Electric linear motion actuator and electric disk brake system

Patent metadata

Field	Value
Publication number	US-9574630-B2
Application number	US-201514878001-A
Country	US
Kind code	B2
Filing date	Oct 8, 2015
Priority date	Sep 7, 2010
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

An electric linear motion actuator includes planetary rollers mounted between the radially inner surface of an outer ring member and the radially outer surface of a rotary shaft, and a carrier rotatable about the rotary shaft and including radially movable roller shafts rotatably supporting the respective planetary rollers. Elastic rings each having circumferentially separate ends are each wrapped around the roller shafts to radially inwardly bias the roller shafts, thereby bringing the respective planetary rollers into elastic contact with the radially outer surface of the rotary shaft. Each elastic ring is prevented from rotating relative to the roller shafts, thereby preventing one of the roller shafts from being axially aligned with the gap between the circumferential separate ends, causing the elastic ring to be radially compressed and thus making it impossible for the elastic rings to radially bias the roller shafts.

First claim

What is claimed is:

1. An electric linear motion actuator comprising:
a housing;
an outer ring member mounted in the housing and having a center axis;
a rotary shaft extending along the center axis of the outer ring member, and configured to be rotationally driven by an electric motor;
a carrier supported on the rotary shaft so as to be rotatable about the rotary shaft; and
planetary rollers mounted between a radially outer surface of the rotary shaft and a radially inner surface of the outer ring member, and rotatably supported by the carrier,
wherein the outer ring member has a helical rib formed on the radially inner surface of the outer ring member and in engagement with circumferential grooves formed on a radially outer surface of each of the planetary rollers,
whereby when the rotary shaft rotates, the planetary rollers are configured to rotate due to frictional contact between the rotary shaft and the respective planetary rollers, thereby moving the outer ring member in an axial direction,
wherein the electric linear motion actuator further comprises a friction coupling arrangement configured to frictionally fixedly couple the carrier to the rotary shaft while an axial load applied to the outer ring member in a push-in direction is small, and to uncouple the carrier from the rotary shaft under the axial load when the axial load is large.

2. The electric linear motion actuator according to claim 1 , wherein the friction coupling arrangement comprises a positioning portion formed at an end portion of the rotary shaft and configured to limit a movement of the carrier in the axial direction, and an elastic member biasing the carrier toward the positioning portion.

3. The electric linear motion actuator according to claim 2 , wherein the positioning portion is a tapered shaft portion having a diameter that increases toward the shaft end of the rotary shaft.

4. The electric linear motion actuator according to claim 2 , further comprising a bearing member positioned by the housing in the axial direction, and rotatably supporting a shaft end portion of the rotary shaft to which torque is input, wherein the elastic member is incorporated between opposed portions of the carrier and the bearing member that are opposed to each other in the axial direction.

5. The electric linear motion actuator according to claim 3 , further comprising a bearing member positioned by the housing in the axial direction, and rotatably supporting a shaft end portion of the rotary shaft to which torque is input, wherein the elastic member is incorporated between opposed portions of the carrier and the bearing member that are opposed to each other in the axial direction.

6. The electric linear motion actuator according to claim 2 , wherein the elastic member is one of a disk spring, a coil spring, and a wave spring.

7. The electric linear motion actuator according to claim 3 , wherein the elastic member is one of a disk spring, a coil spring, and a wave spring.

8. The electric linear motion actuator according to claim 4 , wherein the elastic member is one of a disk spring, a coil spring, and a wave spring.

9. The electric linear motion actuator according to claim 1 , wherein the helical rib and the circumferential grooves have V-shaped cross-sections.

10. The electric linear motion actuator according to claim 2 , wherein the helical rib and the circumferential grooves have V-shaped cross-sections.

11. The electric linear motion actuator according to claim 3 , wherein the helical rib and the circumferential grooves have V-shaped cross-sections.

12. The electric linear motion actuator according to claim 4 , wherein the helical rib and the circumferential grooves have V-shaped cross-sections.

13. The electric linear motion actuator according to claim 6 , wherein the helical rib and the circumferential grooves have V-shaped cross-sections.

14. An electric disk brake system comprising a brake disk, a brake pad, and an electric linear motion actuator for linearly driving the brake pad and pressing the brake pad against the brake disk, thereby generating a brake force,
wherein the electric linear motion actuator is the electric linear motion actuator of claim 1 .

15. An electric disk brake system comprising a brake disk, a brake pad, and an electric linear motion actuator for linearly driving the brake pad and pressing the brake pad against the brake disk, thereby generating a brake force,
wherein the electric linear motion actuator is the electric linear motion actuator of claim 2 .

16. An electric disk brake system comprising a brake disk, a brake pad, and an electric linear motion actuator for linearly driving the brake pad and pressing the brake pad against the brake disk, thereby generating a brake force,
wherein the electric linear motion actuator is the electric linear motion actuator of claim 3 .

17. An electric disk brake system comprising a brake disk, a brake pad, and an electric linear motion actuator for linearly driving the brake pad and pressing the brake pad against the brake disk, thereby generating a brake force,
wherein the electric linear motion actuator is the electric linear motion actuator of claim 4 .

18. An electric disk brake system comprising a brake disk, a brake pad, and an electric linear motion actuator for linearly driving the brake pad and pressing the brake pad against the brake disk, thereby generating a brake force,
wherein the electric linear motion actuator is the electric linear motion actuator of claim 6 .

19. An electric disk brake system comprising a brake disk, a brake pad, and an electric linear motion actuator for linearly driving the brake pad and pressing the brake pad against the brake disk, thereby generating a brake force,
wherein the electric linear motion actuator is the electric linear motion actuator of claim 9 .

Assignees

• Muramatsu Makoto
• Eguchi Masaaki
• Yamasaki Tatsuya
• Goto Tomomi
• Ntn Toyo Bearing Co Ltd

Inventors

• Muramatsu Makoto
• Eguchi Masaaki
• Yamasaki Tatsuya
• Goto Tomomi

Classifications

• Y10T74/18576

  including screw and nut · CPC title

• F16D2125/48

  with parallel stationary axes, e.g. spur gears · CPC title

• F16D55/226

  in which the common actuating member is moved axially {, e.g. floating caliper disc brakes} · CPC title

• F16H25/2252

  Planetary rollers between nut and screw · CPC title

• F16D2127/007

  for non-linear operation · CPC title