Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2000-01-20
2002-06-04
Snow, Walter E. (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207200, C324S207220
Reexamination Certificate
active
06400144
ABSTRACT:
The invention relates to a magnetic position sensor in the case of which at least two stator elements are arranged in a magnetic field and a magnetic field probe is located in the measuring air gap between the stator elements, a means tracking a moving object being arranged parallel to the plane defined by the stator elements.
Hall angle sensors are known which output signals which are proportional to angles. The detection of a rotary movement is performed in this case via a Hall probe which is located in an air gap which is constructed between two stator halves.
A rotor is fixedly arranged on a shaft which, in turn, is connected to the object whose change in position is to be detected.
The stator elements are fastened to the sensor housing. The Hall sensor is arranged in the measuring air gap between the stator elements in a radial fashion relative to the direction of rotation of the shaft, with the result that its electric terminals project beyond the stator elements and are connected to an evaluation circuit on a printed circuit board in order to produce the electric connection.
Disadvantageous in this case is the complicated mounting of the sensor, since it is necessary for the mounting of the stator elements, on the one hand, and the electric connection between the Hall probe and the printed circuit board, on the other hand, to be performed in separate method steps.
A magnetic position sensor of the generic type is disclosed in GB 2 272 060 A, in the case of which at least two stator elements are arranged in a magnetic field, the measuring air gap being bounded by the stator elements, and a magnetic field probe being located in this measuring air gap. In this case, the magnetic field probe is arranged directly, and the stator element is arranged via an auxiliary support, on a common supporting element. This arrangement also requires a complicated mounting, in particular of the stator elements via the auxiliary support on the printed circuit board.
It is therefore the object of the invention to specify a magnetic position sensor which can be produced simply and cost-effectively.
According to the invention, the object is achieved by virtue of the fact that at least one stator element and the magnetic field probe are arranged on a common supporting element.
Particularly when the supporting element is aligned parallel to the radial extent of the stator element, it is possible to reduce the size of the design of the magnetic position sensor and to mount stator elements and the magnetic field probe, in common with other electronic components, on the supporting element in a single method step.
The stator element advantageously has a region, angled off in the direction of the supporting element, for fastening the stator element to the supporting element. The end of said angled-off region can be placed during mounting directly onto the copper cladding of the printed circuit board and be butt-fastened, for example by reflow soldering.
In a further embodiment, adjoining the first angled-off region of the stator element is a second angled-off region which is constructed parallel to the supporting element and is connected thereto. In this variant, the second angled-off region is connected in a planar fashion to the copper cladding of the supporting element, and this permits a better adhesion of the stator to the supporting element. This part, as well, can be fastened simply to the supporting element by means of surface soldering.
In a particularly simple embodiment, the stator element is constructed as a bent stamping which presses directly on the supporting element. The stator element thus constructed has at least one offset which is inserted into the supporting element through an opening therein and fixed there on the opposite side.
The production as a bent stamping permits rivets and washers to be dispensed with, with the result that the mounting process can be automated by means of soldering. The possibilities of configuring the stator elements can also be combined.
In one embodiment, the magnetic field probe is arranged radially offset relative to a shaft in the measuring air gap, the shaft being fixedly connected to the rotor, which is arranged in the axial direction relative to the stator elements.
The rotor is constructed in two parts, each soft-magnetic rotor element having at least one circular segment and the rotor elements being interconnected rigidly rotated with respect to one another, with the result that the circular segment of the first rotor element is situated opposite a segment gap in the second rotor element, the stator elements being arranged between the rotor elements, and a magnet which generates the magnetic field in the axial direction being arranged both between the rotor elements and the stator elements.
The advantage of the invention consists in that the rigid bipartite rotor configuration suppresses the effects of the axial play on the sensor signal, since the two air gaps occurring between the rotor and stator are simultaneously varied in opposite directions and the sum of the air gaps is therefore always constant.
The sum of the two air gaps, which are constructed in the axial direction between the rotor elements and one stator element each, is preferably small compared to the axial extent of the magnet, as a result of which the magnetic flux through the stator is supported.
In one embodiment, the stator elements are likewise constructed to resemble circular segments.
In one development, the outside radius of the circular segment of at least one rotor element is smaller than the outside radius of a stator element. This permits the arrangement of the magnetic field probe parallel to the axis of rotation of the shaft of the sensor in the air gap between the two stator elements. The advantage of this arrangement consists in that the magnet can now be optimally dimensioned, since the axial spacing between the two rotor parts can be varied freely.
Since the angular dependence of the flux guidance is achieved not via the contour or magnetization of the magnet, but by the asymmetric shape of the rotor, the requirements placed on the magnet are minimal.
The magnet need only generate an axially directed field. The latter can be generated optionally by a rotatably mounted permanent magnet or a magnet which is fixed with reference to the stator and which in this case can be embodied either as a permanent magnet or as an electromagnet.
In one development, the magnet is constructed as a permanently magnetic annular magnet.
The stator segments are advantageously arranged in this case always coaxially around the-axis of rotation of the rotor shaft.
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Hannewald Thomas
Sauerschell Wolfgang
Wehner Andreas
Wiese Peter
Mannesmann VDO AG
Mayer Brown & Platt
Snow Walter E.
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