Spindle nut of a ball screw drive and method for manufacturing a spindle nut

Abstract

A spindle nut (1) of a ball screw drive comprises a nut body (5) made of steel, in which a deflection element (3) designed as a sheet metal part is inserted for the individual deflection of the rolling elements from the inside. The deflection element (3) has a continuous, channel-shaped deflection channel (7) that is open inwards along its entire length, i.e. towards the threaded spindle of the ball screw drive.

Description

The invention relates to a spindle nut provided for use in a ball screw having the features of the preamble of claim 1.A spindle nut of the generic type is known from DE 31 00 349 A1. The spindle nut, which is referred to in this case as a bearing nut, has a deflection depression in the material of the nut. A deflecting insert made of sheet metal is inserted into the deflecting depression. The deflecting insert has a pair of deflecting fingers which are opposite one another and are bent away from the spindle track and enter the latter. The fingers are connected to one another by a so-called insert part which forms a cover. Within a completely assembled ball screw, which comprises the bearing nut, a threaded spindle, and rolling bodies, namely balls, rolling between the bearing nut and the threaded spindle, the rolling bodies are guided outside the cover in the deflection region. In this way, any contact between the rolling bodies and the threaded spindle is excluded in the deflection region.A further ball screw nut intended for use in a ball screw drive, i.e. a spindle nut, with individual deflection is known, for example, from DE 10 2014 221 135 B3. In this case, the spindle nut comprises a tubular sheet metal part which describes a load section of a threaded profile. Inserted into this tubular sheet metal part is a ball return piece, which forms a deflection section and is likewise designed as a sheet metal part.The invention is based on the object of further developing components of ball screws compared to the stand, wherein a particularly favorable ratio between production outlay and long-term load-bearing capacity, even under elevated temperature exposure caused by operation, is sought.This object is achieved according to the invention by a spindle nut having the features of claim 1.The spindle nut according to the application comprises, in a basic concept known per se, a nut base body into which a deflecting element, which is designed as a sheet metal part, is inserted from the inside for individual deflection of the rolling body. According to claim 1, the deflecting element provided for the individual deflection of the rolling bodies has a continuously channel-shaped deflecting channel which is open inwardly over its entire length, that is to say towards the threaded spindle of the ball screw.In contrast to the concept of ball deflection described in DE 31 00 349 A1, i.e. ball return, the inwardly open design of the deflection channel implies that no separating element is present between the balls and the threaded spindle in the deflection region. This enables a particularly space-saving construction of the spindle nut in the radial direction of the ball screw.Compared to conventional plastic deflection pieces, the production of the deflection element from sheet metal allows operation of the ball screw at significantly higher temperatures. This is relevant, for example, when using the spindle nut in a screw drive of an electromechanical actuator, for example in a brake or steering actuator.As regards the fastening of the deflecting element in the main body of the spindle nut, a wide variety of fastening technologies are conceivable, for example screw connections or material connections, wherein any fastening from the outside is not necessary for reasons of principle.In a particularly rational manner, the deflecting element, which is designed as a sheet metal part, can be held in the nut base body by clamping. In this case, the clamping can be effected by a pair of brackets of the deflecting element, which support the deflecting element on the nut base body, in particular in the axial direction of the ball screw. Optionally, the lugs provided for producing the clamping connection each have a clamping bead contacting the nut base body. The clamping bead represents an elevation and / or depression in the otherwise planar tab. The lugs can contact either a smooth or a three-dimensionally structured surface of a recess formed in the nut base body, into which recess the deflecting element is inserted. In a modified embodiment, the deflecting element is held in addition to clamping via an undercut in a pocket of the nut base body, that is to say in a deflecting pocket.According to one possible embodiment, the deflecting element has two bearing strips which are cut through in each case by the deflecting channel and are supported on the nut base body. The one-piece deflecting element made of sheet metal is thus supported to the outside by the support strips. Depending on how much free space exists between the threaded spindle and the spindle nut in the radial direction, the bearing strips can either rest on sections of the threaded structure of the nut base body that have not been processed separately or lie in sections that are recessed corresponding to the wall thickness of the deflecting element made of sheet metal. In the latter case, edges of the bearing strips can be used in cooperation with contours of the depression of the nut base body in addition to the positioning of the deflecting element in the nut base body.Regardless of the exact shape of the recess into which the deflecting element is inserted, a longitudinal side of each support strip can extend as far as one end of the deflecting channel formed by the deflecting element. The bearing strips are aligned substantially in the longitudinal direction of the spindle nut.On one of the two bearing strips or on each bearing strip, a tongue, which engages in a thread turn of the nut base body and functions as a positive-locking contour and is not provided for contacting rolling bodies, can be formed. Together with the already mentioned brackets, optionally together with clamping beads, and the bearing strips supported on the thread of the spindle nut, a form-fit support of the deflecting element in several directions is thus provided.The method according to the invention for producing a spindle nut for a ball screw with individual deflection generally provides that a recess is introduced into a nut base body from the inside in such a way that the outer circumferential surface of the nut base body remains closed, wherein a deflection element designed as a sheet metal part is inserted into the recess for the individual deflection of rolling bodies, i.e. balls, and wherein the mentioned metallic deflection element has a deflection channel which is continuous in the form of a trough and is open inwards over its entire length.The recess provided for receiving the deflecting element in the nut base body can be produced in particular by machining. In principle, also forming and forming methods are possible for the production of the nut base body. The material from which the nut base body is manufactured does not necessarily correspond to the material from which the deflecting element is manufactured. Since the deflecting element does not form part of the load section of the ball channel of the ball screw, metallic materials in particular are suitable for the production of the deflecting element, which materials are distinguished by good deformability, for example by deep drawing, but have a lower mechanical load capacity than the steel from which the nut base body is produced.As for the number of the deflectors within the spindle nut, there are no theoretical limitations. For example, two, three, four or more deflecting elements can be inserted into the nut base body. In the case of a plurality of deflecting elements, these can be offset with respect to one another within the spindle nut in the circumferential direction of the spindle nut.The advantage of the invention lies in particular in the fact that, by using a deflection element which is designed as a stamped and bent part and is inserted from the inside into a spindle nut of a ball screw, both a space-saving, production-friendly construction of the spindle nut and operation of the ball screw under high loads, including temperature loads, are possible.Two exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Shown herein are: FIG. 1 shows a sectional perspective view of a spindle nut of a ball screw drive including a deflection element for individual deflection of the rolling body, FIGS. 2 to 6 show the deflecting element of the spindle nut according to FIG. 1 in different views, FIGS. 7 and 8 show details of the arrangement according to FIG. 1, FIG. 9 shows a detail of a ball screw modified in comparison with the exemplary embodiment according to FIG. 1 in a view analogous to FIG. 7.Unless stated otherwise, the following explanations relate to both exemplary embodiments. Parts corresponding to one another or having the same effect in principle are identified by the same reference numerals in all figures.A spindle nut, denoted overall by the reference symbol 1, of a ball screw drive, not shown in any more detail, is suitable for use in an electromechanical actuator. Between a thread 2 of the spindle nut 1 and a threaded spindle, balls roll off as rolling bodies. During operation of the ball screw, either the spindle nut 1 or the threaded spindle can be used as a rotating drive element of the ball screw, while the respective other element functions as a rotationally secured displaceable output element of the ball screw.For the return of the rolling elements, the spindle nut 1 has an individual deflection of the rolling elements, which is realized with the aid of at least one deflection element 3. In contrast to the arrangement outlined in FIG. 1, the spindle nut 1 can have a plurality of deflection elements 3. The deflecting element 3 has the task of lifting balls out of one winding of the thread turn 2 and introducing them into an adjacent winding. The deflecting element 3 is a sheet metal part which is designed as a stamped and bent part and which is inserted from the inside into a recess 4 of a nut base body 5 made of steel. In contrast to the deflecting element 3, the nut base body 5, which represents the main component of the spindle nut 1, is designed as a solid, chip-removingly machined metal part. The cylindrical outer circumferential surface of the nut base body 5, designated 6, is not interrupted by the recess 4.For the individual deflection of the rolling bodies, i.e. balls, the deflection element 3 has a deflection channel 7 which is open towards the inside, i.e. towards the threaded spindle. This means that the balls, when passing the deflection channel 7, can contact the threaded spindle.The deflecting element 3 has a modified square basic shape in plan view (FIG. 6 ). In this case, the deflection channel 7 approximately represents a diagonal of the square described by the deflection element 3. Two mutually parallel support strips 8 formed by the deflecting element 3, the longitudinal sides of which are denoted by 9, are aligned in the axial direction of the spindle nut 1 and thus of the entire ball screw. Each support strip 8 is asymmetrically cut through by the deflection channel 7, so that each support strip 8 is formed by a short support section 10 and a long support section 11 separate therefrom, wherein the total of four support sections 10, 11 are supported from the inside on the nut base body 5. The ends of the deflection duct 7 denoted by 12, 13 are thus located in each case between a short support section 10 and a long support section 11.Parallel between the two support strips 8 is a holding section 14, which is likewise formed by the deflecting element 3 and which is likewise cut through by the deflecting channel 7. At each of the two ends of the holding section 14 there is a tab 15 which engages in the recess 4 and is aligned in the radial direction of the spindle nut 1 and is structured in the form of a clamping bead 16 which contacts a wall of the recess 14, so that overall a clamping fastening of the deflecting element 3 in the recess 4 is provided.For the correct positioning of the deflecting element 3, the latter also has two tongues 17 which engage in different turns of the thread 2. The tongues 17, which represent positive-locking contours, are each formed on a longitudinal side 9 of a support strip 8, wherein each tongue 7 extends from one of the two long support sections 11.The embodiment according to FIG. 9 differs from the embodiment according to FIGS. 1 to 8 in that an undercut 20 is formed, by means of which the deflecting element 3 is held in the recess 4 in a positive-locking manner. Projections 18 formed by the deflecting element 3 and located at the edges of the lugs 15 engage in depressions 19 in the wall of the recess 4.List of reference characters1 Spindle nut 2 Thread 3 Deflecting element 4 Recess 5 Nut base body 6 Outer circumferential surface 7 Deflecting channel 8 Bearing strip 9 Longitudinal side of the bearing strip 10 Short bearing section 11 Long bearing section 12 End of the deflecting channel 13 End of the deflecting channel 14 Holding section 15 Tab 16 Clamping bead 17 Tongue 18 Protrusion 19 Depression 20 UndercutReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 31 00 349 A1 [0002, 0007]DE 10 2014 221 135 B3

[0003]

Claims

Spindle nut (1) of a ball screw, having a nut base body (5) into which a deflecting element (3) designed as a sheet metal part is inserted for individual deflection of the rolling body from the inside, characterized in that the deflecting element (3) provided for individual deflection has a deflection channel (7) which is continuous in the form of a trough and is open towards the inside over its entire length, that is to say towards the threaded spindle of the ball screw.Spindle nut (1) according to Claim 1, characterized in that the deflecting element (3) designed as a sheet metal part is held in the nut base body (5) by clamping.Spindle nut (1) according to Claim 2, characterized in that the clamping is effected by a pair of brackets (15) of the deflecting element (3), which support the deflecting element (3) on the nut base body (5) in the axial direction of the ball screw.Spindle nut (1) according to Claim 3, characterized in that the lugs (15) provided for producing the clamping connection each have a clamping bead (16) which makes contact with the nut base body (5).Spindle nut (1) according to one of Claims 1 to 4, characterized in that the deflecting element (3) has two bearing strips (8) which are each cut through by the deflecting channel (7) and are supported on the nut base body (5).Spindle nut (1) according to claim 5, characterised in that a longitudinal side (9) of each support strip (8) extends as far as an end (12, 13) of the deflection channel (7).Spindle nut (1) according to claim 5 or 6, characterised in that a tongue (17), which engages in a thread turn (2) of the nut base body (5) and functions as a positive-locking contour and is not provided for contacting rolling bodies, is integrally formed on each bearing strip (8).Method for producing a spindle nut (1) for a ball screw with individual deflection, wherein a recess (4) is introduced from the inside into a nut base body (5) in such a way that the outer circumferential surface (6) of the nut base body (5) remains closed, and wherein a deflection element (3) designed as a sheet metal part is inserted into the recess (4) for the individual deflection of rolling bodies, that is to say balls, by means of which a deflection channel (7) which is continuous in a trough shape and is open inwards over its entire length is formed.Method according to Claim 8, characterized in that the recess (4) in the nut base body (5) is produced by machining.Method according to claim 8 or 9, characterised in that the deflecting element (3) is fastened in the nut base body (5) by clamping with additional undercut (20).

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