JP2018009660A - Planetary roller screw type linear motion mechanism and electric brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the reliability of a motion of a planetary roller screw type linear motion mechanism which can switch a load conversion rate according to a load in an axial direction which is applied to an object from an outer ring member.SOLUTION: In a planetary roller screw type linear motion mechanism, a friction connecting part 40 in which a carrier 14 is supported by an elastic member 37 so that the carrier 14 relatively moves to a rotating shaft 8 by a reaction force to a rear part in an axial direction which is received by an outer ring member 5, and which friction-contacts with the carrier 14 in a state that the carrier 14 does not relatively move to the rear part in the axial direction with respect to the rotating shaft 8, and releases the friction-connection with the carrier 14 in state that the carrier 14 relatively moves to the rear part in the axial direction with respect to the rotating shaft 8 is arranged at an external periphery of the rotating shaft 8. The friction connecting part 40 is formed into such a shape that the friction connecting part contacts with the carrier 14 at an outside diameter side with respect to a diameter PCD of a circle which passes centers of planetary rollers 13 in common.SELECTED DRAWING: Figure 2

Description

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

  Conventionally, as a brake device for a vehicle, a hydraulic brake device using a hydraulic pressure as a drive source has been often adopted. However, the hydraulic brake device uses a brake oil, and thus has a high environmental load. Also, an ABS, a stability control system is used. It is difficult to further enhance the functions such as brake assist. Therefore, an electric brake device using an electric motor as a drive source has attracted attention as means for realizing further enhancement of the function of the brake device and reduction of environmental load.

  The electric brake device includes a brake disc that rotates integrally with a wheel, a brake pad that is disposed to face the brake disc, and an electric linear actuator that linearly drives the brake pad. The brake pad is used as a brake disc. A braking force is generated by pressing.

  As an electric linear motion actuator used in such an electric brake device, for example, the one described in Patent Document 1 is known. The electric linear actuator of Patent Document 1 includes an electric motor, a rotating shaft to which rotation of the electric motor is input, a plurality of planetary rollers that are in rolling contact with the outer periphery of the rotating shaft, and the plurality of planetary rollers that rotate. The carrier has a carrier that can be revolved in a releasable manner, an outer ring member that is disposed so as to surround the plurality of planetary rollers, and a housing that accommodates the outer ring member so as to be movable in the axial direction. 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 electric linear actuator, when rotation of the electric motor is input to the rotation shaft, the rotation of the rotation shaft is transmitted to the planetary roller that is in rolling contact with the outer periphery of the rotation shaft, and each planetary roller rotates while rotating. Revolve around the axis. 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.

  When this electric linear actuator is used in an electric brake device, if the lead angle of the spiral protrusion on the inner periphery of the outer ring member is set large, the moving speed in the axial direction of the outer ring member becomes faster. The time it takes for the brake pad to come into contact with the brake disc is shortened and the response of the brake can be improved. However, since the load conversion rate is small, the force with which the brake pad presses the brake disc is small. There is a problem of becoming.

  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 achieve both of improving the response of the brake and increasing 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.

  In this way, in a state in which no load is applied forward in the axial direction from the outer ring member to the object, the friction coupling portion on the outer periphery of the rotation shaft frictionally couples with the carrier, and the relative rotation between the carrier and the rotation shaft is limited. The Therefore, when rotation is input from the outside to the rotating shaft, the carrier revolves integrally with the rotating shaft, and the outer ring member moves in the axial direction with a small reduction ratio. On the other hand, in a state where an axially forward load is applied to the object from the outer ring member, the frictional coupling between the friction coupling portion on the outer periphery of the rotation shaft and the carrier is released, and relative rotation between the carrier and the rotation shaft is allowed. Therefore, when rotation is input from the outside to the rotation shaft, the planetary roller revolves while rotating, and the outer ring member moves in the axial direction with a large reduction ratio. In this way, the load conversion rate (reduction ratio) can be switched according to the axial load applied to the object from the outer ring member.

Japanese Patent No. 5496836

  In Patent Document 1, a taper surface formed on the outer periphery of the rotating shaft so as to face the inner periphery of the carrier is employed as a friction coupling portion that frictionally couples with the carrier. The contact radius is small, and it is difficult to increase the torque that can be transmitted by frictional coupling.

  That is, when the rotating shaft suddenly accelerates or decelerates in a state where the inner tapered surface of the carrier is electrically coupled to the outer tapered surface of the rotating shaft, slip may occur between the rotating shaft and the carrier. . As a method for preventing this slipping, it is conceivable to set the magnitude of the preload acting on the carrier from the elastic member. However, if the preload is increased, it is difficult to assemble the planetary roller screw type linear motion mechanism. There's a problem.

  The problem to be solved by the present invention is to improve the reliability of the operation of the planetary roller screw type linear motion mechanism capable of switching the load conversion rate in accordance with the axial load applied to the object from the outer ring member. .

In order to solve the above problems, the present invention provides a planetary roller screw type linear motion mechanism having the following configuration.
A rotation axis to which rotation is input from the outside,
A plurality of planetary rollers in rolling contact with the outer periphery of the rotating shaft;
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 that is provided on the outer periphery of each planetary roller and engages with the spiral ridge so as to move the outer ring member in the axial direction when the planetary roller revolves while rotating. ,
The carrier is elastic so that the carrier moves relative to the rotation shaft in the axial rearward direction by a 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. Supported by members,
In a state where the carrier does not move relative to the rotating shaft in the axial direction rearward, the carrier and the carrier are frictionally coupled so as to limit relative rotation of the carrier and the rotating shaft, and the carrier moves relative to the rotating shaft. And a planetary roller provided with a friction coupling portion on the outer periphery of the rotating shaft to release the frictional coupling between the carrier and the carrier so as to allow relative rotation between the carrier and the rotating shaft in a state where the carrier is relatively moved rearward in the axial direction. In screw type linear motion mechanism,
The friction coupling portion is configured to come into contact with the carrier on the outer diameter side of the diameter of a circle that passes through the centers of the plurality of planetary rollers in common with the rotation axis when frictionally coupled with the carrier. ing.

  In this way, when the frictional coupling portion frictionally couples with the carrier, the frictional coupling portion and the carrier on the outer diameter side than the diameter of a circle that passes through the centers of the plurality of planetary rollers around the rotation axis in common. Since contact is made, the contact radius between the frictional coupling portion and the carrier is increased, and the torque that can be transmitted by the frictional coupling between the frictional coupling portion and the carrier is increased. Therefore, even when the rotating shaft suddenly accelerates or decelerates, slippage between the rotating shaft and the carrier can be prevented, and the operation reliability can be improved.

As the carrier, a plurality of support pins that respectively support the planetary rollers so as to rotate, an axial front disk that holds front end portions in the axial direction of the plurality of support pins, and an axial rear end portion of the plurality of support pins. When adopting one that has an axial rear disk to hold,
It is preferable that the frictional coupling portion employs a member separate from the rotating shaft attached to the outer periphery of the rotating shaft so as to face the axially front disk in the axial direction.

  In this way, since the rotating shaft and the friction coupling portion are manufactured as separate members, the processing of the rotating shaft is facilitated, and the friction coupling portion is also easily processed. Can be reduced.

  The friction coupling portion is not in contact with the carrier in the entire region on the inner diameter side of the diameter of a circle that passes through the centers of the planetary rollers when the carrier contacts the friction coupling portion. Preferably formed.

  In this way, it is possible to secure a contact pressure on the outer diameter side of the diameter of a circle that passes through the centers of the planetary rollers in common, so that the slip between the rotating shaft and the carrier can be more effectively performed. It becomes possible to prevent.

  As the contact surface of the friction coupling portion with respect to the carrier, a tapered surface having a diameter larger than the diameter of a circle passing through the centers of the plurality of planetary rollers in common with the rotation axis as a center can be employed.

  If it does in this way, since the contact surface pressure between a friction coupling part and a carrier becomes high by the wedge effect | action of a taper surface, it becomes possible to prevent more effectively the slip between a rotating shaft and a carrier.

  According to the planetary roller screw type linear motion mechanism of the present invention, when the frictional coupling portion frictionally couples with the carrier, the frictional coupling portion has a diameter of a circle that passes through the centers of the plurality of planetary rollers in common around the rotation axis. Since the contact with the carrier is on the outer diameter side, the contact radius between the frictional coupling portion and the carrier is large, and the torque that can be transmitted by the frictional coupling between the frictional coupling portion and the carrier is large. Therefore, even when the rotating shaft suddenly accelerates or decelerates, slip between the rotating shaft and the carrier is prevented, and the operation reliability is high.

Sectional drawing which shows the electrically driven linear motion actuator incorporating the planetary roller screw-type linear motion mechanism of 1st 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 friction coupling portion Sectional view along line VV in FIG. The figure which shows the state which the load to an axial back is not applied to the carrier shown in FIG. 2, and the carrier and the friction coupling part were friction-coupled. The figure which shows the state by which the load to an axial back was applied to the carrier shown in FIG. 2, and the frictional coupling of a carrier and a frictional coupling part was cancelled | released The expanded sectional view of the vicinity of the frictional coupling part of the planetary roller screw type linear motion mechanism of 2nd Embodiment of this invention 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 9 from the inner side

  FIG. 1 shows an electric linear actuator 2 using a planetary roller screw linear motion mechanism 1 according to a first 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 direction front, the outer ring When the outer ring member 5 moves to the side where the protruding length of the member 5 from the housing 15 becomes smaller, the moving direction of the outer ring member 5 is rearward in the axial direction, the direction of circling around the rotating shaft 8 is the circumferential direction, and the rotating shaft 8 The direction in which the distance changes is defined as the radial 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 20 that holds an axial front end of each support pin 18. The axial rear disk 21 holding the axial rear end of each support pin 18 and the axial front disk 20 and the axial rear disk 21 passing between the plurality of planetary rollers 13 adjacent in the circumferential direction. It has the pillar part 22 to connect. The column portion 22 integrates both the disks 20 and 21 so that the axial front disk 20 and the axial rear disk 21 do not move relative to either the axial direction or the circumferential direction.

  As shown in FIG. 2, the axial front disk 20 and the axial rear disk 21 are each formed in an annular shape that penetrates the rotary shaft 8. Sliding bearings 23 and 24 that are in sliding contact with the outer periphery of the rotating shaft 8 are mounted on the inner periphery of the axial front disc 20 and the inner periphery of the axial rear disc 21, respectively.

  Between the inner periphery of each planetary roller 13 and the outer periphery of the support pin 18, the radial bearing 25 which supports the planetary roller 13 so that rotation is possible is integrated. A thrust bearing 26 is incorporated between each planetary roller 13 and the axial rear disk 21 to support the planetary roller 13 in the axial direction in a rotatable state. An alignment seat 27 is incorporated between the thrust bearing 26 and the axial rear disk 21 so as to tiltably support the planetary roller 13 via the thrust bearing 26.

  The outer ring member 5 is supported by an inner surface of a receiving hole 28 formed in the housing 15 so as to be slidable in the axial direction. Inside the housing 15, a bearing support member 29 is fixed at a position away from the carrier 14 in the axial direction rearward. The bearing support member 29 is formed in an annular shape that penetrates the rotating shaft 8. A radial bearing 30 that rotatably supports the rotary shaft 8 is incorporated in the inner periphery of the bearing support member 29. As the radial bearing 30, for example, a sintered slide bearing or a deep groove ball bearing can be adopted.

  The bearing support member 29 is restricted from moving rearward in the axial direction by a protrusion 31 provided on the inner periphery of the accommodation hole 28, and is moved forward in the axial direction by a retaining ring 32 attached to the inner periphery of the accommodation hole 28. It is regulated. Further, relative rotation of the rotating shaft 8 in the axial direction relative to the bearing support member 29 is restricted by a retaining ring 33 attached to the outer periphery of the rotating shaft 8. Further, relative movement of the carrier 14 in the axial direction relative to the rotating shaft 8 is restricted by a retaining ring 34 attached to the outer periphery of the axially front end portion of the rotating shaft 8.

  Here, the radial bearing 30 is incorporated in a state where relative movement in the axial direction relative to the bearing support member 29 is restricted, and the retaining ring 33 is attached to the radial bearing 30 on the rear side in the axial direction. Further, the retaining ring 34 is attached to the front side in the axial direction with respect to the sliding bearing 23 on the inner periphery of the front disc 20 in the axial direction.

  A thrust bearing 35 is incorporated between the carrier 14 and the bearing support member 29 to support the carrier 14 from the rear side in the axial direction in a state where the carrier 14 can revolve. A spacer 36 for transmitting an axial load from the carrier 14 to the thrust bearing 35 is incorporated between the carrier 14 and the thrust bearing 35. An elastic member 37 is incorporated between the carrier 14 and the spacer 36, and an axial gap 38 that allows the carrier 14 to move in the axial direction is provided between the spacer 36 and the carrier 14. As a result, when an axially rearward load is applied to the carrier 14, the elastic member 37 is compressed in the axial direction by the load, and the carrier is within the range of the axial gap 38 between the carrier 14 and the spacer 36. 14 moves relative to the rotary shaft 8 in the axially rearward direction. Here, the size of the axial gap 38 between the carrier 14 and the spacer 36 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 37 is formed in an annular shape that allows the rotation shaft 8 to pass therethrough. The elastic member 37 is, for example, a disc spring. A wave spring or a coil spring can be employed instead of the disc spring. When the outer ring member 5 does not apply a load forward in the axial direction to the object (that is, when no reaction force in the axially rearward direction is acting on the carrier 14), the elastic member 37 is previously axially moved. It is in a compressed state, and is built in so that a pre-pressure acts on the carrier 14 from the elastic member 37.

  In this embodiment, the elastic member 37 is incorporated between the carrier 14 and the spacer 36. However, the position where the elastic member 37 is incorporated may be any other position as long as it is between the carrier 14 and the bearing support member 29. An elastic member 37 may be incorporated between the seat 36 and the thrust bearing 35, or the spacer 36 may be composed of two divided bodies that can move relative to each other in the axial direction, and the elastic member 37 may be incorporated between the two divided bodies. Alternatively, an elastic member 37 may be incorporated between the thrust bearing 35 and the bearing support member 29.

  On the outer periphery of the rotating shaft 8, a friction coupling portion 40 that is axially opposed to the axial front disk 20 is attached. The friction coupling portion 40 is a disk-like member formed separately from the rotary shaft 8, and is fitted and attached to the outer periphery of the rotary shaft 8.

  As shown in FIG. 4, between the fitting surfaces of the friction coupling portion 40 and the rotating shaft 8, a rotation preventing portion 41 that prevents the friction coupling portion 40 from rotating with respect to the rotating shaft 8 is provided. The anti-rotation portion 41 is, for example, a portion having a shape in which a part of the circumference is a plane parallel to the axis of the rotation shaft 8 (see FIG. 5). Further, the friction coupling portion 40 is restricted from moving forward in the axial direction with respect to the rotary shaft 8 by a retaining ring 34 on the outer periphery of the rotary shaft 8.

  The friction coupling portion 40 has an outer diameter larger than a diameter PCD of a circle that passes through the centers of the plurality of planetary rollers 13 in common (hereinafter simply referred to as “PCD of the planetary rollers 13”), and the carrier 14 is frictionally coupled. When it comes into contact with the portion 40, it comes into contact with the carrier 14 on the outer diameter side with respect to the PCD of the planetary roller 13 around the rotation shaft 8. The contact surface of the friction coupling portion 40 with respect to the carrier 14 is a plane perpendicular to the axial direction.

  A concave portion 42 having a circular diameter centered on the rotation shaft 8 is formed on the surface of the friction coupling portion 40 facing the front disk 20 in the axial direction. The diameter of the recess 42 is larger than the PCD of the planetary roller 13. As a result, when the carrier 14 comes into contact with the friction coupling portion 40, the friction coupling portion 40 is not in contact with the carrier 14 in the entire area on the inner diameter side of the PCD of the planetary roller 13.

  Here, as shown in FIG. 6, 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 load on the rearward in the axial direction is not applied to the carrier 14), The friction coupling portion 40 is in contact with a portion on the outer diameter side of the planet roller 13 of the carrier 14 relative to the PCD. At this time, the frictional coupling part 40 and the carrier 14 are frictionally coupled by the force of the elastic member 37, and the relative rotation of the carrier 14 and the rotating shaft 8 is limited by the frictional force between the contact surfaces of the frictional coupling part 40 and the carrier 14. It becomes a state.

  On the other hand, as shown in FIG. 7, the carrier 14 is moved in the axially rearward direction relative to the rotating shaft 8 (that is, the carrier 14 is loaded with the axially rearward load, and the elastic member 37 is compressed by the load. In the state in which the amount is increased), the front disk 20 in the axial direction of the carrier 14 is separated from the friction coupling portion 40. At this time, the frictional coupling between the frictional coupling portion 40 and the carrier 14 is released, and the relative rotation between the carrier 14 and the rotating shaft 8 is allowed.

  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 a state in which the outer ring member 5 shown in FIG. 2 does not apply a load in the axial direction forward to the object (that is, a state in which a reaction force in the axially rearward direction does not act on the carrier 14), FIG. As shown in FIG. 4, the carrier 14 and the friction coupling portion 40 are frictionally coupled, and the relative rotation between the carrier 14 and the rotary shaft 8 is limited. 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 where an axially forward load is applied to the object from the outer ring member 5, the axially rearward reaction force received by the outer ring member 5 passes through the planetary roller 13 and the thrust bearing 26 in order. The carrier 14 moves relative to the rotary shaft 8 in the axial direction rearward due to the reaction force in the axially rearward direction, and the frictional coupling between the carrier 14 and the frictional coupling portion 40 is released as shown in FIG. Thus, 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.

  9 and 10 show an electric brake device using the electric linear actuator 2 having the above 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 disposed opposite to both sides in the axial direction of the brake disc 50, and an inner side And an electric linear actuator 2 that drives the brake pad 53 linearly. 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. 6, the carrier 14 is frictionally coupled to the friction coupling portion 40, so that the outer ring member 5 shown in FIG. Move in the axial direction with a relatively fast 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 is moved relative to the rotary shaft 8 as shown in FIG. Since the frictional coupling between the carrier 14 and the friction coupling portion 40 is released relative to the rear in the axial direction, the moving speed in the axial direction of the outer ring member 5 shown in FIG. An 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 inner brake pad 53 presses the brake disc 50. It becomes possible.

  As described above, in the planetary roller screw type linear motion mechanism 1, the friction coupling portion 40 on the outer periphery of the rotating shaft 8 is connected to the carrier 14 in a state in which no load is applied to the object from the outer ring member 5 in the axial direction. Since the frictional coupling is performed and the relative rotation between the carrier 14 and the rotary shaft 8 is restricted, 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 friction coupling between the friction coupling portion 40 on the outer periphery of the rotating shaft 8 and the carrier 14 is released, and the relative relationship between the carrier 14 and the rotating shaft 8 is released. Since the rotation is allowed, the moving speed of the outer ring member 5 in the axial direction becomes slow, and the load conversion rate becomes large. 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, as shown in FIG. 4, the planetary roller screw type linear motion mechanism 1 is configured such that when the frictional coupling portion 40 is frictionally coupled to the carrier 14, the frictional coupling portion 40 is centered on the rotation shaft 8 and the PCD of the planetary roller 13 is connected. Since the contact is made with the carrier 14 on the outer diameter side, the contact radius between the friction coupling part 40 and the carrier 14 is large, and the torque that can be transmitted by the frictional coupling between the friction coupling part 40 and the carrier 14 is large. Therefore, even when the rotating shaft 8 suddenly accelerates or decelerates, slip between the rotating shaft 8 and the carrier 14 is prevented, and the operation reliability is high.

  Further, in this planetary roller screw type linear motion mechanism 1, since the rotary shaft 8 and the friction coupling portion 40 are manufactured as separate members, the machining of the rotary shaft 8 is easy and the friction coupling portion 40 is also made. As a result, the manufacturing cost as a whole is reduced.

  The planetary roller screw type linear motion mechanism 1 is frictionally coupled so that the carrier 14 is not in contact with the carrier 14 in the entire region on the inner diameter side of the planetary roller 13 when the carrier 14 comes into contact with the friction coupling portion 40. Since the portion 40 is formed, the contact pressure on the outer diameter side of the PCD of the planetary roller 13 can be secured, and the slip between the rotating shaft 8 and the carrier 14 can be effectively prevented. It is.

  FIG. 8 shows a second embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  On the outer periphery of the rotating shaft 8, a friction coupling portion 40 that is axially opposed to the axial front disk 20 is attached. The friction coupling portion 40 is a disk-like member formed separately from the rotary shaft 8, and is fitted and attached to the outer periphery of the rotary shaft 8.

  The friction coupling portion 40 includes a disc portion 61 having an outer diameter larger than the PCD of the planetary roller 13 and a cylindrical portion 62 extending axially rearward from the radial outer end of the disc portion 61. A tapered surface 63 is formed on the inner periphery of the cylindrical portion 62 so as to face the outer periphery of the axial front disk 20. The tapered surface 63 is a tapered inner peripheral surface whose inner diameter decreases from the axial rear side toward the front side. The inclination angle of the tapered surface 63 (the angle formed by the tapered surface 63 with respect to the direction parallel to the axial direction) is set in the range of 5 to 20 °.

  On the outer periphery of the front disk 20 in the axial direction of the carrier 14, a tapered outer peripheral surface 64 is formed so as to face the tapered surface 63 of the friction coupling portion 40. The inclination angle of the taper outer peripheral surface 64 (the angle formed by the taper outer peripheral surface 64 with respect to the direction parallel to the axial direction) is set in the range of 5 to 20 °. The tapered outer peripheral surface 64 is preferably formed to have an inclination angle equal to that of the tapered surface 63.

  The minimum diameter of the tapered surface 63 on the inner periphery of the cylindrical portion 62 of the friction coupling portion 40 is smaller than the minimum diameter of the tapered outer peripheral surface 64 of the carrier 14. As a result, when the carrier 14 comes into contact with the friction coupling portion 40, the friction coupling portion 40 is not in contact with the carrier 14 in the entire area on the inner diameter side of the PCD of the planetary roller 13.

  As shown in FIG. 8, the planetary roller screw type linear motion mechanism 1 according to the second embodiment is configured such that when the friction coupling portion 40 is frictionally coupled with the carrier 14, the friction coupling portion 40 is centered on the rotation shaft 8. 13 is in contact with the carrier 14 on the outer diameter side of the PCD 13, the contact radius between the friction coupling portion 40 and the carrier 14 is large, and the torque that can be transmitted by the frictional coupling between the friction coupling portion 40 and the carrier 14 is large. Therefore, even when the rotating shaft 8 suddenly accelerates or decelerates, slip between the rotating shaft 8 and the carrier 14 is prevented, and the operation reliability is high.

  Further, since the contact surface of the friction coupling portion 40 with respect to the carrier 14 is a tapered surface 63 having a diameter larger than that of the PCD of the planetary roller 13 around the rotation shaft 8, the friction coupling portion 40 is caused by the wedge action of the tapered surface 63. The contact surface pressure between the rotating shaft 8 and the carrier 14 is increased, and the slip between the rotating shaft 8 and the carrier 14 can be prevented more effectively.

  In addition, since the planetary roller screw type linear motion mechanism 1 is manufactured by using the rotary shaft 8 and the friction coupling portion 40 as separate members as in the first embodiment, the rotary shaft 8 can be easily processed. In addition, the friction coupling portion 40 can be easily processed. As a result, the manufacturing cost as a whole is reduced.

  The planetary roller screw type linear motion mechanism 1 is frictionally coupled so that the carrier 14 is not in contact with the carrier 14 in the entire region on the inner diameter side of the planetary roller 13 when the carrier 14 comes into contact with the friction coupling portion 40. Since the portion 40 is formed, the contact pressure on the outer diameter side of the PCD of the planetary roller 13 can be secured, and the slip between the rotating shaft 8 and the carrier 14 can be effectively prevented. It is.

  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 13 Planetary roller 14 Carrier 16 Spiral protrusion 17 Circumferential groove 18 Support pin 20 Axial front disk 21 Axial rear disk 37 Elastic member 40 Friction coupling 50 brake disc 53 Inner brake pad PCD Diameter

Claims (5)

A rotating shaft (8) to which rotation is input from the outside;
A plurality of planetary rollers (13) in rolling contact with the outer periphery of the rotating shaft (8);
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);
It is provided on the outer periphery of each planetary roller (13), and when the planetary roller (13) revolves while rotating, it engages with the spiral ridge (16) so as to move the outer ring member (5) in the axial direction. A helical groove or a circumferential groove (17),
The carrier (14) moves rearward in the axial direction with respect to the rotating shaft (8) by the reaction force in the rearward direction in the axial direction when the outer ring member (5) applies a load forward in the axial direction to the object. The carrier (14) is supported by the elastic member (37) so as to be relatively moved,
In a state where the carrier (14) is not relatively moved rearward in the axial direction with respect to the rotating shaft (8), the carrier (14) and the rotating shaft (8) are limited so as to limit relative rotation of the carrier (14). 14) and in a state where the carrier (14) is relatively moved axially rearward with respect to the rotation shaft (8), relative rotation between the carrier (14) and the rotation shaft (8) is allowed. In the planetary roller screw type linear motion mechanism in which the frictional coupling portion (40) for releasing the frictional coupling with the carrier (14) is provided on the outer periphery of the rotating shaft (8) as follows:
The frictional coupling part (40) has a diameter of a circle (PCD) that passes through the centers of the plurality of planetary rollers (13) in common with the rotating shaft (8) when frictionally coupled with the carrier (14). The planetary roller screw type linear motion mechanism is characterized in that the outer diameter side is in contact with the carrier (14). The carrier (14) includes a plurality of support pins (18) that rotatably support the planetary rollers (13), and an axial front disk (10) that holds the front end in the axial direction of the plurality of support pins (18). 20) and an axial rear disk (21) for holding the axial rear ends of the plurality of support pins (18),
The friction coupling portion (40) is a separate member from the rotating shaft (8) attached to the outer periphery of the rotating shaft (8) so as to face the axial front disc (20) in the axial direction. Item 4. The planetary roller screw type linear motion mechanism according to Item 1.   When the carrier (14) contacts the friction coupling part (40), the friction coupling part (40) is larger than the diameter (PCD) of a circle that passes through the centers of the planetary rollers (13) in common. The planetary roller screw type linear motion mechanism according to claim 1 or 2, wherein the planetary roller screw type linear motion mechanism is formed so as to be in non-contact with the carrier (14) in the entire region on the inner diameter side.   From the diameter (PCD) of a circle in which the contact surface of the friction coupling portion (40) with respect to the carrier (14) passes through the centers of the plurality of planetary rollers (13) around the rotating shaft (8). The planetary roller screw type linear motion mechanism according to any one of claims 1 to 3, wherein the tapered surface (63) has a large diameter. The planetary roller screw type linear motion mechanism (1) according to any one of claims 1 to 4,
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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