Hybrid Technology

Toyota Highlander Hybrid is a "full" hybrid, which means it is capable of operating in electric-only or gas engine-only mode, as well as a mode that combines the power of the gas engine and electric motor. A 288-volt DC Nickel metal hydride (Ni-MH) battery pack fits neatly under the second row seat. The battery's power is directed through a "boost converter" that raises voltage to 650V DC. An inverter changes this to 650V AC, providing its elevated power to a front-mounted 123-kW electric motor that turns as high as 12,500 RPM.

There are two motor-generators in the 4x2 models and three in the 4WD-i models. Referred to as MG1, MG2 and MGR (rear electric motor in 4WD-i), each has a specific function and each does double duty as both drive motor and generator (although MG1 is a starter and provides no motive force).

The engine-driven generator (MG1) and rear electric motor (MGR) can charge the battery pack, which powers other electric motors as needed. Power from the gas engine and front electric-drive motor (MG2) is distributed to the drive wheels via a planetary gear-type continuously variable transmission, which eliminates individual gear ratios. The 4WD-i system employs a separate 50-kW electric motor (MGR) at the rear that provides up to 96 lb.-ft. of additional drive torque as required, depending on driving conditions.

The permanent-magnet front electric drive motor (MG2) produces peak torque from 0-1,500 RPM, giving the Highlander Hybrid powerful and instantaneous response that will be especially felt and appreciated in low- and mid-speed performance and in merging and passing maneuvers. In addition to its motor-generator duties, the crucial MG1 adds two functions: one as a starter motor for the gas engine; and two, by regulating the amount of electrical power it generates (which varies its RPM), MG1 controls the output speed of the transaxle through the planetary gear set - without clutches or viscous couplings. This key element of the Toyota hybrid powertrain is also the reason why Highlander Hybrid eliminates the gear changes that can typically be felt even from the most refined modern automatic transmissions.

The power steering pump, water pump, and air conditioner compressor are electrically powered rather than engine-belt-driven to reduce noise and optimize fuel consumption. These are necessary, because the gas engine often shuts down - a fuel-saving benefit of the hybrid system - especially when the vehicle is stopped or driven slowly through traffic.

A regenerative braking system further boosts system efficiency. When the vehicle 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 Dynamics Integrated Control (VDIM)

In Toyota Highlander Hybrid, VDIM constantly calculates vehicle motion based on signals from a yaw rate and deceleration sensor, wheel speed sensors and steering angle sensor. Using these inputs, VDIM controls all of the vehicle's dynamic handling systems and can employ them collectively and seamlessly, allowing it to quickly detect the onset of a loss of vehicle control and help correct it. The ability to operate in such a proactive manner means that corrections to vehicle attitude are typically quicker, more accurate and subtler than with other stability and traction control systems.

A vital component of VDIM is the Electronically Controlled Braking system (ECB), which translates brake pedal stroke and pressure to generate the precise amount of combined electric regeneration and hydraulic pressure needed to match driving conditions.

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