Actuation device for a brake system, and brake system

Abstract

The invention relates to an actuation device (1) for a brake system (2), comprising an electric machine (21) which is arranged in a motor housing (20), a rotor (22) of the electric machine (21) being arranged on a rotatably mounted drive shaft (23) in a rotationally fixed manner, and a movably mounted actuator element (3), wherein the drive shaft (23) is coupled to the actuator element (3) by means of a transmission device (29) such that the actuator element (3) can be moved by the electric machine (21). The transmission device (29) has a worm gear (30) comprising a worm shaft (31) and a worm wheel (32), and the drive shaft (23) forms the worm shaft (31). According to the invention, the rotational axis (24) of the drive shaft (23) is aligned perpendicularly to the movement axis (4) of the actuator element (3).

Description

[0001] Description

[0002] title

[0003] The invention relates to an actuating device for a braking system, comprising an electric machine arranged in a motor housing, wherein a rotor of the electric machine is arranged in a rotationally fixed manner on a rotatably mounted drive shaft, and comprising a displaceably mounted actuator element, wherein the drive shaft is coupled to the actuator element by a gear device such that the actuator element is displaceable by the electric machine, wherein the gear device has a worm gear with a worm shaft and a worm wheel, and wherein the drive shaft forms the worm shaft.

[0004] The invention also relates to a braking system.

[0005] State of the art

[0006] A hydraulic braking system of a motor vehicle typically has several friction brake devices. The friction brake devices are operatively connected to an actuating device of the braking system in such a way that the friction brake devices can be actuated by the actuating device. With the increasing electrification of motor vehicles, actuating devices of braking systems are also becoming increasingly electrified. In this regard, it is known to equip an actuating device for a braking system with an electric motor arranged in a motor housing, wherein a rotor of the electric motor is arranged in a rotationally fixed manner on a rotatably mounted drive shaft. To enable actuation of the friction brake devices by the actuating device, the actuating device also has a displaceably mounted actuator element.The drive shaft is coupled to the actuator element by a gear mechanism such that the actuator element can be moved by the electric motor. The gear mechanism is thus designed to convert rotation of the drive shaft into translational movement of the actuator element. The friction brake devices can therefore be actuated by the electric motor. It is known to use a worm gear mechanism with a worm shaft and a worm wheel in the gear mechanism. The worm gear mechanism enables a high gear ratio to be achieved. Accordingly, the worm gear mechanism ensures that the actuating device generates little noise during operation. Typically, the worm shaft is formed by the drive shaft. Due to its worm shaft design, the drive shaft has a screw thread.

[0007] Disclosure of the invention

[0008] The actuating device according to the invention with the features of claim 1 has the advantage that the actuating device can be implemented cost-effectively. According to the invention, it is provided that a rotational axis of the drive shaft is aligned perpendicular to a displacement axis of the actuator element. By aligning the rotational axis of the drive shaft relative to the displacement axis of the actuator element according to the invention, a transmission-technically simple and mechanically robust coupling of the drive shaft to the actuator element can be achieved. The worm gear is preferably arranged coaxially to the actuator element, so that a longitudinal center axis of the worm gear corresponds to the displacement axis of the actuator element. This design of the actuating device has the advantage that the actuating device is compact and thus space-saving. The screw thread of the drive shaft preferably meshes with an external toothing of the worm gear.

[0009] According to a preferred embodiment, the transmission device comprises a spindle gear arranged downstream of the worm gear. The spindle gear reliably converts the rotation of the drive shaft into the translational movement of the actuator element. Furthermore, the use of a spindle gear is associated with low manufacturing costs. The spindle gear preferably comprises a rotatably mounted spindle nut and a displaceably mounted threaded spindle. The spindle nut preferably forms the worm wheel. Alternatively, the worm wheel is preferably arranged in a rotationally fixed manner on the spindle nut. The threaded spindle preferably forms the actuator element. Alternatively, the threaded spindle is preferably coupled to the actuator element in such a way that the actuator element can be displaced by the threaded spindle.

[0010] According to an alternative embodiment, it is preferably provided that the transmission device comprises a ball screw drive connected downstream of the worm gear. A ball screw drive can also reliably convert the rotation of the drive shaft into the translational movement of the actuator element. The ball screw drive preferably comprises a rotatably mounted nut and a displaceably mounted threaded spindle, with the force transmission between the nut and the threaded spindle being provided by several balls of the ball screw drive.

[0011] According to a preferred embodiment, the gear device is at least partially arranged in a gear housing of the actuating device, and the motor housing is fastened to the gear housing. By arranging the gear device in the gear housing, the gear device is protected from external influences by the gear housing. Preferably, the actuator element is also at least partially arranged in the gear housing. By fastening the motor housing to the gear housing, the actuating device as a whole is mechanically robust. Preferably, the worm gear is arranged in the gear housing. For this purpose, the drive shaft projects out of the motor housing and into the gear housing in such a way that the screw thread of the drive shaft is arranged in the gear housing.Preferably, the drive shaft extends into the gearbox housing through an opening in a housing wall of the gearbox housing. Preferably, the spindle gear or the ball screw is arranged at least partially within the gearbox housing. In particular, the motor housing is attached to the gearbox housing by at least one fastening means, such as a screw.

[0012] Preferably, the motor housing is attached to a gearbox housing flange of the gearbox housing. This allows for a particularly robust mechanical attachment of the motor housing to the gearbox housing, for example, using the aforementioned fastening means. Furthermore, attaching the motor housing to the gearbox housing flange can also provide a fluid seal acting between the motor housing and the gearbox housing. For this purpose, a motor housing flange of the motor housing preferably bears against the gearbox housing flange in a sealing manner.

[0013] The gear housing is preferably a cylindrical extrusion. Extrusions are typically inexpensive to manufacture, so that the manufacturing costs for the actuating device are further reduced by designing the gear housing as an extrusion. A cylindrical element has a circumferentially closed shell wall, wherein the shell wall forms or encloses an axial opening in the cylindrical element. Accordingly, the cylindrical extrusion also has such a shell wall and such an axial opening, wherein the axial opening forms a housing interior of the extrusion. However, the term "cylindrical" does not imply a cross-section with a specific shape. Rather, the cross-section of the extrusion can have different shapes.Preferably, however, the axial opening has an at least substantially circular cross-section. The extruded profile is preferably made of aluminum.

[0014] According to a preferred embodiment, the displacement axis of the actuator element is oriented perpendicular to a cross-sectional area of ​​the extrusion profile. The cross-sectional area of ​​an extrusion profile is the area whose shape corresponds to the opening of the extrusion die used to produce the extrusion profile. As previously mentioned, the extrusion profile has an axial opening due to its cylindrical shape. If the displacement axis of the actuator element is oriented perpendicular to the cross-sectional area of ​​the extrusion profile, the extrusion profile is correspondingly open in the displacement direction of the actuator element. This simplifies the coupling of the actuator element to another element, such as a master brake cylinder.

[0015] According to a preferred embodiment, at least a first bearing point of the drive shaft is supported by the gear housing. Because the drive shaft is supported by the gear housing, the position of the drive shaft in the gear housing can be defined particularly precisely. This leads to a reduction in the introduction of transverse forces into the worm gear.

[0016] According to a preferred embodiment, the first bearing point is arranged on a side of the screw thread facing away from the rotor. By mounting the drive shaft on the side of the screw thread facing away from the rotor, the introduction of transverse forces into the worm gear can be particularly effectively avoided. Preferably, in addition to the first bearing point, the drive shaft has a second bearing point which is arranged between the screw thread and the rotor. Particularly preferably, the second bearing point is mounted by a bearing plate arranged on the motor housing. Alternatively, the second bearing point is preferably also mounted by the gear housing. Preferably, in addition to the first bearing point, the drive shaft has a third bearing point which is arranged on a side of the rotor facing away from the screw thread.Particularly preferably, the third bearing point is supported by a base of the motor housing. Preferably, the drive shaft has both the second and the third bearing point in addition to the first bearing point, so that a total of at least three bearing points are present on the drive shaft. Alternatively, the drive shaft has only the second bearing point or only the third bearing point in addition to the first bearing point. According to a preferred embodiment, the drive shaft has a first end on the side of the screw thread facing away from the rotor, and that a speed sensor is arranged at the first end. The first end is easily accessible for measuring or detecting the speed of the drive shaft, so that the arrangement of the speed sensor at the first end of the drive shaft is preferred. The speed sensor is preferably pressed onto the first end.Preferably, the first bearing is located adjacent to the speed sensor. This allows for particularly precise measurement of the drive shaft's speed.

[0017] Preferably, the first end protrudes from the transmission housing. The drive shaft thus protrudes through the transmission housing. Because the first end protrudes from the transmission housing, accessibility to the first end for speed measurement is further improved.

[0018] According to a preferred embodiment, the first end extends into a control unit of the actuating device. The control unit is preferably designed to determine the speed of the drive shaft based on a sensor signal from the speed sensor. Because the first end extends into the control unit, the signal connection of the speed sensor to the control unit can be implemented in a technically simple manner.

[0019] The braking system according to the invention is characterized by the features of claim 13 and the actuating device according to the invention. This also results in the aforementioned advantages. Further preferred features and combinations of features emerge from the above description and from the claims.

[0020] The invention is explained in more detail below with reference to the drawings.

[0021] Figure 1 is a sectional view of an actuating device for a braking system, Figure 2 is a further sectional view of the actuating device,

[0022] Figure 3 is a perspective view of a gear mechanism of the actuating device and

[0023] Figure 4 is a sectional view of a spindle gear of the transmission device.

[0024] Figure 1 shows a longitudinal section through an actuating device 1 for a braking system 2 of a motor vehicle (not shown in detail). The actuating device 1 has a displaceably mounted actuator element 3 or pressure element 3, which in this case is designed as a push rod 3. The actuator element 3 is displaceable along a displacement axis 4 in a first direction 5 and in a second direction 6 opposite the first direction 5. The displacement axis 4 corresponds to the longitudinal center axis of the actuator element 3.

[0025] The actuator element 3 is at least partially arranged in a gear housing 7 of the actuating device 1. In the present case, the gear housing 7 is a cylindrical extrusion profile 7. In this respect, the gear housing 7 has a circumferentially closed casing wall 8. The casing wall 8 forms or encloses an axial opening 9 of the gear housing 7, wherein the axial opening 9 forms a housing interior 10 of the gear housing 7. In the present case, the axial opening 9 has a circular cross-section. The actuator element 3 is arranged in the gear housing 7 or the housing interior 10 in such a way that the

[0026] Displacement axis 4 is aligned perpendicular to a cross-sectional area of ​​the gear housing 7.

[0027] A master brake cylinder 11 of the actuating device 1 is fixedly arranged on the transmission housing 7. In the present case, the master brake cylinder 11 is arranged on a first end face 12 of the casing wall 8. A first hydraulic piston 13 and a second hydraulic piston 14 are displaceably mounted in the master brake cylinder 11, namely in the first direction 5 and in the second direction 6. The master brake cylinder 11 has a plurality of hydraulic connections 15, 16. If the actuating device 1 is installed as intended in the braking system 2, the hydraulic connections 15, 16 are fluidly connected to slave cylinders of friction brake devices of the braking system 2. The friction brake devices can then be actuated by displacing the hydraulic pistons 13 and 14 in the first direction 5. The actuator element 3 is coupled to the hydraulic pistons 13 and 14 in such a way that the hydraulic pistons 13 and 14 can be displaced in the first direction 5 by the actuator element 3.The friction brake devices can therefore be actuated by moving the actuator element 3.

[0028] A housing plate 17 is also fixedly mounted on the transmission housing 7. In this case, the housing plate 17 is arranged on a second end face 18 of the casing wall 8, facing away from the first end face 12. The housing plate 17 at least partially closes the axial opening 9.

[0029] The actuating device 1 also has a drive unit 19. The design of the drive unit 19 is explained in more detail below with reference to Figure 2. Figure 2 shows a cross-section through the actuating device 1. The drive unit 19 has a motor housing 20 in which an electric machine 21 is arranged. An annular rotor 22 of the electric machine 21 is arranged in a rotationally fixed manner on a drive shaft 23, wherein the drive shaft 23 is rotatably mounted about a rotation axis 24. An annular stator 25 of the electric machine 21 is arranged fixedly on the motor housing 20 and radially encloses the rotor 22 with respect to the rotation axis 24. The motor housing 20 is fastened to the transmission housing 7. In the present case, this is achieved in that a motor housing flange 26 of the motor housing 20 is fastened to a transmission housing flange 28 of the transmission housing 7 by means of several fastening means 27.

[0030] The drive shaft 23 is coupled to the actuator element 3 by a gear mechanism 29 such that the actuator element 3 can be displaced by the electric machine 21. Figure 3 shows a perspective view of the gear mechanism 29, with the gear housing 7 omitted in Figure 3. As can be seen, for example, from Figure 1, the rotational axis 24 of the drive shaft 23 is aligned perpendicular to the displacement axis 4 of the actuator element 3. This enables a simple coupling of the drive shaft 23 to the actuator element 3 in terms of transmission technology.

[0031] The transmission device 29 has a worm gear 30. The worm gear 30 has a worm shaft 31 and a worm wheel 32. The worm shaft 31 is formed by the drive shaft 23, wherein the drive shaft 23 has a screw thread 33 for this purpose. The worm wheel 32 has external teeth 34 that mesh with the screw thread 33. The worm gear 30 is arranged in the transmission housing 7. The drive shaft 23 protrudes from the motor housing 20 and through a first opening 35 in the casing wall 8 into the transmission housing 7 such that the screw thread 33 is arranged in the transmission housing 7. The worm wheel 32 is arranged coaxially with the actuator element 3 in the housing interior 10. The rotational axis of the worm wheel 32 thus corresponds to the displacement axis 4 of the actuator element 3.

[0032] The transmission device 29 also has a further transmission 36 designed to convert a rotation into a translational movement. According to the exemplary embodiment illustrated in the figures, the further transmission 36 is designed as a spindle transmission 36. Figure 4 shows a longitudinal section of the actuating device 1 in the region of the spindle transmission 36. According to a further exemplary embodiment, the further transmission 36 is designed, for example, as a ball screw drive.

[0033] The spindle gear 36 has a rotatably mounted spindle nut 37 and a displaceably mounted threaded spindle 38. The spindle gear 36 is also arranged at least partially within the housing interior 10. The spindle nut 37 is arranged coaxially with the worm gear 32 and can be rotated by the worm gear 30. According to the exemplary embodiment illustrated in the figures, the spindle nut 37 and the worm gear 32 are manufactured as a single piece. According to a further exemplary embodiment, the worm gear 32 is arranged, for example, in a rotationally fixed manner on the spindle nut 37. The threaded spindle 38 is coupled to the actuator element 3 in such a way that the actuator element 3 can be displaced by the threaded spindle 38 at least in the first direction 5. In the present case, the threaded spindle 38 is arranged in an axial opening 61 in the housing plate 17. An anti-rotation structure 60 is attached to an end of the threaded spindle 38 facing the actuator element 3.The anti-rotation structure 60 cooperates with the gear housing 7 to support the threaded spindle 38.

[0034] The drive shaft 23 has a first end 39 on a side of the screw thread 33 facing away from the rotor 22. The first end 39 protrudes through a second opening 40 in the casing wall 8 out of the transmission housing 7. A speed sensor 41 is arranged at the first end 39. In the present case, the speed sensor 41 is pressed onto the first end 39. The first end 39 carrying the speed sensor 41 protrudes into a control unit 42 of the actuating device 1. The control unit 42 is designed to determine a speed of the drive shaft 23 depending on the sensor signal from the speed sensor 41 and to control the electric machine 21 depending on the determined speed. Because the first end 39 with the speed sensor 41 protrudes into the control unit 42, the sensor signal from the speed sensor 41 can be fed to the control unit 42 in a technically simple manner.

[0035] The drive shaft 23 has a first bearing 43. The first bearing 43 is located on the side of the screw thread 33 facing away from the rotor 22. In this case, the bearing 43 is located between the speed sensor 41 and the screw thread 33, adjacent to the speed sensor 41. The first bearing 43 is supported by the transmission housing 7. In this case, the transmission housing 7 carries a pivot bearing 44, which acts between the transmission housing 7 and the first bearing 43 of the drive shaft 23.

[0036] The drive shaft 23 also has a second bearing point 45. The second bearing point 45 is arranged between the screw thread 33 and the rotor 22. In the present case, the second bearing point 45 is supported by a bearing plate 46 arranged on the motor housing 20. For this purpose, the bearing plate 46 carries a pivot bearing 47, which acts between the drive shaft 23 on the one hand and the bearing plate 46 on the other. According to a further exemplary embodiment, the second bearing point 46 is also supported by the gear housing 7. The drive shaft 23 also has a third bearing point 48. The third bearing point 48 is arranged on a side of the rotor 22 facing away from the screw thread 33. In the present case, the third bearing point 48 is supported by a base 49 of the motor housing 20. For this purpose, the base 49 carries a pivot bearing 50, which acts between the base 49 and the drive shaft 23.

[0037] The actuating device 1 also has an actuating element 51, which is displaceably mounted in an axial opening 52 of the threaded spindle 38. A first end 53 of the actuating element 51 is

[0038] Input rod 54 is coupled or connectable to a brake pedal of the brake system 2, so that the actuating element 51 can then be displaced by actuating the brake pedal. A second end 55 of the actuating element 51 is coupled to the actuator element 3 such that the actuator element 3 can be displaced by the actuating element 51. The friction brake devices can therefore also be actuated by actuating the brake pedal.

Claims

Claims 1. Actuating device for a braking system, comprising an electric machine (21) arranged in a motor housing (20), wherein a rotor (22) of the electric machine (21) on a rotatably mounted drive shaft (23) is arranged in a rotationally fixed manner, and with a slidably mounted actuator element (3), wherein the drive shaft (23) is coupled to the actuator element (3) by a gear unit (29) such that the actuator element (3) is displaceable by the electric machine (21), wherein the gear unit (29) has a worm gear (30) with a worm shaft (31) and a worm wheel (32), and wherein the drive shaft (23) forms the worm shaft (31), characterized in that a rotation axis (24) of the drive shaft (23) is perpendicular to a displacement axis (4) of the actuator element (3) is aligned.

2. Actuating device according to claim 1, characterized in that the gear unit (29) has a spindle gear (36) connected downstream of the worm gear (30) in terms of gear technology.

3. Actuating device according to claim 1, characterized in that the transmission device (29) has a ball screw drive connected downstream of the worm gear (30) in terms of transmission technology.

4. Actuating device according to one of the preceding claims, characterized in that the transmission device (29) is at least partially arranged in a transmission housing (7) of the actuating device (1), and that the motor housing (20) is attached to the transmission housing (7), in particular by at least one fastening means (27).

5. Actuating device according to claim 4, characterized in that the motor housing (20) is attached to a gearbox housing flange (28) of the gearbox housing (7).

6. Actuating device according to one of claims 4 and 5, characterized in that the gearbox housing (7) is a cylindrical extrusion profile (7).

7. Actuating device according to claim 6, characterized in that the displacement axis (4) of the actuator element (3) is aligned perpendicular to a cross-sectional area of ​​the extrusion profile (7).

8. Actuating device according to one of claims 4 to 7, characterized in that at least one first bearing point (43) of the drive shaft (23) is supported by the gearbox housing (7).

9. Actuating device according to claim 8, characterized in that the drive shaft (23) has a screw thread (33) and the first bearing point (43) is arranged on a side of the screw thread (33) facing away from the rotor (22).

10. Actuating device according to one of the preceding claims, characterized in that the drive shaft (23) has a first end (39) on the side of the screw thread (33) facing away from the rotor (22), and that a speed sensor (41) is arranged at the first end (39).

11. Actuating device according to claim 10, characterized in that the first end (39) protrudes from the gearbox housing (7).

12. Actuating device according to one of claims 10 and 11, characterized in that the first end (39) projects into a control unit (42) of the actuating device (1).

13. Braking system, characterized by an actuating device (1) according to one of the preceding claims.

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