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Switching Roller Finger Follower
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Switching Roller Finger Follower

Our innovative Switching Roller Finger Follower (SRFF) technology for type II overhead camshaft engines enables a variety of variable valve lift strategies including cylinder deactivation to help engine manufacturers achieve emissions and fuel economy regulations. 

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Switching roller finger follower benefits

Pumping losses in an internal combustion engine
Pumping losses in an internal combustion engine

Reduced pumping losses

In spark ignition, engines reduced pumping losses result in increased fuel economy.

Early Intake Valve Closing (EIVC) closes the intake before bottom dead center (BDC) to decrease pumping loss at the valve. We use low lift event for most of low speed operation and it’s always used with cam phasing for optimum timing of low lift.

Cylinder deactivation closes intake and exhaust valves on specific cylinders and forces the remaining cylinders to perform higher specific work. These higher loads force the throttle to be opened more, reducing pumping loss in the active cylinders and improving fuel economy.

eaton variable valve lift friction comparison.jpg

Reduced friction

Friction is a known contributor to the efficiency and fuel economy of modern internal combustion engines. Eaton continues to provide advancements in this area. Our three roller SRFF design offers significant friction reduction (up to 80%) over current state-of-the-art slider pad valvetrain solutions resulting in real-world fuel economy increases.

How SRFF technology can be used

In order to meet future CO2 and NOx regulations, engines will need to rely on advanced combustion processes. Our switching roller finger followers enable powertrain engineers to select combustion process for their particular application.

Single roller SRFF is used in cylinder deactivation (CDA).

The three roller switching roller finger follower design enables a variety of combustion processes:

  • Late Intake Valve Closing (LIVC)
  • Early Intake Valve Closing (EIVC)
  • Internal Exhaust Gas Recirculation (iEGR)
  • Early Exhaust Valve Opening (EEVO)
cylinder deactivation lift curve
Cylinder deactivation (CDA) valve lift curve
internal exhaust gas recirculation lift curve
Internal exhaust gas recirculation (iEGR) valve lift curve
late intake valve closing lift curve
Late intake valve closing (LIVC) valve lift curve
early intake valve closing lift curve
Early intake valve closing (EIVC) valve lift curve

Cylinder Deactivation

Our full lift lost motion, single roller SRFF design provides cylinder deactivation (CDA) when full engine power is not needed, so that remaining, active cylinders run in a higher efficiency mode, increasing fuel economy. This works by reducing throttling losses or pumping work on the active cylinders.

You can find more information about this feature in our cylinder deactivation area.

There are three actuation methods for cylinder deactivation on the Eaton full lift lost motion SRFF: hydraulic, electro-mechanical, and
E-Latch.

Hydraulic Cylinder Deactivation Type II.jpg

Hydraulic Cylinder Deactivation:

  • Hydraulically actuated by oil pressure regulation with OCV (Oil Control Valve)
  • High speed switching capable
  • Precisely controlled mechanical gap/valve lift
  • Low weight, compact design
  • Flexible installation on intake or exhaust side
Mode Engine Speed (rpm) Oil Temperature (degrees Celsius) OCV Signal Switching Port Pressure (bar) Latch Position
Standard Lift 0 to 7200 -40 to 150 De-Enegized 2 to 4 Extended (engaged with inner arm)
CDA (No Lift) Idle to 3500 -20 Energized 20 Reactivated (disengaged with inner arm)

See the Eaton hydraulic actuated, single roller SRFF cylinder deactivation in action.

Electro-mechanical Cylinder Deactivation Type II.jpg

Electro-mechanical Cylinder Deactivation

  • Electro-mechanically achieved by rotating actuation cam with electric motor
    • elimates the need for pressurized oil supply
  • Pre-loading compliance spring enables staging of switching event on base circle
  • -30 degrees Celsius switching capable
  • High speed switching capable (5 milliseconds)
  • Zero rpm switching capable
  • Fail-safe condition capable
  • Precisely controlled mechanical gap/valve lift
  • Low weight, compact design
  • Flexible installation on intake or exhaust side
  • OBD possible based on actuation state
Eaton single roller SRFF CDA elatch with cut away

E-Latch Cylinder Deactivation

  • Very low power consumption
  • Fast response – 3x to 4x faster than hydraulic
  • Optimized power transfer and connector out strategy based on OEM needs
  • Latch state feedback for OBD
  • Ideal for rolling cylinder deactivation

Variable valve lift

For improved fuel economy, performance and drivability in internal combustion engines, Eaton switching roller finger followers enable two modes of operation, allowing gas exchange to be optimized. This is a achieved by a dual lift rocker arm that is actuated by a camshaft with separate cams with low-lift and high-lift profiles.

Three roller SRFFs use Hydraulic, Electro-mechanical and E-Latch actuation technologies.

Hydraulic Variable Valve Lift Type II_b.jpg

Hydraulic variable valve lift

  • Hydraulically actuated by oil pressure regulation with OCV (Oil Control Valve)
  • High speed switching capable
  • Precisely controlled mechanical gap/valve lift
  • Low weight, compact
  • Flexible installation on intake or exhaust side

Watch the 3-Roller SRFF iEGR application in action.

See our high lost motion SRFF in action.

Eaton switching roller finger follower valvetrain

Electro-mechanical variable valve lift

  • Electro-mechanically achieved by rotating actuation cam with electric motor - eliminates the need for pressurized oil supply
  • Pre-Loading compliance spring enables staging of switching event on base circle
  • High speed switching capable (<15ms)
  • -30 degrees Celsius switching capable
  • Zero rpm switching capable
  • Fail-safe condition capable
  • Precisely controlled mechanical gap/valve lift
  • Low weight, compact design
  • Flexible installation on intake or exhaust side
  • OBD possible based on actuation state

Watch the electro-mechanical variable valve lift (VVL) in action.

Types of actuation

Our switching roller finger followers can be activated by a variety of methods including hydraulic, electro-mechanical and electric or E-Latch technology, all of which can be tailored to specific requirements along with increasing efficiency and fuel economy.

Hydraulic actuation is a tried and true technology that reduces switching pressures to support low displacement oil pumps. Electro-mechanical and E-Latch technology enable instant and reliable switching even at very low temperature conditions.  

Hydraulic actuation is a proven technology but it has limitations due to temperature pressure dependencies of engine oil. Electro-Mechanical and E-Latch technologies overcome these challenges by enabling a much larger operating envelope. Additionally, they provide improved onboard diagnostic capabilities and zero rpm switching. 

  Hydraulic Switching Electro-Mechanical Electric or E-Latch
Oil Temp working range (Deg. C) -20 to >150 -30 to >120 -30 to >120
Min Oil Pressure (Bar) 1.5 to >2 N/A N/A
Actuators/Rocker arms 1 actuator/ 4 SRFF 1 actuator/6 SRFF 1 actuator/ 1 Rocker arm
OBD No direct OBD feedback Bank position feedback Individual rocker arm feedback
Minimum RPM Switching Above Idle 0 RPM 0 RPM
Response Time ≈ 15ms < 15ms ≈ 5ms
Rolling activation Very Difficult Possible Possible
Oil Pump Impact Added leakage No impact No impact

Hydraulic actuation

Proven and in production technology. This is the most common and cost-effective actuation method.
Learn more

Electro-mechanical actuation

This technology is production ready now. It enables consistently fast response times and a larger operating envelope for increased fuel economy.
Learn more

E-Latch actuation

Our innovative electric latching technology is the future of variable valve actuation. The on-board coil response time is three to four times faster than hydraulic actuation.
Learn more
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Eaton’s mission is to improve the quality of life and the environment through the use of power management technologies and services. We provide sustainable solutions that help our customers effectively manage electrical, hydraulic, and mechanical power – more safely, more efficiently, and more reliably. Eaton’s 2020 revenues were $17.9 billion, and we sell products to customers in more than 175 countries.
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