Compact magnetic encoder

• US 4,983,916 A
• Filed: 01/25/1989
• Issued: 01/08/1991
• Est. Priority Date: 01/26/1988
• Status: Expired due to Fees

• Current Assignee: Yamaha Corporation
• Original Assignee: Yamaha Corporation
• Inventors: Hayashi, Yoshinori, Nishimura, Seiya, Iijima, Kenzaburou
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US07/301,815
• Time in Patent Office: 713 Days
• Field of Search: 324/173, 324/174, 324/207, 324/208, 324/235, 324/251, 324/252, 338/32 R, 338/32 H, 310/67 R, 310/68 R, 310/68 B, 310/156, 310/168, 310/171
• US Class Current: 324/207.21
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01P 3/487 delivered by rotating magnets

Abstract

In construction of a magnetic encoder used for detection of displacement of a mobile body, a circular magnetized pattern is formed on one longitudinal end face of a magnetic rotary spindle mechanically coupled to the mobile body, and a magnetic sensor faces the magnetized pattern with a prescribed gap. Direct formation of the magnetized pattern on the rotary spindle excludes production errors caused by the conventional coupling process and end-face magnetization assures significant compactness of the entire construction.

Claims

1. An improved magnetic encoder, comprising:

a housing having an axial through-hole;

a magnetic rotary spindle rotatably supported in said axial through-hole of said housing and provided with a magnetized pattern formed circularly on its one longitudinal end face along the periphery; and

a magnetic sensor attached to said housing and facing said magnetized pattern on said one longitudinal end face of said rotary spindle with a prescribed clearance;

said magnetized pattern being formed by use of a sine wave of a wavelength λ and

having a constant pitch equal to said wavelength λ

;

said magnetic sensor being made up of first and second magnetic resistor elements which (i) vary in inherent resistance depending on the intensity of an applied magnetic field and which (ii) are electrically separated from each other by an insulating layer;

each said first magnetic resistor element being phased from an adjacent second magnetic resistor element by a distance equal to λ

/4; and

said first and second magnetic resistor elements being arranged in a circular disposition just corresponding to the circular arrangement of said magnetized pattern on said one longitudinal face of said rotary spindle;

being circularly arranged side-by-side, each forming a hemicircle; and

being concentrically arranged without superposition.

2. A device for magnetically detecting displacement of a separate, mobile body, comprising:

a housing having an axial through-hole;

a magnetic rotary spindle (i) rotatably supported in said axial through-hole of said housing, (ii) provided with a magnetized pattern directly formed on one of its longitudinal end faces along the periphery, and (iii) being made of one of Fe--Cr--Co and Fe--Co--Mg type alloys;

a mechanical coupling connected to said spindle for coupling said spindle to the mobile body; and

a magnetic sensor attached to said housing and facing said magnetized pattern on said one longitudinal end face of said rotary spindle with a prescribed clearance;

said magnetized pattern being formed by use of a sine wave of a wavelength λ and

having a constant pitch equal to said wavelength λ

;

said magnetic sensor being made up of a plurality of magnetic resistor elements which vary in inherent resistance depending on the intensity of an applied magnetic field, including first magnetic resistor elements and second magnetic resistor elements electrically separated from each other by an insulating layer;

said first and second magnetic resistor elements being arranged in a circular disposition just corresponding to the circular arrangement of said magnetized pattern on said one longitudinal face of said rotary spindle;

each said first magnetic resistor element being phased from an adjacent second magnetic resistor element by a distance equal to λ

/4;

said first and second magnetic resistor elements being concentrically arranged without superposition; and

said first and second magnetic resistor elements being circularly arranged side-by-side, each forming a hemicircle.