Wheel Brakes Contribute to Sustainability
Jul 31, 2023
FRANKFURT, Germany – Continental recently posted a three-part series of articles on its website providing its vision of future braking systems. Below is part two: Hydraulic Brake Systems for Future Mobility – Wheel Brakes Contribute to Sustainability.
Article one: The Future of Brakes – Brake Systems of the Future.
Whatever the architecture of the brake system of the future will look like –every car will continue to need wheel brakes. The need for deceleration, emergency stopping, stabilization, standstill management and fail-safe operation makes wheel brakes indispensable. However, on top of that, brakes have to contribute to lower CO2 and dust emissions. Electrification will also bring a revival of the drum brake. Brake calipers, on the other hand, will similarly be optimized for the specific boundary conditions of electrification and for specific types of vehicles. The braking hardware is as much on the move as software and architecture are.
Automated Driving (AD) and electrification pose new challenges to the brakes – as does the need for greater sustainability and lower friction losses caused by residual drag. Hydraulics may become optional in the long run – depending on the strategy of individual vehicle manufacturers. Instead, electromechanical brake actuation offers greater freedom to define vehicle architecture. Both fundamental types of wheel brake, disc/caliper and drum brake, offer potential for future requirements and this potential can be harvested with either hydraulic or electromechanical actuation. Continental is developing wheel brake solutions for new vehicle architectures and new environmental requirements for brakes.
Wheel brakes actuated by electric motors facilitate improvement. Installed on the rear axle, for instance, they offer an ideal solution for regenerative braking, independent of brake pedal feel and hydraulic pressure modulation. Continental is developing electromechanical actuators for calipers and drum brakes alike: The e-caliper and e-drum. The “intelligence“ to control the electric actuation motor can be integrated into the wheel brake, which is part of a future trend towards brake system “disintegration” and distribution.
Dust generated through braking (disc/drum and brake pad/shoe abrasion) is another challenge for the automotive industry. In the future, the aim is to reduce the particulate matter (PM) emission of this type of dust in order to lower the overall vehicle particle emissions. For calipers, one of the current approaches is to apply a hard coating to the brake disc, which reduces abrasion. However, this solution is cost-intensive as the coating is expensive. Still, calipers are an attractive choice, particularly on the front axle (FA) and for vehicles with a greater mass. As discs with calipers dissipate heat very well owed to their open design, they are perfectly suited for delivering very high braking power to decelerate a vehicle with a lot of kinetic energy. This is reflected in Continental’s expertise in developing calipers for hard-coated discs, which reduce particle emissions from this brake type. In order to also reduce the residual friction of the brake shoes, which remain in contact to the disc after the braking action, a caliper design with a greater air gap between disc and pad is available, as well as a solution for active brake pad retraction.
Downsizing is another innovation path that Continental is pursuing with calipers. The potential for further downsizing is a result of electrification: In an electric vehicle equipped with a brake-by-wire system such as the MK C1 or the future MK C2, up to 80 percent of all deceleration events can be covered with regenerative braking during a normal driving style. Assuming that braking actions are consistently started with regenerative braking, this percentage can go up as high as 95 percent. In other words, in an electric vehicle with an optimized regenerative braking strategy, the wheel brakes are hardly ever used for deceleration. This change can be utilized to downsize the calipers, which saves wheel-sprung mass and contributes to vehicle efficiency. As infrequent use of a caliper can potentially cause issues due to brake disc corrosion and less aggressive brake pad surfaces, Continental is also preparing solutions for keeping a caliper fully operational despite longer downtimes.
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