Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-12-11
2001-04-17
Oda, Christine (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207240, C702S158000
Reexamination Certificate
active
06218829
ABSTRACT:
The invention relates to a linear drive having a device for registering the displacement travel and/or position, in particular in a small-scale linear drive according to the preamble of Patent claim
7
.
Devices for registering the displacement travel and/or position of two components which can be displaced with respect to one another are already known in various embodiments such as, for example, DE 42 10 934 C1, DE 39 35 261 A1, DE-C 12 62 621 and JP 2-62454 A., In: Patent Abstracts of Japan, M-976, May 21, 1990, Vol. 14, No. 237.
These devices have an overall complicated structure and can, in particular, not be implemented on a very small scale either.
A device of similar generic type in which, however, only one sensor is used is known from U.S. Pat. No. 4,725,776. Only incremental registering of the displacement travel is possible with this device.
In devices of the generic type according to EP 0 109 296 A2 and GB 22 05 406 A, absolute registering of position is already possible by means of magneto-resistive sensors. For this purpose, in said publications, sensors are assigned different profile regions. The structural expenditure which is necessary for this is large.
The invention is concerned with the problem of implementing on as small a scale as possible and in a simple constructed fashion a linear drive device of the generic type with a high degree of display precision.
A solution in this respect is shown by the characterizing feature of claim
7
.
Expedient refinements are the subject-matter of the subclaims. These are explained in more detail with reference to an exemplary embodiment.
According to the invention, in a linear drive for measuring the displacement travel and the displaced position of the sliding component of this drive, a drive profile in particular which may, per se, possibly already be present on the sliding component can be employed for changing a magnetic field using a magneto-resistive sensor, and this change in the magnetic field can in turn as one of two evaluation criteria, be evaluated in order to determine the displacement travel and the absolute displaced position. The drive profile of a sliding component, implemented for example as a spindle or sliding sleeve, is here either threaded or grooved with identical intervals between the grooves. The grooved or threaded profile is in particular such that there are profile faces inclined with respect to the longitudinal axis of displacement as far as possible in all regions in the longitudinal direction. Otherwise, the measurement precision suffers. For example, a thread with an approximately triangular threaded profile cross section with the profile triangles arranged directly in a row in the longitudinal direction of displacement is ideal for the device according to the invention.
With a relatively fine drive profile of a sliding component, that is to say, for example, with a fine threaded profile with which small amounts of displacement travel can be obtained with high transmission ratios, an extremely sensitive magneto-resistive sensor, which is known per se, is used for precise displacement travel measurement and evaluation.
Such a sensor is also assigned to the region of the second type of profiling of the sliding component, the second type of profiling having to satisfy the same set of requirements as the previously described drive profile.
These sensors are placed in a magnetic field whose configuration depends, inter alia, on the position of the sliding component. For this purpose, each of the individual sensors is aligned with respect to the surface of the drive profile, for example a fine thread of the spindle of a spindle drive, or of the second type of profiling, in such a way that a displacement of the edges of the threaded profile or of the second type of profiling through the magnetic field makes it possible electronically to register and image the displacement which has taken place. Electronic registration and imaging of the displacement of the drive profile of the spindle or of the spindle region with the second type of profiling means that the peaks and valleys of the drive profile of the spindle which are displaced past the sensor are correspondingly registered and evaluated. Thus, it is possible to determine absolutely the position of the sliding component in an extremely simple way.
If a linear drive is driven by means of an electrical servomotor, which is a brushless, permanent-magnet-excited servomotor, in a linear drive with very little play the magnetic field sensor which is used for measuring travel and position can simultaneously be used to commutate this motor.
Moreover, the values determined with the device for registering the travel and/or position according to the invention can be used for the open-loop and closed-loop control of the motor of the linear drive which is, in particular, an electric motor.
Using magneto-resistive magnetic field sensors as magneto-resistive length measuring elements is known per se. In this respect, reference is made, for example, to the following documents: “in Nanometerschritten” [In nanometer increments], Konstruktion & Elektronik [Design and Electronics], No. 26/27 of 16.12.1992, page 8; digitale Längen- und Winkelme&bgr;technik” [Digital length and angle measuring technology], verlag moderne industrie [Modern industry publishing house], 2nd Edition 1991; F. Dettmann, U. Loreit “Positionsmessung mit magnetoresistiven Sensoren” [Position measurement with magneto-resistive sensors] Symposium magnetoresistive Sensoren [Symposium of magneto-resistive sensors] 25.06.92 in Dortmund.
The invention is explained below in more detail with reference to drawn models and various functional diagrams, and a particularly advantageous exemplary embodiment is also specified. In said drawing:
FIG. 1
shows a schematic sectional view of a planetary roller-type spindle drive as linear drive device,
FIG. 2
shows the arrangement of a magnetic field sensor with reference to the profile of a spindle with qualitative representation of the magnetic field,
FIG. 3
shows a diagram with electronic imaging of the intervals between the profile peaks of a longitudinally displaced spindle,
FIG. 4
shows the arrangement of two magnetic field sensors with reference to a spindle which is extended by a driver spindle and has different pitch values of the two spindles, as a preferred exemplary embodiment of the invention,
FIG. 5
shows a diagram with the electronic imaging of the intervals between the profile peaks of the actual spindle on the one hand and of the driver spindle on the other from the exemplary embodiment according to FIG.
4
.
REFERENCES:
patent: 4715241 (1987-12-01), Lipinski et al.
patent: 4725776 (1988-02-01), Onodera et al.
patent: 5090489 (1992-02-01), Ettori
patent: 5299143 (1994-03-01), Hellinga et al.
patent: 5315244 (1994-05-01), Griebeler
patent: 1 262 621 (1968-03-01), None
patent: 39 35 261 (1990-05-01), None
patent: 42 10 934 (1993-07-01), None
patent: 195 33 964 (1996-03-01), None
patent: 0 109 296 (1984-05-01), None
patent: 2 205 406 (1988-12-01), None
patent: 57 046 670 (1982-03-01), None
patent: 2-62454 (1990-03-01), None
Spohr Hans-Hermann
Wittenstein Manfred
Collard & Roe P.C.
Oda Christine
Wittenstein Motion Control GmbH
Zaveri Subhash
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