting a mechanical force acting on a battery unit (5) of an at least partially electrically powered vehicle, which is in thermal contact with a liquid-based cooling system (2), wherein the pressure of the coolant in the cooling system (2) is detected by at least one pressure sensor (22) and, if a defined pressure value is exceeded, a notification of a mechanical force acting on the battery unit (5) is issued. The present invention further relates to a system for detecting a mechanical force acting on a battery unit and to an electric vehicle with such a system.

Description

[0001] The present invention relates to a method for detecting a mechanical force acting on a battery unit. In particular, the present invention relates to an improved method for detecting a mechanical force acting on a battery unit in thermal contact with a liquid-based cooling system.

[0002] The battery units of electrically powered vehicles make up a significant portion of the vehicle's cost-determining component, with battery longevity having a particularly significant impact on the vehicle's economic efficiency. In addition to wear and tear during normal use, batteries can also be damaged by external mechanical forces, thereby reducing their performance. In electrically powered vehicles, damage can occur particularly from below, as the relatively heavy batteries are typically installed close to the ground to ensure weight distribution and improve vehicle handling. Even with additional underride protection, battery cells can be damaged by a sudden mechanical impulse.A notification or the initiation of countermeasures following possible damage to the battery unit would be desirable.

[0003] However, known methods and systems for protecting batteries in vehicles still have potential for improvement.

[0004] The object of the present invention is to at least partially overcome at least one disadvantage of the prior art. In particular, it is an object of the present invention to provide a solution that enables an advantageous embodiment of a method and a system suitable for carrying out the method, wherein both the method and the system can improve the detection of mechanical forces on battery units.

[0005] The solution of the present invention is achieved by a method having the features of claim 1, a system having the features of claim 6 and an electric vehicle having the features of claim 10. Preferred embodiments of the invention are described in the subclaims, in the description or the figures, wherein further features described or shown in the subclaims or in the description or the figures may individually or in any combination constitute an object of the invention, unless the context clearly indicates the opposite.

[0006] The present invention relates to a method for detecting a mechanical force acting on a battery unit of an at least partially electrically driven vehicle that is in thermal contact with a liquid-based cooling system, wherein the pressure of the cooling liquid in the cooling system is detected by at least one pressure sensor and, if a predetermined pressure value is exceeded, a message about a mechanical force acting on the battery unit is output.

[0007] Such a method has clear advantages over state-of-the-art solutions.

[0008] This describes a method for detecting mechanical force impacts. Mechanical force impacts on a vehicle and its batteries can occur, for example, as a result of a strong mechanical impulse that is not adequately shielded by additional mechanical protective measures, such as underbody protection. Such an event can be triggered by a stone or similar object hitting the underbody at a sufficiently high speed.

[0009] The mechanical force is applied to a battery unit in thermal contact with a liquid-based cooling system. Previous heating and cooling systems for the battery cells are connected externally and usually underneath the battery cells. The heat is then dissipated via a TIM (thermal interface material), the cooling medium, through the cooling system. This cooling system is usually designed as a metal plate with embedded cooling channels through which a cooling liquid circulates.

[0010] The battery unit is part of an at least partially electrically powered vehicle. The method according to the invention is suitable for both fully and partially electrically powered vehicles, such as motor vehicles, freight transport vehicles, aircraft, or rail vehicles.

[0011] The pressure of the coolant in the cooling system is detected by at least one pressure sensor. The pressure of the coolant is measured, with the pressure sensor being in direct contact, i.e., located inside or on the coolant. Capacitive pressure sensors, inductive pressure sensors, piezoelectric pressure sensors, or piezoresistive pressure transducers can be used for pressure measurement. The pressure sensor can be located at any point in the cooling system's fluid.

[0012] If a specified pressure value is exceeded, a message is issued indicating a mechanical force acting on the battery unit. During normal operation, the coolant has a working pressure that fluctuates within certain limits; this pressure is typically provided by a pump. An additional mechanical impulse on the cooling system, and thus also on the coolant, briefly compresses it, resulting in a pressure peak that lies outside the normal working range. Depending on the pump used and the usual pressure fluctuations in the system, caused, for example, by temperature fluctuations within the coolant as a function of battery load, a mechanical impulse can contribute to an increase in pressure of, for example, greater than 1.5%, preferably greater than 2%, relative to the currently applied working pressure.If such a pressure increase is detected compared to the time average or other statistical values, a message can be sent to the driver or the vehicle system. For example, a voice or text output to the driver on a display is possible. However, this message can also be sent to the vehicle system in purely digital form, with the recorded pressure and time data of the event being stored in a memory. This memory can be read out, for example during maintenance, and further measures initiated. Depending on the magnitude of the pressure increase, further measures can also be initiated by the vehicle system, such as immediate shutdown of the vehicle or a recommendation for an immediate visit to the workshop.

[0013] The method according to the invention makes it possible to very easily and reliably detect mechanical loads on the underbody of a vehicle via the cooling system. Due to the thermal contact of the cooling system, it has surprisingly been shown that there is a very good correlation between the forces acting on the cooling system and the forces acting on the battery unit.

[0014] This is achieved by providing the method step of measuring the coolant pressure in the cooling system via at least one pressure sensor. If a specified pressure value is exceeded, a notification is issued indicating a mechanical force acting on the battery unit. By monitoring the pressure, mechanical impacts on the underbody and thus on the cooling system can be reliably detected. A strong mechanical impulse on the cooling system also triggers a mechanical impact on the battery system, which is thermally and mechanically coupled to it. The measurement of the forces acting on the battery is therefore indirect but highly correlated with these forces.

[0015] The above-described design therefore enables a particularly safe and reliable method. As described above, the method can determine the pressure in the cooling circuit with high temporal resolution and with a good ability to correlate the occurring pressure signals very reliably and precisely, thus enabling the initiation of reliably coordinated countermeasures.

[0016] Accordingly, it may be preferable for the pressure of the coolant to be recorded via at least two pressure sensors at different points in the cooling system. The use of at least two pressure sensors can have significant advantages over the use of a single pressure sensor. The measurement signals from both pressure sensors can be correlated and compared with each other so that the measurement of a single sensor can be confirmed using the measurement signals from the second sensor. For example, it may be possible for a message to be issued only in cases where at least two pressure sensors measure a pressure peak. If only one pressure sensor detects a pressure peak, this may be an incorrect measurement and this event is then not passed on or processed. The different points in the cooling system could be, for example, the inlet and outlet of the cooling system.Preferably, the different locations can relate to two distant positions in the cooling circuit. For example, the different locations can preferably be separated by a distance of greater than or equal to 20 cm, further preferably greater than or equal to 30 cm, and further preferably greater than or equal to 50 centimeters.

[0017] Additionally or alternatively, it may be advantageous to determine and output the location of the mechanical force acting on the battery unit based on the time difference between the pressure values ​​recorded by the two pressure sensors. Due to the fact that the two pressure sensors are spaced apart, a mechanical pulse is generally not recorded simultaneously by both pressure sensors via the coolant. The delay in the propagation time and the knowledge of the position of the two pressure sensors allow the point of impact of the mechanical pulse to be determined. This can then be forwarded or stored in the system.

[0018] It may further be preferred that the detection of a mechanical force acting on the battery unit also occurs as a function of the time derivative of the pressure. In addition to determining the absolute pressure by the pressure sensors, it may also be advantageous to use the derivative of the pressure as a function of time as a criterion for a mechanical impact. A very rapid change in pressure within a short time interval does not usually occur during standard operation of a cooling system and can therefore indicate the presence of mechanical damage.

[0019] It can also be advantageous to detect a mechanical force acting on the battery unit as a function of the cooling medium temperature. The absolute value of the pressure within the cooling system can also depend on the thermal load on the battery and thus on the coolant. Incorporating this parameter into the analysis of occurring pressure peaks can increase the significance for detecting a damage event.

[0020] Also described is a system for detecting a mechanical force acting on a battery unit of an at least partially electrically driven vehicle, wherein the battery unit has at least one cooling system with a liquid cooling medium circulating therein and a battery unit in thermal contact with the cooling system, wherein the system has at least one pressure sensor in the cooling circuit, wherein the pressure sensor is configured to detect the pressure present in the cooling circuit as a function of time.

[0021] This system reliably detects mechanical forces acting on the underbody of a vehicle. These mechanical forces lead to an increase in pressure in the cooling circuit, and this event is strongly correlated with mechanical forces acting on the battery unit. Furthermore, the system can include a unit capable of communicating with the vehicle's electrical or computer system and, for example, visually or acoustically informing the driver of the damage. This additional unit could, for example, be a computer unit with a memory. However, it is also possible for the computer unit to function solely as a memory, with the event being stored in this memory. During maintenance, the memory can be read, and the affected battery cells of the battery unit can be specifically checked.

[0022] It may further be preferred for the system to have at least two pressure sensors in the cooling circuit. By using at least two pressure sensors in the cooling circuit, the location of the mechanical load on the cooling circuit can be determined based on the difference in the temporal sequence of detection of the pressure increase. This allows the location of the mechanical load on the battery system to be narrowed down more precisely. Furthermore, the results from both pressure sensors can be compared. This can increase the statistical reliability of the detection.

[0023] Furthermore, it can be advantageous for the system to have at least two pressure sensors and at least one temperature sensor in the cooling circuit. By recording temperature values, temperature-related pressure fluctuations in the system can be detected and eliminated. This can increase the statistical reliability of the detection and also make small mechanical impulses caused by small but significant pressure peaks visible.

[0024] Preferably, at least one of the pressure sensors can be arranged at the inlet of the cooling system and at least one of the sensors at the outlet of the cooling system. The system can determine the location of the mechanical force particularly precisely in cases where the pressure sensors are as far apart as possible. This can be achieved, for example, if one of the sensors is mounted at the inlet and another sensor at the outlet of the cooling system.

[0025] Furthermore, the invention relates to an electric vehicle that has a system according to the invention. The safety of electric vehicles can be increased in particular by having a system according to the invention for detecting mechanical impacts on the battery system. Mechanical damage to the battery system can be detected immediately, and measures to rectify the damage can be initiated.

[0026] The invention is further explained below with reference to the figures, where individual or multiple features of the figures may constitute a feature of the invention, either individually or in combination. Furthermore, the figures are to be viewed only as examples and in no way limiting. Fig. 1 shows schematically an underbody structure for an at least partially electrically powered vehicle; Fig. 2 shows schematically the arrangement of a pressure sensor in the cooling liquid of a cooling system; Fig. 3 shows schematically the arrangement of several pressure sensors in the coolant of a cooling system.

[0027] In the Fig. Figure 1 schematically shows an underbody structure for an at least partially electrically powered vehicle. From bottom to top, this figure shows the mechanical underrun protection 1, the cooling system 2, the battery frame 3, the housing tray 4 for the battery unit 5, and the battery unit 5 itself. A mechanical impulse acting on the underrun protection 1 is ultimately transmitted via the cooling system 2 to the batteries of the battery unit 5. The mechanical impulse leads to a short-term compression of the volume of the cooling system 2 and thus to an increase in the pressure of the coolant circulating in the cooling system 2. Due to the mechanical and thermal contact between the cooling system 2 and the battery unit 5, the pressure increase itself and the level of the pressure can be used to infer a mechanical impulse on the battery unit 5. In this way, a mechanical load on the battery unit 5 can be reliably detected.

[0028] In the Fig. 2 schematically shows the arrangement of a pressure sensor 22 in the coolant of a cooling system 2. The cooling system 2 comprises several cooling coils 21, which together form a cooling circuit. The cooling system 2 has an inlet and an outlet for the coolant, wherein the coolant circulates in the cooling system 2. At one point in the cooling system 2, a pressure sensor 22 is arranged, which records the pressure of the coolant as a function of time. In the event of a mechanical impact on the underbody (not shown), the volume of the cooling system 2 is compressed and the pressure sensor 22 detects an increase in pressure. Due to the close contact between the cooling system 2 and the battery unit (not shown), forces are also exerted on the battery unit (not shown) by the mechanical impulse.Countermeasures or maintenance tasks can be initiated by reporting the event to the driver or by saving it in an electronic memory.

[0029] The Fig. 3 shows schematically the arrangement of several pressure sensors 22 in the cooling liquid of a cooling system 2. The basic structure corresponds to the structure from the Fig.2, wherein it is shown here that several pressure sensors 22 are arranged in the cooling system 2. It is shown that one pressure sensor 22 is arranged at the inlet of the cooling system 2 and another pressure sensor 22 is arranged at the outlet of the cooling system 2. By using two pressure sensors 22, the location of the mechanical pulse can be deduced from the different propagation times of the pressure increase through the cooling medium. This allows, for example, subsequent maintenance to be carried out in a more location-specific manner. The one or more pressure sensors 22 can, for example, be combined pressure and temperature sensors. By combining different sensor types, temperature effects of the coolant can be compensated for, thus achieving improved detection of mechanical pulses on the battery unit 5. List of reference symbols 1 underrun protection 2 Cooling system 3 battery frames 4 Housing tray 5 Battery unit 21 cooling coils 22 Pressure sensor

Claims

[1] Method for detecting a mechanical force acting on a battery unit (5) of an at least partially electrically driven vehicle which is in thermal contact with a liquid-based cooling system (2), characterized by that the pressure of the cooling liquid in the cooling system (2) is detected by at least one pressure sensor (22) and, if a predetermined pressure value is exceeded, a message is issued about a mechanical force acting on the battery unit (5). [2] Method according to claim 1, characterized by that the pressure of the cooling liquid is detected by at least two pressure sensors (22) at different points in the cooling system (2). [3] Method according to claim 2, characterized by that the location of the mechanical force acting on the battery unit (5) is determined and output from the time difference between the pressure values recorded by the two pressure sensors (22). [4] Method according to one of the preceding claims, characterized by that the detection of a mechanical force acting on the battery unit (5) also occurs as a function of the time derivative of the pressure. [5] Method according to one of the preceding claims, characterized by that the detection of a mechanical force acting on the battery unit (5) also occurs as a function of the temperature of the cooling medium. [6] System for detecting a mechanical force acting on a battery unit (5) of an at least partially electrically driven vehicle, wherein the battery unit (5) has at least one cooling system (2) with a liquid cooling medium circulating therein and a battery unit (5) in thermal contact with the cooling system (2), characterized bythat the system has at least one pressure sensor (22) in the cooling circuit (2), wherein the pressure sensor (22) is designed to detect the pressure present in the cooling circuit (2) as a function of time. [7] System according to claim 6, characterized by that the system has at least two pressure sensors (22) in the cooling circuit (2). [8] System according to claim 6 or 7, characterized by that the system has at least two pressure sensors (22) and at least one temperature sensor in the cooling circuit (2). [9] System according to one of claims 7 or 8, characterized by that at least one of the pressure sensors (22) is arranged at the inlet of the cooling system (2) and at least one of the sensors (22) is arranged at the outlet of the cooling system (2). [10] Electric vehicle, characterized by that the electric vehicle comprises a system according to one of claims 6 to 9.

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