Technical Field

The invention relates to a pressure compensation device for an electronics housing, featuring a base body fluid-tightly connectable to an edge of a pressure compensation opening of the electronics housing, the base body in which at least one gas passage opening is provided, and an elastic membrane covering the gas passage opening, wherein the membrane is fluid-tightly connected to the base body in a region surrounding the at least one gas passage opening.

Background Art

A pressure compensation device of the above-mentioned type is known, for example, from DE 10 2012 213 697 A1 or DE 10 2012 022 346 B4.

Emergency venting of electrical equipment such as batteries is an important function to prevent the housing from bursting in the event of a pressure increase inside. Particularly in the case of high-voltage batteries such as those used as traction batteries in electric vehicles, battery cell failure can occur, leading to a sharp increase in pressure and temperature in the interior space of the housing. In order to prevent the housing from bursting, the hot and extremely pressurized gas must be quickly discharged from the interior space of the housing to the environment.

To prevent liquids or particles from the environment from entering the housing during normal operation, corresponding pressure compensation devices often have a membrane as a separation layer to the environment. The membrane should typically burst at a given pressure to allow emergency degassing.

Pressure compensation devices of the above-mentioned type can also be used for pressure compensation during normal operation of an electronics housing. Pressure differences between an interior space of the housing and the environment can be compensated by a (slow) gas exchange through the membrane.

The pressure compensation device known from DE 10 2012 022 346 B4 has a semi-permeable membrane. As a result, gas, in particular air, but substantially no water can pass through the membrane. The semipermeable membrane ensures a pressure compensation between the interior space of the housing and the environment. The above-mentioned DE 10 2012 213 697 A1 describes a sensor device for determining a pressure of a medium located inside a housing of an electrochemical energy storage device. In this case, the sensor device has a detection means that can be inductively coupled or is coupled to an electrically conductive layer that can be deflected by the pressure of the medium to be determined. In this connection, the detection means is designed to inductively detect a distance between the layer and the detection means that is dependent on the pressure of the medium to be determined, in order to determine the pressure of the medium from the distance. The electrically conductive layer can be shaped by means of deposition of an electrically conductive material or doping with an electrically conductive material. In this connection, the electrically conductive layer can be part of a membrane of the electrochemical energy storage device, in particular a burst membrane. As an alternative, the electrically conductive layer can be formed in the shape of a membrane of the electrochemical energy storage device, in particular a burst membrane. The detection means may be an electric coil with at least one winding. The coil is disposed on a support element in the shape of a circuit board at a distance from the membrane with the electrically conductive layer. Depending on a difference between the internal cell pressure or media pressure and the ambient pressure or external pressure, the membrane deforms, causing a distance between the detection means and the conductive layer or membrane to change, which in turn is detected by an electrical or electronic measurement using an evaluator electrically connected to the sensing unit. As a result, the pressure measurement is based on a modification in the distance between the membrane and the detection means, which is firmly attached to the housing.

It is an object of the invention to enable fault and performance monitoring on a pressure compensation device by simple means.

Summary of Invention

This object is solved by a pressure compensation device having the features specified in claim 1 an electronics housing according to claim 14 as well as a method according to claim 15. Preferred embodiments are specified in the subclaims and the description. According to the invention, a pressure compensation device for an electronics housing is provided. The electronics housing is preferably a battery housing, in particular for a traction battery of a motor vehicle. The electronics housing features a pressure compensation opening in a housing wall.

The pressure compensation device features a base body that is fluid-tightly connectable to an edge of the pressure compensation opening of the electronics housing. At least one gas passage opening is provided in the base body. In particular, a single gas passage opening can be provided. As an alternative, several gas passage openings can be provided in the base body, which can be separated from each other by webs or ribs, for example.

Furthermore, the pressure compensation device comprises an elastic membrane. The membrane covers the at least one gas passage opening. In this case, the membrane is fluid-tightly connected to the base body in a region surrounding the gas passage opening. In particular, the membrane can prevent particles and liquid from penetrating the electronics housing through the pressure compensation opening or the gas passage opening(s). Due to its elasticity, the membrane can deform when pressure differences occur between an interior space and an environment of the electronics housing.

According to the invention, the pressure compensation device features a sensor attached to the membrane for detecting a movement of the membrane. In this case, the sensor comprises a complete functional unit for detecting the movement of the membrane so that the sensor for movement detection does not interact with other components, for example on the base body or on the electronics housing. In other words, the sensor is a technical unit that functions on its own. This simplifies the construction and assembly of the pressure compensation device. In addition, to function correctly, it is not necessary to align or position the sensor in a defined manner relative to components other than the membrane. The movement of the membrane detected by the sensor allows the pressure compensation device itself or the electronics housing to be monitored. In particular, a bursting of the membrane can be detected based on the detected movements. Furthermore, the pressure difference between the interior space and the environment of the electronics housing can be inferred from the detected movements.

The solution according to the invention, according to which the sensor is attached to the membrane, is not comparable with approaches to membrane monitoring known in the background art, in which a membrane position is detected indirectly by sensors disposed separately from the membrane. In contrast, the invention relates to an in-situ arrangement of the sensor on the membrane. "Attached" in this context may in particular have the meaning "mechanically attached". "Movement" may in particular be understood to mean temporal change of a position of an object. The sensor may therefore in particular be designed to detect a temporal change of a membrane position and/or a velocity of a change of a membrane position.

In embodiments, the sensor is designed to continuously detect the movement of the membrane over a predetermined range of deflection of the membrane. This is a significant difference to background art approaches to membrane monitoring, in which only a membrane end position is monitored. The advantage of continuous membrane monitoring is that a possibly defective operating state can be detected much earlier than before. This makes it possible, in particular, to vary certain operating parameters (power input or output, cooling capacity) for the purpose of an anticipatory operation of a battery system equipped with the pressure compensation device according to the invention in order to avoid consequential damage to the battery system.

In the case of an unusually large inward movement, a correspondingly large pressure load from the outside, for example as a result of exposure to water, can be inferred.

In the case of an unusually large outward movement, a correspondingly large pressure load from the inside, caused, for example, by a malfunction in the interior space of the electronics housing, can be inferred. If this is liquid-cooled, a leakage in the cooling system in the interior space of the electronics housing can be detected. If there are battery cells in the electronics housing, a malfunction leading to outgassing from at least one cell can be detected quickly and unambiguously. Thus - depending on the cell type - a defective cell can be detected yet before the so-called "thermal breakdown". Consequently, corresponding warning signals can be emitted in time, critical functions can be switched off and/or safety functions can be activated so that thermal breakdown of the cells can be prevented as much as possible or at least the extent of the damage can be reduced.

If an emergency opening of the pressure compensation device due to bursting of the membrane as a result of a correspondingly large increase in pressure occurs, this can also be clearly detected by the sensor.

However, not only the potential bursting of the membrane can be detected by the sensor. Rather, by monitoring the movement of the membrane, a continuous diagnosis of the function of the membrane is possible. For this purpose, measured values from the sensor can advantageously be made available to a battery management system as on-board diagnostics.

The movement of the membrane detectable by the sensor can be a deformation of the membrane. In particular, the deformation can be an elongation of the membrane in its plane of extension.

Alternatively or additionally, the movement of the membrane detectable by the sensor can be a deflection of the membrane, in particular perpendicular to its plane of extension.

The sensor can be a strain gauge. In particular, the strain gauge can detect strains in the plane in which the membrane extends.

Either alternatively or additionally, the sensor can be a motion sensor, in particular a single-axis or multi-axis motion sensor. In particular, the motion sensor can detect deflections of the membrane perpendicular to its plane of extension. Preferably, the motion sensor is an accelerometer. Accelerometers are available at low cost and in very small size as well as very low mass. Furthermore, an accelerometer enables speed and/or displacement measurement by integration without the need to measure relative movements of the membrane to another component.

The sensor can be attached directly to the membrane, in particular glued to the membrane. This simplifies the assembly of the pressure compensation device.

The sensor can be a film sensor. A film sensor is particularly suitable for direct attachment to the membrane. The film sensor can be a printed film sensor, i.e. a sensor with conducting paths printed on a film. The film sensor can be a piezo film sensor. Piezo film sensors are available at low cost, in particular as printed film sensors, and they are suitable for strain measurement and/or pulse detection. The film sensor can contain a strain gauge.

As an alternative to direct attachment, the sensor can be attached to the membrane indirectly via a holding device. The holding device can simplify the attachment of the sensor to the membrane. The sensor can be bonded to the holding device. Preferably, the holding device is welded to the membrane, in particular by ultrasonic welding. This can make it easier to attach the sensor to the membrane, for example if in the case of a PTFE membrane it is difficult to attach the sensor directly.

The sensor can be inseparably attached to the membrane.

Preferably, the sensor is detachably attached to the membrane, in particular detachably attached to the holding device. Once the membrane has been replaced, for example if it has burst, it can still be used.

The pressure compensation device can feature a support grid overlapping the membrane on the inside (with respect to a state arranged on the electronics housing, wherein interior side means towards the interior space of the electronics housing). The support grid can prevent excessive deflection of the membrane in the event of external overpressure or impinging water, thus preventing damage to the membrane. The sensor is typically disposed on the interior side (the side facing the interior space of the electronics housing when mounted) of the membrane. The support grid can also prevent damage to the membrane and the sensor during assembly of the pressure compensation device or due to loose parts in the interior space of the electronics housing.

The support grid can hold the membrane on the base body in an area surrounding the at least one gas passage opening, in particular attach it to retaining webs of the base body. In the area of the gas passage opening, the membrane can be spaced apart from the support grid during normal operation.

The pressure compensation device typically features a cable leading to the sensor. The cable ensures the power supply to the sensor as well as the transmission of the measured values of the sensor to an electronic control unit. The support grid advantageously features a cable duct on which the cable leading to the sensor is held. The cable duct can reduce the risk of damage to the cable.

A connector for the sensor can be attached to the base body. The connector can be a plug connector, in particular female or male. The connector is basically connected to the sensor via the cable. The connector can be directly or indirectly attached to the base body, for example via the support grid. The connector allows in a simple manner to connect the sensorto a control unit when the pressure compensation device is mounted on the electronics housing. In particular, a further cable leading to the control unit can be connected to the connector for this purpose, preferably by setting up a plug connection.

The sensor can be covered by a protective cap. The protective cap can also cover the cable and, if necessary, the connector. The protective cap can be supported by the support grid. Damage to the above-mentioned components can thus be avoided particularly effectively.

At least one further sensor can be attached to the base body. The further sensor is used to detect a further parameter independently of the sensor on the membrane. For example, the further sensor can be a temperature sensor. Alternatively or additionally, a further sensor can be a moisture sensor. In particular, the moisture sensor enables the detection of air humidity or a humidity of a gas in the electronics housing. The further parameters detected by the at least one further sensor, further improve the possibilities for monitoring the proper functioning or an operating state of the pressure compensation device or the electronics housing. The further sensor can be attached to the base body directly or indirectly, for example via the support grid.

The membrane can be gas-permeable but fluid-impermeable. In other words, the membrane can be semi-permeable. The membrane thus allows a slow gas exchange between the interior space and the environment of the electronics housing. At the same time, the membrane prevents liquids and solids from entering the electronics housing. In particular, the semi-permeable membrane can completely prevent the ingress of water from the outside up to a defined water pressure, preferably up to a water pressure of at least 100, particularly preferably 250, very particularly preferably at least 3000 millimeters of water column. The semi-permeable membrane can feature an average pore size that can range from 0.01 micrometer to 20 micrometers. The porosity is preferably about 50%; the average pore size is preferably about 10 micrometers.

As an alternative, the membrane can be impermeable to fluids of all types, i.e. in particular gases and liquids. In other words, the membrane can be gas-permeable but fluid-impermeable.

The (in particular semi-permeable) membrane can be made of thermoplastic, for example polytetrafluoroethylene (PTFE). In particular, the membrane can be made of expanded or preferably sintered PTFE. As an alternative, the membrane can be made of (thermoplastic) polypropylene (PP).

The thickness of the membrane is basically much smaller than its other external dimensions. The membrane can cover a minimum width and/or a minimum length or a minimum external diameter of at least 20 mm, preferably of at least 30 mm, in particular of at least 40 mm. The membrane thickness can be at least 20 times, preferably at least 40 times, in particular at least 100 times, smaller than the minimum width and/or the minimum length or the minimum external diameter of the membrane. The membrane thickness can preferably be at least 1 micrometer, preferably at least 10 micrometers, wherein the membrane can feature, in particular over its entire membrane surface, a substantially constant membrane thickness. The membrane thickness can be at most 1 mm, particularly preferably at most 0.5 mm.

A covering hood can be disposed on the exterior side of the base body. The covering hood can prevent damage to the membrane from outside during operation of an electronics housing with the pressure compensation device. Between the covering hood and the base body, a flow path leading through the at least one gas passage opening basically remains open between the environment and the interior space.

Advantageously, the covering hood is latched to the base body. This simplifies the installation of the pressure compensation device.

A sealing element for sealing against the electronics housing can be disposed on the base body. The sealing element can be designed as axial seal or as radial seal, i.e. in particular on a front face (in the case of the axial seal) or on a circumferential surface (in the case of the radial seal). For a radial seal, the base body can feature a connecting piece for engaging in the pressure compensation opening. An axial seal can engage in a groove of the base body.

Also within the scope of the present invention is an electronics housing, in particular a battery housing, having a pressure compensation device as described above in accordance with the invention. The pressure compensation device is basically disposed at a pressure compensation opening of the electronics housing. The advantages of the pressure compensation device become apparent also and especially when using the electronics housing.

Further within the scope of the present invention is a battery, in particular a traction battery for a motor vehicle, which features an electronics housing or battery housing as described above in accordance with the invention and battery cells disposed in the battery housing. Here, the advantageous effects of the pressure compensation device are particularly apparent. The battery cells can be, for example, lithium ion cells.

Also within the scope of the present invention is a method for testing an electronics housing, in particular an electronics housing described above according to the invention or a battery described above according to the invention, wherein an internal pressure in the electronics housing is modified according to a predefined pressure profile and a motion profile of a membrane detected by a sensor during this process is compared with a reference motion profile. This results in a specific pressure change in the electronics housing. During the defined pressure change, the sensor detects the movement of the membrane. This motion profile is compared with the reference motion profile - either during or after the pressure change. The reference motion profile can be determined by changing the internal pressure according to the predefined pressure profile on a functional, in particular new, electronics housing and stored for the comparison. If the match between the detected motion profile and the reference motion profile is sufficiently accurate, it can be concluded that the electronics housing is intact and, in particular, that the pressure compensation device is intact. If the recorded motion profile deviates from the reference motion profile by more than a predefined amount, a defect in the electronics housing or the pressure compensation device can be inferred. The type of deviation can lead to conclusions about the type of defect. Corresponding limit values for comparing the detected motion profile and the reference motion profile can be predefined on the basis of typical damage patterns.

Brief Description of Drawings

Other features and advantages of the invention will become apparent from the following detailed description of embodiment examples of the invention, from the patent claims as well as with reference to the figures of the drawing which show details according to the invention. The aforementioned features and those described in still further detail can be implemented individually or in any number of appropriate combinations in variants of the invention. The features shown in the drawing are presented in such a way that the special features according to the invention can be made clearly visible.

In the drawing, the following is shown:

Fig. 1 a first embodiment of a pressure compensation device according to the invention having a sensor attached to a membrane, the sensor being connected via a cable to a plug connector, on which a further sensor is disposed, in a schematic perspective view looking at an interior side;

Fig. 2 the pressure compensation device of Fig. 1 in a schematic perspective view looking at an exterior side;

Fig. 3 a schematic exploded view of the pressure compensation device of Fig. 1 ;

Fig. 4 the pressure compensation device of Fig. 1 in a schematic, partially cut perspective view;

Fig. 5 a second embodiment of a pressure compensation device having a sensor attached to a membrane, the sensor being connected to a plug connector via a cable, and with a further sensor on a further plug connector, in a schematic, partially cut perspective view;

Fig. 6 a third embodiment of a pressure compensation device according to the invention having a film sensor attached to a membrane, the film sensor being connected via a cable to a plug connector, on which a further sensor is disposed, in a schematic perspective view looking at an interior side;

Fig. 7 the film sensor and the plug connector of the pressure compensation device of Fig. 6 as well as a protective cap therefor, in a schematic perspective view;

Fig. 8 an abstract representation of a battery having an electronics housing according to the invention, which features a pressure compensation device according to the invention;

Fig. 9 a schematic flow chart of a method according to the invention for testing an electronics housing.

Description of Embodiments

Figures 1 to 4 show a first embodiment of a pressure compensation device 10 for an electronics housing 12 shown in Figure 8 in various views. In the present case, the electronics housing 12 is a battery housing for a battery 14. A plurality of battery cells 16, for example lithium ion cells, are disposed in the electronics housing 12 or battery housing. The pressure compensation device 10 is disposed at a pressure compensation opening 18 in a housing wall of the electronics housing 12.

The pressure compensation device 10 features a base body 20. A gas passage opening 22 is provided in the base body 20, compare in particular Figures 3 and 4. The gas passage opening 22 is covered by a membrane 24. The membrane 24 is fluid- tightly connected to the base body 20 at its outer periphery. In the present case, the membrane 24 is covered by a support grid 26 fixing the membrane 24 to the base body 20. The support grid 26 is disposed on an interior side of the membrane 24 facing an interior space 28 of the electronics housing 12.

The membrane 24 can be semi-permeable, i.e. gas-permeable but fluid- impermeable, and can be made of PTFE, for example. Gas exchange can occur through the membrane 24 for pressure compensation between the interior space 28 and an environment 30 of the electronics housing 12.

On the exterior side of the embodiment shown, a covering hood 32 is disposed on the base body 20, compare in particular Figures 2, 3 and 4. The covering hood 32 and the base body 20 can be latched to one another. A flow path remains open between the covering hood 32 and the base body 20.

For sealing the base body 20 from the electronics housing 12, the pressure compensation device 10 features a sealing element 34. The sealing element 34 can engage in a groove 36 of the base body 20, compare in particular Figure 4. In the present case, the sealing element 34 is an axial seal.

A sensor 38 is attached to the membrane 24, compare Figures 1 , 3 and 4. The sensor 38 is used to detect movements of the membrane 24. Movements of the membrane 24 can be caused in particular by pressure differences between the interior space 28 and the environment 30 of the electronics housing 12. Bursting of the membrane 24 due to an excessively large pressure difference also results in a movement detectable by the sensor 38.

In the embodiment of the pressure compensation device 10 shown here, the sensor 38 is an accelerometer 40. In particular, the accelerometer 40 detects movements perpendicular to the plane of extension of the membrane 24 when the membrane 24 is deflected. Optionally, the accelerometer 40 can also detect movements occurring in the plane of extension of the membrane 24.

In this case, the sensor 38 is indirectly attached to the membrane 24 via a holding device 42. The holding device 42 can be non-detachably welded to the membrane 24, for example by ultrasonic welding. The sensor 38 can be releasably attached to the holding device 42, for example latched to the holding device 42. Alternatively, the sensor 38 can be releasably or non-releasably bonded to the holding device 42.

The sensor 38 is connected to a connector 46 via a cable 44. The connector 46 is designed here as a female plug connector. The connector 46 is attached to the base body 20. A further cable leading to a controlling device can be connected to the sensor 38 using a plug connection via the connector 46 (not shown in more detail).

The support grid 26 features a cable duct 48. The cable duct 48 is designed here as a hook. The cable 44 between the sensor 38 and the connector 46 is fixed to the support grid 26 using the cable duct 48. The pressure compensation device 10 can feature a further sensor 50. The further sensor 50 can be disposed on the connector 46. For example, the further sensor 50 can be a temperature sensor and/or a moisture sensor.

Figure 5 shows a second embodiment of a pressure compensation device 52. The pressure compensation device 52 of Figure 5 corresponds in design and function largely to the pressure compensation device 10 shown in Figures 1 to 4. In this respect, reference is made to the preceding description. The differences are presented below with priority.

In the pressure compensation device 52, a further sensor 50 is disposed on a further connector 54. The further connector 54 with the further sensor 50 is attached to the base body 20. The further connector 54 is designed here as a female plug connector.

No further sensor is provided at the connector 46 for the sensor 38 in the pressure compensation device 52. However, it would be conceivable to provide a further sensor at the connector 46.

Figure 6 shows a third embodiment of a pressure compensation device 56. The pressure compensation device 56 of Figure 6 corresponds in design and function largely to the pressure compensation device 10 shown in Figures 1 to 4. In this respect, reference is made to the preceding description. The differences are presented below with priority.

In the pressure compensation device 56, the sensor 38 is a film sensor 58. In this case, the sensor 38 is directly attached to the membrane 24. In particular, the sensor 38 can be welded to the membrane 24.

The film sensor 58 can be a printed piezo film sensor. The film sensor 58 allows detection of strains of the membrane 24, it is therefore a strain gauge. In other words, the sensor 38 can detect deformations of the membrane 24. In addition, the sensor 38 can enable detection of pulses occurring perpendicular to the plane of extension of the membrane 24, such as during possible bursting of the membrane 24.

Figure 7 shows the film sensor 58 of the pressure compensation device 56 of Figure 6 together with the cable 44 leading to the connector 46. Figure 7 also shows a protective cap 60 for the sensor 38, the cable 44 and the connector 46. The protective cap 60 can be attached to the support grid 26 covering the sensor 38, the cable 44 and the connector 46. Such a protective cap 60 could also be provided for the pressure compensation devices 10 or 52, compare Figures 1 to 4 or Figure 5.

Figure 9 shows a flow chart of a method of testing an electronics housing 14 having a pressure compensation device 10, 52 or 56 described above. In particular, the testing method allows the membrane 24 to be tested to determine whether or not it is gas permeable or gas impermeable to a desired degree.

In a step 102, an internal pressure in the interior space 28 of the electronics housing 14 is varied relative to an external pressure in the environment 30 in a predefined manner. In other words, the pressure difference between the interior space 28 and the environment 30 follows a predefined pressure profile.

The first execution of step 102 is carried out when the electronics housing 14 is new, if it can be assumed that the latter and, in particular, its pressure compensation device 10, 52 or 56 are intact. As an alternative, the first execution of step 102 can be carried out for identically constructed electronics housing 14 on an intact sample.

During the first pressure change according to step 102, a reference motion profile of the membrane 24 is recorded using the sensor 38 in a step 104. The reference motion profile is recorded.

Step 102 is repeated for the functional test. In other words, the internal pressure in the electronics housing 14 is changed again after some time according to the predefined pressure profile. During a further execution of step 102, a motion profile of membrane 24 is recorded using the sensor 38 in a step 106. This motion profile is compared to the reference motion profile in a step 108. If the motion profile and the reference motion profile match sufficiently precisely, the electronics housing 14 and in particular the membrane 24 are intact. If the motion profile deviates from the reference motion profile by more than a predefined amount, a defect is detected. It is understood that the sequence for the functional test outlined in dashed lines in Figure 9, i.e. the renewed execution of step 102 as well as the execution of steps 106 and 108, can be repeated several times. Reference Numerals

Pressure compensation device 10; 52; 56

Electronics housing 12

Battery 14

Battery cell 16

Pressure compensation opening 18

Base body 20

Gas passage opening 22

Membrane 24

Support grid 26

Interior space 28

Environment 30

Covering hood 32

Sealing element 34

Groove 36

Sensor 38

Accelerometer 40

Holding device 42

Cable 44

Connector 46

Cable duct 48 further sensor 50 further connector 54

Film sensor 58

Protective cap 60

Causing 102 a defined pressure change

Detecting 104 a reference motion profile

Detecting 106 a motion profile

Comparing 108 the motion profile and the reference motion profile