Rotation detection sensor ring and method of making the same

A sensor ring to be coaxially mounted on a free end portion of a rotating element for detecting rotations of the rotating element, with the free end portion being defined by an axially extending cylindrical surface and a radial stop surface radially extending from the cylindrical surface and a curvature surface connecting the cylindrical surface with the radial stop surface, comprising:

• a cylindrical portion which defines a cylindrical center opening to be press fitted over the axially extending cylindrical surface of the free end portion of the rotating element;
• a flange portion extending diagonally radially outward from one end periphery of the cylindrical portion such that the flange portion avoids the curvature surface between the cylindrical surface and the radial stop surface of the free end of the rotating element and to abut on the radial stop surface when the sensor ring is completely mounted on the free end portion of the rotating element;
• an annular sensing portion extending radially outward from the other end periphery of the cylindrical portion;
• and
• an outer ring portion extending axially toward the flange portion from an outer periphery of the sensing portion to partly surround the cylindrical portion, and wherein the sensor ring is a one piece product having the cylindrical portion, the flange portion, the sensing portion and the outer ring portion.

A method of manufacturing a sensor ring from a blank of single plate material, the blank including a cylindrical portion, a sensing portion extending radially outward from one end periphery of the cylindrical portion and an outer ring portion extending axially toward the other end periphery of the cylindrical portion from an outer periphery of the sensing portion to partly surround the cylindrical portion, comprising:

• A) setting the blank on a lower mold of a first mold unit with the sensing portion being directed downward toward the lower mold and the cylindrical portion being engaged with a nest plate provided on the lower mold;
• B) lowering a presser mold toward the lower mold until it w is received in a space defined by the cylindrical portion, sensing portion and outer ring portion so that the sensing portion is clamped between the presser mold and lower mold and the blank is held in position;
• C) lowering a plurality of pierce punches toward the lower mold in such a way that downward movement of the pierce punches is guided by the presser mold, to make a plurality of rectangular or square openings in the sensing portion at constant pitches in the circumferential direction of the sensing portion;
• D) removing the blank from the lower mold;
• E) setting the blank on a second mold unit such that an inner wall of the cylindrical portion is supported by a first nest pin, the downwardly directed face of the sensing portion is supported by a stationary punch and an outer wall of the cylindrical portion Is supported by a movable mold with an upper length of the cylindrical portion slightly projecting upward from the movable mold;
• and
• F) lowering an upper mold punch to sandwich the projecting length of the cylindrical portion between the upper mold punch and the movable mold thereby bending the projection length radially outward to form a flange portion of the sensor ring.

An arrangement for detecting rotations of a rotating element, comprising:

• a sensor ring to be coaxially mounted on a free end portion of a rotating element, the free end portion being defined by an axially extending cylindrical surface, a radial stop surface radially extending from the cylindrical surface and a curvature surface connecting the cylindrical surface with the radial stop surface, the sensor ring including:
• a cylindrical portion defining a cylindrical center opening to be press fitted over the axially extending cylindrical surface of the free end portion of the rotating element,
• a flange portion extending diagonally in a radially outward direction from one end periphery of the cylindrical portion such that the flange portion avoids the curvature surface between the cylindrical surface and the radial stop surface of the free end of the rotating element and abuts on the radial stop surface when the sensor ring is completely mounted on the free end portion of the rotating element, and
• an annular sensing portion extending radially outward from the other end periphery of the cylindrical portion, the sensing portion having a plurality of openings at constant intervals in the circumferential direction of the sensing portion to define teeth between each two adjacent openings;
• and
• a sensor exposed to the sensor ring for detecting the teeth of the sensing portion and in turn rotations of the rotating element;
• wherein the flange portion of the sensor ring has a chamfered surface on its inner wall exposed to the connection curvature of the free end portion of the rotating element to avoid the connection curvature of the free end portion of the rotating element.