Boosting brake pressure without pumps

Features - design components

Dayco Venturi-powered system creates vacuum assist for Ford F-150 truck brakes without mechanical or electrical devices.

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October 16, 2017
Robert Schoenberger
Dayco’s Activac system takes air from an engine manifold and directs it through an aspirator to create a low-pressure region that can be used to generate vacuum.

Jim Miller was trying to make cars go faster, instead his team’s innovation is making them stop faster.

“That’s the nature of innovation. You start down one path, and you end up down another avenue that you never would have expected to travel,” says Miller, director of automotive supplier Dayco’s Valve & Actuator Technologies division.

In 2011, Dayco launched Miller’s group as an in-house startup focused on expanding product offerings. The 112-year-old parts supplier focuses on belts and powertrain components, but corporate leaders saw the need for advanced actuation systems and created the team to explore technologies in that arena. One of the group’s first projects was a valve to manage turbocharger airflow.

Ford engineers saw the technology and had a different thought – brakes.

In Ford’s 2017 F-150 pickup, the Activac system diverts air from the engine manifold to provide vacuum assist for the truck’s power brakes.

Boosting brake performance

When Ford put the 3.5L EcoBoost V-6 engine in the F-150 in 2010, it made a huge bet that truck buyers would be willing to choose a turbocharged V-6 instead of a naturally aspirated V-8 in its most popular vehicle. The market response was huge, and in the years since launch, the twin-turbo engine has become the truck’s most popular engine option.

However, downsizing and boosting creates some engineering challenges. Shrinking the engine means creating less vacuum to power secondary systems. Each system that draws engine power creates a parasitic loss to the vehicle, so the more load that can be removed from the engine, the lower the likelihood of the truck activating its turbochargers, and the higher the fuel efficiency.

For the second-generation 3.5L EcoBoost launched in the 2017 F-150, Ford engineers wanted to get rid of another source of parasitic loss – the brake system’s mechanical vacuum pump.

Paul DiLisio, vice president of program and product management, says downsizing engines forces companies to power brake systems by “adding either a parasitic mechanical vacuum pump or a costly electric vacuum pump to supply enough vacuum to the brake booster. Our system allows you to eliminate the vacuum pump, which will help either cost or improve efficiency.”

Venturi effect

Dayco’s Activac system, called Vacuum on Demand Manager by Ford, operates using the Venturi effect, a phenomenon discovered in the late 1700s by Italian physicist Giovanni Battista Venturi. When fluid, air in this case, passes through a constricted or chocked opening, pressure is lower at that choke point. Dayco engineers used that principle to create an aspirator that takes air coming into the engine and forces it through a tube – wide at both ends and constricted in the middle – creating a small low-pressure area.

“We take a portion of the air naturally coming into the engine and flow it through an aspirator,” Miller explains. “The Venturi effect creates a low-pressure zone at the throat of the device, and we connect that low-pressure zone to the brake-boost canister.”

The low pressure in the aspirator pulls air from the brake-boost canister, supplying more vacuum to the braking system than the engine alone could provide in certain conditions – amplifying engine vacuum. When the brake-boost canister has sufficient vacuum to fully apply the brakes, a signal to the engine control system redirects engine air away from the Activac system.

The aspirator squeezes air through a choke point, using the Venturi effect to create a low-pressure zone.

Miller adds that the system generates enough vacuum from natural engine airflow to eliminate the need for mechanical or electrical boost systems. It’s also lighter, less expensive, offers more vacuum than pumps, and has fewer moving parts.

“We solve a lot of problems without creating new ones,” Miller says. “We check a lot of boxes – lower weight, higher efficiency, eliminating auxiliary pumps, and we improve brake performance.”

Product development

While the target application had been powertrain, Ford engineers saw the potential vacuum that could be produced and adapted Dayco’s technology for the brake system. So even though Dayco’s team developed the basic technology, the first application was based on Ford’s interpretation of that work.

“They came to us with the concept of the system, and they outlined the valve and aspirator that would be needed to make the system work, and we developed those components,” Miller says.

Going from concept to finished product required new skills. Dayco’s long history in auto industry supply wasn’t much help. Working with vacuums is very different than working with belts, Miller says.

“We’re not considering airflow when we’re developing belts. So, we had to develop new expertise to work on this project,” Miller says. “Before it was a physical model, we did quite a bit of computational fluid dynamics (CFD). We went through thousands of iterations of the design, optimizing it through computer modeling before we moved forward to physical models with 3D printing.”

Additive manufacturing allowed Dayco to produce several versions of Activac to test it in pickups before finalizing the design. Once Dayco and Ford engineers were happy with those designs, Dayco selected a supplier for the injection-molded parts and began assembling the systems at its Springdale, Arkansas plant.

DiLisio says while it has been great for the technology’s first application to be in the best-selling vehicle in the United States, he hopes to apply Activac to the powertrain systems for which it was designed.

“Lots of vehicle systems need vacuum,” DiLisio says. “It can be used for crankshaft ventilation, evaporative emissions controls, turbocharger controls, and compressor recirculation valves. Lots of engine control systems rely on vacuum.”

Dayco
www.dayco.com

Ford Motor Co.

www.corporate.ford.com

About the author: Robert Schoenberger is the editor of TMV and can be reached at 216.393.0271 or rschoenberger@gie.net