US 11,975,755 B2Granted

Screw shaft and method for producing same, and electric position-adjusting device for steering wheel

AssigneeNsk Ltd.

InventorTakeshi Saito

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Abstract

Provided is a screw shaft in which shape accuracy of a male threaded portion is sufficiently secured. A screw shaft includes a large-diameter shaft portion, medium-diameter shaft portions and small-diameter shaft portions. The large-diameter shaft portion has a male threaded portion along its entire axial length on its outer peripheral surface. The medium-diameter shaft portions are arranged axially adjacent to the large-diameter shaft portion and have an outer diameter smaller than an outer diameter of the large-diameter shaft portion. The small-diameter shaft portions are axially arranged adjacent to the medium-diameter shaft portions on sides opposite to the large-diameter shaft portion, have an outer diameter smaller than the outer diameter of each of the medium-diameter shaft portions, and do not have rolling traces having a helical shape on their outer peripheral surfaces.

Claims15

Dependent claims

A screw shaft, comprising a large-diameter shaft portion, a medium-diameter shaft portion, and a small-diameter shaft portion, wherein:

the large-diameter shaft portion has a male threaded portion along an entire axial length on an outer peripheral surface;
the medium-diameter shaft portion is arranged axially adjacent to the large-diameter shaft portion and has an outer diameter smaller than an outer diameter of the large-diameter shaft portion;
the small-diameter shaft portion is arranged adjacent to the medium-diameter shaft portion on a side opposite to the large-diameter shaft portion in an axial direction, has an outer diameter smaller than the outer diameter of the medium-diameter shaft portion, and does not have a rolling trace with a helical shape on an outer peripheral surface;
the medium-diameter shaft portion has, on the outer peripheral surface, a rolling trace with a helical shape that is in phase with an extension line of a helical curve that is a groove bottom line of the male threaded portion;
the medium-diameter shaft portion is composed of a first medium-diameter shaft portion arranged on one axial side of the large-diameter shaft portion and a second medium-diameter shaft portion arranged on the other axial side of the large-diameter shaft portion;
the small-diameter shaft portion is composed of at least one of a first small-diameter shaft portion arranged on one axial side of the first medium-diameter shaft portion and a second small-diameter shaft portion arranged on the other axial side of the second medium-diameter shaft portion;
and
an axial length of the male threaded portion corresponds to an effective threaded length.

5 more elements

A manufacturing method of a screw shaft, comprising:

performing rolling processing on a workpiece, the workpiece including a large-diameter shaft portion for rolling, a medium-diameter shaft portion for rolling arranged axially adjacent to the large-diameter shaft portion for rolling and having an outer diameter smaller than an outer diameter of the large-diameter shaft portion for rolling, and a small-diameter shaft portion arranged adjacent to the medium-diameter shaft portion for rolling on a side opposite to the large-diameter shaft portion for rolling in an axial direction and having an outer diameter smaller than the outer diameter of the medium-diameter shaft portion for rolling, using a plurality of rolling dies to create progress of the workpiece in order to form a male threaded portion over an entire axial length of an outer peripheral surface of the large-diameter shaft portion for rolling, wherein:
in performing the rolling processing on the workpiece, rolling processing is performed, using the rolling dies, to form a male threaded portion on the outer peripheral surface of the large-diameter shaft portion for rolling, and the rolling dies are not brought into contact with an outer peripheral surface of the small-diameter shaft portion;
in performing the rolling processing on the workpiece, a rolling trace with a helical shape is formed on an outer peripheral surface of the medium-diameter shaft portion for rolling;
a workpiece in which the medium-diameter shaft portion for rolling is composed of a first medium-diameter shaft portion for rolling arranged on one axial side of the large-diameter shaft portion for rolling and a second medium-diameter shaft portion for rolling arranged on the other axial side of the large-diameter shaft portion for rolling, and the small-diameter shaft portion is composed of at least one of a first small-diameter shaft portion arranged on one axial side of the first medium-diameter shaft portion for rolling and a second small-diameter shaft portion arranged on the other axial side of the second medium-diameter shaft portion for rolling is used as the workpiece;
and
an axial length of the male threaded portion corresponds to an effective threaded length.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/031,559Filed 11 Oct 2021
Priority: JP 2020-17254813 Oct 2020
Published: US 2023/0406394 A121 Dec 2023
Granted: 7 May 2024
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

B62D 1/181
Yieldable or adjustable, e.g. tiltable: with power actuated adjustment, e.g. with position memory
B21H 3/04
External screw-threads ; Making dies for thread rolling: making by means of profiled-rolls or die rolls
B21H 3/046
Thread-rolling heads: working radially
F16H 25/24
Screw mechanisms: elements essential to such mechanisms, e.g. screws, nuts