JP2011179542A - Electromotive linear actuator and electromotive disc brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly guide linear movement of an output member even if lateral moment acts on the linearly moving output member, to eliminate the need for centering of a planetary roller, and to reduce its machining man-hours. <P>SOLUTION: An outer annular member 5, which regulates the axial movement of a carrier 6 supporting a planetary roller 7 and is fitted inside of the inner diameter surface of a cylindrical member 1a of a housing 1 in such a way as to be slidable in the axial direction, is stopped from rotating by a key 21 in a coupled object which is being driven, and the outer annular member 5 serves as the output member which moves linearly. Further, a plurality of support shafts 6b extending in parallel between each planetary roller 7 is provided on the carrier 6, and each planetary roller 7 is rotatably supported by rotatively contacting cylindrical members 18 rotatably externally fit on the support shafts 6b to an outer diameter surface of each planetary roller 7 from the both sides. <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 or linear drive member as an output member connected to the brake member. There is a problem that guidance becomes difficult. 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.

  In addition, the electric linear actuators described in Patent Documents 2 and 3 have a planetary roller having a hollow structure, and a needle roller bearing is provided on a support shaft of a carrier inserted into the center of the planetary roller having the hollow structure. Since the planetary roller is rotatably supported via the outer circumferential surface of the planetary roller, it is necessary to center the circumferential groove and the spiral groove formed by a processing method such as rolling on the outer diameter surface of the planetary roller with respect to the support shaft of the carrier. There is. For this reason, coupled with the processing of the planetary roller into a hollow structure, there is a problem that the number of processing steps of the planetary roller increases and the manufacturing cost increases.

  Therefore, an object of the present invention is to make it possible to smoothly guide the linear movement of the output member even if a lateral moment acts on the linearly moving output member, and to eliminate the need for centering of the planetary roller. It is to reduce man-hours.

  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. The carrier is provided with a plurality of support shafts extending in parallel with the planetary rollers between the plurality of planetary rollers, and a cylindrical member rotatably fitted on these support shafts is provided outside the planetary rollers. A configuration was adopted in which each planetary roller was rotatably supported by rolling contact with the radial surface from both sides.

  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 carrier is provided with a plurality of support shafts extending in parallel with the planetary rollers between the plurality of planetary rollers, and a cylindrical member rotatably fitted on these support shafts is provided on both sides of the outer diameter surface of each planetary roller. The planetary rollers are supported in a freely rotating manner so that the centering of the planetary rollers is unnecessary and the number of processing steps can be reduced.

  By making the planetary roller a solid structure, the number of processing steps can be further reduced.

  By forming the support shaft by a separate member and fixing the support shaft formed by the separate member to the carrier by fitting or screwing, the processing yield of the carrier can be increased.

  The cylindrical member can be formed of a resin material.

  The cylindrical member may be formed of a metal material.

  The cylindrical member can also be formed of a sintered material.

  By supporting the cylindrical member on the support shaft with a rolling bearing, the cylindrical member can be more smoothly brought into rolling contact with the outer diameter surface of the planetary roller.

  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 forming the strip member by drawing a metal, it is possible to increase the strength by work hardening using an inexpensive metal material with few alloy components and to form the strip member at a high yield at a low cost. Further, if the strip member is wound in a spiral shape during the drawing process, it is possible to facilitate the circumferential attachment to the spiral groove.

  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.

  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, the centering of the planetary roller is not required, and the number of processing steps can be reduced.

  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. The member is an output member that linearly moves, and the carrier is provided with a plurality of support shafts extending in parallel with the planetary rollers between the plurality of planetary rollers, and a cylindrical member that is rotatably fitted around these support shafts. Since each planetary roller is rotatably supported on the outer diameter surface of each planetary roller from both sides, even if a lateral moment acts on the linearly moving output member, the linear motion of the output member is smooth It is possible to guide and eliminate the need for centering of the planetary roller, and the number of processing steps can be reduced.

  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, the centering of the planetary roller is not required, and the processing man-hour can be reduced. it can.

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) is sectional drawing which expands and shows the support shaft and cylindrical member of FIG. 1, (b) is sectional drawing which shows the modification of (a). (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. 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. The gears 3a, 3b, and 3c may be spur gears or helical gears, and the material may be a resin that can be reduced in weight, or a sintered material that can be easily molded, in addition to a metal such as steel. it can. The gears 3a, 3b, and 3c may be formed of different materials. 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 restrict 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.

  A carrier 6 that revolves together with the planetary roller 7 is fixed to the carrier body 6a and the carrier body 6a by fitting, and extends between the four planetary rollers 7 in parallel with the planetary roller 7 to be described later. The support plate 6c includes four support shafts 6b that rotatably support the member 18 and press plates 6c that are attached to the front ends of these support shafts 6b and prevent the planetary roller 7 from coming off. A partial cylindrical portion 6d extending toward the planetary roller 7 on the outer diameter side of the shaft 6b is integrally formed. 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.

  The carrier body 6a is externally fitted to the rotary shaft 4 through a sliding bearing 13 formed of a sintered material so as to be relatively rotatable, and is in contact with the end surface of the shaft support member 8 through a thrust roller bearing 14. Movement of the carrier 6 toward the base end side of the rotating shaft 4 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. Further, the holding plate 6c is brought into contact with a retaining ring 16 attached to the tip of the rotating shaft 4 via a slide bearing 15 formed of a sintered material, and the carrier 6 moves toward the tip of the rotating shaft 4. Is regulated. The slide bearing 15 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 planetary roller 7 has a solid structure, and the rotation of the planetary roller 7 is supported by the carrier body 6a by a thrust roller bearing 17, and a cylindrical member that is externally fitted to the support shafts 6b extending between the planetary rollers 7. 18 is in rolling contact with the outer diameter surface of each planetary roller 7 from both sides, and each planetary roller 7 is rotatably supported by the carrier 6.

  As shown in FIG. 4A, the cylindrical member 18 fitted on the support shaft 6b is formed of a metal material, and is rotatably supported by a pair of needle roller bearings 19 as rolling bearings on the support shaft 6b. ing. FIG. 4B shows a modification of the cylindrical member 18. The cylindrical member 18 is formed of a resin material or a sintered material, and is externally fitted to the support shaft 6b so as to be freely rotatable due to its self-lubricating property.

  As shown in FIG. 1, a seal member 20 having a cylindrical peripheral edge portion is provided on 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 cylindrical member 18 are disposed from the outside. It is fitted. The seal member 20 is formed by pressing a thin steel plate. The seal member 20 can also be formed of resin or rubber.

  A driven object is connected to the distal end side of the outer ring member 5, and a key 21 that is prevented from rotating by the driven object is provided on the distal end surface. 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. 5 (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 circumferentially attached to the spiral grooves 5a. 5 b, two spiral ridges are formed on the inner diameter surface of the outer ring member 5. The strip member 5b is formed by drawing a low carbon steel, and the strength is increased by work hardening.

  Further, as shown in FIG. 5 (b), the spiral ridge formed by the strip member 5b is fitted into the outer diameter surface of the planetary roller 7, and the lead pitch is different at the same pitch as the spiral ridge 1 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. The spiral groove 7a of the planetary roller 7 may be a circumferential groove having the same pitch as that of the spiral protrusion.

  FIG. 6 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 21 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 described above, the number of planetary rollers is four, but the number of planetary rollers is not limited to four. Further, the cylindrical member supported by each support shaft may be brought into contact with the planetary rollers on both sides adjacent to each other as in the embodiment, or may be brought into contact with the planetary rollers individually.

  In the above-described embodiment, the spiral protrusion on the inner diameter surface of the outer ring member is formed by a separate stripe member fitted in the spiral groove. However, the spiral protrusion can be formed integrally with the outer ring member.

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 shaft 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 Sliding bearing 16 Retaining ring 17 Thrust roller bearing 18 Cylindrical member 19 Needle roller bearing 20 Seal member 21 Key 31 Caliper body 32 Disc rotor 33 Brake pad

Claims (11)

  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 The outer ring member is prevented from rotating, and is fitted into the inner diameter surface of the housing so as to be slidable in the axial direction, and the outer ring member serves as an output member that linearly moves to the carrier. A plurality of support shafts extending in parallel to the planetary rollers are provided between the plurality of planetary rollers, and a cylindrical member rotatably fitted on these support shafts is rolled onto the outer diameter surface of each planetary roller from both sides. An electric linear actuator, wherein the planetary rollers are in contact with each other and are rotatably supported.   The electric linear actuator according to claim 1, wherein the planetary roller has a solid structure.   The electric linear actuator according to claim 1 or 2, wherein the support shaft is formed of a separate member, and the support shaft formed of the separate member is fixed to the carrier by fitting or screwing.   The electric linear actuator according to any one of claims 1 to 3, wherein the cylindrical member is formed of a resin material.   The electric linear actuator according to claim 1, wherein the cylindrical member is made of a metal material.   The electric linear actuator according to claim 1, wherein the cylindrical member is formed of a sintered material.   The electric linear actuator according to claim 1, wherein the cylindrical member is supported on the support shaft by a rolling bearing.   The electric linear actuator according to any one of claims 1 to 7, 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 8, wherein the strip member is formed by metal drawing.   The electric linear actuator according to claim 8 or 9, further comprising a guide surface that guides an upper surface of a spiral protrusion formed by a strip member that surrounds the spiral groove.   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 10 as a dynamic actuator.

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