ELECTRICAL COUPLING ARRANGEMENT FOR WIRELESS SIGNAL TRANSMISSION IN THE AREA OF A HOLLOW MACHINE ELEMENT

Description

[0001] The present invention relates to an electrical coupling arrangement for wireless signal transmission in the area of machine elements, preferably a gearbox or electric motor.

[0002] The field of application of the invention extends primarily to automotive engineering. Particularly in hybrid or electric vehicles, drivetrain components such as electric motors, transmissions, and transmission shafts are typically subjected to sensor-based condition monitoring. For this purpose, condition-monitoring sensors are used in the area of gears, bearings, clutches, and the like. These sensors primarily measure component temperature, but also vibrations, voltages, torques, accelerations, angles, rotational speeds, magnetic field strengths, and the like. These sensors then make these values available to a usually external electronic evaluation unit for signal evaluation and / or a transmitting and / or receiving unit, e.g., a reader, for example, within the framework of a so-called condition monitoring system or as control parameters for control processes.

[0003] The signal transmission between the sensors and the electronic evaluation unit can be realized via a fail-safe wired connection, provided the signal transmission does not take place between components that are moving relative to one another, especially rotating ones. While electrical contact-based rotary feedthrough units exist, these are quite susceptible to failure and require maintenance due to the mechanical sliding contact principle. The present invention, however, is dedicated to the topic of wireless signal transmission, which can be realized, for example, via radio, infrared, or the like. The solution according to the invention can also be used in other drive trains, for example, in wind turbines. State of the art

[0004] DE 10 2014 200 639 A1 discloses a system for determining status data of a transmission, in particular a planetary transmission, comprising at least one passive RFID sensor unit with a sensor and an RFID reader. It is only generally proposed that the RFID reader be arranged on a first transmission part and the RFID sensor unit be arranged on a second transmission part, which is movable relative to the first transmission part. Such wireless signal transmission requires an interference-free radio link that cannot be impaired by adjacent components or external influences.

[0005] WO 2021 1004568 A1 discloses an electric drive motor, transmission, combustion engine, and combinations thereof, which are equipped with several condition-monitoring sensors to form a sensor network. The sensors of the sensor network are preferably arranged at different positions in the machine and are each intended to measure a physical quantity. For this purpose, the individual sensors are each electrically connected wirelessly to an electronic evaluation unit, which processes the wirelessly received signals from the sensors. When designing the arrangement of the sensors, uninterrupted radio links must also be ensured. Other prior art electrical coupling arrangements are known from documents DE102013100979, DE1020141121116, DE102004018370, and DE3044734.

[0006] In practice, however, it is not always possible to integrate the condition-monitoring sensors into the machine in such a way that uninterrupted wireless signal transmission can be guaranteed, especially between machine elements rotating relative to one another and from deep, difficult-to-access machine structures.

[0007] It is therefore the object of the present invention to provide an electronic coupling arrangement for wireless signal transmission in the area of machine elements, which ensures reliable transmission of sensor signals to an external electronic evaluation unit using simple technical means. Brief description of the invention

[0008] This object is achieved by an electrical coupling arrangement according to claim 1. Claim 10 specifies, as a preferred application, a transmission or an electric motor with an electrical coupling arrangement according to the invention. The dependent claims are directed to advantageous developments of the invention.

[0009] The invention includes the technical teaching that an electrical coupling arrangement for wireless signal transmission in the region of a cavity of an at least partially hollow machine element comprises a transmitter-side hollow-cylindrical coupling element connected to a sensor arranged in or on the machine element, which is fitted into the cavity, and which corresponds via a transmission path, in particular an air path or oil as a dielectric, to a receiver-side pin-shaped coupling element which projects at least partially into the hollow-cylindrical region of the transmitter-side coupling element arranged in the cavity. The inventive solution also involves an exchange of transmitter and receiver sides. The sensor preferably transmits a signal which is transmitted via the coupling elements to the transmitting / receiving unit / evaluation unit.

[0010] In other words, the inventive solution relates to an electrical coupling arrangement for wireless signal transmission, in which the signal is transmitted inside an at least partially hollow machine element. The sensor signals from multiple sensors arranged on the machine element can be detected via a coupling element extending into the cavity. Likewise, multiple sensors can be connected to one coupling element. Thus, the inventive solution is particularly suitable for detecting sensor signals on rotating components.

[0011] The solution according to the invention can thus be used particularly advantageously for wirelessly detecting, for example, the rotor temperatures of a traction motor. Excessively high temperatures in the rotor lead to demagnetization of the magnets, thus damaging the electric motor. For this reason, a more complex and expensive magnetic material has been used to counteract this tendency toward demagnetization.

[0012] However, with the solution according to the invention, the temperature can be measured directly at the magnets and the maximum permissible temperature can be precisely controlled. A further benefit of determining the rotor temperature is the calculation of the torque of the electric motor. The torque of the electric motor is usually determined using characteristic maps in which the rotor temperature is an important influencing factor. The rotor temperature, which can be measured using a wireless temperature sensor, allows the torque to be calculated more precisely. Furthermore, it is possible to monitor the temperature of temperature-critical transmission components, especially bearings, and to cool them as needed. This consequently reduces the oil requirement and thus also the churning losses usually associated with pressure oil lubrication.

[0013] The solution according to the invention makes it possible, for example, to implement a sensor network and integrate numerous temperature sensors at any location on an electric motor or transmission with minimal effort. Their measured values can be recorded and processed in an application-specific manner via a central electronic evaluation unit. This enables optimal system control.

[0014] According to a preferred embodiment of the invention, the transmitter-side hollow-cylindrical coupling element is tubular or sleeve-shaped. This can be prefabricated and inserted into the likewise preferably cylindrical cavity of the machine element with inner wall contact and fastened thereto, for example by gluing. It should be noted that an insulating layer is required between the hollow-cylindrical coupling element, which is preferably made of a metal, for example copper, and the inner wall of the machine element, which is usually also made of an electrically conductive material, preferably steel. This insulating layer can be made, for example, of an electrically non-conductive plastic. The insulating layer can be a component of the prefabricated tubular or sleeve-shaped coupling element or can also be designed as a separate sleeve-shaped element and thus form, for example, its outer surface.This allows the hollow cylindrical coupling element to be secured in the cavity of the hollow machine element using an adhesive connection or similar method. In addition to such a material connection, a force-fit connection, for example, by press-fitting, is also conceivable.

[0015] According to a further embodiment of the sensor-side hollow-cylindrical coupling element, this can also be designed as a film or coating. In the case of a film, this has an electrical insulation layer applied to the outside. With such a multilayer film, the cavity of the machine element can be easily lined; adhesive attachment is recommended. It is also conceivable to first coat a cylindrical cavity of the machine element with an electrical insulation layer, for example, a plastic, upon which an electrically conductive layer, for example, made of a metal, is applied. This can be done, for example, by vacuum vapor deposition.

[0016] In addition, it is also conceivable to form the hollow cylindrical coupling element from a printed circuit board material, in particular as a flexible printed circuit board or a printed circuit board consisting of several segments would be suitable for this purpose.

[0017] According to a further measure improving the invention, it is proposed that the hollow cylindrical coupling element on the transmitter side be arranged coaxially with the pin-shaped coupling element on the receiver side. This allows for particularly high signal quality, and the pin-shaped coupling element on the receiver side is arranged in a particularly protected manner within the hollow structure of the machine element. This applies both mechanically and radio-technically with regard to interference signals.

[0018] For this purpose, it is further proposed that the hollow cylindrical coupling element on the transmitter side protrude beyond the distal end of the pin-shaped coupling element on the receiver side. For the automotive applications of particular interest here, the pin-shaped coupling element should preferably be 5 to 10 mm shorter than the hollow cylindrical coupling element.

[0019] To further improve signal transmission, it is proposed that the length of the hollow cylindrical coupling element on the transmitter side and / or the pin-shaped coupling element on the receiver side be a multiple of the wavelength of the operating frequency of the wireless signal transmission. For this purpose, the length can be dimensioned according to, for example, one-quarter, half, or three-quarters of the wavelength.

[0020] The pin-shaped coupling element on the receiving side can be designed, for example, as a rod, tube or sleeve and can be provided with an electrically non-conductive coating in order to avoid direct electrical contact with the hollow cylindrical coupling element on the transmitting side, for example as a result of unwanted deformation.

[0021] If the coupling element is tubular or sleeve-shaped, it can be arranged on a component connected to the housing. If the component connected to the housing is made of a metallic material, the inner surface of the tubular-sleeve-shaped coupling element should be provided with an insulating layer. The insulating layer can be part of the prefabricated tubular or sleeve-shaped coupling element or can also be designed as a separate sleeve-shaped element, thus forming, for example, its inner surface.

[0022] According to a further measure improving the invention, it is proposed that, to protect the receiver-side pin-shaped coupling element from unwanted deformation, a non-magnetic and / or non-electrical bearing element can be provided surrounding it and supporting it against the hollow-cylindrical coupling element. A simple plastic disc, glued into the outer edge of the hollow-cylindrical coupling element and with the pin-shaped coupling element protruding through its central opening, is sufficient for this purpose.

[0023] Within the scope of the inventive solution, wireless signal transmission can be based on SAW or RFID technology. The operating frequencies are preferably the ISM bands 13.5 MHz, 433 MHz, 868 MHz, 2.4 GHz, or 5 GHz, or other standard radio bands, such as the SDR band.

[0024] According to a preferred embodiment, the at least partially hollow machine element is a hollow shaft of a gear pair or a drive shaft within the drive train of a motor vehicle or a wind turbine. The solution according to the invention utilizes the hollow structure of this machine element, which is primarily used for an oil feedthrough, to create a mechanically protected and signal-transmittingly reliable sensor connection.

[0025] Preferably, the machine element is rotatably mounted, and the reader-side coupling element is attached to the stationary housing. An energy harvesting module or similar device can be provided to supply power to the active sensor. If the reader-side coupling element is very thin and long, it can be stiffened or additionally supported. It can be arranged inside or outside the housing.

[0026] An electrically decoupling layer or sleeve on the transmitting or receiving-side coupling element is also advantageous. The dielectric, air or oil, and in particular the dielectric constant between the coupling elements, is related to the length of the coupling element. Likewise, the insulation layer between the transmitting-side coupling element and the machine component, or between the receiving-side coupling element and the component fixed to the housing, can be a dielectric. This dielectric, or in particular the dielectric constant of the insulation layer, can also be related to the length of the coupling element. Detailed description based on drawing

[0027] Further measures improving the invention are described in more detail below, together with the description of preferred embodiments of the invention, with reference to the figures. It shows: Fig. 1 shows a schematic longitudinal section through a gear pair arranged on a hollow shaft with a sensor for temperature detection, which is connected via an electrical coupling arrangement according to a first exemplary embodiment of the invention, Fig. 2 shows a schematic longitudinal section through a gear pair arranged on a hollow shaft with a sensor for temperature detection, which is connected via an electrical coupling arrangement according to a second exemplary embodiment of the invention, Fig. 3 shows a schematic longitudinal section through a gear pair arranged on a hollow shaft with a sensor for temperature detection, which is connected via an electrical coupling arrangement according to a third exemplary embodiment of the invention, and Fig.4 shows a schematic longitudinal section through a gear pair arranged on a hollow shaft with a sensor for temperature detection, which is connected via an electrical coupling arrangement according to a fourth embodiment of the invention.

[0028] According to Fig. 1 A hollow shaft 1 carrying a gear pair forms a cavity 2 in which a hollow cylindrical coupling element 3 is accommodated and which interacts with a pin-shaped coupling element 4 via air as a dielectric to form a wireless signal transmission path.

[0029] In the gear area outside the hollow shaft 1, a sensor 5 for detecting the component temperature is arranged. This sensor is electrically connected to the hollow-cylindrical coupling element 3 on the transmitter side via a plastic layer 6 acting as a dielectric. The pin-shaped coupling element 4 corresponding to this on the receiver side projects largely into the hollow-cylindrical region of the transmitter-side coupling element 3 arranged in the cavity 2. The hollow-cylindrical coupling element 3 on the transmitter side protrudes by a length a beyond the distal end of the pin-shaped coupling element 4 on the receiver side. The pin-shaped coupling element 4 is arranged coaxially to the hollow-cylindrical coupling element 3.

[0030] In this embodiment, the pin-shaped coupling element 4 is designed as a rod made of an electrically conductive material.

[0031] After Fig. 2The hollow cylindrical coupling element 3' on the transmitter side is designed in the form of a foil, which is provided with an electrically insulating plastic coating on the outer surface. Additionally, the sensor 5 is housed in an insulating sensor protective cover 7, through which the sensor 5 is pressed into a corresponding bore in the machine element. Otherwise, this embodiment corresponds to the embodiment described above.

[0032] At the Fig. 3 In contrast to the embodiment described above, the pin-shaped coupling element 4' on the receiver side is designed in the form of a tube, giving this pin-shaped coupling element 4' a hollow waveguide characteristic for improved signal transmission. Otherwise, this embodiment also corresponds to the embodiment described above.

[0033] According to Fig. 4A bearing element 8 is arranged in the intermediate region between the pin-shaped coupling element 4 and the hollow-cylindrical coupling element 3 coaxially surrounding it. The bearing element 8 consists of a non-magnetic and non-electrical plastic and serves to support the pin-shaped coupling element 4, which is quite thin in this embodiment, to ensure its desired position, even when the hollow shaft 1 is rotating rapidly. Otherwise, this embodiment also corresponds to the embodiment described above.

[0034] The invention is not limited to the preferred embodiments described in more detail above. For example, it is also possible to use a cavity of another at least partially hollow machine element to accommodate the electrical coupling arrangement according to the invention instead of a hollow shaft. List of reference symbols

[0035] 1Hollow shaft 2Cavity 3Hollow cylindrical coupling element 4Pin-shaped coupling element 5Sensor 6Dielectric 7Sensor protective cover 8Bearing element arecessed length

Claims

1. An electric coupling arrangement for wireless signal transmission in the area of a cavity (2) of an at least partially hollow machine part, comprising a transmitter-side hollow-cylindrical coupling element (3), which is connected to at least one sensor (5) arranged in or on the machine part and which is fitted in the cavity (2), and which corresponds to a receiver-side pin-shaped coupling element (4) via a transmission path within the cavity, characterized in that the pin-shaped coupling element projects at least partially into the hollow-cylindrical area of the transmitter-side coupling element (3) arranged in the cavity (2).

2. The electric coupling arrangement according to claim 1, characterized in that the transmitter-side coupling element (3) is tubular or sleeve-shaped.

3. The electric coupling arrangement according to claim 1, characterized in that the transmitter-side coupling element (3) is a film or coating.

4. The electric coupling arrangement according to claim 1, characterized in that the transmitter-side coupling element (3) is arranged coaxially to the receiver-side pin-shaped coupling element (4).

5. The electric coupling arrangement according to claim 1, characterized in that the transmitter-side coupling element (3) projects at the end face beyond a distal end of the receiver-side coupling element (4).

6. The electric coupling arrangement according to claim 1, characterized in that the length of the transmitter-side hollow-cylindrical coupling element (3) and / or the receiver-side pin-shaped coupling element (4) is a multiple of the wavelength of the operating frequency of the signal transmission.

7. The electric coupling arrangement according to claim 1, characterized in that the receiver-side pin-shaped coupling element (4) is configured as a rod, tube, or sleeve.

8. The electric coupling arrangement according to claim 1, characterized in that the receiver-side pin-shaped coupling element (4) is supported or electrically decoupled with respect to the machine part by at least one non-magnetic and / or non-electric bearing element (8).

9. The electric coupling arrangement according to claim 1, characterized in that the machine part having the cavity (2) is configured as a hollow shaft (1) in a drive train of a motor vehicle or a wind energy plant.

10. A transmission and / or electric motor of a hybrid or electric vehicle having an electric coupling arrangement for wireless signal transmission in the area of a cavity (2) in an at least partially hollow machine part according to one of the preceding claims.