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US 8,424,402 B2Granted
Ball screw unit
AssigneeJtekt Corporation
InventorsHajime Watanabe, Satoshi Kondo, Yasuhiro Ohta
Life of this patent
Estimating the term…
Abstract
The outer diameter of a spline nut and the inner diameter of a nut body holding portion of a housing gradually decrease in the downward direction. A ball screw protection unit includes a nut body taper face that is formed in the outer peripheral face of the spline nut, a holding portion taper face that is formed in the nut body holding portion, and a disc spring that is provided at the upper end of the spline nut and that biases the spline nut in such a direction that a friction force between the nut body taper face and the holding portion taper face increases (downward direction).
Claims10
A ball screw unit, comprising:
- a screw shaft including a groove;
- a nut that is fitted to the groove of the screw shaft via balls and that has an outer diameter which gradually decreases in a predetermined direction;
- a nut holding portion that disposed on an outer peripheral face of the nut, that holds the nut, and that has an inner diameter which gradually decreases in the predetermined direction in accordance with a gradual decrease in the outer diameter of the nut;
- and
- a nut biasing member that biases the nut in the predetermined direction in which the outer diameter of the nut and the inner diameter of the nut holding portion gradually decrease,
- wherein the outer diameter of the nut and the inner diameter of the nut holding portion gradually decrease in such a manner that when a force that proceeds in a direction opposite to a direction of the biasing force of the nut biasing member and that overcomes the biasing force is applied to the nut, a friction force between the outer peripheral face of the nut and an inner peripheral face of the nut holding portion decreases to allow relative movement between the nut and the nut holding portion,
- wherein the nut biasing member is disposed on an end of the nut, the end of the nut having an outer diameter greater than an outer diameter of an other end of the nut, and
- wherein the nut and nut holding portion are configured such that, when the nut reaches a movement limit position of the nut in the direction of the biasing force, the nut holding portion continues moving in the direction of the biasing force.
5 more elements
A ball screw unit, comprising:
- a screw shaft including a groove;
- a nut that is fitted to the groove of the screw shaft via balls and that has an outer diameter which gradually decreases in a predetermined direction;
- a nut holding portion that is provided on an outer peripheral face of the nut, that holds the nut, and that has an inner diameter which gradually decreases in the predetermined direction in accordance with a gradual decrease in the outer diameter of the nut;
- a nut biasing member that biases the nut in the predetermined direction in which the outer diameter of the nut and the inner diameter of the nut holding portion gradually decrease;
- a housing that holds the screw shaft;
- a stopper that defines a movement limit position of the nut, which is a member that moves linearly, in a direction in which the nut moves forward, by hitting a predetermined portion of the housing;
- and
- a cylindrical body that is arranged coaxially with the screw shaft, that is fitted in the housing in such a manner that the cylindrical body is allowed to move linearly, and that is adjacent to the nut via the biasing member,
- wherein the outer diameter of the nut and the inner diameter of the nut holding portion gradually decrease in such a manner that when a force that proceeds in a direction opposite to a direction of the biasing force of the nut biasing member and that overcomes the biasing force is applied to the nut, a friction force between the outer peripheral face of the nut and an inner peripheral face of the nut holding portion decreases to allow relative movement between the nut and the nut holding portion,
- wherein the nut is a ball screw nut,
- wherein the nut holding portion is a cylindrical nut case that is fitted onto the nut and that is fixed to the cylindrical body,
- wherein the outer diameter of the nut and the inner diameter of the nut holding portion gradually decrease in the direction in which the nut moves forward, and
- wherein the nut biasing member biases the nut in the direction in which the nut moves forward.
10 more elements
Dependencies are inferred from the claim text.