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Abstract

Hybrid Synergy Drive (HSD) is a set of hybrid car technologies developed by Toyota and used in the company's Prius , Highlander Hybrid , Camry Hybrid , Lexus RX 400h/RX 450h , Lexus GS 450h , Lexus LS 600h/LS 600hL , and Lexus HS 250h automobiles . It is also used in the Nissan Altima Hybrid.

Description of Hybrid Synergy Drive


HSD technology produces a full hybrid vehicle and allows the car to perform on the electric motor only as opposed to most other brand hybrids which cannot and are considered mild hybrids ; it also combines an electric drive and a planetary gear set which performs similarly to a continuously variable transmission . The Synergy Drive is a drive-by-wire system with no direct mechanical connection between the engine and the engine controls: both the gas pedal/accelerator and the gearshift lever in an HSD car merely send electrical signals to a control computer .

HSD is a refinement of the original Toyota Hybrid System ( THS ) used in the 1997-2003 Toyota Prius. The second generation system THS II first appeared on the redesigned Prius. The name was changed in anticipation of its use in vehicles outside the Toyota brand ( Lexus ; the HSD-derived systems used in Lexus vehicles were termed Lexus Hybrid Drive since 2006).

The Lexus Hybrid Drive system has since been touted for its increase in vehicle power as well as environmental and efficiency benefits. By May 2007 Toyota sold one million hybrids and by the end of August 2009 had sold a total of two million. Toyota hybrids make up approximately 75% of United States hybrid sales.

The Toyota HSD replaces a normal geared transmission with an electromechanical system. Because an internal combustion engine (ICE) delivers power best only over a small range of torques and speeds , the crankshaft of the engine is usually attached to an automatic or manual transmission by a clutch or torque converter that allows the driver to adjust the speed and torque that can be delivered by the engine to the torque and speed needed to drive the wheels of the car.

When required to classify the transmission type of an HSD vehicle (such as in standard specification lists or for regulatory purposes), Toyota describes HSD-equipped vehicles as having E-CVT ( Electronically-controlled Continuously Variable Transmission ).

In the "standard" car design the alternator (AC generator) and starter (DC motor) are considered accessories that are attached to the internal combustion engine (ICE) which normally drives a transmission to power the wheels propelling the vehicle.