Method for manufacturing a stator for an ultrasonic motor

A method for manufacturing a stator for an ultrasonic motor including a motor casing, a rotor and a piezoelectric element for causing the stator to vibrate and the rotor to rotate, wherein the stator has an inner land portion for supporting the stator in the motor casing, an outer land portion formed around the inner land portion for the piezoelectric element to be attached to, and a plurality of teeth secured to the outer land portion by a plurality of radial slits, said method comprising the steps of:

• compressing fine metal particles to form a pre-compression body having a predetermined shape, whereby said pre-compression body is provided with a plurality of projections for forming the plurality of teeth of the stator;
• baking said pre-compression body to produce a sintered body;
• and
• applying a densification process on said sintered body such that the pressing force applied to the outer land portion of said sintered body is larger than the pressing force applied to the inner land portion, whereby the density of the inner land portion is smaller than that of the outer land portion and whereby a portion of the teeth at the outer land portion of said sintered body are formed having a density ratio (Dr) of at least 90%.

A method for manufacturing a stator for an ultrasonic motor including a motor casing, a rotor and a piezoelectric element for causing the stator to vibrate and the rotor to rotate, wherein the stator has an inner land portion for supporting the stator in the motor casing, an outer land portion formed around the inner land portion for the piezoelectric element to be attached to, and a plurality of teeth secured to the outer land portion by a plurality of radial slits, said method comprising the steps of:

• compressing fine metal particles to form a pre-compression body having a predetermined shape, whereby said pre-compression body is provided with a plurality of projections for forming the plurality of teeth of the stator;
• baking said pre-compression body to produce a sintered body;
• and
• applying a densification process on the plurality of teeth of the outer land portion of said sintered body, so as to densify the teeth without densifying the inner land portion, whereby a portion of the teeth at the outer land portion of said sintered body are formed having a density ratio (Dr) of at least 90%.