Vibration transmitter, ultrasonic transducer structure, and medical device

A vibration transmitter comprising:

• a proximal end extending portion that extends along a central axis from a proximal end to a distal end, and is configured to receive longitudinal vibration of ultrasonic vibration generated by an ultrasonic vibrator fixed to the proximal end;
• a supported portion that:
• (i) is provided on a distal end portion of the proximal end extending portion along the central axis, (ii) located on an outer periphery of a node of vibration on the central axis or on an outer periphery near the node of the vibration while the longitudinal vibration is being transmitted along the central axis, (iii) protrudes outward in a radial direction orthogonal to the central axis, and (iv) is supported by a housing;
• a distal end extending portion that:
• (i) is disposed on a distal end portion of the supported portion along the central axis, (ii) is configured to receive the longitudinal vibration, and (iii) has an outer diameter smaller than an outer diameter of the supported portion;
• a first relay provided between the supported portion and the proximal end extending portion;
• and
• a second relay provided between the supported portion and the distal end extending portion, wherein:
• the second relay includes a horn that having an outer diameter at a position continuously adjacent to the supported portion that is larger than:
• an outer diameter of the first relay at a position continuously adjacent to the supported portion, and
• the outer diameter of the distal end extending portion;
• the horn is configured to expand an amplitude of vibration output from a distal end of the distal end extending portion to be larger than a maximum amplitude at an antinode of vibration in the first relay or the proximal end extending portion while the longitudinal vibration is being transmitted;
• and
• wherein the first relay and the second relay are shaped such that, while the longitudinal vibration is being propagated to the vibration transmitter:
• a displacement distribution of the first relay and a displacement distribution of the second relay at positions distant from the central axis in the radial direction are balanced with respect to the supported portion, and
• displacement of the supported portion in a direction along the central axis is prevented.