In this environment friendly era, every OEM and car manufacturers are trying every possible approach to control and regulate emissions from car and follow regulations related to ecology. This has led to produce more clean and downsized engines. As it is known that electric actuation can help in controlling the actuators to actuate the flap or valves in few milliseconds over their stroke. There are two possible solutions to implement it. First, Integration of an air valve should be done prior to the piston. Second, complete variable system(intake) performed by the camshaft replacement using electric actuation of valves, known as camless engine. As per author views to improve engine efficiency air admission parameters need to be adopted to the rotation speed of engine (gasoline primarily). In this paper, a new high-speed rotary solenoid for air pulse valve application and fast linear actuator for variable valve actuation.
Mass-Spring system is highly recommended when high speed actuators are needed. Using a patterned circuit for balancing the force repartition and to compact spring assembly a new structure is developed. The principle of this system is that Rotary actuator is an oscillating mass spring system made of oscillating armature between two statoric parts supporting electric coils. For sizing of actuators two key parameters are stiffness of spring, K and induction(max) allowed in the magnetic circuit. Latching torque evolution graph is studied in order to achieve the circuit sizing. Flux2D software is used to visualize magnetic saturation and compute the total torque. Spring sizing was found to be difficult because stiffness has a greater impact on moving spring inertia. Spiral springs is the proposed solution leading to a very compact design and simple integration. In order to achieve optimization between spring inertia and stiffness a model (analytical) and finite element software is used to study that.
Here the most important requirement was that the system has to keep the positions at rest while maintaining low cost and no current consumption. Such method will allow cylinder deactivation and will help in attaining some driving modes like urban conditions. Considering two actuators per cylinder will increase the cost and magnetic mass than required amount. MMT developed a new linear actuator, which can produce fast displacement. This actuator uses a polarized solenoid stator that acts on a double moving armature on each side of the unique stator part. Such structure is more advantageous as it will help in achieving rest positions at both ends using same magnets. Linear actuator is developed in such a way that the upper coil affects only upper armature and lower coil affects only lower armature. Armatures are linked using shaft so upper airgap is inversely related to lower airgap (i.e. decrease of one increase other). The behavior of the actuator was modeled using analytical calculation and FEM simulation tools.
Linear actuator designed helps in achieving better efficiency of magnets and a low-cost design. The transition is achieved between both end positions, such that springs store energy in rest positions. To keep the armature in the positions there is no need to energize coils and thus there is no need to initialize the middle stroke start position. Latching force achieved is due to the magnets that generates higher force than springs. Magnet allows a safe rest position such that current decreases/cancel magnet force, enabling the springs to take armature off the rest position and here transition occurs. Such actuators were well suited to variable valve actuation because of its cheap possible solution. This prototype uses 4.5g for magnet mass and allows a latching force of about 230 N in both end positions. Higher the load the higher the magnet mass. The linear actuator can work in four different ways namely, Single Phase Unipolar mode (cheapest solution), Single Phase Bipolar mode(evolution), Dual Phase Unipolar Mode (good solution), Dual Phase Bipolar Mode (best and supreme solution).
Rotary and Linear actuator are spring mass systems so their dynamic behavior is same. MMT developed two actuators with fast displacement. Such designs are suitable for improving air intake. First actuator is a compact rotary solenoid having high holding torque achieved using spring systems. Second is a low cost linear polarized solenoid which uses magnet on both ends of stroke and is flexible to electrical strategies.Both designs achieve the transition from one stable position to other in less than 5ms for a large stroke. The prototypes designed for both the actuators will help in improving air intake and thus the solutions.
