Double-roller helical pair device for variable lead screw rod

The invention discloses a double-roller helical pair device for a variable lead screw rod. The double-roller helical pair device comprises a screw rod, a nut main body, roller assemblies, guide rails, an end cover and an outer shell, wherein the screw rod is mounted on a substrate used for bearing a driving mechanism; the nut main body is mounted on the screw rod; the nut main body and the screw rod form a helical pair; the roller assemblies are composed of roller sleeves and rollers which are in interference fit; the roller assemblies are positioned in roller grooves in the upper and lower sides of the nut main body, and are longitudinally symmetrical; motion directions of the roller assemblies are opposite; the guide rails are mounted in two guide rail holes of the roller sleeves in the roller assemblies; the two ends of the guide rails are positioned in guide rail holes of the nut main body and the end cover; the roller assemblies can move along the guide rails; the roller assemblies can move back and fort