Brake actuator for a motor vehicle, and motor vehicle

Abstract

The invention relates to a brake actuator (1) for a motor vehicle and also to a motor vehicle with such a brake actuator (1). The brake actuator (1) comprises: a drive device (10) having a motor housing (11) and a drive shaft (12) protruding from the motor housing (11); an anti-friction bearing (13) which has an inner ring (13a) and an outer ring (13b), wherein the anti-friction bearing (13) is arranged on the motor housing (11) and is designed to mount the drive shaft (12); and a housing (4) which adjoins the motor housing (11) in the region of the anti-friction bearing (13), wherein the drive shaft (12) at least partially penetrates the housing (4), wherein the outer ring (13b) of the anti-friction bearing (13) is arranged between the housing (4) and the motor housing (11) in such a way that the outer ring (13b) is mounted in a form-fitting manner in an axial direction (X) of the drive shaft (12).

Description

[0001] R. 418401

[0002] - 1 -

[0003] Description

[0004] title

[0005] Brake actuator for a motor vehicle and motor vehicle

[0006] The present invention relates to a brake actuator for a motor vehicle and a motor vehicle with such a brake actuator.

[0007] State of the art

[0008] A service brake is typically a brake system that uses brake fluid to press a brake piston, along with a brake pad, against a brake disc to slow the vehicle. Brake boosters or brake actuators can be used to actuate the brake piston.

[0009] In known designs, the ball bearing on the outer ring can be fixed in a bearing shield of the motor by means of an interference fit. The centering of the motor to a brake booster housing is usually achieved via the outer diameter of the

[0010] Ball bearing. The bearing shield is axially supported by the HU housing. Due to the known design, the bearing shield is pre-tensioned during assembly; in particular, the

[0011] The pocket in the HU housing for the bearing shield ring on the ball bearing is practically not deep enough to prevent axial forces acting on the motor shaft from causing a displacement of the ball bearing.

[0012] For example, EP 3350041 A1 describes an electromechanical brake booster for a motor vehicle, wherein at least one support element is attached to a gearbox housing base of the gearbox, which is substantially parallel to an adjustment axis of the spindle R. 418401

[0013] - 2 -

[0014] extends, wherein a sheet metal sleeve with an annular groove is pressed onto a ball bearing outer ring, wherein the ball bearing can be pulled out of the hole if the press fit of the sheet metal sleeve does not prevent this.

[0015] Furthermore, other bearing options are known for use in a brake booster. For example, EP 1 426645 A1 describes an electromechanical brake actuator, in which the axial fixing of the inner and outer rings of the ball bearings is achieved in a conventional manner by suitably designed shoulders of the housing or the spindle nut and by clamping rings or snap rings.

[0016] Disclosure of the invention

[0017] The invention provides a brake actuator for a motor vehicle with the features of claim 1 and a motor vehicle with the features of claim 8.

[0018] According to a first aspect of the invention, a brake actuator for a motor vehicle is provided. The brake actuator comprises a drive unit with a motor housing and a drive shaft projecting from the motor housing. Furthermore, the brake actuator includes a rolling bearing having an inner ring and an outer ring. The rolling bearing is arranged on the motor housing and is designed to support the drive shaft. The brake actuator also includes a housing that adjoins the motor housing in the area of ​​the rolling bearing. The drive shaft at least partially penetrates the housing. The outer ring of the rolling bearing is arranged between the housing and the motor housing such that the outer ring is positively locked in an axial direction of the drive shaft.

[0019] According to a second aspect of the invention, a motor vehicle is provided with a brake actuator according to the first aspect of the invention.

[0020] One of the underlying ideas of the present invention is to support the rolling bearing axially on the motor housing, so that axial forces do not have to be supported exclusively via a radial press fit. That is to say, R. 418401

[0021] - 3 -

[0022] Instead of fixing the rolling bearing in the housing only by means of the radial press fit, an axial stop is provided in the housing.

[0023] The drive mechanism allows a piston to be axially displaceable. The piston can actuate an associated hydraulic system or a mechanical mechanism.

[0024] An advantage of the present invention is that axial forces from the drive shaft or motor shaft can be transmitted directly to the housing. Consequently, the load-bearing capacity in the axial direction is limited by the mechanical properties of the components, in particular the rolling bearing and the motor housing, and not by the radial press fit. Furthermore, the stability of the bearing arrangement of the rolling bearing in conjunction with the housing and the motor housing can be better controlled, since these components are easier to assemble in the brake actuator according to the invention.

[0025] Furthermore, the tolerance chain between the housing and the drive shaft is shorter, as the tolerance for positioning the rolling bearing in the housing can be eliminated. This is advantageous, for example, for the tolerance chain between a rotor position magnet mounted on the other side of the drive shaft and the rotor position sensor in a brake actuator control unit, which is mounted on the housing.

[0026] is attached.

[0027] For example, the brake actuator can be electromechanical or designed as a so-called brake-by-wire system.

[0028] Advantageous designs and further developments result from the further sub-claims as well as from the description with reference to the figures in the drawing.

[0029] According to a further development of the invention, the outer ring of the rolling bearing is pressed axially between the housing and the motor housing. The housing can thus be axially supported via the rolling bearing, in particular via the outer ring, instead of directly via the motor housing. R. 418401

[0030] - 4 -

[0031] According to a further embodiment of the invention, the motor housing has a shoulder directed inwards, in which the rolling bearing is arranged. The shoulder can form a kind of support shoulder for the outer ring. In particular, the shoulder can form a stepped section of the motor housing. For example, the shoulder can be formed partially or completely around the drive shaft.

[0032] According to a further embodiment of the invention, the shoulder device is radially in contact with the outer ring and has an axial stop for the outer ring, wherein the axial stop is arranged offset inwards with respect to the motor housing.

[0033] Optionally, the housing can have an inward-facing stepped arrangement in which the rolling bearing is located. The stepped arrangement can form a kind of support shoulder for the outer ring.

[0034] In particular, the stepped assembly can form a stepped section of the housing. For example, the stepped assembly can be formed partially or completely around the drive shaft. Furthermore, the stepped assembly can have an axial stop for the outer ring, wherein the axial stop of the housing is arranged offset inwards with respect to the housing.

[0035] According to a further embodiment of the invention, a predetermined radial pressure is also present between the rolling bearing and the motor housing. This predetermined pressure or preload can be selected such that axial forces from the drive shaft do not cause the rolling bearing to lift off, and conversely, that the screws for fastening the motor housing to the housing are not overloaded or that the permissible surface pressure between the outer ring and the motor housing is not exceeded. For example, the predetermined pressure can act radially between the shoulder and the outer ring.

[0036] According to a further embodiment of the invention, the rolling bearing is designed as a ball bearing, a four-point contact bearing, a tapered roller bearing, a spherical roller bearing, or R. 418401

[0037] - 5 -

[0038] Designed as a ball roller bearing, the rolling bearing can advantageously withstand loads in both the radial and axial directions. For example, the type of rolling bearing can be selected based on the maximum axial force it can withstand.

[0039] For example, the motor housing may have a bearing shield that supports the rolling bearing. The bearing shield may also include the shoulder assembly. The bearing shield is, in particular, a part of the motor housing. Furthermore, the housing and the bearing shield may be axially supported by the outer ring of the rolling bearing.

[0040] The drive unit can be an electric motor. The drive shaft can, for example, be designed as a worm shaft.

[0041] The housing can also be referred to as a hydraulic housing or a mechanical housing.

[0042] Brief description of the drawings

[0043] The invention will now be explained with reference to the figures in the drawings. The figures show:

[0044] Fig. 1 shows a perspective view of a brake-by-wire brake actuator for a motor vehicle according to an embodiment of the invention;

[0045] Fig. 2 shows a sectional view of the drive unit where the housing is adjacent; and

[0046] Fig. 3 shows an enlarged view of the rolling bearing from Fig. 2 in a mounted state.

[0047] In the figures, the same reference symbols denote identical or functionally equivalent components, unless otherwise stated.

[0048] Description of the exemplary embodiments R. 418401

[0049] - 6 -

[0050] Further advantages, features and details of the invention will become apparent from the following description, in which various embodiments are described in detail with reference to the drawing.

[0051] Fig. 1 shows a perspective view of a brake-by-wire brake actuator 1 for a motor vehicle according to an embodiment of the invention.

[0052] In so-called brake-by-wire systems, where a control signal is generated by actuating a brake pedal or in another way and an electro-hydraulic actuator is actuated based on the control signal to generate the brake pressure, the brake-by-wire brake actuator 1 is used.

[0053] The brake-by-wire brake actuator 1 includes, by way of example, a drive unit 10 connected to a housing 4. A gear unit 3 arranged in the housing 4 can be driven via the drive unit 10. A primary piston 2 of a tandem master cylinder 7, also provided in the housing 4, is operatively connected to the gear unit 3, so that when the drive unit 10 is driven, the primary piston 2 can be axially displaced to actuate the tandem master cylinder 7. The drive unit 10 comprises a motor housing 11 and a drive shaft (not shown) projecting from the motor housing 11. The drive shaft at least partially penetrates the housing 4. The housing 4 can also be referred to as a hydraulic housing or a mechanical housing. In particular, the rotary motion of the drive shaft is converted by the gear unit 3 into an axial motion, which moves the primary piston 2 of the tandem master cylinder 7 via a pushrod receptacle 8 and a pushrod.The gear unit 3 can have a worm gear that is driven by the drive shaft.

[0054] A control unit 20 is arranged on the side of the housing 4 facing away from the drive unit 10. The drive unit 10 can be controlled via this control unit 20. The drive unit 10 can be an electric motor. As shown in Fig. 1, the control unit 20 is arranged opposite the motor housing 11 with respect to the drive shaft. R. 418401

[0055] - 7 -

[0056] In a brake-by-wire system, the clamping force of the brake calipers is not applied directly via the brake pedal, but rather via one or more electro-hydraulic or electromechanical actuators. In such a system, the brake pedal has no direct mechanical or hydraulic connection to the wheel brakes. The brake pedal actuation merely serves as input information for the control unit 20.

[0057] The brake-by-wire brake actuator 1 further comprises a rolling bearing (not shown) having an inner ring and an outer ring. The rolling bearing is arranged on the motor housing 11 and is designed to support the drive shaft, as can be seen below in Fig. 2. The outer ring of the rolling bearing is arranged between the housing 4 and the motor housing 11 such that the outer ring is positively locked in one axial direction of the drive shaft.

[0058] Fig. 2 shows a sectional view of the drive unit 10 to which the housing 4 is attached.

[0059] The drive unit 10 comprises a motor housing 11 and a drive shaft 12 projecting from the motor housing 11. By way of example, the motor housing 11 here has a bearing shield 11a, which is part of the motor housing 11 and supports a rolling bearing 13. The bearing shield 11a can also include a shoulder 14.

[0060] The rolling bearing 13 comprises an inner ring 13a and an outer ring 13b. The rolling bearing 13 is arranged on the motor housing 11, in particular in the shoulder assembly 14. The rolling bearing 13 supports the drive shaft 12 of the drive assembly 10.

[0061] The shoulder 14 is shown directed into the interior of the motor housing 11. The shoulder 14 can form a type of support shoulder for the outer ring 13b. In particular, the shoulder 14 can form a stepped section of the motor housing 11. For example, R. 418401

[0062] - 8 -

[0063] The offset device 14 may be formed partially or completely around the drive shaft 12.

[0064] In particular, the shoulder device 14 can be radially in contact with the outer ring 13b and have an axial stop 15 for the outer ring 13b. As illustrated in Fig. 2, the axial stop 15 can be arranged offset inwards, i.e. downwards, with respect to the motor housing 11.

[0065] Furthermore, a predetermined pressure in a radial direction can be applied between the rolling bearing 13 and the motor housing 11. The predetermined pressure or preload can be selected such that axial forces from the drive shaft 12 do not cause the rolling bearing 13 to lift off (minimum required preload) and, on the other hand, that the screws for fastening the motor housing 11 to the housing 4 are not overloaded or that the permissible surface pressure between the outer ring 13b and the motor housing 11 is not exceeded (maximum permissible preload).

[0066] For example, the predetermined pressure between the shoulder device 14 and the outer ring 13b can act radially.

[0067] In the area of ​​the rolling bearing 13, the housing 4 abuts the motor housing 11 or the bearing shield 11a. The drive shaft 12 penetrates the housing 4 at least partially.

[0068] The outer ring 13b of the rolling bearing 13 is arranged between the housing 4 and the motor housing 11 such that the outer ring 13b is positively fitted in an axial direction X of the drive shaft 12. In particular, the outer ring 13b of the rolling bearing 13 can be pressed between the housing 4 and the motor housing 11 in the axial direction X. The housing 4 can thus be axially supported via the rolling bearing 13, in particular via the outer ring 13b, instead of directly via the motor housing 11.

[0069] Furthermore, the housing 4 comprises a stepped assembly 5 directed inwards, in which the rolling bearing 13 is arranged. The stepped assembly 5 can form a type of support shoulder for the outer ring 13b. In particular, the stepped assembly 5 can form a stepped section of the R. 418401

[0070] - 9 -

[0071] housing 4. For example, the stepped assembly 5 can be formed partially or completely around the drive shaft 12. Furthermore, the stepped assembly 5 can have an axial stop 6 for the outer ring 13b, wherein the axial stop 6 of the housing 4 is arranged offset inwards, i.e. upwards, with respect to the housing 4.

[0072] The rolling bearing 13 can be designed, for example, as a ball bearing, a four-point contact bearing, a tapered roller bearing, a spherical roller bearing, a ball bearing, or another type of radial bearing. Advantageously, the rolling bearing 13 can withstand loads in both the radial and axial directions X. For example, the type of rolling bearing 13 can be selected based on the maximum axial force it can withstand.

[0073] The drive unit 10 can be an electric motor. The drive shaft 12 can, for example, be designed as a worm shaft.

[0074] Fig. 3 shows an enlarged view of the rolling bearing 13 from Fig. 2 in a mounted state.

[0075] Figure 3 shows, in particular, the stepped assembly 5 of the housing 4 with its axial stop 6, and the shoulder assembly 14 of the motor housing 11, especially of the bearing shield 11a, with its axial stop 15. The stepped assembly 5 and the shoulder assembly 14 positively lock the outer ring 13b of the rolling bearing 13 in the axial direction X. In particular, they can axially press the outer ring 13b.

[0076] Although the present invention has been explained above by way of example embodiments, it is not limited to these, but can be modified in many ways. In particular, combinations of the preceding embodiments are also conceivable.

Claims

R. 418401 - 10 - Claims 1. Brake actuator (1) for a motor vehicle, comprising: a drive unit (10) with a motor housing (11) and a drive shaft (12) projecting from the motor housing (11); a rolling bearing (13) having an inner ring (13a) and an outer ring (13b), wherein the rolling bearing (13) is arranged on the motor housing (11) and is designed to support the drive shaft (12); and a housing (4) which adjoins the motor housing (11) in the area of ​​the rolling bearing (13), wherein the drive shaft (12) at least partially penetrates the housing (4), wherein the outer ring (13b) of the rolling bearing (13) is arranged between the housing (4) and the motor housing (11) such that the outer ring (13b) is positively fitted in an axial direction (X) of the drive shaft (12).

2. Brake actuator (1) according to claim 1, wherein the outer ring (13b) of the rolling bearing (13) is pressed between the housing (4) and the motor housing (11) in the axial direction (X).

3. Brake actuator (1) according to claim 1 or 2, wherein the motor housing (11) has a shoulder device (14) directed into the interior of the motor housing (11) in which the rolling bearing (13) is arranged.

4. Brake actuator (1) according to claim 3, wherein the shoulder device (14) is radially in contact with the outer ring (13b) and has an axial stop (15) for the outer ring (13b), the axial stop (15) being arranged offset inwards with respect to the motor housing (11). R. 418401 - 11 - 5. Brake actuator (1) according to one of the preceding claims, wherein a predetermined pressure in a radial direction is further present between the rolling bearing (13) and the motor housing (11).

6. Brake actuator (1) according to one of the preceding claims, wherein the rolling bearing (13) is designed as a ball bearing, as a four-point bearing, as a tapered roller bearing, as a spherical roller bearing or as a ball roller bearing.

7. Motor vehicle with a brake actuator (1) according to one of the preceding claims.

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