Multi-rotation angle detection device, and segment counter for same

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 two or more-cycle alternating magnetic field 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, when the power generation sensor generates the voltage pulse, determines a rotation direction and a rotational position of the rotating body by using a polarity of the voltage pulse (hereinafter referred to as “new voltage pulse polarity”), an output state of the sensor element observed when the voltage pulse is generated (hereinafter referred to as “new sensor element state”), a polarity of a previous voltage pulse (hereinafter referred to as “previous voltage pulse polarity”), an output state of the sensor element observed when the previous voltage pulse is generated (hereinafter referred to as “previous sensor element state”), and a count value updated by the generation of the previous voltage pulse and stored in the nonvolatile memory (hereinafter referred to as “previous count value”), and updates the count value and stores the updated count value in the nonvolatile memory;
• wherein the segment counter is configured to update the count value by:
• determining the rotation direction of the rotating body based on a combination of the new voltage pulse polarity and the new sensor element state to determine a count amount sign;
• setting a count amount absolute value to 1 if the new voltage pulse polarity is different from the previous voltage pulse polarity;
• setting the count amount absolute value to 0 if the new voltage pulse polarity is the same as the previous voltage pulse polarity and the new sensor element state is the same as the previous sensor element state;
• setting the count amount absolute value to 2 if the new voltage pulse polarity is the same as the previous voltage pulse polarity and the new sensor element state is different from the previous sensor element state;
• and
• prefixing the determined count amount sign to the count amount absolute value to obtain a count amount, and adding the count amount to the previous count value;
• 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.