Method for preventing the deposition of ferromagnetic particles, system and gearbox

Abstract

Method for preventing the deposition of ferromagnetic particles (6) between an induction sensor (4) with at least one permanent magnet (8) and a sensor unit (2), characterized in that a tolerance compensation element (26), which reduces or fills a gap (12) between the induction sensor (4) and the sensor unit (2), and which consists of at least one elastic material in the form of a nonwoven material, is used to completely or partially fill a gap (12) between the sensor unit (2) and the induction sensor (4), so that no or only a few particles (6) can be deposited on the surfaces of the sensor unit (2) or the induction sensor (4).

Description

[0001] The invention relates to a method for preventing the deposition of ferromagnetic particles between an induction sensor with at least one permanent magnet and a sensor unit, as well as a system and gearbox with a corresponding system according to the preamble of claims 12 and 3.

[0002] Sensors and associated encoders are used today in a wide variety of technical applications. One such application is in manual transmissions, where gears are shifted via shift forks connected to manually, semi-automatically, or automatically operated, longitudinally movable shift rails. The sensors used include, for example, displacement sensors for detecting shift positions in these transmissions. The displacement of a shift rail, detected by an inductive displacement sensor array, is processed as a position signal in a function controller, for example, to verify whether the transmission shift was successful. Inductive displacement sensor arrays, such as those using LVDT sensor technology, are frequently employed as displacement sensors. These require an inductive encoder with at least one permanent magnet as the encoder element.

[0003] In some transmissions, the position sensors are located outside the transmission oil chamber. However, there are also transmissions where the position sensors are located inside the transmission oil chamber. In this transmission application, the permanent magnet inductive sensor can be fixed to the shift rail, and the sensor unit can be bolted to the transmission housing. This creates an air gap between the inductive sensor and the sensor unit. This air gap can vary depending on the positioning on the shift rail.

[0004] Due to abrasion, ferromagnetic chips or particles form in the transmission oil. These ferromagnetic chips or particles are attracted to the permanent magnet of the inductive position sensor, weakening the magnetic field of the permanent magnet. This can affect the position signal, resulting in inaccurate or invalid position signals.

[0005] German patent application DE 10 2009 039 447 A1 discloses a method for cleaning the surface of a liquid detection sensor, wherein the sensor is a capacitive sensor and a sensitive surface of the sensor is actively cleaned at regular intervals. This active cleaning can be achieved by relative movement of the sensitive surface with respect to a wiper element, by spraying with a liquid, or by applying a vibration to the sensor or a component rigidly connected to the sensor. For this solution using a wiper element, either the sensor itself, a wiper, or both components must be moved. Additional moving components pose an increased risk of damage. Furthermore, cleaning must be actively initiated manually or automatically from the outside. If this process is not continuously activated or initiated, the current degree of cleaning cannot be reliably determined.

[0006] Document DE 36 21 155 A1 discloses an arrangement for measuring rotational speed in which a magnetic sensor is positioned opposite a wheel having a magnetic division, wherein the surface of the sensor facing the wheel is provided with a layer of non-magnetizable material which has a contour adapted to the wheel.

[0007] Document WO 2003 / 004 973 A1 discloses an arrangement for measuring the angular position of an object with planar magnetoresistive sensors through which an electric current flows and which are arranged in a magnetic field parallel to their respective planes, which is generated by an arrangement of magnets rotatably mounted eccentrically on a shaft, wherein the angular position of the shaft corresponds to that of the object to be measured.

[0008] Document GB 2 506 698 A discloses a detector for measuring the relative position of bodies along a measuring path, comprising a first inductive target attached to a first body and arranged to face a first winding attached to a second body; a second inductive target attached to the first body and arranged to face a second winding attached to the second body; wherein the targets extend along the measuring path and their extent varies orthogonally to the measuring path, such that a comparison of the inductances of the windings indicates the relative position of the two bodies.

[0009] Document JP 2006-177676 A discloses the provision of a leaf load detector that prevents foreign materials, such as fine particles, from entering the gap between a Hall element and a magnet during displacement. In the detector, the Hall element and the magnet are used to detect the relative displacement between the two elements. A deformation-capable medium is filled into the gap between the Hall element and the magnet.

[0010] Against this background, the invention is based on the objective of creating a device and a method for preventing the deposition of ferromagnetic particles between an induction sensor with at least one permanent magnet and a sensor unit, as well as a gearbox with a corresponding device.

[0011] The solution to the problem arises from the features of independent claims 1, 6 and 7, while advantageous embodiments and further developments of the invention can be derived from the dependent claims subordinate to these claims.

[0012] The invention is based on the finding that the problem described above is best solved by proposing a device for preventing the deposition of ferromagnetic particles between an induction sensor with at least one permanent magnet and a sensor unit, wherein the device consists of at least one tolerance compensation element which reduces or fills the gap or distance between the induction sensor and the sensor unit. The tolerance compensation element is preferably made of an elastic material. This tolerance compensation element, made of an elastic, compressible, suitable material, at least partially covers the induction sensor or the permanent magnet, completely or partially fills the gap between the sensor unit and the induction sensor, and prevents the accumulation or deposition of ferromagnetic particles on the surface of the induction sensor or the permanent magnet.The permanent magnet or the sensor unit can be reduced or prevented.

[0013] An elastic material is preferably used, as the dynamics and wear of mechanical parts (e.g., in the bearings of the switching rails) lead to variable deflections over their service life. Various suitable materials can also be combined. Furthermore, different shapes for the tolerance compensation element are conceivable, or several tolerance compensation elements can be arranged directly next to each other. It is important to ensure that the material can withstand the required environmental conditions in the oil chamber. Additionally, force transmission from the induction encoder through the tolerance compensation element to the sensor unit should be largely avoided or minimized.

[0014] The tolerance compensation element, made of elastic material, can be attached directly or indirectly to the surface of a sensor unit or an induction encoder. Attachment can be achieved, for example, by bonding. Nonwoven materials are used as suitable elastic materials.

[0015] To further illustrate the invention, exemplary embodiments are included. Fig. 1 Schematic representation of an induction encoder and a sensor unit in a manual transmission Fig. 2 Schematic representation of a device according to the invention on the induction sensor in a manual transmission analogous to Fig. 1 Fig. 3 Schematic representation of a device according to the invention on the sensor unit in a manual transmission analogous to Fig. 1

[0016] In Fig. Figure 1 schematically depicts a sensor unit 2 with an induction sensor 4. The sensor unit 2 consists of a primary coil 16 surrounding a saturation rod 24, at the ends of which two secondary coils 18 are attached. Opposite this is an induction sensor 4 with a permanent magnet 8, which, when approaching the sensor unit 2, causes a local saturation, a saturation area 20, of the saturation rod 24. The position of this saturation area 20 can then be evaluated. Since there is a gap 12 between the sensor unit 2 and the induction sensor 4, various ferromagnetic particles 6 can accumulate in this gap 12, with the particles being particularly attracted by the permanent magnet 8. If such an accumulation of particles 6 is present in the gap 12, the magnetic field lines 14 are deflected or disturbed by the particle accumulation 6, resulting in position errors or even no measurable position.

[0017] Fig. 2 now shows a schematic representation of a device according to the invention on the induction sensor analogous to Fig. 1, which is intended to prevent an accumulation of ferromagnetic particles in the gap 12. For this purpose, the gap 12 is minimized or even closed by a tolerance compensation element 26. In the embodiment shown here, a tolerance compensation element 26 is therefore attached to a surface of the induction sensor 4. The gap 12 between the sensor unit 2 and the induction sensor 4 has thus been minimized. This has also minimized the accumulation of ferromagnetic particles 6 to such an extent that the magnetic field lines 14 are not affected.

[0018] To enable the tolerance compensation element 26 to be used even with variable deflection, it is preferably made of an elastic, compressible material. This also prevents excessive force transmission from the induction encoder 4 to the sensor unit 2.

[0019] Fig. Figure 3 also shows a schematic representation of a device according to the invention on the induction sensor analogous to Fig. 1, which prevents an accumulation of ferromagnetic particles in the gap 12. For this purpose, the gap 12 is also minimized by a tolerance compensation element 26. In the embodiment shown here, the tolerance compensation element 26 is attached to a surface of the sensor unit 2. The gap 12 between the sensor unit 2 and the induction sensor 4 is thereby also minimized. This also minimizes the accumulation of ferromagnetic particles 6 to such an extent that the magnetic field lines 14 are not affected.

[0020] In order to be able to use the tolerance compensation element 26 even with variable deflection, it is preferably also made of an elastic, compressible material. Reference sign 2 sensor units 4 induction sensors 6. Accumulation of ferromagnetic particles 8 permanent magnets 10 Direction of movement of the induction sensor 12 columns 14 magnetic field lines 16 primary coil 18 secondary coils 20 saturation range 22 magnetic field lines in the area of ​​particle accumulation 24 saturation bar 26 Tolerance compensation element

Claims

Method for preventing the deposition of ferromagnetic particles (6) between an induction sensor (4) with at least one permanent magnet (8) and a sensor unit (2), characterized in that a tolerance compensation element (26), which reduces or fills a gap (12) between the induction sensor (4) and the sensor unit (2), and which consists of at least one elastic material in the form of a nonwoven material, is used to completely or partially fill a gap (12) between the sensor unit (2) and the induction sensor (4), so that no or only a few particles (6) can be deposited on the surfaces of the sensor unit (2) or the induction sensor (4). System comprising an induction sensor (4) with at least one permanent magnet (8), a sensor unit (2) and a device for preventing the deposition of ferromagnetic particles (6) between the induction sensor (4) with at least one permanent magnet (8) and a sensor unit (2), wherein the device consists of at least one tolerance compensation element (26) which reduces or fills a gap (12) between the induction sensor (4) and the sensor unit (2), wherein the tolerance compensation element (26) consists of at least one elastic material in the form of a nonwoven material. Transmission with a system according to claim 2, wherein the sensor unit (2) includes at least one displacement sensor for detecting switching positions in the transmission. Gearbox according to claim 3, characterized in that the tolerance compensation element (26) is attached directly or indirectly to the sensor unit (2) or to the induction sensor (4). Gearbox according to claim 3 or 4, characterized in that the tolerance compensation element (26) is bonded to a surface of the sensor unit (2) or to a surface of the induction sensor (4).

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