Electricity: measuring and testing – Electrical speed measuring – Including speed-related frequency generator
Patent
1982-05-13
1985-01-22
Krawczewicz, Stanley T.
Electricity: measuring and testing
Electrical speed measuring
Including speed-related frequency generator
G01P 348, G01P 354
Patent
active
044954646
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a non-contacting, speed-detecting device of a DC generator type, and especially to the above-mentioned device comprising a cylindrical permanent magnet rotor having N and S poles distributing alternatingly in the circumferential direction, a stator facing said permanent magnet rotor, a permanent magnet for location rotating coaxially with said permanent magnet rotor, and magnetic induction switches positioned close to the circumference of said permanent magnet for location.
2. Background of the Invention
A non-contacting, speed-detecting device of the DC generator type of the prior art which is used for detecting the rotating speed of, for example, a rotary machine is illustrated in FIGS. 1(A), (B), and (C). The device of FIG. 1 comprises a cylindrical permanent magnet rotor 1 having N and S poles distributing alternatingly in the circumferential direction, a stator 2 facing said permanent magnet rotor 1, stator windings 4 wound in said stator 2, a permanent magnet 3' for location rotating coaxially with said permanent magnet rotor 1, and magnetic induction switches 5 positioned close to the circumference of said permanent magnet 3' for location so that said magnetic induction switches are actuated in response to the rotating position of said permanent magnet 3' for location, and, accordingly, the desired output signal is obtained.
In the speed-detecting device of FIG. 1, the permanent magnet rotor 1 has two S pole regions and two N pole regions alternating at 90.degree. in the circumferential direction on its lateral circumferential surface. The stator 2 is arranged concentricly around the rotator 1 so that it is close to its lateral circumferential surface. In the stator 2, windings 4 of four phases (W.sub.1, W.sub.2, W.sub.3, and W.sub.4) displaced by an electric angle 90.degree. are wound. The permanent magnet 3' for location is mounted on the rotating axis at a distance from the rotor 1 in the axial direction. The permanent magnet 3' for location has an S pole region .alpha. on its lateral circumferential surface. Four magnetic induction switches 5 are positioned on the same circle close to the lateral circumferential surface of the permanent magnet 3' for location, and positioned distant from each other. Each of the magnetic induction switches is positioned so that it corresponds to each phase of the stator windings 4 and detects that the S region .alpha. of the permanent magnet 3' for location passes close to it. The structure of the permanent magnet 3' for location is illustrated in detail in FIG. 1(C).
The circuit for obtaining a DC voltage output proportional to the rotating speed in accordance with the non-contacting, speed-detecting device of a DC generator type of FIG. 1 is illustrated in FIG. 2. The alternating voltage generated in each phase of the stator windings 4 is switched selectively by the semiconductor switch 8 actuated by the location signal from the magnetic induction switch 5 and is inputted into the operational amplifier 7 through the resistors R.sub.1, R.sub.2, R.sub.3, or R.sub.4. The DC voltage output proportional to the rotating speed is obtained at the output terminal 9 of the operational amplifier 7. In FIG. 2, the resistors R.sub.5, R.sub.6, R.sub.7, and R.sub.8 are pull-up resistors, R.sub.9 is a feed-back resistor, and R.sub.10 is a reference input resistor.
When the permanent magnet 3' for location is rotating at a constant speed in the speed-detecting device of FIG. 1, the variation of the magnetic flux density in regard to time at the position on which the magnetic induction switch 5 is mounted is illustrated as .phi.' in FIG. 3. The above-mentioned magnetic flux density .phi.' assumes a maximum value when the S pole region 12 passes the detecting position and assumes a minimum value when the N pole region 13 passes the detecting position. In the transition region 14 between the S pole region 12 and the N pole region 13, the magnetic flux density .phi.' changes relatively slowly from a maximum value to a
REFERENCES:
patent: 3188620 (1965-06-01), MacCallum
patent: 3447034 (1969-05-01), Smith
patent: 3548663 (1970-12-01), Radin
Clark, Rotary Tachometer/Encoder, IBM Technical Disclosure Bulletin, Feb. 1976, p. 2787.
Amemiya Yoichi
Iwamatsu Noboru
Kozai Yoshinori
Fujitsu Fanuc Limited
Krawczewicz Stanley T.
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