WO2019015710A1

WO2019015710A1 - Threaded nut for a ball screw drive

Info

Publication number: WO2019015710A1
Application number: PCT/DE2018/100549
Authority: WO
Inventors: Stefan Michaloudis; Stephan Ruffershöfer; Dieter Adler; Armin Gerner; Jürgen Engel
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2017-07-19
Filing date: 2018-06-11
Publication date: 2019-01-24
Also published as: DE102017116255A1

Abstract

The invention relates to a threaded nut for a ball screw drive, said threaded nut comprising a nut main body (2) having a thread (3), and a multi-part outer deflection means (9) for returning balls via a deflection channel (14) into the thread (13), wherein, at each transition between the thread (3) and the deflection channel (14), a ball-guiding sleeve (5) which is inserted into a bore (13) in the nut main body (2) is connected fixedly to the nut main body (2), and wherein, in addition to the ball-guiding sleeve (5), a deflection base (11) which delimits the deflection channel (14) radially on the inside engages at least partially in the bore (13).

Description

Threaded nut for a ball screw drive

The invention relates to a suitable for a ball screw nut with an external deflection for ball recirculation. Furthermore, the invention relates to a method for producing a threaded nut.

A ball screw generally comprises a threaded spindle, a threaded nut, as well as between the threaded spindle and the threaded nut rolling rolling elements, namely balls. If a ball screw has a ball return, then the setting range of the ball screw is in principle not limited. This applies to a catchy as well as a multi-speed ball screw.

A ball return can be designed either as a single deflection, front deflection or as external deflection. The outer deflection claimed in comparison to the individual deflection more space in the radial direction, but has the advantage that the balls can be promoted over several turns away in the thread of the ball screw back, which is associated with a broader load-bearing area of the ball screw.

Various designs of threaded nuts with external deflection are described, for example, in the documents EP 1 830 106 A1, EP 0 985 851 A1, as well as

DE 10 2009 009 851 A1 discloses. In contrast to the ball screws described in the cited documents, a ball screw disclosed in DE 10 2012 213 856 A1 has a threaded nut inside the wall thickness of which a straight return channel for ball return is arranged. Another design of a ball screw with ball return is in the

DE 73 14 698 U discloses. In this case, balls which are due to the threaded spindle, by a trough-shaped, several turns of a ball race track cross recess guided on the outer circumference of the ball nut, wherein the channel-shaped recess is covered by a roof-shaped bridge. The invention has for its object to further develop a suitable for a ball screw nut relative to the prior art, both under manufacturing aspects and from the point of view of long-term reliability. This object is achieved by a threaded nut with the

Features of claim 1 and by a method for producing a suitable for a ball screw threaded nut according to claim 9. The explained below in connection with the manufacturing method embodiments and advantages apply mutatis mutandis to the threaded nut and the ball screw and vice versa.

The threaded nut has a nut body, which is also referred to as a ball nut. A formed on the inside of the threaded nut thread allows, together with a threaded spindle, the rolling of balls in a load-bearing channel of a ball screw.

Next, the threaded nut on a multi-part outer deflection, through which a deflection channel is formed for the return of balls in the thread. For the discharge of balls from the thread, that is, the load-bearing channel of the ball screw, as well as for the introduction of balls in the load-bearing channel are located in the mother body bores, in each of which a ball sleeve is inserted. Here, a solid, material, positive or non-positive connection between the mother body and each ball sleeve is already made before the nut is completed with other parts.

In addition to the ball sleeve, a deflection base defining the deflection channel radially inwardly engages, at least partially, in the bore located in the nut base body. The deflection base has a middle, preferably curved, the outer contour of the mother body adapted portion and two to the middle section subsequent, pointing in the direction of each bore, pin-shaped sections. A partial engagement of the deflection base in a bore of the nut base body is understood to mean a configuration in which the end face of a peg-shaped section, ie end section, of the deflection base is not arranged with its entire circumference within the bore, but partially in the lateral direction is called radial direction of the bore and the pin-shaped portion, protrudes beyond the bore.

The ball sleeve is preferably formed as a metal sleeve, in particular sheet metal sleeve. Likewise, other materials are suitable for the manufacture of the ball sleeve sleeve, which are harder than those materials through which the deflection of two ball shells connecting each other is formed. Such materials are, for example, ceramic materials or particularly wear-resistant plastics.

Regardless of the material from which the ball sleeve sleeve is made, this preferably has a cylindrical portion and two adjoining these, extending in opposite axial directions of the cylindrical portion, for example, diametrically opposed, formed as lobes noses. One of the lobes is used for the discharge of balls from the load-bearing channel, the other lobe as anti-rotation of the ball sleeve inside the outer deflection.

Overall, the ball sleeve sleeve with respect to an axis which extends transversely to the longitudinal axis of the ball sleeve sleeve, be formed rotationally symmetrical with respect to a rotation of 180 °. This is synonymous with an identical geometry and diametrical arrangement of the two lobes. In a modified embodiment, the two lobes match their shape, but - viewed in the longitudinal direction of the ball sleeve sleeve - offset by an angle deviating from 180 ° to each other. Also in this embodiment, incorrect assembly of the ball sleeve is excluded. Preferably, the ball sleeve is bent as a slotted sleeve made of sheet metal. Alternatively, the ball sleeve may be a non-slotted sleeve. In each embodiment, the high strength of the ball sleeve sleeve is particularly advantageous in the region of the tabs formed on the cylindrical section. In all cases, preferably made of metal, hard ball sleeve sleeve assembly technology is an integral part of the ball nut. This has advantages over solutions in which initially ball sleeve sleeves and a ball return element made of plastic, have significant advantages in terms of manufacturing tolerances to be considered: Due to the tightness of the ball sleeve in the hole located in the mother body bore a tolerance chain is given at this point, which only the bore tolerance of the nut body and the wall thickness tolerance of the ball sleeve sleeve is formed.

The fixed seat of the ball sleeve sleeves in the mother body has the particular advantage that it can come at the ball circulation within the ball screw to any malfunction in the transition between the load channel and the deflection, that is, the ball return channel serving. In addition, the bore in the mother body, in which the ball sleeve is to be used, compared to conceivable designs in which a clearance between ball sleeve and bore exists, be dimensioned smaller, which is associated with increased stability and wear resistance of the ball nut. The deflection base, which is placed as a component of the outer deflection on the ball sleeve sleeves, is preferably made of plastic, wherein the central, curved portion of the deflection base can rest on the lateral surface of the mother body. Likewise, designs are feasible, in which the middle section is lifted completely or partially from the lateral surface of the mother body, wherein the central portion may have an un-curved shape in these cases.

The nut can be produced in the following steps:

A metallic parent body having a plurality of stepped through-holes and on the inside of which at least one thread intended to cooperate with balls and a threaded spindle is provided,

in the stepped bores of the parent body, a ball sleeve made of metal is attached in each case, - At least one two ball sleeve bridging deflection base is placed on the nut body so that it at least partially engages in the through holes, in each of which a ball sleeve is held,

- On the deflection base, a deflection cover is placed to form a Umlenkkanals, which is preferably made as well as the deflection base made of plastic.

Optionally, the entire assembly, which comprises the parent body, the ball sleeves, the deflection base and the deflection cover, is then inserted into a thin-walled outer sleeve in comparison to the parent body. The plug connections which are produced between the ball sleeve sleeves, the deflection base and the deflection cover have, in typical designs of the threaded nut, a lower holding force than the connection between the outer deflection, that is to say the arrangement formed from the deflection base and the deflection cover, and the outer sleeve.

According to a possible embodiment of the threaded nut, at least four ball sleeve sleeves, in particular exactly four ball sleeve sleeves, are rigidly connected to the nut base body, one pair of ball sleeve sleeves being connected to exactly one associated deflection base and the plurality of deflection bases being connected to the deflection channels by a single deflection cover bounded radially outward, are covered. The deflection cover, which completes two deflection bases or a larger number of deflection bases to form a corresponding number of deflection channels, extends for example over the entire in the axial direction

Direction measured length of the mother body. Also, the optional outer sleeve may have a length which corresponds to the length of the mother body. According to a modified design, the deflection cover is formed directly by the outer sleeve.

Irrespective of the presence of a metallic outer sleeve, the respective bores receiving a ball sleeve in the parent body are preferably stepped, tapering towards the central axis of the parent body, the deflection base - or more precisely, one of the peg-shaped sections of the deflection element. base - at least partially engages only in an outer region of the bore, while an inner, compared to the outer region narrower region of the bore for permanently fixed support of the ball sleeve is provided. Here, the outer, larger diameter portion of the bore is preferably - measured in the longitudinal direction of the bore - shorter than the inner, narrower region of the bore.

This means that over most of its length the bore has a small diameter, only sufficient for receiving and holding the ball sleeve, but not a plastic part, which results in a correspondingly low weakening of the ball nut in its interior, the at least one Thread forming area is synonymous. The small compared to the inner, narrowed portion of the bore bore of the outer, further diameter portion of the bore is sufficient for supporting the peg-shaped portion of the deflection base due to the precise, play-free positioning of the ball sleeve in the bore of the ball nut.

The threaded nut can be used for example in a ball screw drive of a brake booster, an electromechanical steering or an electric parking brake. Thanks to the space-saving ball deflection, the threaded nut is generally suitable for applications with limited installation space, even within stationary systems, for example in industrial automation.

An exemplary embodiment of the invention will be explained in greater detail below with reference to a drawing. Herein show:

1 is a perspective view of a nut body of a threaded nut for a ball screw,

FIG. 2 ball sleeve of the threaded nut according to FIG. 1, FIG.

3 shows the threaded nut in a sectional view,

Fig. 4 components of the threaded nut in an exploded view. A designated overall by the reference numeral 1 threaded nut is part of a ball screw, not shown, with respect to its basic function is referred to the cited prior art.

With a threaded spindle per se known design acts a mother body 2 of the threaded nut 1 together. The mother body 2 is also referred to as a threaded nut in the strict sense or as a ball screw nut. The ball screw nut 2 is a solid metal part. On the inner peripheral surface of the ball screw nut 2, a thread 3 is formed, in which balls as

Unroll the rolling elements. The lateral surface of the ball screw nut 2 designated by 4 is substantially cylindrical.

From the lateral surface 4, a total of four ball sleeve sleeves 5 protrude, which constitute transition elements between the nut base body 2 and an outer deflection 9 of the threaded nut 1.

FIG. 2 shows an insulated ball sleeve 5. The ball sleeve 5 is a metal part made of sheet steel. A cylindrical section 6, that is to say the main section, of the ball sleeve 5 is interrupted by a gap 7 running in the longitudinal direction of the ball sleeve 5. At the two end faces of the cylindrical portion 6 close on diametrically opposite sides of the ball sleeve 5 lobes 8, which are aligned in the longitudinal direction of the ball sleeve 5. The two lobes 8 are also referred to as lugs of the ball sleeve 5 and serve in one case the discharge of balls from the thread 3 and in the other case the rotation of the ball sleeve 5 within the outer deflection 9 described in more detail below.

The complete outer deflection 9 is located within an outer sleeve 10 designed as a sheet metal part, which surrounds the parent body 2 concentrically. The outer deflection 9 is constructed in several parts, wherein a made of plastic, channel-shaped deflection base 1 1 is placed directly on the lateral surface 4. The entire outer deflection 9 comprises in the exemplary embodiment, two deflection bases 1 1, which are covered by a single deflection cover 12, the Au the ßenumlenkung 9 completed. The measured in the longitudinal direction of the threaded nut 1 and thus the entire ball screw length of the Umlenkungsdeckels 12 corresponds in the embodiment of the length of the ball screw nut 2 and the length of the outer sleeve 10. Deviating from this, other length relations between the Umlenkungsdeckel 12 and the ball screw nut 2 are conceivable.

Between each deflection base 1 1 and the deflection cover 12, a deflection channel 14 is formed for ball return within the threaded nut 1. In its central region of the deflection channel 14 is curved in the present case in adaptation to the lateral surface 4. Alternatively, a straight design of the central region of the Umlenkkanals 14 is possible. At its two ends of the deflection channel 14 is in each case in a shorter section, which is directed to a bore 13 to. Each bore 13 is a stepped bore, wherein an inner, narrower region of the bore 13 on the inner peripheral surface of the nut body 2, that is in the region of the thread 3, ends, while an outer, expanded portion of the bore 13 in the lateral surface. 4 empties.

The region of larger diameter of the bore 13 has a length designated by a. The length of the inner, tapered region of the bore 13 is designated by b. As is apparent from Fig. 3, the length a is less than the length b. The lengths designated by a, b are to be measured in the longitudinal direction of the bore 13 and thus of the ball sleeve sleeve 5. The diameter of the bore 13 in its inner, tapered portion is dimensioned such that the ball sleeve 5 is fixable therein. The outwardly directed tab 8 of the ball sleeve sleeve 5 protrudes from the tapered portion of the bore 13, wherein it acts in cooperation with the deflection base 1 1 as anti-rotation. The deflection base 1 1 engages partially with its pin-shaped portions in the portion of the bore 13 with an enlarged diameter and contacted with this section, the ball sleeve 5. In the manufacture of the threaded nut 1, the deflection base 1 1 is only then placed on the mother body 2, if the ball sleeve sleeves 5 are already fixed permanently and in a precisely defined position in the mother body 2. The rigid connection between the mother body 2 and the ball sleeve 5 remains even during operation of the ball screw. The links between the diversions kungsbasen 1 1 and the ball sleeve sleeves 5 are designed in the embodiment as connectors. The same applies to the connection between the deflection base 11 and the deflection cover 12. The overall small dimensioned, only a part of their length step-like widened holes 13 allow a small radial distance between the thread 3 and the Außenumlenk- 9 and so that a total of compact and robust construction of the threaded nut 1.

LIST OF REFERENCE NUMBERS

1 threaded nut

2 ball screw nut, nut body

3 thread

4 lateral surface

5 ball sleeve

6 Cylindrical section of the ball sleeve

7 gap of the ball sleeve

8 Nose of the ball sleeve, lobes

9 outside deflection

10 outer sleeve

1 1 deflection base

12 diverter cover

13 hole, stepped

14 Deflection channel a Length of the outer area of the bore 13 b Length of the inner, narrower area of the bore 13

Claims

claims

1 . A threaded nut for a ball screw, with a threaded body (3) having mother body (2), and with a multi-part Außenum- steering (9) for returning balls via a deflection channel (14) in the thread (13), wherein at each transition between the thread (3) and the deflection channel (14) in each case in a bore (13) of the parent body (2) inserted ball sleeve sleeve (5) is fixedly connected to the mother body (2), and wherein in addition to the ball sleeve (5) a deflection channel (14) radially inwardly bounding deflection base (1 1) at least partially engages in the bore (13).

2. threaded nut according to claim 1, characterized in that the ball sleeve sleeve (5) as a metal sleeve, in particular sheet metal sleeve, with a cylindrical portion (6) and two adjoining thereto, in opposite axial directions of the cylindrical portion (6) extending, diametrically opposed Noses (8) is formed.

3. threaded nut according to claim 1 or 2, characterized in that as

Deflection base (1 1) is provided a plastic part contacting a lateral surface (4) of the parent body.

4. threaded nut according to claim 3, characterized in that at least four ball sleeves (5) with the mother body (2) are connected, wherein in each case a pair of ball sleeves (5) with exactly one associated deflection base (1 1) is connected and the plurality of Deflection bases (1 1) by a single deflection cover (12) which limits the deflection channels (14) radially outward, are covered.

5. threaded nut according to claim 4, characterized in that extending the deflection cover (12) over the entire measured in the axial direction length of the mother body (2).

6. threaded nut according to one of claims 1 to 5, characterized in that the outer deflection (9) within a metallic, in comparison to the mother body (2) thin-walled outer sleeve (10).

7. threaded nut according to one of claims 1 to 6, characterized in that each bore (13) in the parent body (2) stepped, tapering towards the central axis of the nut base body (2) is executed, wherein the deflection kung base (1 1) engages only in an outer region of the bore (13), while an inner, narrower region of the bore (13) for holding the ball sleeve (5) is provided.

8. threaded nut according to claim 7, characterized in that the outer, larger diameter portion of the bore (13) has a longitudinal direction of the bore (13) measured length (a) which is less than the length (b) of the inner, narrower area of the bore (13).

9. A method for producing a threaded nut for a ball screw, comprising the following steps:

A mother body (2), on the inside of which at least one thread (3) is formed, is provided,

a number of ball sleeves (5) are fastened in stepped bores (13) of the parent body (2),

- A two ball shells (5) bridging deflection base (1 1) is placed on the mother body (2), wherein at least partially into the bores (13), in each of which a ball sleeve sleeve (5) is held,

- A deflection cover (12) is placed on the deflection base (1 1) to form a deflection channel (14).

10. The method according to claim 9, characterized in that the arrangement, which comprises the parent body (2), the ball sleeve sleeves (5), the deflection base (1 1) and the deflection cover (12), in a comparison with the mother body (2) thin-walled outer sleeve (10) is used.