The application discloses an up-drilling hot melting
drill bit with variable
diameter, and belongs to the technical field of polar ice cap drilling, which comprises a first
drill bit body, a spline rod, a first spring, a sliding sleeve, a second spring, a second
drill bit body, a connecting rod, a first fixing block, a third spring, a limiting sleeve, a fourth spring, a second fixing block, an outer tube, a third
drill bit body, a supporting rod, a fifth spring and a limiting
gasket, which maintains a small
diameter when drilling downward and increases the
diameter when drilling upward, so that a large-diameter borehole is formed, and the problem that a recyclable hot melting
detector is prone to being stuck when drilling upward in a dry hole section is solved; the interaction force between the
drill bit and the ice layer is used as the power for increasing the diameter of the
drill bit, and the drill bit can be self-locked when the diameter of the drill bit is increased to the maximum; the setting height of the second drill bit body and the third drill bit body is controlled, so that the retraction and extension movements of the second drill bit body and the third drill bit body are performed at different heights, the mutual interference of the second drill bit body and the third drill bit body is avoided, and the second drill bit body and the third drill bit body can be spliced into a complete ring after being extended, and the structure is simple and reliable.