ELECTROMECHANICAL BRAKE PRESSURE GENERATOR FOR A HYDRAULIC BRAKING SYSTEM OF A VEHICLE AND METHOD FOR MANUFACTURING AN ELECTROMECHANICAL BRAKE PRESSURE GENERATOR

Abstract

An electromechanical brake pressure generator including a threaded drive system. The system includes a rotatable spindle nut, a axially displaceable spindle cooperating with a thread of the spindle nut, and a hydraulic piston which at least partially radially surrounds the spindle and the spindle nut and is rotatably fixedly connected to the spindle and which carries out an axial piston stroke as a result of the rotation of the spindle nut. The system includes a housing which at least partially surrounds the hydraulic piston and forms a hydraulic cylinder, and an axial recess, in the hydraulic cylinder, which forms an anti-twist protection together with a torque support formed at the hydraulic piston and using which the hydraulic piston and the spindle are secured against twisting during a rotation of the spindle nut, the recess forming a sliding surface for the torque support of the hydraulic piston.

Claims

1. An electromechanical brake pressure generator for a hydraulic braking system of a vehicle, comprising: at least one threaded drive system configured to convert a drive-side rotary motion into a translatory motion; and a piston/cylinder unit actuatable by the threaded drive system for hydraulic brake pressure generation; wherein the threaded drive system includes: a spindle nut which is rotatable via an electric motor; a spindle which cooperates with a thread of the spindle nut so that the spindle is axially displaced with a rotation of the spindle nut; a hydraulic piston of the piston/cylinder unit; a housing of the piston/cylinder unit which at least partially surrounds the spindle, the spindle nut and the hydraulic piston; and an anti-twist protection via which the spindle is secured against twisting during a rotation of the spindle nut, wherein the anti-twist protection includes a torque support which is configured at the hydraulic piston and engages in an axial recess of the housing, the recess forming a sliding surface for the torque support of the hydraulic piston.

2. The electromechanical brake pressure generator as recited in claim 1, wherein the housing is formed of at least two housing parts integrally joined to one another, the recess extending across the housing parts, and the sliding surface is continuous and seamless in an axial direction.

3. The electromechanical brake pressure generator as recited in claim 1, wherein a contact shoe via which the torque support rest against the sliding surface is situated at the torque support in a contact area with the sliding surface, the contact shoe being made of a material different from the hydraulic piston.

4. The electromechanical brake pressure generator as recited in claim 3, wherein the contact shoe is made of a plastic material.

5. The electromechanical brake pressure generator as recited in claim 1, wherein a caulking is formed at an axially outer end of the housing, so that a bearing for the spindle nut is attached in an axial direction between the caulking and a housing projection.

6. The electromechanical brake pressure generator as recited in claim 1, wherein a radially outer end of the recess includes a rounding.

7. A method for manufacturing an electromechanical brake pressure generator, the electromechanical brake pressure generator including at least one threaded drive system configured to convert a drive-side rotary motion into a translatory motion, and a piston/cylinder unit actuatable by the threaded drive system for hydraulic brake pressure generation, wherein the threaded drive system includes a spindle nut which is rotatable via an electric motor, a spindle which cooperates with a thread of the spindle nut so that the spindle is axially displaced with a rotation of the spindle nut, a hydraulic piston of the piston/cylinder unit, a housing of the piston/cylinder unit which at least partially surrounds the spindle, the spindle nut and the hydraulic piston, and an anti-twist protection via which the spindle is secured against twisting during a rotation of the spindle nut, wherein the anti-twist protection includes a torque support which is configured at the hydraulic piston and engages in an axial recess of the housing, the recess forming a sliding surface for the torque support of the hydraulic piston, the method comprising the following steps: integrally joining at least two housing parts to form the housing; and forming the recess which extends in the axial direction and includes the sliding surface, the recess and the sliding surface extending across the housing parts, and, together with the torque support of the hydraulic piston, forms the anti-twist protection for the hydraulic piston and the spindle.

8. The method as recited in claim 7, wherein the housing parts forming the housing are integrally joined to one another using friction stir welding.

9. The method as recited in claim 7, wherein an axially outer end of the housing is caulked after a bearing supporting the spindle nut has been introduced, so that the bearing is held in the axial direction.

10. A vehicle, comprising: a hydraulic braking system; and an electromechanical brake pressure generator for the hydraulic braking system, the electromechanical brake pressure generator including: at least one threaded drive system configured to convert a drive-side rotary motion into a translatory motion; and a piston/cylinder unit actuatable by the threaded drive system for hydraulic brake pressure generation; wherein the threaded drive system includes: a spindle nut which is rotatable via an electric motor; a spindle which cooperates with a thread of the spindle nut so that the spindle is axially displaced with a rotation of the spindle nut; a hydraulic piston of the piston/cylinder unit; a housing of the piston/cylinder unit which at least partially surrounds the spindle, the spindle nut and the hydraulic piston; and an anti-twist protection via which the spindle is secured against twisting during a rotation of the spindle nut, wherein the anti-twist protection includes a torque support which is configured at the hydraulic piston and engages in an axial recess of the housing, the recess forming a sliding surface for the torque support of the hydraulic piston.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 shows an illustration of a conventional electromechanical brake booster from the related art.

[0029] FIG. 2 shows a schematic illustration of a hydraulic braking system for a vehicle including an electromechanical brake pressure generator.

[0030] FIG. 3 shows a sectional illustration of one exemplary embodiment of a threaded drive system according to the present invention of the electromechanical brake pressure generator.

[0031] FIG. 4 shows a perspective view of one exemplary embodiment of a housing of the threaded drive system of the electromechanical brake pressure generator.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0032] FIG. 2 shows a schematic illustration of a hydraulic braking system 10 for a vehicle including an electromechanical brake pressure generator 14. Hydraulic braking system 10 includes electromechanical brake pressure generator 14. This brake pressure generator 14 includes a piston/cylinder unit 18 which is supplied with brake fluid via a brake fluid reservoir 22.

[0033] Piston/cylinder unit 18 may be activated by a brake pedal 26 actuated by the driver, and the resulting brake pedal travel is measured by a pedal travel sensor 30 and forwarded to a control unit 34.

[0034] Even though FIG. 2, generally, shows a brake booster, here, the brake pedal travel is measured by pedal travel sensor 30. A brake pressure generation without a brake pedal travel is also possible, so that the vehicle is also brakable in the autonomous driving state.

[0035] Based on the measured brake pedal travel, control unit 34 generates a control signal for an electric motor 38 of brake pressure generator 14. Electric motor 38, which is connected to a gearbox (not shown) of brake pressure generator 14, boosts the braking force input by brake pedal 26 within the scope of a decoupled system in accordance with the control signal. For this purpose, a threaded drive system 40 situated in brake pressure generator 14 is activated by electric motor 38 in accordance with the actuation of brake pedal 26 so that the rotary motion of electric motor 38 is converted into a translatory motion.

[0036] With the aid of brake pressure generator 14, the brake fluid present in piston/cylinder unit 18 is pressurized by the actuation of brake pedal 26. This brake pressure is forwarded to a brake hydraulic system 46 via brake lines 42. Brake hydraulic system 46, which is only shown as a box here, is formed by various valves and other components for forming a, for example, electronic stability program (ESP). Brake hydraulic system 46 is additionally connected to at least one wheel brake unit 50 so that a braking force may be applied to wheel brake unit 50 by a corresponding switching of valves.

[0037] FIG. 3 shows a sectional illustration of one exemplary embodiment of a threaded drive system 40 according to the present invention of electromechanical brake pressure generator 14. Threaded drive system 40 includes a housing 64, which is formed of two housing parts 64a, 64b (see FIG. 4). Housing 64, which is made of metal, forms a pot-shaped hydraulic cylinder 68.

[0038] Threaded drive unit 40 additionally includes a spindle nut 72, which is supported with the aid of a bearing 76 with respect to housing 64. In this exemplary embodiment, a drive wheel 80, which is rotatably fixedly connected to spindle nut 72, is situated at an axial end of spindle nut 72. Spindle nut 72 is driven by electric motor 38 shown in FIG. 2 with the aid of this drive wheel 80. Spindle nut 72 thus carries out a rotary motion about its longitudinal axis.

[0039] Spindle nut 72 surrounds a spindle 84, which is in engagement with spindle nut 72 with the aid of a thread 88. Spindle 84 is rotatably fixedly connected to a hydraulic piston 92 radially surrounding spindle nut 72. Hydraulic piston 92 and housing 64 form an anti-twist protection 96, 100 so that spindle 84 and hydraulic piston 92 are axially displaceable with a rotation of spindle nut 72. Hydraulic piston 92 thus carries out a piston stroke.

[0040] Anti-twist protection 96 of hydraulic piston 92 is formed by two torque supports 96 in this exemplary embodiment, which extend radially outwardly and protrude over the remaining hydraulic piston 92 on the outer side. The two torque supports 96 are situated at an angle of 180 with respect to one another. Anti-twist protection 100 of housing 64 is formed by two recesses 100 extending in the axial direction, in which torque supports 96 engage, so that hydraulic piston 92 and spindle nut 72 are secured against twisting.

[0041] Recesses 100 form sliding surfaces 104 extending in the axial direction, against which torque supports 96 rest. In addition, recesses 100 include a rounding 108 at radially outer ends. With a rotation of spindle nut 72, torque supports 96 slide in the axial direction on sliding surfaces 104 of recesses 100. In a contact area with sliding surface 104, torque supports 96 include contact shoes 112, with the aid of which improved sliding properties are achieved. In this exemplary embodiment, contact shoes 112 are made of plastic.

[0042] Bearing 76, with the aid of which spindle nut 72 is supported with respect to housing 64, is situated in housing 64 in the axial direction between a housing projection 116 and an axially outer end 120 of housing 64. A caulking 124 is formed at the axially outer end 120 of housing 64, so that bearing 76 is held between housing projection 116 and caulking 124 in the axial direction. This caulking 124 is formed after the installation of bearing 76.

[0043] FIG. 4 shows a perspective view of one exemplary embodiment of housing 64 of threaded drive system 40 of electromechanical brake pressure generator 14. For better illustration, spindle nut 72, spindle 84, bearing 76 and hydraulic piston 92 have been omitted in this figure. This figure furthermore shows caulking 124, which is only formed after an installation of bearing 76.

[0044] It is additionally apparent in this figure that housing 64 is formed of a first housing part 64a and a second housing part 64b. Second housing part 64b is integrally joined to first housing part 64a, for example with the aid of friction stir welding. After both housing parts 64a, 64b have been joined to one another, hydraulic cylinder 68 and recesses 100 including sliding surfaces 104 are formed, for example with the aid of milling. Due to the integral joint between the two housing parts 64a, 64b, a continuous and seamless sliding surface 104 may thus be created. As a result, a subsequently inserted sliding rail may be dispensed with, so that only contact shoes 112 are situated at torque supports 96.