Position sensor incorporating a permanent magnet and a magnetism-sensitive probe and including primary and secondary air gaps

• US 5,532,585 A
• Filed: 05/20/1994
• Issued: 07/02/1996
• Est. Priority Date: 05/19/1992
• Status: Expired due to Term

• Current Assignee: MMT SA
• Original Assignee: Moving Magnet Technologies SA (Société industrielle de Sonceboz SA)
• Inventors: Prudham, Daniel, Oudet, Claude
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US08/182,039
• Time in Patent Office: 774 Days
• Field of Search: 324/207.11, 324/207.13, 324/207.14, 324/207.15, 324/207.20, 324/207.21, 324/207.22, 324/207.23, 324/207.24, 324/207.25, 324/232 , 324/235, 324/239, 324/260, 324/262
• US Class Current: 324/207.22
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A position sensor which includes a stator presenting a slot forming a main air-gap inside which is positioned a permanent magnet, and including a sensor which features a magnetism-sensitive probe for measuring magnetic flow formed in a secondary air-gap. The permanent magnet is of a bipolar type and is movable inside the main thin air-gap delimited by ferromagnetic parts joined by non-magnetic connecting parts. The length of the main air-gap as measured along the direction of displacement of the movable magnet is at least 2(C+E), C designating the travel of the magnet and E designating the width of the main air-gap, the length of the magnet further being at least equal to (C+E) and its travel being at least ±C/2 with respect to the secondary air-gap perpendicular to the main air-gap.

Claims

1. A position sensor comprising:

first and second ferromagnetic components connected by at least one non-magnetic connection element, the first and second ferromagnetic components defining a principal air gap;

a permanent magnet formed to travel in the principal air gap;

a secondary air gap formed perpendicular to the principal air gap;

an induction measurement device including a magnetism sensitive probe formed in the secondary air gap; and

wherein a length of the principal air gap as measured in a direction of the travel of the permanent magnet is at least equal to 2(C+E), where C is a course of travel of the permanent magnet and E is a width of the principal air gap, and a length of the permanent magnet is at least equal to (C+E) and the course of travel of the permanent magnet is equal to (+C/2)+(-C/2) relative to the secondary air gap.

2. The position sensor according to claims 1, wherein said two ferromagnetic components are connected by at least one non-magnetic lateral flange.

3. The position sensor according to claim 1, wherein said permanent magnet travels inside a fluid-tight tubular element.

4. The position sensor according to claim 1, wherein said permanent magnet is enclosed in a sheath of a material having a low coefficient of friction.

5. The position sensor according to claim 4, wherein the sheath of material is Teflon.

6. The position sensor according to claim 1, wherein a width Z of the permanent magnet as measured along an axis perpendicular to a direction of its magnetization is greater than or equal to 3L, where L is a length of the magnet as measured in the direction of its magnetization.

7. The position sensor according to any one of claims 1-4, wherein said permanent magnet is an annular magnet and can rotate freely.

8. The position sensor according to claim 1, further comprising a movable mechanism including a bearing incorporating on an upper part a clamp allowing coupling of a connection rod, said bearing sliding on the first ferromagnetic component incorporating a flat part and a cavity which positions the permanent magnet parallel to said flat part, said second ferromagnetic component being positioned adjacent to an outer surface of a bottom of a housing made of a non-magnetic material, said secondary air gap further being perpendicular to the direction of travel of said movable mechanism.

9. The position sensor according to claim 8, wherein said connection rod comprises two stops and a spring arranged respectively between the front stop and a shoulder belonging to the connection rod.