KR-102964213-B1 - electric actuator

KR102964213B1KR 102964213 B1KR102964213 B1KR 102964213B1KR-102964213-B1

Abstract

In an electric actuator comprising an electric motor, a nut (first screw member), and a screw shaft (second screw member) that is inserted and inserted through the nut so as to be reciprocally connected, wherein each screw thread of the screw shaft is each composed of two flanks and a top portion connecting the flanks, and grease is used as a lubricant, by forming a groove portion cut from the top portion toward the bottom portion side in each screw thread of the screw shaft, and forming a tapered surface that widens as it moves away from the groove portion in the circumferential direction on at least a part of the flank side of each groove portion, lubrication of the screw connection portion of the first screw member and the second screw member can be promoted, thereby improving motion conversion efficiency and suppressing wear of the screw connection portion.

Inventors

우수이 고지
우에야마 료
이소 다케노리
나루카와 히로무

Assignees

아스테모 가부시키가이샤

Dates

Publication Date: 20260512
Application Date: 20211112
Priority Date: 20201126

Claims (6)

An electric actuator comprising an electric motor, a first screw member rotatably driven by the electric motor, and a second screw member inserted through the first screw member so as to be linearly movable, wherein each screw thread of the first screw member and the second screw member is respectively composed of two flanks and a top portion connecting the flanks, and wherein the screw joint portions of the first screw member and the second screw member are lubricated by grease. A groove portion is formed in each of the threads of at least one of the first screw member and the second screw member, extending from the top portion toward the bottom portion. An electric actuator characterized by forming a tapered surface on at least a portion of the circumferential edge of the flank side of each of the above-mentioned groove portions, such that the axial distance between the two flanks widens as it moves away from the groove portion in the circumferential direction, and attracts grease retained within the groove portion to the screw joint portion by a wedge effect.
In paragraph 1, An electric actuator characterized in that a plurality of the above-mentioned grooves are arranged on the same straight line along the axial direction of at least one of the first screw member and the second screw member.
In paragraph 1 or 2, An electric actuator characterized in that the above-mentioned grooves are formed in a plurality in the circumferential direction of at least one of the first screw member and the second screw member.
In paragraph 1 or 2, An electric actuator characterized in that the above grooves are each formed with a depth ranging from the top portion to the bottom portion in the height direction of the screw thread.
In paragraph 1 or 2, A grease retaining portion capable of accommodating the grease is formed on the inner circumference of one axial end of the first screw member, having an outer diameter larger than the maximum diameter of the second screw member, and between the second screw member and the grease retaining portion. An electric actuator characterized by having a cover member installed to cover the axial opening of the grease retaining part.
An electric actuator comprising an electric motor, a first screw member rotatably driven by the electric motor, and a second screw member inserted through the first screw member so as to be linearly movable, wherein each screw thread of the first screw member and the second screw member is respectively composed of two flanks and a top portion connecting the flanks, and wherein the screw joint portions of the first screw member and the second screw member are lubricated by grease. A groove portion is formed in each of the threads of at least one of the first screw member and the second screw member, extending from the top portion toward the bottom portion. A tapered surface is formed on at least a portion of the circumferential edge of the flank side of each of the above-mentioned grooves, wherein the axial distance between the two flanks widens as it moves away from the groove in the circumferential direction. A grease retaining portion capable of accommodating the grease is formed on the inner circumference of one axial end of the first screw member, having an outer diameter larger than the maximum diameter of the second screw member, and between the second screw member and the grease retaining portion. A cover member is installed to cover the axial opening of the grease retaining part, and The above cover member integrally comprises a cover portion and a tube portion coaxial with the first screw member, and An electric actuator characterized by forming a cylindrical scraper portion on the inner circumference of the cover portion and setting the inner diameter of the scraper portion to be slightly larger than the outer diameter of the second screw member to form a minute gap in the radial direction between the scraper portion and the second screw member.

Description

electric actuator The present invention relates to an electric actuator having a motion conversion mechanism that converts the rotation of a first screw member by an electric motor into the linear motion of a second screw member inserted through the first screw member via a screw connection. An electric actuator comprises an electric motor and a motion conversion mechanism that converts the rotation of the electric motor into linear motion of a screw member. Here, the motion conversion mechanism comprises a first screw member (nut) that is rotationally driven by the electric motor and a second screw member (screw shaft) that is screw-coupled and inserted through the first screw member, and converts the rotation of the electric motor (first screw member) into linear motion of the second screw member. Such an electric actuator is used, for example, in an electric braking device of a vehicle (see, for example, Patent Document 1). However, in the motion conversion mechanism of an electric actuator, since a second screw member inserted and penetrating a rotating first screw member moves linearly relative to the first screw member, sliding friction occurs at the screw connection between the second screw member and the first screw member, and there is a problem in that the motion conversion efficiency is reduced due to this sliding friction, and wear occurs at the screw connection between the first screw member and the second screw member. Accordingly, Patent Document 2 proposes a configuration in which a small, meandering spiral oil groove is formed on the threaded surface (flank) of a feed screw (second screw member). Additionally, Patent Document 2 proposes a configuration in which a single straight oil groove is formed on the outer circumference of the feed screw (second screw member), which is parallel to the axis and has a depth deeper than the bottom surface of the screw groove. Patent Document 3 proposes forming a plurality of arc-shaped curved grooves in the circumferential direction on one of the two flanks of each screw thread of a first screw portion (first screw member) and a second screw portion (second screw member). Here, each groove has a first surface extending from the bottom of the screw thread toward the top, and a second surface extending from the bottom of the first surface toward the bottom of the screw thread, respectively, and the angle of inclination of the first surface flank is set to be smaller than the angle of inclination of the second surface flank. Patent Document 4 proposes that among the first flank (a flank that transmits force) and the second flank (a flank located on the axially opposite side to the first flank) of each screw thread of a rotary screw member (a first screw member) and a linear screw member (a second screw member), a concave portion for lubricating oil is formed in a grid shape by knurling only in the first flank. FIG. 1 is a perspective view of an electric actuator according to the present invention. FIG. 2 is a cross-sectional view of an electric actuator according to the present invention. FIG. 3 is a plan view of the nut and screw shaft portion of an electric actuator according to the present invention. Figure 4 is a cross-sectional view along line 4-4 of Figure 3. FIG. 5 is a partial perspective view illustrating a groove formed in the threads of a screw shaft of an electric actuator according to the present invention. FIG. 6 is a partial plan view illustrating the supply state of grease to the screw joint of the nut and the screw shaft in an electric actuator according to the present invention. Figure 7 is a cross-sectional view along line 7-7 of Figure 3. Figure 8 is an enlarged detailed view of part 8 of Figure 7. Figure 9 is an enlarged detailed view of part 9 of Figure 7. Figure 10 is a cross-sectional view along line 10-10 of Figure 9. Figure 11 is a cross-sectional view along line 11-11 of Figure 9. Figures 12 (a) and (b) are partial cross-sectional views illustrating the state of grease application to a screw shaft in an electric actuator according to the present invention. Embodiments of the present invention will be described below based on the attached drawings. FIG. 1 is a perspective view of an electric actuator according to the present invention, and FIG. 2 is a cross-sectional view of an electric actuator according to the present invention. The electric actuator (1) according to the present embodiment is provided in an electric parking brake device not shown, and as shown in FIG. 2, it is provided with an electric motor (2) capable of forward and reverse rotation as a driving source, a motion conversion mechanism (4) that converts the rotation of the electric motor (2) into reciprocating linear motion of a screw shaft (3) which is a second screw member, and an electric mechanism (gear mechanism) (5) for transmitting the rotation of the electric motor (2) to the motion conversion mechanism (4), and these electric motor (2), motion conversion