In normal driving, power from the engine will be divided by the power split device both to drive the wheels directly and to power the generator, which, in turn, drives the electric motors. In these circumstances, power allocation is constantly monitored and adjusted between the engine and motors to maximise efficiency. When sudden acceleration is required, engine and electric motors operate in tandem, with extra power supplied by the battery to boost motor response.
Intelligent four-wheel drive
The RX400h’s Hybrid Synergy Drive system uniquely features a second electric motor to drive the rear wheels and provide electric four-wheel drive for certain driving conditions.
Controlled by the Vehicle Dynamics Management system, the four-wheel drive is automatically engaged via continuously adjusted front and rear electric motor torque, as when accelerating hard from standstill or through the gears, when cornering, or whenever a loss of traction from the front wheels is detected.
Moreover, during deceleration and under braking, the engine switches off and the electric motors act as high-output generators, driven by all four wheels. This regenerative braking system optimises energy management by recovering kinetic energy that would usually be lost as heat and storing it as electrical energy in the battery. In addition, battery power level is constantly managed by the engine-driven generator, which means there is no need to recharge the system from an external source.
Vehicle Dynamics Management
In conjunction with the new Hybrid Synergy Drive system, the RX400h has enhanced handling and driving stability thanks to its re-tuned suspension, specially designed Electronic Power Steering (EPS) and the installation of Vehicle Dynamics Management, one of the most advanced vehicle stability control systems currently available.
The VDM is less obtrusive that conventional VSC systems, but is ultimately more effective. By means of high-speed "by-wire" throttle, brake and transmission technology, VDM co-ordinates control of the Hybrid Synergy Drive, the electric four-wheel drive and Electronically Controlled Braking (ECB), adjusting front and rear electric motor torque according to driving conditions and stabilising vehicle behaviour on low grip surfaces, such as snow or mud.
Flagship Of The RX Series
The RX400h shares the sleek and muscular styling of the RX300, but will be the flagship of the range riding on bespoke 18-inch alloy wheels and featuring a redesigned front grille, fog lamps and bumper. The cabin displays all the trademark Lexus values of peerless comfort, outstanding quality and driving ergonomics. Exclusive brushed aluminium trim reflects the state-of-the-art technology used in the powertrain. On the instrument panel in front of the driver, the tachometer is replaced by a power meter. The driver can also monitor the operation of the different elements in the Hybrid Synergy Drive system by means of a continuous read out on the seven-inch touch display screen on the centre console.Published 21 May 2004