JP2008089084A - Electric linear motion actuator and electric brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the axial length of a whole electric linear motion actuator. <P>SOLUTION: An electric motor 2 is installed in parallel to a cylindrical part 1a on a flange 1b arranged on one end side of the cylindrical part 1a of a casing 1, and the whole axial length can be shortened by transmitting rotation of a rotor shaft 2a of the electric motor 2 to a rotary shaft 4 of the linear motion actuator arranged in the center of the cylindrical part 1a by gears 3a, 3b and 3c. <P>COPYRIGHT: (C)2008,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).

  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 2).

  Usually, since the electric brake device is attached under the spring of the vehicle, it is desired to be able to operate stably even under vibration from the road surface and to be designed compactly.

JP-A-6-327190 (Figs. 1 and 5) JP 2003-343620 A (FIG. 1)

  The ball screw mechanism and the ball ramp mechanism employed in the above-described conventional electric linear actuator have a certain degree of boosting function by the motion conversion mechanism along the lead screw thread and the inclined cam surface. A large boosting function as required by a brake device or the like cannot be secured. For this reason, in the electric linear actuator that employs these motion conversion mechanisms, the drive force is increased by incorporating a separate reduction mechanism as described above, but a gear reduction mechanism such as a planetary gear reduction mechanism is incorporated. Impedes the compact design of the electric linear actuator.

  For such problems, the present applicant can secure a large boosting function without incorporating a separate speed reduction mechanism, and an electric motor 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 interposed between the rotor shaft of the rotor and an outer ring member fixed to the inner diameter surface of the casing on the outer diameter side of the rotor shaft. Is rotated around the rotor shaft as the rotor shaft rotates, and spiral ridges are provided on the outer diameter surface of the rotor shaft or the inner diameter surface of the outer ring member, and a spiral is formed on the outer diameter surface of each planetary roller. While rotating the circumference of the rotor shaft by providing a circumferential groove in which the spiral ridge fits at the same pitch as the ridge, or a spiral groove in which the lead angle is different and the spiral ridge fits in the same pitch as the spiral ridge Revolve The carrier for supporting the planetary rollers are relatively moved in the axial direction, it has proposed a mechanism for converting the rotary motion of the rotor shaft to linear motion of the carrier previously (Japanese Patent Application No. 2005-217250, Japanese Patent Application No. 2005-217429).

  In the electric linear actuator described above, the components of the linear actuator are arranged on the outer diameter side of the rotor shaft of the electric motor, and the electric motor and the linear actuator are arranged in series on the same axis. There is a problem that the overall axial length is increased.

  Accordingly, an object of the present invention is to shorten the axial length of the entire electric linear actuator.

  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 interposed between the outer ring member and each planetary roller so as to revolve while rotating around the rotation shaft as the rotation shaft rotates. A circumferential groove in which spiral ridges are provided on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member, and the spiral ridges are fitted on the outer diameter surface of each planetary roller at the same pitch as the spiral ridges. Alternatively, a spiral groove in which the spiral ridges are fitted at the same pitch as the spiral ridges and the spiral ridges are fitted is provided, and the carrier supporting each planetary roller that revolves while rotating around the rotation shaft is relatively moved in the axial direction. Rotation of the rotating shaft The dynamic and converted into linear motion of the carrier, the electric linear motion actuator for linearly driving a driven object, adopting the structure of arranging the rotating shaft so as not coaxially to the rotor axis of the electric motor.

  That is, by arranging the rotation axis of the linear actuator so as not to be coaxial with the rotor shaft of the electric motor, the overall axial length can be shortened.

  By disposing the rotating shaft in parallel with the rotor shaft of the electric motor, the overall axial length can be made the shortest and the outer shape can be made compact with less irregularities.

  The rotation may be transmitted from the rotor shaft of the electric motor to the rotation shaft using a gear.

  The spiral ridges provided on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member are formed by the strip members that surround the spiral grooves provided on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member. Thus, the spiral ridge can be easily formed with high accuracy.

  An inner diameter surface of the casing for fixing the outer ring member is formed by a cylindrical surface, and an annular groove is provided on the inner diameter surface of the casing formed by the cylindrical surface, and the axial direction of the linear motion actuator generated in the outer ring member is formed in the annular groove By inserting the stopper that receives the reaction force, the inner diameter surface of the casing can be easily processed from both directions, and the outer ring member can be inserted into the casing from both directions to improve the assemblability.

  By forming the stopper fitted into the annular groove with a plurality of arcuate members, the stopper can be easily fitted into the annular groove.

  By providing means for holding the inner diameter surface of the stopper formed of the plurality of arcuate members, it is possible to prevent the stopper from falling off the annular groove.

  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 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. At the same time, the axial length of the entire linear actuator can be shortened.

  Since the electric linear actuator of the present invention is arranged so that the rotation shaft of the linear actuator is not coaxial with the rotor shaft of the electric motor, the overall axial length can be shortened.

  By disposing the rotating shaft in parallel with the rotor shaft of the electric motor, the overall axial length can be made the shortest and the outer shape can be made compact with less irregularities.

  The spiral ridges provided on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member are formed by the strip members that surround the spiral grooves provided on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member. Thus, the spiral ridge can be easily formed with high accuracy.

  The inner surface of the casing for fixing the outer ring member is formed by a cylindrical surface, and an annular groove is provided on the inner surface of the casing formed by the cylindrical surface, and the axial direction reaction of the linear motion actuator generated in the outer ring member is formed in the annular groove. By inserting a stopper for receiving a force, the inner diameter surface of the casing can be easily processed from both directions, and the outer ring member can be inserted into the casing from both directions to improve assemblability.

  By forming the stopper fitted into the annular groove with a plurality of arcuate members, the stopper can be easily fitted into the annular groove.

  By providing means for holding the inner diameter surface of the stopper formed of the plurality of arcuate members, it is possible to prevent the stopper from falling off the annular groove.

  The electric brake device of the present invention uses the electric linear actuator described above 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, and the linear actuator The overall axial length can be shortened.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 5 show the electric linear actuator of the first embodiment. 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 inner diameter surface of the cylindrical portion 1a, three planetary rollers 7 rotatably supported by the carrier 6 are interposed, and each planetary roller 7 revolves around the rotating shaft 4 while rotating around it.

  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 the lid 1d by a ball bearing 8, and the intermediate gear 3b meshing with the gear 3a and the gear 3c attached to the rotor shaft 2a is a shaft passed between the flange 1b and the lid 1d. The pin 9 is attached via a ball bearing 10.

  An annular groove 11 is provided on the inner diameter surface of the cylindrical portion 1a of the casing 1, and a stopper 12 that receives the axial reaction force of the linear motion actuator generated in the outer ring member 5 is fitted into the annular groove 11, and the inner diameter surface thereof. A ring-shaped holding member 13 is fixed to the inner diameter surface of the cylindrical portion 1a. The holding member 13 is partially cut away in the circumferential direction so as not to interfere with the intermediate gear 3b.

  Each planetary roller 7 is rotatably supported by a needle roller bearing 14 on a support shaft 6 a of a carrier 6 fitted on the rotary shaft 4, and its rotation is supported by the carrier 6 by a thrust ball bearing 15. Further, a linear drive member 16 is supported by a thrust ball bearing 17 on the carrier 6 that revolves together with each planetary roller 7 so that the linear motion of each planetary roller 7 is transmitted to the linear drive member 16 via the carrier 6. It has become.

  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 the strip members having a square cross section 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. 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. 4A and 4B, the spiral directions of the spiral ridge and the spiral groove 7a appear to be opposite to each other, but the spiral shown in FIG. Since the ridge is screwed into the portion on the back side of the spiral groove 7a shown in FIG. 4B, the directions of the spirals of both 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 FIG. 5A, the stopper 12 is formed by three arcuate members 12a having a central angle slightly smaller than 120 °, and a gap is opened in the circumferential direction between the arcuate members 12a. And can be easily fitted into the annular groove 11 of the casing 1. Even if the stopper 12 is divided in this manner, the inner diameter surface is held by the holding member 13, so that it does not fall off the annular groove 11.

  FIG. 5B shows a modification of the stopper 12. The stopper 12 is formed by four arcuate members 12a, and a gap is formed in the circumferential direction between the arcuate members 12a. Note that the number of divisions of the stopper 12 into the arcuate member 12a may be two or more.

  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 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 16. 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 16 is prevented from rotating by the key 24 on the brake pad 23 on the pressing side.

  7 and 8 show the electric linear actuator of the second embodiment. This electric linear actuator is provided with a flange 1b that projects so as to form a corner at one end of the cylindrical portion 1a of the casing 1, and the electric motor 2 is attached to the flange 1b at a right angle to the cylindrical portion 1a. The rotation of the rotor shaft 2a of the electric motor 2 is transmitted from the worm 3d attached to the rotor shaft 2a to the gear 3c attached to the rotation shaft 4, and the cylindrical portion 1a and the flange 1b are connected to each other. The worm 3d and the gear 3c are arranged so as to mesh with each other in a space covered with the peripheral wall 1c and the lid 1d connected to the outer periphery. The holding member 13 holding the stopper 12 is partially cut away in the circumferential direction so as not to interfere with the rotor shaft 2a to which the worm 3d is attached. Other parts are the same as those of the first embodiment.

  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 the same pitch as the spiral protrusion and the lead angle is different on the outer diameter surface of the planetary roller. The outer circumferential surface of the planetary roller can be provided with circumferential grooves having the same pitch as the spiral ridges.

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. a and b are front views showing the spiral ridge of the outer ring member and the spiral groove of the planetary roller in FIG. a is a front view showing the stopper of FIG. 1, and b is a front view showing a modification of a. 1 is a longitudinal sectional view showing an electric brake device employing the electric linear actuator of FIG. A longitudinal sectional view showing an electric linear actuator of a second embodiment Sectional view along line VIII-VIII in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 1a Cylindrical part 1b Flange 1c Peripheral wall 1d Lid 2 Electric motor 2a Rotor shaft 3a, 3b, 3c Gear 3d Worm 4 Rotating shaft 5 Outer ring member 5a Spiral groove 5b Strip member 6 Carrier 7 Planetary roller 7a Spiral groove 8 Ball bearing 9 Shaft Pin 10 Ball bearing 11 Annular groove 12 Stopper 12a Arc-shaped member 13 Holding member 14 Needle roller bearing 15 Thrust ball bearing 16 Linear drive member 17 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 spiral ridges are formed on the outer diameter surface of the rotation shaft or the inner diameter 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. Providing a spiral groove to be rotated, relatively moving the carrier supporting each planetary roller that revolves around the rotating shaft in the axial direction, and converting the rotational motion of the rotating shaft into the linear motion of the carrier; Electricity that drives the driven object linearly In Formula linear actuator, electric linear motion actuator, characterized in that the rotary shaft is arranged so as not coaxially to the rotor axis of the electric motor.   The electric linear actuator according to claim 1, wherein the rotary shaft is arranged in parallel with a rotor shaft of the electric motor.   The electric linear actuator according to claim 1 or 2, wherein a rotation is transmitted from a rotor shaft of the electric motor using a gear on the rotating shaft.   The spiral protrusion provided on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member is formed by a strip member that is attached to a spiral groove provided on the outer diameter surface of the rotating shaft or the inner diameter surface of the outer ring member. Item 4. The electric linear actuator according to any one of Items 1 to 3.   An inner diameter surface of the casing for fixing the outer ring member is formed by a cylindrical surface, and an annular groove is provided on the inner diameter surface of the casing formed by the cylindrical surface, and the axial direction of the linear motion actuator generated in the outer ring member is formed in the annular groove The electric linear actuator according to any one of claims 1 to 4, wherein a stopper for receiving a reaction force is fitted.   The electric linear actuator according to claim 5, wherein the stopper fitted into the annular groove is formed of a plurality of arc-shaped members.   The electric linear actuator according to claim 6, further comprising means for holding an inner diameter surface of a stopper formed by the plurality of arcuate members.   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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