Electromechanical Actuator

Patent metadata

Field	Value
Publication number	US-2018259019-A1
Application number	US-201615758289-A
Country	US
Kind code	A1
Filing date	Sep 5, 2016
Priority date	Sep 7, 2015
Publication date	Sep 13, 2018
Grant date	—

Abstract

An electromechanical actuator for use in a hydraulic braking circuit of a vehicle comprises an electric motor having a stator and a rotor, and a linear actuator that is located within the motor. The linear actuator comprises an elongate shaft having a screw part at one end carrying an external thread that extends along a portion of the shaft, and a fixing part at the other end shaft, the linear actuator further comprising a drive nut that surrounds the screw part of the shaft and is located at least in a retracted position inside the enlarged bore of the first portion of the rotor body, the drive nut and being connected to the screw part. The rotor body is secured relative to the stator by a bearing assembly that is fixed to the second part of the elongate rotor body, the other end of the rotor body being otherwise unsupported and overhung from the bearing assembly.

First claim

1 . An electromechanical actuator for use in a hydraulic braking circuit of a vehicle comprising:
an electric motor having a stator and a rotor, and a linear actuator that is located within the motor, in which: the stator is located within a housing having a first end and a second end, the rotor is located inside the housing and comprises an elongate rotor body having a bore passing from a first end of the body to a second end of the body, the bore being enlarged over a first portion of the body located towards the first end of the motor, and being of reduced size over a second portion of the body located towards the second end of the motor, the linear actuator comprising an elongate shaft that is located within the bore in the elongate rotor body, the shaft having a screw part at one end carrying an external thread that extends along a portion of the shaft that is located within the first portion of the bore in the rotor body, and a fixing part at the other end of the shaft that is a tightly located into the bore of the second portion of the elongate body to prevent radial movement of the shaft relative to the elongate body, the linear actuator further comprising a drive nut that surrounds the screw part of the shaft and is located at least in a retracted position inside the enlarged bore of the first portion of the rotor body, the drive nut having an internal thread and being connected to the screw part through a set of balls that engage the threads of the drive nut and screw part, the rotor body being secured relative to the stator by a bearing assembly that is fixed to the second part of the elongate rotor body, the other end of the rotor body being otherwise unsupported and overhung from the bearing assembly.

2 . The electromechanical actuator according to claim 1 in which the second part of the rotor body is located concentrically within the stator of the motor and the first part of the rotor body is offset axially from the stator.

3 . The electromechanical actuator according to claim 1 in which the housing, stator, rotor body and shaft are all generally cylindrical when viewed in cross section and all have their long axes aligned on a common central axis of the motor.

4 . The electromechanical actuator according to claim 1 in which the rotor body is secured to the housing through a bearing race assembly of the kind having an annular inner race that is secured to the second part of the rotor body, an annular outer bearing race that is secured to the housing, and a plurality of bearings located between the races.

5 . The electromechanical actuator according to claim 4 in which the bearing assembly comprises a four point contact bearing.

6 . The electromechanical actuator according to claim 4 in which the inner bearing race is a transition fit or very light sliding fit onto the second portion of the rotor body.

7 . The electromechanical actuator according to claim 4 in which the outer bearing race is prevented from moving radially or axially relative to the housing.

8 . The electromechanical actuator according to claim 1 in which, to secure the rotor body to the housing and the shaft to the rotor body, the portion of the shaft that extends through the reduced width section of bore in the rotor is provided with an external thread and a locking nut is provided that has an internal thread that engages the thread on the external thread, the locking nut being sized so that when located on the thread of the shaft the locking nut engages both the rotor and the inner bearing race whereby as the locking nut is tightened the shaft is pulled into engagement with the bore of the rotor towards the first end of the motor housing and at the same time the inner race of the bearing is pressed by the locking nut onto the rotor in a direction towards the second end of the housing.

9 . The electromechanical actuator according to claim 8 in which an opening is provided in an end wall of the housing that closes the second end of the housing to allow access to the locking nut.

10 . The electromechanical actuator according to claim 8 in which the outer face of the rotor body that is closest to the second end of the housing is provided with a shoulder that locates an end face of the inner bearing, the locking nut tightening the inner race onto this shoulder.

Assignees

• Trw Ltd

Inventors

• Smith Nigel Peter

Classifications

• F16D65/14 Primary

  Actuating mechanisms for brakes; Means for initiating operation at a predetermined position (brake control systems, parts thereof B60T) · CPC title

• H02K7/102

  with friction brakes · CPC title

• H02K7/085

  radially supporting the rotary shaft at only one end of the rotor (H02K7/086, H02K7/09 take precedence) · CPC title

• B60T13/746

  and mechanical transmission of the braking action · CPC title

• F16D2121/04

  acting on a piston-type actuator, e.g. for liquid pressure · CPC title