Lexus RX400h - In Detail

Press Release

RX 400h - At a Glance

 

Hybrid Synergy Drive

·          The first-ever 4WD high performance hybrid SUV

·          3.3-litre petrol engine with a front and a rear electric motor, and a maximum system output of 200kW/272 DIN hp

·          Seamless acceleration from 0-100kph in just 7.6 seconds

·          Lowest premium petrol SUV fuel consumption on the market: 8.1l/100 km in combined cycle .

·          Low CO2 emissions: 192gr/km

·          NOx emissions close to zero

 

Safety

·          Segment first application of Vehicle Dynamics Integrated Management (VDIM), the Lexus' unique advanced vehicle stability control system

·          Electronically Controlled Brake system (ECB) to improve braking performance and brake energy regeneration

·          7 Airbags including the segment first driver knee airbag

·          LIFE ON-BOARD

·          Bluetooth® connectivity

 

Prologue

 

5

RX 400h Chief Engineer Osamu Sadakata, of the Lexus Development Centre-Product Development group, gives his personal insight into Hybrid Synergy Drive®, its importance for the Lexus marque and the possibilities for its future development.

 

A close interest in his father's architectural career sowed the childhood seeds of Mr. Sadakata 's desire to become an engineer. After graduating from high school, he went to university to complete a doctorate in Mechanical

Engineering where, not yet qualified, he had already been identified by Toyota as a potential asset to the company.

 

"In Japan, the recruiting system is slightly different" Mr. Sadakata explains. "Especially in university. And companies often approach you in your last year to find out if you're interested in joining them. At the time, I was drawn to Seiko, but I had the opportunity to go and look round the Toyota Motor Corporation plant on an orientation day." One look, and Mr. Sadakata was hooked. "I was amazed by the sheer scale of the undertaking" he recalls. "The complexities of these huge machines performing such delicate, precision operations... it was such a striking counterpoint to the tiny, intricate process of watch manufacture. I thought, wow, this is amazing. And I decided, on the spot, to go for Toyota."

 

From the outset, Mr. Sadakata was fascinated by the rigorous scrutineering processes essential to the production of cars. "My first job was analysing Noise, Vibration and Harshness" he remembers. "And the first car I was directly involved with was the Crown - a model which only sells in our Japanese market. But, because there weren't two separate divisions when I joined Toyota -Lexus was merely a high quality division with the company- I started working on the first ever Lexus, the LS, at the same time. My specialty area was the study of wind noise around the windows."

 

More recently, far from believing himself already an expert in the field of hybrid drive systems, Mr. Sadakata's appointment to the RX 400h project came as something of a surprise. "At

the time, the decision to run with the RX400h project had not yet been made. But, because of a number of seminars I'd attended over the past few years, top management knew I was interested in new directions and thought".

 

Today, asked to choose from the raft of radical engineering solutions and technological breakthroughs encapsulated in one vehicle, Mr. Sadakata is reluctant to highlight any one element of the RX 400h which he considers to be its most impressive attribute. "Rather than picking one small detail, I would highlight the basic concept of the RX 400h, which is that everything is seamless in the driving experience. Every part, every movement must be seamless, and the handling so smooth that the driver remains unaware of the enormously sophisticated technology at work. I like to think of it as unnoticed technology."

 

In its long term management guidelines "Global Vision 2010" announced in 2002, the Toyota Motor Corporation defined its resolve to be a leader in environmental performance as an absolute imperative. As such, it is actively employed in improving fuel efficiency and reducing the exhaust emissions of conventional petrol and diesel engines, modifying engines so they use alternative fuels such as Compressed Natural Gas, and developing and popularising clean energy vehicles. "Howeve r, to fulfil our own company goals as well as satisfying the different, premium sector aspirations the Lexus customer has his car, the answer", avers Mr. Sadakata, "had to be hybrid technology."

 

"I think the use of hybrid technology will grow and spread through the market" considers Mr. Sadakata. "Currently it's all about how to use petrol as efficiently as possible, allied to

the greater horsepower you achieve. And this is behind the fun-to-drive aspect of the RX 400h."

 

"But, on the other hand, there is another technology, the fuel cell. And it's not that we are dividing these two technological fields.", Mr. Sadakata stresses. "It is merely that fuel cell technology is so complex that we see hybrid drive systems as the first essential step to its successful development. You have to have the one before you can achieve the other. In the end, then, it doesn't matter if the power source is petrol, diesel or even hydrogen; the hybrid system serves all sources as the most efficient way of using energy."

 

"Certainly, development of fuel cell technology will continue" he considers of the future. "But, ultimately, circumstances will decide whether that, or petrol, is at the core of the automobile market. The key point is in how you use the limited resources we have. We still don 't know how long the world's oil resources will last. Perhaps we'll develop ever increasingly efficient petrol engines and the oil will last longer than anticipated. So it's impossible to put a time scale on the compulsory shift to other power sources."

 

That such a fuel cell will be developed for mass-market motoring, Mr. Sadakata considers inevitable. "But, at the moment, there is no infrastructure in place for the mass-production of hydrogen. We must also consider", he is quick to point out, "that most of the manufacturing sources for hydrogen are themselves responsible for pollution, even if the fuel cell itself is 'clean'."

 

"And it's not just the technology" he stresses. "Society itself needs to embrace the new technology. Otherwise it will take a great deal of time and be very difficult indeed to make the change."

 

The World's First Performance Hybrid SUV

 

 In the new RX 400h, the Lexus Division engineers have created completely new, SUV oriented hybrid components based on the Hybrid Synergy Drive® concept.

 

This ground breaking development features the world's first hybrid system to employ a high power front and rear electric motor and a highly efficient petrol engine working in optimum collaboration both to provide an 'intelligent' electric 4-wheel drive capability and significantly improve low to mid-speed acceleration and fuel efficiency, whilst minimising CO2 emissions.

 

RX400h Hybrid Synergy Drive in Action

 

The Lexus RX 400h's exceptionally powerful Hybrid Synergy Drive® system combines the following characteristics to provide both superior fuel efficiency and driving performance:

 

·          First, energy loss reduction -the system automatically stops the engine at low vehicle speed and at idle, thus reducing expenditure of energy that would normally be wasted.

·          Second, energy recovery and re-use -the kinetic energy that would normally be wasted as heat during deceleration and braking is recovered as electric energy, which is then used to power the starter and the electric motor.

·          Third, motor assist -the electric motor assists the engine during acceleration.

·          Fourth, high efficiency operational control -the system maximises the vehicle's overall efficiency by using the electric motor to run the vehicle under operating conditions in which the engine's efficiency is low, and by generating electricity under operating conditions in which the engine's efficiency is high.

·          And fifth, seamless acceleration via electric, Continuously Variable Transmission.

 

Over the course of any journey, the new Hybrid Synergy Drive® system operates in several different modes to maximise the RX 400h's overall efficiency. When the engine is cold and the ignition is switched on, the system will start the engine to warm the unit. Thereafter, at rest, the engine stops automatically to conserve fuel.

 

Under operating conditions of low engine efficiency such as start up and low to mid-range speeds, the vehicle runs on the electric motors alone, thus eradicating CO2 emissions.

 

Under normal driving conditions, engine output is divided by a power split device both to drive the wheels directly and power the generator which, in turn, drives the electric motors and simultaneously charges the high-voltage battery. In these circumstances, power allocation is constantly monitored and adjusted between engine and motors to maximise efficiency. When sudden acceleration is required, engine and electric motors again operate in optimum collaboration with extra power supplied from the battery to boost motor response.

 

Unique to the RX 400h's Hybrid Synergy Drive®, the vehicle's rear wheels are driven by a rear electric motor to provide 'E-four' -Lexus' innovative Electric 4-Wheel Drive system- under various driving conditions. Controlled by the Vehicle Dynamics Integrated Management (VDIM) system, 4-wheel drive is automatically engaged via constantly adjusted front and rear electric motor torque under hard acceleration (both from a standstill and through the gears), when driving through corners and whenever the front wheels lose traction.

 

Moreover, during deceleration and under braking, the engine switches off and front and rear high-output electric motors act as high-output generators driven by all four wheels. This regenerative braking system optimises energy management in the new RX 400h's Hybrid Synergy Drive® system by recovering kinetic energy (normally wasted as heat under braking and deceleration) as electric energy for storage in the high performance battery. Furthermore, under all driving conditions, battery power and energy transfer levels are constantly managed via the engine driven generator obviating any requirement to recharge the system from an external source.

 

At all speeds, the RX 400h's Hybrid Synergy Drive® system monitors itself for optimum performance and fuel efficiency with minimum emissions, either running the electric motors in isolation, the engine in isolation or a combination of both. Details of this appear on a multi-information display in the driver's instrument binnacle. In cars fitted with the satellite navigation system, comprehensive data on power flow and the status of the high voltage battery appear on a 7", full colour monitor.

 

*1 This is calculated by combining the maximum output of the only two independent energy generating sources within the Hybrid Synergy Drive® system, the petrol engine and the battery. Hence the 155kW/211 DIN hp maximum power output of the 3.3 litre V6 combines with the 45kW/61 DIN hp output of the battery.

 

Performance

 

Producing a maximum power output of 200kW/272DIN*1 hp, the second generation Hybrid Synergy Drive® system gives the Lexus RX 400h a maximum speed of 200kph. Via continuously variable transmission, it will accelerate seamlessly from 0-100kph in just 7.6 seconds with none of the expected 'jumps' between the gears.

 

Proving substantially more frugal than rival models of a similar power output, the RX 400h boasts fuel efficiency levels never before achieved in a luxury SUV, returning 9.1l/100km under urban driving conditions, 7.6l/100km on the motorway, and a combined figure of 8.1l/100km.

 

Compliant with EURO IV emission standards, the new Lexus generates NOx emissions close to zero, and returns a CO2 emission figure of just 192g/km in the combined cycle. This represents a substantial reduction of 36% over the emissions of premium sector, V6 SUV competitors. Driving an RX 400h can reduce CO2 emissions by up 2.6 tons per annum*2.

 

*2 Calculation based on the combined EC cycle of SUV competitors V6 petrol engines, with 24,000 km driving a year.

 

"All car manufacturers will have some form of hybrid very soon -or are now planning something.", considers Karl Schlicht, Vice President, Lexus Europe. "And I think it's fair to say that Lexus' dedication to hybrid technology, and our early success, has surprised some other established manufacturers. It only makes sense that when NOx standards start to bite, diesels will become more expensive and hybrids even more attractive.", he continues. "The NOx story has been avoided in Europe, and this needs to change. There is a reason why in other markets, like North America or Japan, NOx standards are stricter than in Europe. Level the standards for particulate emissions globally, and hybrids become very attractive."

 

"Add the performance element offered by the RX 400h, and the proposition becomes even more interesting" says Schlicht. "When you consider global economies of scale, this again tilts the balance towards hybrids. Simplify the standards and take NOx into account, then let the consumer decide… Hybrids will represent a core technological advantage for Lexus. And as for its SUV application in the RX 400h; it's like letting you enjoy a chocolate sundae, but without the guilt."

Suspension

 

The new RX 400h employs a substantially enhanced version of Lexus’ proven, front MacPherson strut and rear dual-link strut suspension system to provide impressive handling characteristics, excellent steering response and high speed straight-line stability. The revised system has been tuned to optimise driving dynamics, combining sporty handling with a comfortable ride and minimal Noise Vibration and Harshness (NVH) to guarantee Lexus refinement under all driving conditions.

 

Front suspension

 

The improved front MacPherson strut suspension system features a weight reducing, pressed steel-plated L-shaped lower arm, incorporating high damping bushings, revised shock absorbers with a redesigned valve and oil and seal refinements to promote more linear damping. The

introduction of yoke control coil springs to reduce body roll, realise a flatter cornering attitude and create added vehicle stability during cornering.

 

The optimisation of the caster angle and the adoption of ‘Nachlauf’ geometry, which offsets the kingpin axis ahead of the axle centre, result in increased caster trail which enhances both straight-line stability and steering feel. The location of the kingpin axle outside the wheel, allied to the addition of a small, well-shaped sub-frame, results in excellent tight-turn performance and a compact turning circle of just 5.7 metres.

 

Lower arm and tie rod geometry has been further refined to suppress changes in toe angle under suspension bounce/ rebound, thus ensuring excellent straight line performance.

And the angled location of the lower arm member with the rear side higher than the front creates an anti-dive suspension geometry effectively to suppress nose-diving under braking.

 

In addition, the front suspension also adopts a small level of negative camber, effectively leaning the top of each front wheel inwards when the vehicle is running in a straight line. Under cornering load, the change in vehicle posture naturally reduces the ground contact camber angle of the outside front wheel, optimising contact between tyre tread pattern and road surface for enhanced, high performance cornering.

 

Rear suspension

 

The dual-link strut rear suspension system features a more rigid axle design incorporating third generation axle bearings for high torsional rigidity. The carefully considered tuning of coil spring and damper rates, stabilisers and bushings within the optimised suspension geometry promotes improved handling stability allied to a more comfortable ride.

 

Electric Power Steering

 

The utilisation of Electric Power Steering (EPS) within the RX 400h offers several advantages over comparable hydraulic systems. Powered by a brushless, 42 volt DC motor and a gear reduction mechanism mounted on the coaxial of the rack shaft, the EPS system consumes electricity only when assistance is required, using no energy when, for instance, driving in a straight line, and therefore helping reduce fuel consumption by approximately 1.5%.

 

The system structure, comprising motor, torque sensor and reduction mechanism, is markedly more compact and noise-free in operation. By introducing a ball screw reduction gear, smooth rotation, high efficiency, and low friction and noise have been achieved.

 

The EPS Electronic Control Unit features a 32-bit CPU to increase signal processing speed, and actuates the DC motor based on signals received from various sensors, including steering torque and vehicle speed sensors. Power assistance characteristics are changed particularly smoothly, providing an enjoyable, seamless steering feel that is light at low speeds and increasingly responsive as vehicle speed builds.

 

The absence of power steering fluid in the system makes it environmentally friendly at the time of disposal; servicing and component removal is easier; and bleeding air from the system is no longer necessary.

 

3.3-Litre V6 Petrol Engine

 

The RX 400h employs the 3MZ-FE engine already familiar to drivers of the RX 330 in the US, but features significant revisions to intake, exhaust, cooling and engine control systems to optimise the unit’s compatibility with Hybrid Synergy Drive®.

 

The 3MZ-FE engine is a 3,311cc, four-cam, 24 valve, V6 petrol unit, employing the Otto cycle for performance orientation, and producing a maximum power of 155kW/211DIN hp @ 5,600rpm and 288Nm of torque @ 4,400rpm.

 

Variable Valve Timing - intelligent (VVT-i) guarantees optimum power under all conditions, increasing low-speed torque, boosting overall power at higher speeds and, in coordination with the hybrid control systems, improving fuel efficiency. The use of ETCS-i (Electronic Throttle Control System-intelligent – replaces traditional cable control between the accelerator pedal and the fuel injection) further enhances fuel efficiency and, allied to VVT-i, contributes to smooth engine starting and stopping with a significant reduction in Noise Vibration and Harshness (NVH) during engine start whilst the vehicle is in motion.

 

The unit has no starter, alternator or serpentine belt, and the Hybrid Synergy Drive® system generator is used to start the engine, rather than a conventional starter motor. Moreover, in order to optimise engine speed control for maximum hybrid system fuel efficiency, engine speed is controlled –taking vehicle speed and throttle depression into consideration- by the generator. Depending on vehicle conditions there are, however, instances when the engine speed is controlled independently by the throttle. When its operation is not required by the hybrid drive system, the generator stops the engine immediately after the fuel supply is cut, at which point the fuel pump is also stopped to reduce auxiliary component electric consumption. The installation of both Electric Power Steering and Electric Air Conditioning also reduces power demand from the engine, further optimising fuel efficiency.

 

In order to accommodate the Hybrid Synergy Drive® system inverter within the engine compartment, the intake system air cleaner assembly is installed directly over the engine. The adoption of a slit resonator helps both to reduce noise and enhance performance.

 

Modifications to the cooling system include a modularised radiator for air condenser and inverter use, realising space savings and component number reductions. An all-aluminium engine radiator has been introduced for easier recycling, and the use of a ring fan with Pulse Width Modulation offers high efficiency combined with noise reduction and a saving in fan control system power.

 

Within the exhaust system, the adoption of a tri-metal (platinum, palladium, and rhodium) catalyst offers excellent anti-deterioration performance both at high temperature and times of low temperature activation. A spring-type variable valve within the main exhaust muffler opens to reduce airflow resistance and enhance output power at high engine speeds, remaining closed in the low revolution range greatly to improve soundproofing performance.

 

Front Power Unit

 

The front power unit consists of the front electric motor, generator, power split mechanism and the motor speed reduction planetary gear. All attendant gearings are laid out in a three shaft, transaxle configuration within the

remarkably compact transmission casing, on an extension of the engine crankshaft. One of the notable characteristics of the new, quieter hybrid system is that it has achieved both a higher power output and a reduction in transmission unit size by combining planetary reduction gears with a newly developed, compact, high speed motor.

 

The hybrid transaxle’s 3.137 final drive, direct gear drive configuration is both more compact and quieter running than comparable chain-driven systems, whilst the absence of clutches, bands, valves or hydraulics ensures low­ maintenance and mechanical durability. The unit has a total mass of 118kg which is 25kg heavier than a 5-speed automatic transmission.

 

Front Electric Motor

 

In order to satisfy the high RX 400h performance targets, a compact, high output motor of unprecedented power was required. The Lexus hybrid system employs a water/oil cooled, AC synchronous type motor of a high-efficiency DC, brushless design operating on AC current. A rotor constructed from stacked, electromagnetic steel plates and Neodymium permanent magnets arranged in an optimum, V configuration combine to maximise drive torque and power output.

 

This, allied to a boost in power supply voltage to 650V, a significant increase in motor rotation speed to a maximum of 12,400rpm and the adoption of a planetary gear to amplify torque through motor speed reduction, has increased power output by approximately 2.48 times that of the Prius motor, despite the respective units being of near identical size.

 

With a power output of 123kW/167DIN hp @ 4,500rpm and 333Nm of torque @ 0-1,500rpm, the new unit boasts the highest output per unit of weight and volume in the world.

 

Generator

 

As with the electric moto r, the water/oil cooled generator is also of the AC synchronous type. The generator’s exceptionally high rotational speed generates increased power to the new, high output motor, significantly enhancing the power supply up to the medium-speed range and improving RX 400h acceleration in the low to medium speed arena.

 

Power split planetary gear

 

The power split device is at the very heart of the RX 400h’s Hybrid Synergy Drive® system. It features a planetary gear set, which is aligned with the generator, front electric motor and planetary reduction gear for motor deceleration, on an extension of the engine crankshaft within the transmission casing.

 

Via two output shafts, the power split device is connected on the one hand to the generator, on the other, to the electric motor and the wheels. Thus the power output of the engine may be transmitted along two separate routes; a mechanical route -incorporating torque from the electric motor- to the drive wheels, and an electrical route to the generator.

 

The device employs a planetary gear set (so called because planetary gears orbit a sun gea r, as in the solar system) to divide the power output of the engine between the two routes. This comprises a central sun gear, an outer ring gear, and intermediary, planetary, pinion gears which engage both the former. The pinion gears are themselves attached to a carrier, enabling them to both rotate around their own axis and the central, sun gear.

 

The generator is connected to the sun gear. The engine is connected to the planetary pinion gear carrier. The electric motor is connected to the outer, ring gea r, itself directly connected to the differential, which drives the wheels. Hence, with power transmitted to it either from the engine, the electric motor, or a combination of the two, the rotational speed of the ring gear determines the speed of the vehicle.

 

In this configuration, with a 72:28% engine torque split between ring and sun gears, the planetary gear set allows for the full range of power transmission options inherent in the Hybrid Synergy Drive® system.

 

During initial start up and at slow speeds, the engine is not running and the planetary pinion gear carrier is stationary. Powered by the electric motor, the ring gear revolves, driving the wheels and, via the pinion gears revolving on the stationary carrier, rotates the sun gear attached to the generator.

 

To start the engine as vehicle speed increases, momentarily stopping the rotation of the sun gear generates sufficient force (via the ring gear’s rotation of the planetary gears) to set the planetary pinion gear carrier in motion, turning the engine crankshaft. Once the engine has started, it transmits power back through the pinion gears on the revolving carrier to both the outer ring gear, driving the wheels, and the inner sun gear. Rotated by the sun gear, the generator supplies electric power, via the power control unit, either to recharge the battery or drive the motor.

 

During full acceleration, when both engine and motor operate in tandem to drive the wheels, more power is supplied by the battery to the motor, and engine output increases. Under these circumstances, slowing or even stopping the rotation of the generator’s sun gear diverts more of the engine ’s rotational force through the pinion gears to the outer ring gea r, transmitting additional power to the wheels.

 

Motor speed reduction planetary gear

 

The secret of the new, 123kW/167DIN hp electric motor’s compact dimensions lies in its connection to a second, dedicated, rear planetary reduction gear, also aligned with the power split device and generator, on the engine crankshaft.

 

Once again, this planetary gear system comprises a central sun gear, an outer ring gear, and intermediary, planetary, pinion gears which engage both the former. Within this mechanism, however, sun gear is connected to the motor, and the ring gear is connected to the power output shaft. Moreover, the intermediary, pinion gears are connected to a carrier which, in this case, is fixed to the transmission casing and does not rotate.

 

When the motor drives the sun gear, the planetary pinion gears rotate on their own axis, causing the ring gear to revolve. Due to the gear ratio differential, the rotational speed of the ring gear is slower than that of the sun gear. Therefore, as the motor’s rotary speed is reduced, motor torque is increased.

 

Via the gearing of this motor speed reduction device, the motor torque becomes 1: 2.478. Since motor size is proportional to motor torque, the use of the planetary reduction gear allows for the generation of torque appropriate to the performance requirements of the RX 400h within a remarkably compact motor design.

 

Electronically controlled Continuously Variable Transmission (E-CVT)

 

In conjunction with this unique, hybrid transaxle drive system, the new Lexus RX 400h further benefits from an electronically controlled, Continuously Variable Transmission (E-CVT) which simulates a continuous variation of the transmission ’s current ratio by selectively controlling the rpm of the engine, generator and electric motor. As a result, the engine and the motors operate at the most efficient points regardless of the vehicle’s speed. The E-CVT in the RX 400h provides seamless acceleration without the shift point felt with conventional transmission. Transmission friction losses have also been reduced by some 30% through the use of ball-bearings and low viscosity oil.

High-Voltage Battery

 

The RX 400h Hybrid Synergy Drive® system features a new, high output, nickel-metal hydride 288 volt battery. The battery is linked to a monitoring unit with a Hybrid Vehicle-Electronic Control Unit (HV-ECU), which monitors battery recharging conditions, detects problems, performs fail-safe system management and controls the battery cooling fan system.

 

The 69kg, 8-cell battery module (1.2V per cell) assembly, comprising 30 in-line bus bar modules connected in series, is divided into three sections to allow its location under the rear seats without compromising rear seat accommodation in any way.

 

The battery and all its related components are encased in a sealed metal casing. This casing meets the highest standards of protection, shielding vehicle occupants from electromagnetic fields. In the event of an accident, crash sensors initiate the HV-ECU’s immediate disconnection of the battery.

 

The introduction of a metallic battery casing has enabled a considerable reduction in size of the battery module over that of previous, resin casing constructions. The overall height of the battery pack has been reduced by 40mm (some 22%) compared to the previous Hybrid Vehicle battery pack.

 

The use of a metallic casing also contributes to an enhanced cooling performance. Each of the three battery module assemblies is equipped with its own, dedicated air-cooling fan. The fans are driven by brushless motors, allowing for compact design, high efficiency and ultra-quiet operation. Cabin air is brought in through three intake vents located under the front of the rear seats, and flows from top to bottom between the battery modules causing a heat­exchange effect. The air is exhausted from the rear of the battery pack into an under-floor plenum, from which it is dispersed both back into the cabin and to the outside air.

 

Constantly recharged by the operation of the hybrid drive system, the battery requires no external charging throughout the life of the vehicle.

 

Power Control Unit

 

The power control unit consists of a voltage boost converte r, inverter and DC/DC converter, controlled by a motor control ECU which receives commands from the Hybrid Vehicle Control ECU.

 

By installing a new high voltage power circuit within the power control unit, the voltage of both the electric motor and generator has been increased to 650V. According to the formula ‘Power = Voltage x Current’, an increase in voltage enables a reduction in current, and allows for a decrease in the size of the inverter and, hence, the power control unit as a whole. Moreover, the reduction in current minimises energy loss, thus improving system efficiency.

 

The inverter within the Hybrid Synergy Drive®’s power control unit converts a direct current (DC) from the battery into an alternating current (AC), simultaneously boosting the voltage, which then drives the electric motor. A DC/DC converter which adapts the main battery DC voltage to 12V DC auxiliary system voltage is built into the same unit.

 

The boosting of battery voltage and conversion to AC power is carried out within the inverter by a unique semiconductor switching device, the Insulated Gate Bipolar Transistor (IGBT). Since the current in question is significant, minimising heat generation is an important consideration, and the IGBT has been finely tuned down to the crystal level to achieve high efficiency allied to the lowest possible levels of heat generation.

 

Rear Power Unit

 

The rear drive unit consists of a second 650 volt electric motor driving the rear wheels when necessary, to provide Electric 4-Wheel Drive. The motor and attendant, three shaft, direct drive gearing are incorporated in one compact, 40kg transaxle casing mounted on a dual anti-vibration support mechanism to minimise NVH. As with the front unit, the absence of clutches, bands, valves or hydraulics ensures low maintenance and mechanical durability.

 

Activated by the RX 400h’s sophisticated Vehicle Dynamics Integrated Management system working in conjunction with the power control unit, this rear unit is mechanically independent of the front drive system, requiring no transfer or propeller shaft connection.

 

Rear Electric Motor

 

Spinning at up to 10,752 rpm, the air cooled, permanent magnet, 650 volt rear electric motor generates a maximum output of 50kW/67DIN hp @ 4,610-5,120rpm and 130Nm of torque @ 0-610rpm. The motor drives the rear axle through speed reduction gearing with a ratio of 6.859:1.

 

E-Four’ Electric 4-Wheel Drive

 

Unique to the Lexus’ Hybrid Synergy Drive®, Electric 4-Wheel Drive is afforded the RX 400h via its rear drive unit. The ‘E-Four’ system has been designed to effortlessly fulfil the fundamental objective of practical, everyday, 4-wheel drive performance equivalent to that provided by traditional, mechanical 4x4 drive systems whilst, through the automatic deactivation of rear wheel drive when it is not required, simultaneously realising the peerless fuel efficiency of a hybrid vehicle.

 

‘E-Four’ Electric 4-Wheel Drive is activated, and continuously adjusted, by the skid control computer within the RX 400h’s sophisticated Vehicle Dynamics Integrated Management system, working in conjunction with the Hybrid Synergy Drive® system’s power control unit.

 

Provided by a variety of sensors, vehicle status information including speed, acceleration and steering angle, is input into the skid control computer, along with shift position and driver demanded torque requirements supplied by the hybrid drive system control computer. The skid control computer calculates the optimum front/rear wheel distribution ratio of driving torque, which is then effected by the hybrid drive system computer’s activation -via the power split device- of the front and rear drive units.

 

Under acceleration, when driving on slippery roads, the necessary front and rear wheel torque distribution is constantly recalculated and optimum drive torque transmitted to the appropriate wheels.

 

Under normal driving conditions, to enhance fuel efficiency, front wheel drive is employed and the rear drive unit is inactive. However, when driving on a slick road surface, or if acceleration, a left, right or U-turn, or tight cornering is required, electronic control once again optimises and constantly adjusts the distribution of front and rear wheel drive torque to promote a stable driving performance.

 

During deceleration, the rear drive unit motor operates as a generator to collect kinetic energy and recharge the main battery, thus further enhancing overall Hybrid Synergy Drive® system efficiency.

 

ÂÂÂÂ

The new RX 400h is comprehensively equipped with technologically advanced active and passive safety systems, offering an advanced level of occupant safety.

 

Active Safety

 

Vehicle Dynamics Integrated Management (VDIM)

 

Until now, active safety systems such as Anti-Lock Brakes (ABS), Traction Control (TRC) and Vehicle Stability Control (VSC) have tended to act independently. As such, their successful operational combination has been limited and, hence, their optimal performance abilities unrealised.

 

As installed in the new Lexus RX 400h, the Vehicle Dynamics Integrated Management system (VDIM) has been developed specifically to integrate these various systems, greatly improving active safety and enhancing vehicle performance across the full driving spectrum.

 

Moreover, whereas conventional active safety systems are only activated immediately after a limit of the vehicle’s performance envelope has been reached, VDIM activates control before that limit is realised. As a result, the limits of the vehicle’s performance threshold is more difficult to reach, whilst offering smoother vehicle behaviour at this threshold through less obtrusive intervention and, hence, a more pleasurable drive.

 

The core of the VDIM system is the control execution programme built into the Electronic Control Unit (ECU) of the Electronically Controlled Brake system (ECB). In order to obtain a comprehensive measure of driver operation and vehicle conditions, the VDIM system constantly acquires information from various sensors throughout the RX 400h, including brake master cylinder pressure, brake pedal stroke, steering angle, accelerator pedal stroke, vehicle yaw rate, the vehicle acceleration, wheel rotational speeds, brake wheel cylinder pressure at each wheel, and Hybrid Vehicle system output torque.

 

VDIM not only integrates the RX 400h’s ABS, TRC, VSC and EBD braking system functions with the Electronic Power Steering, but also co-ordinates control of the Hybrid Synergy Drive® and Electric 4-Wheel Drive systems. By the application of ‘integrated’ control of all the elements related to vehicle movement, including motor torque, brakes and steering, VDIM not only optimises the activation of braking, stability and traction control systems, but also assist the driver by making the correct steering action easier and incorrect action more difficult.

 

Within Vehicle Stability Control operation, for instance, a variation in left and right hand tyre grip could pull the vehicle to one side under braking. VDIM inputs steering torque to counteract the imbalance in left and right hand side braking force, providing steering assistance that reduces the steering wheel pull (torque steer) and allows the driver to make course corrections more easily.

 

When braking in a corner, a forward load shift may result in loss of rear tyre grip, and resultant oversteer. Steering wheel torque will be applied in the counter-steering (opposite lock) direction. Through the Electronic Brakeforce Distribution function, the use of linear brake actuators makes it possible to begin control before the vehicle’s limit has been reached. The VDIM system apportions the appropriate braking force to each wheel, ensuring continued vehicle stability by pre-emptively restraining the spinning tendency, whilst contributing to superior braking performance.

 

Under even stronger braking in a corner, front wheel lock-up and loss of grip may result in understeer. The steering torque assist will first help the driver to tighten the steering trajectory. However, if the driver applies a too great steering turn, then VDIM will apply steering torque in the reverse direction to help the driver bringing the vehicle back under control. By once again independently controlling the braking force to all four wheels via the EBD system, VDIM helps to prevent front wheel lock-up and regain vehicle balance, offering seamless control until the conventional ABS and VSC functions take over.

 

Electronically Controlled Brake System (ECB)

 

Via powerful, 319mm ventilated front and 288mm rear disc brakes, “by-wire� ECB system facilitates the RX 400h’s ABS, TRC, VSC, BA and EBD braking functions. ECB not only improves overall vehicle braking performance, but also facilitates improved brake energy regeneration.

 

Within the system, independent hydraulic braking power is applied to each of the four wheels. A sensor detects the amount of force being applied to the brake pedal.

The hydraulic braking power is then calculated and applied to each wheel as necessary by ECU adjustment of pressure at the hydraulic source.

 

The system operation employs a combination of hydraulic braking power and regenerative power from the front and rear electric motors under deceleration. A hydraulic pressure control function balances the total braking force between that supplied by hydraulics and motors.

 

Brake Assist

 

An integral Brake Assist function automatically enhances a driver’s braking when the braking speed is judged to be faster than usual, and emergency braking is necessary. A computer recognises this condition based on information fed from the master cylinder pressure sensor and pedal stroke sensor of the ECB system. The brake actuator then increases the wheel cylinder hydraulic pressure and, hence, the braking force.

 

Such a system has consistently proven effective when the driver is in a state of panic and may not apply sufficient brake pedal force, or when the driver is unable to continue applying sufficient brake pedal pressure over time, resulting in deteriorating braking force.

 

Intelligent Adaptive Front Lighting system (I-AFS)

 

The new RX 400h also features the Intelligent Adaptive Front Lighting System (I-AFS), which swivels the High Intensity Discharge (HID) headlamps up to 15 degrees, helping to illuminate a bend as the driver steers into it.

 

Unlike rival systems which are merely linked directly to the vehicle’s steering or use additional lights, Intelligent AFS controls the lighting direction. Employing vehicle speed and steering angle information, I-AFS uses an electronic controller to calculate the optimum sweep of the illuminated area when cornering, swinging the projector headlight to the inner side of the cornering directing to effect a wider field of illumination.

Passive Safety

 

Impact absorbent structure

 

Within a body shell of high torsional stiffness, the overall structural strength of the new SUV is complemented by an impact-absorbent structure which is designed to optimise both offset deformable barrier front-end and head-on collision performance, minimising the transmission of impact energy to, and deformation of, the passenger compartment.

 

The installation of a reinforced rear floor member minimises body deformation caused by a rear end, offset collision, and also helps to prevent fuel tank leakage both during and after an impact.

 

Further driver protection is also afforded by an energy absorbing mechanism in the steering column which, in the event of impact transmission to the steering mechanism, moves the entire column forwards, away from the driver. The RX 400h is also equipped with a collapsible pedal system to minimise injuries to the driver’s feet in the event of a frontal collision.

 

Airbags

 

The new Lexus RX 400h benefits from no less than 7 airbags. Two-stage Dual Supplemental Restraint System (SRS) “intelligent� front airbags employ sensors to determine the severity of an impact and automatically control the force

of bag deployment. An SRS driver’s knee airbag deploys from the lower part of the instrument panel simultaneously to the front airbag. Extra large driver and passenger TAP (Thorax Abdomen Pelvis) side airbags feature a capacity of 16 litres - at least 6 litres greater than conventional side airbags- for torso, abdomen and pelvis protection.

 

The operation of front and rear side curtain shield airbags is now further enhanced through roll-over sensor activation. Moreover, whilst the crash sensor installed in the lower part of the central pillar simultaneously deploys both curtain shield and side airbags, the sensor installed in the lower part of the rear quarter pillar activates the curtain airbags only, thus minimising unnecessary airbag deployment.

 

Exterior Design

 

Based on the innovative, elegant styling of the RX 300, the RX 400h may be instantly identified within the RX range through a number of exclusive design changes.

 

A new, muscular, sporting front bumper design features a large central opening that aids cooling of the hybrid system, and integral, projection lens fog lamps.

 

The new front grille features vertical bars of variable thickness and sharp horizontal bars supporting the Lexus badge, both readily identifying the RX 400h as a member of the Lexus family. The Lexus badge has been enlarged to harmonise with the new grille design.

 

The use of LED (Light-Emitting Diode) illumination within the rear combination lamps and a crystalline cut shape for the reflector lenses creates a jewel-like appearance to the RX 400h’s tail light cluster. The addition of a louver to the tail and stop lamp section reinforces a horizontal accent within the cluster. And the first use of rear surface evaporation for the LED reflector ensures a powerful radiance even when the lamps are not illuminated. LED elements light up ten times faster than conventional lamps, representing approximately 6 metres of reaction time at 100 kph, a distance that can be critical in the avoidance of a collision. The LED tail lamp illumination also reduces electricity consumption, enhances fuel efficiency and offers maintenance-free use throughout the vehicle lifetime.

 

Ultraviolet ray reduction glass is introduced for all glazing, to reduce sunlight penetration and cut solar gain by more than 90%. Dark grey glass is employed for the rear door, quarter panel and tailgate glazing to afford rear seat privacy and promote a tighter, more compact appearance to the overall vehicle design. Water repellent glass has also been introduced to the front door windows to enhance wet weather visibility.

 

The RX model range boasts class-leading aerodynamics, with particular emphasis on the eradication of wind noise. To promote both high speed straight line-stability and excellent fuel economy, careful consideration had been given to controlling the airflow convergence at the back of the RX 400h. Front and rear tyre fairings control wheel arch airflow to lower wind noise and enhance stability, whilst the addition of numerous aerodynamic under-body elements further promotes vehicle stability, helps reduce wind noise to a minimum and lowers the RX 400h’s Cd value to 0.33.

 

The new Lexus runs on unique, 18" x 7", five-spoke allow wheels fitted with P235/55 R 18 tyres, and is available in a range of seven body colours.

 

Interior Design

 

Retaining the all luxury, practicality and ergonomic excellence of the RX 300, including split/folding rear seats, a flat floor loadspace and a power operated tailgate, the RX 400h passenger compartment has been further improved through numerous revisions which identify the new hybrid as the performance flagship of the RX model range.

 

Aluminium-style inserts detailing replaces wood accents surrounding the revised centre console control panel, and elsewhere throughout the interior. A multi-function overhead console includes right and left map reading lamps, cabin interior illumination, a pop-open glasses holder and an intruder sensor, whilst both driver and front passenger sun visors feature an illuminated vanity mirror with dimmer adjustment.

 

Within the three pod, “Optitron�, driver’s instrument panel, a power meter replaces the tachometer to the left, whilst a new multi-function display is also included centrally within the cluster. In cars fitted with the satellite navigation system, comprehensive data on power flow and the status of the high voltage battery can be accessed via a 7", full colour monitor within the centre console.

 

In common with all Lexus models, the new RX 400h sets class-leading standards in Noise Vibration and Harshness (NVH) reduction, sound absorption and vibration damping to offer calm within the cabin.

 

Vibration damping has been optimised through new gussets and reinforcements further to strengthen the highly rigid bodyshell, a chain-free, direct gear drive in the front transaxle and a new, noise reducing design of the radiator cooling fan blade. Road and engine noise have been rigorously suppressed through the comprehensive use of sound proofing materials throughout the engine and passenger compartments, including sound insulating windscreen glass and a new, foamed damping coat material that adheres to the entire floor panel, treating it as an entire acoustic system. This affords enhanced road noise reduction, whilst achieving a 20% reduction in the weight of soundproofing materials. Significant improvements in wind noise reduction have been achieved within the new RX 400h through the adoption of a flush mounted A pillar moulding, an increase in front door and windscreen glazing thickness, the installation of bonnet, bumper and apron seals and the addition of sound absorbent within the A, B and C pillars.

 

On-Board Comfort

 

The new RX 400h interior is equipped with a comprehensive range of technologically advanced equipment designed both to simplify and enhance life on board.

 

Air-conditioning with electric compressor

 

Unique to Lexus, the RX 400h features an innovative electric, air-conditioning compressor with a built-in inverter and brushless, DC motor.

 

Unlike conventional passenger car air-conditioning units, wherein the compressor is powered by the vehicle engine, the compressor of the RX 400h is powered by the high voltage battery, and compressor revolution speed is controlled within specific boundaries by the integrated inverter. Thus, the need to idle the engine simply to cool the vehicle interior is eliminated, vehicle fuel efficiency is not compromised, and cooling efficiency is greatly enhanced.

 

The air-conditioning layout incorporates a Revolutionary Slim (RS) evaporator and Straight Flow Aluminium-II (SFA-II) heater cores at both the front and rear of the unit, maximising front foot-well space. The compact RS evaporator provides excellent cooling performance, whilst an anti-bacterial treated resin coating helps curtail the bad odours caused by bacteria proliferation.

 

To enhance comfort, a sophisticated neural network with fully independent driver and front passenger controls has been introduced to the automatic air-conditioning system.

 

In addition, it is now possible to supply both warm and cool air to the rear console vents, whilst a new humidity sensor, integral to the cabin temperature sensor, further helps to enhance comfort by preventing the cabin air from becoming too dry.

 

When a desired cabin temperature is set, the air-conditioner ECU checks cabin air temperature and humidity, as well as outdoor temperature and solar heat, and then calculates the objective compressor speed required for the targeted temperature. Since the inverter provides accurate compressor speed control, optimum cooling performance and cabin humidity are achieved both quickly and efficiently.

 

Lexus Navigation system with Bluetooth® wireless telephone

 

The new RX 400h’s Lexus Navigation system uses the GPS Global Positioning System allied to map data from a DVD to indicate the vehicle’s position on an Electronic Multi-Vision (EMV) 7", full-colou r, touch sensitive, centre console display screen, and give both visual and voice guidance to a selected destination. One single DVD covers the whole of Europe, and the Dynamic Route Guidance* (DRG) facility constantly updates the navigation system on traffic conditions, suggesting alternative routes to avoid congestion, accidents and delays.

 

The upgraded system includes voice activation in a choice of 2 languages, a revised LCD display with improved clarity and a background colour setting function, and the addition of Bluetooth®, hands-free, mobile phone connectivity. Whenever a mobile phone is in the vehicle, the hands-free system is automatically activated; the phonebook is transferred and is accessible through the EMV (up to 500 numbers can be stored), whilst sound is channelled through the audio system. The new RX 400h further includes steering wheel switches for phone and voice activation, the phone interface being displayed on the centre console screen.

 

Audio system

 

The class-leading acoustics of the RX 400h interior are complemented by a choice of advanced audio systems including a Lexus 8-speaker system with an in-dash 6 CD player and Automatic Sound Leveliser (ASL). The top-of-the­range system is a 240W Mark Levinson® design featuring an ultra-low distortion, 24-bit Digital Signal Processor and 11 speakers, including a 230mm ceramic woofer.

 

Lexus Parking Assist Monitor

 

The new Lexus RX 400h’s Parking Assist Monitor features a small camera discreetly installed on the tailgate handle, which displays a wide-angle, rear-view image on the centre console EMV display screen whenever reverse gear is selected. Vehicle width and bumper edge guidelines on the screen provide additional assistance for kerbside parallel parking and manoeuvring into tight spaces.

 

The Bluetooth® word mark and logos are owned by the Bluetooth SIC, Inc. and any use of such marks by Toyota Motor Corporation is under license.

 

* Available in Austria, Belgium, Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, Switzerland and United Kingdom

 

In addition to obtaining the international ISO Standard for environmental management, the Kyushu plant has adopted numerous additional environmental protection measures. A Zero Landfill Waste Campaign has succeeded in reducing landfill waste to just 2% of its 1999 total, and this figure will be further lowered through advanced sorting techniques and ties with new recycling companies. The development of clean energy systems is encouraged, both by employing natural gas and promoting the use of cogeneration systems. The facility is also actively pursuing new solar light generation technologies. The Kyushu plant takes in some 4,000 tons of water each day. Treated in the Aqua Control Centre, no water is discharged until it meets in-house standards, which exceed those of local and national government regulations. Furthermore, to reduce chemical emissions, the plant has introduced a monitoring system for the tracking of chemicals –such as organic solvents ­released into the environment.

 

This year, following a 25 billion yen investment facilitating both plant expansion and employment of the 2,000 more staff necessary to meet anticipated hybrid demand, Kyushu plant will become the sole manufacturer of all Lexus hybrid vehicles. With RX 400h manufacturing which started mid-March, Lexus anticipates the production of 36,400 RX 400h models in 2005, of which 6,200 will constitute the Japanese market version. Ultimately, domestic and overseas models of the RX 400h will represent some 14% of the Kyushu plant’s 264,000 units total annual vehicle production.

 

The numerous hybrid components are sourced from elsewhere: The high-voltage battery is produced at Panasonic EV Energy, the front transaxle at a headquarter plant, the rear transaxle at both headquarter and Kyushu plants, and the power control unit at Toyota Hirose and Denso plants.

 

Hybrid vehicle production does not require the installation of bespoke production lines; the RX 400h and RX 300 are produced on the same assembly line. As with the production of any new model, which introduces a new construction sequence and components, the workforce does require some training, but this is no longer or more complex than that required for a conventionally powered model.

Exterior Dimensions

 

Interior Dimensions

 

Technical Specifications