Sensor assembly for a motor vehicle, method for manufacturing a sensor assembly and motor vehicle with a sensor assembly

Abstract

The invention is directed at a sensor assembly (10) for a vehicle (34), designed to be mounted on a window glass (36) of the vehicle (34), the sensor assembly (10) comprising a main PCB (20), arranged inside a main compartment (14) of a housing (12) of the sensor assembly (10), a secondary PCB (22), arranged inside a secondary compartment (16) of the housing (12), and a sensor module (24) with a temperature sensor and a humidity sensor, wherein the module (24) is mechanically and electrically conductively connected to the secondary PCB (22). In the mounted position, the temperature sensor is designed to measure a temperature of the window glass (36) and the humidity sensor is designed to measure a humidity within a cabin (40) of the vehicle (34). The main PCB (20) and the secondary PCB (22) are electrically conductively connected to each other by an electrically conductive adhesive (32).

Description

[0001] Sensor assembly for a motor vehicle, method for manufacturing a sensor assembly and motor vehicle with a sensor assembly

[0002] An aspect of the invention is directed at a sensor assembly for a motor vehicle, which is designed to be mounted on a window glass of the motor vehicle. The sensor assembly comprises a combined sensor module with at least one temperature sensor and at least one humidity sensor, a so-called HT-sensor module (H: humidity; T: temperature), preferably arranged in a sensor-IC (IC - integrated circuit). Further aspects of the invention are directed at a method for manufacturing a sensor assembly and at a motor vehicle with a sensor assembly.

[0003] In the automotive industry, combined temperature and humidity measurements are widely used in order to predict fogging of one or more window glasses of a motor vehicle, preferably of the windshield of the motor vehicle. Therein, the temperature of the window glass and the humidity inside a vehicle cabin are measured and analyzed. The temperature and humidity sensors are preferably arranged in a combined sensor module, which can be integrated into a sensor assembly, which may further comprise rain and / or light sensors. Such sensor assemblies are often mounted within an area of the windshield of the motor vehicle close to the rear mirror.

[0004] In order to be able to reliably and accurately measure a temperature of the window glass, the temperature sensor of a sensor assembly as described above should be mounted in close or even direct physical contact to the window glass. Therefore, the combined sensor module is often not part of a main sensor printed circuit board (sensor PCB) of the sensor assembly and also not integrated into a main housing compartment of the sensor assembly. Instead, the combined sensor module is mechanically and electrically conductively connected to a secondary printed circuit board, which can be arranged in a secondary housing compartment. The secondary housing compartment can comprise a through-hole, through which the combined sensor module can be pressed against the window glass in a mounted position of the sensor assembly. To ensure full functionality of the sensor assembly as a whole, the main printed circuit board and the secondary printed circuit board are mechanically and electrically conductively connected to each other. An example of such a sensor assembly is known from CN 209525606 II, wherein the secondary printed circuit board is weldingly fixed on the main printed circuit board. In other words, the main and secondary printed circuit boards are welded together for mechanical and electrical connection.

[0005] In this context, US 7,770,433 B2 describes a humidity detector for detecting fogging on a window, for example the windscreen of a vehicle. The humidity detector comprises a housing adapted to hold a humidity sensor towards the windscreen of the vehicle or any other type of window. A flexible printed circuit board is arranged between the humidity sensor and the windscreen and provides a connection between the humidity sensor and further circuitry of the detector. The humidity sensor is located under a cap, which is engaged by a glider member. A spring pushes the glider member towards the windscreen.

[0006] According to the known solutions, the mechanical and electrical connection between the secondary printed circuit board and further circuitry is either provided by welding or via a mechanical connector, i.e. a further building component or construction part of the sensor assembly. These ways of connecting the secondary printed circuit board to further circuitry of the sensor assembly either is irreversible or extremely prone to wear, as it requires additional construction parts.

[0007] It is a subject of the present invention to provide an improved sensor assembly of the above described type, which overcomes the shortcomings of the known solutions.

[0008] This subject is solved by the subject-matter of the independent claims. Further embodiments of the invention are described by the dependent claims, the description and the figures.

[0009] A first aspect of the invention is directed at a sensor assembly for a motor vehicle of the described type, wherein the sensor assembly is designed to be mounted on a window glass of the motor vehicle, preferably on a windshield of the motor vehicle. The sensor assembly comprises a main printed circuit board, which is arranged inside a main compartment of a housing of the sensor assembly, a secondary printed circuit board, which is arranged inside a secondary compartment of the housing of the sensor assembly, and a combined sensor module with at least one temperature sensor and at least one humidity sensor, wherein the combined sensor module is mechanically and electrically conductively connected to a section of the secondary printed circuit board. In other words, the combined sensor module is mounted on the secondary PBC in the secondary compartment of the housing.

[0010] In the mounted position on the window glass of the vehicle, the at least one temperature sensor is designed to measure a temperature of the window glass and the at least one humidity sensor is designed to measure a humidity within a passenger cabin of the motor vehicle. In other words, the arrangement of the sensors is such, that in the mounted position, the temperature sensor is in close or even direct contact to the window glass. To this end, the secondary housing compartment may comprise a through-hole, through which the temperature sensor of the combined sensor module can be pressed against the window glass in the mounted position. At the same time, the humidity sensor may be fluidly coupled to air within the cabin of the motor vehicle, such that it can measure the humidity within the cabin.

[0011] According to the invention, the main printed circuit board and the secondary printed circuit board are electrically conductively connected to each other by an electrically conductive adhesive. In other words, instead of using a mechanical connector, the connection between the main PCB and the secondary PCB, for example a flex-band PCB, is done by using an electrically conductive bonding material, for example an electrically conductive glue or an electrically conductive epoxy, which is ensuring both the mechanical fixation and also the electrical connection of the secondary PCB to the main PCB. Preferably, the electrically conductive adhesive is placed to contact pads on one or both of the PCBs for better contact and for preventing damage on the PCB surfaces, which may be caused by the adhesive.

[0012] With the new solution the mechanical connector can be removed, thus decreasing the susceptibility to wear of the sensor assembly. Further, manufacturing of the sensor assembly may be accelerated, which may lead to cost reduction. The adhesive may also be easily removed, for example by applying a solvent, thus facilitating the disassembly of the components of the sensor assembly.

[0013] The invention includes embodiments that provide additional advantages.

[0014] Preferably, the main printed circuit board and the secondary printed circuit board have different intrinsic mechanical stiffnesses, wherein the main printed circuit board has a higher stiffness than the secondary printed circuit board, preferably wherein the secondary printed circuit board is foldable. In other words, the main PCB may be a rigid PCB made from a plastic or polymer material. The stiffness of the main PCB may be comparable to the stiffness of a metal sheet of a few millimeters thickness. The secondary PCB on the other hand may be a flexible PCB or a flex-band PCB. It may also be made form or contain a plastic or polymer material. Compared to the main PCB, however, the secondary PCB may have a reduced intrinsic stiffness. The intrinsic stiffness of the secondary PCB may be comparable to the stiffness of a sheet of writing paper, such that the secondary PCB may easily be bended or folded into a desired geometry. This way, the given assembly space within the housing compartments of the sensor assembly may best be used.

[0015] Preferably, the secondary printed circuit board is folded, at least with its section carrying the combined sensor module, between two opposing walls of the secondary compartment of the housing. Preferably, the secondary PCB is folded in a way that the combined sensor module, which is attached to it, is pushed through a through-hole in a wall of the secondary housing compartment, which is oriented essentially perpendicular to the two opposing walls.

[0016] Preferably, in the mounted position, the folded secondary printed circuit board is pressed against the window glass with its folded section, such that the at least one temperature sensor is pressed against the window glass. Caused by the intrinsic stiffness of the secondary PCB, the folding of it may cause a spring load, which presses the combined sensor module against the window glass, thus ensuring close or even direct physical contact between the temperature sensor and the window glass. In other words, the flexible or foldable secondary PCB has an electrical and a mechanical function.

[0017] Preferably, the main printed circuit board and the secondary printed circuit board each comprise a contact pad, wherein the electrically conductive adhesive is placed at least between the contact pads. The contact pads may protect the surfaces of the PCBs from a corrosive effect of the adhesive. The pads may further enhance the electrical connectivity or the quality of the electrical connection of the PCBs.

[0018] A further aspect of the invention is directed at a method for manufacturing a sensor assembly of the above described type, comprising the steps of

[0019] - providing a housing for the sensor assembly, comprising a main compartment and a secondary compartment,

[0020] - arranging a main printed circuit board in the main compartment and arranging a secondary printed circuit board in the secondary compartment, - mechanically and electrically conductively connecting a combined sensor module with at least one temperature sensor and at least one humidity sensor to a section of the secondary printed circuit board,

[0021] - applying an electrically conductive adhesive onto a surface of the main printed circuit board and / or onto a surface of the secondary printed circuit board, and

[0022] - electrically conductively connecting the main printed circuit board and the secondary printed circuit board to each other by pressing the surfaces against each other with the electrically conductive adhesive in between.

[0023] Preferably, the method further comprises the step of curing the electrically conductive adhesive by applying a curing temperature between including 120°C and including 150°C, preferably of 130°C, especially preferably of 140°C.

[0024] Preferably, the method further comprises the step of folding the secondary printed circuit board, at least with its section carrying the combined sensor module, between two opposing walls of the secondary compartment of the housing. The secondary PCB may be folded such that the at least one temperature sensor points in a direction towards a surrounding of the housing away from an interior of the housing. In other words, the folding may be such that the temperature sensor is pressed against the window glass in the mounted position.

[0025] A further aspect of the invention is directed at a motor vehicle with a sensor assembly according to the described embodiments, wherein the sensor assembly is mounted on a window glass, preferably a windshield, of the motor vehicle, wherein in the mounted position, at least one temperature sensor of the sensor assembly is designed to measure a temperature of the window glass by being pressed against the window glass, such that it is in close or even direct physical contact with the window glass, and a humidity sensor of the module is designed to measure a humidity within a passenger cabin of the motor vehicle, for example by being fluidly coupled to the passenger cabin.

[0026] Preferably, the motor vehicle further comprises a control unit, which is designed to receive temperature and humidity data from the sensor assembly and to asses a probability of fogging of the window glass based on the temperature and humidity data. If a predetermined probability for fogging is detected, the control unit may be designed to automatically activate a climate function of the motor vehicle to reduce the humidity inside the vehicle cabin and to reduce the probability for fogging. Alternatively or additionally, the control unit of the motor vehicle may produce a warning signal in response to the detected probability for fogging and transmit the warning signal to a warning device of the vehicle, for example a display device and / or an acoustic warning device with a loudspeaker. Like this, a driver of the vehicle can receive a visual and / or acoustic warning signal to prepare for fogging.

[0027] The motor vehicle can be a passenger car, a truck, a passenger bus or also a motorcycle.

[0028] The control unit may comprise one or more computing units. In the present disclosure, a computing unit may for example be understood as a data processing device with processing circuitry. A computing unit can therefore perform computing operations in order to process data. The computing operations may also include indexed accesses to a data structure, for example a look-up table, LUT.

[0029] In particular, a computing unit may include one or more computers, one or more microcontrollers, and / or one or more integrated circuits, for example, one or more application-specific integrated circuits, ASIC, one or more field-programmable gate arrays, FPGA, and / or one or more systems on a chip, SoC. The computing unit may also include one or more processors, for example one or more microprocessors, one or more central processing units, CPU, one or more graphics processing units, GPU, and / or one or more signal processors, in particular one or more digital signal processors, DSP. The computing unit may also include a physical or a virtual cluster of computers or other of said units.

[0030] A computing unit may also comprise one or more hardware and / or software interfaces and / or one or more memory units. Therein, a memory unit may be implemented as a volatile data memory, for example a dynamic random access memory, DRAM, or a static random access memory, SRAM, or as a non-volatile data memory, for example a readonly memory, ROM, a programmable read-only memory, PROM, an erasable programmable read-only memory, EPROM, an electrically erasable programmable readonly memory, EEPROM, a flash memory or flash EEPROM, a ferroelectric random access memory, FRAM, a magnetoresistive random access memory, MRAM, or a phase-change random access memory, PCRAM.

[0031] The preferred embodiments presented with reference to the sensor assembly according to the invention and the advantages thereof correspondingly apply to all of the further aspects of the invention and vice versa.

[0032] Further features of the invention are apparent from the claims, the figures and the description of figures. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of figures and / or shown in the figures alone are usable not only in the respectively specified combination, but also in other combinations without departing from the scope of the invention. Thus, implementations are also to be considered as encompassed and disclosed by the invention, which are not explicitly shown in the figures and explained, but arise from and can be generated by separated feature combinations from the explained implementations. Implementations and feature combinations are also to be considered as disclosed, which thus do not comprise all of the features of an originally formulated independent claim. Moreover, implementations and feature combinations are to be considered as disclosed, in particular by the implementations set out above, which extend beyond or deviate from the feature combinations set out in the relations of the claims.

[0033] Below, embodiments of the invention are explained in more detail based on schematic drawings.

[0034] There show:

[0035] Fig. 1 a schematic representation of a sensor assembly according to the state of the art;

[0036] Fig. 2 a schematic detailed view of the sensor assembly of Fig. 1 ;

[0037] Fig. 3 a schematic representation of a sensor assembly according to an embodiment of the invention;

[0038] Fig. 4 a schematic detailed view of the sensor assembly of Fig. 3;

[0039] Fig. 5 a schematic representation of a method for manufacturing a sensor assembly according to an embodiment of the invention; and

[0040] Fig. 6 a schematic representation of a motor vehicle with a sensor assembly according to an embodiment of the invention. In the figures, identical or functionally identical elements are provided with the same reference characters.

[0041] Fig. 1 shows a schematic representation of a sensor assembly 10 as known from the art. The sensor assembly 10 comprises a housing 12 with a main compartment 14 and a secondary compartment 16. The main housing compartment 14 and the secondary housing compartment 16 may be separated by a partition wall 18. The housing 12 may be made of or comprise a plastic material. Preferably, the housing 12 provides some protection for the electrical components within the housing 12 against electromagnetic radiation. To this end, the housing 12 may at least partially contain a metal material.

[0042] Within the housing 12, electrical components of the sensor assembly 10 are arranged on a printed circuit board (PCB). Therein, a main PCB 20 is arranged in the main compartment 14 and a secondary PCB 22 is arranged in the secondary compartment 16 of the housing 12. On the main PCB 20, different electrical components, for example control units for different sensors of the sensor assembly 10, may be mounted. On the secondary PCB 22, a combined sensor module 24 (see Fig. 2) may be mounted. The combined sensor module 24 may comprise at least one temperature sensor and at least one humidity sensor of the sensor assembly 10. For mechanically and electrically conductively connecting the secondary PCB 22 with its combined sensor module 24 to the main PCB 20, the secondary PCB 22 may be put through a through-hole within the partition wall18 and connected to the main PCB 20 via a mechanical and electrical connector 26.

[0043] The secondary PCB 22 may be formed as a flex-band PCB, that is a flexible or bendable or foldable band, that can be folded between the walls of the secondary compartment 16. As can be seen from Fig. 1 , the folding may be done in what essentially resembles a II- shape. Therein, one end of the secondary PCB 22 is put through the through-hole in the partition wall 18 and is connected to the main PCB 20 via the connector 26. The opposing end of the secondary PCB 22 is hooked to a hook 28 in one of the walls of the secondary compartment 22 to keep it in place. By folding the secondary PCB 22 into the secondary compartment 16, a preload or pretension is created, which is caused by the deformation of the secondary PCB 22. The amount of preload or pretension that is created by the folding depends on the intrinsic stiffness of the secondary PCB 22. The stiffer the secondary PCB 22, the higher the amount of preload will become. The preload will push the combined sensor module 24 in the direction of arrow 30 (the reader is referred to Fig. 2 for further explanation, especially with regard to the positioning of the combined sensor module 24). In the mounted state of the sensor assembly 10 on a window glass of a motor vehicle, arrow 30 will point towards the window glass, thus the combined sensor module 24 will be pressed against the window glass by the preload of the folded secondary PCB 22.

[0044] Fig. 2 shows, with reference to what has been described in the context of Fig. 1 , a detailed schematic view of the sensor assembly 10, as known from the art. In this view, the positioning of the combined sensor module 24 on the secondary PCB 22 is clearly visible. The combined sensor module 24 is pushed in the direction of arrow 30 by the preload of the folded secondary PCB 22. Thus, the secondary PCB 22 has a mechanical and an electrical function.

[0045] Fig. 3 shows a schematic representation of a sensor assembly 10 according to an embodiment of the invention. The sensor assembly 10 as shown in Fig. 3 differs from the sensor assembly 10 as shown in Figs. 1 and 2 only in the way of connecting the secondary PCB 22 to the main PCB 20. According to the shown embodiment, the secondary PCB 22 is mechanically and electrically conductively connected to the main PCB 20 by an electrically conductive adhesive 32. The adhesive 32 may comprise an electrically conductive pad or an electrically conductive epoxy resin or an electrically conductive glue or a combination thereof. For ensuring its electrical conductivity, the adhesive 32 may contain graphene particles and / or graphene fibers, which may be woven into an adhesive pad.

[0046] As an alternative solution, reference sign 32 may refer to a contact pad, which may be arranged on an end of the secondary PCB 22. In this case, the electrically conductive adhesive may be arranged between the pad 32 and a surface of the main PCB 20. On the surface of the main PCB 20, there may also be a contact pad 32, such that the electrically conductive adhesive may be arranged between the two pads 32. In the view of Fig. 3, the adhesive between the pads 32 is not explicitly shown for the sake of clarity of the figure.

[0047] Fig. 4 shows, with reference to what has been described in the context of Figs. 1 to 3, a schematic detailed view of the sensor assembly 10 as shown in Fig. 3. For the sake of clarity, only the PCBs 20, 22 and the adhesive 32, here again shown as a contact pad, are shown.

[0048] Fig. 5 shows a schematic representation of a method for manufacturing a sensor assembly 10 according to an embodiment of the invention. In a step S5.1 a housing 12 for the sensor assembly 10 is provided, the housing 12 comprising a main compartment 14 and a secondary compartment 16. In a step S5.2, a main printed circuit board 20 is arranged in the main compartment 14 and a secondary printed circuit board 22 is arranged in the secondary compartment 16. In a step S5.3, which can be performed before or after placing the secondary printed circuit board 22 in the secondary compartment 16, a combined sensor module 24 with at least one temperature sensor and at least one humidity sensor is mechanically and electrically conductively connected to a section of the secondary printed circuit board 22. In a step S5.4, an electrically conductive adhesive 23 is applied onto a surface of the main printed circuit board 20 and / or onto a surface of the secondary printed circuit board 22. In a consecutive step S5.5, the main printed circuit board 20 and the secondary printed circuit board 22 are electrically conductively connected to each other by pressing the surfaces against each other with the electrically conductive adhesive 32 in between.

[0049] In the method, steps S5.2 to S5.4 can be performed in any order, depending on the layout and construction of a respective assembly line. After having applied the electrically conductive adhesive 32, there may be an additional curing step, during which the adhesive 32 may be cured by a curing temperature between 120°C and 150°C, depending on the composition of the adhesive 32.

[0050] Fig. 6 shows a schematic representation of a motor vehicle 34 with a sensor assembly 10 according to an embodiment of the invention being mounted on a window glass 36 of the motor vehicle 34. In the shown embodiment, the window glass 36 belongs to the windshield of the motor vehicle 34. The sensor assembly 10 is mounted on an interior side of the windshield, such that in the mounted position, the combined sensor module 24 is pressed against the window glass 36 in the direction of arrow 30.

[0051] The motor vehicle 34 may further comprise a control unit 38, which may be designed to receive temperature and humidity data from the sensor assembly 10 and to asses a probability of fogging of the window glass 36 based on the temperature and humidity data. If a predetermined probability for fogging is detected, the control unit 38 may be designed to automatically activate a climate function of the motor vehicle 34 to reduce the humidity inside the vehicle cabin 40 and to reduce the probability for fogging. Alternatively or additionally, the control unit 38 of the motor vehicle 34 may produce a warning signal in response to the detected probability for fogging and transmit the warning signal to a warning device of the vehicle 34, for example a display device and / or an acoustic warning device with a loudspeaker. Like this, a driver of the vehicle 34 can receive a visual and / or acoustic warning signal to prepare for fogging.

[0052] Overall, the examples show, how a sensor assembly can be improved by electrically conductively connecting a main and a secondary PCB of the sensor assembly by an electrically conductive adhesive.

Claims

Claims1 . Sensor assembly (10) for a motor vehicle (34), which is designed to be mounted on a window glass (36) of the motor vehicle (34), the sensor assembly (10) comprising- a main printed circuit board (20), which is arranged inside a main compartment (14) of a housing (12) of the sensor assembly (10),- a secondary printed circuit board (22), which is arranged inside a secondary compartment (16) of the housing (12) of the sensor assembly (10), and- a combined sensor module (24) with at least one temperature sensor and at least one humidity sensor, wherein the combined sensor module (24) is mechanically and electrically conductively connected to a section of the secondary printed circuit board (22), wherein in the mounted position on the window glass (36) of the motor vehicle (34), the at least one temperature sensor is designed to measure a temperature of the window glass (36) and the at least one humidity sensor is designed to measure a humidity within a passenger cabin (40) of the motor vehicle (34), characterized in that the main printed circuit board (20) and the secondary printed circuit board (22) are electrically conductively connected to each other by an electrically conductive adhesive (32).

2. Sensor assembly (10) according to claim 1 , wherein the main printed circuit board (20) and the secondary printed circuit board (22) have different intrinsic mechanical stiffnesses, wherein the main printed circuit board (20) has a higher intrinsic stiffness than the secondary printed circuit board (22), preferably wherein the secondary printed circuit board (22) is foldable.

3. Sensor assembly (10) according to any of the preceding claims, wherein the secondary printed circuit (22) board is folded, at least with its section carrying the combined sensor module (24), between two opposing walls of the secondary compartment (16) of the housing (12).

4. Sensor assembly (10) according to claim 3, wherein in the mounted position, the folded secondary printed circuit board (22) is pressed against the window glass (36) with its folded section, such that the at least one temperature sensor is pressed against the window glass (36).

5. Sensor assembly (10) according to any of the preceding claims, wherein the main printed circuit board (20) and the secondary printed circuit board (22) each comprise a contact pad, wherein the electrically conductive adhesive (32) is placed at least between the contact pads.

6. Method for manufacturing a sensor assembly (10) according to any of the preceding claims, comprising the steps of- providing a housing (12) for the sensor assembly (10), comprising a main compartment (14) and a secondary compartment (16),- arranging a main printed circuit board (20) in the main compartment (14) and arranging a secondary printed circuit board (22) in the secondary compartment (16),- mechanically and electrically conductively connecting a combined sensor module (24) with at least one temperature sensor and at least one humidity sensor to a section of the secondary printed circuit board (22),- applying an electrically conductive adhesive (32) onto a surface of the main printed circuit board (20) and / or onto a surface of the secondary printed circuit board (22), and- electrically conductively connecting the main printed circuit board (20) and the secondary printed circuit board (22) to each other by pressing the surfaces against each other with the electrically conductive adhesive (32) in between.

7. Method according to claim 6, further comprising the step of- curing the electrically conductive adhesive (32) by applying a curing temperature between including 120°C and including 150°C, preferably of 130°C, especially preferably of 140°C.

8. Method according to claim 6 or 7, further comprising the step of- folding the secondary printed circuit board (22), at least with its section carrying the combined sensor module (24), between two opposing walls of the secondary compartment (16) of the housing (12).

9. Motor vehicle (34) with a sensor assembly (10) according to any of claims 1 to 5, wherein the sensor assembly (10) is mounted on a window glass (36) of the motor vehicle (34), preferably on a window glass (36) of a windshield of the motor vehicle (10), wherein in the mounted position, at least one temperature sensor of the sensor assembly (10) is designed to measure a temperature of the window glass (36) and a humidity sensor of the sensor assembly (10) is designed to measure a humidity within a passenger cabin (40) of the motor vehicle (34).

10. Motor vehicle (34) according to claim 9, further comprising a control unit (38), which is designed to receive temperature and humidity data from the sensor assembly (10) and to asses a probability of fogging of the window glass (36) based on the temperature and humidity data.

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