Electricity: measuring and testing – Magnetic – Displacement
Patent
1985-12-13
1987-10-27
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
Displacement
324174, 324226, 403369, G01P 3487, G01B 730, B23Q 520, F16B 200
Patent
active
047032626
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a magnetic sensor system for spindle orientation whereby the spindle of a machine tool or the like is stopped at a fixed position in a contactless manner. More particularly, the invention relates to a mounting structure for mounting a magnetic body of the magnetic sensor system on the spindle.
A magnetic sensor system for spindle orientation in which the spindle of a machine tool or the like is stopped at a fixed position in a contactless manner, ordinarily is adapted to extract a position feedback signal from a magnetic sensor directly connected to the spindle and to process the signal by an orientation circuit. The position feedback signal is for the purpose of detecting the position of a rotary shaft. A magnetic signal from a magnetic body attached to the spindle at a prescribed position thereon is detected and extracted by a sensing unit arranged on a mechanically stationary member.
FIGS. 6(A), (B) are diagrams showing an example of the arrangement of a position detector for detecting the position of a spindle 1. FIG. 6(A) is a side view and FIG. 6(B) is a cross-sectional view along the cross-section; of the rotating spindle 1.
In order to stop a prescribed portion of the spindle 1 at a fixed position, the position detector comprises a magnetic body 10 attached to the spindle at a rotational angle which is the same as that of the prescribed portion, and a sensing unit 11 for producing a magnetic signal delivered to an orientation circuit 12. As shown in FIG. 6(C), the magnetic body 10 has two rubber magnets 10b of triangular cross section accommodated in a case 10a, and is mounted in such a manner that the magnetizing strength thereof changes continuously from the S pole to the N pole in the direction of spindle rotation (the direction of the arrow). The sensing unit 11 is mounted on a mechanically stationary member in the neighborhood of the spindle 1 to confront the magnetic body 10 across a distance of 1 to 2 mm.
As shown in FIG. 6(C), the sensing unit 11 is composed of three saturable reactors SRA.sub.1, SRA.sub.2, SRA.sub.3 arranged side by side in a case 11a. Each saturable reactor has a core CR on which coils L.sub.1, L.sub.2 are wound to produce mutually opposing polarities, as shown in FIG. 6(D). The coils L.sub.1, L.sub.2 have a common terminal TA to which a high-frequency signal from the orientation circuit 12 is applied, as well as respective terminals TB, TC from which a magnetic signal corresponding to the position of the magnetic body 10 is produced.
FIG. 6(E) is a waveform diagram of output signals PDS, ASV obtained from the orientation circuit 12 when the magnetic body 10 and sensing unit 11 are positionally related as shown in FIG. 6(C).
ASVa, PDS, ASVb indicate output voltage waveforms obtained from the sensing unit and corresponding to the respective saturable reactors SRA.sub.1, SRA.sub.2, SRA.sub.3 of the sensing unit 11. The orientation circuit 12 is so arranged that the sensing circuit produces an output voltage of zero as the center line of the magnetic body 10a successively achieves coincidence with the center lines of the saturable reactors SRA.sub.1, SRA.sub.2, SRA.sub.3, a positive output voltage at a position near the left of each center line, and a negative output voltage at a position near the right of each center line. Therefore, ASVa, PDS and ASVb have an overall voltage waveform that crosses the zero level. The voltage signal PDS is used as a rotation deviation signal of the spindle 1. A voltage signal ASV is the sum of a voltage waveform obtained by shifting the phase of the sensing circuit output ASVa by 180.degree., and the output ASVb of the sensing circuit. The voltage signal ASV is used as a signal indicating that the prescribed portion of the spindle 1 has arrived near the fixed position.
Though the position of the spindle 1 may be detected by arranging the position detector in the foregoing manner, the output signal ASV can be outputted as the voltage waveform shown in FIG. 6(F) besides the form shown in F
REFERENCES:
patent: 3317829 (1967-05-01), Kuhrt et al.
patent: 3565471 (1971-02-01), Nilsson
patent: 4064708 (1977-12-01), Breads
patent: 4345851 (1982-08-01), Soussloff
patent: 4385276 (1983-05-01), Bitzel
Fujioka Yoshiki
Tokuoka Hiroshi
Fanuc Ltd
Strecker Gerard R.
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