Because there are times when the engine is not running, hybrid vehicles need an alternative to vacuum boost systems. Most use an electro-hydraulic system with a high-pressure accumulator used to provide brake pressure boost. The Nissan system replaces this expensive accumulator system with an electric boost system. Based on Nissan's description (available after the jump), it appears that an electric motor concentric with the master cylinder drives a ball-screw to push the piston beyond the actual pedal input to provide the boost. This is an on-demand system that could use less energy than the pumps required to charge an accumulator. Because the accumulator pressure leaks down, the pump has to run periodically to recharge it. This electric system doesn't need to do that. We'll be looking into both of these in more detail soon.
Nissan Announces Two World-First Steering and Braking Technologies
YOKOHAMA (July 21, 2010) - Nissan Motor Co., Ltd. today announced two world first technologies - "Electro-hydraulic Power Steering system" and "Electric Driven Intelligent Brake" systems. They will be mounted on the Nissan Fuga Hybrid, which goes on sale in Japan this fall, and Infiniti M Hybrid, a luxury hybrid model scheduled to be launched in 2011 in the United States and Europe.
The new systems are characterized by creative yet simple mechanisms and advanced computerized control, providing not only effective environmental performance for hybrid vehicles, but also high parts integration, responsive steering and braking, along with a natural maneuvering feel.
Electro-hydraulic Power Steering system
For the first time in the world, an Electro-hydraulic Power Steering system has been adopted in which the motor is activated only when the driver is steering. The system is smaller than traditional power steering systems, which was achieved by integrating multiple parts. It offers the advantages of both types of steering - the natural and smooth steering of hydraulic power steering and the improved fuel efficiency of electric power steering - combined to create a balanced system fitting the Nissan Fuga and Infiniti M's luxury sport sedan buyers' needs.
Electric Driven Intelligent Brake
The Electric Driven Intelligent Brake, another world's first system, utilizes the vehicle's electric motor to directly operate the brake cylinders. When the driver steps on the brake pedal, the necessary braking force is maintained while the hydraulic pressure of the friction brake is controlled to help maximize the energy regeneration of the hybrid motor. Because of its simple structure, in which the motor directly operates the brake cylinders, this new Electric Driven Intelligent Brake system has the potential to be applied to various future hybrid vehicles.
Nissan's goal is to achieve superior environmental performance while pursuing a fundamental quality of its cars – the joy of driving. The hybrid drive system to be used on the Fuga and Infiniti M Hybrids consists of the gasoline engine, electric motor and a unique Intelligent Dual Clutch Control utilizing separate electronically-controlled clutches on the drive wheels. This allows high environmental efficiency, while achieving an exhilarating driving experience with high-response linear acceleration levels that equal or exceed those of gasoline-powered cars.
These technologies are the culmination of the company's research and development efforts based on the Nissan Green Program 2010 (NGP 2010) – Nissan's mid-term environmental action plan that includes initiatives to reduce CO2 emissions and introduce truly effective technologies, products and services into the market.