ROTATIONAL ANGLE DETECTOR

• US 20070103147A1
• Filed: 11/06/2006
• Published: 05/10/2007
• Est. Priority Date: 11/07/2005
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Original Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Inventors: NAKATA, TAKESHI, KONDO, SEIJI
• Granted Patent: US 7,366,636 B2
• Time in Patent Office: Days
• US Class Current: 324/207.250
• CPC Class Codes: B62D 15/0215 by measuring on the steering column
• CPC Class Codes: G01D 5/04 using levers; using cams; using gearing
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence

Abstract

A rotational angle detector for detecting the rotational angle of the rotor in a wide range without requiring dark current. A first detection gear including an m number of teeth and a second detection gear including an L number of teeth are each engaged with a main gear rotated integrally with a steering shaft which includes an n number of teeth. A microcomputer calculates a rotational angle θ of the steering shaft using a rotational angle α of the first detection gear within one cycle and a rotational angle β of the second detection gear within one cycle.

Claims

1. A device for detecting rotational angle of a rotor, the device comprising:

a main gear rotated integrally with the rotor and including an n number of teeth;

a first detection gear including an m number of teeth engageable with the main gear and rotated together with the main gear;

a second detection gear including an L number of teeth engageable with the main gear and rotated together with the main gear, wherein L is greater than m;

a first detection means for detecting rotational angle α

of the first detection gear within a cycle set in accordance with a predetermined angle;

a second detection means for detecting rotational angle β

of the second detection gear within the cycle; and

a rotational angle calculating means for calculating a rotational angle θ

of the rotor using the rotational angle α

of the first detection gear within the cycle detected by the first detection means and the rotational angle β

of the second detection gear within the cycle detected by the second detection means;

wherein the rotational angle calculating means calculates a first rotational angle θ

1 based on θ

1=mL/{n(L−

m)}×

[(α

−

β

)+(i−

j)Ω

], where Ω

is an angle corresponding to the cycles of α and

β

, i is an integer indicating the number of cycles completed by the first detection gear in relation with the rotational angle α

, j is an integer indicating the number of cycles completed by the second detection gear in relation with the rotational angle β

, i=j is satisfied in the case of α

≧

β

, and i=j+1 is satisfied in the case of α

<

β

;

the rotational angle calculating means calculates a second rotational angle θ

2 based on θ

2=m/n×

α

;

the rotational angle calculating means calculates the integer i indicating the number of cycles completed by the first detection gear in relation with the rotational angle α

based on i=(θ

1−

θ

2)n/(mΩ

) using the calculated first rotational angle θ

1 and the second rotational angle θ

2; and

the rotational angle calculating means calculates the rotational angle θ

of the rotor based on θ

=m/n×

(α

+iΩ

) using the calculated integer i.

2. The device according to claim 1, wherein the calculated i is rounded to an integer if i as calculated by i=(θ

1−

θ

2)n/(mΩ

) is not an integer due to measurement error.

3. The device according to claim 1, wherein L=m+1.