Ball screw mechanism and linear motion device

Abstract

Provided is a ball screw mechanism that can prevent vibration and noise and avoid an increase in heat by ensuring smooth movements of balls without the occurrence of obstructions or the like of the balls on a screw shaft, and without the need to consider the return of the balls as in a conventional circulation-type ball screw. The present invention is provided with a screw shaft 2 that has a spiral groove 2a and extends linearly; a housing 30 that surrounds the circumference of the screw shaft 2; and a plurality of balls 4 and ball bearings 5 that transmit the thrust of the screw shaft 2 to the housing 30. The ball bearings 5 each have outer rings 7 that are attached and fixed to the housing 30 at predetermined intervals along the spiral groove 2a of the screw shaft 2, and inner rings 6 provided with a concave spherical contact surface 5a, which is in contact with the balls 4, on the side surface facing the screw shaft 2. The inner rings 6 are installed so as to be rotatable about rotation axes N1-N4 that cross the rotation axis O of the screw shaft 2. The balls 4 are disposed adjacent to the inside of the spiral groove 2a of the screw shaft 2 at predetermined intervals while in contact with the contact surfaces 5a of the ball bearings 5.

Description

technical field [0001] The present invention relates to the technology of a ball screw mechanism using a screw shaft and balls. Background technique [0002] Conventionally, as the ball screw, various ball screws are known. [0003] For example, there are non-recirculating ball screws and recirculating ball screws in which balls are fixed to sliding bearings provided in the nut and the balls are rotated on the screw shaft in the non-recirculating ball screw. While moving the nut, in the recirculating ball screw, in the ball nut located on the ball screw shaft, a plurality of balls are wound around the screw shaft 1.5 to 3.5 times, and the balls sent to the nut discharge port are passed through the tube Or guides such as return grooves return to the original nut entry, allowing the balls to circulate within the nut. [0004] However, conventional recirculating ball screws have various problems as described below, which cannot be solved at present. [0005] For example, whe...

AI Technical Summary

Problems solved by technology

[0008] As a result, the smooth return of the balls is hindered, and mutual impact between the balls occurs, resulting in increased vibration, noise, and heat, which also hinders the smooth return of the balls

[0009] In addition, in the conventional recirculating ball screw, the mutual collision between the balls is inevitable in the structure, especially in order to realize the reduction of the backlash or the increase of the rigidity of the ball screw, a set of When preloading the ball screw with a nut with oversized balls or a pair of nuts displaced in the axial direction, the mutual pressing between the balls becomes stronger, and the direction of rotation of the contact surface of the balls changes. On the contrary, a loss is generated thereby, so a decrease in power transmission efficiency cannot be avoided

[0010] In order to prevent this problem, a cage has been conventionally proposed, but unlike general bearings, there is a problem that the structure becomes complicated due to the return of the balls.

[0011] In addition, when the number of effective loops of the nut (the number of turns of the ball) increases, the accumulated pitch error also increases, so the load sharing ratio of the balls varies, and it is very difficult to suppress it.

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