Innovation Meets Tradition

Electric Parking Brake with Lightweight Drum

Innovation Meets Tradition: Electric Parking Brake with Lightweight Drum

The underestimated heroes of the road make a comeback

Continental is known worldwide for its proven and innovative drum brakes. Simplex drum brakes in particular have long proven to be extremely reliable and low-maintenance. In view of the changes in the automotive industry aimed at electrification, emission reduction, comfort and safety, Continental offers innovative solutions to utilize proven drum brake technology in modern, highly efficient and environmentally friendly vehicle concepts and to further expand its strengths.

A prime example of the innovative use of drum brake technology is the integration of a modern electric parking brake into the hydraulic service brake. The current generation of the EPB-Si (Electric Parking Brake for Simplex Brakes) uses a small DC motor to set the brake shoes in motion. This advanced technology is used, for example, on the rear axle of the VW ID. platform in models such as the ID.3 and ID.

The Return of the Classics: Why Drum Brakes are a Sustainable Alternative

Drum brakes offer the following major advantages for electrified and clean passenger cars:

  • Efficiency in electric vehicles: The low frequency of use of wheel brakes in electric vehicles compared with conventional vehicles makes drum brakes attractive. Braking operations are mainly carried out by using the e-machine as a generator, resulting in a braking effect of up to 0.3 g.

  • Energy-saving driving style: In energy-saving driving, the wheel brakes of an electric vehicle are rarely activated. This means that the drum brake reliably provides consistent performance even if it is inactive for a longer period of time due to its closed design, which prevents corrosion on the surface of the cast iron friction ring.

  • Future-proof: The sophisticated design of the drum brake makes it future-proof. It is particularly resistant to corrosion and offers reliable performance, making it an attractive option for electric vehicle brake systems.

  • Increased efficiency due to design: Another advantage of drum brakes in electric vehicles is their natural efficiency due to their design. Since the brake shoes are always actively retracted by a spring after the braking process, there is almost no residual torque, which helps to maximize range. By contrast, a disc brake often has a residual torque of around 1 to 2 Nm, which means that the use of a drum brake can save around 1 to 2 g of CO2 per kilometer.

  • More sustainability through fewer brake dust emissions: Another advantage of the drum brake is that the brake dust remains in the drum brake. This is particularly advantageous for conventional and hybrid vehicles, where the wheel brakes are applied more frequently and brake dust emissions are a critical issue. Therefore, the EPB-Si meets the Euro 7 requirements.

Due to the advantages mentioned above, drum brakes are currently experiencing a revival. They offer efficient braking and help maximize the range of electric vehicles, making them a promising option for the automotive industry.

On the Way to New Strengths: the EPB-Si as an Advanced Electronic Parking Brake

Current development activities in the field of hydraulic brake systems will add two further aspects to the EPB-Si:

  • The electric parking brake will be actuated by a highly efficient motor gearbox, which will further reduce the power requirement. The braking force is permanently applied by a self-locking mechanism in the gearbox without any energy requirement.

  • In addition, the new lightweight drum design will reduce the mass of the brake by up to 35%. This weight brings the EPB-Si with lightweight drum closer to that of a brake disc with caliper.

The electric parking brake is a perfect addition for electrified vehicles, as the required power is already available. At Continental, we are already working on another future advantage of our drum brake technology: the use of lightweight materials, which significantly reduces the weight of the drum brake. This enables even more efficient use of the brakes and helps to reduce the weight of the vehicle.

The lightweight drum consists of two parts: the friction ring is made of conventional gray cast iron and offers optimum tribology, while the front plate of the housing is made of aluminum. The targeted use of the heavy gray cast iron makes a larger brake diameter possible. The design weight of drum brakes normally limits the feasible brake diameter, but Continental’s lightweight drum can solve this problem by reducing the brake mass by up to 35%. In addition, the lightweight drum has an attractive appearance, although the actual brake is not visible due to the closed rim design.

For electrified vehicles, the advantages of lightweight construction and low drag torque are obvious. Less weight and high efficiency mean more range or a smaller battery without compromising range.    

The EPB-Si is an innovative drum brake that has proven to be a long-term component (with a mileage of 300,000 kilometers or more) and requires no maintenance on the rear axle of electric vehicles. By comparison, conventional or hybrid vehicles require replacement of the brake shoes at most once.  

In summary, innovative drum brakes such as the EPB-Si are a smart technology with great potential for use in efficient vehicles.

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