The invention relates to a speed sensor, in particular a wheel speed sensor having a sensor housing for accommodating a magnetic field sensor element, an adapter for holding the sensor housing and a magnetic encoder, and to the use of the speed sensor in motor vehicles.
Various configurations of such speed sensors are already known. The air gap or the reading range of so-called active sensors as well is dependent on the pitch of the corresponding gearwheel or magnetic encoder. In installation situations in which a large number of pole pairs or teeth or a sensor wheel of small diameter, paired with large assembly tolerances, occurs, the function cannot be ensured using a sensor with fixed dimensions.
Known adjustable wheel speed sensors are fixed to a displaceable fastening bushing by means of a small clamping screw with an external hexagon. However, only length adaptations of the order of magnitude of 10 mm can be achieved thereby.
In another known length adaptation of a wheel speed sensor, the wheel sensor is pushed, together with a resilient sleeve, into a receiving hole. Since the sensor remains displaceable in this arrangement, there is the possibility, during driving operation, of the sensor being pushed so far out of the hole again that signal interference or signal losses can occur as a result of the changing air gap.
Aspects of the invention relate to providing a speed sensor which is fixed such that it is adjustable in the longitudinal direction and is nevertheless secure in order to avoid signal interference on the basis of imprecise geometry.
This is achieved, according to aspects of the invention, by the features of a speed sensor having a sensor housing for accommodating a magnetic field sensor element, an adapter for holding the sensor housing and a magnetic encoder, wherein the speed sensor has a device for length adaptation or air gap adjustment, and in that the device has a clamping mechanism for holding the sensor housing.
The solution according to aspects of the invention surprisingly and simply provides a speed sensor with which the sensor housing is fixed such that it is adjustable in a simple and robust manner in the longitudinal direction and is nevertheless secure in order to avoid signal interference on account of undesirable changes in the distance between the sensor element and the encoder. The secure adjustment of the length of the wheel speed sensor also makes it possible to implement different installation situations with the sensor without having to produce a new sensor head for this purpose in each case, which may also be of interest, in particular, for small quantities.
In expedient embodiments of the speed sensor according to aspects of the invention, at least one of the following aspects can be advantageously expediently used with respect to the length adaptation and air gap adjustability:
The speed sensor is preferably in the form of a wheel speed sensor and is accordingly used as such.
The speed sensor preferably comprises at least one magnetic field sensor element and a magnetic encoder which comprises, in particular, at least one permanent-magnetic encoder track or an encoder track made of a magnetizable material, very particularly preferably in the form of a perforated disk or ring with stamped portions or a gearwheel.
The speed sensor preferably comprises a fastening device which is designed in such a manner that it can be used to adjust the air gap between the sensor element and the encoder.
The speed sensor is preferably in the form of an active sensor which requires electrical energy in order to operate at least its one magnetic field sensor element.
It is preferred for the speed sensor to have at least one magnetic field element, in particular a magnetoresistive sensor element or a Hall sensor element, an electronic signal processing circuit and, in particular, a plastic housing. This plastic housing is very particularly preferably substantially cylindrical.
It is expedient for the fastening device to comprise an adapter unit, a clamping ring and a pressure screw. In this case, the adapter unit is designed, in particular, in such a manner that it can accommodate the housing of the speed sensor in a recess in a manner safeguarded against rotation, and the recess of the adapter unit is designed in such a manner that it is suitable for receiving the clamping ring when arranged concentrically around the speed sensor housing, the adapter unit having a hole for fastening the entire speed sensor by means of a screw, for example.
A conical hole which forms a mating surface to the clamping ring is preferably provided in the central part of the adapter. The adapter expediently also comprises a threaded hole into which the pressure screw is screwed, which pressure screw axially loads the clamping ring and firmly braces the latter onto the sensor housing via the cone surfaces. On its outer surface, the clamping ring advantageously likewise has a cone corresponding to the cone hole in the adapter. The inner surface is designed in a manner corresponding to the sensor housing, with the result that a large clamping surface is ensured with an axial tensile stress.
In another embodiment, instead of the clamping ring, the clamping mechanism has an elastic shaping element which fixes the sensor housing by tightening the pressure screw using the transverse deformation. However, this fixing would then be less rigid, which may result in vibrations but would also result in a certain degree of flexibility when starting up the encoder on the sensor housing.
The speed sensor or wheel speed sensor or wheel sensor is thus designed, by way of example, in such a manner that the length of the air gap with respect to the magnetic encoder is adjustable in order to make it possible to compensate for the assembly tolerances in the vehicle: the air gap or the reading range, in particular of so-called active sensors, is dependent on the pitch of the corresponding gearwheel or magnetic encoder. In installation situations in which a large number of pole pairs or teeth or a sensor wheel of small diameter, paired with large assembly tolerances, occurs, the function cannot necessarily be ensured using a sensor with fixed dimensions.
Adjusting the length of the air gap or the positioning of the wheel speed sensor also makes it possible, for example, to handle different installation situations with a sensor without having to produce a new sensor head for this purpose, which may be of interest, in particular, for very small quantities. Previous adjustable wheel sensors were fixed, for example, to a displaceable fastening bushing by means of a small clamping screw, of the order of magnitude of an SW5 external hexagon. Only a length adaptation of the order of magnitude of 10 mm could also be achieved thereby.
Aspects of the invention also relate to the use of the speed sensor in motor vehicles, in particular in trucks.
The invention is best understood from the following detailed description when read in connection with the accompanying drawing. Included in the drawing is the following figure:
This sensor housing partially illustrated in
In this case, the sensor housing can be installed, for example, in conventional standard receiving holes with a nominal diameter of 16 or 18, for example.
In the embodiment illustrated in
The sensor can be installed in the vehicle, in particular the vehicle axle, as follows. The sensor is preassembled with the adapter, the clamping ring and the pressure screw and is delivered to the customer with the length preset, said customer inserting the sensor into the axle part and screwing it or fastening it to the axle part in another manner, as described above. Shrink-fit or press-fit connections are less suitable, however, with this assembly sequence. With another assembly sequence, the adapter with the clamping ring and the pressure screw is fitted in the axle part and the sensor is subsequently pushed in, if appropriate onto a stop, and is fixed using the pressure screw. A third assembly sequence provides for only the adapter to be first of all introduced into the axle part. The sensor with the pressure screw, which has been pushed on, and the clamping ring is then subsequently fitted into the adapter. This sequence is appropriate, in particular, if the adapter is intended to have a press fit or a shrink fit or is intended to be adhesively bonded.
Number | Date | Country | Kind |
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10 2009 035 065.9 | Jul 2009 | DE | national |
10 2009 054 521.2 | Dec 2009 | DE | national |
This application is the U.S. National Phase Application of PCT/EP2010/059355, filed Jul. 1, 2010, which claims priority to German Patent Application No. 10 2009 035 065.9, filed Jul. 28, 2009 and German Patent Application No. 10 2009 054 521.2, filed Dec. 10, 2009, the contents of such applications being incorporated by reference herein.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2010/059355 | 7/1/2010 | WO | 00 | 1/18/2012 |