Speed or angular position electromagnetic transducer

• US 3,942,045 A
• Filed: 06/05/1974
• Issued: 03/02/1976
• Est. Priority Date: 06/05/1974
• Status: Expired due to Term

• Current Assignee: Fiat Societa Per Azioni
• Original Assignee: Fiat Societa Per Azioni
• Inventors: Palazzetti, Mario
• Primary Examiner(s): Duggan, Donovan F.
• Application Number:
  US05/476,495
• Time in Patent Office: 636 Days
• Field of Search: 310/155, 310/154, 310/111, 310/168, 310/13, 324/174
• US Class Current: 310/155
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors

Abstract

An electromagnetic angular speed or angular position transducer comprises a permanent magnet with closely spaced pole faces and a ferromagnetic core magnetically connected to the magnet and carrying a coil. The transducer cooperates with a toothed wheel the teeth of which are moved past the pole faces and the core in such a way that two magnetic circuits are completed by the teeth, one passing through the teeth and the two pole faces, and the other passing through the teeth and the core. The two magnetic circuits are in parallel with one another and the reluctance of each changes as the teeth move therepast. The circuit through the two pole faces ensures that the magnet is operated with a high leakage flux so that small changes in the reluctance cause relatively large flux changes and thus a relatively high electromotive force in the coil wound about the core.

Claims

1. In an electromagnetic angular speed or position transducer of the type having means defining a permanent magnetic circuit, including a cylindrical permanent magnet means having radial magnetization with two pole faces, a toothed wheel, which is relatively rotatable with respect to said cylindrical permanent magnet means to complete a magnetic circuit when positioned adjacent said pole faces whereby relative movement between the teeth of said toothed wheel and said pole faces causes regular changes to the reluctance of said magnetic circuit;

a coil wound onto said permanent magnet means in which an electric current is induced by flux changes resulting from said changes in reluctance;

the improvements comprising;

said coil is wound on a ferromagnetic core located axially within said cylindrical permanent magnet means forming part of said magnetic circuit of said permanent magnet, and

said pole faces are positioned with respect to one another whereby, said magnetic circuit means and said pole faces form part of a first closed magnetic circuit which can be completed by said toothed wheel being adjacent thereto, and said core on which said coil is wound forms part of a second closed magnetic circuit which can be completed by said toothed wheel being adjacent thereto whereby both said circuits experience reluctance changes upon movement of said toothed wheel with respect to said magnetic circuit means, said first and second closed magnetic circuits being in parallel with one another.