Recirculating ball nut, assembly for a ballscrew drive and method for producing a recirculating ball nut

Abstract

A method of manufacturing a recirculating ball nut for a ball screw drive, comprising a base body which includes at least one recirculating ball track, the method comprising the following manufacturing steps: manufacturing the base body by precision forging; and finishing the recirculating ball track by a cutting method subsequent to manufacturing the base body.

Claims

1. A method of manufacturing a recirculating ball nut for a ball screw drive, comprising a base body which includes at least one recirculating ball track, the method comprising the following manufacturing steps: manufacturing the base body by precision forging; and finishing the at least one recirculating ball track by a cutting method subsequent to manufacturing the base body; wherein the at least one recirculating ball track is roughly incorporated into the base body by the precision forging step.

2. The method according to claim 1, wherein the at least one recirculating ball track is milled.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a partly sectional and perspective view of an assembly according to the invention, for a ball screw drive with a recirculating ball nut according to the invention;

(2) FIG. 2 shows a schematic illustration of a power steering with an assembly according to the invention;

(3) FIGS. 3a and 3b show schematic illustrations of various method steps of a method according to the invention for manufacturing a recirculating ball nut according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows an assembly 10 having a recirculating ball nut 12 for a power steering 14 which is partly shown in FIG. 2. In addition to the recirculating ball nut 12, the assembly 10 includes a belt pulley 16 which is connected to the recirculating ball nut 12 so as to be non-rotatable relative thereto.

(5) As can be seen in FIG. 1, the recirculating ball nut 12 includes a substantially cylindrical base body 13. The base body 13 of the recirculating ball nut 12 and also the belt pulley 16 have flanges 18, 20 provided thereon which rest against each other in a longitudinal direction L and are firmly connected with each other in the longitudinal direction L and also in the peripheral direction by means of a plurality of fastening means 22, which are rivets in the embodiment shown here. Provided on the inner surface 24 of the recirculating ball nut 12 is a plurality of recirculating ball tracks 26 formed similar to a thread. A tooth profile 27 is provided on the outside of the belt pulley.

(6) The power steering 14 shown in FIG. 2 includes a steering linkage 28 having a thread 30 that corresponds in terms of orientation and pitch to the recirculating ball tracks 26 of the recirculating ball nut 12. The assembly 10 is mounted for rotation in relation to the steering linkage 28 and held in a thrust-resistant manner in the longitudinal direction L. Provided between the recirculating ball nut 12 and the steering linkage 28 is a plurality of transmission means, in particular balls, which engage in both the recirculating ball tracks 26 and in the thread 30 of the steering linkage 28, as a result of which the recirculating ball nut 12 is coupled to the steering linkage 28.

(7) The belt pulley 16 of the assembly 10 is coupled to a drive 34 of the power steering 14 via a belt 32. When the assembly 10 is rotated by the drive 34, the steering linkage 28 is displaced in the longitudinal direction L by means of the coupling via the balls, as a result of which a steering assist force acts on the steering linkage 28.

(8) In order to ensure a reliable function of the assembly 10 and thus of the power steering 14, it is required for the recirculating ball tracks 26 to be manufactured with a very high precision, so that the transmission means can roll therein with a very low resistance while still featuring as little play as possible.

(9) According to the invention, the recirculating ball nut 12 or the base body 13 of the recirculating ball nut 12 is manufactured in a forging method, in particular a precision forging method (FIG. 3a). Subsequently, the recirculating ball tracks 26 are manufactured or finished by a cutting manufacturing method, for example by milling (FIG. 3b).

(10) This manufacturing method allows the recirculating ball nut 12 to be produced quickly and in a simple fashion. The forging method allows a material-saving manufacture of the base body 13, so that very little material is wasted. Manufacturing the entire base body 13 or the recirculating ball nut 12 by a cutting manufacturing method, on the other hand, would involve a very high material usage. For this reason, this method, which allows very low manufacturing tolerances, is made use of exclusively for manufacturing and/or for finishing those areas of the recirculating ball nut 12 where such precision is necessary, that is, the recirculating ball tracks 26. Applying the cutting manufacturing methods exclusively to the recirculating ball tracks allows a material-saving manufacture of the recirculating ball nut 12.

(11) Instead of a milling method, any other suitable cutting manufacturing method may also be used for manufacturing the recirculating ball tracks 26.

(12) In the embodiment shown here, the assembly 10 has a two-part configuration, with a belt pulley 16 and a recirculating ball nut 12. Depending on the structure of the assembly 10, however, these components may also be formed integrally with each other. In particular, the belt pulley 16 may be part of the base body 13 of the recirculating ball nut 12.

(13) The connection preventing relative rotation between the belt pulley 16 and the recirculating ball nut 12 may also be produced in other ways, for example by a suitable torque transmission profile. In particular, instead of the rivets, bolts or other suitable fastening means 22 may also be used.

(14) In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.