Shaft for steering device, method of manufacturing shaft for steering device, and electric power steering device

Patent metadata

Field	Value
Publication number	US-11383757-B2
Application number	US-201716609774-A
Country	US
Kind code	B2
Filing date	Jun 22, 2017
Priority date	Jun 22, 2017
Publication date	Jul 12, 2022
Grant date	Jul 12, 2022

Abstract

A shaft for a steering device has a first portion, a second portion, and a third portion that is a shaft integrated with the first portion and the second portion and couples the first portion and the second portion in a first direction. The outer diameter of the third portion is smaller than the length of the second portion in a second direction intersecting with the first direction, and is constant across a direction extending along the first direction. The hardness of the third portion is greater than the hardness of the second portion, and is constant across the direction extending along the first direction.

First claim

The invention claimed is:

1. A shaft for a steering device, the shaft comprising:
a first portion;
a second portion; and
a third portion that is integrated with the first portion and the second portion, and that is a shaft coupling the first portion and the second portion in a first direction, wherein
an outer diameter of the third portion is smaller than a length of the second portion in a second direction intersecting with the first direction, and is constant across a direction extending along the first direction,
a hardness of the third portion is greater than a hardness of the second portion, and is constant in the direction extending along the first direction,
the third portion includes a small-diameter portion that is provided on a side of the first portion, and a middle-diameter portion that couples the small-diameter portion and the second portion, and that has an outer diameter smaller than that of the second portion,
an outer diameter of the small-diameter portion is smaller than that of the middle-diameter portion, and is constant in a direction extending along the first direction, and
a hardness of the small-diameter portion is greater than the hardness of the second portion, and is constant in a direction extending along the first direction.

2. The shaft for a steering device according to claim 1 , wherein
a leveled portion is provided between the third portion and the second portion, and
the hardness of the third portion near the leveled portion is greater than the hardness of the second portion near the leveled portion.

3. The shaft for a steering device according to claim 1 , wherein
the second portion includes a stopper portion that is to be coupled to an output shaft, and a large-diameter portion that is provided between the stopper portion and the third portion and has an outer diameter greater than that of the third portion, and
the hardness of the third portion is greater than a hardness of the large-diameter portion.

4. The shaft for a steering device according to claim 1 , wherein
the second portion includes a stopper portion that is to be coupled to an output shaft, and a large-diameter portion that is provided between the stopper portion and the third portion and has an outer diameter greater than that of the third portion, and
the hardness of the small-diameter portion is greater than the hardness of the large-diameter portion.

5. The shaft for a steering device according to claim 1 , wherein
the first portion and the second portion are a shaft having a longitudinal direction that extends along the first direction, and
the first portion is to be coupled to an input shaft mounted on a side of a steering wheel.

6. The shaft for a steering device according to claim 1 , wherein
the second portion is a yoke that is to be connected to an output shaft or a pinion shaft generating an output torque,
the first portion is a spline shaft portion provided with a spline groove, and
the third portion is a shaft portion that is integrated with the yoke and the spline shaft portion and couples the yoke and the spline shaft portion.

7. An electric power steering device comprising:
the shaft for a steering device according to claim 1 ;
an output shaft on which a decelerator rotated by a torque input from an electric motor is mounted, the output shaft being coupled to the second portion; and
a torsion bar that couples the output shaft and the shaft for a steering device.

8. A method of manufacturing a shaft for a steering device, the method comprising:
a step of forming a first blank portion and a second blank portion that has a diameter smaller than that of the first blank portion to form a processed hardened layer on the second blank portion, by swaging a material in a radial direction, and
a step of pressing the first blank portion and the second blank portion of the material into a die in the axial direction using a press to integrally form a spline shaft portion, a large-diameter portion, and a middle shaft portion, the spline shaft portion being provided with a spline groove, the large-diameter portion being provided to an end of the material on an opposite side of the spline shaft portion, the middle shaft portion being provided between the spline shaft portion and the large-diameter portion and having an outer diameter being smaller than that of the large-diameter portion and constant in a direction extending along the axial direction, wherein
a small-diameter portion is formed by machining the middle shaft portion, and a middle-diameter portion between the small-diameter portion and the large-diameter portion is formed by machining one end of the large-diameter portion in the axial direction.

9. The method of manufacturing a shaft for a steering device according to claim 8 , further comprising a step of machining a leveled portion between the large-diameter portion and the middle shaft portion in the axial direction, while leaving part of the processed hardened layer.

Assignees

• Nsk Ltd

Inventors

• Yasuda Kaname
• Suehiro Tatsuya
• Yamada Kazuya

Classifications

• B62D1/20 Primary

  Connecting steering column to steering gear · CPC title

• B21K1/06

  axles or shafts · CPC title

• B62D5/0412

  the axes of motor and steering column being parallel · CPC title

• B62D1/16

  Steering columns · CPC title

• B21K1/066

  splined · CPC title