JP2017223301A - Planetary roller screw type linear motion mechanism and electric brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch a load conversion rate according to an axial load applied to an object from an outer ring member, and to easily finish a cylindrical surface on which a planetary roller on the outer circumference of a rotating shaft rolls and contacts by polishing or the like. It provides a planetary roller screw type linear motion mechanism capable of. SOLUTION: In a planetary roller screw type linear motion mechanism in which an outer ring member 5 moves in an axial direction by engaging a spiral ridge 16 on the inner circumference of an outer ring member 5 with a circumferential groove 17 on the outer circumference of a planetary roller 13, a shaft. The carrier 14 is supported by the elastic member 35 so as to move relative to the rotating shaft 8 due to the reaction force in the rearward direction, and when the carrier 14 does not move relative to the rotating shaft 8, it is frictionally coupled with the carrier 14. When the carrier 14 is relatively moved with respect to the rotating shaft 8, a tapered surface 38 for releasing frictional coupling with the carrier 14 is provided on the outer periphery of the rotating shaft 8, and the tapered surface 38 is axially oriented with respect to the planetary roller 13. It is located behind. [Selection diagram] Fig. 2

Description

  The present invention relates to a planetary roller screw type linear motion mechanism used for an electric linear motion actuator and an electric brake device using the planetary roller screw type linear motion mechanism.

  As a linear motion mechanism that converts an externally input rotational motion into a linear motion and outputs the linear motion, for example, a planetary roller screw type linear motion mechanism as in Patent Document 1 is known.

  The planetary roller screw type linear motion mechanism of Patent Document 1 is capable of rotating a rotating shaft to which rotation is input from the outside, a plurality of planetary rollers that are in rolling contact with an outer peripheral cylindrical surface of the rotating shaft, and the plurality of planetary rollers. And a carrier that is revolved and an outer ring member that is disposed so as to surround the plurality of planetary rollers. A spiral ridge is provided on the inner periphery of the outer ring member, and a spiral groove or a circumferential groove that engages with the spiral ridge is provided on the outer periphery of each planetary roller.

  In this planetary roller screw type linear motion mechanism, when rotation is input from the outside to the rotating shaft, the rotation of the rotating shaft is transmitted to the planetary roller that is in rolling contact with the outer periphery of the rotating shaft, and each planetary roller rotates. Revolve around the axis of rotation. At this time, the outer ring member moves in the axial direction by the engagement of the spiral groove or circumferential groove on the outer periphery of the planetary roller and the spiral protrusion on the inner periphery of the outer ring member. In this way, the planetary roller screw type linear motion mechanism converts the rotation of the rotation shaft into a linear motion of the outer ring member.

  This planetary roller screw type linear motion mechanism can be used for an electric brake device. In this case, when the brake is applied, the rotation of the electric motor is converted into a linear motion of the brake pad by the planetary roller screw type linear motion mechanism, and the brake pad is pressed against the brake disc. On the other hand, when releasing the brake, the electric motor is rotated in the reverse direction, and a clearance is provided between the brake pad and the brake disk.

  Here, if the lead angle of the spiral protrusion on the inner periphery of the outer ring member is set to be large, the moving speed in the axial direction of the outer ring member is increased, so that it is necessary for the brake pad to come into contact with the brake disc when the brake is applied. Although the time is shortened and the responsiveness of the brake can be improved, the load conversion rate is reduced, but there is a problem that the force with which the brake pad presses the brake disc is reduced. On the other hand, if the lead angle of the spiral protrusion on the inner periphery of the outer ring member is set to be small, the load conversion rate increases, so that it is possible to increase the force with which the brake pad presses the brake disc when braking. However, since the moving speed of the outer ring member in the axial direction is slow, the time required for the brake pad to come into contact with the brake disk becomes long, and the response of the brake is lowered. That is, there is a conflict between increasing the response of the brake and increasing the force with which the brake pad presses the brake disc.

  Therefore, in Patent Document 1, in order to improve both the response of the brake and increase the force with which the brake pad presses the brake disc, a load is applied according to the axial load applied to the object from the outer ring member. It proposes a structure that changes conversion rate.

  That is, the carrier is made of an elastic member so that the carrier moves relative to the rotation axis in the axial rearward direction by the reaction force in the axial rearward direction that is received when the outer ring member applies a load in the axial direction forward to the object. I support it. In addition, when the carrier is not moved relative to the rotation axis in the axial direction rearward, the carrier is frictionally coupled with the carrier so as to limit the relative rotation between the carrier and the rotation axis, and the carrier is moved rearward in the axial direction with respect to the rotation axis. In the state of relative movement, a friction coupling portion for releasing the frictional coupling with the carrier is provided on the outer periphery of the rotation shaft so as to allow relative rotation between the carrier and the rotation shaft. Here, the friction coupling portion is a tapered surface provided on the outer periphery of the front end portion in the axial direction of the rotating shaft so that the diameter gradually increases from the cylindrical surface with which the planetary roller is in rolling contact toward the front in the axial direction.

Japanese Patent No. 5496836

  In the above planetary roller screw type linear motion mechanism, the inventor of the present application, when finishing the cylindrical surface with which the planetary roller on the outer periphery of the rotating shaft is in rolling contact with high precision by polishing or the like, the shape of the rotating shaft is the finish processing. I noticed a difficult shape.

  That is, in the planetary roller screw type linear motion mechanism of Patent Document 1, a tapered surface having a diameter gradually increasing from the cylindrical surface to which the planetary roller is in rolling contact toward the front in the axial direction is provided. And this taper surface is a site | part which has an outer diameter larger than the cylindrical surface which a planetary roller rolls and contacts. Therefore, it is not possible to adopt a low-cost processing method (for example, centerless through polishing) that processes the outer periphery of the rotating shaft while rolling and supporting the outer periphery of the rotating shaft, and the cylindrical surface on which the planetary roller is in contact with the rolling is highly accurate. There exists a problem that the processing cost for finishing becomes high.

  The problem to be solved by the present invention is that the load conversion rate can be switched according to the axial load applied to the object from the outer ring member, and the planetary roller on the outer periphery of the rotating shaft is in rolling contact with the cylindrical surface It is to provide a planetary roller screw type linear motion mechanism that can be easily finished by polishing or the like.

In order to solve the above problems, the present invention provides a planetary roller screw type linear motion mechanism having the following configuration.
A rotating shaft having a cylindrical surface on the outer periphery;
A plurality of planetary rollers in rolling contact with the cylindrical surface;
A carrier that holds the plurality of planetary rollers in a rotatable and revolving manner;
An outer ring member disposed so as to surround the plurality of planetary rollers and supported so as to be movable in the axial direction;
A spiral ridge provided on the inner periphery of the outer ring member;
A spiral groove or a circumferential groove provided on the outer periphery of each planetary roller so as to engage with the spiral protrusion,
In the planetary roller screw type linear motion mechanism in which the outer ring member moves in the axial direction by the engagement of the spiral ridge and the spiral groove or the circumferential groove,
The carrier moves so that the carrier moves relative to the rotational axis in the other axial direction by a reaction force in the other axial direction received when a load is applied to the outer ring member in one axial direction. An elastic member that supports
Provided on the outer periphery of the rotating shaft, and when the carrier does not move relative to the rotating shaft in the other axial direction, the carrier and the friction coupling so as to limit the relative rotation of the carrier and the rotating shaft A friction coupling portion that releases the frictional coupling between the carrier and the carrier so as to allow relative rotation between the carrier and the rotation shaft when the carrier moves relative to the rotation axis in the other axial direction; With
The planetary roller screw type linear motion mechanism, wherein the frictional coupling portion is disposed on the other side in the axial direction with respect to the planetary roller.

  In this way, in a state where no load is applied to the object from the outer ring member, the friction coupling portion on the outer periphery of the rotation shaft is frictionally coupled with the carrier, and the relative rotation between the carrier and the rotation shaft is limited. Therefore, when rotation is input from the outside to the rotating shaft, the carrier revolves integrally with the rotating shaft, and the planetary roller revolves around the rotating shaft without rotating. At this time, the revolution speed of the planetary roller is relatively fast. Therefore, the moving speed of the outer ring member in the axial direction is increased, and the load conversion rate is reduced. On the other hand, in a state where a load is applied from the outer ring member to the object, the frictional coupling between the frictional coupling portion on the outer periphery of the rotating shaft and the carrier is released, and relative rotation between the carrier and the rotating shaft is allowed. Therefore, when rotation is input from the outside to the rotating shaft, the planetary roller revolves around the rotating shaft while rotating. At this time, the revolution speed of the planetary roller is relatively slow. Therefore, the moving speed of the outer ring member in the axial direction becomes slow, and the load conversion rate increases. Thus, the load conversion rate can be switched according to the axial load applied to the object from the outer ring member.

  In addition, the friction coupling portion on the outer periphery of the rotating shaft is usually in a shape having a portion having a small diameter from one axial direction (front in the axial direction) to the other axial direction (back in the axial direction). A cylindrical surface on which the planetary roller is in rolling contact with the planetary roller because it is disposed in the other axial direction (axial direction opposite to the direction in which the load is applied to the object from the outer ring member, that is, axially rearward). Can be the maximum diameter portion of the rotating shaft. Therefore, it is possible to employ a low-cost processing method (for example, centerless through polishing) that processes the outer periphery of the rotating shaft while rolling and supporting the outer periphery of the rotating shaft, and polishing the cylindrical surface on which the planetary roller is in rolling contact. It is possible to finish easily.

  As the friction engagement portion, a tapered surface whose outer diameter decreases from one axial direction to the other can be employed.

  In this way, when the carrier and the frictional coupling portion on the outer periphery of the rotating shaft are frictionally coupled, a large frictional force can be generated by the wedge action of the tapered surface.

Moreover, in this invention, the thing of the following structures is also provided together as an electric brake device using said planetary roller screw type linear motion mechanism.
A planetary roller screw type linear motion mechanism configured as described above;
An electric motor that rotationally drives the rotating shaft of the planetary roller screw type linear motion mechanism;
A brake pad that moves integrally with the outer ring member of the planetary roller screw type linear motion mechanism;
A brake disc disposed opposite the brake pad;
Electric brake device having

  The planetary roller screw type linear motion mechanism of the present invention can switch the load conversion rate according to the axial load applied to the object from the outer ring member. Further, since the friction coupling portion on the outer periphery of the rotating shaft is disposed on the other side in the axial direction with respect to the planetary roller, the cylindrical surface on which the planetary roller is in rolling contact can be the maximum diameter portion of the rotating shaft. is there. Therefore, it is possible to employ a low-cost processing method (for example, centerless through polishing) that processes the outer periphery of the rotating shaft while rolling and supporting the outer periphery of the rotating shaft, and polishing the cylindrical surface on which the planetary roller is in rolling contact. It is possible to finish easily.

Sectional drawing which shows the electric linear motion actuator incorporating the planetary roller screw-type linear motion mechanism of embodiment of this invention FIG. 1 is an enlarged cross-sectional view of the vicinity of the planetary roller screw type linear motion mechanism of FIG. Sectional view along line III-III in FIG. FIG. 2 is an enlarged sectional view in the vicinity of the elastic member of FIG. The figure which shows the state by which the reaction force to the axial direction back was loaded on the carrier of FIG. Sectional drawing which shows an example of the electric brake device using the electric linear motion actuator shown in FIG. The figure which looked at the electric brake equipment shown in Drawing 6 from the inner side

  FIG. 1 shows an electric linear motion actuator 2 using a planetary roller screw type linear motion mechanism 1 according to an embodiment of the present invention. The electric linear actuator 2 includes an electric motor 3, a reduction gear train 4 that decelerates and transmits the rotation of the electric motor 3, and rotation input from the electric motor 3 via the reduction gear train 4. And a planetary roller screw type linear motion mechanism 1 for converting and outputting the linear motion.

  The reduction gear train 4 includes an input gear 7 fixed to the motor shaft 6 of the electric motor 3, an output gear 9 fixed to the rotation shaft 8 of the planetary roller screw type linear motion mechanism 1, and the input gear 7 and the output gear 9. An intermediate gear 10 that transmits the rotation between the two gears and a gear case 11 that houses these gears 7, 9, 10. The reduction gear train 4 decelerates the rotation input to the input gear 7 from the motor shaft 6 of the electric motor 3 by sequentially transmitting the input gear 7, the intermediate gear 10, and the output gear 9 having different numbers of teeth, The decelerated rotation is output from the output gear 9 to the rotary shaft 8.

  As shown in FIGS. 2 and 3, the planetary roller screw type linear motion mechanism 1 includes a rotating shaft 8 having a cylindrical surface 12 on the outer periphery, a plurality of planetary rollers 13 that are in rolling contact with the cylindrical surface 12, and the plurality of planetary planets. A carrier 14 that holds the roller 13 so that it can rotate and revolve, a hollow cylindrical outer ring member 5 that is disposed so as to surround the plurality of planetary rollers 13, and a housing 15 that accommodates the outer ring member 5 so as to be movable in the axial direction. And have. The plurality of planetary rollers 13 are arranged at intervals in the circumferential direction between the inner circumference of the outer ring member 5 and the outer circumference of the rotating shaft 8.

  Here, the direction parallel to the rotation shaft 8 is the axial direction, and the movement direction of the outer ring member 5 when the outer ring member 5 moves to the side where the protruding length of the outer ring member 5 from the housing 15 increases is the axial front (one side). ), The movement direction of the outer ring member 5 when the outer ring member 5 moves to the side where the protruding length of the outer ring member 5 from the housing 15 becomes smaller is the rear side in the axial direction (the other side), and the direction around the rotating shaft 8 Defined as direction.

  As shown in FIG. 2, spiral ridges 16 are provided on the inner periphery of the outer ring member 5. The spiral ridge 16 is a ridge that extends obliquely with a predetermined lead angle with respect to the circumferential direction. On the outer circumference of each planetary roller 13, a plurality of circumferential grooves 17 that engage with the spiral ridges 16 are formed at intervals in the axial direction. The interval between the circumferential grooves 17 adjacent to each other in the axial direction on the outer circumference of each planetary roller 13 is the same as the pitch of the spiral ridges 16. Here, the circumferential groove 17 having a lead angle of 0 degree is provided on the outer periphery of the planetary roller 13, but a spiral groove having a lead angle different from that of the spiral protrusion 16 may be provided instead of the circumferential groove 17. .

  As shown in FIGS. 2 and 3, the carrier 14 includes a plurality of support pins 18 that rotatably support the planetary rollers 13, and an axial front disk 19 that holds an axial front end of each support pin 18. The axial rear disk 20 that holds the axial rear end of each support pin 18, and the axial front disk 19 and the axial rear disk 20 are passed between a plurality of circumferentially adjacent planetary rollers 13. It has the pillar part 21 to connect. The column portion 21 integrates both the disks 19 and 20 so that the axial front disk 19 and the axial rear disk 20 do not move relative to each other in either the axial direction or the circumferential direction.

  As shown in FIG. 2, the axial front disk 19 and the axial rear disk 20 are each formed in an annular shape that penetrates the rotary shaft 8. A slide bearing 22 that is in sliding contact with the outer periphery of the rotary shaft 8 is mounted on the inner periphery of the axially front disk 19.

  Between the inner periphery of each planetary roller 13 and the outer periphery of the support pin 18, a radial bearing 23 that supports the planetary roller 13 so as to rotate is incorporated. A thrust bearing 24 is incorporated between each planetary roller 13 and the axially rear disk 20 to support the planetary roller 13 in the axial direction in a rotatable state. An alignment seat 25 is incorporated between the thrust bearing 24 and the axial rear disk 20 so as to tiltably support the planetary roller 13 via the thrust bearing 24.

  The outer ring member 5 is supported by an inner surface of a receiving hole 26 formed in the housing 15 so as to be slidable in the axial direction. Inside the housing 15, a bearing support member 27 is fixed at a position away from the outer ring member 5 in the axial direction rearward. The bearing support member 27 is formed in an annular shape that allows the rotation shaft 8 to pass therethrough. A radial bearing 28 that rotatably supports the rotary shaft 8 is incorporated in the inner periphery of the bearing support member 27. As the radial bearing 28, for example, a sintered slide bearing or a deep groove ball bearing can be adopted.

  The bearing support member 27 is restricted from moving rearward in the axial direction by a protrusion 29 provided on the inner periphery of the accommodation hole 26, and is moved forward in the axial direction by a retaining ring 30 attached to the inner periphery of the accommodation hole 26. It is regulated. In addition, relative movement of the rotating shaft 8 in the axial direction relative to the bearing support member 27 is restricted by a retaining ring 31 attached to the outer periphery of the rotating shaft 8. In addition, relative movement of the carrier 14 in the axial direction relative to the rotating shaft 8 is restricted by a retaining ring 32 attached to the outer periphery of the front end portion in the axial direction of the rotating shaft 8.

  Here, the radial bearing 28 is incorporated in a state in which relative movement in the axial direction relative to the bearing support member 27 is restricted, and the retaining ring 31 is attached to the radial bearing 28 on the rear side in the axial direction. The retaining ring 32 is attached to the front side in the axial direction with respect to the sliding bearing 22.

  A thrust bearing 33 is incorporated between the carrier 14 and the bearing support member 27 to support the carrier 14 from the rear side in the axial direction in a state where the carrier 14 can revolve. A spacer 34 for transmitting an axial load from the carrier 14 to the thrust bearing 33 is incorporated between the carrier 14 and the thrust bearing 33. An elastic member 35 is incorporated between the carrier 14 and the spacer 34, and an axial gap 36 that allows the carrier 14 to move in the axial direction is provided between the spacer 34 and the carrier 14. As a result, when an axially rearward load is applied to the carrier 14, the elastic member 35 is compressed in the axial direction by the load, and the carrier is within the range of the axial clearance 36 between the carrier 14 and the spacer 34. 14 moves relative to the rotary shaft 8 in the axially rearward direction. Here, the size of the axial gap 36 between the carrier 14 and the spacer 34 is very small. For this reason, the distance that the carrier 14 can move relative to the rotating shaft 8 in the axial direction rearward is extremely short (for example, 0.5 mm or less).

  The elastic member 35 is formed in an annular shape that allows the rotation shaft 8 to pass therethrough. The elastic member 35 is, for example, a disc spring. A wave spring or a coil spring can be employed instead of the disc spring. The elastic member 35 is compressed in the axial direction in a state where no axially rearward load is applied to the carrier 14 and biases the carrier 14. The elastic member 35 is incorporated so that when a load is applied to the carrier 14 in the rearward direction in the axial direction, the amount of compression in the axial direction of the elastic member 35 increases in accordance with the magnitude of the load.

  An accommodation recess 37 is formed on the surface of the spacer 34 facing the carrier 14. A part of the elastic member 35 is accommodated in the accommodating recess 37, and the remaining part of the elastic member 35 protrudes from the accommodating recess 37.

  In this embodiment, the elastic member 35 is incorporated between the carrier 14 and the spacer 34, but the elastic member 35 may be installed at any other position as long as it is between the carrier 14 and the bearing support member 27. The elastic member 35 may be incorporated between the seat 34 and the thrust bearing 33, or the spacer 34 may be constituted by two divided bodies that can move relative to each other in the axial direction, and the elastic member 35 may be incorporated between the two divided bodies. Alternatively, the elastic member 35 may be incorporated between the thrust bearing 33 and the bearing support member 27.

  On the outer periphery of the rotating shaft 8, a cylindrical surface 12 with which the planetary roller 13 is in rolling contact, a tapered surface 38 (friction coupling portion) positioned axially rearward of the cylindrical surface 12, and an axially rearward direction of the tapered surface 38. And a cylindrical surface 39 that is continuous with the cylindrical surface 39. The cylindrical surface 39 is a surface supported by the radial bearing 28, and the outer diameter of the cylindrical surface 39 is smaller than the outer diameter of the cylindrical surface 12.

  As shown in FIG. 4, the tapered surface 38 is a conical surface whose outer diameter decreases from the front side in the axial direction toward the rear side. The inclination angle of the tapered surface 38 (the angle formed by the tapered surface 38 with respect to the direction parallel to the axial direction) is set in the range of 5 to 20 °.

  A tapered inner peripheral surface 40 is formed on the inner periphery of the rear disk 20 in the axial direction of the carrier 14 so as to face the tapered surface 38 on the outer periphery of the rotating shaft 8. The inclination angle of the tapered inner peripheral surface 40 (the angle formed by the tapered inner peripheral surface 40 with respect to the direction parallel to the axial direction) is set in the range of 5 to 20 °. The tapered inner peripheral surface 40 is preferably formed to have the same inclination angle as the tapered surface 38.

  Here, as shown in FIG. 4, in a state where the carrier 14 is not relatively moved rearward in the axial direction with respect to the rotating shaft 8 (that is, a state where the carrier 14 is not loaded with an axial rearward load), The tapered inner peripheral surface 40 of the carrier 14 is in contact with the outer peripheral tapered surface 38 of the rotating shaft 8. At this time, the tapered inner peripheral surface 40 and the tapered surface 38 are frictionally coupled by the force of the elastic member 35, and the relative rotation between the carrier 14 and the rotating shaft 8 is limited by the frictional force between the tapered inner peripheral surface 40 and the tapered surface 38. It becomes a state.

  On the other hand, as shown in FIG. 5, the carrier 14 is relatively moved axially rearward with respect to the rotating shaft 8 (that is, the carrier 14 is loaded with an axial rearward load, and the elastic member 35 is compressed by the load. In an increased amount), the taper inner peripheral surface 40 of the carrier 14 is separated from the taper surface 38 on the outer periphery of the rotary shaft 8. At this time, the frictional coupling between the tapered inner peripheral surface 40 and the tapered surface 38 is released, and the carrier 14 and the rotary shaft 8 are allowed to rotate relative to each other.

  An operation example of the electric linear actuator 2 will be described.

  When the motor shaft 6 of the electric motor 3 shown in FIG. 1 rotates, the rotation is decelerated and transmitted by the reduction gear train 4 and is input to the rotating shaft 8 of the planetary roller screw type linear motion mechanism 1.

  Here, in the state in which no load forward in the axial direction is applied from the outer ring member 5 to the object, the load in the rearward direction in the axial direction is not applied to the carrier 14, and therefore, as shown in FIG. The peripheral surface 40 and the tapered surface 38 on the outer periphery of the rotary shaft 8 are frictionally coupled, and the relative rotation between the carrier 14 and the rotary shaft 8 is restricted. Therefore, when rotation is input from the electric motor 3 shown in FIG. 1 to the rotating shaft 8 via the reduction gear train 4, the carrier 14 revolves integrally with the rotating shaft 8, and the planetary roller 13 rotates without rotating. Revolve around axis 8. The planetary roller 13 and the outer ring member 5 move relative to each other in the axial direction by the engagement of the circumferential groove 17 on the outer periphery of the planetary roller 13 and the spiral ridge 16 on the inner periphery of the outer ring member 5. Since the movement in the axial direction is regulated together with the carrier 14, the planetary roller 13 does not move in the axial direction with respect to the housing 15, and the outer ring member 5 moves in the axial direction with respect to the housing 15.

  At this time, since the carrier 14 revolves integrally with the rotating shaft 8 and the planetary roller 13 revolves around the rotating shaft 8 without rotating, the planetary roller 13 revolves around the rotating shaft 8 while rotating. However, the revolution speed of the planetary roller 13 is relatively high. Therefore, the moving speed of the outer ring member 5 in the axial direction is increased, and the load conversion rate is reduced.

  On the other hand, in a state in which a load in the axial direction forward is applied to the object from the outer ring member 5, the reaction force in the rearward direction received by the outer ring member 5 passes through the planetary roller 13 and the thrust bearing 24 in order. The carrier 14 moves relative to the rotating shaft 8 in the axially rear direction by the reaction force in the axially rearward direction, and the tapered inner peripheral surface 40 of the carrier 14 and the rotating shaft 8 are moved as shown in FIG. The frictional coupling of the outer peripheral taper surface 38 is released, and relative rotation between the carrier 14 and the rotary shaft 8 is allowed. Therefore, when rotation is input from the electric motor 3 shown in FIG. 1 to the rotary shaft 8 via the reduction gear train 4, the planetary roller 13 revolves around the rotary shaft 8 while rotating around the support pin 18. . The planetary roller 13 and the outer ring member 5 move relative to each other in the axial direction by the engagement of the circumferential groove 17 on the outer periphery of the planetary roller 13 and the spiral ridge 16 on the inner periphery of the outer ring member 5. Since the movement in the axial direction is regulated together with the carrier 14, the planetary roller 13 does not move in the axial direction with respect to the housing 15, and the outer ring member 5 moves in the axial direction with respect to the housing 15.

  At this time, since the planetary roller 13 revolves around the rotating shaft 8 while rotating, the revolving speed of the planetary roller 13 is relatively slower than the case where the planetary roller 13 does not rotate and revolves around the rotating shaft 8. It will be a thing. Therefore, the moving speed of the outer ring member 5 in the axial direction becomes slow, and the load conversion rate increases.

  As described above, in the electric linear actuator 2, the load conversion rate is switched according to the axial load applied from the outer ring member 5 to the object. By using the electric linear actuator 2 in the electric brake device, it is possible to improve both the response of the brake and increase the pressing force of the brake, as will be described later.

  6 and 7 show an electric brake device using the electric linear actuator 2 having the above-described configuration. The electric brake device includes a brake disc 50 that rotates integrally with a wheel (not shown), a mounting bracket 51 that is fixed to the vehicle body so as not to move in the axial direction with respect to the brake disc 50, and the mounting bracket 51. A caliper body 52 supported so as to be slidable in parallel with the axial direction of the brake disc 50, an inner side brake pad 53 and an outer side brake pad 54 opposed in the axial direction with the brake disc 50 interposed therebetween, and an inner side brake pad And an electric linear actuator 2 for moving 53 in the axial direction. A minute clearance 55 is provided between the inner brake pad 53 and the brake disc 50. The inner brake pad 53 and the outer brake pad 54 are held by the mounting bracket 51 so as to be movable in the axial direction and immovable in the circumferential direction.

  The caliper body 52 includes a claw portion 56 that faces the back surface of the outer brake pad 54 in the axial direction and an outer shell portion 57 that faces the outer diameter side of the brake disc 50. The outer shell portion 57 is formed integrally with the housing 15 of the electric linear actuator 2. The outer shell 57 of the caliper body 52 and the housing 15 of the electric linear actuator 2 may be formed separately and integrated with bolts or the like. The outer ring member 5 is disposed on the back surface of the inner side brake pad 53 so that the inner side brake pad 53 moves together with the outer ring member 5 when the outer ring member 5 moves.

  At the end of the outer ring member 5 on the brake disc 50 side, an engagement recess 59 is formed to engage with an engagement protrusion 58 formed on the back surface of the inner brake pad 53. The outer ring member 5 is prevented from rotating by the engagement of the engagement recess 59.

  An operation example of this electric brake device will be described.

  When the brake is applied, when the electric motor 3 (see FIG. 1) rotates, the rotation is transmitted from the electric motor 3 to the rotary shaft 8 via the reduction gear train 4, and the rotation is caused by the planetary roller screw type linear motion mechanism 1. The inner side brake pad 53 is pushed and moved forward in the axial direction by the outer ring member 5. At this time, until the inner brake pad 53 comes into contact with the brake disc 50, as shown in FIG. 4, the carrier 14 is frictionally coupled to the tapered surface 38 of the rotary shaft 8, so the outer ring shown in FIG. The member 5 moves in the axial direction at a relatively high speed. Therefore, the time required for the inner brake pad 53 to contact the brake disc 50 is short, and the response of the brake can be improved.

  Thereafter, when the inner brake pad 53 comes into contact with the brake disc 50 and an axial load is applied from the inner brake pad 53 to the brake disc 50, the carrier 14 moves relative to the rotating shaft 8 as shown in FIG. 5. Since the carrier 14 and the taper surface 38 of the rotating shaft 8 are released relative to each other in the axial direction, the axial movement speed of the outer ring member 5 shown in FIG. 1 is slowed and the load conversion rate is large. Thus, a large axial load is generated. Therefore, the force with which the inner brake pad 53 presses the brake disc 50 can be increased.

  As described above, when the electric linear actuator 2 is used in the electric brake device, it is possible to improve both the response of the brake and increase the force with which the brake pad presses the brake disc 50. .

  As described above, the planetary roller screw type linear motion mechanism 1 of this embodiment has a friction coupling portion on the outer periphery of the rotary shaft 8 in a state where no load is applied to the object from the outer ring member 5 in the axial direction. Since the carrier 14 is frictionally coupled and the relative rotation between the carrier 14 and the rotary shaft 8 is limited, the moving speed of the outer ring member 5 in the axial direction is increased, and the load conversion rate is reduced. On the other hand, in a state in which a load in the axial direction is applied to the object from the outer ring member 5, the frictional coupling between the friction coupling portion on the outer periphery of the rotating shaft 8 and the carrier 14 is released, and the relative rotation between the carrier 14 and the rotating shaft 8 is released. Is allowed, the moving speed of the outer ring member 5 in the axial direction is reduced, and the load conversion rate is increased. As described above, the planetary roller screw type linear motion mechanism 1 can switch the load conversion rate according to the axial load applied to the object from the outer ring member 5.

  Further, the planetary roller screw type linear motion mechanism 1 of this embodiment has a low cost such as centerless through polishing when the cylindrical surface 12 on which the planetary roller 13 on the outer periphery of the rotary shaft 8 is in rolling contact is finished with high accuracy. It is possible to adopt this processing method.

  That is, for example, the taper surface 38 in FIG. 2 is disposed axially forward (left side in the drawing) with respect to the cylindrical surface 12 with which the planetary roller 13 is in rolling contact, and the taper inner peripheral surface 40 is disposed on the inner periphery of the axial front disk 19. However, since the tapered surface 38 has a larger outer diameter than the cylindrical surface 12, the cylindrical surface 12 with which the planetary roller 13 is brought into rolling contact is finished by polishing or the like. Therefore, there is a problem that a low-cost processing method (for example, centerless through polishing) cannot be adopted, and the processing cost for finishing the cylindrical surface 12 with high accuracy is increased.

  On the other hand, in the planetary roller screw type linear motion mechanism 1 of this embodiment, the tapered surface 38 (friction coupling portion) on the outer periphery of the rotary shaft 8 is disposed rearward in the axial direction with respect to the planetary roller 13 (cylindrical surface 12). Therefore, the cylindrical surface 12 with which the planetary roller 13 is in rolling contact can be the maximum diameter portion of the rotating shaft 8. Therefore, it is possible to employ a low-cost processing method (processing that rolls and supports the outer periphery of the rotating shaft 8 while polishing. For example, centerless through polishing), and the cylindrical surface 12 can be easily finished. Centerless through-polishing uses a grinding wheel that rotates at a fixed position and an adjustment wheel that rotates at a position opposite to the grinding wheel with the workpiece sandwiched between them. This is a processing method for continuously polishing the outer periphery of a workpiece while feeding the workpiece in the axial direction.

  As the friction coupling portion, for example, an axis orthogonal surface connecting between the cylindrical surface 12 and the cylindrical surface 39 can be adopted. However, when the tapered surface 38 is employed as the friction coupling portion as in the above embodiment, the carrier When it is frictionally coupled to 14, it is possible to generate a large frictional force by the wedge action of the tapered surface 38.

  In the present embodiment, the rotary shaft 8 and the carrier 14 are frictionally coupled, but a member that rotates integrally with the carrier 14 and the rotary shaft 8 may be frictionally coupled. For example, the elastic member 35 is provided between the spacer 34 and the thrust bearing 33 so that the spacer 34 rotates integrally with the carrier 14, and the spacer 34 frictions with the tapered surface 38 on the outer periphery of the rotating shaft 8. You may provide the taper inner peripheral surface 40 to couple | bond.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Planetary roller screw type linear motion mechanism 3 Electric motor 5 Outer ring member 8 Rotating shaft 12 Cylindrical surface 13 Planetary roller 14 Carrier 16 Spiral protrusion 17 Circumferential groove 35 Elastic member 38 Tapered surface 50 Brake disk 53 Inner side brake pad

Claims (3)

A rotating shaft (8) having a cylindrical surface (12) on its outer periphery;
A plurality of planetary rollers (13) in rolling contact with the cylindrical surface (12);
A carrier (14) for holding the plurality of planetary rollers (13) in a rotatable and revolving manner;
An outer ring member (5) disposed so as to surround the plurality of planetary rollers (13) and supported so as to be movable in the axial direction;
A spiral ridge (16) provided on the inner periphery of the outer ring member (5);
A spiral groove or a circumferential groove (17) provided on the outer periphery of each planetary roller (13) so as to engage with the spiral protrusion (16);
In the planetary roller screw type linear motion mechanism in which the outer ring member (5) moves in the axial direction by the engagement of the spiral protrusion (16) and the spiral groove or the circumferential groove (17),
The carrier (14) is axially moved with respect to the rotating shaft (8) by a reaction force to the other axial direction received when a load is applied to the object in the axial direction on the outer ring member (5). An elastic member (35) that supports the carrier (14) so as to move relative to the other;
When provided on the outer periphery of the rotating shaft (8) and the carrier (14) is not moved relative to the rotating shaft (8) in the other axial direction, the carrier (14) and the rotating shaft ( 8) When the carrier (14) is frictionally coupled with the carrier (14) so as to limit the relative rotation of the carrier (14) and the carrier (14) moves relative to the other axis in the axial direction, the carrier (14) ) And the friction coupling part for releasing the frictional coupling with the carrier (14) so as to allow relative rotation of the rotating shaft (8),
The planetary roller screw type linear motion mechanism characterized in that the frictional coupling portion is disposed on the other side in the axial direction with respect to the planetary roller (13).   The planetary roller screw type linear motion mechanism according to claim 1, wherein the friction engagement portion is a tapered surface (38) whose outer diameter decreases from one axial direction to the other. The planetary roller screw type linear motion mechanism (1) according to claim 1 or 2,
An electric motor (3) for rotationally driving the rotating shaft (8) of the planetary roller screw type linear motion mechanism (1);
A brake pad (53) that moves integrally with the outer ring member (5) of the planetary roller screw type linear motion mechanism (1);
A brake disc (50) disposed opposite the brake pad (53);
Electric brake device having

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