Claims
- 1. A stroke sensor for detecting a stroke position of a movable member linearly movable relative to a body within a space formed in said body, said stroke sensor comprising:a sensor member having one end supported in a cantilever fashion adjacent a predetermined end of said body and having another end extending into the space of said body, said movable member having an inner space formed therein to permit entry of said sensor member into said movable member; a coil section having a plurality of coil segments excitable by a predetermined A.C. signal and sequentially arranged along a direction of linear movement of said movable member, said coil section being provided on one of said sensor member and an inner peripheral wall of said movable member defining said inner space; and a magnetism-responsive substance provided on other of said sensor member and the inner peripheral wall of said movable member defining said inner space in such a manner that said magnetism-responsive substance is movable relative to said coil section, wherein relative positions of said magnetism-responsive substance and said coil section vary in accordance with a stroke position of said movable member, in response to which respective inductance of said coil segments are caused to vary in such a manner that during movement of said magnetism-responsive substance from one end to another of a particular one of said coil segments, a voltage across the particular coil segment is caused to progressively decrease or increase.
- 2. A stroke sensor as claimed in claim 1 which further comprises an arithmetic operator that takes out the respective voltages of said coil segments and performs addition and/or subtraction between the voltages of said coil segments to thereby generate an A.C. output signal presenting a particular amplitude based on a predetermined cyclic function characteristic in accordance with the stroke position of said movable member.
- 3. A stroke sensor as claimed in claim 2 wherein said arithmetic operator generates a plurality of A.C. output signals presenting particular amplitudes based on predetermined cyclic function characteristics in accordance with the stroke position of said movable member, and the cyclic function characteristics defining respective ones of the amplitudes of the plurality of A.C. output signals comprising cyclic functions of a same characteristic which are shifted from each other by a predetermined phase amount.
- 4. A stroke sensor as claimed in claim 3 which further comprises an amplitude-to-phase conversion section that receives the plurality of A.C. output signals generated by said arithmetic operator and detects, from a correlation between amplitude values in the plurality of A.C. output signals, particular phase values in the predetermined cyclic functions defining the amplitude values, to generate data indicative of the position of said movable member to be detected on the basis of the detected particular phase values.
- 5. A stroke sensor as claimed in claim 3 wherein said plurality of A.C. output signals include an A.C. output signal presenting an amplitude of a sine function characteristic in accordance with the stroke position of said movable member and an A.C. output signal presenting an amplitude of a cosine function characteristic in accordance with the stroke position of said movable member.
- 6. A stroke sensor as claimed in claim 1 wherein said coil section is provided on said sensor member and said magnetism-responsive substance is provided on the inner peripheral wall of said movable member defining said inner space.
- 7. A stroke sensor as claimed in claim 6 wherein said sensor member includes a bobbin section containing a magnetic body and each of said coil segments of said coil section is fitted in said bobbin section.
- 8. A stroke sensor as claimed in claim 7 wherein said bobbin section includes a cylindrical portion made of a nonmagnetic material, and one or more magnetic rods received within said cylindrical portion.
- 9. A stroke sensor as claimed in claim 6 wherein said magnetic body or each of said one or more magnetic rods has an electrically-conductive coating formed thereon.
- 10. A stroke sensor as claimed in claim 6 wherein said sensor member includes a core rod having said coil section fitted therein, and a magnetic spacer interposed between opposed ends of each adjoining pair of said coil segments.
- 11. A stroke sensor as claimed in claim 6 wherein a material of said movable member itself comprises said magnetism-responsive substance.
- 12. A stroke sensor as claimed in claim 1 wherein said magnetism-responsive substance includes at least one of a magnetic material and an electrically-conductive material.
- 13. A stroke sensor as claimed in claim 1 wherein said coil section comprises substantially a single coil extending along the direction of linear movement of said movable member, and a plurality of output terminals are provided at predetermined intermediate positions of the single coil so that said plurality of coil segments are formed by said single coil.
Priority Claims (3)
Number |
Date |
Country |
Kind |
11-69229 |
Mar 1999 |
JP |
|
11-249755 |
Sep 1999 |
JP |
|
11-249768 |
Sep 1999 |
JP |
|
RELATED APPLICATION
This application is a continuation-in-part application of our corresponding U.S. application Ser. No. 09/525,281 filed Mar. 14, 2000, which is now pending.
US Referenced Citations (5)
Foreign Referenced Citations (6)
Number |
Date |
Country |
0 759 539 |
Feb 1997 |
EP |
0 795 738 |
Sep 1997 |
EP |
2-26003 |
Jul 1990 |
JP |
10126241 |
May 1998 |
JP |
10-153203 |
Jun 1998 |
JP |
10170210 |
Jun 1998 |
JP |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
09/525281 |
Mar 2000 |
US |
Child |
09/653424 |
|
US |