Innovations in the Electric Power Train, Backed by Decades of Experience
July 9, 2019
Electric-powered vehicles are nothing new. Electric cars were popular in Europe and the United States in the 1890s and early 1900s because they were cleaner, quieter, and easier to start than cars with internal combustion engines (ICEs). Even after gasoline-powered cars took over the consumer market, electric trains and trucks continued to transport coal out of mines and move people through subway tunnels. Electric tow tractors, load carriers, and forklifts kept factories and warehouses running around the world.
Today, increased climate volatility and bans on fossil fuel vehicles drive investments in electric-powered cars, trucks, and buses. More than 125,000 electric commercial vehicles were produced globally in 2017, and a Research and Markets report predicts that number will exceed 1.8 million by 2025.
In the U.S., where online shopping has skyrocketed, delivery companies deploy electric medium-duty trucks and vans to meet the demand more sustainably. In China, strong government incentives and a low rate of car ownership make consumers more inclined toward electric cars, and every five weeks, 9,500 new electric buses take to the roads—the equivalent of the entire London bus fleet.
The challenge of electric propulsion
The electric vehicle (EV) market is far from mature, however. First-generation EV power train solutions are still a dime a dozen, with startups vying with established manufacturers for a position in the market. Suppliers are staying on top of developments so they can adapt quickly as demand for EVs increases.
The big challenge continues to be batteries. Experts expect lithium battery costs to remain high for the next ten years. To get more miles from a charge, manufacturers look for power dense, fuel-efficient powertrain solutions, so that vehicles can be lighter, with room for bigger battery packs.
EV challenges for bearing designers include harsher thermal environments and lighter-weight lubricants, says Christopher Marks, chief engineer of Timken’s off-highway group. Recently promoted, he was formerly Timken’s resident expert on EVs in the on-highway space.
“Lighter-weight lubricants have been a trend for years because they allow for greater efficiencies in drivetrain operation,” he says. “Those lighter lubricants can cause performance issues, however, because we don’t have the film thickness in the bearing and gear contact.”
Operating temperatures in EV gearboxes also tend to be quite high, compared to ICE vehicles. “When you have an electric motor fixed to a gearbox, it’s a large generator of heat,” says Marks. “The only heat generation in a conventional drivetrain is the power loss of the bearings and the gears.”
“It’s a challenge to make bearings last longer in a more aggressive environment than what they conventionally run in,” he says. To meet that challenge, Timken designers rely on the company’s proven processes and vast application knowledge across many industries.
Paving the way with bearing innovation in the conventional and hybrid space
Historically, the automotive industry’s reliance on Timken for application innovation is nothing new. Beginning in 1975, Corporate Average Fuel Economy (CAFE) regulations began raising fuel efficiency targets for cars and light trucks in the U.S. Since then, Timken’s power dense, fuel-efficient (PDFE) tapered roller bearings have played a role in both conventional and electric-ICE hybrid applications.
“The interesting thing about hybrids is, depending on the level of hybrid, the drivetrains don’t change significantly,” says Marks. “PDFE technology is not new, but the design of those bearings has been unique to conventional or hybrid axles.”
Fully electric vehicles, on the other hand, are still evolving, with axles and power trains that can vary significantly from each other and from ICE or hybrid vehicles. One new electric truck design, for example, has four motors—one for each wheel. “All of these innovations offer challenges for our customers,” says Marks. “But it’s still about offering power dense, fuel-efficient solutions to achieve lighter vehicle weight and longer distances in between fuel-ups or, in this case, battery charges.”
Minimizing space requirements, while maximizing power
To solve for EV applications, Timken engineers designed the ePDFE tapered roller bearing product line, building on knowledge they acquired over years of making PDFE bearings for conventional and hybrid vehicles.
“The big difference lies in the macro-geometry,” says Marks. “These bearings and axles tend to be a little smaller than those in conventional vehicles.” Timken ePDFE tapered roller bearings provide a smaller solution, compared to ball bearings, so that customers can downsize shafts and housings to build more power-dense gearboxes.
The internal geometry of ePDFE bearings, on the other hand, makes them more fuel efficient, and that’s where Timken’s micro-geometry technologies play a big role. The manufacturing technologies and engineering standards that the company is known for guide its engineers as they take customer application requirements into the design process.
“We have the technology to help customers design the smallest and most powered gearbox, paving the way for more compact power train designs, overall vehicle weight reduction, lower bearing operating temperatures, and improved power train efficiency,” says Marks. “Timken ePDFE bearings can also help reduce noise, vibration, and harshness, an important factor in vehicles lacking the background rumble of an internal combustion engine.”
Early design collaboration offers optimized results
Marks emphasizes the importance of collaborating with Timken engineers early in the design process, to optimize solutions up front, rather than trying to retrofit them later. “We want to make sure the customer is designing an environment that is beneficial for bearings,” he says. “When they come to us early, we can work with them to create an architecture that allows the bearings to operate at a high level of performance, in terms of longevity and reliability.”
As is typical of youthful industries, Marks says, today’s EV manufacturers are ultra-focused on speed-to-market, rather than on wringing all the potential efficiency and reliability out of their product. “I think there will be room to increase efficiency over time, as EVs begin commanding a greater share of the market,” he says, “just as today on the conventional side, manufacturers are working to increase fuel economy one mile per gallon at a time. You get that by changing all these little things, like the bearings.”
Helping customers navigate a quickly changing market
Electric vehicles are not the only innovation rocking the automotive world. “We’re in the midst of a revolution today,” says Marks, with manufacturers anticipating the rise of ride sharing and autonomous vehicles, as well. “Eventually, we may see lower ownership rates and fewer vehicles in the U.S., for example, but one vehicle will be driving 100,000 miles a year, rather than 12,000-15,000 miles.” A shift of that sort could dramatically affect aftermarket reliability requirements—an area that Timken is positioned well to address.
“People are looking into lots of crystal balls, to try to understand where the industry is going,” says Marks. Long-term, he expects to see a mix of hybrid and all-electric vehicles targeted to the consumer and on-highway commercial markets, and an increase in efficiency standards for off-highway vehicles.
To help EV manufacturers hit their targets, Timken engineers continue doing what they do best: Working closely with customers to develop the ideal solution for each application.