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Hydraulic brake Bosch solution for braking energy recovery in automotive electronics
Brake energy recovery in electric vehicles refers to the process where, during deceleration or braking, the drive motor switches into a power generation mode. This converts part of the vehicle’s kinetic energy into electrical energy, which is then stored in the battery. At the same time, the motor applies regenerative braking by feeding back torque to the drive shaft, helping to slow down the vehicle. This technique is commonly known as regenerative braking or feedback braking. Implementing this technology can significantly improve the vehicle's driving range on a single charge.
The brake energy recovery system typically combines an electric and hydraulic braking system. The hydraulic component plays a crucial role in controlling brake pressure, ensuring a good pedal feel for the driver and maintaining overall vehicle safety. Unlike traditional fuel-powered vehicles, electric vehicles lack a conventional internal combustion engine to provide vacuum for the brake system. Additionally, the implementation of regenerative braking requires seamless communication between the hydraulic system and the motor.
Major automotive manufacturers and suppliers have developed various hydraulic brake solutions tailored for different types of electric vehicles. Below are some typical approaches used in the industry:
1. **Vacuum-Assisted Hydraulic Brake System**
This system integrates an Electronic Vacuum Pump (EVP) and a Pedal Travel Sensor (PTS) into the existing vacuum-assisted hydraulic brake setup. The EVP provides the necessary vacuum for the brake booster, while the PTS detects the driver's braking input to optimize energy recovery. Although this solution uses many existing components, it has limitations such as lower energy recovery efficiency and less smooth braking performance due to direct integration of motor feedback with friction brakes.
2. **ESP/ESC-Based Hydraulic Brake System**
For example, Bosch's ESPhev system eliminates the need for a vacuum booster. It builds upon standard ESP technology, adding features like hydraulic assist and feedback torque coordination. The system calculates braking demand based on pedal travel and distributes braking force efficiently. While this approach offers better energy recovery and compact design, it is generally suitable for smaller vehicles due to its limited load capacity.
3. **EHB (Electro-Hydraulic Brake) Based System**
EHB systems consist of a power unit, hydraulic unit, and electronic control unit. They use motors and accumulators to generate brake pressure and allow precise control over both motor feedback and hydraulic braking. Examples include Bosch's HAShev and Mando's AHBIII. These systems offer improved comfort and higher energy recovery but come with increased complexity and cost.
4. **New Brake Booster-Based Hydraulic System**
This innovative approach replaces traditional vacuum boosters and hydraulic pumps with a high-performance motor that drives a piston through a gear mechanism. It enables faster response times, shorter braking distances, and better compatibility with advanced driver assistance systems. Systems like Nissan Leaf and Tesla Model S have successfully implemented this technology. Companies such as Continental and Bosch have also introduced similar solutions, focusing on modular and intelligent designs.
While foreign suppliers have made significant progress in developing EHB and new brake booster technologies, domestic manufacturers still face challenges in key areas like ESP/ESC and solenoid valves. However, there has been growing progress in research and development, with many local suppliers collaborating with universities to advance these technologies. As electric vehicles become more widespread, it is expected that domestic suppliers will catch up and compete effectively in the global market.