ELECTROMECHANICAL BRAKE PRESSURE GENERATOR OR BOOSTER HAVING A THREADED DRIVE ASSEMBLAGE

Abstract

An electromechanically drivable brake pressure generator for a hydraulic braking system of a vehicle, having at least one threaded drive assemblage for converting an input-drive-side rotary motion into a translational motion, and a piston/cylinder unit, actuatable by the threaded drive assemblage, for hydraulic brake pressure generation. The assemblage encompasses: a spindle that has a spindle thread; and a spindle nut that has a spindle nut thread, the spindle nut being disposed on the spindle thread of the spindle so that as one of the two spindle elements rotates, the other, which is prevented from twisting using a twist preventer, is axially displaceable. The spindle nut has a spindle nut body and at least one anti-friction layer made of plastic, which is applied on the spindle nut body and has a more pronounced anti-friction property than the spindle nut body, that anti-friction layer being applied on the spindle nut thread.

Claims

1. An electromechanically drivable brake pressure generator for a hydraulic braking system of a vehicle, comprising: at least one threaded drive assemblage configured to convert an input-drive-side rotary motion into a translational motion; and a piston/cylinder unit, actuatable by the threaded drive assemblage, for hydraulic brake pressure generation; wherein the threaded drive assemblage includes: a spindle that has a spindle thread; and a spindle nut that has a spindle nut thread, the spindle nut being disposed on the spindle thread of the spindle in such a way that as one of the spindle and spindle nut rotates, the other one of the spindle and spindle nut, which is prevented from twisting using a twist preventer, is axially displaceable; wherein the spindle nut has a spindle nut body and at least one anti-friction layer made of plastic, which is applied on the spindle nut body and has a more pronounced anti-friction property than an anti-friction property of the spindle nut body, the anti-friction layer being applied at least on the spindle nut thread.

2. The electromechanically drivable brake pressure generator as recited in claim 1, wherein the anti-friction layer has lower strength than the spindle nut body.

3. The electromechanically drivable brake pressure generator (as recited in claim 1, wherein the spindle nut body is made from metallic material.

4. The electromechanically drivable brake pressure generator as recited in claim 1, wherein the spindle nut body is made from a plastic material.

5. The electromechanically drivable brake pressure generator as recited in claim 4, wherein the spindle nut body is fiber-reinforced.

6. The electromechanically drivable brake pressure generator as recited in claim 1, wherein the spindle nut body has several twist preventers that form sliding surfaces, the anti-friction layer being applied onto the sliding surfaces.

7. The electromechanically drivable brake pressure generator as recited in claim 1, wherein the spindle nut body is completely coated with the anti-friction layer.

8. A vehicle having an electromechanically drivable brake pressure generator for a hydraulic braking system, the electromechanically drivable brake pressure generator comprising: at least one threaded drive assemblage configured to convert an input-drive-side rotary motion into a translational motion; and a piston/cylinder unit, actuatable by the threaded drive assemblage, for hydraulic brake pressure generation; wherein the threaded drive assemblage includes: a spindle that has a spindle thread; and a spindle nut that has a spindle nut thread, the spindle nut being disposed on the spindle thread of the spindle in such a way that as one of the spindle and spindle nut rotates, the other one of the spindle and spindle nut, which is prevented from twisting using a twist preventer, is axially displaceable; wherein the spindle nut has a spindle nut body and at least one anti-friction layer made of plastic, which is applied on the spindle nut body and has a more pronounced anti-friction property than an anti-friction property of the spindle nut body, the anti-friction layer being applied at least on the spindle nut thread.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 depicts an conventional electromechanical brake pressure generator from the related art.

[0023] FIG. 2 is a simplified schematic depiction of a conventional hydraulic braking system, from the related art, for a vehicle, having an electromechanical brake pressure generator.

[0024] FIG. 3 depicts a spindle/spindle nut unit of the threaded drive assemblage.

[0025] FIG. 4 is an enlarged depiction of the spindle nut thread on which an anti-friction layer is applied.

[0026] FIG. 5 is a partial perspective depiction of the spindle nut, having a twist preventer on which the anti-friction layer is applied.

[0027] FIG. 6 is a perspective view of a spindle nut on which an anti-friction layer is applied.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0028] FIG. 2 is a simplified schematic depiction of a conventional hydraulic braking system 10, from the related art, for a vehicle, having an electromechanical brake pressure generator 14. Hydraulic braking system 10 encompasses electromechanical brake pressure generator 14 and a piston/cylinder unit 18. Piston/cylinder unit 18 and electromechanical brake pressure generator 14 are both hydraulically connected to a brake hydraulics unit 22 that is depicted here merely as a box.

[0029] Brake hydraulics unit 22 is configured, by way of various valves and further components, to embody, e.g., an electronic stability program (ESP). In order to allow the vehicle to be decelerated, brake hydraulics unit 22 is additionally connected to at least one wheel brake device 26 so that, by corresponding switching of valves, a braking force can be applied to wheel brake device 26.

[0030] Piston/cylinder unit 18 is actuated by muscle force via a brake pedal 30. In contrast thereto, the braking force of electromechanical brake pressure generator 14 is generated via an electric motor 34. Electric motor 34 is connected for that purpose to a linkage 38 by which a threaded drive assemblage 42 is driven. Threaded drive assemblage 42 is connected to a hydraulic piston 46 disposed in a hydraulic cylinder 44, so that a brake pressure can be generated.

[0031] FIG. 3 depicts a spindle/spindle nut unit 50 of threaded drive assemblage 42. FIG. 3 shows only a portion of spindle/spindle nut unit 50. A threaded drive assemblage 42 encompassing spindle/spindle nut unit 50 could be used in hydraulic braking system 10 shown in FIG. 2. Spindle/spindle nut unit 50 of threaded drive assemblage 42 encompasses a spindle 54 that is partly surrounded by a spindle nut 58.

[0032] Spindle 54 has a spindle thread 62 that is in engagement with a spindle nut thread 66 that is embodied on spindle nut 58. In this exemplifying embodiment, spindle nut 58 encompasses twist preventers 70 that project radially. These twist preventers 70 are in engagement with a housing (not shown). The result is that upon a rotation of spindle 54, spindle nut 58 does not rotate along with it. Spindle 54 is thereby axially displaceable.

[0033] Spindle nut 58 additionally has an anti-friction layer 74 that is applied onto spindle nut thread 66 of a spindle nut body 78. FIG. 4 is, for that purpose, an enlarged view of a portion of spindle nut thread 66. For better illustration, spindle 54 has been omitted from this Figure. As shown in FIG. 4, a continuous anti-friction layer 74 made of plastic is applied onto spindle nut thread 66 of spindle nut body 78. This plastic has lubrication properties, so that an easier rotary motion of spindle 54 is possible and emergency mode properties are guaranteed.

[0034] FIG. 5 is a partial perspective depiction of spindle nut 58 having a twist preventer 70 on which an anti-friction layer 74 is applied. Only half of spindle nut 58 is depicted in this Figure. Anti-friction layers 74 are additionally applied onto sliding surfaces 76, which here are the longitudinal sides of twist preventers 70. Sliding surfaces 76 are the sides that abut, for example, against a housing in order to prevent twisting. During an axial motion of spindle nut 58, twist preventer 70 essentially slips along a corresponding surface of the housing. Anti-friction layer 74 makes possible easy slippage of twist preventers 70.

[0035] FIG. 6 is a perspective view of a spindle nut 58 on which an anti-friction layer 74 is applied. For spindle nut 58 shown in FIG. 6, anti-friction layer 74 is depicted only in section. In this exemplifying embodiment spindle nut 58 additionally has a total of four twist preventers 70. With this spindle nut 58, the entire spindle nut 58 has anti-friction layer 74. Sliding contact with all components with which spindle nut 58 is in contact is thereby improved. In addition, anti-friction layer 74 can more easily be applied onto spindle nut body 78, for example, in the course of injection molding.