مقابلة مع كبير مصممي لكزس LS460..........
Q and A with Satoru Maruyamano
Lexus engineer wanted 8-speed to be world’s first
By MARK RECHTIN | AUTOMOTIVE NEWS EUROPE
AutoWeek | Published 09/05/06, 8:00 am et
Satoru Maruyamano has spent 17 of his 28 years with Toyota Motor developing transmissions. So it made sense that he would be the chief engineer for the 2007 Lexus LS460, which has the world’s first eight-speed automatic transmission. Maruyamano spoke with Automotive News Europe Reporter Mark Rechtin at the car’s press introduction in Salzburg, Austria.
How did you decide it was necessary to have an eight-speed transmission?
We decided right from the start. When we launched the LS430, BMW already had a six-speed, which beat us in the “world first” category. At that time we started studying eight speeds. We met with Aisin at a World Cup game (in Japan) about four years ago about the transmission’s development. The Mercedes S class has seven speeds, but sixth and seventh are so close that we think it’s just a six-speed.
OK, so you’re first. But why do it?
For power, performance and fuel economy. First-gear ratio is very low, and top gear is much higher than that of a six-speed. So in top gear we get low engine rpms and good control logic for improved fuel economy. But we also developed the 4.6-liter engine with big torque, as passing power is very important. We use the 4-5-6-7 gears as the sweet spot of the transmission.
Early in development, we were worried it would be too busy-feeling, too frequent-shifting. So we have several control logics. The computer recognizes a freeway or a winding road for the suitable gear ratio. The previous six-speed also had some transmission noise. So in designing the eight-speed, we needed to look at the various shaft sizes and dimensions at their most basic level of engineering.
Did you begin developing the base model first?
We started the base model first. But r&d on both was almost done together. We had been planning a long-wheelbase version all along, where it would be more luxurious. For example, the tires on the long-wheelbase model would be more plush. The base model had just coil springs, but the long-wheelbase version has coil springs and an air suspension. And within that air suspension, we have a European-tuned suspension and a choice of 18-inch or 19-inch wheels.
It appears you are copying BMW’s “Bangle butt” trunk-lid design ...
The current LS was a boxy four-door. This time we wanted a change. We wanted a lower, more stable feeling. Not that we ignored packaging, but we wanted to pay attention to design. We had to keep interior packaging, and we also had to consider our passive safety crush zones. So we increased the wheelbase and used bigger tires. But if you put big tires on the current LS, the turning radius is too big. So we had to deal with that in the design by increasing the width of the car, which also looks like a stable design.
Why only have a V-8 and a hybrid?
It would have been easy to do a V-12 for Lexus. But it’s very expensive, when you look at the prices BMW, Mercedes and Audi charge. Besides, if we developed a V-12 for the LS, we would be following others, not leading. So we stayed with a hybrid focus instead. The hybrid focus is on fuel economy, but with a hybrid you get all-wheel drive. The competition’s V-12s have great straight-ahead speed.
But at some point a turn comes, and you have to brake. Our hybrid will beat their V-12 power.
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