GM patent previews new dual-clutch transaxle
General Motors has just been granted a patent for a new, compact, dual-clutch transmission featuring eight, nine, or 10 forward speeds.
Invented by Tejinder Singh and assigned to General Motors Technology Operations LLC, United States patent #10,309,489 seems primarily concerned with making a DCT with improved “packaging.” Technological wonders that they are, DCTs are also complicated mechanisms. As the name indicates, they include two clutches, two power input paths, two gears for every forward speed along with their synchronizers, plus three gears to implement reverse.
That’s a lot of machinery to fit into one case. The patent attempts to create an efficient, responsive, and compact dual-clutch gearbox that takes up as little space as necessary.
Although the invention is described as a “transmission,” the drawings and claims include a differential on the output, so in today’s parlance it could also be called a transaxle, incorporating the final drive in the transmission case.
Besides improved packaging, another goal of the invention is smoothness. When DCTs were first introduced to the market, some consumers complained about shifts that were rougher than those in conventional automatic transmissions with fluid torque converters, and people weren’t used to how DCTs don’t creep when you release the brake like traditional automatic cars do. Should the new transmission actually be an improvement in those areas, we might even see the gearbox show up on some of GM’s more powerful front-wheel-drive passenger models.