JP2011172378A - Electric linear motion actuator and electric braking device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric linear motion actuator capable of smoothly guiding the linear movement of an output member performing linear movement even if a lateral moment acts to the output member, and preventing abrasion of outer diameter surfaces of a rotating shaft and a planet roller, and in an inner diameter surface of an outer ring member. <P>SOLUTION: The movement of a carrier 6 for supporting the planet roller 7 is regulated in an axial direction, the outer ring member 5 internally fitted so as to be slidable in the axial direction in the inner diameter surface of a cylindrical portion 1a of a housing 1 is whirl-stopped by a key 22 to a driven object to be coupled, the outer ring member 5 is used as an output member for linear movement, and a hard plating layer is applied to the surface of a thread member 5b for forming spiral protruding threads which are circumferentially formed on the outer diameter surface of the rotating shaft 4, the outer diameter surface including a portion of the spiral groove 7a of the planet roller 7 and the inner diameter surface of the outer ring member 5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric linear motion actuator that linearly drives a driven object by converting the rotational motion of an electric motor into linear motion, and an electric brake that presses a brake member against the braked member using the electric linear motion actuator Relates to the device.

  Many of the electric linear actuators that convert the rotational motion of the electric motor into linear motion to drive the driven object linearly employ a ball screw mechanism or a ball ramp mechanism as the motion conversion mechanism. In many cases, a gear reduction mechanism such as a planetary gear reduction mechanism is incorporated so that a large linear driving force can be obtained (see, for example, Patent Document 1).

  The ball screw mechanism and the ball ramp mechanism employed in the electric linear actuator described above have a certain degree of boosting function by a motion conversion mechanism along the lead screw thread and the inclined cam surface. It is not possible to secure a large boosting function that is necessary for the above. For this reason, in the electric linear actuator that employs these motion conversion mechanisms, a separate reduction mechanism such as a planetary gear reduction mechanism is incorporated to increase the driving force. In this way, a separate reduction mechanism is incorporated. Impedes the compact design of the electric linear actuator.

  For such problems, the present inventors can ensure a large boosting function without incorporating a separate speed reduction mechanism, and as an electric linear actuator suitable for an electric brake device that requires a large thrust, A plurality of planetary rollers rotatably supported by the carrier are interposed between a rotating shaft to which rotation is transmitted from the electric motor and an outer ring member fixed to the inner diameter surface of the housing on the outer diameter side of the rotating shaft. The planetary roller revolves while rotating around the rotation shaft as the rotation shaft rotates, and a spiral protrusion is provided on the inner diameter surface of the outer ring member, and the spiral protrusion is provided on the outer diameter surface of the planetary roller. A circumferential groove into which the spiral ridges are fitted at the same pitch as or a spiral groove into which the spiral ridges are fitted at the same pitch as the spiral ridges with different lead angles and revolves while rotating around the rotation axis. Support planetary roller First, a mechanism in which the carrier is relatively moved in the axial direction, the rotational motion of the rotating shaft is converted into the linear motion of the carrier, and the linear drive member connected to the carrier or the carrier is used as the output member for linearly driving the driven object. It has been proposed (see Patent Documents 2 and 3).

  On the other hand, many hydraulic brake devices have been adopted, but in recent years, with the introduction of advanced brake control such as ABS (Antilock Brake System), these controls are performed without a complicated hydraulic circuit. Electric brake devices that can do this are attracting attention. The electric brake device operates an electric motor in response to a brake pedal depression signal or the like, and incorporates an electric linear actuator as described above into a caliper body to press a brake member against a member to be braked (for example, a patent) Reference 4).

JP-A-6-327190 JP 2007-32717 A JP 2007-37305 A JP 2003-343620 A

  Patent Documents 2 and 3 describe an electric linear actuator that uses a linear drive member connected to the carrier or a linear drive member as an output member that linearly moves, and does not incorporate a separate speed reduction mechanism. However, since the linearly moving carrier and the linear drive member have a relatively short length in the axial direction, for example, in an electric brake device using this electric linear actuator, a brake to be driven is used. A tangential force acts on the member from the braked member, but a part of this tangential force acts as a lateral moment on the carrier and linear drive member connected to the brake member, making it difficult to smoothly guide these linear motions. There is a problem. When the linear drive member guided by the outer ring member is connected to the brake member, when the brake member is worn, the axial protrusion amount of the linear drive member from the outer ring member is increased, and the guide length is shortened. Therefore, smooth guidance of the linear drive member becomes more difficult.

  Further, when the electric linear actuator is used repeatedly, wear proceeds on the outer diameter surface of the rotating shaft and the planetary roller and the inner diameter surface of the outer ring member. As the wear progresses and the play increases, the planetary roller that revolves while rotating tends to have a radial inclination or a circumferential inclination (skew). When the planetary roller is inclined in the radial direction or the circumferential direction in this way, the contact between the helical ridges meshing with each other and the circumferential groove or the helical groove becomes non-uniform, and an excessively large load is locally generated between them. May occur, and the spiral protrusions or circumferential grooves or spiral grooves may be partially lost. Furthermore, when the spiral ridge of the outer ring member or the circumferential groove or spiral groove of the planetary roller is worn, contact with the circumferential groove or spiral groove in each of the spiral ridges becomes uneven, and partly The contact surface pressure with the circumferential groove or the spiral groove at the streak of the rod becomes excessive, and there is a possibility that seizure, a defect or the like may occur at these contact portions.

  Accordingly, an object of the present invention is to make it possible to smoothly guide the linear motion of the output member even when a lateral moment acts on the linearly-moving output member, and to rotate the outer shaft and outer ring of the rotating shaft or planetary roller. This is to prevent wear on the inner diameter surface of the member.

  In order to solve the above-described problems, the present invention provides a carrier between a rotating shaft to which rotation is transmitted from an electric motor and an outer ring member fitted inside the inner diameter surface of the housing on the outer diameter side of the rotating shaft. A plurality of planetary rollers that are rotatably supported are interposed so that these planetary rollers revolve around the rotation shaft as the rotation shaft rotates, and spirally project on the inner surface of the outer ring member. A circumferential groove into which the spiral ridge is fitted at the same pitch as the spiral ridge, or a spiral ridge with a different lead angle at the same pitch as the spiral ridge, is provided on the outer diameter surface of the planetary roller. The outer ring member and the carrier are moved relative to each other in the axial direction, and the rotational movement of the rotary shaft is converted into the linear movement of the output member in the axial direction to be connected to the linearly moving output member. Electric drive that drives the driven object in a straight line An output member that restricts movement of the carrier in the axial direction, prevents the outer ring member from rotating, and is fitted into the inner diameter surface of the housing so as to be slidable in the axial direction, and linearly moves the outer ring member. As described above, a configuration in which surface hardening treatment is applied to at least one of the outer diameter surface of the rotating shaft, the outer diameter surface of each planetary roller, and the inner diameter surface of the outer ring member is employed.

  That is, the movement of the carrier in the axial direction is restricted, the outer ring member is prevented from rotating, the inner ring surface of the housing is slidably fitted in the axial direction, and the outer ring member is used as an output member that linearly moves. The outer ring member as a member can be guided with a long dimension in the axial direction on the inner diameter surface of the housing, and even if a lateral moment acts on the linearly moving output member, the linear motion of the output member can be smoothly guided. The outer diameter surface of the rotating shaft, the outer diameter surface of each planetary roller, and the inner diameter surface of the outer ring member are subjected to surface hardening treatment, whereby the outer diameter surface of the rotating shaft and the planetary roller and the inner diameter of the outer ring member The wear on the surface can be prevented.

  By forming the spiral ridges provided on the inner diameter surface of the outer ring member with the strip members that surround the spiral grooves provided on the inner diameter surface of the outer ring member, the spiral ridges can be easily and accurately formed.

  By providing a guide surface that guides the upper surface of the spiral protrusion formed by the strip member that surrounds the spiral groove, the strip member that surrounds the spiral groove can be prevented from falling off. The guide surface for guiding the upper surface of the spiral ridge can be provided on a carrier that supports the planetary roller or a separate guide member fixed to the carrier.

  By subjecting at least one of the surface of the spiral ridge provided on the inner diameter surface of the outer ring member and the surface of the circumferential groove or spiral groove provided on the outer diameter surface of the planetary roller to surface hardening treatment, the spiral ridge or spiral It is possible to prevent seizure or chipping in the circumferential groove or the spiral groove into which the ridge is fitted.

  The surface hardening process may be a hard plating process. Examples of the hard plating treatment include hard Cr plating, Ni—B plating, and Ni—P plating.

  The wear resistance of the member subjected to the surface hardening treatment can be further improved by carburizing the low carbon steel having a carbon content of 0.3% by mass or less. .

  Even when the surface-treated member is subjected to quenching and tempering treatment using a medium carbon steel having a carbon content exceeding 0.3% by mass as a material, these wear resistances are further improved. be able to.

  By making at least one of the spiral ridge provided on the inner diameter surface of the outer ring member and the spiral groove provided on the outer diameter surface of the planetary roller into a multi-threaded spiral, the lead angle of the spiral ridge and the spiral groove can be adjusted. The degree of freedom for setting the difference can be increased.

By setting the equivalent lead angle α represented by the following equation (1) of the spiral ridge to 0.5 ° or less, preferably 0.3 ° or less, the spiral ridge and planet of the outer ring member due to the axial load. It is possible to ensure a load holding function so that the outer ring member is not pushed back so that slippage occurs between the circumferential groove or the spiral groove of the roller and the planetary roller does not rotate in the reverse direction.

  The reason why the equivalent lead angle α is set to 0.5 ° or less is based on experimental results. When the lubrication state between the spiral protrusion and the circumferential groove or the spiral groove is good, it is 0.3 ° or less. It is preferable to do this.

ここに、Ｄｓは回転軸の外径、θｓは回転軸の回転角度であり、Ｄｓ・θｓは回転軸の外径面の回転変位となる。 The tangent of the equivalent lead angle α is defined as the axial movement amount X of the outer ring member with respect to the rotational displacement of the outer diameter surface of the rotating shaft, and is expressed by equation (2).

Here, Ds is the outer diameter of the rotating shaft, θs is the rotation angle of the rotating shaft, and Ds · θs is the rotational displacement of the outer diameter surface of the rotating shaft.

ここに、Ｄｏは外輪部材の内径、θｐは遊星ローラの公転角度である。 Since the axial movement amount X of the outer ring member is generated by the difference between the lead angle αo of the spiral protrusion and the lead angle αp of the circumferential groove or the spiral groove of the planetary roller, it is expressed by equation (3). In the case of the circumferential groove, the lead angle αp is zero.

Here, Do is the inner diameter of the outer ring member, and θp is the revolution angle of the planetary roller.

（４）式は、プラネタリ型遊星減速機における速度伝達比の式と等価なものであり、（３）式と（４）式を（２）式に代入して整理することにより、（１）式が得られる。 Further, the revolution angle θp of the planetary roller is expressed by the following equation (4).

Equation (4) is equivalent to the equation for the speed transmission ratio in the planetary planetary reducer. By substituting Equations (3) and (4) into Equation (2), The formula is obtained.

  Equation (1) corresponds to a lead angle that defines the amount of axial movement of the screw shaft accompanying the rotation of the screw. It is known that the screw that holds the axial load by sliding friction of the screw inclined surface varies depending on the lubrication state of the screw inclined surface, but the limit lead angle that can hold the axial load is about 3 to 5 °. . The equivalent lead angle α limited by the present invention so as to hold the above-described axial load is smaller by one order than the limit lead angle of this screw, and is close to the limit lead angle of the ball screw. The reason for this is considered that the planetary roller of the linear actuator rotates in a planetary manner between the rotating shaft and the outer ring member like a ball screw ball.

  The present invention also includes an electric linear actuator that linearly drives the brake member by converting the rotational motion of the electric motor into linear motion, and presses the brake member that is linearly driven against the braked member. Therefore, by adopting a configuration in which any one of the above-described electric linear actuators is used as the electric linear actuator, a tangential force acting on the brake member from the braked member is laterally applied to the output member that moves linearly. Even when acting as a moment, the linear motion of the output member can be smoothly guided, and wear on the outer diameter surface of the rotating shaft and the planetary roller and the inner diameter surface of the outer ring member can be prevented.

  The electric linear actuator of the present invention restricts the movement of the carrier supporting the planetary roller in the axial direction, prevents the outer ring member from rotating, and is fitted into the inner diameter surface of the housing so as to be slidable in the axial direction. Since the member is an output member that linearly moves and at least one of the outer diameter surface of the rotating shaft, the outer diameter surface of each planetary roller, and the inner diameter surface of the outer ring member is subjected to surface hardening treatment, Even if a lateral moment acts, the linear motion of the output member can be smoothly guided, and the planetary roller can be prevented from being worn on the outer surface of the rotating shaft and the planetary roller or the inner surface of the outer ring member. It is possible to prevent the inclination in the radial direction or the circumferential direction from occurring.

  In the electric brake device of the present invention, the brake member that presses against the member to be braked is linearly driven by using the electric linear actuator described above, so that the tangential force acting on the brake member from the member to be braked is applied. However, even if acting as a lateral moment on the linearly moving output member, the linear motion of the output member can be smoothly guided, and the outer diameter surface of the rotating shaft and the planetary roller and the inner diameter surface of the outer ring member can be guided. It is possible to prevent wear and prevent the planetary roller from being inclined in the radial direction or the circumferential direction.

A longitudinal sectional view showing an embodiment of an electric linear actuator Sectional view along the line II-II in FIG. Sectional view along line III-III in FIG. (A), (b) is a front view which shows the spiral protrusion of the outer ring member of FIG. 1, and the spiral groove of the planetary roller, respectively. Sectional drawing which expands and shows the vicinity of the planetary roller of FIG. Sectional drawing which shows the modification of FIG. 1 is a longitudinal sectional view showing an electric brake device employing the electric linear actuator of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the electric linear actuator is provided with a flange 1b projecting to one end of a cylindrical portion 1a of the housing 1, and the electric motor 2 is connected to the cylindrical portion 1a on the flange 1b. Mounted in parallel, the rotation of the rotor shaft 2a of the electric motor 2 is transmitted to the rotating shaft 4 disposed at the center of the cylindrical portion 1a by the gears 3a, 3b, 3c. Four planetary rollers 7 rotatably supported by the carrier 6 are interposed between the outer ring member 5 fitted in the inner diameter surface of the cylindrical portion 1a so as to be slidable in the axial direction, and each planetary roller 7 rotates. As the shaft 4 rotates, it revolves while rotating around it.

  A lid 1c is attached to the side of the housing 1 where the flange 1b is provided, and the gears 3a, 3b, 3c are arranged so as to mesh with each other in the same axial section of the space covered with the lid 1c. A shaft support member 8 is fitted on the lid 1c side of the cylindrical portion 1a, and the base end side of the rotating shaft 4 to which the gear 3c is attached is supported by the shaft support member 8 with a ball bearing 9. The shaft support member 8 is fixed to the housing 1 with retaining rings 10 on both sides, and also serves to regulate the movement of the rotary shaft 4 and the carrier 6 in the axial direction. An intermediate gear 3b meshed with the gear 3a and the gear 3c attached to the rotor shaft 2a is supported by a ball bearing 12 on a shaft pin 11 passed between the flange 1b and the lid 1c.

  The carrier 6 that revolves together with the planetary roller 7 is externally fitted to the rotary shaft 4 through a slide bearing 13 having a carrier body 6a made of a sintered material so as to be relatively rotatable, and through a thrust roller bearing 14. Abutting on the end face of the shaft support member 8, the movement of the rotating shaft 4 toward the base end side is restricted. The slide bearing 13 may be formed of resin, ceramics, a metal such as an aluminum alloy or a copper alloy, or a composite material thereof. Each planetary roller 7 is rotatably supported on a support pin 6b of the carrier 6 by a needle roller bearing 15, and a holding plate 6c fixed to the support pin 6b with a retaining ring 16 on the opposite side to the carrier body 6a. It is prevented from coming off and its rotation is supported by the carrier body 6 a by a thrust roller bearing 17.

  A retaining ring 18 is mounted on the distal end side of the rotating shaft 4, and a holding plate 6 c of the carrier 6 is brought into contact with the retaining ring 18 via a slide bearing 19 formed of a sintered material, so that the distal end side of the rotating shaft 4. The movement of the carrier 6 is restricted. The slide bearing 19 may also be formed of a resin, ceramics, a metal such as an aluminum alloy or a copper alloy, or a composite material thereof. The holding plate 6c is integrally formed with a partial cylindrical portion 6d extending to the planetary roller 7 side, and a fan-shaped lubricant is applied to the outer diameter surface of the planetary roller 7 on the inner diameter side of the partial cylindrical portion 6d. The member 20 is held. The outer diameter surface of the partial cylindrical portion 6d also serves as a guide surface that guides the upper surface of the spiral protrusion formed by the strip member 5b of the outer ring member 5 described later. Further, a seal member 21 having a cylindrical peripheral edge portion is fitted into the inner diameter surface of the end portion of the outer ring member 5 so as to block the inner diameter portion where the planetary roller 7 and the lubricant application member 20 are arranged from the outside. ing. The seal member 21 is formed by pressing a thin steel plate. The seal member 21 can also be formed of resin or rubber.

  A driven object is connected to the front end side of the outer ring member 5, and a key 22 is provided on the front end surface of the outer ring member 5 so as not to be rotated by the driven object. Accordingly, the outer ring member 5 fitted in the inner diameter surface of the cylindrical portion 1a of the housing 1 so as to be slidable in the axial direction moves relative to the carrier 6 in which the axial movement in both directions is restricted, and outputs linearly. It becomes a member. The cylindrical portion 1a on the side where the driven object is connected to the outer ring member 5 is open, and the outer ring member 5 is guided in a long length in the axial direction on the inner diameter surface of the cylindrical portion 1a and protrudes from the cylindrical portion 1a. Smooth linear motion with long strokes.

  As shown in FIG. 4 (a), two spiral grooves 5a are provided on the inner diameter surface of the outer ring member 5 to which the planetary rollers 7 are in rolling contact, and separate strip members are attached around the spiral grooves 5a. 5 b, two spiral ridges are formed on the inner diameter surface of the outer ring member 5. The two spiral ridges have an equivalent lead angle α defined by the equation (1) of 0.3 ° or less, and can secure a load holding function so that the outer ring member 5 is not pushed back. ing.

  Further, as shown in FIG. 4B, the spiral ridge formed by the strip member 5b is fitted in the outer diameter surface of the planetary roller 7, and the lead angle is different at the same pitch as the spiral ridge. A spiral groove 7a is provided. Due to the engagement of the spiral ridges and the spiral grooves 7a, the planetary roller 7 that revolves while rotating around the rotation shaft 4 has a shaft angle with the outer ring member 5 due to the difference in the lead angle between the spiral ridges and the spiral grooves 7a. Move relative to the direction. The reason why the spiral ridges of the outer ring member 5 are two multi-threads is to increase the degree of freedom in setting the difference in the lead angle with the spiral groove 7a of the planetary roller 7. Articles may be used. Further, the spiral groove 7a of the planetary roller 7 can be a circumferential groove having the same pitch as the spiral protrusion.

  As shown in FIG. 5, the outer circumferential surface of the spiral groove 7a formed on the outer circumferential surface of the planetary roller 7 is formed by a strip member 5b with inclined side walls so that the groove width extends from the groove bottom side to the groove edge side. The inner surface of the spiral ridge 5 is inclined at an angle equal to the inclination angle of the side wall of the spiral groove 7a so that the width of the spiral ridge narrows from the base side to the top side. Accordingly, when the planetary roller 7 is in rolling contact with the inner surface of the outer ring member 5 and the spiral ridges of the outer ring member 5 are fitted into the spiral grooves 7a having different lead angles, the shoulders of the spiral ridges are There is no contact with the groove edge of the spiral groove 7a.

  The rotating shaft 4, the strip member 5 b forming the spiral ridge and the planetary roller 7 are carburized using a low carbon steel having a carbon content of 0.3 mass% or less as a material. A hard plating layer 23 formed by hard Cr plating as a surface hardening treatment is formed on the outer surface including the radial surface, the surface of the strip member 5b, and the spiral groove 7a of the planetary roller 7. These hard plating layers 23 may be formed by a hard plating process such as Ni-B plating or Ni-P plating.

  FIG. 6 shows a modification of the spiral ridge of the outer ring member 5 of FIG. In this modification, the spiral ridges are formed integrally with the outer ring member 5, and the rotating shaft 4, the outer ring member 5 and the planetary roller 7 are hardened with a medium carbon steel having a carbon content of 0.3 mass% as a material, The outer diameter surface of the rotating shaft 4, the inner diameter surface of the outer ring member 5 including the surface of the spiral protrusion, and the outer diameter surface including the surface of the spiral groove 7 a of the planetary roller 7 are hardened by hard Cr plating. A plating layer 23 is formed.

  FIG. 7 shows an electric brake device that employs the electric linear actuator described above. This electric brake device is a disc brake in which a brake pad 33 as a brake member is disposed oppositely on both sides of a disc rotor 32 as a braked member inside the caliper body 31, and the electric linear actuator is connected to the caliper body 31. The outer ring member 5 as an output member that linearly moves is locked to a brake pad 33 as a driven object by a key 22 so that the brake pad 33 is pressed against the disc rotor 32. In this figure, the electric linear actuator is shown in a cross section orthogonal to the cross section shown in FIG.

  In the embodiment and the modification described above, the entire surface of the spiral ridges on the outer diameter surface of the rotating shaft, the outer diameter surface of the planetary roller, and the inner diameter surface of the outer ring member are subjected to surface hardening treatment. A part of the processing can be omitted.

DESCRIPTION OF SYMBOLS 1 Housing 1a Cylindrical part 1b Flange 1c Cover 2 Electric motor 2a Rotor shaft 3a, 3b, 3c Gear 4 Rotating shaft 5 Outer ring member 5a Spiral groove 5b Strip member 6 Carrier 6a Carrier main body 6b Support pin 6c Holding plate 6d Partial cylindrical part 7 Planet Roller 7a Spiral groove 8 Shaft support member 9 Ball bearing 10 Retaining ring 11 Shaft pin 12 Ball bearing 13 Sliding bearing 14 Thrust roller bearing 15 Needle roller bearing 16 Retaining ring 17 Thrust roller bearing 18 Retaining ring 19 Sliding bearing 20 Lubricant application member 21 Seal member 22 Key 23 Hard plating layer 31 Caliper body 32 Disc rotor 33 Brake pad

Claims (10)

  A plurality of planetary rollers rotatably supported by the carrier are interposed between a rotating shaft to which rotation is transmitted from the electric motor and an outer ring member fitted into the inner diameter surface of the housing on the outer diameter side of the rotating shaft. These planetary rollers revolve while rotating around the rotation axis as the rotation shaft rotates, and provided with spiral ridges on the inner diameter surface of the outer ring member, on the outer diameter surface of the planetary roller, The outer ring member and the carrier are provided with a circumferential groove into which the spiral ridges are fitted at the same pitch as the spiral ridges, or a spiral groove into which the spiral ridges are fitted at different pitches and the same pitch as the spiral ridges. The motor linearly drives the driven object connected to the linearly moving output member by converting the rotational motion of the rotary shaft into the linear motion of the output member in the axial direction. In the actuator, the carrier As an output member that linearly moves the outer ring member as an output member that restricts the movement of the outer ring member in the axial direction, prevents the outer ring member from rotating, and is fitted inside the inner diameter surface of the housing so as to be slidable in the axial direction. At least one of an outer diameter surface, an outer diameter surface of each planetary roller, and an inner diameter surface of the outer ring member is subjected to a surface hardening process.   2. The electric linear actuator according to claim 1, wherein the spiral protrusion provided on the inner diameter surface of the outer ring member is formed of a strip member that is circumferentially attached to a spiral groove provided on the inner diameter surface of the outer ring member.   The electric linear actuator according to claim 2, further comprising a guide surface that guides an upper surface of a spiral protrusion formed by a strip member that surrounds the spiral groove.   The surface hardening process is performed on at least one of the surface of the spiral protrusion provided on the inner surface of the outer ring member and the circumferential groove or the surface of the spiral groove provided on the outer surface of the planetary roller. The electric linear actuator described in the above.   The electric linear actuator according to claim 1, wherein the surface hardening treatment is a hard plating treatment.   The electric linear motion according to any one of claims 1 to 5, wherein the member subjected to the surface hardening treatment is carburized using a low carbon steel having a carbon content of 0.3 mass% or less as a raw material. Actuator.   The electric type according to any one of claims 1 to 5, wherein the member subjected to the surface hardening treatment is subjected to quenching and tempering treatment using a medium carbon steel having a carbon content exceeding 0.3 mass% as a material. Linear actuator.   The electric type according to any one of claims 1 to 7, wherein at least one of a spiral protrusion provided on an inner diameter surface of the outer ring member and a spiral groove provided on an outer diameter surface of the planetary roller is a multi-helix. Linear actuator. The electric linear actuator according to any one of claims 1 to 8, wherein an equivalent lead angle α represented by the following equation (1) of the spiral protrusion is set to 0.5 ° or less.

  An electric brake device that includes an electric linear actuator that linearly drives a brake member by converting a rotational movement of the electric motor into a linear movement, and presses the brake member that is linearly driven against the member to be braked. An electric brake device using the electric linear actuator according to any one of claims 1 to 9 as a dynamic actuator.

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