Screw nut of a ball screw mechanism, and process for manufacturing a screw nut

Abstract

A screw nut (1) of a ball screw mechanism comprises a main nut part (5) which is made of steel and into which a deflection element (3) in the form of a sheet metal piece for individually deflecting rolling elements is inserted from inside. The deflection element (3) has a deflection channel (7) that is entirely grooved and is open inwards, i.e. in the direction of the screw nut of the ball screw mechanism, over its entire length.

Description

[0001] Spindle nut of a ball screw drive and method for producing a spindle nut

[0002] The invention relates to a spindle nut intended for use in a ball screw drive, having the features of the preamble of claim 1. Furthermore, the invention relates to a method for producing a spindle nut for a ball screw drive.

[0003] A spindle nut of this type is known from DE 31 00 349 A1. The spindle nut, referred to in this case as a bearing nut, has a deflection recess in the material of the nut. A deflection insert made of sheet metal is inserted into the deflection recess. The deflection insert has a pair of opposing deflection fingers that are bent towards and immersed in the spindle raceway. The fingers are connected to each other by a so-called insert section, which forms a cover. Within a fully assembled ball screw drive, which comprises the bearing nut, a threaded spindle, and rolling elements (namely balls) rolling between the bearing nut and the threaded spindle, the rolling elements are guided outside the cover in the deflection area. In this way, any contact between the rolling elements and the threaded spindle is excluded in the deflection area.

[0004] Another ball screw nut, i.e., a spindle nut with a single deflection, intended for use in a ball screw drive is known, for example, from DE 10 2014 221 135 B3. In this case, the spindle nut comprises a tubular sheet metal part that defines a load section of a thread profile. A ball return piece is inserted into this tubular sheet metal part, which forms a deflection section and is also designed as a sheet metal part.

[0005] The invention is based on the object of further developing components of ball screws compared to the state of the art, whereby a particularly favorable ratio between manufacturing effort and long-term load capacity is sought, even under operationally increased temperature influences.

[0006] This object is achieved according to the invention by a spindle nut having the features of claim 1. The object is also achieved by a method for producing a spindle nut according to claim 8.

[0007] The spindle nut according to the application comprises, in a known basic design, a nut base body into which a deflection element, designed as a sheet metal part, is inserted from the inside for the individual deflection of the rolling elements. According to claim 1, the deflection element provided for the individual deflection of the rolling elements has a continuous groove-shaped deflection channel that is open inward over its entire length, i.e., toward the threaded spindle of the ball screw drive.

[0008] In contrast to the ball redirection concept described in DE 31 00 349 A1, the inwardly open design of the redirection channel implies that there is no separating element between the balls and the threaded spindle in the redirection area. This enables a particularly space-saving design of the spindle nut in the radial direction of the ball screw drive.

[0009] Compared to conventional plastic deflection pieces, manufacturing the deflection element from sheet metal allows the ball screw drive to operate at significantly higher temperatures. This is relevant, for example, when using the spindle nut in a lead screw drive of an electromechanical actuator, such as a brake or steering actuator.

[0010] With regard to the fastening of the deflection element in the base body of the spindle nut, a wide variety of fastening technologies are conceivable, such as screw connections or material-to-material connections, although any external fastening is fundamentally unnecessary. In a particularly efficient manner, the deflection element, designed as a sheet metal part, can be held in the nut base body by clamping. In this case, the clamping can be achieved by a pair of tabs on the deflection element, which support the deflection element on the nut base body, particularly in the axial direction of the ball screw drive. Optionally, the tabs provided for establishing the clamping connection each have a clamping bead that contacts the nut base body. The clamping bead represents a raised area and / or depression in the otherwise flat tab.The tabs can contact either a smooth or a three-dimensionally structured surface of a recess formed in the nut base body, into which the deflection element is inserted. In a modified embodiment, the deflection element is held in a pocket of the nut base body, i.e., a deflection pocket, in addition to being clamped via an undercut.

[0011] According to one possible embodiment, the deflection element has two support strips, each intersected by the deflection channel and supported on the nut base body. The support strips thus provide outward support for the one-piece, sheet metal deflection element. Depending on the radial clearance between the threaded spindle and the spindle nut, the support strips can either rest on non-machined sections of the thread structure of the nut base body or be located in recessed sections corresponding to the wall thickness of the sheet metal deflection element. In the latter case, the edges of the support strips, in conjunction with the contours of the recess in the nut base body, can be used additionally to position the deflection element in the nut base body.

[0012] Regardless of the exact shape of the recess into which the deflection element is inserted, one long side of each support strip can extend to one end of the deflection channel formed by the deflection element. The support strips are essentially aligned in the longitudinal direction of the spindle nut. A tongue engaging in a thread of the nut base body, acting as a positive-locking contour and not intended for contacting rolling elements, can be formed onto one of the two support strips or onto each support strip. Together with the aforementioned tabs, optionally including clamping beads, and the support strips supported on the thread of the spindle nut, this provides positive support for the deflection element in multiple directions.

[0013] The method according to the application for producing a spindle nut for a ball screw drive with individual deflection generally provides that a recess is made in 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 for the individual deflection of rolling elements, i.e. balls, is inserted into the recess, and wherein the said metallic deflection element has a continuous groove-shaped deflection channel which is open inwards over its entire length.

[0014] The recess in the nut base body intended to accommodate the deflection element can be produced, in particular, by machining. In principle, both primary forming and forming processes can be considered for the production of the nut base body. The material from which the nut base body is made does not necessarily match the material from which the deflection element is made. Since the deflection element does not form part of the load section of the ball channel of the ball screw, metallic materials in particular can be considered for the production of the deflection element. These materials are characterized by good formability, for example, by deep drawing, but have a lower mechanical load-bearing capacity than the steel from which the nut base body is made.

[0015] There are no theoretical limitations regarding the number of deflection elements within the spindle nut. For example, two, three, four, or more deflection elements can be incorporated into the nut body. In the case of multiple deflection elements, these can be offset from one another within the spindle nut in the circumferential direction of the spindle nut.

[0016] The advantage of the invention lies in particular in the fact that the use of a deflection element designed as a stamped and bent part, which is inserted from the inside into a spindle nut of a ball screw, enables both a space-saving, production-friendly construction of the spindle nut and operation of the ball screw under high loads, including temperature loads.

[0017] Two exemplary embodiments of the invention are explained in more detail below with reference to a drawing. In the drawings:

[0018] Fig. 1 in a sectional perspective view of a spindle nut of a ball screw drive including a deflection element for individual rolling element deflection,

[0019] Fig. 2 to 6 the deflection element of the spindle nut according to Figure 1 in different views,

[0020] Fig. 7 and 8 details of the arrangement according to Figure 1 ,

[0021] Fig. 9 shows a detail of a ball screw drive modified compared to the embodiment according to Fig. 1 in a view analogous to Fig. 7.

[0022] The following explanations refer to both exemplary embodiments, unless otherwise stated. Parts that correspond to one another or have essentially the same function are identified by the same reference numerals in all figures. A spindle nut, identified overall by the reference numeral 1, of a ball screw drive (not shown in detail) is suitable for use in an electromechanical actuator. Balls roll as rolling elements between a thread 2 of the spindle nut 1 and a threaded spindle. During operation of the ball screw drive, either the spindle nut 1 or the threaded spindle can be used as the rotating drive element of the ball screw drive, while the other element functions as the rotationally secured, displaceable output element of the ball screw drive.

[0023] For rolling element return, the spindle nut 1 has an individual rolling element deflection, which is implemented with the aid of at least one deflection element 3. In contrast to the arrangement sketched in Figure 1, the spindle nut 1 can have a plurality of deflection elements 3. The deflection element 3 has the task of lifting balls from one turn of the thread 2 and guiding them into an adjacent turn. The deflection element 3 is a sheet metal part designed as a stamped and bent part, which is inserted from the inside into a recess 4 of a nut base body 5 made of steel. In contrast to the deflection element 3, the nut base body 5, which represents the main component of the spindle nut 1, is designed as a solid, machined metal part. The cylindrical outer peripheral surface of the nut base body 5, designated 6, is not interrupted by the recess 4.

[0024] For the individual deflection of the rolling elements, i.e., balls, the deflection element 3 has a deflection channel 7, which is open inward, i.e., toward the threaded spindle. This means that the balls can contact the threaded spindle when they pass through the deflection channel 7.

[0025] The deflection element 3 has a modified square basic shape in plan view (Figure 6). 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 deflection element 3, the long sides of which are designated 9, are aligned in the axial direction of the spindle nut 1 and thus of the entire ball screw drive. Each support strip 8 is asymmetrically intersected by the deflection channel 7, so that each support strip 8 is formed by a short support section 10 and a separate long support section 11, with the total of four support sections 10, 11 being supported from the inside on the nut base body 5. The ends of the deflection channel 7, designated 12, 13, are thus each located between a short support section 10 and a long support section 11.

[0026] Parallel between the two support strips 8 is a holding section 14, which is also formed by the deflection element 3 and is also intersected by the deflection channel 7. At each end of the holding section 14 there is a tab 15 engaging in the recess 4, oriented in the radial direction of the spindle nut 1, which is structured in the form of a clamping bead 16 that contacts a wall of the recess 14, so that overall a clamping fastening of the deflection element 3 in the recess 4 is provided.

[0027] For correct positioning of the deflection element 3, it further comprises two tongues 17, which engage in different turns of the thread 2. The tongues 17, which represent form-fitting contours, are each formed on a longitudinal side 9 of a support strip 8, with each tongue 7 extending from one of the two long support sections 11.

[0028] The embodiment according to Fig. 9 differs from the embodiment according to Figs. 1 to 8 in that an undercut 20 is formed, by which the deflecting element 3 is held in a form-fitting manner in the recess 4. Here, projections 18 formed by the deflecting element 3 and located on the edges of the tabs 15 engage in recesses 19 in the wall of the recess 4. List of reference symbols

[0029] spindle nut

[0030] thread

[0031] deflection element

[0032] recess

[0033] Mother body

[0034] Outer peripheral surface

[0035] deflection channel

[0036] Support strips

[0037] Long side of the support strip short support section long support section

[0038] End of the deflection channel

[0039] End of the deflection channel

[0040] holding section

[0041] tab

[0042] clamping bead

[0043] Tongue

[0044] projection

[0045] Deepening

[0046] undercut

Claims

Patent claims 1. Spindle nut (1) of a ball screw drive, with a nut base body (5) into which a deflection element (3) designed as a sheet metal part is inserted from the inside for individual rolling element deflection, characterized in that the deflection element (3) provided for individual deflection has a continuously groove-shaped deflection channel (7) which is open inwards over its entire length, that is to say towards the threaded spindle of the ball screw drive.

2. Spindle nut (1) according to claim 1, characterized in that the deflection element (3) designed as a sheet metal part is held by clamping in the nut base body (5).

3. Spindle nut (1) according to claim 2, characterized in that the clamping is effected by a pair of tabs (15) of the deflection element (3), which support the deflection element (3) in the axial direction of the ball screw drive on the nut base body (5).

4. Spindle nut (1) according to claim 3, characterized in that the tabs (15) provided for producing the clamping connection each have a clamping bead (16) contacting the nut base body (5).

5. Spindle nut (1) according to one of claims 1 to 4, characterized in that the deflection element (3) has two support strips (8) each intersected by the deflection channel (7) and supported on the nut base body (5).

6. Spindle nut (1) according to claim 5, characterized in that a longitudinal side (9) of each support strip (8) extends to one end (12, 13) of the deflection channel (7).

7. Spindle nut (1) according to claim 5 or 6, characterized in that a tongue (17) is formed on each support strip (8) which engages in a thread (2) of the nut base body (5), functions as a form-fitting contour and is not intended for contacting rolling elements.

8. Method for producing a spindle nut (1) for a ball screw drive with individual deflection, wherein a recess (4) is introduced into a nut base body (5) from the inside in such a way that the outer circumferential surface (6) of the nut base body (5) remains closed, and wherein (4) a deflection element (3) designed as a sheet metal part is used for the individual deflection of rolling elements, i.e. balls, through which a continuous groove-shaped deflection channel (7) is formed, which is open inwards over its entire length.

9. Method according to claim 8, characterized in that the recess (4) in the nut base body (5) is manufactured by machining.

10. Method according to claim 8 or 9, characterized in that the deflection element (3) is fastened by clamping with an additional undercut (20) in the nut base body (5).

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