The basics of IVA

Introduction

IVA is a full authority, electro-magnetic, poppet-valve actuation system which can actuate inlet, exhaust or both inlet and exhaust valves on an internal combustion engine. Advanced, multi-stable, electronically controlled,BAT based actuators drive individual desmodromic valve trains for each valve and an Energy recovery spring (ERS) assists to drive or slow the actuator when “boost” is required. 

IVA has different system operating modes that provide an unbeatable control range of valve lift, timing and period; irrespective of crank angle and almost independent of each other – the mechanical link to the crank is completely broken. This gives the same increase in control and performance as analogous digital transitions in auto such as carburettors to fuel injection, or points based ignition with mechanical advance/retard to fully electronic ignition systems.

The actuator

The actuator at the heart of IVA is  purpose designed by Camcon and uses our core BAT principles to achieve its performance. Key features include"

• 12V operation
• Permanent Magnet Motor
• 4 Phase
• 3 stable parking positions
• Energy Recovery Spring (ERS) assisted
• Full 360˚ rotation or part rotation and return • Very high torque density

Basic operation

-The actuator stops at a datum position after each valve event.
-The required event lift, period and timing are calculated and converted into an event profile in the VCU.
-The crank position sensor provides the datum timing for each event.
-The cam is then driven by the actuator to provide the event as calculated.
-For full lift the actuator will complete a full revolution.
-For part lift the actuator will drive the cam to that lift, then reverse direction to close the valve

Modes

- IVA has two operating modes providing an unrivalled range of valve lift, timing and period control virtually independent of each other and irrespective of crank angle
– the mechanical link to the crank is completely broken
- IVA is fast enough to offer two events per cycle at low-mid engine speeds
- Full rotation provides full-lift events at medium to high engine speeds
- IVA has two operating modes providing an unrivalled range of valve lift, timing and period control virtually independent of each other and irrespective of crank angle
– the mechanical link to the crank is completely broken
- IVA is fast enough to offer two events per cycle at low-mid engine speeds
- Bounce events are used to provide partial lift at low to medium engine speeds

Power Consumption

IVA power consumption (including alternator efficiency) is lower than the parasitic losses of a conventional camshaft driven valvetrain in the majority of operating points:

- Inlet only 6000 rpm, 2 valves/cylinder <1.25kW
- Inlet only, idle <<30W

Outline Capability

The current design inputs for IVA yield the following performance surface. These are not absolute constraints:

- Any valve period down to 7ms duration is possible (equivalent to 25° crank at 600 RPM and 252° at 6000)
- Maximum valve lift 7.6mm (achievable at all speeds)
–Full lift is achievable throughout the speed range
–Part lifts down to fractions of a mm are available
- Infinitely variable lift between zero and full lift
–Valve opening and closing points are completely independent of the crank and under user control
–Complex events (e.g. dual lift) and profiled opening can also be used
–Each valve is separately controllable, cycle –by-cycle
- Different events on each inlet or exhaust valve in the same cylinder
- Start valve opening at any required timing