Swing-type speed reducer

A swing speed reducer comprising:

• an input shaft rotatably supported by a main body around an input axis extending in the X-axis in an X-Y-Z coordinate system;
• a precession body comprising a spherical portion and a pair of precessional shafts projecting from both sides of the spherical portion along a precession axis passing through the center of the spherical portion, with one of the precessional shafts being held by the input shaft so as to be capable of precessing around the X-axis;
• a precession supporter for supporting the precession body so as to enable precessional motion of the precession body relative to the main body, wherein the precession supporter is anchored to the main body;
• a swinging body that, in the Z-axis direction, engages with the surface of the precession body on the opposite side from the precession supporter and is swung by the precessional motion of the precession body;
• a swing motion supporter that engages with the swinging body and supports the swing motion of the swinging body relative to the main body;
• and an output shaft rotatably supported by the main body around the Z-axis direction, wherein the output shaft engages with the swinging body so as to be rotated by the swing motion of the swinging body,
• wherein an annular precession groove that follows a locus traced between the precession body and the precession supporter when the precession body is in precessional motion is provided in the surface of the precession body facing the precession supporter, and a precessional ball element that rolls through the annular precession groove is rotatably held by the precession supporter,
• wherein an annular swing groove that causes the swinging body to swing in the circumferential direction around the Z-axis and in the Z-axis direction when the precession body is in precessional motion is provided in the surface of the precession body facing the swinging body, and a ball element for swing motion that rolls through the annular swing groove is rotatably held by the surface of the swinging body facing the precession body,
• wherein a swing guide groove for guiding the swing motion of the swinging body is provided in the surface of the swinging body facing the swing motion supporter, and a swing motion guide ball element that rolls through the swing guide groove is rotatably held by the swing motion supporter, and
• wherein an undulating groove formed by a plurality of continuous arc-shaped grooves for one period of the swing motion of the swinging body is provided around the entire circumference of the surface of the swinging body facing the output shaft, and output ball elements that roll through the undulating groove are rotatably held by the output shaft.