The 2008 HYbrid Air combines petrol with compressed air in a full-hybrid solution and this technology is a key step in achieving the goal one day soon of 140mpg. The HYbrid Air combines two energies to achieve the highest efficiency in various situations. So, the compressed air will assist, or even take the place of, the petrol engine during the phases which consume the most energy such as acceleration and moving off.
The HYbrid Air consists of an energy tank containing pressurised air installed under the body in the central tunnel, a low pressure tank at the rear suspension cross member acting as an expansion bottle and an hydraulic unit consisting of a motor and a pump installed under the bonnet on the transmission.
The latter consists of an EGC (Electronic Gearbox Control) drivetrain to manage the distribution between the two motors. It replaces the mechanical gearbox and in addition offers automated gear changes.
The engine used in this application is the latest generation 3-cylinder petrol engine making the HYbrid Air compatible with existing platforms benefitting occupant space, modularity and the volume of the petrol tank, which remains unchanged.
The driver controls the two energy sources to achieve the highest overall efficiency possible in any given situation and switching between the three modes available is seamless for the driver.
In the Air (ZEV) mode, only the energy contained in the compressed air tank will drive the vehicle. As it depressurises, the air occupies an increasing amount of space in the energy tank and so displaces a corresponding volume of oil. This is an energy carrier which supplies the hydraulic motor coupled to the drivetrain. As the engine is switched off, the vehicle moves without consuming any fuel or emitting any CO2. This mode especially comes into its own when driving in urban areas.
In Petrol mode, only the 1.2-litre VTi 3-cylinder petrol engine powers the vehicle. This engine benefits from the latest technology to offer, compared to the previous generation, a reduction in weight of 21kg, friction reduced by 30% and advanced thermo-management to reach the optimum operating temperature more quickly. This mode is particularly suited to steady speeds on main roads and motorways.
In the Combined mode, the petrol engine and hydraulic motor operate simultaneously to move the vehicle in proportions adjusted according to the situation to achieve optimum fuel economy. Adaptable, the HYbrid Air can supply the hydraulic motor from two sources. While the quantity of energy contained in the pressurised air tank is sufficient to fulfil the driver's request, the hydraulic motor operates using this source. Then, if necessary, it can be supplied by the hydraulic pump directly. This mode is intended in particular for the transitional phases in urban areas and on the open road (moving off, acceleration).
The energy tank is filled in two ways. On deceleration (on braking or releasing the accelerator), the speed is reduced by the resistance to the compression of the air in this accumulator. The alternative consists of filling by restarting the internal combustion engine; in this situation, some of the energy produced by the petrol engine is used to compress the air.
On the current generation of B segment vehicles, the HYbrid Air considerably reduces fuel consumption and CO2 emissions. Following a homologation cycle test, a figure of 97.4mpg was achieved and CO2 levels of just 69g/km.
HYbrid Air technology is the result of a project which brought together 200 specialists including Bosch. The HYbrid Air was also developed in financial partnership with the ‘Investing in the Future Programme’ of the Ademe, the French Environment and Energy Management Agency.
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