Planetary roller screw drive (PWG) and actuator with a planetary roller screw drive

Abstract

Planetary roller screw drive (1), in particular for use in an actuator for actuating a clutch of a vehicle, wherein a plurality of planets (4, 5, 6, 7, 8, 9) arranged between the spindle (2) and the ring gear (3) are in engagement with their profiles (G4, G5, G6, G7, G8, G9) with a profile (G2) of a spindle (2) and with a profile (G3) of a ring gear (3), and the profiles (G2 to G9) are formed with elevations and grooves extending therebetween, the grooves have a groove width at a base diameter (d) of the profile, the profiles (G4, G5, G6, G7, G8, G9) of the planets (4, 5, 6, 7, 8, 9) are in engagement with the profile (G2) of the spindle (2) and with the profile (G3) of the ring gear (3), wherein flanks of the elevations of the profile (G4, G5, G6, G7, G8, G9) of the planets (4, 5, 6, 7, 8,9) are in operative contact on one side with flanks of the elevations of the profiling (G3) of the ring gear (3) and on the other side with flanks of the elevations of the profiling (G2) of the spindle (2), characterized in that from the first planet (4) in the circumferential direction to the last planet (9) in the circumferential direction, which is again arranged next to the first planet (4), the width of the grooves increases from planet (4, 5, 6, 7, 8) to planet (5, 6, 7, 8, 9).

Description

[0001] The invention relates to a planetary roller screw drive (hereinafter referred to as PWG), in particular for use in an actuator for actuating a clutch of a vehicle and an actuator with a planetary roller screw drive.

[0002] Planetary roller screw drives (PWG) (also referred to as planetary roller screw spindles or planetary roller screw spindle drives) have been state of the art for many years and are described, for example, in DD 0277308 A5. For example, a planetary roller screw drive is known from the publication DE 10 2010 047 800 A1, which is contained in a hydrostatic actuator in the form of a hydrostatic clutch actuator to convert a rotary motion generated by an electric motor into an axial motion. A planetary roller screw drive with a threaded spindle and a nut arranged on the threaded spindle, and with several planets distributed over the circumference, arranged between the threaded spindle and the nut, which planets are arranged so that they can roll on the inner circumference of the nut and the outer circumference of the threaded spindle, is known from the publication DE 10 2010 011 820 A1.This solution provides a preloading device for the planets. The nut comprises two axially movable nut parts, and the preloading device comprises a spring element that is spring-loaded against one of the nut parts. The nut performs two functions: on the one hand, it is a transmission component, and on the other, it is part of the preloading device.

[0003] The publications DE 10 2010 047 800 A1 and DE 10 2013 217 472 A1 describe release systems for a clutch of a motor vehicle, in which a piston mounted axially displaceably in a housing is actuated using a drive via a PWG.

[0004] Hydrostatic clutch releasers are also known from the documents DE 10 2014 206 956 A1 and DE 10 2014 208 088 A1, which use a planetary roller gear, also known as a planetary roller screw, to convert a rotary movement into a linear actuating movement.

[0005] Generic planetary roller screw drives are also known from EP 2 541 099 A1 and DE 10 2011 088 905 A1.

[0006] In all the aforementioned prior art solutions, the planetary roller screw drive has a sleeve within which several planetary bodies are arranged around a threaded spindle at an equal distance from one another and mesh, on the one hand, with the outer profile of the threaded spindle over a length range and a large profile diameter and, on the other hand, with the inner profile of one or two ring gears over a length range with a smaller profile diameter.

[0007] The disadvantage here is that, particularly when used in actuators, the SPWG (pitch-true planetary rolling thread spindle gear) for converting a rotary movement into a linear movement is mainly loaded on one side, which results in the need for different planetary geometries, since stepped planets with an area for the spindle contact and an area for the ring gear contact are required.

[0008] Due to the axial offset of the planetary contact areas and the associated axial offset of the force introduction points on the spindle and ring gear, reaction torques arise that must be absorbed by the planetary carriers. Furthermore, the tooling required to manufacture the planetary gears is complex, and the blank must also be designed with a stepped design. Furthermore, during assembly, care must be taken to ensure the correct planetary gears are installed in the correct position.

[0009] The object of the present invention is to develop a gear in the form of a planetary roller screw drive (PWG), in particular a pitch-accurate planetary roller screw drive (SPWG), which has a simple structural design, which also takes into account a one-sided load and is easy to install, as well as to provide an actuator with a corresponding PWG.

[0010] This problem is solved by the characterising features of the first and eighth patent claims.

[0011] Advantageous embodiments arise from the subclaims.

[0012] The planetary roller screw drive (hereinafter referred to as PWG) is intended in particular for use in an actuator for actuating a clutch of a vehicle, wherein the planets have a planetary geometry for a particularly one-sided force introduction, such that the profiling of the planets engages over an equal length range with a profiling of a spindle and with a profiling of a ring gear and the profilings are designed in a thread-like manner with elevations and grooves extending therebetween and the grooves have a groove width at a root diameter of the profiling, and wherein flanks of the elevations of the profiling of the planets are in operative contact on one side with flanks of the elevations of the profiling of the ring gear and on the other side in operative contact with flanks of the elevations of the profiling of the spindle.

[0013] Preferably, the inventive design of an SPWG is used in an actuator similar to a hydrostatic clutch actuator within a master cylinder. Such actuators experience a one-sided axial load on the SPWG, which can be better absorbed by the planets thanks to the novel design of the planets.

[0014] Since the force is applied primarily from one side, the thread flanks on the spindle are subjected to only one (heavy) stress. The same applies to the groove flanks on the ring gear. In planetary gears, one flank of the protrusions adjacent to a groove is in contact with the spindle, while the other flank of an adjacent protrusion adjacent to the same groove is in contact with the ring gear.

[0015] The flanks of the elevations of the profiling of the planets are connected to grooves with different groove widths, whereby from the first planet in the circumferential direction, which has the smallest groove width, to the last planet in the circumferential direction, which has the largest groove width and is again arranged next to the first planet, the groove width increases from planet to planet, whereby the width of the flanks of the profiling decreases.

[0016] The contact points of the flanks of the elevations of the profiles of the planets, which mesh with the ring gear, must lie in a plane perpendicular to the longitudinal axis of the spindle. The contact points of the flanks of the elevations of the profiles of the planets follow the spindle pitch and thus lie on a spiral line, which results in the different groove widths of the planets.

[0017] The width of the flanks of the planets in the area of ​​the base diameter of the profiling decreases from a largest width in a circumferentially arranged first planet to a smallest width in a circumferentially arranged last planet from planet to planet, whereby the flank angle of all planets remains constant, so that only the first planet has an outer diameter of the profiling that corresponds to the nominal diameter of the profiling and the other planets in the area of ​​the profiling have a smaller outer diameter than the nominal diameter and the circumferentially last planet has the smallest outer diameter, whereby the grooves of the first planet have the same large nominal diameter for contact with the ring gear as for contact with the spindle.Overall, the flanks of the planetary profiles are designed on a first side for contact with the profile of the ring gear and on a second side for contact with the profile of the spindle.

[0018] Therefore, the flank geometry is designed in such a way that the various planets distributed over the circumference do not differ from one another in that the grooves for the spindle contact and the ring gear contact are axially separated and each axially offset from one another, but in that the planets have grooves of different groove widths from planet to planet and the contact zones of the planets, which are axially at the same height and clamp with the ring gear, are essentially aligned with one another and thus lie in a plane that is inclined perpendicular to the spindle axis, and all planets have the same root diameter of the profiles and the same flank angle.

[0019] The planets thus have a different profile such that the grooves of neighboring planets have different widths and the groove width increases from a smallest width in the area of ​​the base diameter in a first planet to a largest width in the area of ​​the base diameter in a last planet.

[0020] The width of the grooves increases from the first planet to the last planet by a proportionate amount corresponding to the number of planets, whereby the outer diameter of the planets is reduced according to the increasing size of the grooves from a largest outer diameter at the first planet to a smallest outer diameter at the last planet.

[0021] The innovative design of the planets means that the outer diameter of the planets whose flanks of a projection are axially close to one another is smaller than the nominal diameter of the first planet. This results in smaller contact areas and therefore lower local load carrying capacity. Therefore, the "gained" axial length by integrating the two groove areas is partially reduced by additional grooves required in order to ensure a comparable load carrying capacity of the overall system. Another advantage is that the groove area of ​​the planets for the ring gear contact can have the same large nominal diameter as for the spindle contact. This leads to better osculation and therefore higher load carrying capacity in the contact areas.

[0022] The inventive solution ensures that sufficient contact for power transmission between the spindle / planet / ring gear is always present for one actuation direction. This means that a PWG equipped in this way can only transmit power in one main direction with all planets; in the other direction, this power transmission would only occur with the fully formed profile.

[0023] By using planets without axial offset of the threaded areas that mesh with the spindle, the only thing that needs to be considered during assembly is maintaining the circumferential arrangement of the planets and ensuring that the correct number of planets is installed, not their alignment, which significantly simplifies assembly. Furthermore, manufacturing costs are reduced.

[0024] The invention is explained in more detail below using an exemplary embodiment and the accompanying drawings. They show: Fig. 1 a cross section through a SPWG Fig. 2 Section AA according to Fig. 1, Fig. 3 Section BB according to Fig. 1, Fig. 4 Section CC according to Fig. 1, Fig. 5 an enlarged schematic representation of a longitudinal section of the PWG according to. Fig. 2.

[0025] In Fig. 1 shows a cross-section of a pitch-true planetary roller screw drive (SPWG) 1, with which the rotary movement of a rotor (not shown) generated by an electric motor is converted into an axial lifting movement of the axially movable component of the SPWG 1, with which an axial release movement is generated, whereby, for example, when used in an actuator for clutch actuation, a release bearing is axially actuated, which acts against the diaphragm spring tongues of a diaphragm spring of a clutch and thereby actuates it (release bearing, diaphragm spring tongues, diaphragm spring and clutch are not shown).

[0026] The SPWG 1 according to the invention has a centrally arranged spindle 2 which is rotatable about a longitudinal axis A2 and which is provided with a profile G2 with a pitch in the manner of a thread.

[0027] In order to establish an operative connection between the spindle 2 and the ring gear 3 which surrounds it at a distance and has an internal profile G3, the six planets in the form of a first planet 4, a second planet 5, a third planet 6, a fourth planet 7, a fifth planet 8 and a sixth planet 9 with their profiles G4, G5, G6, G7, G8, G9 are in engagement with the profile G2 of the spindle 2 and with the profile G3 of the ring gear 3.

[0028] The first planet 4 is followed clockwise by the second planet 5, then the third planet 6, then the fourth planet 7, the fifth planet 8 and finally the sixth planet 9, which is again arranged adjacent to the first planet 4.

[0029] The ring gear is surrounded by an outer sleeve 10, which has a planetary roller carrier 11 for the end-side bearing of the planets 4 to 9. The ring gear 3 is supported by an axial bearing 12 in the direction of the acting actuating force in the main direction against the outer sleeve 10.

[0030] Preferably, the inventive design of an SPWG is used in an actuator similar to a hydrostatic clutch actuator within a master cylinder. Such actuators experience a one-sided axial load on the SPWG, which can be better absorbed by the planets thanks to the novel design of the planets.

[0031] Since the force is applied primarily from one side, the thread flanks on spindle 2 are subjected to only one (heavy) stress. The same applies to the groove flanks on ring gear 3. Thus, for the six planets 4 to 9, one flank side of the grooves of profiles G4 to G9 is in contact with spindle 2, and the opposite side of the flanks is in contact with the ring gear.3.

[0032] The contact points of the flanks of the profiles G4 to G9 of the planets 4 to 9, which mesh with the ring gear 4, lie in a plane perpendicular to the longitudinal axis of the spindle and the contact points of the flanks of the elevations of the profiles of the planets follow the spindle pitch and thus lie on a spiral line, which results in the different groove widths of the profiles of the planets and the width of the flanks of the profiles G4 to G9 of the adjacent rollers 4 to 9 gradually decreases, in this case by 1 / 6 in each case for six planets. This is evident from the Fig. 2 to 4 The width of the grooves between the flanks of the profile G4 becomes increasingly larger for the other planets 5 to 9, so that on planet 9, whose profile G9 has the greatest width of the grooves between the flanks and therefore the flanks are smaller and the outer diameter (not designated) is smaller than the undesignated outer diameter of the other planets 4 to 8. The outer diameter of the planets 4 to 9 becomes smaller from planet to planet, from a largest outer diameter on planet 4, which corresponds to the nominal diameter, to a smallest outer diameter on planet 9.

[0033] In the case of the planets (here 7, 8 and 9), whose flanks of the elevations are axially close to one another, the planets therefore have a smaller outer diameter than the nominal diameter, whereby the groove area of ​​the planets (here 4, 5, 6) for contact with the ring gear 3 has the same large nominal diameter as for contact with the spindle 2. Thus, the grooves are designed on a first side for contact with the profile G3 of the ring gear 3 and on a second side for contact with the profile G2 of the spindle 2.

[0034] From the Fig. 2 to 5 it can be seen that the profile height becomes increasingly smaller from planet 4 to planet 9.

[0035] From the enlarged view in Fig. 4 it can be seen that the planet 4 has a distance B4 between the unmarked flanks of the profile G4 and has an outer diameter D4, which here still corresponds to the unmarked nominal diameter.

[0036] The flank angle α, which in Fig. 5 is only evident from the first planet 4 and the third planet 7, is the same for all planets 4 to 9. Furthermore, all planets 4 to 9 have the same base diameter d in the area of ​​their profiles G4 to G9, which is Fig. 5 is also only visible for the first planet 4 and the third planet. The planet 7 has a profile G7 with a larger distance b7 between the undesignated flanks, which reduces its outer diameter D7, so that it is smaller than the outer diameter D4 of the first planet 4 and thus smaller than the nominal diameter.

[0037] This will result in the other Fig. 5 visible planets 7 smaller contact areas to the spindle 2 and the ring gear 3 and thus a lower local load capacity is realized.

[0038] It can be seen that one flank of the planets 4, 7 meshes with the spindle 2 and the opposite flank meshes with the ring gear 3.

[0039] The pitch-accurate planetary roller screw drive (SPWG) 1 is intended in particular for use in an actuator for actuating a clutch of a vehicle, wherein the planets have a planetary geometry for a particularly one-sided force introduction, such that the profiling of the planets engages over an equal length range with a profiling of a spindle and with a profiling of a ring gear, and wherein the groove flanks of the profiling of the planets are in operative contact with the profiling of the ring gear on one side and in operative contact with the profiling of the spindle on the other side. List of reference symbols 1 SPWG 2 spindles 3 ring gear 4 First Planet 5 Second Planet 6 Third planet 7 Fourth Planet 8 Fifth Planet 9 Sixth Planet 10 Outer sleeve 11 planetary roller carrier 12 thrust bearings A2 Longitudinal axis of spindle 2 b4 Distance between the flanks of the profile G4 b7 Distance between the flanks of the profile G7 d base diameter D4 Outer diameter of the first planet 4 D7 Outer diameter of the fourth planet 7 G2 Profiling of spindle 2 G3 Internal profiling of the ring gear 3 G4 Profiling of the first planet 4 G5 Profiling of the second planet 5 G6 Profiling of the third planet 6 G7 Profiling the Fourth Planet 7 G8 Profiling the Fifth Planet 8 G9 Profiling of the sixth planet 9 α flank angle

Claims

[1] Planetary roller screw drive (1), in particular for use in an actuator for actuating a clutch of a vehicle, wherein a plurality of planets (4, 5, 6, 7, 8, 9) arranged between the spindle (2) and the ring gear (3) are in engagement with their profiles (G4, G5, G6, G7, G8, G9) with a profile (G2) of a spindle (2) and with a profile (G3) of a ring gear (3), and the profiles (G2 to G9) are formed with elevations and grooves extending therebetween, the grooves have a groove width at a base diameter (d) of the profile, the profiles (G4, G5, G6, G7, G8, G9) of the planets (4, 5, 6, 7, 8, 9) are in engagement with the profile (G2) of the spindle (2) and with the profile (G3) of the ring gear (3), wherein flanks of the elevations of the Profiling (G4, G5, G6, G7, G8, G9) of the planets (4, 5, 6, 7, 8,9) are in operative contact on one side with flanks of the elevations of the profiling (G3) of the ring gear (3) and on the other side with flanks of the elevations of the profiling (G2) of the spindle (2), , characterized by that from the first planet (4) in the circumferential direction to the last planet (9) in the circumferential direction, which is again arranged next to the first planet (4), the width of the grooves increases from planet (4, 5, 6, 7, 8) to planet (5, 6, 7, 8, 9). [2] Planetary roller screw drive according to claim 1, characterized by that the planets (4, 5, 6, 7, 8, 9) have a different profile (G4, G5, G6, G7, G8, G9) such that the grooves of adjacent planets (4, 5, 6, 7, 8, 9) have different widths and increase from a smallest width (B4) in the region of the base diameter (d) in a first planet (4) to a largest width in the region of the base diameter (d) in a last planet (9). [3] Planetary roller screw drive according to one of claims 1 or 2, characterized by that the distance between adjacent flanks of a raised portion of the profiling of a planet (4, 5, 6, 7, 8, 9) in the region of the base diameter (d) of the profiling decreases from planet to planet, from a greatest distance in the case of a circumferentially arranged first planet (4) to a smallest distance in the case of a circumferentially arranged last planet (9), wherein the flank angle (α) of all planets (4 to 9) remains constant, so that only the first planet (4) has an outer diameter (D4) of the profiling (G4) which corresponds to the nominal diameter of the profiling (G4) and the other planets (5, 6, 7, 8, 9) have a smaller outer diameter than the nominal diameter in the region of the profiling, and the circumferentially last planet (9) has the smallest outer diameter. [4] Planetary roller screw drive according to one of claims 1 to 3, characterized bythat the grooves of the first planet (4) for contact with the ring gear (3) have the same large nominal diameter as for contact with the spindle (2). [5] Planetary roller screw drive according to one of claims 1 to 4, characterized by that the flanks of the profiles (G4 to G9) of the planets (4, 5, 6, 7, 8, 9) are designed on a first side for contact with the profile (D3) of the ring gear (3) and on a second side for contact with the profile (G2) of the spindle (2). [6] Planetary roller screw drive according to one of claims 1 to 5, characterized by that the width of the grooves from the first planet (4) to the last planet (9) decreases by a proportional amount corresponding to the number of planets (4, 5, 6, 7, 8, 9), whereby the root diameter (d) of the grooves of all planets (4, 5, 6, 7, 8, 9) and the flank angle (α) of the profiles of all planets (4, 5, 6, 7, 8, 9) are the same. [7] Planetary roller screw drive according to one of claims 1 to 6, characterized by that the outer diameter of the planets (4, 5, 6, 7, 8, 9) is reduced from a largest outer diameter (D4) in the first planet (4) to a smallest outer diameter in the last planet (9) in accordance with the increasing size of the grooves. [8] Actuator, in particular for actuating a clutch in the drive train of a vehicle with a planetary roller screw drive (1) according to one of claims 1 to 7.

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