JP2018013167A - Planetary roller screw type direct motion mechanism and electric brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planetary roller screw type direct motion mechanism capable of easily finishing the cylindrical surface on which planetary rollers on the circumference of a rotation axis are in rolling contact by polishing etc., while being switchable the load conversion rate in accordance with the axial load applied to an object from an outer ring member.SOLUTION: A planetary roller screw type direct motion in that a carrier 14 is supported by an elastic member 35 so that the carrier 14 moves relative to a rotation axis 8 by the reaction in the axial rearward direction; and a friction connection part 40 that is provided on the circumference of the rotation axis 8 and that frictionally connects with the carrier 14 in a state where the carrier 14 is not moved relative to the rotation axis 8, and that cancels the frictional coupling with the carrier 14 in a state where the carrier 14 is moved relative to the rotation axis 8. In that, the friction connection part 40 is formed as an annular member separated from a portion having a cylindrical surface 12 of the rotation axis 8.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. Here, the friction coupling portion is a tapered surface directly formed on the outer periphery of the rotating shaft.

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, the frictional coupling portion that frictionally couples with the carrier employs a tapered surface formed directly on the outer periphery of the rotating shaft. And this taper surface has an outer diameter larger than the cylindrical surface of the outer periphery of a rotating shaft (surface to which a planetary roller is rolling contact). For this reason, it is not 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 finishes the cylindrical surface on the outer periphery of the rotating shaft with high accuracy. For this reason, there is a problem that the processing cost is increased.

  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 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. In the state of relative movement in the rearward direction in the axial direction, 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 is provided on the outer periphery of the rotation shaft.
In the planetary roller screw type linear motion mechanism in which the friction coupling portion has an outer diameter larger than the cylindrical surface,
The friction coupling portion is formed as an annular member separate from the portion having the cylindrical surface of the rotating shaft, and the friction coupling portion is fitted and fixed to the outer periphery of the rotating 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.

  The frictional coupling portion has an outer diameter larger than the cylindrical surface with which the planetary roller is in rolling contact. The frictional coupling portion is formed as an annular member separate from the portion having the cylindrical surface of the rotating shaft. Therefore, the cylindrical surface with which the planetary roller is in rolling contact 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 coupling portion, relative rotation with respect to the rotation shaft is restricted by fitting with a non-circular cross-section portion formed on the outer periphery of the rotation shaft, and attached to the outer periphery of the rotation shaft. It is possible to employ a structure in which the axial movement with respect to the rotating shaft is restricted by a retaining ring.

  If it does in this way, the operation | work which attaches a friction coupling part to the outer periphery of a rotating shaft is easy.

  In addition, as the friction coupling portion, a configuration in which an outer periphery of the rotating shaft is fitted with a margin can be employed. Examples of means for providing a tightening allowance include press fitting, shrink fitting, and the like.

  If it does in this way, the shape of the inner periphery of a friction coupling part and the shape of the fitting part with respect to the friction coupling part of the outer periphery of a rotating shaft can be made into a simple thing (for example, cylindrical surface), a friction coupling part and rotation The manufacturing cost of the shaft can be reduced.

  Moreover, as the friction coupling part, a welded part to the outer periphery of the rotating shaft may be adopted.

  Also, splines are formed on the outer periphery of the rotating shaft, the splines have a hardness higher than the hardness of the inner peripheral portion of the friction coupling portion, and the spline is bitten into the inner peripheral portion of the friction coupling portion. The friction coupling portion may be fixed to the rotating shaft.

  If it does in this way, it will become possible to fix a friction coupling part to a rotating shaft with very high intensity.

  In addition, a spline is formed on the inner periphery of the friction coupling portion, and the spline has a hardness higher than the hardness of a fitting portion with respect to the friction coupling portion on the outer periphery of the rotation shaft, and the spline is formed on the rotation shaft. The friction coupling portion may be fixed to the rotating shaft by biting into the outer periphery of the rotating shaft.

  If it does in this way, it will become possible to fix a friction coupling part to a rotating shaft with very high intensity.

  As the contact surface of the friction coupling portion with respect to the carrier, a taper shape having an outer diameter that decreases from the front side toward the rear side in the axial direction can be adopted.

  In this case, the contact surface pressure between the frictional coupling portion and the carrier is increased by the wedge action of the taper, so that it is possible to effectively prevent slippage between the rotating shaft and the carrier.

Moreover, in this invention, the thing of the following structures is also provided 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. In addition, since the friction coupling portion is formed as an annular member separate from the portion having the cylindrical surface of the rotating shaft, the cylindrical surface with which the planetary roller is in rolling contact may be the maximum diameter portion of the rotating shaft. Is possible. 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 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 (A) is a figure which shows the modification of the friction coupling part shown in FIG. 4, (b) is sectional drawing along the VIII-VIII line of (a). (A) is a figure which expands and shows the frictional coupling part of the planetary roller screw-type linear motion mechanism of 2nd Embodiment, (b) is sectional drawing along the IX-IX line of (a). (A) is a figure which expands and shows the friction coupling | bond part of the planetary roller screw-type linear motion mechanism of 3rd Embodiment, (b) is sectional drawing along the XX line of (a). The figure which expands and shows the frictional coupling part of the planetary roller screw-type linear motion mechanism of 4th Embodiment. The figure which expands and shows the frictional coupling part of the planetary roller screw-type linear motion mechanism of 5th Embodiment. (A) is a figure which expands and shows the friction coupling | bond part of the planetary roller screw-type linear motion mechanism of 6th Embodiment, (b) is sectional drawing along the XIII-XIII line | wire of (a). The figure which shows the process which fixes the friction coupling part shown in FIG. 13 to the fitting shaft part of a rotating shaft. The figure which shows the process which fixes the frictional coupling part of the planetary roller screw-type linear motion mechanism of 7th Embodiment to the fitting shaft part of a rotating shaft. 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 device shown in FIG. 16 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. A slide bearing 23 that is in sliding contact with the outer periphery of the rotary shaft 8 is mounted on the inner periphery of the axial rear disk 21.

  Between the inner periphery of each planetary roller 13 and the outer periphery of the support pin 18, a radial bearing 24 that supports the planetary roller 13 so as to rotate is incorporated. A thrust bearing 25 is incorporated between each planetary roller 13 and the axially rear disk 21 to support the planetary roller 13 in the axial direction in a rotatable state. Further, between the thrust bearing 25 and the axial rear side disk 21, an aligning seat 26 that supports the planetary roller 13 so as to be tiltable via the thrust bearing 25 is incorporated.

  The outer ring member 5 is supported by an inner surface of a receiving hole 27 formed in the housing 15 so as to be slidable in the axial direction. Inside the housing 15, a bearing support member 28 is fixed at a position away from the carrier 14 in the axial direction rearward. The bearing support member 28 is formed in an annular shape that penetrates the rotary shaft 8. A radial bearing 29 that rotatably supports the rotary shaft 8 is incorporated in the inner periphery of the bearing support member 28. As the radial bearing 29, for example, a sintered slide bearing or a deep groove ball bearing can be adopted.

  The bearing support member 28 is restricted from moving rearward in the axial direction by a projection 30 provided on the inner periphery of the accommodation hole 27, and is moved forward in the axial direction by a retaining ring 31 attached to the inner periphery of the accommodation hole 27. It is regulated. In addition, relative movement of the rotating shaft 8 in the axial direction relative to the bearing support member 28 is restricted by a retaining ring 32 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 friction coupling portion 40 fixed to the outer periphery of the axially front end portion of the rotating shaft 8.

  Here, the radial bearing 29 is incorporated in a state in which relative movement in the axial direction relative to the bearing support member 28 is restricted, and the retaining ring 32 is attached to the radial bearing 29 on the rear side in the axial direction.

  A thrust bearing 33 is incorporated between the carrier 14 and the bearing support member 28 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. 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 applied to the carrier 14), the elastic member 35 is previously axially moved. The compressed state is adopted, and the preload is applied from the elastic member 35 to the carrier 14.

  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 28. 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 28.

  As shown in FIGS. 4 and 5, the friction coupling portion 40 is an annular member that is separate from the portion having the cylindrical surface 12 of the rotating shaft 8. The friction coupling portion 40 is fitted and fixed to the outer periphery of a fitting shaft portion 8a formed at the front end of the rotating shaft 8 in the axial direction. The fitting shaft portion 8 a has a shape that does not have a portion that extends radially outward from the outer diameter of the cylindrical surface 12. On the other hand, the frictional coupling part 40 has a shape having an outer diameter larger than that of the cylindrical surface 12 (that is, a portion exceeding the outer diameter of the cylindrical surface 12 in the radial direction).

  Relative rotation with respect to the rotating shaft 8 is restricted by fitting the frictional coupling portion 40 to a non-circular rotation-preventing portion 41 formed on the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. Here, the rotation preventing portion 41 is a portion having a shape in which a part of the circumference is a plane parallel to the axis of the rotation shaft 8. Further, the friction coupling portion 40 is restricted from moving forward in the axial direction with respect to the rotating shaft 8 by a retaining ring 42 attached to the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. Further, the friction coupling portion 40 is restricted from moving rearward in the axial direction with respect to the rotating shaft 8 by a step portion 43 formed at the rear end in the axial direction of the fitting shaft portion 8a. The stepped portion 43 is a portion whose outer diameter increases from the front side in the axial direction toward the rear side in the axial direction.

  A tapered surface 44 whose outer diameter decreases from the front side in the axial direction toward the rear side is formed on the outer periphery of the friction coupling portion 40. The inclination angle of the taper surface 44 (angle formed by the taper surface 44 with respect to the direction parallel to the axial direction) is set in the range of 5 to 20 °.

  A tapered inner peripheral surface 45 facing the tapered surface 44 is formed on the inner periphery of the front disk 20 in the axial direction of the carrier 14. The inclination angle of the tapered inner peripheral surface 45 (the angle formed by the tapered inner peripheral surface 45 with respect to the direction parallel to the axial direction) is set in the range of 5 to 20 °. The tapered inner peripheral surface 45 is preferably formed to have the same inclination angle as the tapered surface 44.

  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 taper inner peripheral surface 45 of the carrier 14 is in contact with the taper surface 44 on the outer periphery of the friction coupling portion 40. At this time, the tapered inner peripheral surface 45 and the tapered surface 44 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 45 and the tapered surface 44. It becomes a state.

  On the other hand, as shown in FIG. 7, the carrier 14 is relatively moved axially rearward with respect to the rotation shaft 8 (that is, the carrier 14 is loaded with the axially rearward load, and the elastic member 35 is compressed by the load. In an increased amount), the taper inner peripheral surface 45 of the carrier 14 is separated from the taper surface 44 on the outer periphery of the friction coupling portion 40. At this time, the frictional coupling between the tapered inner peripheral surface 45 and the tapered surface 44 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 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 25 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.

  16 and 17 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 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 axial movement speed 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 carrier 14 is frictionally coupled to the friction coupling portion 40 in a state where no load is applied to the object from the outer ring member 5 in the axial direction, and the carrier 14 Since the relative rotation of 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 carrier 14 and the friction coupling portion 40 is released, and the relative rotation between the carrier 14 and the rotating shaft 8 is allowed. The moving speed in the axial direction of the outer ring member 5 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 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 friction coupling portion 40 shown in FIG. 2 can be formed as an integral part without a joint with respect to the portion having the cylindrical surface 12 of the rotating shaft 8. Since the portion 44 has a larger outer diameter than the portion of the cylindrical surface 12, when the cylindrical surface 12 is finished by polishing or the like, a low-cost processing method (for example, centerless through polishing) cannot be employed, and the cylinder There exists a problem that the processing cost for finishing the surface 12 with high precision becomes high.

  On the other hand, in the planetary roller screw type linear motion mechanism 1 of this embodiment, the frictional coupling portion 40 is formed as an annular member separate from the portion having the cylindrical surface 12 of the rotating shaft 8. The cylindrical surface 12 with which 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 (for example, centerless through polishing) that processes the outer periphery of the rotating shaft 8 while rolling and supporting the outer periphery of the rotating shaft 8, and the cylindrical surface on which the planetary roller 13 is in rolling contact. 12 can be easily finished by polishing or the like. 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.

  Further, in this embodiment, the friction coupling portion 40 is fitted to a non-circular rotation-preventing portion 41 formed on the outer periphery of the rotation shaft 8 to restrict relative rotation of the friction coupling portion 40 with respect to the rotation shaft 8, The retaining ring 42 attached to the outer periphery of the rotating shaft 8 restricts the axial movement of the friction coupling portion 40 with respect to the rotating shaft 8. By doing in this way, the operation | work which attaches the friction coupling part 40 to the outer periphery of the rotating shaft 8 becomes easy.

  As shown in FIG. 5, as the non-rotating portion 41 having a non-circular cross section, when a portion having a shape in which a part of the circumference is a plane parallel to the axis of the rotating shaft 8 is employed, the rotating portion 41 is arranged in the circumferential direction. When a plurality (two in the figure) are provided at equal intervals, it is possible to improve the positioning accuracy of the center of the friction coupling portion 40 with respect to the center of the rotating shaft 8, but as shown in FIGS. 8 (a) and 8 (b). Only one detent 41 may be provided.

  9A and 9B show 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.

  Relative rotation with respect to the rotating shaft 8 is restricted by fitting the frictional coupling portion 40 to a non-circular rotation-preventing portion 41 formed on the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. Here, the anti-rotation portion 41 is a portion whose cross-sectional shape is a polygon. The friction coupling portion 40 is restricted from moving forward in the axial direction with respect to the rotating shaft 8 by a retaining ring 42 attached to the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. Further, the friction coupling portion 40 is restricted from moving rearward in the axial direction with respect to the rotating shaft 8 by a step portion 43 formed at the rear end in the axial direction of the fitting shaft portion 8a. Even if it does in this way, the operation | work which attaches the frictional coupling part 40 to the outer periphery of the rotating shaft 8 is easy like 1st Embodiment.

  FIGS. 10A and 10B show a third embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  Relative rotation with respect to the rotating shaft 8 is restricted by fitting the frictional coupling portion 40 to a non-circular rotation-preventing portion 41 formed on the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. Here, the rotation preventing portion 41 is a spline (a plurality of axially extending protrusions arranged at equal intervals in the circumferential direction). The friction coupling portion 40 is restricted from moving forward in the axial direction with respect to the rotating shaft 8 by a retaining ring 42 attached to the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. Further, the friction coupling portion 40 is restricted from moving rearward in the axial direction with respect to the rotating shaft 8 by a step portion 43 formed at the rear end in the axial direction of the fitting shaft portion 8a. Even if it does in this way, the operation | work which attaches the frictional coupling part 40 to the outer periphery of the rotating shaft 8 is easy like 1st Embodiment.

  FIG. 11 shows a fourth embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The friction coupling portion 40 is fitted to the outer periphery of the fitting shaft portion 8a of the rotating shaft 8 with a margin. Here, the inner periphery of the friction coupling portion 40 is a cylindrical surface 60, and the outer periphery of the fitting shaft portion 8 a is also a cylindrical surface 61. In a state before the friction coupling portion 40 is fitted to the fitting shaft portion 8a (that is, a state where the friction coupling portion 40 is removed from the fitting shaft portion 8a), the inner diameter of the cylindrical surface 60 on the inner periphery of the friction coupling portion 40 is The outer diameter of the cylindrical surface 61 of the outer periphery of the fitting shaft portion 8a is set to be smaller, and the inner periphery of the friction coupling portion 40 is fitted by press-fitting the fitting shaft portion 8a into the friction coupling portion 40. The outer periphery of the shaft portion 8a is held in a tightened state. In this way, the shape of the inner periphery of the friction coupling portion 40 and the shape of the fitting portion of the outer periphery of the rotary shaft 8 with respect to the friction coupling portion 40 can be simplified. 8 can be reduced. A shrink fit may be used instead of the press fit.

  FIG. 12 shows a fifth embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The friction coupling portion 40 is welded to the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. Here, the inner periphery of the friction coupling portion 40 is a cylindrical surface 62, and the outer periphery of the fitting shaft portion 8 a is also a cylindrical surface 63. The inner diameter of the cylindrical surface 62 on the inner periphery of the friction coupling portion 40 is set slightly larger than the outer diameter of the outer cylindrical surface 63 of the fitting shaft portion 8a. A bead 64 in which the base material of the friction coupling portion 40 and the base material of the rotary shaft 8 are melted and integrated is formed at the front end in the axial direction of the fitting portion between the cylindrical surface 62 and the cylindrical surface 63. In this way, the shape of the inner periphery of the friction coupling portion 40 and the shape of the fitting portion of the outer periphery of the rotary shaft 8 with respect to the friction coupling portion 40 can be simplified. 8 can be reduced.

  FIGS. 13A and 13B show a sixth embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  A spline 65 is formed on the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. The spline 65 has a hardness higher than the hardness of the inner peripheral portion of the friction coupling portion 40, and the friction coupling portion 40 is fixed to the rotating shaft 8 by the spline 65 biting into the inner peripheral portion of the friction coupling portion 40. Has been.

  A method of fixing the friction coupling portion 40 to the fitting shaft portion 8a will be described. As shown in FIG. 14, first, the spline 65 is formed on the outer periphery of the fitting shaft portion 8a of the rotating shaft 8, and then the outer periphery of the fitting shaft portion 8a is cured by heat treatment. On the other hand, the inner peripheral portion of the friction coupling portion 40 is a cylindrical surface 66. The cylindrical surface 66 is not heat treated. Here, the hardness of the spline 65 is higher than the hardness of the inner peripheral portion of the friction coupling portion 40. The circumscribed circle diameter of the spline 65 is larger than the inner diameter of the cylindrical surface 66. In this state, the fitting shaft portion 8 a of the rotating shaft 8 is press-fitted into the friction coupling portion 40. Thereby, the spline 65 bites into the cylindrical surface 66 on the inner periphery of the frictional coupling part 40, and the inner peripheral part of the frictional coupling part 40 is plastically deformed. By this plastic deformation, the friction coupling portion 40 is firmly fixed to the fitting shaft portion 8a.

  Thus, if the friction coupling part 40 is fixed to the rotating shaft 8 by biting the spline 65 into the inner peripheral part of the friction coupling part 40, the friction coupling part 40 can be fixed with extremely high strength.

  FIG. 15 shows a method of fixing the friction fitting portion 40 to the fitting shaft portion 8a in the seventh embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  First, the spline 67 is formed on the inner circumference of the friction coupling portion 40, and then the inner circumference of the friction coupling portion 40 is cured by heat treatment. On the other hand, the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8 is a cylindrical surface 68. The cylindrical surface 68 is not heat treated. Here, the hardness of the spline 67 is higher than the hardness of the outer periphery of the fitting shaft portion 8 a of the rotating shaft 8. The inscribed circle diameter of the spline 67 is smaller than the outer diameter of the cylindrical surface 68. In this state, the fitting shaft portion 8 a of the rotating shaft 8 is press-fitted into the friction coupling portion 40. Thereby, the spline 67 bites into the outer peripheral cylindrical surface 68 of the fitting shaft portion 8a, and the outer peripheral portion of the fitting shaft portion 8a is plastically deformed. By this plastic deformation, the friction coupling portion 40 is firmly fixed to the fitting shaft portion 8a.

  Thus, if the friction coupling part 40 is fixed to the rotating shaft 8 by biting the spline 67 into the outer periphery of the fitting shaft part 8a, the friction coupling part 40 can be fixed with extremely high strength.

  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 40 Friction coupling part 41 Anti-rotation part 42 Retaining ring 50 Brake disk 53 Inner brake pad 65, 67 Spline

Claims (8)

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);
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 (35) 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. A frictional coupling part (40) for releasing the frictional coupling with the carrier (14) is provided on the outer periphery of the rotating shaft (8),
In the planetary roller screw type linear motion mechanism in which the friction coupling portion (40) has a larger outer diameter than the cylindrical surface (12),
The friction coupling portion (40) is formed as an annular member separate from the portion having the cylindrical surface (12) of the rotating shaft (8), and the friction coupling portion (40) is formed as the rotating shaft (8). A planetary roller screw type linear motion mechanism characterized by being fitted and fixed to the outer periphery of the roller.   The friction coupling part (40) is fitted to a non-circular cross-section part (41) formed on the outer periphery of the rotary shaft (8) to restrict relative rotation with respect to the rotary shaft (8), The planetary roller screw type linear motion mechanism according to claim 1, wherein axial movement relative to the rotary shaft (8) is restricted by a retaining ring (42) attached to an outer periphery of the rotary shaft (8).   The planetary roller screw type linear motion mechanism according to claim 1, wherein the friction coupling portion (40) is fitted to the outer periphery of the rotating shaft (8) with a margin.   The planetary roller screw type linear motion mechanism according to claim 1, wherein the friction coupling portion (40) is welded to an outer periphery of the rotating shaft (8). Splines (65) are formed on the outer periphery of the rotating shaft (8),
The spline (65) has a hardness higher than the hardness of the inner peripheral portion of the friction coupling portion (40),
2. The planetary roller screw type according to claim 1, wherein the spline (65) bites into an inner peripheral portion of the friction coupling portion (40) so that the friction coupling portion (40) is fixed to the rotating shaft (8). Linear motion mechanism. A spline (67) is formed on the inner periphery of the friction coupling portion (40),
The spline (67) has a hardness higher than the hardness of a fitting portion with respect to the friction coupling portion (40) on the outer periphery of the rotating shaft (8),
The planetary roller screw type linear motion mechanism according to claim 1, wherein the friction coupling portion (40) is fixed to the rotary shaft (8) by the spline (67) biting into an outer periphery of the rotary shaft (8). .   The planet according to any one of claims 1 to 6, wherein a contact surface of the friction coupling portion (40) with respect to the carrier (14) has a tapered shape in which an outer diameter decreases from an axial front side toward a rear side. Roller screw type linear motion mechanism. The planetary roller screw type linear motion mechanism (1) according to any one of claims 1 to 7,
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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