Automotive technology

Bosch hydraulic hybrid Practical and fun to drive An alternative powertrain that offers an efficient way to recover braking energy

  • Can reduce urban fuel consumption by up to 45 percent
  • Low-cost, robust, and easy-to-service hybrid drive
  • The worldís first hydraulic hybrid with a pneumatic pressure accumulator
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  • March 05, 2013
  • Automotive technology
  • Press releases
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press release

Boschís new, hydraulic full-hybrid powertrain shows that frugality can be fun. The technology, which Bosch is developing in collaboration with PSA Peugeot CitroŽn, is clear in its aims: to supply a hydraulic hybrid powertrain that will significantly reduce fuel consumption and CO2 emissions in compact cars. The system is also compatible with passenger cars from other vehicle segments, as well as light delivery trucks operating in urban environments.

The hydraulic hybrid is designed to enable a boost effect that would normally be offered only by complex electric drives. Here, a conventional internal-combustion engine combines with hydraulic units and an accompanying nitrogen pressure accumulator to provide a brief boost to acceleration. The hybrid system is able to support gasoline and diesel engines in ranges where they do not work at optimum efficiency.

The power-split concept permits various drive options. For short journeys, stored energy can be used to run exclusively on hydraulically generated power, with the internal-combustion engine remaining inactive and the vehicle producing zero emissions. For longer journeys, or when driving at higher speeds, accelerative force is provided by the internal-combustion engine. Alternatively, the two types of powertrain can also be combined. In this case, the energy stored in the hydraulic system and the fuel burned in the internal-combustion engine work together to drive the vehicle, which also provides a brief boost effect.

Bosch and PSA Peugeot CitroŽn see great potential in this technology. In the new European driving cycle, it has the capacity to reduce fuel consumption by up to 30 percent when compared to a conventional internal-combustion engine. For purely urban driving, this rises to as much as 45 percent. As a result, the range of a compact car can be greatly increased using this alternative powertrain. The improved efficiency is due to the careful configuration of the two powertrain components.

Whatís more, the hybrid system makes use of energy that would normally go to waste. Braking, for instance, quickly fills up the hydraulic accumulator: the kinetic energy captured during braking is converted into hydraulic energy and stored in the pressure accumulator. Normally, this energy would go to waste, turning into heat in the friction linings of the brakes. The advantages of a hybrid powertrain are equally evident when the vehicle is travelling at a constant speed. Here, the engine can be run within an efficient range while also filling the hydraulic energy accumulator.

This hydraulic-mechanical system makes for a low-cost, robust, and easy-to-service hybrid powertrain. Since it needs no specialized infrastructure, it can be used around the world.

Detailed technical description of operation
In addition to a conventional internal-combustion engine, a hydraulic hybrid powertrain also includes a pressure accumulator and a reservoir. Hydraulic units compress a gas cushion using hydraulic fluid. Fluid and gas are kept separate from one another. The gas cushion stores energy by the gas being compressed rather like a coiled spring. At this point, the pressure in the system is over 300 bar. The amount of energy that can be stored in the pressure accumulator depends on the size of the system. As soon as the pressure within the accumulator is relieved, the system works in reverse. The gas expands once more, providing a compressive force on the hydraulic fluid and driving a hydraulic motor. This motor takes the stored energy and delivers it back to the vehicle via the transmission.

It is true that the pressure accumulator has a more limited capacity and range than the lithium-ion batteries found in electric cars. Nonetheless, it is much quicker to recharge and can use the extra energy provided by the internal-combustion engine more efficiently.

About the collaboration between Bosch and PSA
The close collaboration between Bosch and PSA Peugeot CitroŽn dates back to an engineering alliance set up in 2008. In 2011, this strategic partnership saw Peugeot launch the 3008 HYbrid4, the worldís first series-produced diesel hybrid passenger car with axle-split drive. PSA Peugeot CitroŽn developed the electrical components (electric motor, power electronics, and high-voltage generator) in close collaboration with Bosch, a collaboration which extended to developing the special technical setup needed to use the ESPģ electronic stability program in hybrid vehicles. The hybrid powertrain concept now also features in PSAís Peugeot 508 (both the RXH station wagon and the HYbrid4 sedan) and CitroŽn DS5 HYbrid4 models, for which Bosch supplies the electrical powertrain components.

Contact persons for press inquiries:
Udo RŁgheimer, phone: +49 711 811-6283
Florian Flaig, phone +49 711 811-6282

Click here to find further information.

Automotive Technology is the largest Bosch Group business sector. In 2013, its sales came to 30.6 billion euros, or 66 percent of total group sales. This makes the Bosch Group one of the leading automotive suppliers (NB: Due to a change in accounting policies, the 2013 figures can only be compared to a limited extent with the 2012 figures). Automotive Technology largely operates in the following areas: injection technology for internal-combustion engines, alternative powertrain concepts, efficient and networked powertrain peripherals, systems for active and passive driving safety, assistance and comfort functions, technology for user-friendly infotainment as well as car-to-car and Car2X communication, and concepts, technology, and service for the automotive aftermarket. Bosch has been responsible for 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. In 2013, its roughly 281,000 associates generated sales of 46.1 billion euros. (NB: Due to a change in accounting policies, the 2013 figures can only be compared to a limited extent with the 2012 figures). Its operations are divided into four business sectors: Automotive Technology, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its roughly 360 subsidiaries and regional companies in some 50 countries. If its sales and service partners are included, then Bosch is represented in roughly 150 countries. This worldwide development, manufacturing, and sales network is the foundation for further growth. In 2013, the Bosch Group invested some 4.5 billion euros in research and development and applied for some 5,000 patents. This is an average of 20 patents per day. The Bosch Groupís products and services are designed to fascinate, and to improve the quality of life by providing solutions which are both innovative and beneficial. In this way, the company offers technology worldwide that is ďInvented for life.Ē

Further information is available online at www.bosch.com and www.bosch-press.com, http://twitter.com/BoschPresse.

PI8066 - March 05, 2013

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