Method of making a magnetic-encoding device having hall effect devices

• US 4,897,914 A
• Filed: 12/16/1988
• Issued: 02/06/1990
• Est. Priority Date: 09/20/1984
• Status: Expired due to Term

• Current Assignee: Phoenix America Inc. (discoverIE Group Plc)
• Original Assignee: Robert J. Loubier
• Inventors: Loubier, Robert J.
• Primary Examiner(s): Echols, P. W.
• Application Number:
  US07/285,499
• Time in Patent Office: 417 Days
• Field of Search: 29/602.1, 338/32 H, 324/202, 324/208, 324/117 H, 324/251, 324/174, 307/309
• US Class Current: 29/602.1
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G01D 5/142 using Hall-effect devices measuring magnetic variables using Hall-effect or other galvanomagnetic devices G01R33/06
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

Reproducibility in the manufacture of rotating shaft sensing encoders and similar devices employing Hall effect switching devices to sense changes in magnetic fields is achieved in the present invention by forming a frame of the encoder as a unitary or one piece arrangement for both supporting a shaft bearing and an angular behavior sensor, such as a Hall effect switch, thus controlling tolerances, air gaps and angular orientation of the sensor. Calibration of such a device to compensate for manufacturing variability in the Hall sensing device as well as any other variabilities in the encoder is then achieved by providing a reversable calibrating magnetic field close to the Hall effect switch and moving that magnetic field until the desired switch calibration is achieved.

Claims

1. The method of fabricating a magnetic-encoding device having a Hall effect switch and a rotatable disc-shaped actuating magnet comprising the steps of forming an integral frame with at least two component-locating positions, one of said component-locating positions being sized to receive snugly a Hall effect switch, fitting such a switch onto said one position thereby locating said switch-relative to the second of said two positions, forming a disc-shaped permanent magnet with circumferentially alternating poles on its periphery and a predetermined outer diameter, mounting said magnet for rotation about its axis to said second position with its periphery adjacent to said Hall effect switch, said second portion serving to locate said magnet relative to said switch whereby said frame and said two component-locating positions serve to locate and position said switch and magnet relative to each other with a minimum of dimensional tolerance therebetween.

2. The method of claim 1 including the step of mounting a magnet-mounting post on said second position, said second position and said post having been preformed to fit together with predetermined dimensional tolerance, and mounting said magnet on said post.

3. The method of claim 1 wherein said first position is a cavity shaped to receive and to locate said switch said second position being a hole sized to receive a post or shaft on which said magnet is mounted.