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, the brake pressure generator comprising: a threaded drive system that is configured to convert a drive-side rotary motion into a translatory motion and that includes: a drive wheel that is rotatable by an electric motor; a spindle nut that is arranged at an interior of the drive wheel and is rotationally fixed relative to the drive wheel, so that the spindle nut rotates whenever the drive wheel rotates; 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 a piston/cylinder unit, the piston/cylinder unit being actuatable by the threaded drive system for hydraulic brake pressure generation; and a housing of the piston/cylinder unit that at least partially surrounds the spindle, the spindle nut, and the hydraulic piston; wherein: an anti-twist protection, via which the spindle is secured against twisting during the rotation of the spindle nut, includes a torque support that (a) is part of the hydraulic piston and (b) engages in an axial recess of the housing, the recess forming a sliding surface for the torque support of the hydraulic piston; the spindle nut includes a radially outwardly extending projection that has a first spindle nut surface facing in a first axial direction; a groove extends, within a thickness of a wall of the housing, circumferentially around a longitudinal central axis of the spindle and is divided into multiple sections by the axial recess which is formed within the thickness of the wall of the housing perpendicularly to the groove; the groove has a groove floor facing in the first axial direction and a groove ceiling facing in a second axial direction that is opposite to the first axial direction; the drive wheel extends with a portion of the drive wheel passing radially inwards over an exterior edge of the housing that faces in the first axial direction towards the passing portion of the drive wheel, the passing portion of the drive wheel not being radially within the housing; a radially interior region of the drive wheel is attached to the spindle nut and has a first drive wheel surface that faces in the second axial direction and that is within the housing; the threaded drive system includes a bearing ring; a radially exterior edge section of the bearing ring is held within the groove with a first exterior bearing ring surface of the radially exterior edge section of the bearing ring that faces in the first axial direction abutting against the groove ceiling and a second exterior bearing ring surface of the radially exterior edge section of the bearing ring that faces in the second axial direction abutting against the groove floor; and a radially interior edge section of the bearing ring is held with a first interior bearing ring surface of the radially interior edge section of the bearing ring that faces in the first axial direction abutting against the first drive wheel surface of the radially interior region of the drive wheel and a second interior bearing ring surface of the radially interior edge section of the bearing ring that faces in the second axial direction abutting against the first spindle nut surface of the radially outwardly extending projection of the spindle nut, the bearing ring thereby fixing an axial position of the spindle nut relative to the housing, with the spindle nut being rotatable relative to the housing, while engagement of the torque support with the axial recess rotationally fixes the spindle relative to the housing, with the spindle being axially translatable relative to the housing.

2. The electromechanical brake pressure generator as recited in claim 1, wherein at least a portion of the spindle nut is arranged radially between at least a portion of the hydraulic piston and at least a portion of the spindle and the torque support is arranged at an axial position occupied by the spindle nut.

3. The electromechanical brake pressure generator as recited in claim 1, wherein the housing is formed of a first housing part and a second housing part that is integrally joined to the first housing part and projects perpendicularly from an exterior edge surface of the first housing part that faces in the first axial direction, the recess extending from within the first housing part into the second housing part, and the sliding surface is continuous and seamless in the axial directions.

4. The electromechanical brake pressure generator as recited in claim 1, wherein a contact shoe via which the torque support rests 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.

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

6. The electromechanical brake pressure generator as recited in claim 1, wherein an axially extending radially outer edge of the recess (a) protrudes radially outward beyond a radially exterior surface of the housing that is present in a circumferential region of the housing that includes the groove and (b) is rounded about an axis that is parallel to the longitudinal central axis of the spindle.

7. The electromechanical brake pressure generator as recited in claim 1, wherein the radially outwardly extending projection of the spindle nut includes a second spindle nut surface that faces in the second axial direction and that is arranged as an end stop that limits an extent to which the torque support is axially slidable in the first axial direction within the recess.

8. A method for manufacturing an electromechanical brake pressure generator for a hydraulic braking system of a vehicle, the electromechanical brake pressure generator including a threaded drive system that is configured to convert a drive-side rotary motion into a translatory motion, the threaded drive system including a drive wheel that is rotatable by an electric motor, a spindle nut, a spindle, a hydraulic piston of a piston/cylinder unit, and a housing of the piston/cylinder unit, the method comprising the following steps: integrally joining at least two housing parts to form the housing; and forming an axial recess of the housing that (a) extends axially and includes a sliding surface, the recess and the sliding surface extending across the housing parts, and (b) together with a torque support which is part of the hydraulic piston and engages in the axial recess, forms an anti-twist protection via which the spindle is secured against twisting during the rotation of the spindle nut; wherein: the spindle nut is arranged at an interior of the drive wheel and is rotationally fixed relative to the drive wheel, so that the spindle nut rotates whenever the drive wheel rotates; the spindle cooperates with a thread of the spindle nut so that the spindle is axially displaceable by the rotation of the spindle nut; the piston/cylinder unit is actuatable by the threaded drive system for hydraulic brake pressure generation; the housing at least partially surrounds the spindle, the spindle nut, and the hydraulic piston; the spindle nut includes a radially outwardly extending projection that has a first spindle nut surface facing in a first axial direction; a groove extends, within a thickness of a wall of the housing, circumferentially around a longitudinal central axis of the spindle and is divided into multiple sections by the axial recess which is formed within the thickness of the wall of the housing perpendicularly to the groove; the groove has a groove floor facing in the first axial direction and a groove ceiling facing in a second axial direction that is opposite to the first axial direction; the drive wheel extends with a portion of the drive wheel passing radially inwards over an exterior edge of the housing that faces in the first axial direction towards the passing portion of the drive wheel, the passing portion of the drive wheel not being radially within the housing; a radially interior region of the drive wheel is attached to the spindle nut and has a first drive wheel surface that faces in the second axial direction and that is within the housing; the threaded drive system includes a bearing ring; a radially exterior edge section of the bearing ring is held within the groove with a first exterior bearing ring surface of the radially exterior edge section of the bearing ring that faces in the first axial direction abutting against the groove ceiling and a second exterior bearing ring surface of the radially exterior edge section of the bearing ring that faces in the second axial direction abutting against the groove floor; and a radially interior edge section of the bearing ring is held with a first interior bearing ring surface of the radially interior edge section of the bearing ring that faces in the first axial direction abutting against the first drive wheel surface of the radially interior region of the drive wheel and a second interior bearing ring surface of the radially interior edge section of the bearing ring that faces in the second axial direction abutting against the first spindle nut surface of the radially outwardly extending projection of the spindle nut, the bearing ring thereby fixing an axial position of the spindle nut relative to the housing, with the spindle nut being rotatable relative to the housing, while engagement of the torque support with the axial recess rotationally fixes the spindle relative to the housing, with the spindle being axially translatable relative to the housing.

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

10. The method as recited in claim 8, wherein an axially outer end of the housing is caulked after the bearing ring has been introduced to thereby form the ceiling of the groove.

11. A vehicle, comprising: a hydraulic braking system; and an electromechanical brake pressure generator for the hydraulic braking system, the electromechanical brake pressure generator including a threaded drive system (a) that is configured to convert a drive-side rotary motion into a translatory motion and (b) that includes: a drive wheel that is rotatable by an electric motor; a spindle nut that is arranged at an interior of the drive wheel and is rotationally fixed relative to the drive wheel, so that the spindle nut rotates whenever the drive wheel rotates; 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 a piston/cylinder unit, the piston/cylinder unit being actuatable by the threaded drive system for hydraulic brake pressure generation; and a housing of the piston/cylinder unit that at least partially surrounds the spindle, the spindle nut, and the hydraulic piston; wherein: an anti-twist protection, via which the spindle is secured against twisting during the rotation of the spindle nut, includes a torque support that (a) is part of the hydraulic piston and (b) engages in an axial recess of the housing, the recess forming a sliding surface for the torque support of the hydraulic piston; the spindle nut includes a radially outwardly extending projection that has a first spindle nut surface facing in a first axial direction; a groove extends, within a thickness of a wall of the housing, circumferentially around a longitudinal central axis of the spindle and is divided into multiple sections by the axial recess which is formed within the thickness of the wall of the housing perpendicularly to the groove; the groove has a groove floor facing in the first axial direction and a groove ceiling facing in a second axial direction that is opposite to the first axial direction; the drive wheel extends with a portion of the drive wheel passing radially inwards over an exterior edge of the housing that faces in the first axial direction towards the passing portion of the drive wheel, the passing portion of the drive wheel not being radially within the housing; a radially interior region of the drive wheel is attached to the spindle nut and has a first drive wheel surface that faces in the second axial direction and that is within the housing; the threaded drive system includes a bearing ring; a radially exterior edge section of the bearing ring is held within the groove with a first exterior bearing ring surface of the radially exterior edge section of the bearing ring that faces in the first axial direction abutting against the groove ceiling and a second exterior bearing ring surface of the radially exterior edge section of the bearing ring that faces in the second axial direction abutting against the groove floor; and a radially interior edge section of the bearing ring is held with a first interior bearing ring surface of the radially interior edge section of the bearing ring that faces in the first axial direction abutting against the first drive wheel surface of the radially interior region of the drive wheel and a second interior bearing ring surface of the radially interior edge section of the bearing ring that faces in the second axial direction abutting against the first spindle nut surface of the radially outwardly extending projection of the spindle nut, the bearing ring thereby fixing an axial position of the spindle nut relative to the housing, with the spindle nut being rotatable relative to the housing, while engagement of the torque support with the axial recess rotationally fixes the spindle relative to the housing, with the spindle being axially translatable relative to the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an illustration of a conventional electromechanical brake booster from the related art.

(2) FIG. 2 shows a schematic illustration of a hydraulic braking system for a vehicle including an electromechanical brake pressure generator.

(3) 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.

(4) 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

(5) 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.

(6) 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.

(7) 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.

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) 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.

(14) 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.

(15) 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.

(16) 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.

(17) 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.