Valve with pressure equalization function, battery with such a valve and vehicle with such a battery

Abstract

Valve (1) comprising a valve body (2), a first valve element (3) arranged in a passage (23) of the valve body (2) with a valve needle (31) and a valve base (32), the movement of which is limited at least in a first direction (41) by a first valve seat (26), at least a second valve element (5) arranged in the valve body (2), the movement of which is limited in the first direction (41) by a second valve seat (27), and at least a third valve element (6) arranged in the valve body (2), the movement of which is limited in a second direction (42) by a third valve seat (28), wherein the passage (23) has a first opening (231) and a second opening (232) which is arranged opposite to the first opening (231), and wherein the first direction (41) and the second direction (42) are opposite to each other, wherein a leak testing device (8) can be connected to the valve (1), thereby characterizedthat the second opening (232) of the passage (23) is closed with a gas-permeable membrane (7), preferably an oleophobic membrane (7).

Description

State of the art The present invention relates to a valve, in particular a valve with a pressure equalization function, wherein the valve is preferably used in a battery for a motor vehicle that is at least partially electrically powered. Furthermore, the present invention relates to a battery with such a valve, in particular a lithium-ion battery pack, and to a motor vehicle equipped with a corresponding battery that has such a valve. In various technology sectors, highly advanced rechargeable batteries or battery packs—that is, a combination of several individual battery cells into a pack or assembly—have recently been increasingly used, for example, in the automotive sector to power an electric motor or an electric auxiliary motor that is used in addition to a conventional combustion engine, such as in a hybrid vehicle or similar. Lithium-ion battery assemblies, so-called lithium-ion battery packs, are used in particular, and their handling and operation require a wide range of safety precautions due to the highly reactive lithium. Since a battery pack is simply a combination of several individual batteries, the terms "battery" and "battery pack" will be used synonymously in the following text.The safety of these battery packs, also known as battery systems, is a key factor in their industrialization on the global market. Among other things, it is advantageous for such a lithium-ion battery pack to have pressure equalization between the battery pack housing and the environment to prevent damage to the housing caused by any pressure differences that may occur. Such pressure differences can arise, for example, during the transport of the lithium-ion battery pack in an airplane, when driving a vehicle equipped with a lithium-ion battery pack in a mountainous region, due to natural fluctuations in air pressure, or even simple temperature fluctuations.A pressure difference between the inside of the battery pack and its surroundings can place significant mechanical stress on the battery pack housing, potentially leading to minor or, in some cases, even severe damage. Aside from the possibility of unwanted leakage of battery contents, such a rupture could also allow moisture from the surrounding air to penetrate the battery pack's interior and condense, for example, on the cooling systems of the individual battery cells. This could result in substantial damage to the battery pack through corrosion or short circuits. To address this problem, known battery packs incorporate appropriate safety features, such as a pressure equalization element with a valve and a built-in desiccant, as described, for example, in DE 10 2010 063 423 A1. The safety mechanism described therein allows for any necessary pressure equalization between the interior of the battery pack housing and the surrounding environment, while the desiccant prevents moisture from entering the battery pack. Pressure equalization occurs only when a predetermined pressure differential between the interior of the battery pack and its surroundings is reached, due to a spring preload on the relevant components. This differential pressure overcomes the spring preload and opens the valve.Another example of the state of the art for a pressure equalization valve of a battery can be found in EP 0 504 573 A1, in which a lead-acid battery is equipped with a two-way relief valve, i.e. with a valve that allows venting in the case of a predetermined overpressure in the battery cell and ventilation in the case of a predetermined underpressure, by overcoming a spring force to open the valve in one direction or the other, which is adjustable according to the predetermined response pressure. An additional problem with the use of lithium-ion battery packs is that a defect or improper handling of the battery pack can lead to gas formation within the lithium-ion cells. This can also create a pressure difference between the interior of the battery pack and the surrounding environment, resulting in overpressure inside the cell. In some known battery packs, this problem has been addressed by a specially designed rupture membrane that opens or bursts at a certain internal pressure, allowing the gases to escape and thus preventing thermal runaway. However, due to their chemical composition, the escaping gases pose a significant risk to humans and the environment.In known battery packs, suitable systems are used to direct and neutralize gases in the event of damage. However, to ensure that gas exchange occurs only through the designated openings of the battery pack and that toxic gases cannot escape uncontrollably in the event of damage, the battery pack housing must be hermetically sealed. Therefore, a method for verifying the gas tightness of the battery pack is required at the latest upon completion of the battery pack, and this verification should preferably be possible without compromising the gas tightness of the battery pack housing. State of the art in this regard includes, for example, the publications DE 10 2011 122 349 A1 or JP H08- 138 713 A as well as the subsequently published publication DE 10 2013 213 909 A1 . Disclosure of the invention To address the problems discussed above, the present invention provides a valve with the features of claim 1, preferably for a lithium-ion battery. Furthermore, the present invention provides a battery with a valve according to the invention and a vehicle, preferably an electric vehicle or a hybrid vehicle, with such a battery. More precisely, the valve according to the invention comprises a valve body as its main component, which has a through-bore or a through-bore, and a first valve element arranged in the through-bore, which is provided with a valve needle and a valve base attached to it or formed integrally with it. The movement of the valve base, and thus the movement of the valve needle or of the entire first valve element, is limited at least in a first direction by a first valve seat, so that movement of the valve base in the first direction is prevented by the first valve seat.Furthermore, the valve has at least one second valve element also arranged in the valve body, the movement of which in the first direction is likewise limited by a valve seat, the so-called second valve seat, so that a movement of the second valve element, which preferably has a disc shape, in the first direction is stopped by the second valve seat. Finally, the valve according to the invention further has at least one third valve element also arranged in the valve body, the movement of which in a second direction is limited by a third valve seat, so that a movement of the third valve element, which preferably has a disc shape, in the second direction is stopped by the third valve seat.The passage provided in the valve body, which is preferably a central passage extending along the longitudinal axis of the valve body, has a first opening and a second opening that is arranged opposite to the first opening, so that the two openings are thus oriented in opposite directions. Furthermore, the previously defined first direction is essentially opposite to the second direction. An entry of a fluid flow in the first direction, such as an airflow or the like, into the passage of the valve body therefore occurs through the first opening, and an exit of this flow, if the first valve element allows unimpeded flow through the passage, occurs through the second opening. An entry of a flow traveling in the second direction into the passage of the valve body would occur through the second opening.However, since the movement of the first valve element is obstructed by the first valve seat, unimpeded flow from the second opening to the first opening is impossible. Therefore, the first valve seat is preferably designed in such a way that any flow entering the valve body through the first opening is interrupted. The valve base of the first valve element is preferably pre-tensioned against the first valve seat by a spring element, such as a simple spring in the form of a coil spring or a leaf spring. The first valve element, together with the valve body and its passage, as well as with the associated spring element, forms a so-called "Schrader valve," also known as a car valve. The second valve element is preferably pre-tensioned against the second valve seat by a spring element, such as a coil spring or a leaf spring, and the third valve element is preferably pre-tensioned against the third valve seat by a spring element, such as a coil spring or a leaf spring.The second valve element, together with the second valve seat in the valve body and the associated spring element, and the third valve element, together with the third valve seat in the valve body and the associated spring element, each form a so-called one-way valve. In the valve according to the invention, the Schrader valve, acting as a pressure test valve, and the two opposing one-way valves, acting as a pressure equalization valve arrangement or pressure equalization element, are thus combined into a single unit. This unit enables both the leak testing of a battery pack equipped with the valve according to the invention and the pressure equalization between the battery pack and the environment. It is mounted at a suitable location in the battery pack housing. Advantageous further developments of the invention are possible through the features of the dependent claims. According to the invention, the second opening of the passage is closed with a gas-permeable membrane, preferably an oleophobic membrane, which prevents moisture from penetrating the battery pack. More preferably, the second valve element is arranged in a channel within the valve body, and the third valve element can also be arranged in a further channel within the valve body, the channels preferably branching off from the passage, particularly at a point upstream of the passage in the first direction, which is located upstream of the first valve seat in the first direction. The channels, or air channels, for the preferably two one-way valves thus branch off from the opening for the Schrader valve.It is further preferable that the valve body tapers on the side of the second opening, at least over a section, meaning that the outer diameter of this section decreases or is smaller in this section than the rest of the valve body, with the valve needle preferably being arranged at least partially in a portion of the passage extending into the tapered section. The tapered section can be provided at least partially with an external thread through which, according to the invention, a leak tester can be connected to the valve. This means that when using the valve according to the invention with a battery pack, the Schrader valve serves to check the tightness of the battery pack housing.For testing purposes, an apparatus is connected to this part of the valve according to the invention, i.e., to the tapered section of the valve body. This apparatus fills the battery pack with a test gas, usually compressed air, up to a defined pressure. After reaching the test pressure, any pressure drop that may occur inside the battery pack housing is measured over a specific period. Based on this measurement, the tightness or degree of tightness of the battery pack housing can be determined. According to a further aspect of the invention, a battery or battery pack, in particular a lithium-ion battery or the like, is provided with a valve as previously described in the invention, wherein the valve is part of a battery housing to connect the interior of the battery to the environment when the valve is open. In a preferred embodiment, the valve is detachably connected to the housing, for example by means of a threaded connection or the like, but alternatively it can also be integrally connected to the battery housing or battery pack housing. Furthermore, according to a further aspect of the present invention, a motor vehicle is provided with such a battery or battery pack. Advantages of the invention The one-way valves of the valve according to the invention, which can also be referred to as pressure equalization elements, are "bypassed" during a leak test, thus eliminating the need for a gas-tight closure of the one-way valve openings for this test. The connection of the one-way valves to the Schrader valve enables both the leak test of the battery pack and the pressure equalization between the battery pack and the environment, and is mounted at only one suitable location in the battery pack housing. Therefore, the installation space required for its functionalities can be minimized by the valve according to the invention. Furthermore, the problems discussed above can be solved in a simple and effective manner. Brief description of the drawings Fig. 1 is a sectional view of a preferred embodiment of the valve according to the invention in the installed state in a battery; Fig. 2 is a sectional view of the preferred embodiment of the valve according to the invention in the installed state in a battery, in which a leak tester is connected to the valve and tests for leaks; Fig. 3 is a sectional view of the preferred embodiment of the valve according to the invention in the installed state in a battery, wherein the external pressure of the battery exceeds the internal pressure of the battery; and Fig. 4 is a sectional view of the preferred embodiment of the valve according to the invention in the installed state in a battery, wherein the internal pressure of the battery exceeds the external pressure of the battery. Preferred embodiment of the invention Figures 1, 2, 3 to 4 show a valve 1 according to a preferred embodiment of the invention in various actuation states. Figure 1 shows the valve 1 according to the invention in a rest state, mounted in a battery 9, more precisely in a battery housing, the outer wall 91 of which is represented in Figures 1, 2, 3 to 4 by a double-dotted / dashed line. The valve 1 is essentially a cylindrical component and primarily comprises a valve body 2, which in this embodiment consists of a section 21 with a small outer diameter, the so-called tapered section 21, and a section 22 with a large outer diameter, which forms the remainder of the valve body 2. In this embodiment, the tapered section 21 has a cylindrical shape, but can alternatively also be designed in a truncated conical shape or the like. Inside, the valve body 2 has a central through-bore 23 extending along its longitudinal axis, also called passage 23, which extends from an end face of the tapered section 21 to an end face of the section 22 with a large outer diameter. The passage 23 forms a first, preferably circular, opening 231 at the end face of the section 22 with the large outer diameter and a second, preferably circular, opening 232 at the end face of the tapered section 21. During normal operation of the valve 1, the first opening 232 is closed by a gas-permeable membrane 7, preferably a thin, oleophobic membrane 7, which is applied to the end face of the tapered section 21, for example by gluing or the like.In the area of ​​passage 23, which extends into the large outer diameter section 22, more precisely at a point 233 below the transition between the tapered section 21 and the large outer diameter section 22, two channels, the first channel 24 and the second channel 25, branch off from passage 23 into the surrounding area of ​​the large outer diameter section 22. After branching off, the two channels 24 and 25 run briefly essentially perpendicular to passage 23 and the longitudinal axis of the valve body 2, respectively, and then bend at a right angle towards the end face of the large outer diameter section 22. They extend to this face, thus running essentially parallel to passage 23 after the bend, and finally open into the interior of battery 9 at the end face of the large outer diameter section 22. A first valve element 3 is arranged in the passage 23, consisting of a valve needle 31 or valve pin 31 and a valve base 32, also referred to as the valve needle base 32. The valve needle 31 and the valve base 32 are preferably rotationally symmetrical components. The valve needle 31 is arranged at least partially in the portion of the passage 23 that extends into the tapered section 21 and has an outer diameter that is smaller than the inner diameter of the passage 23. The valve base 32, which is preferably designed in a disc shape, is arranged completely in the section 22 with the large outer diameter, more precisely in a first valve chamber 234 that is formed in the passage 23 in the section 22 with the large outer diameter. The first valve chamber 234 has a larger diameter than the passage 23, and the valve base 32 also has a larger diameter than the passage 23 but a smaller diameter than the valve chamber 234, so that the valve base 32 is located in the first valve chamber 234. The valve base 32 is biased by a spring 33 against a first valve seat 26, which is formed by an inner wall of the first valve chamber 234 on the side facing the second opening 232, so that the first valve element 3 is in a closed position in the rest state, i.e., in a state without a significant pressure difference between the two sides of the valve 1, with the valve base 32 biased towards the second opening 232 or towards the tapered section 21 and thereby closing the passage 23.On the side of the valve chamber opposite the first valve seat 26, a projection 2341 is provided, which does not extend over the entire inner circumference of the first valve chamber 234 but only over a specific angular circumferential range of the valve chamber interior, preferably between 45° and 180°, and more preferably over 90°. As shown, inter alia, in Fig. 2, the valve base 32 can rest against the projection 2341, so that only the specific angular circumferential range is closed off by the valve base 32 and the remaining angular circumferential range forms a continuous opening, so that the first valve element 3 is in a substantially open state without the valve base 32 being able to rest on the side of the first valve chamber 234 opposite the first valve seat 26 and completely close the first valve chamber 234, and thus the passage 23. During normal operation, which is shown in Fig.As shown in Figure 1, i.e., in a valve operation without a significant pressure difference between the outside and the inside of the battery 9, the first valve element 3, the so-called Schrader valve, completely closes the passage 23 with the help of the built-in spring 33. As can be seen in Fig. 2, a second valve chamber 241 is provided in the first channel 24, in which a second valve element 5 is arranged, the diameter of which is larger than the diameter of the channel 24 but smaller than the diameter of the second valve chamber 241. Similar to the valve base 32, the second valve element 5 is biased by a spring 51 against a second valve seat 27, which is formed by an inner wall of the second valve chamber 241 on the side of the second valve chamber 241 facing the second opening 232, so that the second valve element 5 is in a closed position at rest, biased towards the second opening 232 or towards the tapered section 21, and thereby closes the channel 24 at rest. As further shown in Fig.As can be seen from Figure 2, a third valve chamber 251 is provided in the second channel 25, in which a third valve element 6 is arranged, the diameter of which is larger than the diameter of the channel 25 but smaller than the diameter of the third valve chamber 251. Unlike the second valve element 5, or in the opposite direction to the second valve element 5, the third valve element 6 is biased by a spring 61 against a third valve seat 28, which is formed by an inner wall of the third valve chamber 251 on the side of the third valve chamber 251 facing the first opening 231, so that the third valve element 6 is in a closed position in the rest state, biased towards the first opening 231 and thereby closing the channel 25 in the rest state. Figure 2 also shows a leak tester 8 connected to the valve 1, which is connected to the tapered section 21 via a port 81, for example by a screw connection, wherein the port 81 can have an internal thread and the tapered section 21 a matching external thread. Any other type of fixed connection between the port 81 and the tapered section 21 of the valve body 2 of the valve 1 is also possible, such as a clamp connection or the like. The port 81 has an internal bolt 82 which, in the screwed-on state, actuates the valve needle 31, that is, presses downwards against the preload force of the spring 33, lifts the valve foot 32 from the valve seat 26 and thus opens the passage 23, so that a continuous fluid connection is created between the interior of the battery 9 and the leak tester 8.To check the tightness of the battery housing 91, a test gas, such as compressed air, helium, sulfur hexafluoride, or hydrogen, can be introduced into the housing 91, or the interior of the battery 9, via the test device 8. Since the test device 8 is connected to the valve 1 during the leak test, thus keeping the valve needle 31 depressed, the same pressure is achieved on both sides of the valve 1. The second valve element 5 and the third valve element 6, both of which are one-way valves, therefore remain in their respective rest positions. Using the test device 8, which stops the flow of the test gas when a predetermined maximum pressure is reached, the pressure inside the battery 9 can now be measured over a specific period, and any leaks can thus be detected by any pressure drop that may occur during this time. Figure 3 shows a state of valve 1 in which the ambient pressure of battery 9 is higher than the internal pressure of battery 9. In this state, the ambient overpressure causes the second valve element 5 to move against the preload force of spring 51, so that the second valve element 5 lifts off the second valve seat 27 and the one-way valve with valve element 5 opens the flow path between the environment, passage 23, first channel 24, second valve chamber 241 and the interior of battery 9. Thus, pressure equalization between the environment and the interior of battery 9 can occur. The first valve element 3 does not open in this case because the spring force of spring 33 is greater than the spring force of spring 51, and therefore the ambient overpressure cannot overcome the spring force of spring 33 and thus does not move valve element 3.If the ambient air pressure is higher than the pressure inside battery 9, which can represent a battery pack in this context, only the second valve element 5 opens after the tolerance threshold is exceeded, allowing air to flow into battery 9. The pressure difference can thus be equalized. Figure 4 shows a state of valve 1 in which the internal pressure of battery 9 is higher than the ambient pressure. Due to this internal overpressure, the third valve element 6 moves against the preload force of the spring 61, causing the third valve element 6 to lift off the third valve seat 28. This opens the one-way valve, with the valve element 6, the flow path between the interior of battery 9, the third valve chamber 251, the second channel 25, and the environment. Thus, pressure equalization between the interior of battery 9 and the environment can occur. Accordingly, once a certain tolerance threshold is exceeded, the valve element 6 opens and air flows outwards. The pressure difference can be equalized in this way.

Claims

Valve (1) comprising a valve body (2), a first valve element (3) arranged in a passage (23) of the valve body (2) with a valve needle (31) and a valve base (32), the movement of which is limited at least in a first direction (41) by a first valve seat (26), at least a second valve element (5) arranged in the valve body (2), the movement of which is limited in the first direction (41) by a second valve seat (27), and at least a third valve element (6) arranged in the valve body (2), the movement of which is limited in a second direction (42) by a third valve seat (28), wherein the passage (23) has a first opening (231) and a second opening (232) which is arranged opposite to the first opening (231), and wherein the first direction (41) and the second direction (42) are opposite to each other, wherein a leak testing device (8) can be connected to the valve (1), thereby characterizedthat the second opening (232) of the passage (23) is closed with a gas-permeable membrane (7), preferably an oleophobic membrane (7). Valve (1) according to claim 1, wherein the first valve seat (26) in the passage (23) is designed such that a flow which flows through the first opening (231) into the valve body (2) is interrupted when the valve base (32) comes into contact with the first valve seat (26). Valve (1) according to one of the preceding claims, wherein the second valve element (5) is arranged in a channel (24) in the valve body (2), and the third valve element (6) is arranged in a further channel (25) in the valve body (2). Valve (1) according to claim 3, wherein the channels (24, 25) branch off from the passage (23), preferably at a point (233) upstream of the passage (23) with respect to the first direction (41). Valve (1) according to one of the preceding claims, wherein the valve body (2) tapers at least over a section (21) on the side of the second opening (232), wherein preferably the valve needle (31) is arranged at least partially in a part of the passage (23) which extends in the tapered section (21). Valve (1) according to claim 5, wherein the tapered section (21) is at least partially provided with an external thread through which the leak test device (8) can be connected to the valve (1). Valve (1) according to one of the preceding claims, wherein the valve needle (3) with the valve base (32) is pre-tensioned against the first valve seat (26) by a spring element (33), and / or the second valve element (5) is pre-tensioned against the second valve seat (27) by a spring element (51), and / or the third valve element (6) is pre-tensioned against the third valve seat (28) by a spring element (61). Battery (9), in particular a lithium-ion battery, with a valve (1) according to one of the preceding claims, wherein the valve (1) is part of a housing (91) of the battery (9) to connect between the interior of the battery (9) and the environment of the battery (9) when the valve (1) is open, wherein preferably the valve (1) is detachably connected to the housing (91). Motor vehicle with a battery (9) according to claim 8 .

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