Abstract
A ball screw (1) having a threaded nut (3) arranged on the threaded shaft (2) and a ball channel (4) wound about the longitudinal axis of the threaded shaft (2), and in which the balls (5) and at least one helical spring (6) are received. This helical spring (6) is supported on a molded part (7) which is inserted into a recess (8) of the threaded nut (3) and closes the recess (8).
Claims
1. A ball screw comprising a threaded nut arranged on a threaded shaft, the threaded shaft including threads that define a ball channel wound about a longitudinal axis of the threaded shaft, balls and at least one helical spring are received in the ball channel, a molded part that supports the helical spring is inserted into a recess of the threaded nut and closes the recess, the molded part is held with a positive fit in the recess by contact with the threads of the threaded shaft, the molded part has a projecting shoulder extending in a circumferential direction with a first surface pointing toward the threaded nut and a second, oppositely arranged surface pointing toward the threaded shaft.
2. The ball screw according to claim 1, wherein the molded part has a section with an opposite construction with respect to a threaded profile of the threaded shaft.
3. The ball screw according to claim 1, wherein the projecting shoulder that extends in the circumferential direction has a circular segment shape.
4. The ball screw according to claim 1, wherein the molded part is an injection molded, die cast, or sintered part.
5. The ball screw according to claim 1, wherein the molded part is a machined part.
6. The ball screw according to claim 1, wherein said shoulder engages in a ring gap defined by the threaded nut and the threaded shaft.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) An embodiment of the invention is shown in the drawing and is described in more detail below. Shown are:
(2) FIG. 1 a side view of a ball screw according to the invention,
(3) FIG. 2 a section view of the ball screw shown in FIG. 1 in an assembled position,
(4) FIG. 3 a view of the ball screw shown in FIG. 2 in the axial direction,
(5) FIG. 4 an enlarged view of the molded part,
(6) FIG. 5 an enlarged section view of the molded part in an assembled position,
(7) FIG. 6 a side view sectioned according to FIG. 2 of the ball screw according to the invention after assembly,
(8) FIG. 7 an axial view corresponding to FIG. 3 of the ball screw from FIG. 6,
(9) FIG. 8 an enlarged view corresponding to FIG. 4 of the molded part from FIG. 7,
(10) FIG. 9 an enlarged view corresponding to FIG. 5 of the molded part from FIG. 6 after assembly,
(11) FIG. 10 a perspective view of the molded part, and
(12) FIG. 11 another perspective view of the molded part.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(13) The ball screw 1 shown in a side view in FIG. 1 and in a section view in FIG. 2 comprises a threaded nut 3 arranged on a threaded shaft 2 and a ball channel 4 wound about the longitudinal axis of the threaded shaft 2. In the section of the ball channel 4 that is located on the inner side of threaded nut 3 there are balls 5 and helical springs 6. The ball screw 1 is part of a parking brake that can be actuated electromechanically and is known from DE 10 2008 062 180 A1. A detailed explanation of the other components of the parking brake is therefore not provided here. In the sectioned side view of FIG. 2, it can be seen that the balls 5 are located in the ball channel 4. In addition, the helical spring 6 is provided that is located at one end of the ball channel 4.
(14) FIG. 3 is an axial view of the ball screw of FIG. 2 in the direction of the arrow shown there. It can be seen that one end of the helical spring 6 contacts a molded part 7 that is shown in FIG. 4 in an enlarged view. The molded part 7 is inserted into a recess 8 of the threaded nut 3. The molded part 7 closes the recess 8, so that the helical spring 6 contacts the molded part 7 and not the recess 8, as in other constructions. This prevents the end of the helical spring 6 from being able to buckle or deform in the ball channel 4.
(15) FIG. 5 shows the molded part 7 from FIG. 2 and FIG. 3 in an enlarged view. In FIG. 5, it can be seen that the molded part 7 has a projecting shoulder 9 that extends in the circumferential direction and is held in a ring gap between the threaded nut 3 and the threaded shaft 2. The shoulder 9 has a first surface 10 that points toward the threaded nut 3 and a second, opposite surface 11 that points toward the threaded shaft 2. The ring gap 18 is defined by the tooth tips 14, 15 of the helical ball grooves 16, 17 that are wound about the shaft axis and are formed on the threaded shaft 2 and on the threaded nut 3. The shoulder 9 curved in an arc shape about the shaft axis engages in this ring gap 18. This arc-shaped shoulder 9 here has a circular segment-like construction. The shoulder 9 prevents the molded part 7 from being able to be incorrectly tipped about a tipping axis a in the installed state.
(16) FIG. 2 shows the ball screw 1 in an assembled position. The threaded shaft 2 is rotated in the threaded nut 3 so that the molded part 7 can be inserted and installed in the axial direction. After assembly, the threaded shaft 2 is rotated back into an operating position that is shown in FIGS. 6-9. FIG. 6 here corresponds to FIG. 2 and shows a sectioned side view of the ball screw 1. FIG. 7 is an axial view of FIG. 6. FIG. 8 shows an enlarged detail in the area of the molded part. And FIG. 9 shows the molded part from FIG. 6 in an enlarged view.
(17) In FIGS. 6 to 9, the threaded shaft 2 is located in its operating position. To reach this position, it was rotated back starting from the operating position shown in FIGS. 2 to 5. In FIGS. 6 and 9 it can be seen that the threaded shaft 2 has a threaded shoulder 12, so that the molded part 7 is held with a positive fit in the recess 8. The shoulder 9 of the molded part 7 is used as an additional safety device, because it prevents distortion or unscrewing of the molded part 7, but such a shoulder is optional, that is, the molded part 7 basically satisfies its function even if no such shoulder is provided.
(18) FIGS. 10 and 11 are perspective views of the molded part 7. It can be seen that the projecting shoulder 9 extending in the circumferential direction has a circular segment-like construction. The molded part 7 has a section 13 with an approximately equal but opposite construction with respect to the threaded profile (ball channel 4) of the threaded shaft 2. Accordingly, the molded part 7 is held in the assembled state by its section 13 with a positive fit in the profile of the threaded shaft 2. The other, opposite end of the molded part 7 is held with a positive fit in the recess 8 of the threaded nut.
LIST OF REFERENCE NUMBERS
(19) 1 Ball screw 2 Threaded shaft 3 Threaded nut 4 Ball channel 5 Balls 6 Helical spring 7 Molded part 8 Recess 9 Shoulder 10 First surface 11 Second surface 12 Threaded shoulder 13 Section a Tipping axis
