Variable transformer position sensor

• US 5,216,364 A
• Filed: 01/11/1989
• Issued: 06/01/1993
• Est. Priority Date: 01/11/1989
• Status: Expired due to Term

• Current Assignee: Uusi LLC (Nartron Corporation)
• Original Assignee: Nartron Corporation
• Inventors: Shank, David, Ko, Clyde, Munch, Carl
• Primary Examiner(s): Snow, Walter
• Application Number:
  US07/296,183
• Time in Patent Office: 1,602 Days
• Field of Search: 324/207, 324/208, 324/225, 324/226, 324/262, 324/207.16, 324/207.17, 324/207.24, 324/207.22, 340/870.31, 340/870.36, 336/45, 336/73, 336/75, 336/77, 336/84 R, 336/130, 336/132, 336/133, 336/136
• US Class Current: 324/207.24
• CPC Class Codes: B60G 17/01933 Velocity, e.g. relative velocity-displacement sensors
• CPC Class Codes: B60G 2204/111 on pneumatic springs
• CPC Class Codes: B60G 2204/112 on dampers, e.g. fluid dampers
• CPC Class Codes: B60G 2400/202 Piston speed; Relative velocity between vehicle body and wheel
• CPC Class Codes: B60G 2400/25 Stroke; Height; Displacement
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2401/17 Magnetic/Electromagnetic
• CPC Class Codes: F15B 15/2861 using magnetic means
• CPC Class Codes: G01D 5/2046 by a movable ferromagnetic element, e.g. a core
• CPC Class Codes: G01D 5/2053 by a movable non-ferromagnetic conductive element

Abstract

A linear position sensor includes coextensively positioned primary and secondary windings, each having an elongated core and a coil radially spaced around the core. A cyclically varying signal is applied to the primary winding which develops a signal across the secondary winding due to transformer coupling. A coupling adjustment member varies the amount of transformer coupling and is longitudinally movable with respect to the winding assembly. The relative longitudinal positioning of the coupling member with respect to the winding assembly is determined by measuring the signal developed across the secondary winding. In one embodiment, the windings are similarly configured, are arranged side-by-side and spaced apart; the coupling adjustment member enhances the transformer coupling between the windings which are telescopingly received within the member. In another embodiment, one winding is concentrically positioned within the other and the coupling adjustment member disrupts the transformer coupling between the windings by being positionable in a gap between the windings. Embodiments are illustrated both for location internal to, and external of, a vehicle shock absorber.

Claims

1. A linear position sensor system comprising:

a sensor member having electrical connection terminals;

an electronic assembly interconnected with said electrical connection terminals and including a sine wave generator for applying a sine wave signal to said terminals and measuring means for measuring an electrical parameter of said sensor at said terminals;

adjustment means movable with the member whose position is to be sensed for proportionally adjusting the value of said electrical parameter;

said sine wave generator including means for generating a square wave signal at a square wave generator output and a low-pass filter between said square wave generator output and said electrical connection terminals for shunting high frequency signals away from the square wave generator output;

said low pass filter including an amplifier having an inverting input, an amplifier output, a resistor between said amplifier output and said inverting input, a first capacitor between said square wave generator output and said inverting input and a second capacitor between said square wave generator output and said amplifier output.

2. The sensor in claim 1 in which said sensor and said electronic assembly are combined within a common housing.

3. The sensor in claim 2 in which said common housing comprises said sensor and said electronic assembly being commonly enclosed to provide an environmentally resistant assembly.

4. The sensor in claim 1 in which said measuring means includes rectifying means for rectifying said electrical parameter and means for applying a DC offset to the rectified electrical parameter.

5. The sensor in claim 4 in which said rectifying means includes an amplifier having an inverting input and an output and a diode between said amplifier input and output.

6. A linear position sensor comprising:

a winding assembly including an elongated primary winding and an elongated secondary winding, said windings being spaced apart and coextensively positioned within a common housing, each of said windings including an elongated core and a coil radially wound around the respective said core;

a tubular member having a cylindrical wall made from a nonferrous metal adapted to telescopingly receive a portion of said winding assembly within said wall;

an electronic assembly joined with said winding assembly within said common housing and having generating means for generating a cyclically varying signal, said signal being applied to said primary winding and measuring means for measuring the signal developed across said secondary winding, said signal being proportional to the length of said winding assembly portion within the cylindrical wall of said tubular member; and

a boot sealingly joining said tubular member and said winding assembly.

7. The sensor in claim 6 in which said generating means includes a square wave generating means for generating a square wave signal and low pass filtering means for passing only components of said square wave signal below a predetermined frequency.

8. The sensor in claim 7 in which said low pass filtering means includes shunting means for shunting components of said square wave signal above said predetermined frequency to ground.

9. A linear position sensor comprising:

a winding assembly including an elongated primary winding and an elongated secondary winding, each of said windings including an elongated core and a coil radially wound around the respective said core having a preestablished non-constant turn spacing, said secondary winding core including wall means defining a central bore extending axially along the direction of elongation of said secondary winding, said bore having an inner diameter larger than the outer diameter of said primary winding, said primary winding positioned within said bore defining an annular cavity between said windings,

a tubular member having a cylindrical wall made from a magnetic material and adapted to be longitudinally adjustable positioned within said annular cavity, and

means for activating a primary coil winding with an energization signal and for sensing an output from the secondary coil,

said pre-established non-constant turn spacing providing a substantially linear response related to movement of the tubular member.

10. The sensor in claim 9 wherein said means for activating comprises an electronic assembly having generating means for generating a cyclically varying signal, said signal being applied to said primary winding and measuring means for measuring the signal developed across said secondary winding, said signal being inversely proportional to the length of said tubular member within said winding assembly annular cavity.

11. The sensor in claim 10 in which said generating means includes a square wave generating means for generating a square wave signal and low pass filtering means for passing only components of said square wave signal below a predetermined frequency.

12. The sensor in claim 11 in which said low pass filtering means includes shunting means for shunting components of said square wave signal above said predetermined frequency to ground.

13. A linear position sensor comprising:

a primary winding having a first elongated core and a coil wound around said core;

a secondary winding having a second elongated core substantially coextensive with said first core and a coil radially wound around said second core;

coupling adjustment means movable with a member whose position is to be sensed and with respect to said windings for varying the transformer coupling between said windings;

a tubular shaped frame member having inner surface means defining a bore, said windings being positioned in said bore;

said coupling adjustment means slidable within said bore and including an inner metallic member fitted within an outer polymer support member; and

anti-friction means including ribs extending from and annularly spaced around said outer polymer support member and said inner surface means.

14. A linear position sensor comprising:

a primary winding having a first elongated core and a coil wound around said core;

a secondary winding having a second elongated core substantially coextensive with said first core and a coil radially wound around said second core;

coupling adjustment means movable with a member whose position is to be sensed and with respect to said windings for varying the transformer coupling between said windings;

a tubular shaped frame member having inner surface means defining a bore, said windings being positioned in said bore;

said coupling adjustment means slidable within said bore and including an inner metallic member fitted within an outer support member; and

anti-friction means between said outer support member and said inner surface

said tubular shaped frame member including means defining a plurality of openings spaced along said tubular frame to allow pressure within said bore to equalize as said coupling adjustment means moves therein.

15. A linear position sensor comprising:

a primary winding having a first elongated core and a coil wound around said core;

a secondary winding having a second elongated core substantially coextensive with said first core and a coil radially wound around said second core;

coupling adjustment means movable with a member whose position is to be sensed and with respect to said windings for varying the transformer coupling between said windings;

a tubular shaped frame member having inner surface means defining a bore, said windings being positioned in said bore;

said coupling adjustment means slidable within said bore and including an inner metallic member fitted within an outer support member;

anti-friction means between said outer support member and said inner surface; and

a boot extending between said tubular frame member and said coupling adjustment means.

16. A linear position sensor comprising:

a primary winding having a first elongated core and a coil radially wound around said core including a multiplicity of turns spaced substantially along the length of said core;

a secondary winding having a second elongated core substantially coextensive with said first core and a coil radially wound around said second core including a multiplicity of turns spaced substantially along the length of said second core; and

coupling adjustment means movable with a member whose position is to be sensed and with respect to said windings for varying a transformer coupling between said windings;

said primary and secondary windings being parallel and spaced apart and said coupling adjustment means includes a coupling enhancing member around said coils such that a signal developed in said secondary winding as a result of exciting the primary winding increases as the coupling enhancing member overlaps a greater extent of said primary and secondary windings;

wherein said coupling enhancing member comprises a current conducting tubular member.

17. The sensor in claim 16 in which said tubular member is made from a nonferrous metal.

18. The sensor in claim 18 in which said cores are made from ferromagnetic material.

19. A linear position sensor comprising:

a primary winding having a first elongated core and a coil radially wound around said core including a multiplicity of turns spaced substantially along the length of said core;

a secondary winding having a second elongated core substantially coextensive with said first core and a coil radially wound around said second core including a multiplicity of turns spaced substantially along the length of said second core; and

coupling adjustment means movable with a member whose position is to be sensed and with respect to said windings for varying a transformer coupling between said windings;

said primary and secondary windings being parallel and spaced apart and said coupling adjustment means includes a coupling enhancing member around said coils such that a signal developed in said secondary winding as a result of exciting the primary winding increases as the coupling enhancing member overlaps a greater extent of said primary and secondary windings;

wherein said core are made from ferromagnetic material.

20. A linear position sensor comprising:

a primary winding having a first elongated core and a coil radially wound around said core including a multiplicity of turns spaced substantially along the length of said core;

a secondary winding having a second elongated core substantially coextensive with said first core and a coil radially wound around said second core including a multiplicity of turns spaced substantially along the length of said second core;

coupling adjustment means movable with a member whose position is to be sensed and with respect to said windings for varying a transformer coupling between said windings;

said primary and secondary windings being parallel and spaced apart and said coupling adjustment means includes a coupling enhancing member around said coils such that a signal developed in said secondary winding as a result of exciting the primary winding increases as the coupling enhancing member overlaps a greater extent of said primary and secondary windings; and

means for applying a cyclically varying signal to said primary winding and measuring means for measuring the signal developed across said secondary winding coupled from said primary winding.

21. A linear position sensor comprising:

a primary winding having a first elongated core and a coil radially wound around said core including a multiplicity of turns spaced substantially along the length of said core;

a secondary winding having a second elongated core substantially coextensive with said first core and a coil radially wound around said second core including a multiplicity of turns spaced substantially along the length of said second core; and

coupling adjustment means movable with a member whose position is to be sensed and with respect to said windings for varying a transformer coupling between said windings;

said primary and secondary windings being parallel and spaced apart and said coupling adjustment means includes a coupling enhancing member around said coils such that a signal developed in said secondary winding as a result of exciting the primary winding increases as the coupling enhancing member overlaps a greater extent of said primary and secondary windings;

wherein said windings are encapsulated in a common package.

22. The sensor in claim 21 further including an electronic module said module having means for generating a cyclically varying signal and applying said cyclically varying signal to said primary winding and means for measuring the signal developed across said secondary winding coupled from said primary winding.