The invention discloses an intermittent sub-joint for lowering the bottom-hole
pressure difference, which comprises an outer cylinder, a
drill pipe joint, a spring and an annular
piston. Rod joint, the
drill pipe joint part is inserted into the shaft hole, and a
water flow channel is arranged in the center of the
drill pipe joint along its axial direction; the spring and the annular
piston are both sleeved on the lower part of the
drill pipe joint and can move up and down along its central axis, and the spring The upper end is connected to the
drill pipe joint, and the lower end of the spring is connected to the upper end surface of the annular
piston; a pressure relief hole and a reverse
nozzle are set on the side wall of the outer cylinder, the pressure relief hole communicates with the chamber, and the upper end surface of the annular piston is subjected to external annular pressure. The lower end surface of the annular piston is subjected to the
drilling fluid pressure in the shaft hole. When the annular piston moves up to a certain distance under the action of the
pressure difference between the upper and lower end surfaces, the reverse
nozzle communicates with the shaft hole. The invention can improve the effect of reducing the
pressure difference at the bottom of the well, accelerate the drilling speed of the drilling
machine, and enhance the ability of the
drill bit nozzle to clean the bottom of the well and assist
rock breaking.