Search

JP-2026074568-A - Planetary roller screws, linear actuators, and electromechanical brakes

JP2026074568AJP 2026074568 AJP2026074568 AJP 2026074568AJP-2026074568-A

Abstract

[Problem] To suppress the decrease in transmission efficiency when converting rotational force into linear force. [Solution] The device comprises a shaft 20 having a shaft-side threaded portion 21, a roller 30 having a roller-side threaded portion 31 formed in the shape of a round bar that engages with the shaft-side threaded portion 21, and a roller-side engagement portion 32 positioned at a different location from the roller-side threaded portion 31 in the axial direction, with repeating ridges extending along the circumferential direction of the round bar, and a nut 50 formed in the shape of a cylinder with the shaft 20 and roller 30 arranged inside, and having a nut-side engagement portion 52 on its inner circumferential surface that engages with the roller-side engagement portion 32, wherein multiple rollers 30 are arranged around the shaft 20 in the circumferential direction of the shaft 20, and the multiple rollers 30 are held together with the rollers 30 by a retainer 40 positioned inside the nut 50, and the retainer 40 supports multiple positions on each roller 30. [Selection Diagram] Figure 1

Inventors

  • 疋田 真史

Assignees

  • 日本精工株式会社

Dates

Publication Date
20260507
Application Date
20241021

Claims (7)

  1. A shaft having a shaft-side threaded portion formed in a spiral shape on its outer surface, A roller having a round bar shape extending along the axial direction of the shaft and a roller-side threaded portion that engages with the shaft-side threaded portion, and a roller-side engagement portion that is positioned at a different location from the roller-side threaded portion in the axial direction and has repeating irregularities in the axial direction that extend along the circumferential direction of the round bar, A nut having a cylindrical shape, with the shaft and roller arranged inside, and having a nut-side meshing portion that meshes with the roller-side meshing portion, with the inner circumferential surface having repeating axial irregularities that extend along the circumferential direction of the inner circumferential surface. Equipped with, Multiple rollers are arranged around the shaft in the circumferential direction of the shaft. The multiple rollers are held together with the rollers by a retainer positioned inside the nut, The retainer is a planetary roller screw that supports the roller so that it can rotate while restricting the positional relationship with the roller at multiple axial positions on the roller.
  2. The planetary roller screw according to claim 1, wherein the retainer is formed in a cylindrical shape and supports the portion of the roller between the roller-side threaded portion and the roller-side meshing portion, and the portion of the roller opposite to the side where the roller-side meshing portion is located relative to the roller-side threaded portion.
  3. A nut cover is provided on the end of the roller where the roller-side engagement portion is located. The planetary roller screw according to claim 2, wherein the nut cover has rolling portions that contact the outer circumferential surface of the roller near the end from the inside in the radial direction of the shaft.
  4. The planetary roller screw according to claim 1, wherein the outer diameter of the roller-side meshing portion is smaller than the outer diameter of the roller-side threaded portion.
  5. The planetary roller screw according to claim 1, wherein the threaded portion on the shaft side and the threaded portion on the roller side have spiral directions opposite to each other.
  6. A shaft having a shaft-side threaded portion formed in a spiral shape on its outer surface, A roller having a round bar shape extending along the axial direction of the shaft and a roller-side threaded portion that engages with the shaft-side threaded portion, and a roller-side engagement portion that is positioned at a different location from the roller-side threaded portion in the axial direction and has repeating irregularities in the axial direction that extend along the circumferential direction of the round bar, A nut having a cylindrical shape, with the shaft and roller arranged inside, and having a nut-side meshing portion that meshes with the roller-side meshing portion, with the inner circumferential surface having repeating axial irregularities that extend along the circumferential direction of the inner circumferential surface. A planetary roller screw having, A motor that applies driving force to the aforementioned shaft, Equipped with, Multiple rollers are arranged around the shaft in the circumferential direction of the shaft. The multiple rollers are held together with the rollers by a retainer positioned inside the nut, The retainer supports the roller so that it can rotate while restricting the positional relationship with the roller at multiple axial positions on the roller. The roller rotates as the rotation of the shaft, which rotates due to the driving force from the motor, is transmitted from the shaft-side threaded portion to the roller-side threaded portion, and moves relative to the shaft in the axial direction. The nut is a linear actuator that moves relative to the shaft in the axial direction together with the roller when the axial movement of the roller is transmitted from the roller-side meshing portion to the nut-side meshing portion.
  7. A shaft having a shaft-side threaded portion formed in a spiral shape on its outer surface, A roller having a round bar shape extending along the axial direction of the shaft and a roller-side threaded portion that engages with the shaft-side threaded portion, and a roller-side engagement portion that is positioned at a different location from the roller-side threaded portion in the axial direction and has repeating irregularities in the axial direction that extend along the circumferential direction of the round bar, A nut having a cylindrical shape, with the shaft and roller arranged inside, and having a nut-side meshing portion that meshes with the roller-side meshing portion, with the inner circumferential surface having repeating axial irregularities that extend along the circumferential direction of the inner circumferential surface. A planetary roller screw having, A motor that applies driving force to the aforementioned shaft, A disc-shaped brake rotor, A brake pad that contacts the aforementioned brake rotor, A brake caliper that holds the aforementioned brake pad, Equipped with, Multiple rollers are arranged around the shaft in the circumferential direction of the shaft. The multiple rollers are held together with the rollers by a retainer positioned inside the nut, The retainer supports the roller so that it can rotate while restricting the positional relationship with the roller at multiple axial positions on the roller. The roller rotates as the rotation of the shaft, which rotates due to the driving force from the motor, is transmitted from the shaft-side threaded portion to the roller-side threaded portion, and moves relative to the shaft in the axial direction. The nut moves relative to the shaft in the axial direction together with the roller, as the axial movement of the roller is transmitted from the roller-side meshing portion to the nut-side meshing portion. The nut is an electromechanical brake that applies a pressing force to the brake pad in a direction that presses the brake pad against the brake rotor by its relative axial movement with respect to the shaft.

Description

This disclosure relates to planetary roller screws, linear actuators, and electromechanical brakes. A planetary roller screw has been proposed, comprising a rotating shaft, multiple rollers arranged around the shaft, and a nut that moves relative to the shaft in conjunction with the axial relative movement of the rollers relative to the shaft. In a planetary roller screw configured in this way, the rotational force of the shaft is transmitted to the nut via the rollers, and this force is transmitted as a force that moves the nut axially along the shaft. Therefore, the planetary roller screw is capable of converting rotational force into linear force. For example, the planetary roller screw described in Patent Document 1 comprises a shaft with a helical threaded portion, multiple rollers arranged around the shaft, each having a threaded portion that engages with the threaded portion formed on the shaft, and having non-helical grooves on both sides of the threaded portion, and a nut that covers the multiple rollers and has grooves on its inner surface that engage with the non-helical grooves of the rollers. In the planetary roller screw described in Patent Document 1, with this configuration, when the shaft and nut rotate relative to each other, the rollers rotate on their own axis and move axially relative to the shaft, causing the nut to also move axially relative to the shaft along with the rollers. International Publication No. 2020/164655 Figure 1 is a cross-sectional view of a planetary roller screw according to an embodiment.Figure 2 shows the outer shape of the shaft and roller and the cross-section of the nut shown in Figure 1.Figure 3 is an exploded perspective view of a planetary roller screw.Figure 4 is an exploded perspective view of a planetary roller screw, viewed from a different direction than in Figure 3.Figure 5 is a cross-sectional view of the main part of an electromechanical brake according to an embodiment.Figure 6 is a modified example of the planetary roller screw according to the embodiment, and is a cross-sectional view showing a form in which the nut cover has an insertion hole. The present disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments described below. Furthermore, the components in the embodiments below include those readily conceivable to those skilled in the art, those substantially identical, and those within the scope of equivalents. Moreover, the components disclosed in the embodiments below can be combined as appropriate. [Embodiment] Figure 1 is a cross-sectional view of a planetary roller screw 10 according to an embodiment. Figure 2 is a diagram showing the outer shapes of the shaft 20 and roller 30 and a cross-section of the nut 50 shown in Figure 1. The planetary roller screw 10 includes a shaft 20, a roller 30, a nut 50, and a retainer 40. Of these, the shaft 20, roller 30, and nut 50 are made of heat-treated iron. The retainer 40 is made of a self-lubricating metal, such as brass. The shaft 20 is an axial member, and a through hole 23 is formed on the inside of the shaft 20 along the longitudinal direction of the shaft 20, along the central axis AX of the shaft 20. The through hole 23 has multiple sections with different diameters, and a portion of the through hole 23 is formed as a fitting hole 24 into which the drive shaft of a power source connected to the shaft 20 and used to rotate the shaft 20 can be fitted. The fitting hole 24 is designed so that relative rotation with respect to the drive shaft of the power source is impossible, allowing the drive shaft to be fitted. In this embodiment, a spline is formed in the fitting hole 24. Furthermore, the shaft 20 has a flange portion 22 formed in a flange shape near one end of the shaft 20 in the longitudinal direction on its outer circumferential surface. The flange portion 22 is formed to protrude outward from the outer circumferential surface of the shaft 20 in a disc-like shape in the radial direction of the shaft 20. Furthermore, the shaft 20 has a shaft-side threaded portion 21 formed spirally on its outer circumferential surface. The shaft-side threaded portion 21 is a thread formed spirally on the outer circumferential surface of the shaft 20, centered on the central axis AX of the shaft 20. In other words, the crests and valleys of the threads of the shaft-side threaded portion 21 extend in the circumferential direction centered on the central axis AX of the shaft 20, and are formed inclined toward the direction in which the central axis AX of the shaft 20 extends. The shaft-side threaded portion 21 is formed from a position near the flange portion 22 on the outer circumferential surface of the shaft 20 toward the side where the end opposite to the end on which the flange portion 22 is located is positioned. The roller 30 is formed in a round bar shape with an outer diameter smaller than the outer diameter of the shaft 20