Mobility Solutions

For low fuel consumption and a good range Bosch regenerative braking systems for hybrid and electric vehicles

  • Regenerative braking systems based on current ESP® Generation 9
  • Vacuum-independent systems for plug-in hybrids and electric cars
  • Complete portfolio for electromobility
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  • September 13, 2011
  • Mobility Solutions
  • Press releases
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press release

The range of hybrid and electric vehicles is set to grow strongly in the years ahead. To achieve the targeted fuel savings and range, these vehicles must, among other things, recover as much energy as possible from braking so that this can be used for electrical propulsion. Bosch is currently developing regenerative braking systems that, in tandem with the powertrain, enable optimum recuperation. “Ideally, all braking operations will be used in their entirety for energy generation,” says Dr. Werner Struth, president of the Bosch Chassis Systems Control division. “In situations where the electric motor's brake torque is not sufficient, the hydraulic braking system provides support. This goes unnoticed by the driver.” Bosch offers two types of regenerative braking system – solutions that interact with classic vacuum-based brake boosters and vacuum-independent systems.

With today's vehicles, the brake booster uses a vacuum to boost the power applied by the driver. The vacuum is generated by either the internal-combustion engine or a vacuum pump. However, hybrid vehicles switch off the internal-combustion engine as often as possible and electric vehicles do not have one at all. These vehicles therefore use either an electric vacuum pump or a vacuum-independent braking system.

Vacuum-based solution: ESP® hev
The ESP® hev regenerative braking system is based on the current Generation 9 and is therefore a very cost-effective solution. In hybrid and electric vehicles with a vacuum-based brake booster, ESP® hev coordinates the electric-motor and hydraulic brake torques and controls the vacuum pump. The product is being taken into series operation in a hybrid vehicle with rear-wheel drive and front-/rear-axle brake-circuit split. With ESP® hev for this drive and brake configuration, the rear brake circuit is decoupled from the driver's foot. An increased dead stroke of the brake pedal is used to decelerate the vehicle initially using only regenerative power via the electric motor connected to the rear axle. For this purpose, the system requests generator torque equivalent to the pedal travel. It is limited to 0.2 g, which is around 20 percent of the maximum braking performance. This covers almost all the braking maneuvers that occur in everyday situations. If the driver applies more pressure to the brake, additional hydraulic brake torque is generated at the front axle using the conventional method, so the vehicle is slowed down using both axles. If the regenerative brake torque available at the rear axle is not sufficient, the system uses the hydraulic modulator's pump to generate additional braking pressure for the rear axle. These processes go unnoticed by the driver, which means there is no change to the familiar pedal response or vehicle behavior. In addition to the version for the front-/rear-axle brake-circuit split described above, Bosch also offers a version for diagonal braking circuits.

Vacuum-independent solution: HAS hev
In future, Bosch will offer the HAS hev braking system for hybrid and electric vehicles not equipped with a vacuum-based brake booster. HAS stands for Hydraulic Actuation System and hev indicates that the product is designed for installation in hybrid electric vehicles. The system is suitable for all brake-circuit splits and drive concepts. It comprises a brake operation unit and a hydraulic actuation control module which supplement the ESP® hydraulic modulator. The brake pedal and wheelbrakes are mechanically decoupled. The brake actuation unit processes the braking command, and an integrated pedal travel simulator ensures the familiar pedal feel. The braking pressure modulation system implements the braking command using the electric motor and wheelbrakes. The aim is to achieve maximum recuperation while maintaining complete stability. Depending on the vehicle and system status, deceleration of up to 0.3 g can be generated using only the electric motor. If this is not sufficient, the modulation system uses the pump and high-pressure accumulator to generate additional hydraulic braking pressure for the wheelbrakes.

In addition to the braking system, Bosch offers a complete portfolio for hybrid and electric vehicles. This includes electric motors for various hybrid and electric drive concepts, the corresponding power electronics, lithium-ion battery systems, and complete function development.

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Mobility Solutions is the largest Bosch Group business sector. In 2015, its sales came to 41.7 billion euros, or 59 percent of total group sales. This makes the Bosch Group one of the leading automotive suppliers. The Mobility Solutions business sector combines the group’s expertise in three mobility domains – automation, electrification, and connectivity – and offers its customers integrated mobility solutions. Its main areas of activity are injection technology and powertrain peripherals for internal-combustion engines, diverse solutions for powertrain electrification, vehicle safety systems, driver-assistance and automated functions, technology for user-friendly infotainment as well as vehicle-to-vehicle and vehicle-to-infrastructure communication, repair-shop concepts, and technology and services for the automotive aftermarket. Bosch is synonymous with important automotive innovations, such as electronic engine management, the ESP anti-skid system, and common-rail diesel technology.

The Bosch Group is a leading global supplier of technology and services. It employs roughly 375,000 associates worldwide (as of December 31, 2015). The company generated sales of 70.6 billion euros in 2015. Its operations are divided into four business sectors: Mobility Solutions, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its roughly 440 subsidiaries and regional companies in some 60 countries. Including sales and service partners, Bosch’s global manufacturing and sales network covers some 150 countries. The basis for the company’s future growth is its innovative strength. Bosch employs 55,800 associates in research and development at 118 locations across the globe. The Bosch Group’s strategic objective is to deliver innovations for a connected life. Bosch improves quality of life worldwide with products and services that are innovative and spark enthusiasm. In short, Bosch creates technology that is “Invented for life.”

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PI7485 - September 13, 2011

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