Patent Application
20240208478
This application claims priority to German Priority Application No. 102022134795.8, filed Dec. 23, 2022, the disclosure of which is incorporated herein by reference in its entirety.
The disclosure relates to a method for producing a gear shaft, for example for an electrically operated brake booster, such as for a brake system of a car. The disclosure also relates to a gear shaft for an electrically operated brake booster and a brake booster for a brake system in a car.
A electromechanical brake booster is known from DE 10 2007 018 469 A1. The known brake booster comprises an electric motor having a rotation/translation conversion gear, which converts a rotating drive movement of the electric motor into a linear movement for actuating a master brake cylinder, and a mechanical gear with a variable transmission ratio,
A method for producing a threaded part of a cylindrical screw drive for an electromechanical brake booster is known from DE 10 2011 081 966 A1.
A further electromechanical brake booster having an electric motor and a rotation/translation conversion gear is known from DE 10 2015 0 12 124 A1.
What is needed is to overcome the disadvantages of the prior art, and to provide a method for producing a gear shaft for an electromechanical brake booster, a gear shaft and an electromechanical brake booster, which enable cost-effective manufacture and usability in different vehicle series with high dimensional accuracy of the components.
According to a first aspect of the disclosure, a method for producing a gear shaft for an electromechanical brake booster having an electric motor and having a rotation/translation conversion gear, which converts a rotating drive movement of the electric motor into a linear movement for actuating a piston-cylinder unit for generating a hydraulic brake pressure, is provided, according to which a force transmission element is provided. A rotationally-symmetrical gearing is integrally formed on a drive-side end of the force transmission element; a positioning and fastening device is formed on the force transmission element at the output side, and a gearwheel is anchored on the force transmission element in a rotationally fixed manner by the positioning and fastening device.
According to one exemplary arrangement, at least a lateral surface of the force transmission element is chemically and/or thermally treated, at least in some portions. In a rotationally symmetrical force transmission element, such as a cylindrical shaft, the term lateral surface refers to the outer circumferential surface of the rotationally symmetrical body. For example, at least the lateral surface of the force transmission element is hardened, for example before the positioning and fastening device is formed. In another variant, the positioning and fastening device is formed and only then is the force transmission element, for example including the positioning and fastening device, chemically and/or thermally treated, for example hardened.
According to one exemplary arrangement, a fastening aid for a bearing and/or a positioning device is formed on the force transmission element. For example, the fastening aid is incorporated by cutting, such as in a turning process. Multiple fastening aids may also be incorporated. A fastening aid may be configured as a narrowing, a recess or a projection, and may, comprise an undercut.
According to one exemplary arrangement, an axial positioning device is formed on the force transmission element such that it is fixed against axial displacement, or—if a fastening aid is provided—it is anchored on the fastening aid. For example, the axial positioning device is brought into form-fitting engagement with the force transmission element.
According to one exemplary arrangement, a lateral surface of the force transmission element is machined by cutting and/or abrasion, at least in some portions, before the gearwheel is anchored in a rotationally fixed manner with respect to the force transmission element. For example, the force transmission element is moved past a grinding tool along its entire length in the direction of the longitudinal extent of the force transmission element. In one exemplary arrangement, the grinding tool is only brought into abrasive contact with the force transmission element in certain regions along its entire length.
According to one exemplary arrangement, the positioning and fastening device is formed, for example, by shaping the force transmission element in a material-preserving manner. The force transmission element may be notched. An impact tool may be used here.
According to one exemplary arrangement, a shaping tool for forming the positioning and fastening device is moved such that the direction in which its shaping force is introduced intersects a direction of extent of the force transmission element which points away from an axis of rotation of the force transmission element. It is thus ensured that a shaping tool, such as an impact tool, shapes material in a predetermined direction, e.g. it generates a material elevation which may serve as an anchoring projection.
According to one exemplary arrangement, the gearwheel and the positioning and fastening device are brought into friction-fitting and/or form-fitting engagement with one another, for example directly, during the pushing-on procedure. Engagement between complementary forms is preferably realized, e.g. as a result of elastic-plastic deformation. In particular, during the pushing-on of the gearwheel, an anchoring recess is formed in the gearwheel, i.e. in a shaft-receiving opening of the gearwheel, by the positioning and fastening device—e.g. a projection or a rib—as a result of elastic-plastic deformation, plastic deformation and/or cutting.
According to one exemplary arrangement, an axial bearing is at least partly formed on an output-side end of the force transmission element. For example, the axial bearing end is produced by cutting, e.g. by turning and/or grinding. The axial bearing end may be hardened.
According to one exemplary arrangement, a recess is formed in an axial bearing end opposite the gearing on the drive-side end of the force transmission element, and a component forming an axial bearing contact is fastened in the recess.
According to a further aspect of the disclosure, a gear shaft for an electromechanical brake booster comprises a force transmission element having a gearing end for tapping off a drive torque and a gearwheel for imparting an output torque. According to the disclosure, a positioning and fastening device for the gearwheel is formed in one piece with the force transmission element.
According to one exemplary arrangement, the gear shaft comprises two bearing portions, for example radial bearing portions, with which a radial bearing is in engagement in each case.
According to one exemplary arrangement, the gear shaft comprises a removable and/or separately manufactured axial positioning device for fixing the position of the gear shaft in the electromechanical brake booster with respect to a drive side. For example, a fastening aid for the axial positioning device is provided, which fastening aid is formed in one piece with the force transmission element.
According to one exemplary arrangement, the fastening and positioning device has a material or lateral-surface elevation and/or depression, for example with respect to the outer circumference of the force transmission element. In one exemplary arrangement, multiple lateral-surface elevations and/or depressions, arranged rotationally symmetrically around the force transmission element, are provided. For example, the lateral-surface elevations and/or depressions extend in the direction of the longitudinal extent of the force transmission element such that they are parallel to the axis of rotation.
According to an exemplary arrangement, the force transmission element has an axial bearing end opposite the gearing end, for example in the axial direction of extent, for tapping off a drive torque. In one exemplary arrangement, the axial bearing end is formed in one piece with the force transmission element. For example, the axial bearing end has a fastening aid, in which a component forming an axial bearing contact is received. The component forming the axial bearing contact may be a hardened steel ball.
According to one exemplary arrangement, the gear shaft is produced according to the method according to the disclosure. For example, the positioning and fastening device comprises an anchoring between the gearwheel and the force transmission element, which anchoring is fixed against rotation and/or axial thrust.
According to a further aspect of the disclosure, an electromechanical brake booster is provided, having an electric motor and having a rotation/translation conversion gear, which converts a rotating drive movement of the electric motor into a linear movement for actuating a piston-cylinder unit for generating a hydraulic brake pressure. According to the disclosure, the rotation/translation conversion gear comprises a gear shaft according to the disclosure and/or which is produced according to the disclosure.
One or more aspects of the disclosure are advantageous in that the gear shaft may be manufactured in a simple and cost-effective manner. One or more aspects of the disclosure are advantageous in that functional constituent parts may be manufactured in at least partly separate manufacturing steps, whereby manufacturing flexibility, scalability and dimensional accuracy may be improved. One or more aspects of the disclosure are advantageous in that the processing of certain functional components is already completed before further processing steps ensue, so that fixed processing reference points, such as reference dimensions, are available for subsequent steps. One or more aspects of the disclosure are advantageous in that regions of the components to be manufactured or the manufactured components are not sensitive to external influences in later manufacturing steps. One or more aspects of the disclosure are advantageous in that functional constituent parts are manufactured in one piece from a semi-finished product, whereby the handling labour is reduced and the force transmission within the component may be improved.
Further features, advantages and properties of the disclosure are explained with the aid of the description of exemplary arrangements of the disclosure and with reference to the figures, in which:
At the drive-side end 22, a gearing end 25 is incorporated in the force transmission element 20 by cutting. In the final installed state, the gearing end 25 is connected to the output of an electric motor (not illustrated in more detail) of an electromechanical brake booster via a clutch 37 (illustrated in
At the output-side axial bearing end 24, the force transmission element 20 is supported axially in a housing 3 (partly illustrated in
Between the drive-side end 22 and the output-side axial bearing end 24, two regions of the force transmission element 20 are produced in a manufacturing process as bearing portions 27, 29, such that that they may be brought into engagement with a radial bearing 34, 32 (illustrated in
A positioning and fastening device 28 for a gearwheel (not illustrated in
Between the two bearing portions 27, 29, on the side of the bearing portion 29, a narrowing 33 is formed in the force transmission element 20, which narrowing serves as a fastening aid for an axial positioning device 31, which can be seen, for example, in
In
In one variant, during the pushing-on procedure, the at least one rib 26 of the positioning and fastening device 28 acts in a cutting, abrasive, elastically deforming and/or plastically deforming manner in the shaft receiving opening of the gear wheel 30, so that rotationally fixed and/or axially fixed anchoring is realized after the pushing-on procedure. The at least one rib 26 and the shaft receiving opening may be matched to one another in terms of their dimensions such that a gearwheel-side part of the positioning and fastening device 28 is formed during the pushing-on procedure.
In another exemplary variant, the shaft receiving opening of the gearwheel 30 has at least one recess and/or at least one projection, which correspond to the at least one rib 26 and/or the at least one notch 23, so that a positioning and fastening device 28 is formed by latching elements on the gearwheel 30 and the force transmission element 20, which latching elements are prefabricated with complementary forms.
At the drive-side end 22, the drive force is imparted to the gear shaft 10 via a clutch 37 from the output end of an electric motor or a gear portion which is connected to the electric motor such that it is in closer proximity to the source within the drive train than the force transmission element. The gearing end 25 is formed with a smaller circumference or radius than the force transmission element 20 such that the force transmission element 20 forms an axial end stop 39 for the clutch 37.
The gear shaft 10 is supported radially on the radial bearings 32, 34, which are in engagement with the bearing portions 29, 27. The radial bearings 32, 34 are designed as ball or roller bearings, for example as needle bearings. In one exemplary arrangement, in the region of the respective bearing portion 29, 27, an inner bearing surface of the bearing is formed by the lateral cylinder surface or the outer circumferential surface of the force transmission element 20.
In terms of its function and production, the gear shaft 10 shown in
To form an axial positioning device 31, a snap ring is pushed onto the narrowing 33 with elastic deformation. With regard to the dimensions of the narrowing 33 in the longitudinal direction of extent and the radial direction of the force transmission element 20, the snap ring is dimensioned such that a position-defining axial stop is formed. The axial positioning device is formed after forming the bearing surfaces 27, 29, which facilitates the manufacture thereof.
In the exemplary arrangement according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022134795.8 | Dec 2022 | DE | national |
