Diesel variable valve actuation
Upcoming diesel engine emission regulations will require significant reductions in NOx and CO2. The key to achieving this is maintaining the aftertreatment temperature in a sweet spot and maximizing the engine's thermodynamic efficiency. Eaton has developed several variable valve actuation technologies for medium- and heavy-duty engines addressing both needs:
- Early / Late Intake Valve Closing (EIVC / LIVC) or "Miller" cycle
- Cylinder Deactivation (CDA)
- Early Exhaust Valve Opening (EEVO)
Eaton variable valve actuation solutions
By deactivating the valves on one or more cylinders, the overall air/fuel ratio is reduced: amount of injected fuel is similar while the air flow is reduced proportionally to the number of deactivated cylinders.
This works to increase the exhaust temperatures and ultimately improve emissions through improved catalyst efficiency. Simultaneously, a fuel efficiency benefit is possible.
EIVC / LIVC - Early / Late Intake Valve Closing
Eaton’s capsule technology can be employed to modulate the intake valve to achieve either early or late valve closing.
Changing the duration of the intake event enables the powertrain engineer to deploy Miller cycle combustion and achieve their fuel economy objectives.
LIVC makes effective compression ratio lower than expansion ratio, increasing efficiency, while increasing exhaust temperature.
- Improves fuel economy by 1-2%
- Enables higher compression ratio
- Keeps the aftertreatment warm
(+40°C at low load) - Eaton mechanical capsule technology enables full switch in one cam revolution and high lift fidelity
Learn more about our Late Intake Valve Closing
CDA - Cylinder Deactivation
By deactivating the valves on one or more cylinders, the overall air/fuel ratio is reduced:
amount of injected fuel is similar while the air flow is reduced proportionally to the number of deactivated cylinders. This works to increase the exhaust temperatures and ultimately improve emissions through improved catalyst efficiency. Simultaneously, a fuel efficiency benefit is possible. Eaton has developed a strategy for maximizing the CDA benefit while maintaining acceptable NHV. This strategy consists of deactivating variable number of cylinders depending on engines lead and load.
By shutting down valves and fuel injection in some of the cylinders, the flow of air through the engine is reduced, increasing the exhaust temperature and improving the efficiency:
- Reduces NOx in low load cycle by 40%+ while reducing CO2 by 5-8%
- NOx reduction up to 90% when combined with advanced aftertreatment
- Activation and deactivation within
1 cam revolution - Enables 1.5 and 2 stroke engine brake strategies
- Compatible with Dynamic Skip Fire (DSF)
Learn more about our Cylinder Deactivation
EEVO - Early Exhaust Valve Opening
Eaton’s capsule technology can be employed to modulate the exhaust valve to achieve early exhaust valve opening during a firing event.
Opening the exhaust valve half way through the expansion, a larger part of the combustion energy goes int heat (vs mechanical work) increasing exhaust temperature:
- Gets aftertreatment hot fast at cold start without the need of an external heating system
- Can open one or two valves
- Compatible with engine brake and other VVA strategies
- Can be activated at any temperature and 0 rpm, when combined with Eaton electro-mechanical actuation technology
Actuation options
Depending on the application and customer requirements, our VVA solutions can have hydraulic or electro-mechanical actuation
Hydraulic Actuation - PLACEHOLDER Image
Electro Mechanical Actuation
Hydraulic Actuation:
the switching element of the VVA rocker is controlled via oil pressure. An oil control valve is used to modify the pressure in the control circuit hence activating and deactivating the system
Electro Mechanical Actuation
The switching element of the VVA rocker is actuated via stationary electromechanical actuator, connected to the rocker arm by a shaft. In its simplest form the actuator has two positions, but it is possible to have a multi-step actuator which enables controlling multiple VVA functions with a single shaft and motor.
Modularity
The VVA solutions presented above are indeed an application of two basic technologies of Eaton: the mechanical capsule and the split rocker. By combining these two technologies, a wide variety of VVA strategies can be realized, even beyond those presented here.
These two technologies have been picked vs alternatives, being the optimal combination of:
- Robustness and reliability
- Fast response time and immediate switching between mode (no intermediate positions)
- Maximum stiffness and lift fidelity
Modular and flexible design
Our VVA capsule approach provides flexibility which enables modifications to the basic cam profile on the fly. Oil commands to different valves can force the valve open or keep them closed when needed, reducing the amount of air going through the cycle, increasing exhaust temperature and improving thermal efficiency.
The LIVC capsule can keep the intake valve open a longer time, which improves the air flow at high engine load. The same type of capsule on the exhaust valve can open it early for higher temperature, or pulse open it during a compression stroke for engine braking.
This modular and flexible allows the same capsule with different oil commands achieve multiple functions allowing OEMs flexibility and choice in the design space. In addition, these solutions are more cost effective than additional aftertreatment.
Diesel engine applications
- Medium-duty
- Heavy-duty
Valvetrain configurations
- Overhead cam
- Overhead valve
Modular capsule design
