ACTUATOR FOR A BRAKE SYSTEM

Description

[0001] The invention relates to an actuating device for a brake system, comprising an electric motor designed to drive a drive shaft mounted rotatably about a rotational axis, comprising a housing, and comprising a master brake cylinder rigidly connected to the housing, wherein at least one hydraulic piston is displaceably mounted in the master brake cylinder, and wherein the drive shaft is coupled to the hydraulic piston in such a way that the hydraulic piston is displaceable by rotation of the drive shaft.

[0002] Furthermore, the invention relates to a braking system with such an actuating device. State of the art

[0003] A motor vehicle's hydraulic brake system typically includes multiple friction brake devices. To actuate the friction brake devices, an actuating device is typically provided with a master brake cylinder in which at least one hydraulic piston is displaceably mounted. The master brake cylinder is fluidly connected to the slave cylinders of the friction brake devices in such a way that the friction brake devices can be actuated by moving the hydraulic piston.

[0004] Electromechanical actuating devices are being installed more and more frequently in motor vehicles. One such actuating device is known, for example, from published patent application WO 2017 108 228 A1. The actuating device has an electric motor designed to drive a drive shaft mounted for rotation about a rotational axis. The drive shaft is coupled to the hydraulic piston in such a way that the hydraulic piston can be displaced by rotation of the drive shaft. The hydraulic piston can therefore be displaced by the electric motor via the drive shaft, so that the friction brake devices can ultimately be actuated by the electric motor. The actuating device also has a housing, with the master brake cylinder being rigidly connected to the housing. Typically, in previously known electromechanical actuating devices, the electric motor is arranged outside the housing, to which the master brake cylinder is rigidly connected.

[0005] The disclosure DE 10 2016 113802 A1 relates to a power assist system including a motor with a rotor shaft, a drive pulley mounted on the rotor shaft, a driven pulley, a flexible belt configured to connect the drive pulley to the driven pulley, and a ball screw assembly. The ball screw assembly includes a rotatable ball screw rotatable together with the driven pulley, a linear transmission ball screw nut surrounding the ball screw, and an anti-rotation device arranged to prevent rotation of the ball screw nut. Disclosure of the invention

[0006] The actuating device according to the invention with the features of claim 1 has the advantage that the actuating device is particularly compact and thus space-saving. According to the invention, the electric motor is arranged in the housing, and the rigid connection of the master brake cylinder to the housing is provided at least partially by the drive shaft. According to the invention, the electric motor is therefore arranged in the housing to which the master brake cylinder is rigidly connected. Due to the arrangement in the housing, the electric motor is protected by the housing, so that an additional motor housing is unnecessary. The electric motor is preferably designed without a motor housing. This not only saves installation space for the actuating device, but also saves costs.

[0007] According to the invention, the master brake cylinder is rigidly connected to the housing or rigidly attached to the housing. A rigid connection between two bodies is understood to mean a connection that does not permit any relative movement of the bodies to one another. In this respect, the rigid connection of the master brake cylinder to the housing is designed, for example, to transmit both axial forces and radial forces. If the terms "axial" and "radial" are used in the disclosure, these terms refer to the axis of rotation of the drive shaft, unless a different reference for the terms is expressly disclosed. An axial force is therefore understood to be a force that is aligned parallel to the axis of rotation. A radial force is understood to be a force that is aligned perpendicular to the axis of rotation.Preferably, the hydraulic piston is displaceable along a displacement axis that is aligned parallel to the rotational axis of the drive shaft. According to the invention, the rigid connection of the housing to the master brake cylinder is at least partially provided or effected by the drive shaft. If, for example, the master brake cylinder is subjected to an axial force, this axial force is at least partially transmitted to the housing by means of the drive shaft. Because the rigid connection of the housing to the master brake cylinder is at least partially provided by the drive shaft, other elements can be omitted which usually partially provide the rigid connection in previously known actuating devices. This also results in the space-saving design of the actuating device according to the invention.

[0008] The actuating device preferably has a first bearing designed to transmit axial forces, which first bearing has a first bearing ring and a second bearing ring, the first bearing ring being rigidly connected to the master brake cylinder and the second bearing ring being rigidly connected to the drive shaft. The rigid connection of the housing to the master brake cylinder is therefore at least partially provided by the first bearing. If the master brake cylinder is subjected to an axial force, this axial force is transmitted to the drive shaft by means of the first bearing ring and the second bearing ring. By means of the first bearing, sufficiently high axial forces can be transmitted to the drive shaft despite the rotatable mounting of the drive shaft. The first bearing ring is preferably an outer bearing ring of the first bearing. Accordingly, the second bearing ring is then an inner bearing ring of the first bearing.Preferably, the second bearing ring is connected to the drive shaft by a press fit. Preferably, the second bearing ring is connected to a first end portion of the drive shaft. Particularly preferably, the first bearing is arranged outside the housing. Accordingly, the drive shaft has a portion that protrudes from the housing.

[0009] The actuating device preferably has a second bearing designed to transmit axial forces, which second bearing has a third bearing ring and a fourth bearing ring, wherein the third bearing ring is arranged fixedly to the housing, and wherein the fourth bearing ring is rigidly connected to the drive shaft. The rigid connection of the housing to the master brake cylinder is therefore provided at least partially by the second bearing. If the drive shaft is subjected to an axial force, this axial force is transmitted to the housing by means of the fourth bearing ring and the third bearing ring. By means of the second bearing, sufficiently high axial forces can be transmitted from the drive shaft to the housing despite the rotatable bearing of the drive shaft. The third bearing ring is preferably an outer bearing ring of the second bearing. Accordingly, the fourth bearing ring is then an inner bearing ring of the second bearing.Preferably, the fourth bearing ring is connected to the drive shaft by a press fit. Preferably, the fourth bearing ring is connected to a second end section of the drive shaft. If the first bearing is connected to the drive shaft in the region of the first end section of the drive shaft and the second bearing is connected to the second end section of the drive shaft, the electric motor is arranged axially between the first bearing on the one hand and the second bearing on the other hand. This ensures stable, rotatable support of the drive shaft by means of the two bearings.

[0010] According to a preferred embodiment, the first bearing and / or the second bearing are designed as rolling element bearings, in particular tapered roller bearings. Such bearings enable low-friction rotation of the drive shaft. Furthermore, such bearings can transmit sufficiently high axial forces. With regard to the transmission of high axial forces, the design of the bearings as tapered roller bearings is particularly advantageous.

[0011] The housing preferably has a cup-shaped recess, with the second bearing arranged in the recess. By providing the recess and arranging the second bearing in the recess, a particularly stable connection between the third bearing ring and the housing can be achieved. Preferably, the third bearing ring is pressed into the recess. The third bearing ring is thus connected to the housing by a press fit acting between a shell wall of the recess and a shell wall of the third bearing ring.

[0012] The master brake cylinder preferably has a connecting flange, with the first bearing ring being rigidly connected to the connecting flange. The connecting flange can provide a stable connection between the master brake cylinder and the housing. The connecting flange preferably has an axial opening in which the first bearing is arranged. The first bearing ring is preferably connected to the connecting flange by a press fit acting between a jacket wall of the axial opening and a jacket wall of the first bearing ring.

[0013] The actuating device preferably has a control unit for controlling the electric motor, wherein the connecting flange is arranged axially between the electric motor on the one hand and the control unit on the other. This arrangement of the control unit is particularly advantageous. Firstly, with such an arrangement, the control unit is located in spatial proximity to the electric motor, whereby an electrical connection of the control unit to the electric motor is technically simple. Secondly, due to the spatial proximity to the connecting flange, the control unit is cooled or cooled by the connecting flange during operation. Preferably, the control unit, in particular a control unit housing of the control unit, lies axially directly against the connecting flange.

[0014] According to a preferred embodiment, the control unit is electrically connected to a motor winding of the electric motor by at least one electrical line, wherein the connecting flange has an axial opening through which the line extends. The line thus runs through the connecting flange. As a result, the line is protected by the connecting flange, and the electrical connection of the control unit to the motor winding is simplified in that the line does not have to be routed around the connecting flange.

[0015] The actuating device preferably has at least one retaining ring which engages radially in a circumferential groove of the drive shaft to axially secure the drive shaft. This increases the level of axial forces that can be transmitted by the drive shaft. The retaining ring preferably lies axially directly on the second bearing ring of the first bearing or the fourth bearing ring of the second bearing. Particularly preferably, the retaining ring is arranged on a side of the first bearing facing away from the second bearing and lies axially directly on the second bearing ring of the first bearing. The actuating device then preferably has a further retaining ring which, for axially securing the drive shaft, engages radially in a further circumferential groove of the drive shaft, is arranged on a side of the second bearing facing away from the first bearing and lies axially directly on the fourth bearing ring of the second bearing.

[0016] The actuating device preferably comprises an actuating element that is displaceably guided in the housing, with the actuating element being guided at least partially by the electric motor. The actuating element is understood to be an element that is coupled to the hydraulic piston in such a way that the hydraulic piston can be displaced by a displacement of the actuating element. Preferably, the drive shaft is coupled to the hydraulic piston by means of the actuating element. Because the actuating element is guided at least partially by the electric motor, only a small number of other components are required to guide the actuating element.

[0017] The actuating device preferably has an anti-rotation plate rigidly connected to the actuating element, wherein a housing-fixed element of the electric motor has a guide projection that engages radially in a recess of the anti-rotation plate to guide the actuating element. This ensures secure guidance of the actuating element. The guide projection preferably has a coating that reduces friction between the guide projection and the anti-rotation plate. According to a further embodiment, the anti-rotation plate has a guide projection that engages radially in a recess of the housing-fixed element of the electric motor to guide the actuating element.

[0018] The actuating device preferably comprises a pull rod, wherein the rigid connection of the housing to the master brake cylinder and the guidance of the actuating element are each provided in part by the pull rod. The provision of the pull rod increases the stability of the rigid connection of the housing to the master brake cylinder and the stability of the guidance of the actuating element. The actuating device preferably comprises precisely one pull rod configured as described above.

[0019] According to a preferred embodiment, a longitudinal center axis of the master brake cylinder, a longitudinal center axis of the pull rod, and the rotational axis of the drive shaft are aligned parallel to one another and lie in the same plane, with the master brake cylinder being arranged radially between the pull rod on the one hand and the drive shaft on the other. Such a configuration advantageously distributes axial forces acting on the master brake cylinder between the pull rod and the drive shaft.

[0020] The brake system according to the invention is characterized by the features of claim 14 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 description and the claims. The brake system preferably has at least one friction brake device that is fluidly connected to the master brake cylinder in such a way that the friction brake device can be actuated by a displacement of the hydraulic piston.

[0021] The invention is explained in more detail below with reference to the drawings. Figure 1 shows a sectional view of an actuating device for a braking system and Figure 2 shows a plan view of the actuating device.

[0022] Figure 1shows a sectional view of an actuating device 1 for a hydraulic brake system of a motor vehicle. The actuating device 1 has a master brake cylinder 2. In the master brake cylinder 2, at least one hydraulic piston (not shown) is mounted axially displaceably along a displacement axis 3. In the present case, the master brake cylinder 2 is a tandem master brake cylinder 2. Accordingly, two hydraulic pistons are mounted axially displaceably one behind the other in the master brake cylinder 2. The displacement axis 3 corresponds to the longitudinal center axis 3 of the master brake cylinder 2. If the actuating device 1 is mounted as part of the brake system in the motor vehicle, the master brake cylinder 2 is connected to the hydraulic system by a plurality of hydraulic connections, of which Figure 1only a single hydraulic connection 4 is shown, is connected to slave cylinders of friction brake devices of the brake system in such a way that the friction brake devices can be actuated by a displacement of the hydraulic pistons in an actuating device 5.

[0023] The actuating device 1 also has a housing 6. The housing 6 is constructed in several parts. In the present case, the housing 6 has a base body 7 and a cover 8. The base body 7 and the cover 8 are rigidly connected to one another by fastening means 9.

[0024] The actuating device 1 also has an electric motor 10, which is arranged in the housing 6 so as to be fixed to the housing. The electric motor 10 is designed to drive a drive shaft 11, which is mounted for rotation about a rotation axis 12. The rotation axis 12 is aligned parallel to the displacement axis 3. The drive shaft 11 projects axially beyond the electric motor 10 on both sides. In this respect, the drive shaft 11 has a first end section 13, which is arranged axially on one side of the electric motor 10, and a second end section 14, which is arranged axially on the other side of the electric motor 10. A first bearing 15 and a second bearing 16 are provided for the rotatable mounting of the drive shaft 11. The first bearing 15 supports the first end section 13 of the drive shaft 11. The second bearing 16 supports the second end section 14 of the drive shaft 11. In this case, the bearings 15 and 16 are designed as rolling element bearings 15 and 16.

[0025] The master brake cylinder 2 has a connecting flange 17. The connecting flange 17 rests axially on an outer side of a wall 18 of the cover 8, which is oriented perpendicular to the rotation axis 12. The master brake cylinder 2 is rigidly connected to the housing 6 or rigidly fastened to the housing. Thus, a connection exists between the master brake cylinder 2 on the one hand and the housing 6 on the other, through which both axial and radial forces can be transmitted. For example, if the master brake cylinder 2 is subjected to an axial force acting in the actuation direction 5, this axial force is transmitted to the housing 6.

[0026] The rigid connection of the master brake cylinder 2 to the housing 6 is provided partially by the drive shaft 11. The first bearing 15 and the second bearing 16 are designed to transmit both axial forces and radial forces. For this purpose, the first bearing 15 has a first bearing ring 19 and a second bearing ring 20, wherein the bearing rings 19 and 20 are rotatable relative to one another. The first bearing ring 19 is rigidly connected to the master brake cylinder 2. In the present case, the first bearing ring 19 is pressed into a first axial opening 21 in the connecting flange 17. The second bearing ring 20 is rigidly connected to the drive shaft 11. In the present case, the drive shaft 11 is pressed into the second bearing ring 20. The second bearing 16 has a third bearing ring 22 and a fourth bearing ring 23, wherein the bearing rings 22 and 23 are rotatable relative to one another. The third bearing ring 22 is rigidly connected to the housing 6.In this case, the third bearing ring 22 is pressed into a cup-shaped recess 24 in the base body 7 of the housing 6. The fourth bearing ring 23 is rigidly connected to the drive shaft 11. In this case, the drive shaft 11 is pressed into the fourth bearing ring 23. Thus, if the master brake cylinder 2 is subjected to an axial force acting in the actuating device 5, this axial force is transmitted to the housing 6 through the first bearing ring 19, the second bearing ring 20, the drive shaft 11, the fourth bearing ring 23, and the third bearing ring 22.

[0027] The actuating device 1 also has a pull rod 25. The pull rod 25 is arranged such that a longitudinal center axis 26 of the pull rod 25 is aligned parallel to the rotation axis 12. The rigid connection of the master brake cylinder 2 to the housing 6 is also partially provided by the pull rod 25. For this purpose, the pull rod 25 extends axially through the housing 6 and the connecting flange 17 and is axially fixed to the housing 6 and the connecting flange 17 by axial stops 27.

[0028] The actuating device 1 also has an axially displaceably guided actuating element 28. The actuating element 28 is coupled to the hydraulic pistons in such a way that the hydraulic pistons can be displaced by a displacement of the actuating element 28. A rotation-locking plate 29 is rigidly connected to the actuating element 28 and can therefore be displaced with the actuating element 28. Furthermore, the actuating device 1 has a return spring 30, which is axially supported on the master brake cylinder 2 on the one hand and on the actuating element 28 or an element rigidly connected to the actuating element 28 on the other.

[0029] The drive shaft 11 is operatively connected to the actuating element 28 such that the actuating element 28 is displaceable by rotation of the drive shaft 11. In this respect, the hydraulic pistons are displaceable by the electric motor 10. For this purpose, the actuating device 1 has a transmission device 31. The transmission device 31 has a first gear 32 which is connected in a rotationally fixed manner to the drive shaft 11. The first gear 32 is arranged axially between the electric motor 10 on the one hand and the second bearing 16 on the other. The first gear 32 is designed to drive a spindle nut 34 of the transmission device 31 by means of at least one further gear 33 of the transmission device 31. An external thread of the actuating element 28 meshes with an internal thread of the spindle nut 34 such that the actuating element 28 is displaceable by rotation of the spindle nut 34.

[0030] The guidance of the actuating element 28 is provided in part by the electric motor 10. In the present case, an element of the electric motor 10 that is fixed to the housing, for example a carrier of the electric motor 10, has a guide projection 35 that extends in the axial direction. The anti-rotation plate 29 has a recess 36 that extends axially through the anti-rotation plate 29. The guide projection 35 engages radially in the recess 36 to guide the actuating element 28. The guide projection 35 has a Figure 1 a coating (not shown) which reduces friction between the guide projection 35 and the anti-rotation plate 29. According to a further exemplary embodiment, the anti-rotation plate 29 has a guide projection which engages radially in a recess of the electric motor 10 extending in the axial direction to guide the actuating element 28.

[0031] The guide of the actuating element 28 is also provided in part by the pull rod 25. For this purpose, the anti-rotation plate 29 has an axial opening 37 through which the pull rod 25 extends axially to guide the actuating element 28.

[0032] The actuating device 1 also has a control unit 38 for controlling the electric motor 10. For example, the control unit 38 is designed to control the electric motor 10 depending on a sensor signal from an actuation sensor (not shown) of the actuating device 1. The connecting flange 17 is arranged axially between the electric motor 10 on the one hand and the control unit 38 on the other. The control unit 38 rests axially directly on the connecting flange 17.

[0033] The connecting flange 17 has a second axial opening 39, which is axially aligned with an axial opening 41 in the cover 8. The control unit 38 is electrically connected to a motor winding of the electric motor 10 via several electrical lines 40. The electrical lines 40 extend through the second axial opening 39 of the connecting flange 17 and through the axial opening 41 in the cover 8.

[0034] To monitor the rotation angle of the drive shaft 11, a magnetic element 42 is provided, which is rotationally fixedly connected to a free end of the first end section 13 of the drive shaft 11. A receiver (not shown) is also provided, which is designed to detect a magnetic field generated by the magnetic element 42. For this purpose, the receiver is located radially or axially opposite the magnetic element 42, for example.

[0035] In order to axially secure the drive shaft 11, a retaining ring 43 is provided. The retaining ring 43 engages radially in a circumferential groove of the drive shaft 11. The retaining ring 43 is arranged axially between the magnetic element 42 on the one hand and the first bearing 15 on the other hand and axially bears directly on the second bearing ring 20. According to a further exemplary embodiment, the drive shaft 11 projects axially beyond the second bearing 16. According to this exemplary embodiment, a further retaining ring is preferably provided, which is arranged on a side of the second bearing 16 facing away from the first bearing 15 and axially bears directly on the fourth bearing ring 23. The further retaining ring preferably engages radially in a further circumferential groove of the drive shaft 11.

[0036] Figure 2 shows a top view of the actuating device 1. As can be seen from Figure 2As can be seen, the master brake cylinder 2, the pull rod 25 and the drive shaft 11 are arranged such that the longitudinal center axis 26 of the pull rod 25, the longitudinal center axis 3 of the master brake cylinder 2 and the rotational axis 12 of the drive shaft 11 lie in the same plane. The master brake cylinder 2 is arranged radially between the pull rod 25 and the drive shaft 11. In addition, the longitudinal center axis 26 of the pull rod 25 and the rotational axis 12 of the drive shaft 11 are equidistant in the radial direction from the longitudinal center axis 3 of the master brake cylinder 2.

[0037] Because the drive shaft 11 partially provides the rigid connection of the master brake cylinder 2 to the housing 6, and because the electric motor 10 partially provides the guidance of the actuating element 28, an additional pull rod can be dispensed with, which would typically provide the rigid connection and guidance together with the pull rod 25. As a result, the actuating device 1 is designed to save overall installation space, as can be seen from Figure 2 is evident.

Claims

1. Actuating device (1) for a brake system, comprising an electric motor (10) which is designed to drive a drive shaft (11) which is mounted so as to be rotatable about an axis of rotation (12), a housing (6) and a master brake cylinder (2) which is rigidly connected to the housing (6), wherein at least one hydraulic piston is mounted so as to be displaceable in the master brake cylinder (2), and wherein the drive shaft (11) is coupled to the hydraulic piston in such a way that the hydraulic piston can be displaced by a rotation of the drive shaft (11), wherein the electric motor (10) is arranged in the housing (6), characterized in that the rigid connection between the master brake cylinder (2) and the housing (6) is provided at least in part by the drive shaft (11).

2. Actuating device according to Claim 1, characterized by a first bearing (15) designed for transmitting axial forces, which comprises a first bearing ring (19) and a second being ring (20), wherein the first bearing ring (19) is rigidly connected to the master brake cylinder (2), and wherein the second bearing ring (20) is rigidly connected to the drive shaft (11).

3. Actuating device according to either of the preceding claims, characterized by a second bearing (16) designed for transmitting axial forces, which comprises a third bearing ring (22) and a fourth bearing ring (23), wherein the third bearing ring (22) is arranged fixed to the housing, and wherein the fourth bearing ring (23) is rigidly connected to the drive shaft (11).

4. Actuating device according to either of Claims 2 and 3, characterized in that the first bearing (15) and / or the second bearing (16) are formed as rolling element bearings, in particular tapered roller bearings.

5. Actuating device according to one of Claims 2 to 4, characterized in that the housing (6) has a cup-shaped recess (24), wherein the second bearing (16) is arranged in the recess (24).

6. Actuating device according to one of Claims 2 to 5, characterized in that the master brake cylinder (2) has a connection flange (17), and in that the first bearing ring (19) is rigidly connected to the connection flange (17).

7. Actuating device according to one of the preceding claims, characterized by a control unit (38) for controlling the electric motor (10), wherein the connection flange (17) is arranged axially between the electric motor (10) on the one hand and the control unit (38) on the other hand.

8. Actuating device according to Claim 7, characterized in that the control unit (38) is electrically connected to a motor winding of the electric motor (10) by at least one electrical line (40), wherein the connection flange (17) has an axial aperture (39) through which the line (40) extends.

9. Actuating device according to one of the preceding claims, characterized by at least one securing ring (43) which engages radially in a circumferential groove of the drive shaft (11) in order to axially secure the drive shaft (11).

10. Actuating device according to one of the preceding claims, characterized by an actuating element (28) which is guided so as to be displaceable in the housing (6), wherein the guiding of the actuating element (28) is provided at least in part by the electric motor (10).

11. Actuating device according to Claim 10, characterized by an anti-rotation plate (29) which is rigidly connected to the actuating element (28), wherein an element of the electric motor (10) that is fixed to the housing has a guide projection (35) which engages in a cutout (36) of the anti-rotation plate (29) in order to guide the actuating element (28).

12. Actuating device according to one of the preceding claims, characterized in that the actuating device (1) has a tie rod (25), wherein the rigid connection of the housing (6) to the master brake cylinder (2) and the guiding of the actuating element (28) are each provided in part by the tie rod (25).

13. Actuating device according to Claim 12, characterized in that a longitudinal centre axis (3) of the master brake cylinder (2), a longitudinal centre axis (26) of the tie rod (25) and the axis of rotation (12) of the drive shaft (11) are oriented parallel to one another and lie in the same plane, wherein the master brake cylinder (2) is arranged radially between the tie rod (25) on the one hand and the drive shaft (11) on the other hand.

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