Multi-rotation angle detection device

A multiturn angle detection device to generate a multiturn absolute angle detection value of a rotating body that is rotated about a rotation axis, the multiturn angle detection device comprising:

• a segment counter to generate a count value according to the rotation of the rotating body by counting segments defined by dividing a single-turn cycle of the rotating body in an angular range over a single turn of the rotating body;
• a precision absolute angle detector, operative with external electric power supply, to generate an absolute angle detection value within the single-turn cycle of the rotating body at a resolution higher than the segments;
• and
• an arithmetic device, operative with the external electric power supply, to generate the multiturn absolute angle detection value of the rotating body by combining the count value of the segment counter with the absolute angle detection value of the precision absolute angle detector;
• wherein the segment counter includes a single power generation sensor, a magnetic field generation source to be rotated together with the rotating body about the rotation axis, a sensor element different from the power generation sensor, and a nonvolatile memory to store the count value;
• wherein the power generation sensor includes a magnetic wire that exhibits a large Barkhausen effect, and a coil wound around the magnetic wire, and generates a voltage pulse according to a magnetic field change occurring due to the rotation of the magnetic field generation source;
• wherein the magnetic field generation source applies a k-cycle alternating magnetic field (wherein k is an integer not smaller than 3) per each turn of the rotating body axially of the magnetic wire;
• wherein the segment counter is operative with an energy of the voltage pulse generated by the power generation sensor without receiving the external electric power supply, and is to detect a rotation direction and a rotational position of the rotating body by using the voltage pulse generated by the power generation sensor and an output signal of the sensor element to update the count value, and to store the updated count value in the nonvolatile memory;
• wherein the arithmetic device uses the count value stored in the nonvolatile memory as it is when receiving the external electric power supply, and generates the multiturn absolute angle detection value of the rotating body by combining the count value of the segment counter with the absolute angle detection value of the precision absolute angle detector.