A SEMINAR ON

PIEZOELECTRIC CONTROLLED HYDRAULIC

ACTUATED CAMLESS ENGINE

HISTORY

• The idea of camless engine had its origin as early as 1899,when designs of variable valve timing surfaced.

• Originally, camless engine were developed for use as a design aide to automotive engine manufacturers .

• Later their design have taken on a variety of forms,from electro pneumatic to electro hydraulic based on the use of electric solenoid.

• There have been a few attempts at developing production models of camless engine,most notably by FORD.

• The UNIVERSITY OF SOUTH CAROLINA,department of mechanical engineering was approached in 2000 to consider the development of camless engine with use of piezoelectric actuator.

EXISTING TECHNOLOGY• In a conventional engine the camshaft has been the

primary means of controlling the valve actuation and timimg, and therefore, influencing the overall performance of the vehicle.

• Since the timing of the engine is dependent on the shape of the cam lobes and the rotational velocity of the camshaft,engineers must make decisions early in the automobile development process.

• Maximum efficiency and max power require unique timing characteristics,the cam design must compromise between the two extremes.

CAMLESS ENGINE

• In a camless engine the conventional devices I.e cam, camshaft,rocker arm,push rod etc are replaced by a valve actuating device attached to the engine valves.

• PIEZOELECTRIC CONTROLLED HYDRAULIC ACTUATOR:-

• Different parts:-

• HYDRAULIC AMPLIFIER• SPOOL VALVE• PIEZOELECTRIC STACKS• CONTROL SYSTEM

HYDRAULIC AMPLIFIER

• The major components that makeup the camless engine actuator are two bore plates,one cylinder block and one piston.

• The cylinder incorporates two ports namely A and B through which hydraulic fluid enters or leaves the cylinder.

• The minimum distance between the ports is 10mm.

PISTON-CYLINDER ARRANGEMENT

HYDRAULIC ACTUATOR AND MOUNTING BLOCK ASSEMBLY

FEW DESIGN CONSIDERATION

• The distance between ports A and B centerlines is 17.5 and distance between the closest edges is 10mm.

• The distance between the ports should accommodate the proper translation with a reasonably sized piston without covering the port.

• The piston surface area with the cylinder should be small to reduce the friction between the surfaces.

• The piston itself must be of reasonable length so that it maintains its orientation while translating.A piston that is too short has a greater chance of tilting slightly and becoming jammed within the cylinder bore.

SPOOL VALVE• A spool valve is connected to the hydraulic

actuator. The position of the spool valve determines the flow of fluid into the cylinder.

• Hydraulic fluid is pumped through a ball valve and into the side port of cylinder block.This connection is directly routed to the P port of the spool valve.From there, the position of the spool valve determines where the pressurized fluid goes.

HYDRAULIC AMPLIFIER-SPOOL VALVE UP

HYDRAULIC AMPLIFIER-SPOOL VALVE DOWN

PIEZOELECTRIC ACTUATOR

• A piezoelectric material generates a charge when it is subjected to an input mechanical stress. In the converse effect,the elements develops an output mechanical deformation when an electric field is applied.

• Piezoelectric is selected as the prime material for actuator for several reasons:-

• These materials have high power density.• These materials response well at high frequency,• Piezoelectric actuators are available in geometries

that are readily integrated in other devices.

• Two piezoelectric stacks are used in case of PZT actuator.

• There stacks are mounted on a hinged lever arrangement at a point in the ratio of 5:1.

• The expansion and contraction of PZT stack causes up and down movement of lever.

• As the expansion of PZT due to application of electric current is very less it can’t move spool valves directly.Hence 5:1 lever is used to amplify the displacement.

CONTROL SYSTEM• The control of camless engine system is

facilitated by a series of electrical components that ultimately supply a variable voltage to piezoelectric stacks.

• From various calculation it was calculated that the voltage required to actuate stack is 24V DC.

• Through various testing a conversion factor is calculated i.e 1V DC output to 8V AC input.

• Based on above conversion, the required input of 192V AC should provide 24V DC output.

• The electronic wiring advances from an outlet at 122V AC to a variable output transformer to create 92V AC.

• This 92V AC is doubled plus a small offset through a step up transformer to give 192V AC.

• The resulting 192V AC supplies the AC to DC converter in the HV amplifier box.

• The converter supplies 24V DC to the splitter/amplifier.

• The splitter outputs two voltage signal based on a separate input voltage wave.One output signal is 0-200V DC and other is 200-0V DC.

• These two variable DC signals are based on a separate voltage input supplied by a function generator.

COMPLETE SYSTEM OVERVIEW AND OPERATION

• In the design the two piezoelectric stacks sit on either side of the lever fulcrum The expansion of one of the stacks causes the lever to move.

• For example,if the left piezoelectric stack expands,the lever moves down. Expansion of right PZT stack causes the lever to move up. The movement of the lever causes the motion of the spool valve.

• The expansion of the PZT stack is generated by the input voltage from the HV amplifier box.BY this arrangement the two stacks never expands at the same time.

• The cycling of the expansion from one stack to the other allows the lever to oscillate up and down.

• The oscillation of spool valve directs the hydraulic flow path.Based on the spool’s position,the fluid can either divert to the top of the adjacent piston or the bottom.

• This pressurization causes the piston to displace down or up,respectively.

• This leads to the opening or closing of engine valve.

ADVANTAGES• Variable valve timing is achieved by varying the

input voltage signal to the PZT stack.This will provide tremendous improvement to the next generation of IC engine.

• It provides high power.• Higher fuel efficiency.• Fewer emission.• Main benefit of linear actuator over cam is that the

timing,opening and closing of valve,open length could be managed by the on board computer while running the vehicle.

• No power is needed from crank shaft to rotate cam,so all the power developed in crank shaft is utilized to run the engine.

LIMITATIONS• Biggest limitation is reliability.• Technical challenges have kept camless technology

off the market,such as precisely opening and closing the valves electronically,packaging the system to fit inside the engine and developing the software to operate the valves.

• It is costlier than cam mechanism.• With the camless system there is a strong need for

the auto maker to change the architecture of the engine.which is again very costly and time consuming.

• A slight computer glitch or electronics problem can instantly destroy some engine parts and cause heavy loss.

          

                                                               

THANK YOU

BIBLIOGRAPHY:-WIKIPEDIA.COMGOOGLE.COM

PRESENTED BY:-

Chitralekha Mishra

19ME/02