Method for operating a braking system

Abstract

The invention relates to a method for operating a braking system (200) in a motor vehicle, wherein: the braking system (200) is assigned to a wheel of the motor vehicle and comprises at least two brake elements (217); at least one actuator (210, 212) is assigned to the at least two brake elements (217); the at least one actuator (210) is designed to actuate the at least two brake elements (217), as a result of which a braking function is carried out; and, in the method, the at least two brake elements (217) are actuated independently of one another.

Description

[0001] R. 412551

[0002] - 1 -

[0003] Description

[0004] title

[0005] Method for operating a braking system

[0006] The invention relates to a method for operating a braking system, in particular a braking system in a motor vehicle, and an arrangement for carrying out the method.

[0007] State of the art

[0008] Brakes are used in motor vehicles to reduce or limit speed. In most designs used to date, this is achieved by converting supplied kinetic energy into heat energy via friction. It should be noted that different braking systems are used for this purpose. Examples of braking systems include drum brakes and disc brakes.

[0009] Electric vehicles are powered, among other things, by so-called wheel hub motors. A wheel hub motor is a motor that is installed directly into a vehicle's wheel and simultaneously forms the wheel hub. Part of the motor transmits the generated torque to the wheel with which it rotates.

[0010] Most designs are electric wheel hub motors, but combustion engines also exist. Both internal and external rotor designs are possible for electric wheel hub motors. See Figure 1 for further details.

[0011] Disc brakes typically use brake calipers whose brake pads are pressed against the disc on both sides. The brake caliper surrounds the brake disc, which also requires installation space above the disc with its larger radius, see Figure 2. R. 412551

[0012] - 2 -

[0013] Multi-disc brakes are used to increase braking torque by increasing the number of friction pairs. They are currently used, for example, in aircraft.

[0014] Drum brakes, on the other hand, are actuated by a hydraulic cylinder or, in the case of electromechanical designs, by an expanding actuator movement, see Figure 3. There are different embodiments of this, with the so-called simplex variant, featuring an expanding cylinder, being the simplest.

[0015] Disclosure of the invention

[0016] Against this background, a method with the features of claim 1 and an arrangement according to claim 11 are presented. Embodiments are described in the dependent claims and in the description.

[0017] A method for operating a braking system in a motor vehicle is presented, wherein the braking system is assigned to a wheel of the motor vehicle and comprises at least two braking elements, and at least one actuator is assigned to the at least two braking elements. Thus, one actuator can be assigned to at least two braking elements. If several actuators are provided, each can be assigned to one braking element or to several braking elements.

[0018] The at least one actuator is designed to actuate the at least two brake elements, thereby performing a braking function. When one, some, or all of the brake elements are actuated, the braking effect occurs. In the case of a friction lining as a brake element, actuation causes the friction lining to be brought into contact with, or pressed against, a rim or brake disc, so that the braking effect is achieved due to friction. R. 412551

[0019] - 3 -

[0020] The at least one actuator is thus controlled to actuate the at least two brake elements. The method is characterized by the fact that the at least two brake elements are actuated independently of each other. This means that the at least one actuator can actuate the brake elements independently of each other.

[0021] In one embodiment, the brake elements are actuated alternately, i.e., one after the other.

[0022] Furthermore, the brake elements can first be actuated alternately and then together.

[0023] At least one actuator can include a spreading mechanism, which is implemented, for example, in a double piston.

[0024] The activation of the brake elements can, for example, be carried out depending on the driving situation of the vehicle.

[0025] Alternatively or additionally, the activation of the brake elements can be carried out depending on their wear. This takes into account whether brake elements, especially friction linings, are already subject to wear due to frequent use. These brake elements can then be "protected".

[0026] Furthermore, an arrangement for operating a braking system in a motor vehicle is presented, which includes a control unit with which the braking elements of a braking system are actuated independently of one another. The control unit thus outputs corresponding control signals for at least one actuator, which in turn actuates the at least two braking elements in response to these control signals. These control signals can also be determined and generated within the arrangement. An evaluation unit can also be provided for this purpose.

[0027] It was thus recognized that different braking strategies can be used depending on or independent of the different braking systems. R. 412551

[0028] - 4 -

[0029] Building on this, it was recognized that new braking and control strategies can be particularly advantageous for multi-disc brake systems. Specifically, the presented method is based on the understanding that actuating all brake elements or friction linings equally is not beneficial in every situation. This can also be detrimental with regard to service life and design.

[0030] In one possible embodiment, a spreading mechanism, typically comprising an expanding piston, is used to actuate the brake. Using such a mechanism instead of a conventionally enclosed piston reduces the required installation space, particularly in areas with larger diameters. Support can still be provided by the wheel carrier. Furthermore, actuation of a friction lining applied to the inside of the rim is possible.

[0031] For further explanation, operating strategies for multi-disc brakes are shown in conjunction with the figures, which enable an optimal system design.

[0032] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0033] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0034] Brief description of the drawings

[0035] Figure 1 shows an exploded view of a wheel with a wheel hub motor.

[0036] Figure 2 shows a perspective view of an embodiment of the disc brake. R. 412551

[0037] - 5 -

[0038] Figure 3 shows several illustrations of different drum brake concepts with varying braking effects.

[0039] Figure 4 shows a schematic representation of an actuation concept with a hybrid brake caliper at the top and bottom.

[0040] Figure 5 shows a schematic representation of an actuation concept with double pistons in the brake caliper and friction surface on the inside of the rim.

[0041] Figure 6 shows an actuation concept with a hybrid brake caliper on one side, as with a disc brake, in combination with a double piston in the brake caliper.

[0042] Embodiments of the invention

[0043] The invention is schematically illustrated with reference to embodiments in the drawings and is described in detail below with reference to the drawings.

[0044] Figure 1 shows an exploded view of a wheel with a wheel hub motor. The illustration shows a wheel 10 with tire, a rotor 12, a bearing 14, a stator 16, a capacitor ring 18, a power electronics unit 20, a protective cover 22, a brake caliper 24, and a brake disc 26.

[0045] Figure 2 shows a perspective view of a disc brake, designated as a whole by the reference numeral 50. The illustration shows a brake disc 52 with a brake caliper 54.

[0046] Figure 3 shows different types of drum brakes. A first embodiment 100 shows a simplex drum brake, a second embodiment 102 a duplex drum brake, a third embodiment 104 a duo-duplex drum brake, a fourth embodiment 106 a servo drum brake, and a fifth embodiment 108 a duo-servo drum brake. R. 412551

[0047] - 6 -

[0048] Operating strategies for multi-disc brakes are now proposed, which differ from previous strategies for conventional wheel brakes or become applicable only due to the different actuation mechanism. Applying the same clamping force to all friction linings as potential braking elements is considered suboptimal. The proposed operating strategies offer various advantages regarding dimensioning, costs, and also regarding particulate matter emissions from friction brakes.

[0049] The multi-disc brake in a so-called corner module is intended, in principle, only to be used when deceleration via the drive system is insufficient or the operating point is unsuitable for it, such as typically when braking to a standstill. A corner module is a ready-to-install module in which various functions are integrated. For example, components of an electric drive system and brake components can be integrated into the corner module. Stability and driving dynamics functions can also be integrated into a corner module. The corner module presented here can be used in conjunction with a wheel hub motor.

[0050] If several actuators are provided, partial braking with a slight deceleration is possible by activating only one actuator. Figure 4 shows a braking system for implementing one embodiment of the presented method. This braking system is designated by the reference numeral 200. The illustration shows a rim 202, two brake discs 204, a wheel hub 206, an upper actuator 210, and a lower actuator 212. The two actuators 210 and 212 each have pistons 214 and 216, respectively, which are pressed against the brake discs 204 for braking. The contact surfaces on the pistons 214 and 216 serve as brake elements 217 and are designed, for example, as friction linings.

[0051] In the concept shown in Figure 4, either only the upper or only the lower actuator is actuated, and thus only the associated brake elements 217 are actuated. R. 412551

[0052] - 7 -

[0053] In the variant with pistons at the top and bottom, alternating actuation is possible for partial braking, with simultaneous actuation of both pistons only conceivable under heavy deceleration. Since the combined clamping force of both pistons is applied, these pistons can be significantly smaller to ensure that, in the event of disc locking, both brake calipers are actuated.

[0054] It is assumed that the actuation mechanism or its design allows the brake pistons to be operated differently.

[0055] Furthermore, it is conceivable that braking with only one brake disc could be used for as long as possible if the required braking torque, due to the necessary deceleration, does not exceed the braking torque that can be applied by a single brake. This would reduce particulate matter emissions instead of actuating all pads with minimal force. In addition, it is also conceivable that the operating strategy for actuating the multi-disc brakes could be modified depending on the location. In urban environments, this strategy would primarily focus on particulate matter reduction, as described above, whereas on highways, alternating braking to reduce wear is also a possibility.

[0056] The brake disc, which is embossed on the rim, is only activated during high deceleration or emergency braking situations and is only reserved for emergency braking situations. This allows for a significantly smaller or thinner design of this brake disc, normally with an intact drivetrain and braking with the brake disc mounted internally, see Figure 5.

[0057] Figure 5 shows a brake system 300 with a double piston in the brake caliper and a friction surface on the inside of the rim. The illustration shows a rim 302, two brake discs 304, a wheel hub 306, a hydraulic or electromechanical control or control unit 308, an actuator 310 with a spreading mechanism, and a double piston 312. The contact surfaces on the double piston 312 are designed as friction linings 317 and serve as brake elements. R. 412551

[0058] - 8 -

[0059] In this embodiment, a multi-disc brake is actuated by a spreading mechanism. This allows for a very space-saving implementation of the multi-disc brake. Simultaneously, this also makes it possible to design the housing or the rim surface as the brake disc, thereby achieving greater component integration. Both hydraulic and electromechanical designs are conceivable.

[0060] Furthermore, it can be designed that the brake discs are actuated alternately. This ensures even wear and prevents rust / corrosion. This strategy can also influence the thickness of the brake disc and brake pads during the design process. The friction linings 317 are thus actuated independently of each other.

[0061] It is also conceivable to design and control the double piston (Figure 5) accordingly, so that it moves asymmetrically and thus uses only the main brake disc for normal braking with moderate deceleration, and only uses the second brake disc mounted on the rim at higher decelerations, e.g., > 0.7 g. In the load spectrum for friction brakes, the number of braking maneuvers with maximum deceleration is very small, only -0.01% of all braking maneuvers fall into this range, which can also be taken into account in the design.

[0062] To prevent corrosion on the brake discs, occasional brake disc wiping, i.e. applying the brake pads to keep the surfaces of the friction pair intact and fully functional, e.g. when braking to a standstill, is conceivable.

[0063] Another strategy could be to actuate the brake disc located more favorably for heat dissipation, e.g., via airflow, if the corner module heats up unfavorably. A corresponding procedure should be included in the actuation concept for this purpose.

[0064] Similarly, if temperatures are too low for optimal operation of the Corner Module, selecting the brake disc to be braked is conceivable. R. 412551

[0065] - 9 -

[0066] Figure 6 shows another embodiment of the brake system, which is designated in its entirety by the reference numeral 400. The illustration shows a rim 402, two brake discs 404, a wheel hub 406, a hydraulic or electromechanical control or control unit 408, and a brake caliper.

[0067] 410 as with a disc brake and a double piston 412.

[0068] In all multi-disc brake systems shown, it is possible that the brake discs have different thicknesses depending on the actuation strategy and the design of the brake actuators.

[0069] When implementing the multi-disc brake system in a corner module, it can be primarily located on the front axle due to the higher braking torque requirement.

Claims

R. 412551 - 10 - Claims 1. Method for operating a braking system (200, 300, 400) in a motor vehicle, wherein the braking system (200, 300, 400) is assigned to a wheel (10) of the motor vehicle and comprises at least two brake elements (217), and at least one actuator (210, 212, 310) is assigned to the at least two brake elements (217), which is configured to actuate the at least two brake elements (217), thereby performing a braking function, in which the at least two brake elements (217) are actuated independently of each other.

2. Method according to claim 1, wherein friction linings (317) are used as brake elements (217).

3. Method according to claim 1 or 2, wherein the brake elements (217) are actuated alternately.

4. Method according to claim 3, wherein the at least two brake elements (217) are first actuated alternately and then jointly.

5. Method according to one of claims 1 to 4, wherein at least one actuator (210, 212, 310) of the at least one actuator (210, 212, 310) comprises a spreading mechanism. R. 412551 - 11 - 6. Method according to one of claims 1 to 5, wherein at least one actuator (210, 212, 310) is configured as a double piston (312, 412) of the at least one actuator (210, 212, 310).

7. Method according to any one of claims 1 to 6, wherein a multi-disc brake system is operated.

8. Method according to any one of claims 1 to 7, wherein a braking system (200, 300, 400) is operated which is integrated in a Corner Module.

9. Method according to one of claims 1 to 8, wherein the actuation of the at least two brake elements (217) is carried out depending on the driving situation of the motor vehicle.

10. Method according to any one of claims 1 to 9, wherein the actuation of the at least two brake elements (217) is carried out depending on their wear.

11. Arrangement for operating a braking system (200, 300, 400) in a motor vehicle with a control unit (308, 408) which is configured to carry out a method according to one of claims 1 to 10.

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