# US 10,865,861 B2 · Electric actuator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,865,861 B2 - Document ID: US10865861B2 - Status: Granted - Kind: B2 - Application number: 16/073,024 - Filed: 2017-01-25 - Published: 2019-02-07 - Granted: 2020-12-15 - Earliest claimed: 2016-02-09 - Assignees: Ntn Corporation - Applicants: Ntn Corporation - Inventors: Takushi Matsuto; Yoshinori Ikeda; Yuuki Naitou - Web page: https://patentgrep.com/patent/US10865861B2 ## CPC - F16H 25/2015: {Means specially adapted for stopping actuators in the end position; Position sensing means} - F16H 25/22: with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members - F16H 25/2204: {with balls} - F16H 25/24: Elements essential to such mechanisms, e.g. screws, nuts (F16H25/22 takes precedence) - G01B 7/00: Measuring arrangements characterised by the use of electric or magnetic techniques - G01D 5/145: {influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06)} - F16D 2121/24: using motors - F16H 2025/2068: {Means for returning linear actuator to zero position, e.g. upon occurrence of failure by using a spring} - F16H 2025/2075: {Coaxial drive motors} - F16H 2025/2087: {using planetary gears} - G01B 7/003: {for measuring position, not involving coordinate determination (coordinate measuring G01B7/004)} - F16H: GEARING - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR - F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES ## Abstract Provided is a ball screw device (31), including: a ball screw shaft (33); and a ball screw nut (32) which is rotatably fitted to an outer periphery of the ball screw shaft (33) through intermediation of a plurality of balls (34), wherein the ball screw shaft (33) performs a linear motion in an axial direction along with rotation of the ball screw nut (32), wherein the ball screw shaft (33) has a hollow shape having a hole portion (33b) extending in the axial direction, and wherein a stroke detection sensor (55) configured to detect an amount of displacement of the ball screw shaft (33) in the axial direction is arranged in the hole portion (33b). ## Claims ### Claim 1 An electric actuator comprising: a motor part configured to be driven upon receiving a supply of power; a motion conversion mechanism part configured to convert rotary motion of the motor part into linear motion; a housing accommodating the motor part and the motion conversion mechanism part; and a terminal part, wherein the motion conversion mechanism part comprises a ball screw device, the ball screw device comprising: a ball screw shaft; and a ball screw nut that is rotatably fitted to an outer periphery of the ball screw shaft through intermediation of a plurality of balls, wherein the ball screw shaft advances and retreats in an axial direction along with rotation of the ball screw nut, wherein the ball screw shaft has a hollow shape having a hole portion extending in the axial direction, wherein a stroke detection sensor configured to detect an amount of displacement of the ball screw shaft in the axial direction is arranged in the hole portion, wherein the housing comprises a plurality of members coupled in the axial direction, wherein the terminal part is configured to hold a power supply circuit and the stroke detection sensor, the power supply circuit being configured to supply the power to the motor part, wherein the terminal part integrally comprises a tubular portion that forms a part of the housing, and wherein the tubular portion is sandwiched by other members of the plurality of members forming the housing from both sides in the axial direction. ### Claim 2 (depends on 1) The electric actuator according to claim 1, wherein the stroke detection sensor is a Hall sensor configured to detect a magnetic field in the axial direction and a radial direction formed in a periphery of a permanent magnet arranged so as to be opposed to the stroke detection sensor through a radial gap, and calculate the amount of displacement of the ball screw shaft in the axial direction based on the detection of the magnetic field. ### Claim 3 (depends on 1) The electric actuator according to claim 1, wherein a center axis of the ball screw shaft and a rotation center of the motor part match with each other. ### Claim 4 (depends on 1) The electric actuator according to claim 1, wherein the motion conversion mechanism part further comprises a speed reducer configured to reduce a speed of rotation of the motor part and transmit the rotation to the ball screw nut. ### Claim 5 (depends on 4) The electric actuator according to claim 4, wherein the speed reducer comprises a planetary gear speed reducer. ### Claim 6 (depends on 1) The electric actuator according to claim 1, further comprising an urging member configured to always urge the ball screw shaft to an original point side. ### Claim 7 (depends on 1) The electric actuator according to claim 1, wherein the terminal part has, on an outer peripheral portion thereof, an opening portion for allowing a lead wire connected to the power supply circuit and a signal line connected to the stroke detection sensor to be drawn out to a radially outer side of the housing.