Electrical energy storage with pressure device

Abstract

The invention relates to an electrical energy storage device (4), in particular for a vehicle, having a plurality of electrically connected individual cells (6) arranged to form a cell stack (2) and having a pressure device (10) for exerting targeted pressure on the cell stack (2), wherein the pressure device (10) comprises at least one pressure plate (14) which lies flat against one end of the cell stack (2), and two fluidically coupled fluid cylinders (12), one of which is coupled to the pressure plate (14) for exerting pressure on the cell stack (2).

Description

[0001] The invention relates to an electrical energy storage device for a vehicle having a housing in which a plurality of electrically connected individual cells arranged to form a cell stack and a pressure device for targeted pressure exertion on the cell stack are arranged.

[0002] Electrical energy storage devices typically expand when they are being charged or are in a state of full charge. They take up a smaller volume when they are being discharged or are in a state of full discharge. Due to such expansion tolerances, electrical energy storage devices are subjected to external mechanical pressure.

[0003] A solid-state battery unit is known from US 2023 / 0318052 A1. The solid-state battery unit comprises a battery module in which a plurality of solid-state battery cells are laminated; a pressure unit configured to apply pressure to the battery module; and a control unit configured to control the pressure unit. The control unit controls a pressure force of the pressure unit depending on a temperature of the battery module and a charge level of the battery module.

[0004] Alternative pressure units, for example, are designed as hydraulic systems. These have the disadvantage that, due to possible leaks, air or fluid can penetrate the interior of the energy storage device, which can lead to contamination or, in the case of moisture, corrosion or even electrical short circuits.

[0005] The invention is based on the object of providing an electrical energy storage device for a vehicle which is of simple construction and easily adjustable with regard to expansion tolerances.

[0006] The object is achieved according to the invention by an electrical energy storage device having the features of patent claim 1.

[0007] Advantageous embodiments of the invention are the subject of the subclaims.

[0008] The electrical energy storage device according to the invention comprises a plurality of electrically connected individual cells arranged to form a cell stack and a pressure device for targeted pressure exertion on the cell stack, wherein the pressure device comprises at least one pressure plate which lies flat against one end, in particular the front end, of the cell stack, and two fluidically coupled fluid cylinders, one of which is coupled to the pressure plate for exerting pressure on the cell stack.

[0009] Advantageous embodiments of the invention are the subject of the subclaims.

[0010] In one possible embodiment, the two fluid cylinders are coupled via a controllable fluid connection in such a way that they form a double-acting pressure unit, for example a double-acting pneumatic unit or a double-acting hydraulic unit for a forward stroke and a return stroke.

[0011] In a further development of the invention, it is provided that at least one sensor, a throttle valve and / or a controllable multi-way valve are connected into the fluid line.

[0012] For example, a first fluid cylinder can be designed as a pressure cylinder that is mechanically coupled to the printing plate. A second fluid cylinder can be designed, for example, as a drive cylinder that is fluidly coupled, on the one hand, to a drive unit for adjusting the drive cylinder and, on the other hand, to the pressure cylinder for exerting pressure.

[0013] Embodiments of the invention are explained in more detail below with reference to drawings.

[0014] Showing: Fig. 1 schematically shows a comparison between a cell stack of an electrical energy storage device arranged in a housing with fully charged individual cells and a cell stack arranged in a housing with half-charged individual cells, Fig. 2 a schematic representation of an electrical energy storage device with a pressure device comprising two fluidically coupled fluid cylinders, and Fig. 3 a schematic representation of an alternative electrical energy storage device with an integrated pressure device, which is arranged within a common housing with the cell stack.

[0015] Corresponding parts are provided with the same reference numerals in all figures.

[0016] Fig. 1 schematically shows a comparison between a cell stack 2 of an electrical energy storage device 4 arranged in a housing 1 with largely fully charged individual cells 6 (for example 100% SoC) and, for example, half-charged individual cells 6 (for example 50% SoC) and a resulting change in size 8, in particular a change in length due to an expansion of the individual cells 6 in the fully charged state.

[0017] The electrical energy storage device 4 is, in particular, a traction battery of an electric vehicle, a hybrid vehicle, or a fuel cell-powered vehicle, wherein the individual cells 6 can be, for example, solid electrolyte cells. Such individual cells 6 expand during electrical charging and decrease in volume when discharged. It is important that, regardless of the respective state of charge (SOC) of the individual cells 6, a certain pressure is exerted on the individual cells 6, in particular on their flat sides.

[0018] In the Fig. In the comparison shown in Figure 1 of the two cell stacks 2 arranged in the housing 1, the individual cells 6 shown on the left have a state of charge (SOC) of 100 percent, while the individual cells 6 of the same electrical energy storage device 4 shown on the right have a state of charge (SOC) of 0 percent. The resulting change in size 8 is also shown. If the individual cells 6 are charged, the spatial volume increases or is larger than that of less or uncharged individual cells 6.

[0019] Fig. 2 shows a schematic representation of the electrical energy storage device 4 with a pressure device 10, comprising two fluid cylinders 12 fluidly coupled to one another.

[0020] The pressure device 10 is used for a targeted or controlled pressure exertion on the cell stack 2 (in Fig. 1). The pressure device 10 can further comprise, for example, at least one pressure plate 14, which rests flat against one end, in particular the front end, of the cell stack 2, wherein one of the two fluidically coupled fluid cylinders 12 is coupled to the pressure plate 14 for exerting pressure on the cell stack 2.

[0021] The two fluid cylinders 12 can, for example, be coupled via a controllable fluid connection 16 in such a way that they form a double-acting pressure unit 18, in particular a double-acting pneumatic unit or hydraulic unit, for a lifting movement 100, in particular a forward stroke 102 and a return stroke 104.

[0022] At least one sensor 20, in particular a pressure sensor or the like, and / or a controllable multi-way valve 22, in particular a 3 / 2-way valve or the like, can be connected to the fluid connection 16, in particular a fluid line, for example a gas line or a liquid line. Additionally or alternatively, a sensor 20, in particular a pressure sensor, can be arranged in the region of the pressure plate 14, in particular between the pressure plate 14 and the cell stack 2. The sensor 20 can, for example, be a strain gauge (= strain gauge sensor), a metal thin-film sensor, a membrane sensor, or the like. The sensor 20 is designed, in particular, as a particularly thin and lightweight sensor 20.

[0023] A first fluid cylinder 12.1 is designed, for example, as a pressure cylinder that is mechanically coupled to the pressure plate 14. A second fluid cylinder 12.2 is designed, in particular, as a drive cylinder that is fluidly coupled, on the one hand, to a drive unit 24 for adjusting the second fluid cylinder 12.2 designed as a drive cylinder, and, on the other hand, to the first fluid cylinder 12.1 designed as a pressure cylinder for exerting pressure.

[0024] The drive unit 24 is designed, for example, as a spindle drive. The drive unit 24 comprises at least one threaded spindle 24.1 and a traveling nut 24.2, which is mounted for longitudinal movement on the threaded spindle 24.1, which can be driven by an electric motor 24.3. The traveling nut 24.2 is coupled to a transmission lever 24.4, which is coupled in motion to a piston 24.5 movably mounted in the second fluid cylinder 12.2. The threaded spindle 24.1 is arranged and rotatably mounted in the vehicle or on the housing 1 via a bearing 24.6.

[0025] Preferably, the first fluid cylinder 12.1 has a larger first diameter 26 than a second diameter 28 of the second fluid cylinder 12.2.

[0026] In the embodiment according to Fig. 2, the cell stack 2 and the pressure plate 14 as well as the first fluid cylinder 12.1 are arranged together in the housing 1. The second fluid cylinder 12.2 and the drive unit 24 as well as essential elements of the fluid connection 16 are arranged outside the common housing 1.

[0027] In order to reliably set an optimal pressure acting on the cell stack 2, a throttle valve 30, in particular a throttle check valve or the like, and / or a check valve 32 can additionally be arranged in the fluid connection 16.

[0028] To control the pressure acting on the cell stack 2, an electronic control unit 34, in particular a battery control unit, an ECU or the like, can be provided, which is coupled or connected via signal lines 23 to the multi-way valve 22, the at least one sensor 20 and the drive unit 24.

[0029] In addition, a filter unit 36 ​​can be provided for optimal pressure adjustment, which is fluidically connected, for example, to the fluid connection 16 or a bypass line 16.1 of the fluid connection 16.

[0030] The fluid cylinders 12 designed as a double-acting pressure unit 18 are provided to exert an optimal pressure on the individual cells 6 or the cell stack 2 with the individual cells 6 (also called battery cells) depending on the state of charge SOC (also called State of Charge or SoC for short).

[0031] The fluid cylinders 12 can each be designed as pneumatic cylinders or as hydraulic cylinders. By designing the two fluid cylinders 12 as a double-acting pressure unit 18, which are controllably fluidically coupled to each other, a conventional, complex compressor, in particular an air compressor, can be eliminated.

[0032] Instead, the second fluid cylinder 12.2 is provided, which has the smaller second diameter 28. The fluid cylinders 12 are preferably designed as pneumatic cylinders.

[0033] A rod end 24.7 of the piston 24.5, arranged outside a fluid-filled cavity 12.2.1, in particular the air-filled cavity 12.2.1, of the second fluid cylinder 12.2, is mechanically connected to the threaded spindle 24.1 via the transmission lever 24.4, to which the so-called traveling nut 24.2 is attached. This threaded spindle 24.1 is in turn rotatably mounted via the bearing 24.6, in particular a pivot bearing, and is driven by the electric motor 24.3, which is particularly relatively small (in terms of installation space and power).

[0034] The second fluid cylinder 12.2, whose piston 24.5 can then be moved back and forth according to the piston movement 106, in particular depending on the direction of rotation of the threaded spindle 24.1, is constructed such that it has a relatively small second diameter 28 and is longer in length than the first fluid cylinder 12.1.

[0035] The length of the threaded spindle 24.1 and the length of the possible piston movement 106 of the second fluid cylinder 12.2 can preferably be coordinated with one another. For example, the travel path of the transmission lever 24.4 arranged on the threaded spindle 24.1 with the traveling nut 24.2 can be designed to be long enough to correspond to the usable length of the piston 24.5 (= the piston rod) of the second fluid cylinder 12.2.

[0036] If the electrical energy storage device 4 (also called a battery) is discharged and the cell stack 2 becomes shorter as a result, the pressure acting on the cell stack 2 must be maintained as much as possible. This is achieved by activating the electric motor 24.3, which drives the threaded spindle 24.1, by means of a corresponding control signal from the control unit 34 (also called a control device or computer unit). The movement of the threaded spindle 24.1 causes the transmission lever 24.4 with the traveling nut 24.2 to move the piston 24.5 of the second fluid cylinder 12.2, so that the piston 24.5 is retracted into a cavity 12.2.1 of the second fluid cylinder 12.2.

[0037] The resulting reduction in the cavity 12.2.1 on the side facing away from the piston builds up a corresponding pressure in the fluid connection 16. The multi-way valve 22, which can also be controlled by the control unit 34 and which was initially in an initial state, is switched so that the fluid connection 16 is cleared for the flow of the fluid, in particular air or a hydraulic fluid. The compressed fluid, in particular air, flowing out of the cavity 12.2.1 is then guided via the throttle valve 30, in particular in the flow direction of an integrated check valve 30.1, and supplied to the first fluid cylinder 12.1, in particular its cavity 12.1.1, which exerts pressure on the cell stack 2 of the individual cells 6 via the corresponding pressure plate 14.

[0038] The sensor 20 can be arranged on the pressure plate 14. This sensor, for example, is a force sensor that measures the applied pressure force and transmits the determined value to the control unit 34 via the signal line 23, where it is taken into account when determining the optimal contact pressure, in particular depending on the state of charge (SOC) of the energy storage device 4. Alternatively or additionally, the sensor 20 arranged in the fluid connection 16 can be used to determine the optimal contact pressure.

[0039] The first fluid cylinder 12.1, which exerts the contact pressure on the cell stack 2, is designed such that it has a rather large first diameter 26. This first diameter 26 is particularly adapted to the installation space defined by the area of ​​the individual cells 6. Because the first fluid cylinder 12.1 exerts pressure on the individual cells 6 and its first diameter 26 is larger than the second diameter 28 of the second fluid cylinder 12.2, whose piston 24.5 drives the threaded spindle 24.1 via the transmission lever 24.4 with traveling nut 24.2 via the electric motor 24.3, such a pneumatic or hydraulic force transmission is possible that several forward and backward movements according to the piston movement 106 of the smaller second fluid cylinder 12.2 can exert a correspondingly large force on the cell stack 2 via the first fluid cylinder 12.1, which has a larger first diameter 26. In addition, the second fluid cylinder 12.2, whose piston 24.5 is driven by the threaded spindle 24.1 and has a piston movement 106 with a larger stroke than the first fluid cylinder 12.1, which exerts pressure or contact force on the cell stack 2, which also contributes to a favorable pneumatic or hydraulic power transmission.

[0040] If the electrical energy storage device 4 is now charged (= cell stack 2 expands and thus becomes longer / larger), a corresponding pressure from the cavity 12.1.1 of the first fluid cylinder 12.1, which exerts pressure on the cell stack 2, is reduced or "released" into the fluid connection 16. This can be done, for example, by controlling the multi-way valve 22. The fluid connection 16 is then released and the fluid, in particular air, can escape, for example, via the multi-way valve 22. To ensure optimal metering, the flow path here also leads via the throttle valve 30, in particular via its throttle 30.2, and not via the integrated check valve 30.1 as is the case when pressure is built up.

[0041] For example, the throttle 30.2 can be adjusted so that the fluid can escape only very slowly and the pressure can be reduced very precisely, thus allowing the contact pressure on the cell stack 2 to be adjusted very precisely. In addition, the throttle 30.2 can also be designed to be controllable.

[0042] In order to achieve high pressures, a worm gear (not shown) can also be used and interposed when driving the threaded spindle 24.1, so that the drive power for the electric motor 24.3 can be very low.

[0043] If the electrical energy storage device 4 is discharged (the volume of the individual cells 6 decreases), the corresponding contact pressure must be maintained. This is achieved by extending a pressure piston 12.1.2 of the first fluid cylinder 12.1 (= single-acting pressure cylinder) and exerting force on the cell stack 2 via the pressure plate 14.

[0044] The first fluid cylinder 12.1 is pressurized with fluid, in particular air, which is supplied from the second fluid cylinder 12.2. The piston 24.5 (also called the drive piston) of the second fluid cylinder 12.2 (also called the drive cylinder) is connected, in particular coupled, to the traveling nut 24.2 via the transmission lever 24.4. The transmission lever 24.4 with traveling nut 24.2 is arranged on the threaded spindle 24.1, so that when the threaded spindle 24.1 rotates, the transmission lever 24.4 and thus also the piston 24.5 of the second fluid cylinder 12.2 move or are moved in the axial direction according to the piston movement 106.

[0045] The compressed (pressurized) fluid, for example, air, in the cavity 12.2.1 of the second fluid cylinder 12.2 is guided through the multi-way valve 22, in particular a 3 / 2-way valve. The position shown is the preferred switching position of the multi-way valve 22.

[0046] The multi-way valve 22 opens the flow path through the fluid connection 16, and the fluid is directed to the throttle valve 30, which may be configured as a throttle check valve, for example. In this switching position, the flow path of the fluid connection 16 leads via the integrated check valve 30.1 (in the flow direction) into the second fluid cylinder 12.2. By pressurizing the second fluid cylinder 12.2 and the corresponding piston surface, force is exerted on the pressure plate 14.

[0047] If the energy storage device 4 is charged, the process occurs in reverse. Charging the energy storage device 4 increases the volume of the individual cells 6 or the length of the cell stack 2. The first fluid cylinder 12.1, in particular its pressure piston 12.1.2, must therefore be retracted in accordance with the change in length of the cell stack 2, but the pressure or contact force on the cell stack 2 must be maintained at an optimally appropriate level. By switching or controlling (e.g. via short pulses) the multi-way valve 22, designed as a 3 / 2-way valve, the flow path in the fluid connection 16 is clear and the fluid can escape via the multi-way valve 22. This reduces the pressure. The flow path leads from the first fluid cylinder 12.1 via the throttle 30.2 of the throttle valve 30. The integrated check valve 30.1 blocks this direction, so that the flow path leads via the throttle 30.2. The throttle 30.2 is set in such a way that only very little fluid can escape or this can only escape very slowly, so that a highly precise dosage of the pressure is possible and the pressure or the contact force on the cell stack 2 can be optimally adjusted or maintained.

[0048] All processes can be controlled via the control unit 34 and the signal lines 23. Information such as the state of charge (SOC) of the energy storage device 4, the battery temperature, or the like, in particular all parameters used to adjust the optimal contact force on the cell stack 2, are exchanged and processed accordingly.

[0049] The “filling” of the second fluid cylinder 12.2 with fresh air can, for example, be carried out from the environment via the bypass line 16.1 and optionally via the filter unit 36 ​​and the check valve 32, so that clean air from the environment can be used.

[0050] Fig. 3 shows a schematic representation of the electrical energy storage device 4 (shown in Fig. 1) with a pressure device 10 integrated into the housing 1. The pressure device 10 is arranged within the common housing 1 with the cell stack 2. In other words: The energy storage device 4 according to Fig. 2 differs from energy storage 4 according to Fig. 3 only in the size of the housing 1, which is in Fig. 3 is designed larger to accommodate all essential components of the printing device 10.

[0051] In particular, the cell stack 2 and all components of the pressure device 10 (also called the compression device) are arranged within the housing 1 (also called the battery housing). In this case, it is particularly important that the second fluid cylinder 12.2 and the threaded spindle 24.1 are designed such that they do not exceed the length of the cell stack 2 and the first fluid cylinder 12.1 (at the greatest possible extension of the cell stack 2 and the second fluid cylinder 12.2 in combination), thus ensuring that the housing 1 can be optimally designed with respect to the housing length and / or width.

[0052] By arranging all components in the common housing 1, the electrical energy storage device 4 with integrated pressure device 10 can be mounted and integrated into a vehicle, in particular a motor vehicle, an aircraft, a spacecraft, or the like, quickly and without any additional assembly effort. The "slim" design of the fluid compression in the form of the second fluid cylinder 12.2, for example, as a pneumatic cylinder rather than a conventional air compressor unit, enables a space-optimized solution, thereby saving space and weight.

[0053] Furthermore, the use of fluid cylinders 12 as drive cylinders, particularly fluid compression units, and / or pressure cylinders significantly reduces vibrations and excessive noise, which would be impossible with a conventional air compressor unit. Due to the large surfaces of the housing 1, there would also be a risk that these would act as a kind of "loudspeaker membrane," further amplifying the noise of a conventional air compressor unit. This is reliably avoided by the invention. List of reference symbols 1 housing 2 cell stacks 4 electrical energy storage 6 single cells 8 Resizing 10 Printing device 12 fluid cylinders 12.1 first fluid cylinder 12.1.1 Cavity 12.1.2 Pressure piston 12.2 second fluid cylinder 12.2.1 Cavity 14 printing plate 16 controllable fluid connections 16.1 Bypass line 18 double-acting pressure unit 20 sensors 22 Multi-way valve 23 Signal line 24 drive unit 24.1 Threaded spindle 24.2 Travelling nut 24.3 Electric motor 24.4 Transmission lever 24.5 pistons 24.6 Storage 24.7 Rod end 26 first diameter 28 second diameter 30 throttle valve 30.1 integrated check valve 30.2 Throttle 32 Check valve 34 Control unit 36 filter unit 100 lifting movement 102 Pre-stroke 104 return stroke 106 Piston movement SOC state of charge 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] US 2023 / 0318052 A1

[0003]

Claims

[1] Electrical energy storage device (4), in particular for a vehicle, with a plurality of electrically connected individual cells (6) arranged to form a cell stack (2) and with a pressure device (10) for the targeted application of pressure to the cell stack (2), characterized by that the pressure device (10) comprises at least one pressure plate (14) which lies flat against one end of the cell stack (2), and two fluidically coupled fluid cylinders (12), one of which is coupled to the pressure plate (14) for exerting pressure on the cell stack (2). [2] Electrical energy storage device (4) according to claim 1, characterized by that the two fluid cylinders (12) are coupled via a controllable fluid connection (16) in such a way that they form a double-acting pressure unit (18). [3] Electrical energy storage device (4) according to claim 2, characterized bythat at least one sensor (20), a controllable multi-way valve (22) and / or a throttle valve (30) are / is connected into the fluid connection (16). [4] Electrical energy storage device (4) according to one of the preceding claims, characterized by that a first fluid cylinder (12.1) is designed as a pressure cylinder which is mechanically coupled to the pressure plate (14), and a second fluid cylinder (12.2) is designed as a drive cylinder which is fluidly coupled on the one hand to a drive unit (24) for adjusting the drive cylinder and on the other hand to the pressure cylinder for exerting pressure. [5] Electrical energy storage device (4) according to claim 4, characterized by that the first fluid cylinder (12.1) has a larger first diameter (26) than a second fluid cylinder (12.2). [6] Electrical energy storage device (4) according to claim 4 or 5, characterized bythat the cell stack (2) and the pressure plate (14) and the first fluid cylinder (12.1) are arranged in a common housing (1) and the second fluid cylinder (12.2) and the drive unit (24) are arranged outside the common housing (1). [7] Electrical energy storage device (4) according to claim 4 or 5, characterized by that the cell stack (2), the pressure plate (14), the two fluid cylinders (12) and the fluid line (16) connecting them as well as the drive unit (24) are arranged in a common housing (1).

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