BALL SCREW NUT

Abstract

A ball screw nut having a tubular sheet metal body with a thread profile and being optionally encapsulated in plastic. This sheet metal body is formed of a sheet metal part that includes the thread profile and a ball-returning piece inserted therein, which is designed as an additional sheet metal part.

Claims

1. A ball screw nut for a ball screw drive comprising a tubular sheet-metal part that has a thread profile that forms a load section, and a ball return piece forming a deflection section, the ball return piece is constructed as a sheet-metal part that is inserted and fixed in a recess of the tubular sheet-metal part and is open toward a spindle of the ball screw drive.

2. The ball screw nut according to claim 1, wherein the thread profile has a single winding.

3. The ball screw nut according to claim 2, wherein the ball return piece is inserted into a rectangular recess of the tubular sheet-metal part having the thread profile.

4. The ball screw nut according to claim 1, wherein the tubular sheet-metal part having the thread profile is constructed as a seamless tube.

5. The ball screw nut according to claim 1, further comprising a support structure made from plastic that surrounds the tubular sheet-metal part having the thread profile.

6. A method for producing a ball screw nut for a ball screw drive, comprising the following steps: providing a tubular sheet-metal part having a thread profile, generating a recess in the tubular sheet-metal part by internal stamping, inserting a ball return piece made from sheet metal into the recess such that the ball return piece is open toward a spindle of the ball screw drive.

7. The method according to claim 6, wherein the ball return piece is fixed in the tubular sheet-metal part having the thread profile by welding.

8. The method according to claim 6, wherein the ball return piece is fixed in the tubular sheet-metal part having the thread profile by clinching.

9. The method according to claim 6, further comprising encapsulating the tubular sheet-metal part with plastic after insertion of the ball return piece.

10. The method according to claim 6, wherein the tubular sheet-metal part is produced by cutting to length a tube profiled into a thread shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] An embodiment of the invention is explained in more detail below with reference to a drawing. Shown herein are:

[0020] FIG. 1 a sheet-metal body of a ball screw nut in an exploded view,

[0021] FIG. 2 the arrangement according to FIG. 1 in a section view,

[0022] FIGS. 3 to 6 different views of the sheet-metal body of the ball screw nut, and

[0023] FIG. 7 the ball screw nut including support structure made from plastic.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] A ball screw nut marked overall with the reference symbol 1 is provided for use in a ball screw drive. For its basic function, refer to the prior art cited above. A spindle interacting with the ball screw nut 1 and rolling bodies, namely balls, which roll between the ball screw nut 1 and the spindle, are not shown in the figures.

[0025] The ball screw nut 1 is formed as a composite part made from a sleeve-shaped sheet-metal body 2 and a plastic support structure 3 that surrounds the sheet-metal body 2 and is generated with an injection molding process. The complete ball screw nut 1, including the plastic support structure 3, is shown in FIG. 7. The support structure 3 is connected to the sheet-metal body 2 such that forces and torques can be transferred between the support structure 3 and the sheet-metal body 2. On the cylindrical outer circumference of the support structure 3 there can be a not-shown toothing arrangement that enables a drive of the ball screw nut 1 by a belt. The ball screw nut 1 can also be provided for driving by gearwheels or for direct, that is, gear-less, driving by an electromotor.

[0026] In FIGS. 1 to 6, only the sheet-metal body 2 of the ball screw nut 1 is shown, wherein FIG. 5 shows the section A-A (FIG. 4). Even with non-encapsulated sheet-metal bodies 2, together with balls as roller bodies and a spindle, a fully functional ball screw drive can be produced, especially for applications with low forces.

[0027] For the production of the sheet-metal body 2, the process starts with a smooth, cylindrical sleeve made from steel sheet. The sleeve is used in the illustrated embodiment for the production of a single sleeve-shaped sheet-metal part designated with 4. Alternatively, the process can start with a tube from which a plurality of sleeve-shaped sheet-metal parts 4 is produced. In both cases, the sleeve or the tube is profiled by non-cutting shaping processes such that a thread profile 5 is created that forms a raceway for the rolling bodies of the ball screw drive. The thread profile 5 can be shaped, in particular, by a roller tool.

[0028] Deviating from the construction shown in the figures, the thread profile 5 can reach up to the end sides of the essentially cylindrical sheet-metal part 4. This applies, in particular, for cases in which a plurality of sheet-metal parts 4 are produced by dividing a longer tube in which a continuous thread profile 5 is impressed.

[0029] The thread profile 5 provided in the sheet-metal part 4 for the rolling bodies of the ball screw drive extends once around the circumference of the sheet-metal part 4, that is, describes a single winding 6 that forms a load section of the ball screw drive. In the circumferential area where the beginning and end of the winding 6 lie, a recess 7 is formed in the sheet-metal part 4 by internal stamping. The recess 7 has an elongated, rectangular shape, wherein its narrow sides lie close to the end sides of the sheet-metal part 4. Between the recess 7 and the two end sides of the sheet-metal part 4 there are connecting pieces 8 that provide for sufficient stability of the sheet-metal part 4 during the production process.

[0030] In the recess 7, a ball return piece 9 is inserted, which is shown raised from the sheet-metal part 4 in FIGS. 1 and 2. The ball return piece 9 is not the piece of sheet metal that was stamped out from the sheet-metal part 4 during the production of the recess 7. The thickness of the ball return piece 9 which is a steel sheet-metal part just like the sheet-metal part 4 is not necessarily identical to the thickness of the sleeve-shaped sheet-metal part 4. In particular, the ball return piece 9 that connects the start and end of the load section 6 and is exposed to less strong mechanical loads through the balls of the ball screw drive than the sheet-metal part 4 can have a smaller thickness than the sleeve-shaped sheet-metal part 4.

[0031] Towards the spindle of the ball screw drive, the ball return piece 9 is open. Through a slight pressure, the ball return piece 9 is fixed in the recess 7 of the sheet-metal part 4. Optionally, a more secure connection between the ball return piece 9 and the sheet-metal part 4 is produced by clinching or a spot-weld connection. Within the profiled section of the sheet-metal body 2 assembled from the sleeve-shaped sheet-metal part 4 and the ball return piece 9 in the ball screw nut 1, a deflection section designated with 10 is formed only by the ball return piece 9.

[0032] After the ball return piece 7 is mounted on the sheet-metal part 4, the sheet-metal body 2 completed in this way is encapsulated as a whole with the support structure 3 made from plastic so that the final ball screw nut 1, as shown in FIG. 7, is produced. The shrinkage of the plastic as it cools down creates, beyond the given positive-fit connection, a permanently tight connection between the support structure 3 and the sheet-metal body 2 of the ball screw nut 1. The support structure 3 contributes significantly to the stability of the entire ball screw nut 1.

LIST OF REFERENCE NUMBERS

[0033] 1 Ball screw nut [0034] 2 Sheet-metal body [0035] 3 Support structure [0036] 4 Sheet-metal part [0037] 5 Thread profile [0038] 6 Winding, load section [0039] 7 Recess [0040] 8 Connecting piece [0041] 9 Ball return piece [0042] 10 Deflection section