JP2008286386A - Electric direct-acting actuator and electric brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relax a contact pressure of an edge portion of a circumferential groove or a helical groove on a planet roller rolling-contacting an outer diameter surface of a rotating shaft and an inner diameter surface of an outer ring member. <P>SOLUTION: The edge portion of the helical groove 7a on the planet roller 7 is subjected to chamfering 7b, which relaxes the contact pressure of the edge portion of the helical groove 7a rolling-contacting the outer diameter surface of the rotating shaft and the inner diameter surface of the outer ring member 5. <P>COPYRIGHT: (C)2009,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.

  With respect to such a problem, the present inventors can secure a large boosting function without incorporating a separate speed reduction mechanism, and as an electric linear actuator suitable for an electric brake device having a small linear stroke, A plurality of planetary rollers rotatably supported by a carrier are provided between a rotating shaft to which rotation is transmitted from the rotor shaft of the motor and an outer ring member fixed to the inner surface of the casing on the outer diameter side of the rotating shaft. Rolling contact, each of these planetary rollers revolves while rotating around the rotating shaft as the rotating shaft rotates, and provided with spiral ridges on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member, The outer circumferential surface of each planetary roller is provided with a circumferential groove in which the spiral ridges are fitted at the same pitch as the spiral ridges, or a spiral groove in which the spiral ridges are fitted in the same pitch as the spiral ridges with different lead angles. Around the axis of rotation The carrier for supporting the respective planetary rollers to rolling while revolving by relatively moved in the axial direction, has proposed a mechanism for converting the rotary motion of the rotary shaft into a linear motion of the carrier previously (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). Usually, since the electric brake device is attached under the spring of the vehicle, it is desired that the electric brake device operates stably even when subjected to vibration from the road surface and can be designed compactly.

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

  The electric linear actuators described in Patent Documents 2 and 3 can secure a large boosting function with a compact design without incorporating a separate speed reduction mechanism. However, the planetary roller is composed of the outer diameter surface of the rotating shaft and the outer ring member. Since it is sandwiched between the inner diameter surface and is brought into rolling contact with the outer diameter side so as to be compressed, the circumferential groove of the outer diameter surface or the groove edge of the spiral groove is formed between the outer diameter surface of the rotating shaft and the outer ring member. Rolling contact is made with a high contact pressure while being in contact with the inner diameter surface, and the circumferential edge of the planetary roller or the spiral groove, or the outer diameter surface of the rotating shaft and the inner diameter surface of the outer ring member, which are in contact with the high contact pressure, roll. There is a problem of dynamic fatigue and shortening the durable life.

  Accordingly, an object of the present invention is to relieve the contact pressure at which the circumferential edge of the planetary roller or the groove edge of the spiral groove is in rolling contact with the outer diameter surface of the rotating shaft and the inner diameter surface of the outer ring member.

  In order to solve the above-described problems, an electric linear actuator according to the present invention is fixed to the inner diameter surface of the casing on the outer diameter side of the rotating shaft that transmits the rotation from the rotor shaft of the electric motor. A plurality of planetary rollers rotatably supported by the carrier are brought into rolling contact with the outer ring member so that each of the planetary rollers revolves while rotating around the rotation shaft as the rotation shaft rotates. In the circumferential direction, a spiral ridge is provided on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member, and the spiral ridge is fitted on the outer diameter surface of each planetary roller at the same pitch as the spiral ridge. Provide a groove or a spiral groove in which the lead angle is different at the same pitch as the spiral ridge, and the spiral ridge is fitted, and the carrier supporting each planetary roller that revolves while rotating around the rotation axis is relatively relative to the axial direction. Move and rotate the rotating shaft The dynamic and converted into linear motion of the carrier, the electric linear motion actuator for linearly driving a driven object, employing the configuration chamfered groove edge portion of the circumferential groove or a spiral groove.

  That is, by chamfering the circumferential edge of the planetary roller or the groove edge of the spiral groove, the circumferential edge of the planetary roller or the groove edge of the spiral groove is rotated with the outer diameter surface of the rotating shaft and the inner diameter surface of the outer ring member. The contact pressure that comes into contact can be relaxed.

  The chamfer may be formed by a single or a plurality of R curves.

  The radius of curvature R of the R curve is preferably 0.05 to 0.3 mm. This is because if the curvature radius R is less than 0.05 mm, the edge contact cannot be sufficiently prevented, and if it exceeds 0.3 mm, it takes time and effort.

  The chamfer may be formed by a single line or a plurality of straight lines.

  The chamfer may be formed by combining an R curve and a straight line.

  Chamfering can be easily performed by forming the chamfering by barrel polishing.

  The chamfer can also be formed by cutting.

  The electric brake device according to the present invention includes an electric linear actuator that linearly drives the brake member by converting the rotational motion of the electric motor into a linear motion, and presses the brake member that is linearly driven against the member to be braked. In the electric brake device, any one of the electric linear actuators described above is used as the electric linear actuator so that the brake can be operated with a large linear driving force without incorporating a separate speed reduction mechanism. .

  The electric linear actuator of the present invention is such that the circumferential edge of the planetary roller or the groove edge of the spiral groove is chamfered so that the circumferential edge of the planetary roller or the groove edge of the spiral groove is the outer diameter surface of the rotating shaft. Since the contact pressure of rolling contact with the inner diameter surface of the outer ring member and the inner ring surface of the outer ring member has been relaxed, rolling fatigue at the groove edge of the planetary roller, the outer diameter surface of the rotating shaft, and the inner diameter surface of the outer ring member is suppressed, and their durability life is extended. can do.

  Chamfering can be easily performed by forming the chamfering by barrel polishing.

  In the electric brake device of the present invention, since the above-described electric linear actuator is used as the electric linear actuator, the brake can be operated with a large linear driving force without incorporating a separate speed reduction mechanism.

  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 that projects so as to form a bowl shape on one end side of the cylindrical portion 1a of the casing 1, and an electric motor is provided on the flange 1b. 2 is mounted in parallel with the cylindrical portion 1a, and 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 gears 3a, 3b, 3c. Between the rotating shaft 4 and the outer ring member 5 fixed to the cylindrical inner surface of the cylindrical portion 1a, three planetary rollers 7 rotatably supported by the support shaft 6a of the carrier 6 are interposed. Each planetary roller 7 revolves while rotating around the rotating shaft 4 as it rotates. In addition, between the adjacent planetary rollers 7, three fan-shaped lubricant application members 8 for applying grease as a lubricant are disposed in sliding contact with the outer diameter surfaces of the planetary rollers 7 on both sides. ing. Each lubricant application member 8 is housed in a bottomed partial cylindrical case 9 attached to the support shaft 6 a of the carrier 6.

  On the side of the casing 1 where the flange 1b is provided, there is provided a peripheral wall 1c that continues to the outer periphery including the cylindrical portion 1a and the flange 1b, and a lid 1d is attached to the peripheral wall 1c, and the gears 3a, 3b, 3c are The inner wall 1c and the lid 1d are arranged so as to mesh with each other within the same axial cross section. The rotary shaft 4 to which the gear 3c is attached is supported by a ball bearing 10 in a hole provided in the lid 1d, and the intermediate gear 3b that meshes with the gear 3a attached to the rotor shaft 2a and the gear 3c has a flange 1b and a lid 1d. Is supported by a ball bearing 12 on a shaft pin 11 passed to

  An annular groove 13 is provided in the inner diameter surface of the cylindrical portion 1a of the casing 1, and a stopper 14 that receives the axial reaction force of the linear motion actuator generated in the outer ring member 5 is fitted into the annular groove 13, and the inner diameter surface thereof. An annular holding member 15 is fixedly fitted on the inner diameter surface of the cylindrical portion 1a. The stopper 14 is divided into a plurality in the circumferential direction and can be easily fitted into the annular groove 13, and the holding member 15 is partially cut away in the circumferential direction so as not to interfere with the intermediate gear 3 b. .

  Each planetary roller 7 is supported by a support shaft 6 a of a carrier 6 fitted on the rotary shaft 4 so as to be rotatable by a needle roller bearing 16, and its rotation is supported by the carrier 6 by a thrust ball bearing 17. Further, a linear drive member 18 is supported by a thrust ball bearing 19 on the carrier 6 that revolves together with each planetary roller 7, and the linear motion of each planetary roller 7 is transmitted to the linear drive member 18 via the carrier 6. It has become.

  As shown in FIG. 4 (a), two spiral grooves 5a are provided on the inner surface of the outer ring member 5 to which the planetary rollers 7 are in rolling contact, and the strip members 5b are circumferentially attached to the spiral grooves 5a. Two spiral ridges are formed on the inner diameter surface of the outer ring member 5. Further, as shown in FIG. 4B, the spiral ridge formed by the strip member 5b is fitted into the outer diameter surface of each planetary roller 7, and the lead angle is different at the same pitch as the spiral ridge. One spiral groove 7a is provided. 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 ridges shown in FIGS. 4 (a) and 4 (b) and the spiral direction of the spiral groove 7a seem to be opposite to each other, but the spiral ridges shown in FIG. 4 (a). Is screwed into the portion on the back side of the spiral groove 7a shown in FIG. 4 (b), so that the directions of the spirals are the same. Accordingly, each planetary roller 7 that revolves while rotating around the rotation shaft 4 and whose spiral groove 7a is screwed with the spiral protrusion of the outer ring member 5 has a difference in lead angle between the spiral protrusion and the spiral groove 7a. Move linearly in the axial direction.

  As shown in an enlarged view in FIG. 5 (a), a chamfer formed on the groove edge of the spiral groove 7a of the planetary roller 7 by a single R curve having a curvature radius R of 0.05 to 0.3 mm. 7b is applied. Therefore, the contact pressure between the outer diameter surface of the rotating shaft 4 and the inner diameter surface of the outer ring member 5 where the groove edge portion of the spiral groove 7a is in rolling contact is relieved.

  FIG. 5 (b) shows another embodiment of the spiral groove 7 a of the planetary roller 7 and the spiral ridge of the outer ring member 5. In this embodiment, when the spiral ridge is fitted into the spiral groove 7a while the planetary roller 7 is in rolling contact with the inner diameter surface of the outer ring member 5, the shoulder of the spiral ridge contacts the groove edge of the spiral groove 7a. In order to prevent the spiral groove 7a from extending from the groove bottom side to the groove edge side, the side walls on both sides are inclined, and the spiral protrusions are spirally formed on both side surfaces so that the width of the spiral narrows from the base side to the top side. It is inclined at an angle equal to the inclination angle of the side wall of the groove 7a. Also in this embodiment, the chamfer 7b formed by the single R curve of the curvature radius R is given to the groove edge part of the spiral groove 7a.

  6A, 6B, 6C, and 6D show modifications of the chamfer 7b applied to the groove edge of the spiral groove 7a shown in FIG. 5B, respectively. 6A shows a chamfer 7b formed with a single straight line, FIG. 6B shows a chamfer 7b formed with two straight lines, and FIG. 6C shows a chamfer 7b with a radius of curvature. FIG. 6D shows a chamfer 7b formed by combining one straight line and two R curves having a radius of curvature R.

  The chamfer 7b shown in FIGS. 5 (a), 5 (b) and 6 (a), (b), (c), (d) is formed using one or both of barrel polishing and cutting. Has been.

  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 brake pads 23 as brake members are arranged oppositely on both sides of a disc rotor 22 as a braked member inside the caliper body 21, and the electric linear actuator is connected to the caliper body 21. The brake pad 23 is pressed against the disc rotor 22 by the linear drive member 18. In this figure, the electric linear actuator is shown in a cross section orthogonal to the cross section shown in FIG. 1, and the linear drive member 18 is locked to the pressing brake pad 23 by a key 24.

  In the embodiment described above, the spiral protrusion is provided on the inner diameter surface of the outer ring member, and the spiral groove having a different lead angle is provided on the outer diameter surface of the planetary roller. Circumferential grooves having the same pitch may be provided, and the spiral ridges may be provided on the outer diameter surface of the rotating shaft.

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. (A) is sectional drawing which expands and shows the helical groove | channel of the planetary roller of FIG. 1, and the spiral protrusion of an outer ring member, (b) is sectional drawing which shows other embodiment of (a). (A), (b), (c), (d) is sectional drawing which shows the modification of the chamfering of FIG.5 (b), respectively. 1 is a longitudinal sectional view showing an electric brake device employing the electric linear actuator of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 1a Cylindrical part 1b Flange 1c Perimeter wall 1d Lid 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 Support shaft 7 Planetary roller 7a Spiral groove 7b Chamfer 8 Lubrication Agent application member 9 Case 10 Ball bearing 11 Axle pin 12 Ball bearing 13 Annular groove 14 Stopper 15 Holding member 16 Needle roller bearing 17 Thrust ball bearing 18 Linear drive member 19 Thrust ball bearing 21 Caliper body 22 Disc rotor 23 Brake pad 24 Key

Claims (8)

  A plurality of planetary rollers rotatably supported by a carrier between a rotating shaft to which rotation is transmitted from the rotor shaft of the electric motor and an outer ring member fixed to the inner diameter surface of the casing on the outer diameter side of the rotating shaft These planetary rollers revolve while rotating around the rotation shaft as the rotation shaft rotates, and spirally project on the outer diameter surface of the rotation shaft or the inner diameter surface of the outer ring member. A circumferential groove in 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 each planetary roller. A spiral groove is provided, and the carrier supporting each planetary roller that revolves while rotating around the rotation shaft is relatively moved in the axial direction, and the rotational motion of the rotation shaft is converted into the linear motion of the carrier. , The power to drive the driven object linearly In Formula linear actuator, electric linear motion actuator, characterized in that chamfered groove edge portion of the circumferential groove or a spiral groove.   The electric linear actuator according to claim 1, wherein the chamfer is formed by a single or a plurality of R curves.   The electric linear actuator according to claim 2, wherein a curvature radius R of the R curve is 0.05 to 0.3 mm.   The electric linear motion actuator according to claim 1, wherein the chamfer is formed by a single or a plurality of straight lines.   The electric linear actuator according to claim 1, wherein the chamfer is formed by combining an R curve and a straight line.   The electric linear actuator according to any one of claims 1 to 5, wherein the chamfer is formed by barrel polishing.   The electric linear actuator according to any one of claims 1 to 5, wherein the chamfer is formed by cutting.   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 7 as a dynamic actuator.

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