JP6758937B2 - Planetary roller screw type linear motion mechanism and electric braking device - Google Patents

Description

The present invention relates to a planetary roller screw type linear motion mechanism used in 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 a rotary motion input from the outside into a linear motion and outputs it, 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 can rotate a rotating shaft to which rotation is input from the outside, a plurality of planetary rollers that roll and contact the cylindrical surface on the outer periphery of the rotating shaft, and the plurality of planetary rollers. It also has a carrier that revolves around the carrier and an outer ring member that is arranged so as to surround the plurality of planetary rollers. A spiral ridge is provided on the inner circumference of the outer ring member, and a spiral groove or a circumferential groove that engages with the spiral ridge is provided on the outer circumference of each planet roller.

In this planetary roller screw type linear motion mechanism, when rotation is input to the rotating shaft from the outside, the rotation of the rotating shaft is transmitted to the planetary rollers that roll and contact the outer circumference of the rotating shaft, and each planetary roller rotates while rotating. Revolve around the axis of rotation. At this time, the outer ring member moves in the axial direction due to the engagement between the spiral groove or the circumferential groove on the outer circumference of the planetary roller and the spiral ridge on the inner circumference of the outer ring member. In this way, the planetary roller screw type linear motion mechanism converts the rotation of the rotating shaft into the linear motion of the outer ring member.

This planetary roller screw type linear motion mechanism can be used for an electric braking device. In this case, when the brake is applied, the rotation of the electric motor is converted into the 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 the brake is released, the electric motor is rotated in the opposite direction to provide a clearance between the brake pad and the brake disc.

Here, if the lead angle of the spiral ridge on the inner circumference of the outer ring member is set large, the moving speed of the outer ring member in the axial direction becomes faster, so that it takes time for the brake pad to come into contact with the brake disc when applying the brake. The time is shortened and the responsiveness of the brake can be improved, but on the other hand, the load conversion rate is reduced, so that 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 ridge on the inner circumference of the outer ring member is set small, the load conversion rate becomes large, so that the force with which the brake pad presses the brake disc when applying the brake can be increased. However, on the other hand, since the moving speed of the outer ring member in the axial direction becomes slow, the time required for the brake pad to come into contact with the brake disc becomes long, and the responsiveness of the brake deteriorates. That is, increasing the responsiveness of the brake and increasing the force with which the brake pad presses the brake disc are in a contradictory relationship.

Therefore, in Patent Document 1, in order to improve the responsiveness of the brake and to increase the force with which the brake pad presses the brake disc, a load is applied according to the axial load applied from the outer ring member to the object. We are proposing a structure that switches the 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 direction due to the reaction force in the axial direction received when the outer ring member applies a load in the axial direction forward to the object. I support it. Further, in a state where the carrier is not relatively moving backward in the axial direction with respect to the rotation axis, frictional coupling with the carrier is performed so as to limit the relative rotation between the carrier and the rotation axis, and the carrier is axially rearward with respect to the rotation axis. In the state of relative movement, a frictional coupling portion for releasing the frictional coupling between the carrier and the rotating shaft is provided on the outer periphery of the rotating shaft so as to allow the relative rotation of the carrier and the rotating shaft. Here, the friction stir welding portion is a tapered surface provided on the outer periphery of the axial front end portion of the rotating shaft so that the diameter gradually increases toward the front in the axial direction from the cylindrical surface on which the planetary roller rolls and contacts.

Japanese Patent No. 54986836

In the above-mentioned planetary roller screw type linear motion mechanism, the inventor of the present application determines that the shape of the rotating shaft is finished when the cylindrical surface on the outer periphery of the rotating shaft is finished with high precision by polishing or the like. I noticed that it has a difficult shape.

That is, in the planetary roller screw type linear motion mechanism of Patent Document 1, a tapered surface whose diameter gradually increases from the cylindrical surface on which the planetary roller rolls and contacts toward the front in the axial direction is provided. The tapered surface is a portion having an outer diameter larger than the cylindrical surface on which the planetary rollers roll and contact. Therefore, it is not possible to adopt a low-cost processing method (for example, centerless through polishing) that processes the outer circumference of the rotating shaft while rolling and supporting the outer circumference of the rotating shaft, and the cylindrical surface on which the planetary rollers roll and contact can be made highly accurate. There is 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 cylindrical surface on which the planetary rollers on the outer periphery of the rotating shaft roll and contact. It is to provide a planetary roller screw type linear motion mechanism which 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 with a cylindrical surface on the outer circumference,
A plurality of planetary rollers that roll and contact the cylindrical surface,
A carrier that holds the multiple planetary rollers so that they can rotate and revolve,
An outer ring member arranged so as to surround the plurality of planetary rollers and supported so as to be movable in the axial direction,
The spiral ridges provided on the inner circumference of the outer ring member and
It has a spiral groove or a circumferential groove provided on the outer periphery of each planetary roller so as to engage with the spiral ridge.
In a planetary roller screw type linear motion mechanism in which the outer ring member moves in the axial direction by engaging the spiral ridge with the spiral groove or circumferential groove.
The carrier moves relative to the other in the axial direction with respect to the rotation axis due to a reaction force to the other in the axial direction received when a load in one of the axial directions is applied to the outer ring member. With elastic members that support
When the carrier is provided on the outer periphery of the rotating shaft and the carrier does not move relative to the other in the axial direction with respect to the rotating shaft, frictional coupling with the carrier so as to limit the relative rotation between the carrier and the rotating shaft. Then, when the carrier moves relative to the other in the axial direction with respect to the rotation axis, the frictional coupling portion that releases the frictional coupling between the carrier and the carrier so as to allow the relative rotation of the carrier and the rotation axis. With
The planetary roller screw type linear motion mechanism, characterized in that the friction coupling portion is arranged on the other side in the axial direction with respect to the planetary roller.

In this way, when no load is applied from the outer ring member to the object, the frictional coupling portion on the outer circumference of the rotating shaft is frictionally welded to the carrier, and the relative rotation between the carrier and the rotating shaft is restricted. Therefore, when rotation is input to the rotation shaft from the outside, the carrier revolves integrally with the rotation shaft, and the planetary roller revolves around the rotation shaft without rotating. At this time, the revolution speed of the planetary roller is relatively high. Therefore, the moving speed of the outer ring member in the axial direction becomes high, and the load conversion rate becomes small. On the other hand, when a load is applied to the object from the outer ring member, the frictional coupling between the frictional coupling portion on the outer periphery of the rotating shaft and the carrier is released, and the relative rotation between the carrier and the rotating shaft is allowed. Therefore, when rotation is input to the rotation axis from the outside, the planet roller revolves around the rotation axis 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 becomes large. In this way, the load conversion rate can be switched according to the axial load applied to the object from the outer ring member.

Further, the frictional coupling portion on the outer periphery of the rotating shaft usually has a shape having a portion having a smaller diameter from one axial direction (front in the axial direction) to the other in the axial direction (rear in the axial direction). Since it is arranged in the other axial direction with respect to the planetary roller (the axial direction opposite to the direction in which the load is applied from the outer ring member to the object, that is, the axial rearward), the cylindrical surface on which the planetary roller rolls and contacts. Can be the maximum diameter portion of the rotating shaft. Therefore, it is possible to adopt a low-cost processing method (for example, centerless through polishing) in which the outer circumference of the rotating shaft is machined while rolling and supporting the outer circumference of the rotating shaft, and the cylindrical surface on which the planetary rollers roll and contact is polished. Can be easily finished by.

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

In this way, when the carrier and the frictional coupling portion on the outer periphery of the rotating shaft are frictionally welded, it is possible to generate a large frictional force due to the wedge action of the tapered surface.

Further, in the present invention, as an electric brake device using the above-mentioned planetary roller screw type linear motion mechanism, the one having the following configuration is also provided.
Planetary roller screw type linear motion mechanism with the above configuration and
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,
Brake discs placed facing the brake pads and
Electric braking device with.

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 stir welding portion on the outer circumference of the rotating shaft is arranged on the other side in the axial direction with respect to the planetary roller, the cylindrical surface on which the planetary roller rolls and contacts can be the maximum diameter portion of the rotating shaft. is there. Therefore, it is possible to adopt a low-cost processing method (for example, centerless through polishing) in which the outer circumference of the rotating shaft is machined while rolling and supporting the outer circumference of the rotating shaft, and the cylindrical surface on which the planetary rollers roll and contact is polished. Can be easily finished by.

Sectional drawing which shows the electric linear motion actuator which incorporated the planet roller screw type linear motion mechanism of embodiment of this invention. Enlarged sectional view of the vicinity of the planetary roller screw type linear motion mechanism of FIG. Sectional view taken along line III-III of FIG. Enlarged cross-sectional view of the vicinity of the elastic member of FIG. The figure which shows the state which the reaction force in the axial direction is applied to the carrier of FIG. A cross-sectional view showing an example of an electric brake device using the electric linear actuator shown in FIG. A view of the electric brake device shown in FIG. 6 as viewed from the inner side.

FIG. 1 shows an electric linear actuator 2 using the planetary roller screw type linear motion mechanism 1 according to the embodiment of the present invention. The electric linear actuator 2 uses an electric motor 3, a reduction gear train 4 that decelerates and transmits the rotation of the electric motor 3, and an outer ring member 5 that transmits rotation input from the electric motor 3 via the reduction gear train 4. It has a planetary roller screw type linear motion mechanism 1 that converts and outputs the linear motion of the above.

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 rotating shaft 8 of the planetary roller screw type linear motion mechanism 1, and an input gear 7 and an output gear 9. It has an intermediate gear 10 for transmitting rotation between the gears 10 and a gear case 11 for accommodating these gears 7, 9, and 10. The reduction gear train 4 reduces the rotation input from the motor shaft 6 of the electric motor 3 to the input gear 7 by sequentially transmitting the input gear 7, the intermediate gear 10, and the output gear 9 having different numbers of teeth. The reduced rotation is output from the output gear 9 to the rotating shaft 8.

As shown in FIGS. 2 and 3, the planet roller screw type linear motion mechanism 1 includes a rotating shaft 8 having a cylindrical surface 12 on the outer circumference, a plurality of planet rollers 13 that roll and contact the cylindrical surface 12, and a plurality of planets thereof. A carrier 14 that holds the rollers 13 so that they can rotate and revolve, a hollow cylindrical outer ring member 5 that is arranged so as to surround the plurality of planetary rollers 13, and a housing 15 that houses the outer ring members 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 rotating shaft 8 is the axial direction, and the moving direction of the outer ring member 5 when the outer ring member 5 moves to the side where the protrusion length of the outer ring member 5 from the housing 15 becomes larger is axially forward (one side). ), The moving direction of the outer ring member 5 when the outer ring member 5 moves to the side where the protrusion length from the housing 15 of the outer ring member 5 becomes smaller is axially rearward (the other), and the direction of orbiting around the rotating shaft 8 is rotated. Defined as direction.

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

As shown in FIGS. 2 and 3, the carrier 14 includes a plurality of support pins 18 that support each planet roller 13 so as to be rotatable, and an axial front disk 19 that holds an axial front end portion of each support pin 18. The axial front disk 19 and the axial rear disk 20 pass between the axial rear disk 20 holding the axial rear end of each support pin 18 and the plurality of planetary rollers 13 adjacent to each other in the circumferential direction. It has a pillar portion 21 to be connected. The pillar portion 21 integrates both the discs 19 and 20 so that the axial front disc 19 and the axial rear disc 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 disc 19 and the axial rear disc 20 are each formed in an annular shape so as to penetrate the rotating shaft 8. A slide bearing 22 that is in sliding contact with the outer periphery of the rotating shaft 8 is mounted on the inner circumference of the axial front disc 19.

A radial bearing 23 that supports the planet roller 13 so as to rotate is incorporated between the inner circumference of each planet roller 13 and the outer circumference of the support pin 18. A thrust bearing 24 that supports the planet roller 13 in the axial direction in a state in which the planet roller 13 can rotate is incorporated between each planet roller 13 and the axial rear disc 20. Further, a centering seat 25 that tiltably supports the planetary roller 13 via the thrust bearing 24 is incorporated between the thrust bearing 24 and the axial rear disc 20.

The outer ring member 5 is supported so as to be slidable in the axial direction on the inner surface of the accommodating hole 26 formed in the housing 15. Inside the housing 15, the bearing support member 27 is fixed at a position axially rearward from the outer ring member 5. The bearing support member 27 is formed in an annular shape that penetrates the rotating shaft 8. A radial bearing 28 that rotatably supports the rotating shaft 8 is incorporated in the inner circumference of the bearing support member 27. As the radial bearing 28, for example, a sintered plain bearing or a deep groove ball bearing can be adopted.

The bearing support member 27 is restricted from moving backward in the axial direction by a protrusion 29 provided on the inner circumference of the accommodation hole 26, and is moved forward in the axial direction by a retaining ring 30 mounted on the inner circumference of the accommodation hole 26. It is regulated. Further, the rotating shaft 8 is restricted from moving forward in the axial direction with respect to the bearing support member 27 by a retaining ring 31 mounted on the outer periphery of the rotating shaft 8. Further, the carrier 14 is restricted from moving forward in the axial direction with respect to the rotating shaft 8 by a retaining ring 32 mounted on the outer periphery of the axial front end portion of the rotating shaft 8.

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

A thrust bearing 33 that supports the carrier 14 from the rear side in the axial direction in a revolving state is incorporated between the carrier 14 and the bearing support member 27. Further, 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 a load is applied to the carrier 14 in the axial direction, the elastic member 35 is compressed in the axial direction by the load, and the carrier is within the range of the axial gap 36 between the carrier 14 and the spacer 34. 14 is adapted to move relative to the rotating shaft 8 in the axial direction. Here, the size of the axial gap 36 between the carrier 14 and the spacer 34 is very small. Therefore, the distance at which the carrier 14 can move relative to the rotating shaft 8 in the axial direction is extremely short (for example, 0.5 mm or less).

The elastic member 35 is formed in an annular shape that penetrates the rotating shaft 8. The elastic member 35 is, for example, a disc spring. It is also possible to use wave springs or coil springs instead of disc springs. The elastic member 35 is preliminarily compressed in the axial direction in a state where no load is applied rearward in the axial direction to the carrier 14, and the carrier 14 is urged. The elastic member 35 is incorporated so that when a load is applied to the carrier 14 in the axial direction, the amount of compression in the axial direction of the elastic member 35 increases according to the magnitude of the load.

A housing 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 portion 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 position where the elastic member 35 is incorporated may be any other position as long as it is between the carrier 14 and the bearing support member 27. An elastic member 35 may be incorporated between the seat 34 and the thrust bearing 33, or the spacer 34 may be composed of two split bodies that can move relative to each other in the axial direction, and the elastic member 35 may be incorporated between the two split 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 on which the planetary roller 13 rolls and contacts, a tapered surface 38 (friction stir welding portion) located axially rearward with respect to the cylindrical surface 12, and an axially rearward portion of the tapered surface 38. Is provided with a continuous 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 to the rear side in the axial direction. 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 facing the tapered surface 38 on the outer periphery of the rotating shaft 8 is formed on the inner circumference of the axially rear disc 20 of the carrier 14. 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 so as to have an inclination angle equal to that of the tapered surface 38.

Here, as shown in FIG. 4, in a state in which the carrier 14 is not moving rearward in the axial direction with respect to the rotating shaft 8 (that is, in a state in which the carrier 14 is not loaded in the rearward direction in the axial direction). The tapered inner peripheral surface 40 of the carrier 14 is in contact with the tapered surface 38 on the outer periphery 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 will be in a state of being.

On the other hand, as shown in FIG. 5, a state in which the carrier 14 is moved rearward in the axial direction with respect to the rotating shaft 8 (that is, a load is applied to the carrier 14 in the rearward direction in the axial direction, and the load compresses the elastic member 35. In the state where the amount is increased), the tapered inner peripheral surface 40 of the carrier 14 is separated from the tapered surface 38 on the outer periphery of the rotating shaft 8. At this time, the frictional coupling between the tapered inner peripheral surface 40 and the tapered surface 38 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 rotation shaft 8 of the planetary roller screw type linear motion mechanism 1.

Here, in a state where the outer ring member 5 does not load the object in the axially forward direction, the carrier 14 is not loaded in the axially rearward direction. Therefore, as shown in FIG. 4, the carrier 14 is inside the taper. The peripheral surface 40 and the tapered surface 38 on the outer periphery of the rotating shaft 8 are frictionally coupled, and the relative rotation of the carrier 14 and the rotating 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. It revolves around the axis 8. Then, the planetary roller 13 and the outer ring member 5 move relative to each other in the axial direction due to the engagement between the circumferential groove 17 on the outer circumference of the planet roller 13 and the spiral ridge 16 on the inner circumference of the outer ring member 5, but the planet roller 13 Since the movement in the axial direction is restricted 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, the carrier 14 revolves integrally with the rotating shaft 8, and the planet roller 13 revolves around the rotating shaft 8 without rotating. Therefore, the planet 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 becomes high, and the load conversion rate becomes small.

On the other hand, when a load is applied to the object from the outer ring member 5 in the axial direction forward, the reaction force received by the outer ring member 5 in the axial direction is sequentially passed through the planetary roller 13 and the thrust bearing 24 to the carrier 14. The carrier 14 moves rearward in the axial direction with respect to the rotating shaft 8 due to the reaction force transmitted to the rear in the axial direction, and as shown in FIG. 5, the tapered inner peripheral surface 40 of the carrier 14 and the rotating shaft 8 The frictional coupling of the tapered surface 38 on the outer periphery of the carrier 14 is released, and the relative rotation of the carrier 14 and the rotating shaft 8 is allowed. Therefore, when rotation is input to the rotating shaft 8 from the electric motor 3 shown in FIG. 1 via the reduction gear train 4, the planet roller 13 revolves around the rotating shaft 8 while rotating around the support pin 18. .. Then, the planetary roller 13 and the outer ring member 5 move relative to each other in the axial direction due to the engagement between the circumferential groove 17 on the outer circumference of the planet roller 13 and the spiral ridge 16 on the inner circumference of the outer ring member 5, but the planet roller 13 Since the movement in the axial direction is restricted 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 planet roller 13 revolves around the rotating shaft 8 while rotating, the revolution speed of the planet roller 13 is relatively slower than when the planet roller 13 revolves around the rotating shaft 8 without rotating. It becomes a thing. Therefore, 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, in this electric linear acting actuator 2, the load conversion rate is switched according to the axial load applied to the object from the outer ring member 5. By using the electric linear actuator 2 in the electric brake device, it is possible to improve the responsiveness 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 configuration. This electric brake device refers to 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 a mounting bracket 51. A caliper body 52 that is slidably supported in parallel with the axial direction of the brake disc 50, an inner side brake pad 53 and an outer side brake pad 54 that face each other in the axial direction with the brake disc 50 in between, and an inner side brake pad. It has an electric linear motion actuator 2 that moves 53 in the axial direction. A minute clearance 55 is provided between the inner side brake pad 53 and the brake disc 50. The inner side brake pad 53 and the outer side 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, respectively.

The caliper body 52 has 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 integrally formed with the housing 15 of the electric linear actuator 2. The outer shell portion 57 of the caliper body 52 and the housing 15 of the electric linear actuator 2 may be formed as separate bodies, and both may be integrated with bolts or the like. The outer ring member 5 is arranged on the back surface of the inner side brake pad 53 so that the inner side brake pad 53 also moves integrally with the outer ring member 5 when the outer ring member 5 moves.

At the end of the outer ring member 5 on the side of the brake disc 50, an engaging recess 59 that engages with the engaging convex portion 58 formed on the back surface of the inner side brake pad 53 is formed, and the engaging convex portion 58 and the engaging convex portion 58 are formed. The outer ring member 5 is prevented from rotating by the engagement of the engaging recess 59.

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

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

After that, when the inner side brake pad 53 comes into contact with the brake disc 50 and an axial load is applied from the inner side brake pad 53 to the brake disc 50, the carrier 14 acts on the rotating shaft 8 as shown in FIG. Since it moves relative to the rear in the axial direction and the frictional coupling between the carrier 14 and the tapered surface 38 of the rotating shaft 8 is released, the moving speed of the outer ring member 5 shown in FIG. 1 in the axial direction becomes slow and the load conversion rate becomes large. As a result, a large axial load is generated. Therefore, it is possible to increase the force with which the inner side brake pad 53 presses the brake disc 50.

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

As described above, in the planetary roller screw type linear motion mechanism 1 of this embodiment, when a load is not applied to the object from the outer ring member 5 in the axial direction forward, the frictional coupling portion on the outer periphery of the rotating shaft 8 is formed. Since it is frictionally coupled with the carrier 14 and the relative rotation between the carrier 14 and the rotating shaft 8 is restricted, the moving speed of the outer ring member 5 in the axial direction becomes faster and the load conversion rate becomes smaller. On the other hand, when a load is applied to the object from the outer ring member 5 in the axial direction forward, the frictional coupling between the outer peripheral frictional coupling portion 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 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, the planetary roller screw type linear motion mechanism 1 of this embodiment has low cost such as centerless through polishing when finishing the cylindrical surface 12 with which the planetary rollers 13 on the outer circumference of the rotating shaft 8 roll and contact with high accuracy by polishing or the like. It is possible to adopt the processing method of.

That is, for example, the tapered surface 38 in FIG. 2 is arranged axially forward (on the left side in the figure) with respect to the cylindrical surface 12 with which the planetary roller 13 rolls and contacts, and the tapered inner peripheral surface 40 is arranged on the inner circumference of the axial front disk 19. However, in this case, the tapered surface 38 has an outer diameter larger than that of the cylindrical surface 12, so that when the cylindrical surface 12 with which the planetary roller 13 rolls and contacts is finished by polishing or the like. 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 high.

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 rotating shaft 8 is arranged axially rearward with respect to the planetary roller 13 (cylindrical surface 12). Therefore, it is possible to make the cylindrical surface 12 with which the planetary roller 13 rolls into contact as the maximum diameter portion of the rotating shaft 8. Therefore, it is possible to adopt a low-cost processing method (processing of polishing while rolling and supporting the outer circumference of the rotating shaft 8, 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 adjusting wheel that rotates at a position facing the grinding wheel with a work piece in between, and the grinding wheel and the adjusting wheel are used for processing. This is a processing method in which the outer circumference of the workpiece is continuously polished while the object is fed in the axial direction.

As the friction stir welding portion, for example, an axially orthogonal plane connecting between the cylindrical surface 12 and the cylindrical surface 39 can be adopted, but if the tapered surface 38 is adopted as the friction stir welding portion as in the above embodiment, the carrier When frictionally welded to 14, a large frictional force can be generated by the wedge action of the tapered surface 38.

In the present embodiment, the rotating shaft 8 and the carrier 14 are frictionally coupled, but a member that rotates integrally with the carrier 14 and the rotating shaft 8 may be frictionally welded. For example, an 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 rubs against the tapered surface 38 on the outer periphery of the rotating shaft 8. The tapered inner peripheral surface 40 to be connected may be provided.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

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 ridge 17 Circumferential groove 35 Elastic member 38 Tapered surface 50 Brake disc 53 Inner side brake pad

Claims (3)

A rotating shaft (8) having a cylindrical surface (12) on the outer circumference,
A plurality of planetary rollers (13) that roll and contact the cylindrical surface (12),
A carrier (14) that holds the plurality of planetary rollers (13) so that it can rotate and revolve.
An outer ring member (5) arranged 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 circumference of the outer ring member (5) and
It has a spiral groove or a circumferential groove (17) provided on the outer periphery of each planet roller (13) so as to engage with the spiral ridge (16).
In the planetary roller screw type linear motion mechanism in which the outer ring member (5) moves in the axial direction by engaging the spiral ridge (16) with the spiral groove or the circumferential groove (17).
The carrier (14) is axially relative to the rotating shaft (8) due to the reaction force to the other axially received when the object is loaded with a load in one 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 the carrier (14) is provided on the outer periphery of the rotating shaft (8) and the carrier (14) does not move relative to the other in the axial direction with respect to the rotating shaft (8), the carrier (14) and the rotating shaft (14) When the carrier (14) is frictionally coupled with the carrier (14) so as to limit the relative rotation of the 8) and the carrier (14) moves relative to the other in the axial direction with respect to the rotation axis (8), the carrier (14) ) And the friction coupling portion that releases the friction coupling with the carrier (14) so as to allow the relative rotation of the rotation shaft (8).
The planetary roller screw type linear motion mechanism, characterized in that the friction coupling portion is arranged 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 coupling 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) that rotationally drives the rotating shaft (8) of the planetary roller screw type linear motion mechanism (1), and
A brake pad (53) that moves integrally with the outer ring member (5) of the planetary roller screw type linear motion mechanism (1), and
A brake disc (50) arranged to face the brake pad (53) and
Electric braking device with.

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