Angular position sensor working to measure high linearity magnetic flux density
First Claim
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1. An angular position sensor comprising:
- a hard magnetic member connected to a rotary member, said hard magnetic member having a circumference and magnetized in a circumferential direction thereof to produce a magnetic field therearound;
a soft magnetic member disposed within the magnetic field produced by said hard magnetic member to form a magnetic circuit, rotation of the rotary member to change a relative position between the magnetic field and said hard magnetic member causes a magnetic flux density in the magnetic circuit to change; and
a magnetic flux density measuring sensor disposed at an interval away from said soft magnetic member, said magnetic flux density measuring sensor working to measure the magnetic flux density in the magnetic circuit to produce a signal as a function of the magnetic flux density as indicating an angular position of the rotary member, wherein said hard magnetic member is so designed as to create magnetic flux that is substantially uniform in amount within a given angular range in a circumferential direction thereof.
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Abstract
An angular position sensor is provided which is designed to an angular position of a rotary shaft. The angular position sensor has a magnet affixed to the rotary shaft. The magnet has an N-pole and an S-pole and is so geometrically shaped as to produce magnetic flux which is substantially uniform in amount within a range extending around each of centers of the N-pole and the S-pole. This improves the linearity of a change in sensor output upon rotation of the rotary shaft.
35 Citations
20 Claims
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1. An angular position sensor comprising:
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a hard magnetic member connected to a rotary member, said hard magnetic member having a circumference and magnetized in a circumferential direction thereof to produce a magnetic field therearound;
a soft magnetic member disposed within the magnetic field produced by said hard magnetic member to form a magnetic circuit, rotation of the rotary member to change a relative position between the magnetic field and said hard magnetic member causes a magnetic flux density in the magnetic circuit to change; and
a magnetic flux density measuring sensor disposed at an interval away from said soft magnetic member, said magnetic flux density measuring sensor working to measure the magnetic flux density in the magnetic circuit to produce a signal as a function of the magnetic flux density as indicating an angular position of the rotary member, wherein said hard magnetic member is so designed as to create magnetic flux that is substantially uniform in amount within a given angular range in a circumferential direction thereof. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An angular position determining apparatus comprising:
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an angular position sensor including (a) a hard magnetic member connected to a rotary member, said hard magnetic member having a circumference and magnetized in a circumferential direction thereof to produce a magnetic field therearound and working to produce magnetic flux that is substantially uniform in amount within a given angular range in a circumferential direction thereof, said hard magnetic member having a first magnetic pole and a second magnetic pole different in polarity from the first magnetic pole, the first and second magnetic poles being jointed at ends thereof at locations 180°
apart from each other in a circumferential direction of said hard magnetic member, (b) a soft magnetic member disposed outside the circumference of said hard magnetic member within the magnetic field produced by said hard magnetic member to form a magnetic circuit, rotation of the rotary member to change a relative position between the magnetic field and said hard magnetic member causes a magnetic flux density in the magnetic circuit to change, said soft magnetic member having gaps formed therein at an interval of approximately 90°
, and (c) a magnetic flux density measuring sensor including a first and a second sensor element respectively disposed in two of the gaps adjacent in the circumferential direction of said soft magnetic member, the first and second sensor elements working to measure magnetic flux densities within the two gaps and produce electric signals indicative thereof; and
an angular position computing circuit working to computing an angular position of the rotary member based on the electric signals produced by said magnetic flux density measuring sensor. - View Dependent Claims (13, 14, 15)
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16. An angular position determining apparatus comprising:
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a ring-shaped hard magnetic member connected to a rotary member, said hard magnetic member including a first magnetic pole and a second magnetic pole different in polarity from the first magnetic pole, the first and second magnetic poles being jointed at ends thereof at locations 180°
apart from each other in a circumferential direction of said hard magnetic member, said hard magnetic member being so designed as to create magnetic flux that is substantially uniform in amount within a given angular range in a circumferential direction thereof;
a soft magnetic member disposed outside a circumference of said hard magnetic member having formed therein gaps arrayed at an interval of approximately 90°
, rotation of the rotary member to change a relative position between said hard magnetic member and said soft magnetic member causes a magnetic flux density in the gaps to change;
magnetic flux density measuring sensors disposed one in each of two of the gaps adjacent in a direction of array of the gaps, said magnetic flux density measuring sensors working to magnetic flux densities within the two gaps and produce electric signals indicative thereof which exhibit substantially triangular waves shifted 90°
apart in phase from each other and each of which has a straight portion; and
an angular position computing circuit working to combine and correct the straight portions of said triangular waves to form a substantially single straight line, said angular position computing circuit computing an angular position of the rotary member using the straight line. - View Dependent Claims (17, 18, 19, 20)
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Specification