Hsd Seminar

8/8/2019 Hsd Seminar

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Contents

1. Principle

I . Power sources II . MG1 and MG2

III . Transmission

2. Operations I . Phases of operation

II. Performance

3. Subsequent developments I . Hybrid Synergy Drive (HSD)

II. Next generation

4. List of vehicles with HSD technolog y

5. Comparison with other hybrids

6 . Aftermarket

7 . Controvers y



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INTRODU C TION

Hybrid Synergy Drive (HSD) is a set of hybrid car technologies developed byToyota and used in the company's Auris, Prius, Highlander Hybrid, Camry Hybrid, Estima,Alphard, Lexus RX 400h/RX 450h, Lexus GS 450h, Lexus LS 600h/LS 600hL, and LexusHS 250h automobiles. Toyota also licenses its HSD technology to Nissan for use thatcompanies' Nissan Altima Hybrid. HSD technology produces a full hybrid vehicle andallows the car to perform on the electric motor only as opposed to most other brand hybridswhich cannot and are considered mild hybrids; it also combines an electric drive and a planetary gearset which performs similarly to a continuously variable transmission. TheSynergy Drive is a drive-by-wire system with no direct mechanical connection between theengine and the engine controls: both the gas pedal/accelerator and the gearshift lever in anHSD car merely send electrical signals to a control computer.

HSD is a refinement of the original Toyota Hybrid System (THS) used in the1997 to 2003 Toyota Prius. The second generation system THS II first appeared on theredesigned Prius in 2004. The name was changed in anticipation of its use in vehicles outsidethe Toyota brand (Lexus; the HSD-derived systems used in Lexus vehicles have been termedLexus Hybrid Drive since 2006). The Lexus Hybrid Drive system is tuned for increased power and performance along with efficiency concerns; [1] it was introduced on all-wheel

drive and rear-wheel drive Lexus models. By May 2007 Toyota had sold one million hybridsworldwide and by the end of August 2009 had sold a total of two million. Toyota -producedhybrids make up approximately 75% of United States hybrid sales.



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Principle

The Toyot HSD repl es a normal geared transmission with an

electromechanical system. Because an internal combustion engine (IC deli ers power best only over a small range of torques and speeds, the crankshaf t of the engine is usuallyattached to an automatic or manual transmission by a clutch or torque conver ter that allows

the dr iver to adjust the speed and torque that can be delivered by the engine to the torque and

speed needed to dr ive the wheels of the car. When required to classify the transmission type

of an HSD vehicle (such as in standard specif ication lists or for regulatory purposes), Toyotadescr i bes HSD-equi pped vehicles as having E-CVT (Electronically-controlled

Continuously Variable Transmission).

Power sources:-

In the "standard" car design the alternator

(AC generator) and star ter (DC motor) are considered

accessor ies that are attached to the internal combustion

engine (IC ) which normally dr ives a transmission to

power the wheels propelling the vehicle. A battery is

used only to star t the car'sinternal combustion engine and run accessor ies when

the engine is not running. The alternator is used torecharge the battery and run the accessor ies when the

engine is running. HSD replaces the gear box (transmission), alternator and star ter motor

with a pair of powerful motor-generators (designated M and M , ~60 Hp total) with a

computer ized shunt system to control them, a mechanical power splitter that acts as a second

differential, and a battery pack that serves as an energy reservoir. The motor-generator uses

power from the battery pack to propel the vehicle at star tup and at low speeds or under

acceleration. The IC may or may not be running at star tup. When higher speeds, faster

acceleration or more power for charging the batter ies is needed the IC is star ted by the

motor-generator (acting as a star ter). These features allow the IC to normally be turned off

for traff ic stops²accessory power (including air conditioning if needed) is normally provided by the battery pack.

High voltage unit of the HSD



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When a moving vehicle operator wants the vehicle to slow down the initial travelof the brake pedal engages the motor -generator(s) into generator mode converting much of the forward motion into electrical current flow which is used to recharge the batteries while

slowing down the vehicle. In this way the forward momentum regenerates (or converts)much of the energy used to accelerate the vehicle back into stored electrical energy. Harder braking action engages standard front disk and rear drum brakes which are also provided for faster stops and emergency use. This wastes energy which could have been recovered and isdiscouraged for normal use.

MG1 and MG2:-

y MG1 (motor generator 1) generates electrical power. MG1 recharges the EV batteryand supplies electrical power to drive MG2. In addition, by regulating the amount of electrical power generated (thus varying MG1's internal resistance and rpm), MG1effectively controls the transaxle's continuously variable transmission. MG1 alsoserves as the engine starter.

y MG2 (motor generator 2) drives the vehicle. MG2 and the engine work together todrive the wheels. The addition of MG2's strong torque characteristics help achieveexcellent dynamic performance, including smooth start-off and acceleration. Duringregenerative braking, MG2 converts kinetic energy into electrical energy, which isthen stored in the EV battery.



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T ransmission:-

HSD eng ine wit

el ect ¡ ic mot or and generat or

The mechanical gear ing design of the system allows the mechanical power from

the IC engine to be split three ways: extra torque at the wheels (under constant rotation

speed), extra rotation speed at the wheels (under constant torque), and power for an electr icgenerator. A computer program running appropr iate actuators controls the systems and

directs the power f low from the different engine + motor sources. This power split achieves

the benef its of a continuously var iable transmission (C T), except that the torque/speed

conversion uses an electr ic motor rather than a direct mechanical gear train connection. An

HSD car cannot operate without the computer, power electronics, battery pack and motor-

generators, though in pr inci ple it could operate while missing the internal combustion

engine. In practice, HSD equi pped cars can be dr iven a mile or two without gasoline, as an

emergency measure to reach a gas station.

An HSD transaxle contains a planetary gear set that adjusts and blends the

amount of torque from the engine and motor(s) as it¶s needed by the front wheels. It is a

sophisticated and complicated combination of gear ing, electr ical motor-generators and

computer controlled electronic controls. One of the motor-generators (M in Toyotamanuals; sometimes called "M -T" for "Torque") is mounted on the dr ive shaf t, and thus

couples torque into or out of the dr ive shaf ts: feeding electr icity into M adds torque at the

wheels. The engine end of the dr ive shaf t has a second differential; one leg of thisdifferential is attached to the internal combustion engine and the other leg is attached to a

second motor-generator (M in Toyota manuals; sometimes "M -S" for "Speed"). The

differential relates the rotation speed of the wheels to the rotation speeds of the engine andM , with M used to absorb the difference between wheel and engine speed. The

differential is an epicyclic gear set (also called a "power split device"); that and the two

motor-generators are all contained in a single transaxle housing that is bolted to the engine.

Special couplings and sensors monitor rotation speed of each shaf t and the total torque on the

dr ive shaf ts, for feedback to the control computer.



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O perat ions

The HSD dr ive works by shunting electr ical power between the two motor

generators, running off the battery pack, to even out the load on the internal combustionengine. Since a power boost from the electr ical motors is available for per iods of rapidacceleration, the IC can be downsized to match only the average load on the car, rather than

sized by peak power demands for rapid acceleration. The smaller internal combustion engine

can be designed to run more eff iciently. Fur thermore, dur ing normal operation the engine

can be operated at or near its ideal speed and torque level for power, economy, or emissions,

with the battery pack absorbing or supplying power as appropr iate to balance the demand

placed by the dr iver. Dur ing traff ic stops the internal combustion engine can even be turned

off for even more economy.

The combination of eff icient car design, regenerative brak ing, turning the engine

off for traff ic stops, signif icant electr ical energy storage and eff icient internal combustion

engine design give the HSD powered car signif icant eff iciency advantages²par ticular ly incity dr iving.

Phases of operat ion:-

Hybr id Synergy Dr ive



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The HSD operates in distinct phases depending on speed and demanded torque.Here are a few of them:

y Engine start: To start the engine, power is applied to MG1 to act as a starter. Becauseof the si e of the motor generators, starting the engine requires relatively little power from MG1 and the conventional starter motor sound is not heard. Engine start canoccur while stopped or moving.

y Low gear (equivalent): When accelerating at low speeds in normal operation, the

engine turns more rapidly than the wheels but does not develop sufficient t orque. Theextra engine speed is fed to MG1 acting as a generator. The output of MG1 is fed toMG2, acting as a motor and adding torque at the driveshaft.

y High gear (equivalent): When cruising at high speed, the engine turns more slowlythan the wheels but develops more torque than needed. MG2 then runs as a generator to remove the excess engine torque, producing power that is fed to MG1 acting as amotor to increase the wheel speed. In steady state, the engine provides all of the power to propel the car unless the engine is unable to supply it (as during heavy acceleration,or driving up a steep incline at high speed). In this case, the battery supplies thedifference. Whenever the required propulsion power changes, the battery quickly balances the power budget, allowing the engine to change power relatively slowly.

y R everse gear: There is no reverse gear as in a conventional gearbox: the computer feeds negative voltage to MG2, applying negative torque to the wheels. Early modelsdid not supply enough torque for some situations: there have been reports of earlyPrius owners not being able to back the car up steep hills in San Francisco. The problem has been fixed in recent models . If the battery is low, the system cansimultaneously run the engine and draw power from MG1, although this will reduceavailable reverse torque at the wheels.

y Silent operation: At slow speeds and moderate torques the HSD can drive withoutrunning the internal combustion engine at all: electricity is supplied only to MG2,allowing MG1 to rotate freely (and thus decoupling the engine from the wheels). Thisis popularly known as "Stealth Mode." Provided that there is enough battery power,

the car can be driven in this silent mode for some miles even without gasoline.



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y Neutral gear: Most jur isdictions require automotive transmissions to have a neutral gear that decouples the engine and transmission. The HSD "neutral gear" is achieved

by turning the electr ic motors off. Under this condition, the planetary gear is stationary

(if the vehicle wheels are not turning); if the vehicle wheels are turning, the r ing gear

will rotate, causing the sun gear to rotate as well (the engine iner tia will keep the

carr ier gear stationary unless the speed is large), while M freewheels so no power is

dissi pated.

Lexus Hybr id Dr i¢

e

y R egenerati e brak ing: By drawing power from M and depositing it into the

battery pack, the HSD can simulate the deceleration of normal compression brak ing

while saving the power for future boost. The regenerative brakes in an HSD system

absorb a signif icant amount of the normal brak ing load, so the conventional brakes on

HSD vehicles are undersized compared to brakes on a conventional car of similar

mass.

y Compression brak ing: The HSD system has a special transmission setting labelled

'B' (for Brake), that takes the place of a conventional automatic transmission's 'L'

setting, providing engine brak ing on hills. This can be manually selected in place of

regenerative brak ing. Dur ing brak ing when the battery is approaching potentiallydamaging high charge levels, the electronic control system automatically switches toconventional compression brak ing, drawing power from M and shunting it to M ,

speeding the engine with throttle closed to absorb energy and decelerate the vehicle.

y Electric boost: The battery pack provides a reservoir of energy that allows the

computer to match the demand on the engine to a predetermined optimal load curve,

rather than operating at the torque and speed demanded by the dr iver and road. The

computer manages the energy level stored in the battery, so as to have capacity toabsorb extra energy where needed or supply extra energy to boost engine power.



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y Battery charging: The HSD can charge its battery without moving the car, by runningthe engine and extracting electrical power from MG1. The power gets shunted into the battery, and no torque is supplied to the wheels.

Performance:-

The Toyota Prius has modest acceleration but has extremely high efficiency for amid si ed four-door sedan: Usually significantly better than 40 mpg (US) is typical of brief

city jaunts; 55 mpg is not uncommon, especially for extended drives at modest speeds (alonger drive allows the engine to warm up fully). This is approximately twice the fuelefficiency of a similarly equipped four -door sedan with a conventional power train. Not allof the extra efficiency of the Prius is due to the HSD system: the Atkinson cycle engine itself was also designed specifically to minimi e engine drag via an offset crankshaft to minimi e piston drag during the power stroke, and a unique intake system to prevent drag caused bymanifold vacuum versus the normal Otto cycle in most engines. Furthermore, the Atkinsoncycle recovers more energy per cycle than the Otto because of its longer power stroke. Thedownside of the Atkinson cycle is much reduced torque, particu larly at low speed; but theHSD has enormous low-speed torque available from MG2.

The Highlander Hybrid (also sold as the Kluger in some countries) offers better acceleration performance compared to its non-hybrid version. The hybrid version goes from 0 ±60 mph in7.2 seconds, trimming almost a second off the conventional version's time. Net hp is 268 hp(200 kW) compared to the conventional 215 hp (160 kW). Top speed for all Highlanders islimited to 112 mph (180 km/h). Typical fuel economy for the Highlander Hybrid rates between 27 and 31 mpg. A conventional Highlander is rated by the EPA with 19 city, 25highway mpg.\



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C ut away d i spl ay o f t £

e HSD

The HSD mileage boost depends on using the gasoline engine as eff iciently as

possi ble, which requires:

y extended dri es, especially in winter : Heating the internal cabin for the passengers

runs counter to the design of the HSD. The HSD is designed to generate as little wasteheat as possi ble. In a conventional car, this waste heat in winter is usually used to heat

the internal cabin. In the Pr ius, running the heater will then require the engine tocontinue running to generate cabin-usable heat. This effect is most pronounced by

turning the climate control (heater) off when at a stop when the engine is running.

Normally the HSD control system will shut the engine off as it is not needed, and will not star t it again until the generator reaches a maximum speed.

y moderate acceleration: Because hybr id cars can throttle back or completely shut off the engine dur ing moderate, but not rapid, acceleration, they are more sensitive than

conventional cars to dr iving style. Hard acceleration forces the engine into a high-

power state while moderate acceleration keeps the engine in a lower power, high

eff iciency state (augmented by battery boost).

y gradual brak ing: R egenerative brakes re-use the energy of brak ing, but cannot absorb

energy as fast as conventional brakes. Gradual brak ing recovers energy for re-use,

boosting mileage; hard brak ing wastes the energy as heat, just as for a conventional car. Use of the "B" (brak ing) selector on the transmission control is useful on long

downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy. Use of "B" constantly is discouraged by Toyota as it may

promote excessive wear on cer tain gears.



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Most HSD systems have batteries that are si ed for maximal boost during a singleacceleration from ero to the top speed of the vehicle; if there is more demand, the batterycan be completely exhausted, so that this extra torque boost is not available. Then the systemreverts to just the power available from the engine. This results in a large decline in performance under certain conditions: an early-model Prius can achieve over 90 mph (140km/h) on a 6 degree upward slope, but after about 2,000 feet (610 m) of altitude climb the

battery is exhausted and the car can only achieve 55 ±60 mph on the same slope

(until the battery is recharged by driving under less demanding circumstances).



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S ubsequent development s

F irst-¤

eneration (G1) Toyot a hybr id: Toyot a Hybr id Syst em (THS)

The basic design of the Toyota Hybr id System / Hybr id Synergy Dr ive has not changed since its introduction in the 1997 Japanese-market Toyota Pr ius, but there have been

a number of signif icant ref inements.

The schematic diagrams illustrate the paths of power f low between electr icmotor-generator 1 (MG1), gasoline internal combustion engine (IC ), planetary gearset "power split device" elements (S:central "sun", C: planetary carr ier, R:outer r ing) and motor-

generator 2 (MG2).

There has been a continuous, gradual improvement in the specif ic capacity of the

traction battery. The or iginal Pr ius used shr ink-wrapped 1.2 volt D cells, and all subsequent THS/HSD vehicles have used custom 7.2 V battery modules mounted in a carr ier.

Called Toyota Hybr id System for initial Pr ius generations, THS was followed by

THS II in the 2004 Pr ius, with subsequent versions termed Hybr id Synergy Dr ive. The THS

relied on the voltage of the battery pack : between 276 and 288 V. The Hybr id Synergy Dr ive

adds a DC to DC conver ter boosting the potential of the battery to 500 V or more. Thisallows smaller battery packs to be used, and more powerful motors.



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Hybrid Synerg y Drive ( HS D):-

Although not par t of the HSD as such, all HSD vehicles from the 2004 Pr ius

onwards have been f itted with an electr ic air-conditioning compressor, instead of the

conventional engine-dr iven type. This removes the need to continuously run the engine whencabin cooling is required. Two positive temperature coeff icient heaters are f itted in the heater

core to supplement the heat provided by the engine.

Second -Generation (G2) Toyot a hybr id: Hybr id Synergy Dr i ¥ e (HSD) f our -wheel dr i¥ e syst em

In 2005, vehicles such as the Lexus R 400h and Toyota Highlander Hybr idadded four-wheel dr ive operation by the addition of a third electr ic motor ("MGR ") on the

rear axle. In this system, the rear axle is purely electr ically powered, and there is no

mechanical link between the engine and the rear wheels. This also permits regenerative

brak ing on the rear wheels. In addition, the motor (MG2) is linked to the front wheel transaxle by means of a second planetary gearset, thereby mak ing it possi ble to increase the

power density of the motor. Ford has also developed a similar hybr id system, introduced inthe Ford Escape Hybr id.

In 2006 and 2007, a fur ther development of the HSD dr ivetrain, under the Lexus

Hybr id Dr ive name, was applied on the Lexus GS 450h / LS 600h sedans. This system uses

two clutches (or brakes) to switch the second motor's gear ratio to the wheels between a ratio

of 3.9 and 1.9, for low and high speed dr iving regimes respectively. This decreases the power f lowing from MG1 to MG2 (or vice versa) dur ing higher speeds. The electr ical path isonly about 70% eff icient, thus decreasing the power f low there increases the overall

performance of the transmission. The second planetary gearset is extended with a second

carr ier and sun gear to a ravigneaux-type gear with four shaf ts, two of which can be held still alternatively by a brake/clutch. The GS 450h and LS 600h systems utilized rear-wheel dr ive

and all-wheel dr ive dr ivetrains, respectively, and were designed to be more powerful than

non-hybr id versions of the same model lines, while providing comparable engine class

eff iciency.



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N ex t generat ion:-

Third -Generation (G¦

) Hybr id Synergy Dr i § e (HSD) / Lexus Hybr id Dr i§ e syst em

Toyota CEO Katsuak i Watanabe said in a February 16, 2007 interview that Toyota was "aiming at reducing, by half, both the size and cost of the third-generation HSD

system." The new system will feature lithium-ion batter ies in later years. Lithium-ion

batter ies have a higher energy capacity-to-weight ratio, but cost more, don't last as long as

NiMH, and operate at higher temperatures, and are subject to thermal instability if not

proper ly manufactured and controlled, raising safety concerns.



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Li st of vehi cl es wi th HS D

technol ogy

The following is a list of vehicles with Hybrid Synergy Drive and relatedtechnologies (Toyota Hybrid System I/II; Lexus Hybrid Drive)

y Toyota Prius

o with THS: December 1997±October 2003o with THSII: October 2003±present

y Lexus RX 400h / Toyota Harrier Hybrid (March 2005±)

y Toyota Highlander/K luger Hybrid

o with THSI: July 2005±September 2008o with THSII: October 2008±present

y Lexus GS 450h (March 2006±present)

y Toyota Camry Hybrid (May 2006±present)

y Lexus LS 600h/LS 600hL (April 2007±present)

y Toyota A-BAT (concept truck)

y Nissan Altima Hybrid (2007±present)

y Lexus RX 450h (2009±present)

y Lexus HS 250h (2009±present)

y Lexus CT 200h (late 2010±)

y Toyota Auris (July 2010±)



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Compar i son wi th other hybr i ds

General Motors, DaimlerChrysler's and BMW's Global Hybrid Cooperation is

similar in that it combines the power from a single engine and two motors. In 2009, thePresidential Task Force on the Auto Industry said that "GM is at least one generation behindToyota on advanced, 'green' powertrain development."

Ford Motor Company independently developed a system with key technologiessimilar to Toyota's HSD technology in 2004. As a result, Ford licensed 21 patents fromToyota in exchange for patents relating to emissions technology. It is currently offered in anSUV, the Ford Escape, and a sedan, the Ford Fusion Hybrid, that was released in March

2009. The four-cylinder hybrid Escape achieves an increase in mileage, and is rated by theEPA with a combined 34 mpg, a 36% improvement over other similar si ed SUVs fromSubaru and Honda (Forester and CR-V, 25 mpg combined).

In contrast, Honda's Integrated Motor Assist uses a more traditional ICE and transmissionwhere the flywheel is replaced with an electric motor, thereby reducing complexity andincreasing serviceability due to the familiar layout.



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A ftermarket

Some early non-production plug-in hybrid electric vehicle conversions have been

based on the version of HSD found in the 2004 and 2005 model year Prius. Early lead -acid battery conversions by CalCars have demonstrated 10 miles (16 km) of ev-only and 20 miles(32 km) of double mileage mixed-mode range. A company planning to offer conversions toconsumers named EDrive systems will be using Valence Li-ion batteries and have 35 miles(56 km) of electric range. Both of these systems leave the existing HSD system mostlyunchanged and could be similarly applied to other hybrid powertrain flavors by simplyreplacing the stock NiMH batteries with a higher capacity battery pack and a charger to refillthem for about $0.03 per mile from standard household outlets. Another provider of a plug -inmodule for the Toyota Prius is Hymotion.



Controversy

As of autumn 2005, the Antonov Automotive Technology BV Plc company has

sued Toyota, the Lexus brand mother company, over alleged patent infringement relating tokey components in the RX 400h's drivetrain and the Toyota Prius hybrid compact car. Thecase has been pending in secret since April 2005, but settlement negotiations did not bring amutually acceptable result. Antonov eventually took legal recourse in the German courtsystem, where decisions are usually made relatively swiftly. The patent holder seeks toimpose a levy on each vehicle sold, which could make the hybrid SUV less competitive.Toyota fought back by seeking to officially invalidate Antono v's relevant patents.

On 1 September 2006 Antonov announced: The Board of Antonov plc announcesthat the Federal Patent Court in Munich has not upheld the validity of the German part of Antonov's patent (EP0414782) against Toyota. A few days earlier, a court in Düsseldorf hadruled that the Toyota Prius driveline breached the Antonov hybrid CVT patent. Equivalent patents are still in force in various countries worldwide. The position is therefore at animpasse, with the Toyota Prius probably breaching the Antonov hybrid CVT patents outsideEurope, Antonov PLC lacking the financial muscle to enforce their patents, and To yota prepared to try to get the Antonov patents cancelled elsewhere if Antonov tries to enforcethem.

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