LEXUS HYBRID DRIVE:
THE DELIGHT'S IN THE DETAIL

Believe it or not, I’ve come to Lexus HQ to learn about having fun. Shinichi Abe, the man behind Lexus Hybrid Drive technology, clearly knows where the fun lies: ‘Essentially it comes down to manoeuvrability and acceleration performance,’ he explains. ‘The former isn’t really an attribute unique to hybrid, but the latter certainly is.’

To illustrate the process he picks up a prop; it’s a football pump doubling as an engine cylinder. Raising and lowering the handle, he goes through the steps of internal combustion: intake (fuel and air enter the cylinder); compression (the piston rises and squeezes the fuel-air mixture); combustion (the spark plug ignites the mixture, sending the piston downward); and exhaust (the gases from the ignition explosion leave the cylinder).

A gas engine piston goes through several of these steps before it can impart adequate torque to spin the wheels. An electric motor requires no gaseous explosions to create torque, so it can generate it immediately. Pairing an electric motor to a gas engine helps make a vehicle more responsive, and more fun.

ELECTRIC MOTOR

The technical challenges in creating ever-greater performance have been huge. ‘With the electric motor, the larger the current that enters it, the more torque it will produce. But you have to manage this high energy, which is where Power Control Unit plays a vital role. Using new transistors and advanced cooling technology, we’ve been able to create increasingly high performance and an even more compact design,’ Abe says.

Lexus is guided by kakushin, the idea of sudden breakthrough moments. The 2010 RX 450h is a good example. ‘We went from 192g/km of CO₂ emissions to only 145g/km,’ Abe explains. ‘The improvement came down to two innovations: an Atkinson-cycle engine and cooled Exhaust Gas Recirculation [EGR].’

HYBRID DRIVE EFFICIENCY

To explain the Atkinson-cycle, Abe reaches for the pump. Letting a little air back out of the cylinder allows the piston to compress the smaller fuel-air mixture farther up the cylinder than normal. Once the mixture ignites, the gases have more room to expand downward, which results in more pressure on the piston, more torque and better engine efficiency. Regenerative braking also plays a role. At this stage a question comes to mind: ‘OK, we’re at a low 145g/km of CO₂ with the RX 450h. How are you going to improve on that?’

‘There are plans,’ Abe says. ‘But now’s not the time to give away too many secrets.’ Anyway, he adds, the people to ask are the whizz kids on his team. ‘The hybrid area is so young. A few years ago, there was no big pressure. Today it’s a tougher environment,’ Abe says. ‘Each of my guys should aim to be the number one hybrid engineer in the world.’

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