The present invention relates to an inductive rotational speed sensor and to a method for producing the same. The present invention relates in particular to overmolding of coil bodies, utilizable for an axial inductive rotational speed sensor as well as for a radial inductive speed sensor.
Passive rotational speed sensors are utilized in the automotive industry, in particular in trucks, to measure the rotational speeds of rotatable components. A rotating speed of the respective road wheel has to be continuously determined for the correct functioning of anti-blocking systems, for example. These rotational speed sensors often are based on inductively measuring a rotational speed of a pole wheel in relation to a coil. As this is possible in a non-contacting manner, and the magnetic field moreover can readily penetrate a hermetic seal, such sensors are very robust in relation to environmental influences as they are typical in vehicle applications.
These rotational speed sensors can be produced as radial or axial sensors. In the case of axial rotational sensors, the electrical connecting line is routed axially away from the rotational speed sensor, that is to say parallel to an axial axis about which the windings of the coil run. In the case of radial rotational speed sensors, the electrical connecting line runs out of the rotational speed sensor in the radial direction (perpendicularly to the axial axis).
In the case of conventional rotational speed sensors, specific coil bodies and/or conductor rails are used for the radial and the axial rotational speed sensor, respectively, and correspondingly protected by overmolding. To this end, said coil bodies and/or conductor rails are fixed in a corresponding overmolding tool so as to prevent any twisting during the overmolding, for example. This fixing takes place, for example, by firmly holding a pole core of the coil body, the former being correspondingly shortened after the overmolding process. This procedure is complex and prone to errors because a reliable anti-twist protection by way of the pole core cannot always be guaranteed. Moreover, the shortening of the pole core is an additional operative step.
There is therefore demand for an inductive sensor which can be produced in a simplified manner.
At least part of the above-mentioned issues are solved by an inductive rotational speed sensor according to the description herein, and by a method for producing the same, according to the description herein. The further descriptions herein define further advantageous embodiments of the subject matter of the main descriptions herein.
The present invention relates to an inductive rotational speed sensor. The rotational speed sensor comprises a coil body having a coil and connecting lines which in terms of the coil windings run axially or radially away from the coil body, and a casing which is of a plastics material (for example an overmolding compound or a casting compound) and at least partially encloses the coil body. The rotational speed sensor moreover comprises fixing arrangement for facilitating a configuration of the casing. The fixing arrangement for radially extending connecting lines can comprise a material core clearance in the casing so as to fix the electrical connecting lines at a mutual spacing when configuring the casing. The fixing arrangement can also comprise an anti-twist safeguard so as to prevent the coil body rotating relative to a tool used for configuring the casing while the latter is being configured, wherein the anti-twist safeguard partially protrudes (radially) from the casing, or extends at least up to an external surface of the casing. At least one type, or both types, of the fixing arrangement is/are configured in the inductive rotated speed sensor.
The material core clearance moreover offers the advantage that rapid cooling is achieved when configuring the casing. Said material core clearance can be achieved, for example, by a protrusion or a die in the tool. The anti-twist safeguard can engage in one or a plurality of depressions/grooves in the tool so as to hold the coil body secured against twisting in the tool, for example.
The casing optionally comprises external ribs which are configured on an external surface and are suitable for clamping the sleeve of an external protective sleeve, wherein the anti-twist safeguard is part of a portion of a rib. Since the rib is generated by a groove in the tool, an engagement of the anti-twist safeguard in the groove automatically leads to an anti-twist safeguard. No modifications on the tool are required here.
The casing optionally comprises at least one plateau on which at least one rib can terminate, for example. The plateau can be configured for fixing thereon an external protective sleeve by caulking. Therefore, the plateau represents in particular a protrusion (said plateau is “standing proud”) and may have the same height level as the anti-twist safeguard. The caulking utilized can be in the form of a localized plastic deformation of the protective sleeve that leads to the latter being fastened to the casing. The casing may also be slightly plastically deformed at the location.
The inductive rotational speed sensor optionally comprises a protective sleeve (for example of metal) having a trumpet-shaped peripheral widening for protecting the casing. The protective sleeve at least partially receives the casing, wherein the trumpet-shaped peripheral widening points toward the connecting lines. An O-ring seal is moreover optionally configured (for example on an external peripheral region) between the protective sleeve and the casing so as to guarantee reliable sealing. The trumpet shape facilitates the protective sleeve being pushed over the O-ring.
The trumpet-shaped peripheral widening optionally comprises fastening arrangement for fastening the protective sleeve and the casing to one another or to the tool. Accordingly, the casing can optionally have a protrusion which comes to engage with the latching hook/bayonet mount so as to achieve the fastening. For example, the fastening arrangement can have a latching hook and/or a bayonet mount, so that the protective sleeve is imparted more grip on the casing (for example in addition to the ribs and the caulking).
The casing optionally comprises complanate faces, the connecting lines to the coil body running therebetween, so as to facilitate handling during or after the configuration of the casing and to provide a further anti-twist safeguard. The complanate faces optionally comprise a labeling area (for example so as to configure thereon labeling by a laser).
The present invention also relates to a method for producing an inductive rotational speed sensor such as has been defined above, for example. The method comprises:
For radially extending connecting lines, the fixing can comprise introducing a die (or a protrusion) between the electrical connecting lines during the configuration of the casing, so as to fix the connecting lines at a predetermined mutual spacing. The fixing can also comprise firmly holding the coil body in a tool utilized for configuring the casing, while utilizing an anti-twist safeguard, wherein the anti-twist safeguard projects from the coil body in the radial direction so as to be held by the utilized tool in this way. The anti-twist safeguard is partially enclosed by the casing when configuring the casing.
The configuration of the casing optionally comprises using a tool which has a table which is displaceable in a linear manner, having at least two lower tool parts and an upper tool part so as to enable the coil body to be populated by a linear displacement. The terms “top” and “bottom” can be defined under the assumption that a flow direction of the plastics material of the casing is from the top toward the bottom, for example. The coil body for electrically contacting the coil can comprise two conductor rails which comprise in each case a barrier between a wire connector of the coil and the contact region for the electrical contacting by the connecting lines. The method according to exemplary embodiments in this instance (as part of configuring the casing) optionally comprises overmolding of the coil body, wherein the overmolding is carried out in such a manner that the barriers cause a deflection of an overmolding compound utilized in the overmolding. In order for the deflection to be effected, the barriers have a corresponding geometry (width, height, etc.) and are correspondingly disposed (for example in the proximity of the wire connector of the coil and perpendicular to the overmolding direction). Since a high pressure is often utilized during overmolding, the barriers offer the protection for the wire contacts to the coil (for example the corresponding weld seams), because the main pressure is initially absorbed by the barrier.
Exemplary embodiments of the present invention achieve at least part of the above-mentioned technical objects by way of the specific fixing arrangement which facilitate the production of the inductive sensors. To this end, anti-twist safeguards can be configured directly as part of the coil body so as to prevent any rotation during an exemplary overmolding process, on the one hand. Moreover, a material core clearance for the radial variant, caused by a die/protrusion, permits reliable fixing of the electrical contact during the overmolding process. Since an overmolding process leads to high mechanical stress on the electrical contacts, protecting or fixing the contacts in a reliable manner is important in order to keep the defect rate low.
This simple processing offers the further advantage that the number of required parts can be significantly reduced, this in turn leading to a reduction of costs.
The exemplary embodiments of the present invention will be better understood by the following detailed description and the appended drawings of the different exemplary embodiments, which are however not to be understood as restricting the disclosure to the specific embodiments but as serving only for the purpose of explanation and understanding.
Moreover provided in the inductive rotational sensor are fixing arrangements 150, 160 which are configured so as to facilitate a configuration of the casing 200. To this end, the fixing arrangements 150, 160 for the radial sensor shown comprise a material core clearance 160 which is configured in the casing and is capable of keeping the electrical connecting lines 30 at a specific mutual spacing when configuring the casing 200. A reliable insulation between the two connecting lines is thus guaranteed even when high mechanical stress by virtue of configuring the casing is exerted on the respective contacts. Moreover, faster cooling upon configuring the casing 200, and thus a faster production, are enable by the material core clearance 160.
The fixing arrangement can furthermore comprise anti-twist safeguards 150 which prevent the coil body 100 rotating relative to a tool used for configuring the casing 200 while the latter is being configured. The anti-twist safeguard 150 in an exemplary manner partially protrudes from the casing 200, or extends at least up to an external surface of the casing 200, so as achieve a grip in the surrounding tool for configuring the casing.
Situated in the coil body 100 are a magnet 40 and a pole core 50, the latter by way of the bar-shaped end 51 thereof protruding from the casing 200, or the coil body, respectively, so as to efficiently conduct the magnetic flux lines, or the variations thereof, from an external region into the interior of the coil 10. The coil 10 in a front region is axially delimited by a disk-shaped end portion 115 of the coil body 100, said end portion 115 has an aperture through which the bar-shaped end 51 of the pole core 50 extends.
Finally, the coil body 100 comprises a latching hook 130 which is configured for fixing the magnet 40 in terms of an axial displacement of the latter parallel to the axial axis R. This fixing offers the advantage that the magnet 20 and the pole core 50 in the event of a production fault can be removed prior to being further overmolded, or even not joined at all. The reject rate in production is minimized in this way.
The material core clearance 160 from
The anti-twist safeguard 150 utilized at least partially protrudes from the casing 200, or extends at least up to a surface. The anti-twist safeguards 150a, 150b may comprise various shapes of protrusions. For example, the anti-twist safeguards 150 may be arrow-shaped elements 150a or pin-shaped elements 150b. The anti-twist safeguard is achieved by anchoring or retaining the anti-twist safeguard 150 in the exemplary overmolding tool utilized. The arrow-shaped elements 150a may become part of the rib 230 (see
The protrusions 150a, 150b in the radial direction extend by at least 0.1 mm beyond the disk-shaped end portions 115, for example (see
The exemplary embodiment from
A seal ring 330 is optionally likewise configured in a groove of a widened portion of the casing 200, so as to guarantee reliable sealing when the protective sleeve is placed thereon.
Fastening arrangement (not to be seen in
The conductor rails 120 are again disposed on both sides of the magnet 40 and comprise a front contact portion 12 for the coil wires from the coil 10. The conductor rails 120 form a barrier 170 which during an exemplary overmolding procedure guide an overmolding compound away from the contact region 12 of the conductor rails 120 and thus protects contacting of the coil 10. As a result, it is possible for the overmolding procedure to be carried out at a very high pressure without risking that damage to the electrical contact to the coil renders the rotational sensor useless.
The coil 10 is held in a front coil region by the coil body 100, wherein the magnet 40 and a separate pole core 50 are disposed within the coil holder 100. The coil body 100 conjointly with the conductor rails 120 and the contacting to the connecting lines 30 is protected by a casing 200 (hermetically sealed, for example). Moreover, the casing 200, which comprises a plastics material, for example, is protected by a protective sleeve 300. The protective sleeve 300 can comprise a metal, for example, so as to offer reliable protection against mechanical influences. The bar-shaped end 51 of the pole core 50 in an exemplary manner abuts the protective sleeve 300 so as to guarantee reliable transmission of the magnetic flux lines or a variation through a pole wheel running past.
According to exemplary embodiments, the contact regions 122 can be flexibly bent so that the production can be carried out in an identical manner based on one universal coil body 100. The axial rotational sensor as well as the radial rotational sensor can utilize the same components. As opposed to conventional rotational sensors, different coil bodies or conductor rails for the axial rotational sensor and the radial rotational sensor are not required. This leads to a reduction in terms of the required parts, to simple processing and assembling, and thus to a reduction in costs.
While an overmolding process can in particular be utilized for configuring the casing 200, the invention is not intended to be limited to a specific casing. Other plastics materials or methods can likewise be utilized (for example, casting). The tool utilized to this end advantageously comprises a table that is displaceable in a linear manner, having two lower tool halves and one upper tool half. The two lower tool halves serve for populating the components to be encased (coil body with coil, conductor rails, etc.) and the upper tool half is provided for supplying the material of the casing (for example the overmolding compound).
Since the cable lengths of rotational sensors in the vehicle industry can be very long (for example, 4 m and more), the table that is displaceable in a linear manner in comparison to conventional tools which for populating carry out a rotating movement, offers the particular advantage that the connecting lines/cables cannot rotate or catch in the tool. This in turn has the advantage that a fully automatic production is possible, because the in some instances long connecting cables are displaced only in a linear manner and as a result, if at all, barely cause an obstacle in the production process.
Advantages of exemplary embodiments comprise in particular:
The features of the invention disclosed in the description, the claims and the figures can be relevant to implementation of the invention individually as well as in any arbitrary combination.
Number | Date | Country | Kind |
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10 2018 132 709.9 | Dec 2018 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2019/083502 | 12/3/2019 | WO | 00 |