EP3077707A1

EP3077707A1 - Actuator having a planetary roller spindle (pwg)

Info

Publication number: EP3077707A1
Application number: EP14827166.1A
Authority: EP
Inventors: Lars Schumann; Lászlo Mán; Peter Greb
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2013-12-06
Filing date: 2014-11-28
Publication date: 2016-10-12
Also published as: CN105793614A; KR20160094964A; US20160305519A1; KR102312769B1; JP6598775B2; CN105793614B; WO2015081951A1; US10487927B2; JP2017503124A; DE112014005561A5

Abstract

The invention relates to an actuator having a planetary roller spindle (PWG), in particular for actuating a clutch of a vehicle, wherein a central spindle having a pitch is rotationally coupled to a rotor of a drive and can by driven by the drive about a rotation axis, and a plurality of planetary rollers are engaged with the spindle and mesh with a ring gear encircling the planetary rollers, said ring gear having grooves in the circumferential direction, wherein the planetary rollers are positioned on both ends in a planetary roller carrier. According to the invention the planetary roller carriers are supported on both ends in a rotationally fixed manner such that the pitch of the spindle can be unambiguously associated with an axial stroke of a component that is axially movable by means of the planetary roller spindle and that is operatively connected to an axially movable piston.

Description

Actuator with planetary roller screw (PWG)

The invention relates to an actuator with Planetenwälzgewindespindel (PWG) according to the preamble of the first claim.

Planetenwälzgewindspindeln (PWG) (also referred to as Planetenwälzgewindsspindeltrie- be) have been state of the art for many years and are described for example in DD 0277308 A5. From DE 10 2010 047 800 A1, for example, a planetary roller screw drive is known which is contained in a hydrostatic actuator in the form of a hydrostatic clutch actuator in order to convert a rotational movement generated by means of an electric motor E into an axial movement. A Planetenwälzgewindetrieb with a threaded spindle and arranged with a threaded spindle on the nut and with several circumferentially distributed between the threaded spindle and the nut arranged planets, which are arranged abradable on the inner circumference of the nut and on the outer circumference of the threaded spindle, is known from the document DE 10th 2010 011 820 A1 known. In this solution, a biasing means for the planet is provided, wherein the nut has two mutually axially movable male parts, and wherein the biasing means comprises a spring member urged against the one nut member. The nut takes on two functions: on the one hand, it is gear part and on the other hand, it is part of the pretensioner.

It is also known (see DE 10 2011 088 995 A1) an absolute measurement for a slip detection of a PWG with a arranged on a threaded spindle spindle nut and with a plurality of distributed over the circumference arranged planetary, which are in rolling engagement with the threaded spindle and the spindle nut in that a sensor element arranged axially non-displaceably with respect to the spindle nut detects an axial displacement of the threaded spindle and the spindle nut relative to one another, wherein the spindle nut is rotatably mounted on a housing having the sensor element about the spindle axis.

In a not yet published application, a release system for a clutch of a motor vehicle is described in which using a drive via a PWG in a housing axially displaceably mounted piston is actuated, wherein the position of the piston can be detected with a sensor.

However, the known systems are relatively expensive, since a bias voltage must be realized and slip-induced slope change of the PWG system make a displacement sensor for exact positioning necessary.

For the boundary condition that the pitch in the ring gear nut and on the planetary rollers 3 is zero, the following limit cases arise: Limit: in case of sticking between the spindle and the planetary rollers, there is no feed / axial movement with the spindle rotating relative to it, whereby there is 100% slip between planetary and ring gear nuts and the efficiency is zero.

Limit case 2: in case of sticking between planetary rollers and ring gear nut a spindle pitch is 1: 1 implemented with 100% slip between planetary rollers and spindle, whereby the Wrcungsgrad is very low.

The object of the present invention is to develop an actuator with a Planetenwälzgewindetrieb, which avoids a slip-induced slope change, ensures good efficiency and has a simple structure.

This object is solved by the characterizing features of the first claim.

Advantageous embodiments emerge from the subclaims.

The actuator in this case has a Planetenwälzgewindespindel (PWG) and is used in particular for the operation of a clutch of a vehicle, wherein a centric pitch having a spindle rotatably connected to a rotor of a drive and driven with the drive about an axis of rotation and a plurality of planetary rollers with the Spindle engaged and meshing with a planetary rollers ring gear having grooves in the circumferential direction, the planetary rollers are positioned at both ends in a planetary roller carrier and according to the invention the planetary roller carriers are rotatably supported at both ends, such that a fixed assignment the pitch of the spindle to an axial stroke of a means of the PWG axially movable member, which is operatively connected to an axially actuated piston, is feasible.

This makes it possible for the first time on the slope of the spindle to determine the axial stroke without consuming sensors to use it.

The first use of a PWG with a rotatably supported planetary roller carrier and associated a schlupfunabhängigen system pitch can be omitted in an actuator on a displacement sensor (according to the state of the art, this is due to slippage necessary) and the associated components in the electronics, because the slip does not affect the axial movement of the axially movable components of the PWG.

Advantageously, the solution according to the invention is combined with the possibility of referencing, whereby an axial reference position / zero position of an axially movable element of the actuator can be determined. The two planet carriers are preferably non-rotatably supported in one, the ring gear surrounding and radially inwardly pointing at both ends first sleeve and this first sleeve is rotatably and axially displaceable received directly or via a second sleeve or other intermediate element in a frame-mounted housing. The ring gear transmits the axial forces of the planetary rollers on the first sleeve, which abuts against the first sleeve secured against rotation second sleeve, with which the piston is connected, for example, actuates a clutch.

The housing is rotatably attached to a drive (preferably an electric motor) receiving engine block and biased against at least one spring or a spring assembly, wherein the first sleeve against a disengagement of the piston against the spring assembly is movable until it is stretched to block. This makes it possible to determine the zero position or an axial reference point of the PWG and thus of the piston via the characteristic curve of the spring assembly.

The rotatably and axially fixedly connected to the planetary roller carrier first sleeve transmits the axial forces and the movement in the form of an axial stroke either directly or via the second sleeve (or an equivalent intermediate element) on the piston, whereby this performs a disengaging movement. In the homing direction, the first sleeve presses on the spring / spring assembly to determine the axial reference point / zero point.

After the reference point / zero point is known, the axial position of the first sleeve and thus the associated with this other axially movable components (second sleeve / piston) can be determined on the slope of the spindle, as it rotatably fixed to the housing together with the planetary roller carriers are.

By preventing rotation of the planetary roller carrier in combination with the spring assembly, which axially allows a reference point, the position determination by means of a rotary encoder of the electric motor or the spindle can be realized. Furthermore, the axial position determination on the motor characteristic curve or the characteristic of the motor current is possible because these characteristics correspond to the characteristic curve of the spring / spring assembly (force / displacement curve).

Furthermore, the position of the clutch on the characteristic curve can be determined by means of a plausibility check.

The spindle has a pitch 0 and is advantageously combined only with an angle encoder for an angle / position sensor which is rotationally connected to the rotor of a driving electric motor.

The first sleeve is preferably formed in two parts and is connected to each other, for example via a, this surrounding clamp together axially and rotationally fixed. The second sleeve has on its outer diameter to a longitudinal toothing, which is in engagement with a longitudinal toothing on the inner contour of the housing, such that the second sleeve is rotatably and axially slidably received in the housing. Furthermore, the second sleeve is connected to the piston, so that an axial movement is transmitted to the piston and thereby the clutch is actuated.

With the solution according to the invention a slip-induced slope change is avoided (not avoiding slippage), wherein a good efficiency is maintained. Thus, the use of a displacement sensor can be omitted and the electronics in actuators, which must approach a specific position due to increased functional safety requirements, be simplified. Only one integrated rotary encoder is used for positioning, the signal of which is only adjusted against plausible referencing against a characteristic curve.

The invention will be explained in more detail with reference to an embodiment and associated drawings.

Show it:

FIG. 1 shows the longitudinal section of the actuator,

FIG. 2 shows the three-dimensional representation of a longitudinal section with a marked force flow F in the direction of disengagement of the piston and FIG

FIG. 3 shows the longitudinal section of the PWG with first and second sleeves,

FIG. 4 shows a three-dimensional representation of the PWG according to FIGS. 2 and 3, but without a second sleeve,

FIG. 5 shows a three-dimensional partial illustration of the housing,

In Figure 1, an actuator is shown in longitudinal section having a Planetenwälzgewindespindel (PWG), with which the rotational movement generated by an electric motor E converts into an axial stroke movement, by which a piston 1 disengageable and thereby a clutch, not shown, can be actuated. The gear in the form of a Planetenwälzgewindespindel PWG (see also Fig. 2 and 3) has a spindle 2 with an external thread 2.1 with a slope which rotatably connected to an unspecified rotor of the drive (here E-motor E) and the drive about a rotational axis L can be driven. With the spindle 2 are a plurality of planetary rollers 3 into engagement, which mesh with a planetary rollers 3 surrounding ring gear 4, the grooves in the circumferential direction. Preferably, three or a multiple of three planetary rollers 3 are positioned around the spindle 2 in the circumferential direction. The Planetary rollers 3 are rotatably received at both ends in each case a planetary roller carrier 5, wherein the two planetary roller carrier 5 are rotatably supported.

For this purpose, each planetary roller carrier 5 is received in an end radially inwardly facing portion A1 of the first sleeve A, which is divided into two halves, which have a radially outwardly facing collar 6 and rotatably against each other via a bracket 7 (preferably made of sheet metal) and axially fixed to each other. The first sleeve A sits non-rotatably and axially fixed in a second sleeve B, which in turn rotatably but axially slidably received in a housing 8 and sealed to this. The second sleeve B has an outer toothing B1 on its outer diameter (see FIG. 2), which corresponds to an internal toothing 8.1 (see also FIG. The housing 8 is fastened to the motor housing 9 of the electric motor E in a frame-fixed manner via a flange region 8.2 pointing radially outwards.

Thus, via the housing 8, the second sleeve B, the first sleeve A and the planetary roller carrier 5 are arranged rotationally fixed.

The ring gear 4 transmits via two thrust bearings 10 of the PWG, which ensure the internal PWG force transmission, the axial forces from the planetary rollers 3 by means of positive engagement (not designated circumferential grooves) in the sleeve A.

The first sleeve A forwards the axial forces and the axial stroke via the second sleeve B to the element to be actuated (here the piston 1), which, according to FIG. 1, via a receiving part 11 at the end pointing outwards through a central opening 8.3 of the housing 8 the second sleeve B is attached.

From Figure 1 it can be seen that the housing 8 with its radially outwardly facing flange 8.2 here biases a spring assembly 12 in the form of a cup spring assembly 12 against the motor housing 9. The first sleeve A presses in the referencing, which is directed against the disengagement of the piston 1, with the radially outwardly facing collar 6, which is enclosed with the clamp 7, on the spring assembly 12, which is biased by the housing 8 to a to ensure plausible homing.

The spindle 2 is provided with a pitch Φ 0 and has an angle sensor, not shown, for an angle and / or position sensor, which / which is rotationally connected to the rotor of the driving electric motor E is / are.

A bearing unit 13 is preferably designed as a 4-point bearing, here as a combination of axial and radial bearings, to accommodate the axial forces and the rotation of the spindle 2 to the housing 8. The motor housing 9 has the stator 9.1, the required non-designated electronics and interfaces to the outside (plug 14, capacitor 15, etc.). Furthermore, with the motor housing 9, the housing 8 is fixed to the frame, in which on the internal teeth 8.1 in the form of longitudinal grooves, the Drehabstützung of the planetary roller carrier 5 is realized indirectly via the first sleeve A and the second sleeve B.

By using a PWG with rotatably supported planetary roller carrier 5 and associated a schlupfunabhängigen system pitch in combination with the possibility of referencing in the actuator according to the invention on a displacement sensor (according to the state of the art is this due to slippage necessary) and the associated components in the Electronics are dispensed with.

In Figures 2 and 3, the transmission of the actuator in the form of Planetenwälzgewindespindel PWG is again shown for clarity, which has already been described in Figure 1 essentially.

In this case, in FIG. 2, the force profile F is represented by the spindle 2 on the second sleeve B, with which the piston 1, not shown, is actuated, with the arrow, and it is shown in FIGS. 2 and 3 that the external teeth B1 are in the form of longitudinal grooves in FIG second sleeve B can be seen. The second sleeve B extends with the region having the external teeth B1, only over one half of the first sleeve A and has after the external teeth B1 on a radially inwardly facing shoulder B2, on which the first sleeve A axially abuts inside. Radially inwardly, a tubular region B3 adjoins the shoulder B2, which surrounds the spindle 2 and on which the piston 1 (see Fig. 1) is fastened.

FIG. 4 shows a three-dimensional illustration of the PWG according to FIGS. 2 and 3, but only with sleeve A and without second sleeve B. At the radially inward-pointing region A1, the first sleeve A has recesses A2 into which the planetary roller carriers 5 engage in a form-fitting manner. so that they are rotationally fixed to the first sleeve A. The two halves of the first sleeve A and the bracket 7 are rotatably secured together by means of interlocking mold elements 16 and secured axially.

FIG. 5 shows an individual part illustration 5 of the housing 8, which has an internal toothing 8.1 in the form of a longitudinal toothing or longitudinal grooves and thus rotatably and axially displaceably receives the second sleeve B with its external toothing B1. The housing 8 is fastened with its flange region 8.2 on the motor housing 9 (not shown here) and has screw holes 8.4 for this purpose.

According to the present invention, the planetary roller carrier is first rotationally supported. The spindle 2 is rotationally connected to the rotor and the ring gear 4 transmits the axial forces of the planetary rollers 3 on a first sleeve A, which is preferably formed in two parts as a sheet metal part. The first sleeve A strikes against a second sleeve B, which allows the lifting movement of the piston 1. Sleeve A is secured against rotation sleeve B and the planetary roller carrier 5 are mounted against rotation in A. By this rotation in combination with the spring assembly 12, which axially allows a reference point, a position measurement can be done in a simple manner by means of a rotary encoder of the electric motor E or the spindle 2. In a preferred embodiment, a plausibility check is still carried out on the characteristic curve of the clutch to determine the position correctly.

It can avoid the slip-induced slope change (not avoiding slippage) while maintaining a good efficiency can be realized. Furthermore, a simple possibility of referencing is provided. As a result, the displacement sensor can be dispensed with and the electronics in actuators that have to approach a specific position due to increased functional safety requirements are eliminated. Only one integrated rotary encoder is used for positioning, the signal of which is only adjusted against plausible referencing against a characteristic curve.

LIST OF REFERENCES

1 piston

spindle

.1 external thread

3 planetary roles

ring gear

5 planetary roller carriers

6 fret

7 clip

8 housing

8.1 Internal toothing

8.2 Flange area

8.3 opening

8.4 screw holes

9 motor housing

9.1 stator

10 thrust bearings

1 1 receiving part

12 spring pack

13 storage unit

14 plugs

5 electronics (capacitor)

16 form elements

A first sleeve

A1 radially inwardly facing area

B second sleeve

B1 external toothing

B2 paragraph

B3 tubular area

E electric motor

F power flow

L rotation axis

PWG planetary roller screw

Claims

claims

1. Actuator with Planetenwälzgewindespindel (PWG), in particular for the actuation of a clutch of a vehicle, wherein a centric pitch having a spindle (2) rotatably connected to a rotor of a drive and the drive about a rotational axis (L) is driven and a plurality of planetary rollers (3) meshing with the spindle (2) and meshing with a ring gear (4) having circumferential grooves in the planetary rollers (3), the planetary rollers (3) being positioned at both ends in a planetary roller carrier (5) are, characterized in that the planetary roller carrier (5) are rotatably supported at both ends such that a fixed assignment of the pitch of the spindle (2) to an axial stroke of an axially movable member by means of the PWG, which with an axially actuated piston (1) is actively connected, is realized.

2. Actuator according to claim 1, characterized in that the planetary roller carrier (5) rotationally fixed in one, the ring gear (4) and rotationally fixed at both ends radially inwardly facing first sleeve (A) are supported, and in that the first sleeve (A ) directly or via a second sleeve (B) rotatably and axially displaceable in a frame-mounted housing (8) is added.

3. Actuator according to claim 1 or 2, characterized in that the ring gear (4) transmits the axial forces of the planetary rollers (3) on the first sleeve (A) which abuts against the first sleeve (A) secured against rotation second sleeve (B) to which the piston (1) is connected.

4. Actuator according to one of claims 1 to 3, characterized in that the housing (8) rotatably attached to a drive motor block and is biased against at least one spring or a spring assembly (12) and that the first sleeve (A) against a disengagement movement of the piston (1) against the spring assembly (12) is movable until it is stretched to block and on the characteristic of the spring assembly (12) a zero position / an axial reference point of the PWG and thus the piston (1) can be determined.

5. Actuator according to one of claims 1 to 8, characterized in that with the planetary roller carrier (5) rotatably and axially fixedly connected first sleeve (A) the axial forces and the movement in the form of an axial stroke of the piston (1) via the second sleeve (B) transmits and presses in the direction of reference to the spring / spring assembly (12).

6. Actuator according to one of claims 1 to 5, characterized by the rotation of the planet carrier in combination with the spring assembly (12), which axially allows a reference point, a position determination by means of a rotary encoder of the electric motor (E) or the spindle ( 2) is feasible.

7. Actuator according to one of claims 1 to 6, characterized in that the position of the clutch on the characteristic curve by means of a plausibility check can be determined.

8. Actuator according to one of claims 1 to 7, characterized in that the spindle (2) has a pitch 0 and is combined with an angle sensor for an angle / position sensor which is rotationally connected to the rotor of a driving electric motor (E) ,

9. Actuator according to one of claims 1 to 8, characterized in that the first sleeve (A) is formed in two parts and that the two parts of the first sleeve (A) via one, this surrounding clamp (7) are interconnected and that the second sleeve (B) axially and rotationally fixed to the first sleeve (A) is connected and that the second sleeve (B) at its outer diameter has a longitudinal toothing which is in engagement with a spline on the inner contour of the housing (8), in such that the second sleeve (B) is rotatably and axially displaceably received in the housing (8).

10. Actuator according to one of claims 1 to 9, characterized in that the second sleeve (B) with the piston (1) is rotatably connected.