The all-new Ford Focus offers up exceptional shift quality to drivers, powered in part by an inventive Ford transmission technology that has been waiting nearly 25 years for computing power to catch up to make it a reality. Focus features the Ford PowerShift dry-clutch six-speed automatic transmission, one of the first transmissions to benefit from Torque Hole Filling (THF), a Ford-developed and patented concept and methodology conceived a quarter century ago.
It uses a combination of mathematical algorithms, computer-aided engineering tools and transmission control technologies to fill what is commonly known as the torque hole – the slight hesitation drivers may feel during an upshift when there is a momentary drop in transmission torque output followed by a rise in torque. The torque hole has been inherent to automatic transmissions since the 1940s, said Ford Research Technical Expert Chris Teslak. “Even though much work in controls and calibration has been done over the years, it has remained a major challenge,” he said.
To address this challenge, Dr. Davor Hrovat, a Ford Technical Fellow in Controls Research, authored an invention disclosure in the mid-1980s on how to coordinate engine and transmission controls to help eliminate the torque hole. Further analytical work and simulation revealed this pioneering concept was promising, but the technology needed to implement it wasn’t fully mature yet. Enabling technologies such as electronic throttle control and improved actuators and sensors, coupled with the THF methodology, gave the team of Ford engineers the tools needed to precisely sync transmission and engine to transfer and smooth out the torque during a portion of an upshift lasting a fraction of a second. Adding that little extra torque during the shift helps fill the hole, creating a smoother drive experience for the customer. In internal engineering evaluations using a PowerShift prototype, THF improved shift quality ratings by up to 2 points on a scale of 1 to 10 in comparison to baseline shifts with conventional controls.
To pre-stage this fraction-of-a-second “conversation” between engine and transmission, a certain degree of finesse, coordination and upfront knowledge of what customers perceive as a quality shift was needed. The technology also required the Ford engineering teams from several disciplines to throw away preconceived notions about conventional engine and shift controls. In total, the team logged approximately three years or 6,000 man-hours of computer-aided mathematical modelling, simulation and analysis of engine speeds, torque and clutch capacity in only 24 months real time to prove the THF concept was production-ready. Ford has two U.S. patents covering broad THF applications while several other related patents are pending. Further research is being conducted on how to most effectively incorporate the THF technology into more conventional planetary gear-based transmissions.
