Electrical coupling device for wireless signal transmission in the area of hollow machine parts

Abstract

The invention relates to an electrical coupling device for radio signal transmission in the region of a cavity (2) in an at least partially hollow mechanical part, comprising a hollow cylindrical coupling element (3) at its transmitter end which fits into the cavity (2), is connected to a sensor (5) located in or on the mechanical part and communicates via a transmission path within the cavity with a pin-type coupling element (4) at its receiver end, the pin-type coupling element (4) protruding at least partially into a hollow cylindrical part located in the cavity (2) of the coupling element (3) at the transmitter end.

Description

Technical Field

[0001] The present invention relates to an electrical coupling device for wireless signal transmission in the area of machine parts, preferably in the area of transmissions or electric motors.

Background Art

[0002] The application area of the present invention mainly extends to vehicle engineering. Especially in hybrid or electric vehicles, drive train components such as electric motors, transmissions, and transmission shafts are usually subject to sensor-based condition monitoring. For this purpose, state monitoring sensors are used in areas such as gears, bearings, couplings, etc., mainly to measure not only the temperature of the components, but also vibrations, voltages, torques, accelerations, angles, speeds, magnetic field strengths, etc., so that they can be utilized as part of a so-called condition monitoring system or as control parameters for a control process, usually by an electronic evaluation unit for external signal evaluation and / or a transmitter and / or receiver unit such as a reader.

[0003] Signal transmission between the sensor and the electronic evaluation unit can be carried out using wires in an interference-preventing manner, provided that signal transmission does not occur between components that move relative to each other, especially between rotating components. Although electrical contact rotary feed-through units exist, they are very susceptible to the effects of failures due to the mechanical sliding contact principle and require maintenance. The present invention, on the one hand, is specialized in the subject of wireless signal transmission, which can be implemented, for example, via radio, infrared, etc. In addition, the solution according to the present invention can also be used in other drive trains, such as wind turbines.

[0004] German Patent Application Publication No. 102014200639 describes a system for determining the status data of a transmission, in particular a planetary transmission, comprising at least one passive RFID sensor unit having a sensor and an RFID reader. Here, it is only generally proposed that the RFID reader be arranged in a first transmission part and the RFID sensor unit be arranged in a second transmission part movable relative to the first transmission part. This type of wireless signal transmission requires an interference-free wireless link that cannot be impaired by adjacent components or external influences.

[0005] International Publication No. 2021 / 1004568 discloses an electric drive machine, a transmission, an internal combustion engine, and combinations thereof equipped with several condition monitoring sensors for forming a sensor network. The sensors of the sensor network are preferably arranged at different positions within the machine and are each designed to measure a physical variable. For this purpose, each individual sensor is wirelessly electrically connected to an electronic evaluation unit that processes the signals received wirelessly from the sensor. When planning the arrangement of the sensors, care must also be taken to ensure that the wireless link is not interrupted.

[0006] However, in practice, it is not always possible to incorporate condition monitoring sensors into a machine in such a way that an interruption-free wireless signal transmission can be guaranteed, especially between mutually rotating machine parts and in cases where access to the machine structure is difficult, such as from a deep location. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0007] Therefore, an object of the present invention is to create an electrical coupling device for wireless signal transmission in the area of machine parts that ensures the reliable transfer of sensor signals to an external electronic evaluation unit using simple technical means. MEANS FOR SOLVING THE PROBLEM

[0008] This object is achieved by the electrical coupling device according to claim 1. Claim 10 designates a transmission or an electric motor having the electrical coupling device according to the invention as a preferred application. The dependent claims relate to further advantageous developments of the invention.

[0009] The invention provides an electrical coupling device for wireless signal transmission in the region of a cavity of a machine part that is at least partially hollow. The coupling device is fitted into the cavity, connected to a sensor arranged within or on the machine part, and communicates with a pin-shaped coupling element at the receiver end that projects at least partially into a hollow cylindrical part, which is arranged within the cavity of the coupling element at the transmitter end via a transmission path, in particular an air path or oil as a dielectric. In this context, the solution according to the invention also includes the exchange of the transmitter end and the receiver end. Preferably, the sensor emits a signal that is transmitted via the coupling element to a transmitter / receiver unit / evaluation unit.

[0010] In other words, the solution according to the invention thus refers to an electrical coupling configuration for wireless signal transmission in which the signal is transmitted inside a machine part that is at least partially hollow. In this context, the sensor signals of several sensors arranged on the machine part can be acquired via a coupling element that projects into the cavity. It is also possible to connect several sensors to one coupling element. The solution according to the invention is thus particularly suitable for acquiring sensor signals on a rotating component.

[0011] Thus, in a particularly advantageous manner, the solution according to the invention can be used, for example, for the wireless detection of the rotor temperature of a traction motor. If the temperature in the rotor is too high, the magnets are demagnetized, and thus the electric motor is damaged. For this reason, hitherto, more expensive magnetic materials have been used to counteract such a demagnetization tendency.

[0012] However, when using the solution according to the present invention, the temperature can be directly measured with a magnet, and the maximum allowable temperature can be accurately controlled. Another advantage regarding the determination of the rotor temperature is that the torque of the electric motor can be calculated. The torque of an electric motor is usually determined by a characteristic diagram where the rotor temperature is an important influencing variable. The torque can be calculated more accurately based on the rotor temperature, which can be measured with a wireless temperature sensor. It is also possible to monitor the temperature of temperature-critical transmission components, especially the bearings, and cool them if necessary. As a result, this also reduces the oil requirements and, consequently, the scattering losses usually associated with pressure oil lubrication.

[0013] The solution according to the present invention enables, for example, by implementing a sensor network, integrating a large number of temperature sensors at any point of an electric motor or transmission with little effort, detecting their measured values via a central electronic evaluation unit, and processing them in an application-specific manner. This makes it possible to achieve optimal system control.

[0014] According to a preferred embodiment of the present invention, the hollow cylindrical coupling element at the transmitter end is designed to be tubular or sleeve-shaped. This element can be pre-manufactured and inserted into a preferably cylindrical cavity of a mechanical part having an inner wall contact portion, and attached thereto, for example, by adhesion. It should be noted that an insulating layer is required between the preferably metal, for example, copper-made hollow cylindrical coupling element and the inner wall of the mechanical part made of a conductive material, which is usually preferably steel, and this can be made of, for example, a non-conductive plastic. The insulating layer can be part of the pre-manufactured tubular or sleeve-shaped coupling element, or designed as a separate sleeve-shaped element and, for example, form its outer surface. Thereby, the hollow cylindrical coupling element can be fixed in the cavity of the hollow mechanical part by an adhesive connection or similar means. In addition to such a materially adhered connection, for example, a force-fit connection by press fitting is also conceivable.

[0015] According to a further embodiment of the hollow cylindrical coupling element at the sensor end, it can also be designed as a film or coating. In the case of a film, an electrically insulating layer is applied on the outside. The cavity of the mechanical part can be easily lined with such a multilayer film, and adhesive fixation is recommended. In addition, it is also conceivable to first coat the cylindrical cavity of the mechanical part with an electrically insulating layer, for example, plastic, and then apply a conductive layer, for example, made of metal. This can be achieved, for example, by evaporation in a vacuum.

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

[0017] According to a further means of improving the present invention, it is proposed that the hollow cylindrical coupling element at the transmitter end is arranged coaxially with the pin-type coupling element at the receiver end. This makes it possible to achieve particularly high signal quality, and the pin-type coupling element at the receiver end is arranged in a particularly well-protected manner within the cavity structure of the mechanical part. This applies to both mechanical considerations regarding interference signals and wireless communication.

[0018] For this purpose, it is further proposed that the hollow cylindrical coupling element at the transmitter end protrudes forward beyond the distal end of the pin-type coupling element at the receiver end. Preferably, in the automotive applications of particular interest here, the pin-type coupling element should be 5 to 10 mm shorter than the hollow cylindrical coupling element.

[0019] In order to further improve signal transmission, it is proposed to make the length of the hollow cylindrical coupling element at the transmitter end and / or the pin-type coupling element at the receiver end a multiple of the wavelength of the operating frequency of the wireless signal transmission. This value can be selected, for example, according to 1 / 4, 1 / 2, or 3 / 4 of the wavelength.

[0020] The pin-type coupling element at the receiver end can be designed, for example, as a rod, tube, sleeve, or spiral, and a non-conductive coating can be provided, for example, to avoid direct electrical contact with the hollow cylindrical coupling element at the transmitter end as a result of unintentional deformation. When the coupling element is in the form of a tube or sleeve, it can be placed on a component connected to the housing. If the housing connection component is made of a metallic material, an insulating layer should be provided on the inner surface of the tubular or sleeve-shaped coupling element. The insulating layer may be part of a pre-manufactured tubular or sleeve-shaped coupling element, or it can be designed as a separate sleeve-shaped element and, for example, form its inner surface.

[0021] According to a further means for improving the present invention, it is proposed that non-magnetic and / or non-electric bearing elements can be provided at the receiver end to surround the pin-type coupling element, support it with respect to the hollow cylindrical coupling element, and protect it from unintentional deformation. For this purpose, a simple plastic disk adhered to the outer edge of the hollow cylindrical coupling element and from whose central opening the pin-type coupling element protrudes is sufficient.

[0022] Wireless signal transmission can be based on SAW or RFID technology as part of the solution according to the present invention. The ISM bands of 13.5 MHz, 433 MHz, 868 MHz, 2.4 GHz or 5 GHz, or other standard wireless bands, for example, the SDR band, are preferably used as the operating frequency.

[0023] According to a preferred application form, the at least partially hollow mechanical component is a hollow shaft or a drive shaft of a gear pair in the drive train of an automobile or a wind turbine. In this regard, the solution according to the present invention utilizes the cavity structure of this mechanical component, which is mainly used for oil feed-through, to create a mechanically protected and highly reliable sensor connection with respect to signal transmission.

[0024] Preferably, the mechanical component is rotatably mounted and the coupling element at the reader end is mounted on the fixed housing. To supply power to the active sensor, an energy harvesting module or the like can be provided. If the coupling element at the reader end is very thin and long, it can be strengthened or additionally held. This can be arranged inside or outside the housing.

[0025] An electrical isolation layer or sleeve on the coupling element at the receiver end or transmitter end is also advantageous. The dielectric, air or oil, especially the dielectric constant between the coupling elements, is related to the length of the coupling element. The insulating layer between the coupling element at the transmitter end and the mechanical component, or between the coupling element at the receiver end and the component fixed to the housing, can also be a dielectric. The dielectric constant of this dielectric, or especially the insulating layer, can also be related to the length of the coupling element.

[0026] Further measures for improving the present invention are illustrated below together with the description of two preferred exemplary embodiments of the present invention using figures.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

[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 received and which interacts with a pin-type coupling element 4 via air as a dielectric to form a wireless signal transmission path.

[0029] A sensor 5 for detecting the component temperature is disposed in the gear region outside the hollow shaft 1 and is electrically connected to the hollow cylindrical coupling element 3 at the transmitter end via a plastic layer 6 functioning as a dielectric. Most of the pin-type coupling element 4 communicating with the pin-type coupling element 4 at the receiver end projects into the hollow cylindrical portion of the coupling element 3 at the transmitter end disposed in the cavity 2. In this regard, the hollow cylindrical coupling element 3 at the transmitter end projects forward beyond the distal end of the pin-type coupling element 4 at the receiver end by a length a. The pin-type coupling element 4 is disposed coaxially with the hollow cylindrical coupling element 3.

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

[0031] According to FIG. 2, the hollow cylindrical coupling element 3' at the transmitter end is designed as a film provided with an electrically insulating plastic coating on its outer surface. In addition, the sensor 5 is housed in an insulating sensor protection cover 7, and via this protection cover 7, the sensor 5 is pressed into the corresponding hole of the mechanical component. Otherwise, this exemplary embodiment corresponds to the exemplary embodiment described above.

[0032] In FIG. 3, in contrast to the exemplary embodiment described first, since the pin-type coupling element 4' at the receiver end is designed in the form of a tube, this pin-type coupling element 4' is provided with hollow waveguide characteristics for improved signal transmission. Otherwise, this exemplary embodiment also corresponds to the exemplary embodiment described first.

[0033] According to FIG. 4, the bearing element 8 is arranged in the intermediate region between the pin-type coupling element 4 and the hollow cylindrical coupling element 3 coaxially surrounding it. The bearing element 8 is made of a non-magnetic and non-electric plastic and serves to support the pin-type coupling element 4, which, in this exemplary embodiment, is very thin in order to secure the desired position even when the hollow shaft 1 is rotating at high speed. Otherwise, this exemplary embodiment also corresponds to the exemplary embodiment described first.

[0034] The present invention is not limited to the preferred exemplary embodiments described in more detail above. Rather, departures therefrom that are within the scope of protection of the following claims are also conceivable. For example, instead of the hollow shaft, it is also possible to use the cavity of another at least partially hollow machine part to accommodate the electrical coupling device according to the present invention.

Explanation of Reference Numerals

[0035] 1 Hollow shaft 2 Cavity 3 Hollow cylindrical coupling element 4 Pin-type coupling element 5 Sensor 6 Dielectric 7 Sensor protection cover 8 Bearing element a Recess length

Claims

1. An electrical coupling device for wireless signal transmission in the region of a cavity (2) within a machine part that is at least partially hollow, comprising a hollow cylindrical coupling element (3) at the transmitter end that is fitted within the cavity (2), connected to at least one sensor (5) disposed within or on the machine part, and communicating with a pin-type coupling element (4) at the receiver end via a transmission path within the cavity, wherein the pin-type coupling element is in the form of a rod made of a conductive material or a tube having hollow waveguide characteristics, and at the transmitter end, at least partially projects into the hollow cylindrical portion of the coupling element (3) disposed within the cavity (2), the electrical coupling device.

2. The electrical coupling device according to claim 1, characterized in that the coupling element (3) at the transmitter end is designed to be tubular or sleeve-shaped.

3. The electrical coupling device according to claim 1, characterized in that the coupling element (3) at the transmitter end is designed as a film or coating.

4. The electrical coupling device according to claim 1, characterized in that the coupling element (3) at the transmitter end is arranged coaxially with the pin-type coupling element (4) at the receiver end.

5. The electrical coupling device according to claim 1, characterized in that the coupling element (3) at the transmitter end projects forward beyond the distal end of the coupling element (4) at the receiver end.

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

7. The electrical coupling device according to claim 1, characterized in that the pin-type coupling element (4) at the receiver end is supported or electrically isolated from the machine part by at least one non-magnetic and / or non-electric bearing element (8).

8. The electric coupling device according to claim 1, characterized in that the machine part having the cavity (2) is designed as a hollow shaft (1) of a drive train of an automobile or a wind turbine.

9. A transmission and / or an electric motor of a hybrid vehicle or an electric vehicle, having the electric coupling device for wireless signal transmission in the region of the cavity (2) in a machine part that is at least partially hollow, according to any one of claims 1 to 8.

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