Method for producing threaded nuts for threaded drives, in particular ball screw nuts for ball screw drives

Abstract

This invention relates to a method for producing a threaded nut (1) for a threaded drive, the method comprising the steps of: producing a sleeve (4) from a steel plate suitable for surface hardening; molding a rolling profile (5) for rolling contact with a rolling body on the inner periphery of the sleeve (4), the rolling profile being wound helically around the longitudinal axis of the sleeve (4); welding a flange (7) to an end face of the sleeve (4), the flange (7) having a welding surface (8) on a flange end face opposite to the sleeve (4) for welding to a machine part (2), the welding surface (8) initially having a diffusion inhibition layer (10) that inhibits carbon penetration; and, after surface hardening of the threaded nut (1), exposing the welding surface (10) by removing the diffusion inhibition layer (10). The threaded nut (1) produced according to the method may be part of a ball screw drive, the flange (7) of which may be welded by the user to a provided machine part (2).

Description

Technical Field

[0001] This invention relates to a method for producing threaded nuts for threaded drive devices, particularly ball screw nuts for ball screw drive devices. Background Technology

[0002] For example, the ball screw nut of the ball screw drive according to the features of the preamble of claim 1 is known from DE2829433 A1. The ball screw nut has a sleeve formed of steel plate with ball grooves on its inner periphery, the ball grooves being spirally wound around the axis of the ball screw drive, and the ball grooves being rolled by a forming method. The ball screw nut is hardened.

[0003] Although low-carbon steel sheets are generally unsuitable for heat treatment hardening, they are suitable for machining without cutting. For this reason, such steel sheets are carburized, and lead screw nuts formed from them are surface hardened. In many applications, depending on the application, a fixed connection is required between the lead screw nut and machine parts. Due to the high carbon content or martensitic structure, welding connections are difficult or impossible. Summary of the Invention

[0004] The purpose of this invention is to provide a threaded nut for a threaded drive device that is easy to manufacture and easy to attach to machine parts after hardening.

[0005] According to the invention, this objective is achieved by the irregularly threaded nut according to claim 1. Other suitable embodiments are provided in the dependent claims.

[0006] The method for producing threaded nuts for threaded drives according to the present invention provides the following steps:

[0007] Sleeves are manufactured from steel plates suitable for surface hardening by forming methods. These sleeves can be seamless and can be cut to length from tubing. Steel plates with low carbon content are suitable for non-machining processes.

[0008] A rolling profile for rolling contact with the rolling body is formed on the inner periphery of the sleeve using a forming method. The rolling profile is wound in a helical manner around the longitudinal axis of the sleeve. All common forming methods such as burnishing, high-pressure sheet forming, and oscillation are possible here.

[0009] In the oscillating method, a sleeve is inserted into a die, which is a stationary part of the oscillating press. The oscillating die is set to a rolling motion, under which the material of the sleeve can flow into its new shape and produce a thread as a rolling profile, which spirals around the longitudinal axis of the sleeve. In the case of a ball screw drive, this thread is formed by ball grooves spirally wound around the sleeve.

[0010] The flange is welded to one end face of the sleeve. Easily weldable steel is used as the material for the flange. The flange has a welding surface on its end face facing away from the sleeve for welding to a machine component. Depending on the application, the machine component may be, for example, a piston or a housing. The threaded drive device produced according to the method of the invention allows for simple connection to a machine component by welding the flange, which has its welding surface, to the machine component.

[0011] A particular advantage of the present invention can be seen in the fact that the wall thicknesses of the flange and the sleeve can be quite different. Therefore, both a surface-hardened thin-walled sleeve and a thick-walled flange, suitable for welding to machine parts used in a threaded drive mechanism with the threaded nut, can be provided in an economically advantageous manner. "Thick wall" should be understood as the flange having a thicker wall than the sleeve.

[0012] To further produce threaded nuts, a diffusion-inhibiting layer is applied to the welded surface. Therefore, the supplied threaded nuts are surface-hardened. Surface hardening is a method of hardening a surface (hardening the boundary layer), which includes carburizing, quenching, and tempering the steel workpiece.

[0013] The diffusion inhibition layer inhibits carbon from penetrating into the weld surface of the flange during carburizing.

[0014] The diffusion-inhibiting layer can be applied to the flange before it is welded to the sleeve. For example, one could envision a circular blank with coated end faces being stamped or cut from a flat sheet. The flange and sleeve, thus positioned, are aligned with each other. Welding to the sleeve can be performed using the flange's wall thickness. The diffusion-inhibiting layer on the end face facing away from the sleeve is melted during the welding process. Alternatively, the diffusion-inhibiting layer can be applied to the sleeve after the flange has been welded to it.

[0015] During the carburizing process of threaded nuts, only the areas without a diffusion inhibition layer are carburized. Sleeves do not require a diffusion inhibition layer and can harden both inside and out after surface hardening. This means that after surface hardening is complete, the areas supporting the diffusion inhibition layer remain soft and easy to weld due to the reduced carbon content.

[0016] After surface hardening, the weld surface can be exposed by removing the diffusion inhibition layer. This exposure of the weld surface can be done during the production of the threaded nut; alternatively, exposure can be done when the threaded drive equipped with the threaded nut according to the invention is delivered to the user. In many cases, the user welds the flange to a machine part for a specific application. Prior to this welding, the user can remove the diffusion inhibition layer at least to the extent that the weld surface is exposed.

[0017] For example, if the end face of the flange facing away from the sleeve is completely covered by such a diffusion-inhibiting layer, it is sufficient to expose only the area on the end face intended for welding to machine parts.

[0018] Alternatively, the diffusion inhibition layer can be applied only to the welded portion and removed from the area of ​​the welded surface after surface hardening. This variation reduces the amount of material used.

[0019] Welding to machine parts can be performed independently of the production of the threaded nut, that is, when the threaded nut or the threaded drive including the threaded nut is delivered to the user by the manufacturer of the threaded drive and, for example, installed in the intended application.

[0020] The diffusion inhibition layer can be formed of copper. This layer can be electroplated or plated. The choice of method depends on the shape of the flange or the semi-finished product used to produce the flange.

[0021] The threaded nut may have an outer sleeve, between which a known deflection device for balls continuously circulating in a ball track is provided. The ball track has a load portion and a deflection portion that always connects the beginning and end of the load portion. The load portion is formed by ball grooves in the threaded nut and ball grooves in the threaded spindle, which are helically wound around the spindle axis. In the case of a single deflection, the load portion may be less than one full turn, and in the case of an external deflection, the load portion may be formed as several turns. The deflection device may have a plastic sleeve coaxially inserted between the sleeve and the outer sleeve. The aforementioned flange extends between the sleeve and the outer sleeve and is securely connected to the outer sleeve. Attached Figure Description

[0022] The invention will now be described in more detail with reference to exemplary embodiments shown in a total of five figures. In the figures:

[0023] Figure 1 A threaded nut in the form of a ball screw drive is shown in longitudinal section, wherein machine parts are welded to the threaded nut.

[0024] Figure 2 It shows Figure 1Magnified details

[0025] Figure 3 Shown with magnified details Figure 2 Variations in, and

[0026] Figure 4 It shows that it has the following characteristics: Figure 1 The ball screw drive device with threaded nuts, and

[0027] Figure 5 It shows Figure 4 Zoomed-in details.

[0028] In all the accompanying drawings, the threaded nut of the screw drive according to the invention is shown in the form of a ball screw nut of a ball screw drive. Detailed Implementation

[0029] Figure 1 A threaded nut 1 of a threaded drive device is shown in longitudinal section, to which a machine component 2 is welded. The threaded nut 1 is designed as a ball screw nut 3. The ball screw nut 3 has a sleeve 4 made of steel plate, on the inner periphery of which an uncut rolling profile 5 is constructed for rolling contact with a rolling element (not shown). The rolling profile 5 is designed as a ball groove 6, which is helically wound around the longitudinal axis, and a rolling element formed of balls (not shown) can roll on this ball groove.

[0030] The sleeve 4 is provided with a welding flange 7 at one axial end, which has a welding surface 8 on its end face opposite to the sleeve 4 for welding to the machine part 2. In addition, a weld 16 penetrating the wall thickness of the flange 7 can be observed, which connects the flange 7 to the sleeve 4 by material bonding.

[0031] Figure 2 The cross-section of flange 7 is shown in magnified detail. The weld 9 connecting machine part 2 to flange 7 is clearly visible. On the end face of flange 7 facing machine part 2, flange 7 is provided with a diffusion inhibition layer 10, which is removed only in the area of ​​weld surface 8 to ensure a problem-free material bond between flange 7 and machine part 2.

[0032] During surface hardening, the threaded nut 1 is carburized. Carbon diffusion into the weld surface 8 is prevented by a diffusion inhibition layer 10, which in this embodiment is formed of copper.

[0033] Figure 2The surface-hardened layer 11 of the sleeve 4 and the surface-hardened layer 12 of the flange 7 are shown, highlighted here by means of thicker lines. These surface-hardened layers 11 and 12 are the result of surface hardening performed after the flange 7 is welded to the sleeve 4 and before the flange 7 is welded to the machine part 2. The ball groove 6 is surface-hardened.

[0034] exist Figure 2 As clearly shown, surface hardening layers 11 and 12 are not formed on the end face of flange 7 facing machine component 2. After surface hardening of threaded nut 1, diffusion inhibition layer 10 is removed only in the area of ​​weld surface 9, thus exposing the weld surface.

[0035] according to Figure 3 The only difference between this exemplary embodiment and the previously described exemplary embodiment is that the diffusion inhibition layer on the end face of the flange 7 facing the machine component 2 has been completely removed before the threaded nut 1 is welded to the machine component 2.

[0036] Figure 4 and Figure 5 A ball screw drive is shown, comprising a threaded nut 1 designed as a ball screw nut 3. The threaded nut 1 has an outer sleeve 17, and a known deflection device 18 for balls continuously circulating in a ball track 19 is provided between the outer sleeve and a sleeve 4. The ball track 19 has a load portion 20 and a deflection portion 21 that always connects the start and end portions of the load portion 20 together. The load portion 20 is formed by ball grooves 14 of the threaded nut 1 and ball grooves 22 of the threaded spindle 23, which are helically wound around the spindle axis. In an exemplary embodiment, the threaded spindle 23 is rotated. In this exemplary embodiment, the load portion 20 extends several turns. The deflection device 18 has a plastic sleeve 24 coaxially inserted between the sleeve 4 and the outer sleeve 17. The flange 7 extends radially between the sleeve 4 and the outer sleeve 17 and is securely connected to the outer sleeve 17.

[0037] List of reference numerals

[0038] 1. Threaded nut 2. Machine part 3. Ball screw nut 4. Sleeve 5. Rolling profile 6. Ball groove 7. Flange 8. Welded surface 9. Weld 10. Layer 11. Surface hardening layer 12. Surface hardening layer 13. Threaded spindle 14. Ball groove 15. Ball 16. Weld 17. Outer sleeve 18. Deflection device 19. Ball track 20. Load part 21. Deflection part 22. Ball groove 23. Threaded spindle 24. Plastic sleeve.

Claims

1. A method for producing a threaded nut (1) for a threaded drive device, the method comprising the following steps: • The sleeve (4) is made of steel plate suitable for surface hardening. • A rolling profile (5) for rolling contact with the rolling body is molded on the inner periphery of the sleeve (4), the rolling profile being wound helically around the longitudinal axis of the sleeve (4). • Weld the flange (7) to the end face of the sleeve (4). • The flange (7) has a welding surface (8) on its flange end face away from the sleeve (4) for welding to the machine part (2). The welding surface (8) initially has a diffusion inhibition layer (10) that inhibits carbon penetration into the welding surface (8). • The threaded nut (1) is surface hardened, and after the surface hardening of the threaded nut (1), the welding surface (8) is exposed by removing the diffusion inhibition layer (10).

2. The method according to claim 1, wherein, After being welded to the sleeve (4) and before the surface of the threaded nut (1) is hardened, the flange (7) is provided with the diffusion inhibition layer (10) on the end face away from the sleeve (4), and the diffusion inhibition layer is removed at least in the area of ​​the welded surface (8) after the surface is hardened.

3. The method according to claim 1 or 2, wherein, The diffusion inhibition layer is formed of copper.

4. The method according to claim 1 or 2, wherein, The diffusion inhibition layer is plated.

5. The method according to claim 1 or 2, wherein, The diffusion inhibition layer is electroplated.

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