Lexus Introduces RX 400h, the World's First Luxury Hybrid SUV

In conventional AWD vehicles, the weight and friction of the additional drive components reduce the vehicle's acceleration performance compared to the same model with 2WD. Not so with the RX 400h. The innovative electric AWD system employs a separate 50-kW electric motor (MGR) at the rear that provides up to 650 lb.-ft. of additional drive torque on demand. The system electronically varies front and rear torque distribution depending on traction conditions.

The Lexus hybrid technology also allows extended electric-mode operation during low speed or stop-and-go driving conditions. The permanent-magnet front electric drive motor (MG2) produces peak torque from zero-to-1,500 RPM, giving the RX 400h powerful and instantaneous response that will be especially felt and appreciated in low- and mid-speed performance and in merging and passing maneuvers.

A regenerative braking system further boosts system efficiency. When the RX 400h is coasting or the brakes are applied, the electric motors function as generators, capturing kinetic energy that would normally be lost as heat through the brakes and transforming it into useable electricity to recharge the batteries.

Vehicle Dynamic Integrated Management (VDIM)

With the RX 400h, Lexus also introduces a new generation of vehicle stability control systems known as Vehicle Dynamics Integrated Management (VDIM). This new system goes well beyond conventional traction and stability controls that simply react to challenging conditions. Instead, VDIM anticipates vehicle instability in virtually any direction and makes stabilizing corrections while allowing higher dynamic capability.

A vital component of VDIM is a new Electronically Controlled Braking system (ECB). The ECB system translates brake pedal stroke speed and pressure and generates the precise amount of combined electric regeneration and hydraulic pressure needed for virtually any driving condition.

Under guidance from VDIM, such precise brake control at individual wheels allows more optimized operation of the vehicle's dynamic handling systems that employ the brakes: ABS, Brake Assist, Vehicle Stability Control (VSC) and traction control (TRAC). VDIM also interfaces with the Electronic Throttle Control system, allowing it to modify vehicle power when needed, and a new Electronic Power Steering system (EPS) to optimize steering assist for each situation.

The EPS uses a DC motor and gear reduction system built into the steering gear housing to provide steering assist. This compact unit contributes to fuel economy by eliminating the traditional power steering pump and by providing its computer-controlled assist only when called for by the driver. EPS also allows a more precise and timely control of steering assist than conventional engine-driven hydraulic systems.

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