Self-induction-type position detector device for detecting object position

• US 20030102862A1
• Filed: 12/31/2002
• Published: 06/05/2003
• Est. Priority Date: 03/15/1999
• Status: Active Grant

• Current Assignee: Amiteq Co., Ltd.
• Original Assignee: Atsutoshi Goto
• Inventors: Sakamoto, Kazuya, Sakamoto, Hiroshi, Goto, Atsutoshi
• Granted Patent: US 6,707,291 B2
• Time in Patent Office: Days
• US Class Current: 324/207.16
• CPC Class Codes: G01D 2205/73 Targets mounted eccentrically with respect to the axis of rotation
• CPC Class Codes: G01D 3/0365 the undesired influence being measured using a separate sensor, which produces an influence related signal
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence

Abstract

Single coil to be excited by a predetermined A.C. signal is provided, with no secondary coil being provided. Magnetism-responsive member is movable relative to the coil so that a self-inductance of the coil progressively increases or decreases in response to displacement of an object to be detected within a predetermined range and a voltage of the coil corresponding to the self-inductance is produced. Predetermined reference voltage is generated and subjected to analog operations with the coil output voltage, to thereby generate first and second A.C. outputs having, as amplitude coefficients, first and second cyclic amplitude functions correlated to the position to be detected. The position is detected on the basis of the phase component of the amplitude coefficient functions. Combination of two coils and one reference voltage may be employed. Further, a plurality of coil segments excitable by a same-phase signal are placed in series along the direction of displacement of the object so that a progressive increase or decrease occurs sequentially in the self-inductance of the coil segments as the magnetism-responsive member moves relative to the coil segments, and the voltage corresponding to the self-inductance is taken out from each of the coil segments. Performing analog arithmetic operations on combinations of the coil voltages produces first and second A.C. outputs having, as amplitude coefficients, first and second cyclic amplitude functions correlated to the position to be detected.

Claims

1. A position detector device comprising:

a coil section including at least one coil to be excited by an A.C. signal;

a magnetism-responsive member movable relative to said coil section, wherein relative positions between said magnetism-responsive member and said coil section vary in response to displacement of an object to be detected and impedance of said coil is caused to vary in response to a variation in the relative positions in such a manner that a voltage produced in said coil is caused to vary in response to a variation in the impedance of said coil during the variation in the relative positions within a predetermined range;

a reference-voltage generation circuit adapted to generate at least one predetermined reference voltage in the form of an A.C. signal; and

an arithmetic operation circuit coupled to said coil and reference-voltage generation circuit, said arithmetic operation circuit adapted to perform an arithmetic operation between said voltage produced in said coil and said predetermined reference voltage, so as to generate at least two A.C. output signals having predetermined cyclic amplitude functions as amplitude coefficients, the cyclic amplitude functions of the two A.C. output signals being different, in their cyclic characteristics, from each other by a predetermined phase.

2. A position detector device as claimed in claim 1 wherein said coil section includes a single coil,

said reference-voltage generation circuit generates first and second reference voltages, and

said arithmetic operation circuit performs predetermined first and second arithmetic operations using a voltage produced in said single coil and said first and second reference voltages, to thereby generate a first A.C. output signal having a first amplitude function as an amplitude coefficient and a second A.C. output signal having a second amplitude function as an amplitude coefficient.

3. A position detector device as claimed in claim 2 wherein said first and second reference voltages define specific phase sections in cyclic characteristics of said first and second amplitude functions of said first and second A.C. output signals, and wherein correspondence between the specific phase sections and a variation range of the relative positions can be varied by varying said first and second reference voltages.

4. A position detector device as claimed in claim 1 wherein said coil section includes two coils, positions of the two coils relative to said magnetism-responsive member being caused to vary with opposite characteristics in response to the displacement of the object to be detected, in response to which respective impedance of the two coils varies with opposite characteristics,

said reference-voltage generation circuit generates a single reference voltage, and

said arithmetic operation circuit performs predetermined first and second arithmetic operations using respective voltages produced in said coils and the reference voltage, to thereby generate a first A.C. output signal having a first amplitude function as an amplitude coefficient and a second A.C. output signal having a second amplitude function as an amplitude coefficient.

5. A position detector device as claimed in claim 1 wherein said reference-voltage generation circuit includes a coil of predetermined impedance which is positioned so as not to be influenced by a movement of said magnetism-responsive member.

6. A position detector device as claimed in claim 1 wherein said coil includes a magnetic core and said magnetism-responsive member has a flat surface that is opposed to said magnetic core of said coil with an air gap interposed therebetween, and wherein as the flat surface of said magnetism-responsive member moves in response to a changing position of the object to be detected, there occurs a dimensional variation in the air gap which brings about a variation in the impedance of said coil.

7. A position detector device as claimed in claim 1 wherein said coil includes a magnetic core, and the impedance of said coil is caused to vary as a distance defined by an air gap between said magnetic core and said magnetism-responsive member or an area of the air gap varies in response to a changing position of the object to be detected.

8. A position detector device as claimed in claim 2 wherein said first and second amplitude functions are sine and cosine functions, respectively.

9. A position detector device as claimed in claim 1 wherein said magnetism-responsive member includes at least one of a magnetic substance and an electrically-conductive substance.

10. A position detector device as claimed in claim 1 wherein said magnetism-responsive member includes a permanent magnet and said coil section includes a magnetic core.

11. A rotary-type position detector device comprising:

a coil section including at least one coil to be excited by an A.C. signal;

a magnetism-responsive member rotationally movable relative to said coil section, wherein relative rotational positions between said magnetism-responsive member and said coil section varies in response to rotational displacement of an object to be detected and impedance of said coil is caused to vary in response to a variation in the relative rotational positions between said magnetism-responsive member and said coil section in such a manner that a voltage produced in said coil is caused to vary in response to a variation in the impedance of said coil during the variation in the relative rotational positions within a predetermined rotational angle range;

a reference-voltage generation circuit adapted to generate a predetermined reference voltage; and

an arithmetic operation circuit coupled to said coil and reference-voltage generation circuit, said arithmetic operation circuit adapted to perform an arithmetic operation between said voltage produced in said coil and said predetermined reference voltage, so as to generate at least two A.C. output signals having predetermined cyclic amplitude functions as amplitude coefficients, the cyclic amplitude functions of the two A.C. output signals being different, in their cyclic characteristics, from each other by a predetermined phase.

12. A rotary-type position detector device as claimed in claim 11 wherein said coil section includes two coils positioned to be apart from each other by a predetermined angle along a direction of variation of the relative rotational positions,

said reference-voltage generation circuit generates a reference voltage corresponding to a center point of variation in a voltage produced in each of said two coils, and

said arithmetic operation circuit subtracts the reference voltage from the voltage produced in a first one of said two coils to thereby generate a first A.C. output signal having, as an amplitude coefficient, a first cyclic amplitude function swinging about the center point of variation in positive and negative directions, and subtracts the reference voltage from the voltage produced in a second one of said two coils to thereby generate a second A.C. output signal having, as an amplitude coefficient, a second cyclic amplitude function swinging about the center point of variation in the positive and negative directions.

13. A rotary-type position detector device as claimed in claim 11 wherein said arithmetic operation circuit performs predetermined first and second arithmetic operations using the voltage produced in said coil and the reference voltage, to thereby generate a first A.C. output signal having a first amplitude function as an amplitude coefficient and a second A.C. output signal having a second amplitude function as an amplitude coefficient.

14. A rotary-type position detector device as claimed in claim 11 wherein said reference-voltage generation circuit includes a coil of predetermined impedance which is positioned so as not to be influenced by a movement of said magnetism-responsive member.

15. A rotary-type position detector device as claimed in claim 11 wherein said coil section is provided in a predetermined limited angular range less than one full rotation of the object to be detected.

16. A rotary-type position detector device as claimed in claim 11 wherein each of the coils in said coil section includes a magnetic core, and the impedance of each of the coils is caused to vary as a distance defined by an air gap between said magnetic core and said magnetism-responsive member or an area of the air gap varies in response to a changing rotational position of the object to be detected.

17. A rotary-type position detector device as claimed in claim 16 wherein said magnetic core of each of the coils in said coil section has an end oriented in a thrust direction of a rotation shaft that is the object to be detected, and the air gap between the end of said magnetic core and said magnetism-responsive member is defined with respect to the thrust direction of the rotation shaft.

18. A rotary-type position detector device as claimed in claim 16 wherein said magnetic core of each of the coils in said coil section has an end oriented in a radial direction of a rotation shaft that is the object to be detected, and the air gap between the end of said magnetic core and said magnetism-responsive member is defined with respect to the radial direction of the rotation shaft, whereby said magnetic core is unsusceptible to a mechanical shake of the rotation shaft.

19. A rotary-type position detector device comprising:

a coil section including at least two pairs of coils to be excited by an A.C. signal, the coils in each of the pairs being positioned to be apart from each other by a distance corresponding to a predetermined rotational angle;

a magnetism-responsive member rotationally movable relative to said coil section, wherein relative rotational positions between said magnetism-responsive member and said coil section vary in response to rotational displacement of an object to be detected and impedance of each of said coils is caused to vary in response to a variation in the relative rotational positions in such a manner that a voltage produced in each of said coils is caused to vary in response to a variation in the impedance of said coil during the variation in the relative rotational positions within a predetermined rotational angle range, the voltages produced in the respective coils in each of the pairs presenting differential characteristics; and

a circuit coupled to said coil section, said circuit adapted to generate, for each of said two pairs of coils, an A.C. output signal having a predetermined cyclic amplitude function as an amplitude coefficient, by taking out a difference in the voltages produced in said respective coils, the cyclic amplitude functions of the A.C. output signals generated for said two pairs of coils being different in their cyclic characteristics by a predetermined phase.

20. A position detector device comprising:

a coil section including a plurality of coil segments to be excited by a predetermined A.C. signal, the coil segments being placed in series along a direction of displacement of an object to be detected;

a magnetism-responsive member movable relative to said coil section, wherein relative positions between said magnetism-responsive member and said coil section vary in response to displacement of the object to be detected and impedance of each of said coil segments is caused to vary in response to a variation in the relative positions in such a manner that a voltage produced in each of said coil segments is caused to progressively increase or decrease during a movement of said magnetism-responsive member from one end to another of each of said coil segments; and

an analog arithmetic operation circuit coupled to said coil section, said analog arithmetic operation circuit adapted to generate a plurality of A.C. output signals presenting amplitudes based on predetermined cyclic function characteristics corresponding to a position of the object to be detected, by taking out voltages of said coil segments and performing addition and/or subtraction on the taken-out voltages, the cyclic function characteristics defining the amplitudes of the plurality of A.C. output signals comprising cyclic functions of a same character that are different from each other by a predetermined phase.

21. A position detector device as claimed in claim 20 which further comprises an amplitude-to-phase converter section that is adapted to receive said plurality of A.C. output signals generated via said analog arithmetic operation circuit, then detect, from a correlation between amplitude values of the A.C. output signals, a specific phase value in the predetermined cyclic functions defining the amplitude values, and then generate position detecting data indicative of a position of the object to be detected.

22. A position detector device as claimed in claim 20 wherein said plurality of A.C. output signals includes an A.C. output signal presenting an amplitude based on a sine function characteristic which corresponds to the position of the object to be detected, and an A.C. output signal presenting an amplitude based on a cosine function characteristic which corresponds to the position of the object to be detected.

23. A position detector device as claimed in claim 20 wherein said magnetism-responsive member includes at least one of a magnetic substance and an electrically-conductive substance.

24. A position detector device as claimed in claim 20 wherein said magnetism-responsive member includes a permanent magnet and said coil section includes a magnetic core.

25. A position detector device as claimed in claim 20 wherein said coil section includes a magnetic core.

26. A position detector device as claimed in claim 20 wherein said coil section is disposed around a bobbin, and said bobbin includes a cylindrical portion made of a non-magnetic substance and one or more magnetic rods received in said cylindrical portion.

27. A position detector device as claimed in claim 26 wherein each of said magnetic rods of said bobbin has an electrically-conductive coating formed on a surface thereof.

28. A position detector device as claimed in claim 20 wherein said coil section comprises substantially one coil running along the direction of displacement of the object to be detected, and said plurality of coil segments are formed of said one coil by providing output terminals at predetermined intermediate points of said one coil.

29. A position detector device comprising:

a coil to be excited by a predetermined A.C. signal;

a magnetism-responsive member movable relative to said coil, wherein relative positions between said magnetism-responsive member and said coil vary in response to displacement of an object to be detected and impedance of said coil is caused to vary in response to a variation in the relative positions between said magnetism-responsive member and said coil in such a manner that a voltage produced in said coil is caused to progressively increase or decrease during a movement of said magnetism-responsive member from one end to another of said coil;

an impedance element to be supplied with the predetermined A.C. signal; and

a circuit coupled to said coil and said impedance element, said cuircuit adapted to receive the voltage produced in said coil and a voltage produced in said impedance element and generate a plurality of A.C. output signals presenting amplitudes based on predetermined cyclic function characteristics corresponding to a position of the object to be detected on the basis of the received voltages, the cyclic function characteristics defining the amplitudes of the plurality of A.C. output signals comprising cyclic functions of a same character that are different from each other by a predetermined phase.

30. A position detector device comprising:

a coil section including a plurality of coil segments to be excited by a predetermined A.C. signal, the coil segments being placed in series along a direction of displacement of an object to be detected;

a magnetism-responsive member movable relative to said coil section, wherein relative positions between said magnetism-responsive member and said coil section varies in response to displacement of the object to be detected and impedance of each of said coil segments is caused to vary in response to a variation in the relative positions between said magnetism-responsive member and said coil section in such a manner that a voltage produce in each of said coil segments is caused to progressively increase or decrease during a movement of said magnetism-responsive member from one end to another of each of said coil segments; and

an analog arithmetic operation circuit coupled to said coil section, said analog arithmetic operation circuit adapted to generate an A.C. output signal presenting an amplitude based on a predetermined cyclic function characteristic corresponding to a position of the object to be detected, by taking out voltages of said coil segments and performing addition and/or subtraction on the taken-out voltages.

31. A position detector device comprising:

a magnet; and

a coil section movable relative to said magnet and including a magnetic core extending along a direction of relative movement thereof to said magnet, said coil section being excitable by an A.C. signal and positioned in such a manner that magnetic saturation is produced at a predetermined portion of said magnetic core that is strongly affected by a magnetic flux from said magnet, and

wherein one of said magnet and said coil section is placed on a given moving section whose position is to be detected as an object to be detected while other of said magnet and said coil section is fixed in position, and relative positions between said magnet and said coil section vary in response to displacement of said moving section, in response to which the predetermined portion of said magnetic core where the magnetic saturation is produced is shifted and said coil section generates an output signal corresponding to a shift in the predetermined portion of said magnetic core where the magnetic saturation is produced.

32. A position detector device as claimed in claim 31 wherein said coil section includes primary and secondary coils, and a plurality of the secondary coils are provided in corresponding relation to different areas of said magnetic core, and wherein an inductive A.C. output signal amplitude-modulated in accordance with the relative positions between said magnet and said coil section is produced from each of said secondary coils with an amplitude function characteristic differing in correspondence with a difference in respective positions of said secondary coils.

33. A position detector device as claimed in claim 31 wherein a first inductive A.C. output signal having an amplitude function of a sine function and a second inductive A.C. output signal having an amplitude function of a cosine function are generated via said coil section.

34. A position detector device as claimed in claim 31 which further comprises a phase detector circuit that receives said first inductive A.C. output signal and said second inductive A.C. output signal and detects a phase value of the sine and cosine functions corresponding to amplitude values of said inductive A.C. output signals.