Proximity sensor

[0002] This application is a continuation of copending International Application No. PCT/EP01/01865, filed Feb. 20, 2001, which designated the United States and was not published in English.

[0003] Field of the Invention

[0004] The invention relates to a proximity sensor with a sensor head for generating sensor signals and to a modular system for forming proximity sensors.

[0005] A proximity sensor is known, for example, from Published, Non-Prosecuted German Patent Application DE 33 18 900 A1. In the case of the known proximity sensor, a mini-transmitter that passes on the sensor signal wirelessly to another unit is already used.

[0006] It is generally known to produce proximity sensors with different outer forms, for example with a cylindrical housing of a diameter of 4, 6, 8, 12, 18 and 30 mm or else with a cuboidal housing (see in this respect, for example, ABB catalogue No. 1SAC103699L0201, printed 6/99, pages VI and VII). The outer form of the housing corresponds to the fastening openings to be provided in machine components. In the case of cylindrical housings, the housing diameter is often chosen in accordance with the sensor spacing. In this case, it is difficult, in particular in the case of very small diameters of the housing, to accommodate not only the sensor head with the sensor coil and a sensor-signal evaluation unit but also additional electronic units, such as a radio transmitter, radio receiver and antenna, within the housing.

[0007] It is accordingly an object of the invention to provide a proximity sensor which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type, which can be adapted in a simple way to differently dimensioned fastening openings.

[0008] With the foregoing and other objects in view there is provided, in accordance with the invention, a proximity sensor. The proximity sensor includes a fastening portion containing a sensor head for generating sensor signals, and an electronics portion connectable to the fastening portion. The electronics portion has a sensor-signal evaluation unit, a modulator/encoder, a radio transmitter with an antenna for emitting evaluated sensor signals and disposed downstream of the modulator/encoder, a radio receiver, a demodulator/decoder for a radio reception of sets of parameters and disposed downstream of the radio receiver, and a power supply unit. An electrical connection is provided for passing the sensor signals from the fastening portion to the electronics portion.

[0009] The advantages that can be achieved with the invention are, in particular, that the electronics portion of the proximity sensor, formed as an independent structural component, can be used universally for all variants of the fastening portions, formed as independent structural components (with different housing diameters or different housing configurations). The electronics of the proximity sensor, including the sensor-signal evaluation unit, radio transmitter, antenna and cableless power supply, does not have to be miniaturized in such a way that it also fits in fastening portions with extremely small dimensions (see, for example, proximity sensors with a cylindrical housing of 4 or 6 mm in diameter). The modular system makes it possible for proximity sensors to be produced at low cost with different fastening portions, respectively adapted to the fastening openings of machine components, it being possible in each case for the same electronics portions to be used for different fastening portions.

[0010] In accordance with an added feature of the invention, the power supply unit contains a secondary coil, a rectifier disposed downstream of the secondary coil, and a store. The secondary coil receives a medium-frequency magnetic field and performs a conversion of the medium-frequency magnetic field into electrical energy.

[0011] In accordance with an additional feature of the invention, the fastening portion has a thread suitable for engagement in a machine component.

[0012] In accordance with another feature of the invention, the electrical connection between the fastening portion and the electronics portion includes plug contacts. Alternatively, the electrical connection takes place by magnetic coupling.

[0013] In accordance with a further feature of the invention, the electrical connection includes an intermediate piece connected between the fastening portion and the electronics portion. Preferably, the intermediate piece is deformable.

[0014] In accordance with another added feature of the invention, the sensor-signal evaluation unit adaptively recognizes a connection of the sensor head for evaluating the sensor signals.

[0015] In accordance with a concomitant feature of the invention, the electrical connection between the fastening portion and the electronics portion takes place contactlessly or with electrical contacts.

[0016] Other features which are considered as characteristic for the invention are set forth in the appended claims.

[0017] Although the invention is illustrated and described herein as embodied in a proximity sensor, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

[0018] The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

[0019] FIGS. 1A and 1B are diagrammatic, perspective views of a first embodiment of a pluggable proximity sensor according to the invention;

[0020] FIG. 2 is a perspective view of a second embodiment of the pluggable proximity sensor;

[0021] FIG. 3 is a perspective view of a third embodiment of the pluggable proximity sensor; and

[0022] FIG. 4 is a block diagram of a power supply unit.

[0023] Referring now to the figures of the drawing in detail and first, particularly, to FIGS. 1A and 1B thereof, there is shown a first embodiment of a pluggable proximity sensor. The proximity sensor is made up of two structural components that can be connected to each other, to be specific a fastening portion 1 and an electronics portion 2. The cylindrical fastening portion 1, preferably formed of metal, serves for fastening a sensor head 6 which detects a sensor environment, in a bore or generally a fastening opening of a machine component and, for this purpose, is preferably provided with a thread 5. The fastening portion 1 in the case of an inductive proximity sensor contains a sensor coil and, if appropriate, a resonant capacitor.

[0024] The electronics portion 2, preferably provided with a plastic housing, contains a sensor-signal evaluation unit 7, required for the evaluation of a sensor signal, a modulator/encoder 8, required for the conversion of an evaluated sensor signal, and a transmitter 9 with an antenna 13 (generally a device for radio transmission to a remote device), serving for the emission of radio signals. The electronics portion 2 expediently contains in addition a radio receiver 10 for receiving sets of parameters (sensor switching thresholds, switching hystereses, correction factors for different materials to be identified, prescribed distance ranges between the sensor and an object to be identified) and a downstream demodulator/decoder 11 for conditioning the received signal, storing it and feeding it to the sensor-signal evaluation unit 7. Furthermore, the electronics portion 2 contains a power supply unit 12 required for cableless power feeding and supply.

[0025] The power supply unit 12 preferably contains a secondary coil 20, a downstream rectifier 21 and a store 22, for example a capacitor 22 for energy storage (FIG. 4). The power supplied to the rest of the proximity sensor from the power supply unit 12 preferably takes place in a pulsed manner with a prescribed on period and a prescribed off period, which has the advantage of optimizing or reducing the energy requirement. A base station, corresponding to the proximity sensor, expediently contains an oscillator, which feeds a primary coil with a medium-frequency oscillation in the range from approximately 15 kHz to 15 MHz, whereby a magnetic field is generated. The secondary coil of the power supply unit 12 receives the medium-frequency magnetic field and performs the conversion from magnetic energy into electrical energy.

[0026] The specified medium frequency would lead to the emission of electromagnetic fields of wavelengths greater than 22 m to 22 km, and consequently greater than the dimension of the primary winding used, so that the primary winding does not act as an antenna for such electromagnetic radiation on account of its dimensions.

[0027] In FIG. 2, a second embodiment of the pluggable proximity sensor is represented. The proximity sensor shown is constructed in principle in the same way as the first embodiment, explained above under FIG. 1, but a fastening portion 3 used has a greater diameter than the fastening portion 1 according to FIG. 1. The example is intended to show that all the required fastening portions can be realized with cylindrical housings of different diameters or with housings of different forms and can be connected in a simple way to the universal electronics portion 2.

[0028] The electrical connection between the two structural components of the proximity sensor, the fastening portion 1 or 3 and the electronics portion 2, preferably takes place by electrical wiring 16 and plug contacts 14, but may also take place contactlessly by magnetic coupling 15, which has the advantage of greater reliability. The sensor-signal evaluation unit 7 can adaptively recognize the connected sensor head 6 and evaluate the transmitted sensor signals accordingly. For the adaptation of the sensor-signal evaluation unit 7 to the connected sensor head 6, additional contacts are provided, for example, for the connection of the two structural components, the fastening portion 1 or 3 and the electronics portion 2.

[0029] When there is restricted installation space, an intermediate piece 4 may be additionally inserted between the fastening portion 1 or 3 and the electronics portion 2, as a third embodiment of a pluggable proximity sensor shown in FIG. 3. In the case of this embodiment, the proximity sensor is accordingly made up of three structural components that can be connected to one another. The electrical connections preferably take place by plug contacts. The intermediate piece 4 is expediently deformable, so that an exact adaptation to the available installation space is possible.

[0030] The invention can also be used in particular in the case of an industrial robot, an automatic production machine, an automatic manufacturing machine or an automation system which has a multiplicity of proximity sensors/proximity switches (system) with different fastening openings, a radio transmission being provided between the individual proximity sensors and a central station with a connected process computer for the transmission of the sensor signals and, if appropriate, for the transmission of sets of parameters.