JP2011179539A - Electric linear motion actuator and electric brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly guide linear motion of an output member even when the lateral moment acts on the output member performing linear motion, and to apply a radial direction preload to a planetary roller at inexpensive processing cost. <P>SOLUTION: When the axial movement of a carrier 6 supporting the planetary roller 7 is regulated, an outer ring member 5 fitted internally to the inner diameter face of a cylindrical part 1a in a housing 1 axially slidably is locked to a driven object connected to it by a key 22 so that the outer ring member 5 serves as the linearly moving output member. At the same time, when the front end face of a spiral projecting line 5a arranged on the inside diameter face of the outer ring member 5 is brought into contact with a groove bottom face of a spiral groove 7a in the planetary roller 7 from the radial direction, a radial direction preload is applied to the planetary roller 7. <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 actuator described above has a radial preload on the planetary roller interposed between the rotary shaft and the outer ring member in order to stably transmit the rotational torque of the rotary shaft serving as the input shaft to the planetary roller. Must be granted.

  Conventionally, the preload in the radial direction of the planetary roller is performed by a method in which the outer diameter surface of the planetary roller is brought into contact with the outer diameter surface of the rotating shaft and the inner diameter surface of the outer ring member with a tightening margin. Is polished. For this reason, when the spiral ridges are formed integrally with the outer ring member, it takes time and effort to polish the inner diameter surface between the narrow spiral ridges of the outer ring member with which the outer diameter surface of the planetary roller comes into contact. There was a problem of getting higher.

  In addition, when a separate strip member is wound around the spiral groove provided on the inner diameter surface of the outer ring member to form a spiral projection, the inner diameter surface can be easily polished before the strip member is looped. The one with the separate strip member is inferior in durability as compared with the one in which the spiral projection is integrally formed.

  Therefore, an object of the present invention is to make it possible to smoothly guide the linear movement of the output member even when a lateral moment acts on the linearly moving output member, and to reduce the radial direction to the planetary roller at a low processing cost. It is to be able to apply preload.

  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 is adopted in which the tip surface of the spiral protrusion provided on the inner diameter surface of the outer ring member is brought into contact with the planetary roller in the radial direction to apply a radial preload to the planetary roller.

  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 inner surface between the narrow spiral ridges of the outer ring member is obtained by bringing the tip surface of the spiral ridge provided on the inner surface of the outer ring member into contact with the planetary roller in the radial direction and applying a radial preload to the planetary roller. Therefore, the radial preload can be applied to the planetary roller at a low processing cost.

  The convex tip surface of the spiral ridge can be brought into contact with a circumferential groove of the planetary roller or a groove bottom surface of the spiral groove.

  The convex tip surface of the spiral ridge can be brought into contact with the outer diameter surface of the small diameter portion provided in a part of the planetary roller in the axial direction.

  The small diameter part of the planetary roller can be provided at both ends in the axial direction.

  The small-diameter portion of the planetary roller can be provided at the central portion in the axial direction.

  The small diameter portion of the planetary roller can be formed of a separate cylindrical member.

  The separate cylindrical member can be fixed to the planetary roller by press-fitting.

  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.

  Each of the electric linear actuators described above is suitable for the spiral ridge formed integrally with the inner surface of the outer ring member.

  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 a radial preload can be applied to the planetary roller at a low processing cost.

  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 the tip end surface of the spiral protrusion provided on the inner diameter surface of the outer ring member is brought into contact with the planetary roller in the radial direction so that a radial preload is applied to the planetary roller. Even if a lateral moment acts on the linearly moving output member, the linear motion of the output member can be smoothly guided, and a radial preload can be applied to the planetary roller at a low processing cost. .

  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 it acts as a lateral moment on the linearly moving output member, the linear motion of the output member can be smoothly guided, and a radial preload can be applied to the planetary roller at a low processing cost. it can.

1 is a longitudinal sectional view showing an electric linear actuator according to a first embodiment. Sectional view along the line II-II in FIG. Sectional view along line III-III in FIG. 1 is an enlarged longitudinal sectional view showing the main part of FIG. 1 is a longitudinal sectional view showing an electric brake device employing the electric linear actuator of FIG. The longitudinal cross-sectional view which expands and shows the principal part of the electric linear actuator of 2nd Embodiment The longitudinal cross-sectional view which expands and shows the principal part of the electrically driven linear actuator of 3rd Embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 4 show a first embodiment. 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.

  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. 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 an enlarged view in FIG. 4, two trapezoidal spiral ridges 5 a are formed on the inner diameter surface of the outer ring member 5, and the spiral ridges 5 a are fitted on the outer diameter surface of the planetary roller 7. It has a trapezoidal shape, and is provided with one spiral groove 7a having the same pitch as the spiral ridge 5a and having a different lead angle, and rotates around the rotation shaft 4 by screwing of the spiral ridge 5a and the spiral groove 7a. However, the planetary roller 7 that revolves moves relative to the outer ring member 5 in the axial direction due to the difference in the lead angle between the spiral protrusion 5a and the spiral groove 7a. The reason why the spiral ridges 5a of the outer ring member 5 are two multi-threads is to increase the degree of freedom in setting the difference in lead angle with the spiral groove 7a of the planetary roller 7, and the spiral ridges 5a. May be one. The spiral groove 7a of the planetary roller 7 may be a circumferential groove having the same pitch as that of the spiral protrusion 5a.

  The spiral ridge 5a of the outer ring member 5 has its tip end surface in contact with the groove bottom surface of the spiral groove 7a of the planetary roller 7, and applies a radial preload to the planetary roller 7. The tip surface of 5a and the groove bottom surface of the spiral groove 7a are polished. The planetary roller 7 and the rotating shaft 4 are in contact with each other at the outer diameter surfaces, and these outer diameter surfaces are also polished. The planetary roller 7 revolves while rotating around the rotating shaft 4 without slipping due to the radial preload, and the rotational torque of the rotating shaft 4 is stably transmitted.

  FIG. 5 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.

  FIG. 6 shows a second embodiment. This electric linear actuator has the same basic configuration as that of the first embodiment. Small diameter stepped portions 7b are provided at both ends of the planetary roller 7, and each small diameter stepped portion 7b A separate cylindrical member 23 having a diameter smaller than the outer diameter of the planetary roller 7 is press-fitted and fixed, and the distal end surface of the spiral protrusion 5a of the outer ring member 5 comes into contact with the outer diameter surface of the cylindrical member 23, thereby causing the planetary surface. The difference is that a radial preload is applied to the roller 7. In this embodiment, the outer diameter surface of the cylindrical member 23 is polished, and the groove bottom surface of the spiral groove 7a is not polished. Other parts are the same as those of the first embodiment.

  FIG. 7 shows a third embodiment. The basic configuration of this electric linear actuator is the same as that of the first embodiment. A small-diameter portion 7c having a small outer diameter is provided at the center of the planetary roller 7, and the spiral of the outer ring member 5 is provided. The difference is that the front end surface of the ridge 5a comes into contact with the small diameter portion 7c, and the planetary roller 7 is given a preload in the radial direction. In this embodiment, the outer diameter surface of the small diameter portion 7c is polished, and the groove bottom surface of the spiral groove 7a is not polished.

  In the embodiment described above, the spiral ridges on the inner diameter surface of the outer ring member are integrally formed. However, the spiral ridges form a spiral groove on the inner diameter surface of the outer ring member, and a separate strip fitted into the spiral groove. It can also be formed of a 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 ridge 6 Carrier 6a Carrier main body 6b Support pin 6c Holding plate 6d Partial cylindrical part 7 Planetary roller 7a Spiral groove 7b Small diameter step 7c Small diameter 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 Cylindrical member 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, the outer ring member is fitted into the inner diameter surface of the housing so as to be slidable in the axial direction. An electric linear motion actuator characterized in that a radial preload is applied to the planetary roller by bringing a tip end surface of a spiral ridge provided on an inner diameter surface into contact with the planetary roller in a radial direction.   2. The electric linear actuator according to claim 1, wherein a convex tip surface of the spiral ridge is brought into contact with a circumferential groove of the planetary roller or a groove bottom surface of the spiral groove.   2. The electric linear actuator according to claim 1, wherein a convex tip surface of the spiral ridge is brought into contact with an outer diameter surface of a small diameter portion provided in a part of an axial direction of the planetary roller.   The electric linear actuator according to claim 3, wherein a small diameter portion of the planetary roller is provided at both end portions in the axial direction.   The electric linear actuator according to claim 3, wherein a small diameter portion of the planetary roller is provided at a central portion in an axial direction.   The electric linear actuator according to any one of claims 3 to 5, wherein the small-diameter portion of the planetary roller is formed of a separate cylindrical member.   The electric linear actuator according to claim 6, wherein the separate cylindrical member is fixed to the planetary roller by press-fitting.   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 motion actuator according to any one of claims 1 to 8, wherein the spiral protrusion is formed integrally with an inner diameter surface of the outer ring member.   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.

Images