Rotation angle detection device and rotation angle detection method

A rotation angle detection device, comprising:

• a rotor made of a magnetic material;
• a stator including “b” or more magnetic detection portions each including a bias magnetic field generation portion and a magnetic detection element, where “b” represents an integer of 3 or more;
• a processor to execute a program;
• and
• a memory to store the program which, when executed by the processor, performs a process of calculating a rotation angle of the rotor based on detection signals obtained by the magnetic detection elements,
• wherein a surface of the rotor that is opposed to the stator has convex and concave portions, which change in “x” cycles for a mechanical angle of 360 degrees, where “x” represents an integer of 1 or more, and the convex and concave portions have a shape that changes in a curved manner, the shape enabling each of the magnetic detection elements to obtain a substantially sine wave, and
• wherein “b” magnetic detection portions of the stator are arranged along a circumferential direction of the stator for one cycle of the convex and concave portions so as to be opposed to, with a gap from, the surface of the rotor that is opposed to the stator, and are arranged at intervals of a mechanical angle of 360/(x×b) degrees.

A rotation angle detection method, comprising:

• arranging, to a rotor made of a magnetic material, a stator including “b” or more magnetic detection portions each including a bias magnetic field generation portion and a magnetic detection element with a gap between the stator and the rotor;
• forming, on a surface of the rotor that is opposed to the stator, convex and concave portions, which change in “x” cycles for a mechanical angle of 360 degrees, where “x” represents an integer of 1 or more, the convex and concave portions having a shape that changes in a curved manner, the shape enabling each of the magnetic detection elements to obtain a substantially sine wave;
• arranging “b” magnetic detection portions of the stator along a circumferential direction of the stator for each cycle of the convex and concave portions such that the “b” magnetic detection portions are opposed to, with a gap from, the surface of the rotor that is opposed to the stator, and arranging the “b” magnetic detection portions at intervals of a mechanical angle of 360×(n×b+m)/(x×b) degrees, where “n” represents an integer of 0 or more and “m” represents an integer of from 1 to “b”;
• calculating a DC offset value from a reference voltage due to a DC component of each of the detection signals obtained by the magnetic detection elements of the magnetic detection portions;
• correcting the detection signals obtained by the “b” magnetic detection elements based on the DC offset value;
• subjecting the corrected “b” detection signals to b-phase/two-phase conversion to obtain two-phase signals;
• and
• calculating an arctangent function of the two-phase signals to calculate a rotation angle.