New Vehicle TOy OTA PrI us ToyoTa Prius Eco-Mobility’s PostEr car

In the mid-90s, talks and concerns about environmental pollution from automobiles were still in its infancy. But one carmaker was clearly preparing for the future. In 1997, the Prius – the world’s first mass-produced hybrid vehicle – went on sale in Japan. And for about 15 years since then, Toyota Motor Corporation (TMC) has been leading the drive towards sustainable mobility. Introduced globally in 2001, the Prius today is sold in over 70 countries, with sales of over 3.3 million full-hybrid vehicles. The company claims this accounts for over 80 % of all global hybrid sales, resulting in reduction of some 21 mn tonnes of CO 2. The third-generation Prius alone has sold more than 1 mn units worldwide.

54 www.autotechreview.com Toyota’s eco-friendly vehicle got the name, Prius, because it was launched before environmental awareness became a mainstream social issue. Meaning ‘before’ in Latin, the first glimpse of the hybrid concept was revealed at the 1995 Tokyo Motor Show, with the market launch of the first Prius (model NHW10) following two years later in December 1997. Six year thereafter, in 2003, Toyota launched the second generation Prius, codenamed XW20, with significant amount of changes in the overall vehicle mechanics and interior space. Led by chief engineer Shigeyuki Hori, develop- ment of the second generation Prius The Toyota Prius is a full hybrid – propelled resulted in 530 patents for the vehicle. by both a battery-powered electric The overall length of the vehicle was motor and a petrol-driven IC engine. extended by 150 mm from its previous avatar. The aerodynamically-designed Kamm tail body ensured better length and wind resistance, resulting in a drag coeffi- efficiency. This results in a high level of driven with the electric motor, while elec- cient (Cd) of 0.26. on-road performance, while minimising tric pumps warm the engine with previ- XW20 was discontinued in 2009 to fuel consumption and pollution from ously saved hot engine coolant before the make way for the third generation Prius, exhaust gases. The battery gets charged, internal combustion engine is started. The the XW30. By this time, Toyota was facing when the car is driven using the petrol EV (electric vehicle) mode is engaged tough competition from other products in engine. Alternatively, when brakes are under most low-load driving conditions, the market, primarily, the Honda Insight. applied, energy that most cars waste as and allows driving at low noise and no Market pressures led the largest carmaker heat lost during braking is converted to fuel consumption. Once the battery is in Asia to cut prices of the Prius in its electricity for the car to use later. exhausted, the car automatically reverts to home market. Toyota claimed its new aer- The HSD system ensures that each the normal mode. The Prius EMS (engine odynamic body design resulted in an power unit supplies significant amounts management system) also recognises improved Cd of 0.25. In mid-2011, Toyota of power, using the least amount of fuel. when the car is stationary and switches made changes to the exterior looks of the On ignition, the vehicle is ready to be off to conserve power, automatically Prius, including updated headlamps, switching back on again, when needed. revised tail lamps, plus a distinctive front fascia and bumper. engine We drive the new Toyota Prius to bring The 2012 Toyota Prius is powered by a to you a detailed technology review of the 1.8 l 2ZR-FXE high-expansion-ratio engine best selling hybrid in the world, explain- that makes use of the Atkinson cycle. The ing in detail the changes made to its pow- engine uses a double overhead camshaft ertrain, safety and comfort features as (DOHC) 16-valve cylinder head with a well as a comprehensive look at Toyota’s 4-cylinder die-cast block. Toyota’s VVT-i Hybrid Synergy Drive. (variable valve timing – intelligent) tech- nology optimises both intake and exhaust valve timing. Hybrid Synergy d rive® This engine is part of the ZR engine family, introduced by Toyota in 2007. The Hybrid Synergy Drive (HSD) used in It has the same bore and stroke as the the Prius is a full hybrid system, which is earlier 2ZR-FE, but the compression ratio often referred to as a combined hybrid is increased to 13.0:1 from the 2ZR-FE’s because the vehicle is propelled by both a 10.0:1. The inlet valve closing is also battery-powered electric motor and a pet- retarded in the new engine, which results rol-driven internal combustion engine. in a greater effective expansion of the Based on the need, the HSD helps the engine than compression. The output for car to switch between petrol and electric The 1.8 l 2Zr-FXE high-expansion-ratio engine the 2ZR-FXE is rated at 98 hp at 5,200 power or combine the two for maximum makes use of the Atkinson cycle. rpm, while the peak torque has been autotechreview March 2012 Volume 1 | Issue 3 55 New Vehicle TOy OTA PrI us

measured at 142 Nm @ 4,000 rpm. Together with the electric motor, the hybrid system net output increases to 134 hp. The previous generations of the Prius hybrid used the 1.5 l 1NZ-FXE engine. Since the initial start is handled by the battery-powered electric motors, the movement is noiseless. Even when the petrol engine comes alive, the Prius doesn’t fail you in terms of noise. Thanks to the electronically-controlled CVT, there is no drastic climb in revs, yet there is enough power for quick overtakes on the highways. Handling and ride quality is easy as well. Compared to the previous generation engine used in the Prius, the 2ZR-FXE Toyota Prius Battery Pack showing airflow. delivers improved levels of fuel efficiency. The use of the electric water pump is a case in point. The water pump is now Hybrid battery Pack Power Split device driven by electricity from the battery. The Ni-MH (nickel metal hydride) battery The power splitting device is used to dis- Engineers at Toyota have eliminated the used in the Prius is compact and light- tribute power produced by the petrol drive belt, which decreases mechanical weight, enabling a high input/output to engine to the drivetrain and the generator. loss and the flow of the coolant can be weight ratio. While the maximum systems A planetary gear consisting of a ring gear, controlled even more precisely according voltage is 650 V, the nominal voltage of pinion gears, a sun gear and a planetary to the vehicle's conditions. In fact, this is the battery pack is calculated at 201.6 V carrier is used to divide the power effi- the first production engine that requires that includes 168 cells of 1.2 V each. ciently. Essentially, it is a clever gearbox no accessory belts, an efficient way of Toyota’s hybrid system maintains the bat- that binds the gasoline engine, generator improving fuel economy. tery charge at a constant level at all times and electric motor together. In addition, the exhaust heat recircula- by monitoring and computing the cumu- tion system utilises exhaust heat, which lative amount of discharge under acceler- generator used to go waste, for the heater and to ation, and recharging by regenerative Compared to its earlier variants, the cur- warm up the engine, allowing quicker braking or with surplus power under nor- rent Prius has a more compact and light- heating and engine warm-ups. Two addi- mal running conditions. The capacity of weight generator, achieved through cen- tional mechanisms that make the engine the battery pack in the current Prius is tralised winding of the coils. It’s a syn- more efficient include the roller rocker measured at 6.5 Ah, with a battery peak chronous AC generator capable of high arm and the cool-EGR (exhaust gas recir- horsepower rating of 36 hp. speed axial rotation, realising substantial culation) system.

Motor Toyota's hybrid technology uses a smaller, yet more efficient permanent magnet syn- chronous motor with a maximum DC voltage of 650 V. Peak power output of the electric motor is measured at 80 hp, while the torque is a healthy 207 Nm. One might wonder why the 98 hp engine com- bined with an 80 hp motor results in a total output of 134 hp and not more. The reason is that 80 hp is the maximum the motor can develop, but since it draws power from a 36 hp rated battery pack, the final output would be the same and hence a total output of 134 hp. Addition- ally, there’s a second motor significantly smaller in size, which is used to start the IC engine and maintain revs during operation. The second and third-generation Power split Device in the Toyota Prius.

56 www.autotechreview.com electrical power, while the car is running in the mid-speed range.

Power Control Unit The power control unit in the Prius con- sists of an inverter, a voltage-boosting converter and an AC/DC converter to run the car on electric motors. The inverter converts DC supplied by the battery to AC to turn the electric motors and to use in the generator. Conversely, it converts AC generated by the electric motors and the generator into DC to recharge the battery. The car features direct cooling of switch- ing device, enabling improved cooling efficiency, inverter downsizing and weight reduction. The new Toyota Prius uses a third-generation inverter, shown here with the second-generation model. The second important feature in the power control unit is the voltage-boosting converter that increases the normal 201.6 Solar v entilation & reM ote aC air conditioning system by remote control V DC supply voltage to a maximum of before entering the car, lowering the tem- 650 V to feed the electric motors and the One of the most interesting additions to perature inside the cabin. generator, as required. On the other hand, the new Prius is clearly the solar ventila- The solar ventilation system is a prod- the DC/DC converter steps down the tion system, which features a solar panel uct developed by Kyocera Corporation of 201.6 V supply voltage from the battery to integrated on the moon roof. The electric- Japan. The company produces multi-crys- 12 V, to be used by ancillary systems and ity generated by the solar module drives talline silicon solar cells for the Prius. The electronic devices like the ECU. the fans to ventilate air inside the car, solar panel is made up of 36 polycrystal- even when the vehicle is parked during line silicon cells that are arranged in regenerative braking daytime. We found the feature to moder- a 6 × 6 grid. Like all other solar panels, The hybrid technology used in the Toyota ate temperature inside the vehicle during these cells generate electricity from the Prius can reuse kinetic energy by using its our drives in and around New Delhi. sun, capable of churning out about 53 W electric motors to regenerate electricity. The remote air conditioning system of power, more than enough to power a While hybrid vehicles still use conven- works closely with the solar ventilation fan that can ventilate the cabin when the tional brake pads at highway speeds, dur- system, enabling the driver to operate the vehicle is parked. The AC system with ing stop-and-go traffic conditions at slower speeds, electric motors help the vehicle brake. Upon application of brakes, the electric motors reverse direction, and the torque created by this reversal coun- teracts the forward momentum and even- tually stops the car. The energy that is recouped during braking is saved in a storage battery and used later to power the motor, whenever the vehicle is using its electric power source. reduction gear The newly developed reduction gear in the Prius is designed to reduce the high rpm of the front electric motors so that the power produced can be transferred to the wheels, with the added benefit of torque amplification. During our tests, we experienced this well in highway con- ditions, where the torque amplification effect, combined with higher revving capability of the front electric motors, provided seamless acceleration at will. The solar panel is made up of 36 polycrystalline silicon cells that are arranged in a 6 × 6 grid. autotechreview March 2012 Volume 1 | Issue 3 57 New Vehicle TOy OTA PrI us

solar ventilation, together with LED stop and tail lamps, helps save a lot of power. In an interaction with Auto Tech Review, a spokesperson at Toyota Kir- loskar Motor (TKM) explained that the solar roof delivers peak power when the following two conditions are met simulta- neously – the solar panel cell temperature is 25° and the amount of insolation (solar radiation) is 1,000 W/sq m. The power would vary with sunlight intensity. In addition, he mentioned there are four pre-requisites to start the solar ventilation system – (i) the car has to be switched-off completely, (ii) ventilation switch has to be on, (iii) 10 minutes should elapse after turning-off the power, and (iv) the amount of insola- tion should approximately be above 500 W/sq m.

deSign

Like we have mentioned in our introduc- Dashboard controls are conveniently located. tion, the Toyota Prius has an aerodynami- cally-designed Kamm tail body. Although conservative, the vehicle has gone them keep an eye on how much fuel cabin was the electronic shift lever, which through significant design changes since they're using over a particular driving returns to the home position automati- its 1997 debut. The new Prius is signifi- cycle. Information display in the centrally- cally after shifting, and enables smooth cantly more aerodynamic, which allow air placed MFD, located atop the vehicle shift operation. The parking range switch to flow more quickly over the top of the dashboard, is conveniently visible to the lets the driver change to the parking range car and create less drag. driver. with one touch. Inside the car, the biggest attraction is We particularly loved the touch tracer There is generous amount of space the energy monitor. A multi-function dis- feature that displays the switches inte- inside the Prius cabin, a product of Toyo- play (MFD) monitors energy flowing to grated into the steering wheel in the ta’s “minimum exterior, maximum inte- and from the engine and battery, along metre. And so was the case with the rior” design philosophy that also helps with information about the vehicle's head-up display, which projects various create ample luggage space. The front regenerative braking and battery levels. driving information on the lower wind- seatbacks are slim in design, allowing For efficiency-conscious drivers, this lets shield. The third big positive for us in the good legroom even for tall passengers. The retractable saddle-type headrests on the rear seats enable good rear visibility for the driver. Prius is easily the most recognisable hybrid in the world today, and it’s under- standable why Toyota has retained the general design of the vehicle over genera- tions. However, the new variant is about 10 cm longer and about 2.5 cm wider as compared to its previous variant. The lower cooling requirement meant Toyota designers could afford to place a tall bumper with a large grille. The hood merges into the swooping silhouette of the roofline with ease, and the tail lamp cluster accentuates the look of the hatch- back at the rear. Information display in the MFD is conveniently visible to the driver.

58 www.autotechreview.com Safety

The safety package in the Prius includes both active and passive safety measures. The airbags package includes driver air- bag, front passenger airbag, driver knee airbag, side airbags, and curtain shield airbags. All airbags come with the supple- mental restraint system or SRS. Active headrests in the front seats contribute to reduction of neck impact in the event of rear-end collisions. The other critical safety feature is the crash safety body, which has front and rear crumple zones that help absorb impact energy in a collision.

environMent ProteC tion

More than three decades back, Toyota stated its commitment to environmental protection, and the HSD is a result of that objective. The HSD system has essentially remained same, but it has gone through several refinements over this period. The effort has been to continuously develop and improve technology that reduces the The airbag system in the new Toyota Prius. amount of carbon generated in production or emitted in exhaust gases, without sacri- ficing performance. The target, in fact, is to achieve zero emissions. engine 2Zr-FXE (Atkinson cycle) Toyota’s search for zero emissions and tyPe 4-cylinder aluminium block and head, double overhead cam (DOHC); environment protection did not stop at 16-valve VVT-i developing technology alone. It uses eco- friendly materials, such as ecological plas- valvetrain 4-valve/ cylinder with VVT-i tic, which helps in the reduction of CO2 diSPlaCeMent 1,798 cc emissions, compared to petroleum-based bore × Stroke 3.17 × 3.48 inches plastics. Ecological plastics have been used in the cowl side trim, scuff plates, exPanSion ratio 13.0 :1 finish plates and the seat cushion pad in CoMbined Power 134 hp the driver’s seat. Moreover, there is pro- active use of recyclable materials, includ- torqUe 105 lb-ft @ 4,000 rpm ing Toyota Super Olefin Polymer (TSOP) Motor tyPe Permanent Magnet synchronous Motor and Recycled Sound Proofing Products Max. voltage DC 650 V (RSPP). In fact, the Prius is claimed to be the biggest user of rare earths of any Motor oUtPUt 80 hp object in the world. battery tyPe Nickel-Metal Hydride

noMinal voltage DC 201.6 V (168 × 1.2 V cells )

CaPaCity 6.5 ampere hour text: Deepangshu Dev sarmah battery HorSePower rating 36 hp PHoto: Deepangshu Dev sarmah tranSMiSSion tyPe Electronically Controlled Continuously Variable Transmission (ECVT)

aCCeleration 0–60 MPH 9.8 seconds

toP SPeed 179 kmph (112 mph) read this article www.autotechreview.com Toyota Prius – specification sheet autotechreview March 2012 Volume 1 | Issue 3 59