Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element
Patent
1994-05-05
1996-07-23
Williams, Hezron E.
Measuring and testing
Speed, velocity, or acceleration
Acceleration determination utilizing inertial element
7351402, 25023114, G01P 1508, G01D 534
Patent
active
055378749
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an angular acceleration detector which detects an angular acceleration of a rotary body such as a motor shaft and the like over an infinite range of rotational angle of the rotary body in a non-contact manner.
BACKGROUND ART
Conventionally, a liquid rotor-type tachometer and an eddy-current tachometer have been known as an angular acceleration detector for detecting an angular acceleration of a rotary body.
The liquid rotor-type tachometer, as shown in FIG. 15 in which the structure thereof is illustrated, detects movements of a liquid instead of those of the pendulum of a servo-type acceleration detector, and measures a value of a feedback electrical current applied to a servo system in order that the servo system realizes a balanced condition with respect to the movement of the liquid, to thereby determine an angular acceleration according to the measured feedback electrical current. More specifically, the liquid 2 is enclosed in a ring-shaped tube 1 and is partitioned by a paddle 3. When the tachometer itself begins to rotate, the liquid tends to stay at an absolute position and therefore the paddle dividing the liquid is angularly deflected by a force applied thereto. A deflection detector 4 detects this deflection and supplies a torquer with a feedback electrical current in order to return the paddle 3 toward a zero position. Since the value of the feedback electrical current is proportional to an amount of angular acceleration occurred, the occurred angular acceleration can be determined in accordance with the instant feedback electrical current.
On the other hand, as shown in FIG. 16, the eddy-current tachometer is constituted in that a permanent magnet is used to form a magnetic circuit and a cylindrical aluminum rotor is disposed in the circuit so that an angular acceleration is detected based on a magnetic electromotive force occurred in accordance with a change in rotational speed of the rotor.
However, since the liquid rotor-type tachometer is limited in a range of measuring rotational angle, it has a defect that it cannot detect a angular acceleration over an infinite rotational range. While, the eddy-current tachometer needs to be provided with a high-sensitive signal processing circuit because detected signals are extremely weak.
An object of the present invention is, in consideration of the above defects, to provide an angular acceleration detector capable of detecting a angular acceleration of a rotary body over an infinite rotational angle.
DISCLOSURE OF INVENTION
An angular acceleration detector of the present invention has two slit-carrying discs (first and second discs) mounted fixedly and coaxially in an opposed state on a rotary body, and a semiconductor position detecting unit formed as a detecting means and consisting, for instance of a light emitting element and a semiconductor position detecting member which are disposed in an opposed state across the slits in the respective discs, the angular acceleration of the rotary body being detected by using this detecting unit. The slits in the second disc cross at a predetermined angle the slits in the first disc. The second disc has an annular weight portion at the radially outer or inner side of a slit-formed portion, and a resiliently deformable spring portion circumferentially arranged at the inner side of the weight and slit-formed portions.
As the rotary body rotates, the two discs rotate together with the rotary body. During the rotation, the spring portion is deformed resiliently and slightly in a circumferential direction by the inertia force of the weight portion of the second disc in accordance with the change in rotational speed of the rotary body. As a result, the slits formed at the radially outer side of the spring portion are also moved slightly in the circumferential direction, so that the crossing portions of the slits of the second disc relative to those of the first disc moves according to the movements of the slits of the second disc. The movements of the crossi
REFERENCES:
patent: 3654480 (1972-04-01), Stepenson
patent: 4077266 (1978-03-01), Takamatsu
patent: 4767925 (1988-08-01), Kawamoto
Akahane Akira
Godler Ivan
Harmonic Drive Systems Inc.
Oda Christine K.
Williams Hezron E.
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