Rotation angle sensor having improved magnetic leakage effect prevention and reduction in parts

• US 6,268,722 B1
• Filed: 03/17/1999
• Issued: 07/31/2001
• Est. Priority Date: 03/17/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Unisia Jecs Corporation (Hitachi, Ltd.)
• Inventors: Kogure, Yoshihiro, Nakazawa, Hirotsugu
• Primary Examiner(s): Oda, Christine
• Assistant Examiner(s): Zaveri, Subhash
• Application Number:
  US09/271,161
• Time in Patent Office: 867 Days
• Field of Search: 324/207.2, 324/207.25, 324/207.21, 324/207.22, 324/207.12, 338/32.R, 338/32.M
• US Class Current: 324/207.25
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A rotation angle sensor is provided, including a casing, and a magnet positioned in the casing. The magnet has a first magnetic pole end and a second magnetic pole end. First and second yokes are positioned at a first predetermined space relative to the first magnetic pole end of the magnet, and a third yoke is positioned at a predetermined space relative to the second magnetic pole end of the magnet. The third yoke is further positioned between the magnet and an extending portion of the first yoke, and is also positioned between the magnet and an extending portion of the second yoke. A first signal output element, which is positioned between the third yoke and the extended portion of the first yoke, outputs a first signal corresponding to an area ratio between the magnet and the first yoke. A second signal output element, which is positioned between the third yoke and the extended portion of the second yoke, outputs a second signal corresponding to an area ratio between the magnet and the second yoke. In addition, a magnetic shielding portion is positioned above the magnet, wherein the magnetic shielding portion interrupts leakage magnet flux of the magnet, and wherein the magnetic shielding portion and the third yoke are integrally formed of a single-piece construction.

Claims

1. A rotation angle sensor, comprising:

a) a casing;

b) a magnet positioned in said casing, said magnet having a first magnetic pole end and a second magnetic pole end;

c) first and second yokes positioned at a first predetermined space relative to the first magnetic pole end of said magnet;

d) a third yoke positioned at a predetermined space relative to the second magnetic pole end of said magnet, said third yoke further positioned between said magnet and an extending portion of said first yoke, and positioned between said magnet and an extending portion of said second yoke;

e) a first signal output element positioned between said third yoke and said extended portion of said first yoke, said first signal output element for outputting a first signal corresponding to an area ratio between said magnet and said first yoke,

f) a second signal output element positioned between said third yoke and said extended portion of said second yoke, said second signal output element for outputting a second signal corresponding to an area ratio between said magnet and said second yoke; and

g) a magnetic shielding portion positioned above said magnet, wherein said magnetic shielding portion interrupts leakage magnet flux of said magnet,

wherein said magnetic shielding portion has a substantially semicircular shape and said third yoke are integrally formed of a single-piece construction.

2. The rotation angle sensor as defined in claim 1, wherein said second magnetic pole end of said magnet has a substantially circular facing, said third yoke comprises

a substantially a circular magnet portion extending, at the predetermined space, relative to said circular facing of said second magnetic pole end.

3. The rotation angle sensor as defined in claim 2, wherein said first and second yokes each comprise a circular magnet portion, and said extending portions of said first and second yokes extend from said circular magnet portions of said first and second yokes, respectively, along a direction of a perimeter of said circular magnet portion of said third yoke.

4. The rotation angle sensor as defined in claim 2, wherein said circular magnet portion of said third yoke is radially positioned between said magnet and said extending portion of said first yoke, and also radially positioned between said magnet and said extending portion of said second yoke;

said first signal output element is radially positioned between said circular magnet portion of said third yoke and said first yoke; and

said second signal output element is radially positioned between said circular magnet portion of said third yoke and said second yoke.

17. The rotation angle sensor as defined in claim 1, wherein said first and second signal output elements are positioned axially below said magnet.

5. A yoke construction for a rotation angle sensor, comprising

a) a magnet having a first magnetic pole end and a second magnetic pole end;

b) a first yoke and a second yoke positioned at a first predetermined space relative to the first magnetic pole end of said magnet;

c) a third yoke having a circular magnet portion, which circular magnet portion of said third yoke is positioned at a second predetermined space relative to second magnetic pole end of the magnet; and

d) a magnetic shielding portion positioned above said magnet, said magnetic shielding portion having a substantially semicircular shape.

6. The yoke construction of claim 5, wherein said first yoke and said second yoke each have a circular magnet portion and an extending portion, said extending portion extending from one end of said circular magnet portion in a direction to said circular magnet portion of said third yoke, and spaced at a third predetermined space relative to said circular magnet portion of said third yoke.

7. The yoke construction for a rotation angle sensor as defined in claim 6, further comprising:

e) a first Hall member installed between said extending portion of the first yoke and said circular magnet portion of the third yoke;

f) a second Hall member installed between said extending portion of the second yoke and said circular magnet portion of the third yoke.

8. The yoke construction for a rotation angle sensor as defined in claim 6, further comprising:

e) at least one projection member which is positioned on said circular magnet portion of said third yoke;

f) a first Hall member installed between said projection of the third yoke and said extending portion of the first yoke;

g) a second Hall member installed between said projection of the third yoke and said extending portion of the second yoke.

18. The yoke construction for a rotation angle sensor as defined in claim 7, wherein said first and second Hall members are positioned axially below said magnet.

9. A yoke construction for a rotation angle sensor, comprising:

a) a magnet having a first magnetic pole end and a second magnetic pole end;

b) a first yoke and a second yoke positioned at a first predetermined space relative to the first magnetic pole end of said magnet;

c) a third yoke having a circular magnet portion, which circular magnet portion of said third yoke is positioned at a second predetermined space relative to second magnetic pole end of the magnet; and

d) a magnetic shielding portion positioned above said magnet, said magnetic shielding portion having a substantially U shape and including a notch as a shaft inserting portion.

10. The yoke construction for a rotation angle sensor as defined in claim 9, further comprising:

e) at least one projection member which is positioned on said circular magnet portion of said third yoke in the direction of the perimeter;

f) a first Hall member installed between said projection of the third yoke and said extending portion of the first yoke;

g) a second Hall member installed between said projection of the third yoke and said extending portion of the second yoke.

19. The yoke construction for a rotation angle sensor as defined in claim 10, wherein said first and second Hall members are positioned axially below said magnet.

11. A rotation angle sensor, comprising:

a) a casing means;

b) a magnet means positioned in said casing means, said magnet means having a first magnetic pole end and a second magnetic pole end;

c) first and second yokes means positioned at a first predetermined space relative to the first magnetic pole end of said magnet means;

d) a third yoke means positioned at a predetermined space relative to the second magnetic pole end of said magnet means, said third yoke means further positioned between said magnet means and an extending portion of said first yoke means, and positioned between said magnet means and an extending portion of said second yoke means;

e) a first signal output means positioned between said third yoke means and said extended portion of said first yoke means, said first signal output means for outputting a first signal corresponding to an area ratio between said magnet means and said first yoke means,

f) a second signal output means positioned between said third yoke means and said extended portion of said second yoke means, said second signal output means for outputting a second signal corresponding to an area ratio between said magnet means and said second yoke means; and

g) a magnetic shielding portion means positioned above said magnet means, wherein said magnetic shielding portion means having a substantially semicircular shape and interrupts leakage magnet flux of said magnet means,

wherein said magnetic shielding portion means and said third yoke means are integrally formed of a single-piece construction.

12. The rotation angle sensor as defined in claim 11, wherein said second magnetic pole end of said magnet means has a substantially circular facing, said third yoke means comprises a substantially a circular magnet portion extending, at the predetermined space, relative to said circular facing of said second magnetic pole end.

13. The rotation angle sensor as defined in claim 12, wherein said first and second yoke means each comprise a circular magnet portion, and said extending portions of said first and second yoke means extend from said circular magnet portions of said first and second yoke means, respectively, along a direction of a perimeter of said circular magnet portion of said third yoke means.

14. The rotation angle sensor as defined in claim 12, wherein said circular magnet portion of said third yoke means is radially positioned between said magnet means and said extending portion of said first yoke means, and also radially positioned between said magnet means and said extending portion of said second yoke means;

said first signal output means is radially positioned between said circular magnet portion of said third yoke means and said first yoke means; and

said second signal output means is radially positioned between said circular magnet portion of said third yoke means and said second yoke means.

20. The rotation angle sensor as defined in claim 11, wherein said first and second signal output means are positioned axially below said magnet means.

15. A rotation angle sensor, comprising:

a) a casing;

b) a magnet positioned in said casing, said magnet having a first magnetic pole end and a second magnetic pole end;

c) first and second yokes positioned at a first predetermined space relative to said first magnetic pole end of said magnet;

d) a third yoke positioned at a second predetermined space relative to said second magnetic pole end of said magnet; and

e) a magnetic shielding portion has a substantally semicircular shape,

wherein each of said first and second yokes includes a circular magnet portion and an extending magnet portion,

wherein each said extending magnet portion is positioned at a greater radial distance from said magnet than each said circular magnet portion, respectively, and

wherein said third yoke and said magnetic shielding portion are integrally formed of a single-piece construction.

16. The rotation angle sensor of claim 15, wherein said third yoke is radially positioned between said magnet and said extending magnet portion of said first yoke, and also radially positioned between said magnet and said extending magnet portion of said second yoke.