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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 operates in a power generation mode, converting the vehicle’s kinetic energy into electrical energy that is stored in the battery. This energy is then used to assist in braking the vehicle by feeding back mechanical resistance through the drive shaft. This method of braking is known as regenerative braking or feedback braking. The implementation of this technology significantly improves the driving range of electric vehicles on a single charge.
The brake energy recovery system typically combines an electric and a hydraulic braking system. The hydraulic component plays a crucial role in controlling brake pressure, ensuring a smooth pedal feel for the driver and maintaining overall vehicle safety. Unlike traditional fuel-powered vehicles, electric vehicles lack an internal combustion engine to provide vacuum assistance for the braking system. Additionally, the integration of regenerative braking requires communication between the hydraulic system and the motor controller.
Major automotive manufacturers and suppliers have developed various hydraulic brake solutions tailored for different types of electric vehicles. Let's explore some of the most common approaches:
1. **Vacuum-Assisted Hydraulic Brake System**
This system incorporates an electronic vacuum pump (EVP) and a pedal travel sensor (PTS) into the traditional vacuum-assisted setup. The EVP provides the necessary vacuum for the booster since electric vehicles don’t have an engine to supply it. A vacuum tank helps stabilize the system and reduce the frequency of EVP activation. PTS ensures efficient energy recovery by detecting the driver’s braking input. While this solution is cost-effective and technologically mature, it suffers from low energy recovery efficiency and poor braking comfort due to direct coupling between friction and motor braking forces.
2. **ESP/ESC-Based Hydraulic Brake System**
Bosch’s ESPhev system eliminates the need for a vacuum booster and instead integrates regenerative braking functions into the existing ESP technology. It uses the driver’s braking demand from the pedal sensor to distribute braking force between the motor and hydraulic systems. This system offers high energy recovery and better coordination, but it is generally limited to smaller vehicles due to its design constraints.
3. **EHB (Electro-Hydraulic Brake) Based System**
EHB systems are more advanced, featuring a power unit, hydraulic components, and an electronic control unit. They allow for full decoupling of the brake pedal, enabling precise control over both regenerative and hydraulic braking. Bosch’s HAShev and Mando’s AHBIII are examples of such systems. These systems offer superior performance, including improved energy recovery and enhanced safety features, but they are complex, heavier, and more expensive to maintain.
4. **New Brake Booster-Based Systems**
These systems replace traditional vacuum boosters with high-performance motors that directly generate master cylinder pressure. They are lighter, respond faster, and improve braking efficiency. The brake pedal can be fully decoupled, allowing for customizable pedal feel and enhanced driving experience. These systems have been successfully implemented in models like the Nissan Leaf and Tesla Model S.
As electric vehicle technology continues to evolve, the brake systems are gradually shifting towards lightweight, modular, and intelligent solutions such as EHB and new brake boosters. Although foreign suppliers like Bosch, Continental, and TRW have a strong presence in this market, domestic manufacturers are making significant progress through research and collaboration with academic institutions. With continued advancements, it is expected that local suppliers will soon be able to develop competitive products that meet global standards.