Camless Engine Report

8/18/2019 Camless Engine Report

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CAMLESS ENGINE

A Seminar Report

submitted in partial fulfilment of the requirements for the

award of the degree of B!e"h in Me"hani"al Engineering

under Bi#u $attnai% &ni'ersit( of !e"hnolog(

b(

)AR&N ANAN*

Regd No+ ,-.,--/01/

&nder the Guidan"e of

*R *ILI$ 2&MAR SA3&

4$rof5 *ept of Me"hani"al Engineering6

*E$AR!MEN! 78 MEC3ANICAL ENGINEERING

*RIEMS5 C&!!AC25 7*IS3A

7C!7BER -.,9


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CER!I8ICA!E

This is to certify that the Seminar entitled :CAMLESS

ENGINE; presented by )AR&N ANAN* bearing Registration

No ,-.,--/01/of Me"hani"al Engineering in *RIEMS has been completed successfully.

This is in partial fulfilment of the requirements of Bachelor

Degree in Mechanical Engineering under Biju Pattnaik ni!ersity

of Technology" #ourkela" $disha.

% &ish her' him success in all future endea!ours.

Under The Guidance of

Prof.Shibabrata Mohapatra $rof 4*r6 *ilip 2umar Sahoo (Seminar incharge) ( Seminar Guide )Dept. of Mechanical Engg. Department of Mechanical Engg.

Prof. Pranab Kishore Dash

HOD, (Dept. of Mechanical Engg.)

Date:-


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A"%nowledgements

% &ould like to e(press my deep and sincere gratitude to my guide"

*R *ILI$ 2&MAR SA3&" of Mechanical Engineering for hisunflagging support and continuous encouragement throughout the

seminar &ork. )ithout his guidance and persistent help this report

&ould not ha!e been possible.

% must ackno&ledge the faculties and staffs of Mechanical

Engineering department for their constant support.

%t*s my great pleasure to ackno&ledge my colleagues for

pro!iding their support and moti!ation.

NAME< )AR&N ANAN*

*epartment of Me"hani"al Engineering

RegdNo = ,-.,--/01/


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ABS!RAC!

The cam has been an integral part of the %+ engine from its in!ention. The cam

controls the breathing channels of the %+ engines" that is" the !al!es through &hich thefuel air mi(ture ,in S% engines- or air ,in +% engines- is supplied and e(haust dri!enout. Beside by demands for better fuel economy" more po&er" and less pollution"motor engineers around the &orld are pursuing a radical camless design that

promisesto deli!er the internal combustion engine s biggest efficiency impro!ement inyears. The aim of all this effort is liberation from a constraint that has handcuffed

performance since the birth of the internal combustion engine more than a centuryago. +amless engine technology is soon to be a reality for commercial !ehicles. %nthecamless !al!e train" the !al!e motion is controlled directly by a !al!e actuator there isno camshaft or connecting mechanisms. Precise electronic circuit controls theoperationof the mechanism" thus bringing in more fle(ibility and accuracy in openingandclosing the !al!es. The seminar looks at the &orking of the electronicallycontrolledcamless engine &ith electromechanical !al!e actuator" its general featuresand benefit o!er con!entional engine The engines po&ering today s !ehicles" &hether they burn gasoline or dieselfuel" rely on a system of !al!es to admit fuel and air to thecylinders and to let e(haustgases escape after combustion. #otating steel camshafts&ith precisionmachined egg shaped lobes" or cams" are the hardtooled brains of thesystem. They push open the!al!es at the proper time and guide their closure" typicallythrough an arrangement ofpushrods" rocker arms" and other hard&are. Stiff springs

return the !al!es to theirclosed position.


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!able of Contents

.,IN!R7*&C!I7N

.- >or%ing 7f a $ushrod Engine

.0 Cran%shaft

.? Camshaft

.9 >or%ing

.@ An o'er'iew of "amless Engine

. Camless 'al'e train

.1 3(drauli" $endulum

./ )al'e opening and "losing

,. )al'e motion "ontrol

,, &nequal lift modifier

,- C(linder 3ead

,0 Components of "amless engine

,? Engine )al'e

,9 3(drauli" $ump

,@ Solenoid )al'e

, 3igh pressure pump

,1 Low pressure pump

,/ Cool down A""umulator

-. Ad'antages

-, Con"lusion

-- Bibliograph(


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8IGN7 8IG&RE *ESCRI$!I7N $AGE

/ig0 1al!e opening and closing 23

/ig 4 5igh pressure reser!iour 02

/ig 6 +ylinder head 04


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, Introdu"tion

The cam has been an integral part of the %+ engine from itsin!ention. The cam controls the6breathing channels 7 of the %+ engines"that is" the !al!es through &hich the fuel air mi(ture

,in S% engines- or air,in +% engines- is supplied and e(haust dri!en out. Besieged bydemandsfor better fuel economy" more po&er" and less pollution" motor engineersaround the&orld are pursuing a radical 6camless 7 design that promises todeli!er the internal 8combustion engine is biggest efficiency impro!ementin years. The aim of all this effort isliberation from a constraint that hashandcuffed performance since the birth of the internalcombustion enginemore than a century ago. +amless engine technology is soon to be arealityfor commercial !ehicles. %n the camless !al!e train" the !al!emotion is controlled directly bya !al!e actuator 8 there is no camshaft orconnecting mechanisms .Precise electrohydrauliccamless !al!e traincontrols the !al!e operations" opening" closing etc. The seminar looksatthe &orking of the electrohydraulic camless engine" its general featuresand benefits o!er

con!entional engines. The engines po&ering today is!ehicles" &hether they burn gasoline or diesel fuel" rely on a system of!al!es to admit fuel and air to the cylinders and let e(haustgases escapeafter combustion. #otating steel camshafts &ith precisionmachined egg shapedlobes" or cams" are the hardtooled 6brains 7 of the system. Theypush open the !al!es at the

proper time and guide their closure" typicallythrough an arrangement of pushrods" rocker arms" and other hard&are.

Stiff springs return the !al!es to their closed position. %n an o!erhead camshaft engine" achain or belt dri!en by the crankshaft turns one ort&o camshafts located atop the cylinder head.

9 single o!erhead camshaft ,S$5+- design uses one camshaft tomo!e rockers that open bothinlet and e(haust !al!es. The doubleo!erhead camshaft ,D$5+-" or t&incam" setup doesa&ay &ith therockers and de!otes one camshaft to the inlet !al!es and the other to thee(haust!al!es.


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24. )$#:%;< $/ PS5 #$D E;


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.0 Cran%shaft

+rankshaft is the engine component from &hich the po&er is taken. %t recei!es the po&er from the connecting rods in the designated sequence for on&ard transmission to the clutchand subsequently to the &heels. The crankshaft assembly includes the crankshaft and

bearings" the fly&heel" !ibration damper" sprocket or gear to dri!e camshaft and oil seals atthe front and rear.


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.? Camshaft

The camshaft pro!ides a means of actuating the opening and controlling the period beforeclosing" both for the inlet as &ell as the e(haust !al!es" it also pro!ides a dri!e for theignition distributor and the mechanical fuel pump. The camshaft consists of a number of camsat suitable angular positions for operating the !al!es at appro(imate timings relati!e to the

piston mo!ement and in the sequence according to the selected firing order. There are t&olobes on the camshaft for each cylinder of the engine one to operate the intake !al!e and theother to operate the e(haust !al!e.


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.9 >or%ing

$hen the cran! shaft turn the cam shaft the cam lobs come up under the valve

lifter and cause the lifter to move upwards. The upward push is carried by the

pushrods through the roc!er arm. The roc!er arm is pushed by the pushrod% the

other end moves down. This pushes down on the valve system and cause it to

move down thus opening the port. $hen the cam lobe moves out from under the

valve lifter% the valve spring pulls the valve bac! upon its seat. At the same time

system pushes up on the roc!er arm% forcing it to roc! bac!. This pushes the

push rods and the valve lifter down% thus closing the valve. The #gure&'%( shows

cam&valve arrangement in conventional engines

)ingle cam and valve conventional valve train mechanism )ince the timing of the

engine is dependent on the shape of the cam lobes and the rotational velocity of

the camshaft% engineers must ma!e decisions early in the automobiledevelopment process that a*ect the engine is performance. The resulting design

represents a compromise between fuel e+ciency and engine power. )ince

maximum e+ciency and maximum power re,uire uni,ue timing characteristics%

the cam design must compromise between the two extremes.This compromise is

a prime consideration when consumers purchase automobiles. )ome individuals

value power and lean toward the purchase of a high performance sports car or

towing capable truc!s% while others value fuel economy and vehicles that will

provide more miles per gallon.

-ecogniing this compromise% automobile manufacturers have been attempting

to provide vehicles capable of cylinder deactivation% variable valve timing //T"%or variable camshaft timing /0T". These new designs are mostly mechanical in

nature. Although they do provide an increased level of sophistication% most are

still limited to discrete valve timing changes over a limited range.


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.@ An o'er'iew of a "amless engine

To eliminate the cam% camshaft and other connected mechanisms% the 0amless

engine ma!es use of three vital components 1 the sensors% the electronic control

unit and the actuator E2E0T-34I0 034T-32 U4IT 5ainly #ve sensors are used in

connection with the valve operation. 3ne for sensing the speed of the engine%

one for sensing the load on the engine% exhaust gas sensor% valve position sensor

and current sensor. The sensors will send signals to the electronic control unit. The electronic control unit consists of a microprocessor% which is provided with a

software algorithm. The microprocessor issues signals to the solid&state circuitry

based on this algorithm% which in turn controls the actuator% to function

according to the re,uirements.

. Camless 'al'e train

In the past% electro hydraulic camless systems were created primarily as research

tools permitting ,uic! simulation of a wide variety of cam pro#les. 6or example%

systems with precise modulation of a hydraulic actuator position in order to

obtain a desired engine valve lift versus time characteristic% thus simulating the

output of di*erent camshafts. In such systems the issue of energy consumption

is often unimportant. The system described here has been conceived for use in

production engines.

It was% therefore% very important to minimie the hydraulic energy consumption.

In the past% electro hydraulic camless systems were created primarily as research

tools permitting ,uic! simulation of a wide variety of cam pro#les. 6or example%

systems with precise modulation of a hydraulic actuator position in order toobtain a desired engine valve lift versus time characteristic% thus simulating the

output of di*erent camshafts. In such systems the issue of energy consumption

is often unimportant. The system described here has been conceived for use in

production engines. It was% therefore% very important to minimie the hydraulic

energy consumption.

1. Electromechanical Poppet Valves

This type of system uses an armature attached to the valve system.Theoutside

casing contains a magnetic coil of some sort that can be used toeither attract or

repel the armature% hence opening or closing the valve.5ost early systems

employed solenoid and magnetic attraction7repulsionactuating principals using

an iron or ferromagnetic armature. These typesof armatures limited the

performance of the actuator because theyresulted in a variable air gap. As the

air gap becomes larger ie when thedistance between the moving and stationary


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magnets or electromagnetsincreases"% there is a reduction in the force. To

maintain high forces onthe armature as the sie of the air gap increases% a higher

current isemployed in the coils of such devices. This increased current leads

tohigher energy losses in the system% not to mention non&linear behaviourthat

ma!es it di+cult to obtain ade,uate performance. The result of thisis that most

such designs have high seating velocities ie the valves slamopen and shut

hard8" and the system cannot vary the amount of valve lift.Theelectromechanical valve actuators of the latest poppet valve designeliminate the

iron or ferromagnetic armature. Instead it is replaced with acurrent&carrying

armature coil. A magnetic #eld is generated by amagnetic #eld generator and is

directed across the #xed air gap. Anarmature having a current&carrying armature

coil is exposed to themagnetic #eld in the air gap. $hen a current is passed

through thearmature coil and that current is perpendicular to the magnetic #eld%

aforce is exerted on the armature.$hen a current runs through thearmature coil

in either direction and perpendicular to the magnetic #eld%an electromagnetic

vector force% !nown as a 2orent force% is exerted onthe armature coil. The force

generated on the armature coil drives thearmature coil linearly in the air gap in a

direction parallel with the valvestem. 9epending on the direction of the currentsupplied to the armaturecoil% the valve will be driven toward an open or closed

position. Theselatest electromechanical valve actuators develop higher and

better& controlled forces than those designs mentioned previously. These

forcesare constant along the distance of travel of the armature because the

sieof the air gap does not change.

The !ey component of the )iemens&developed in#nitely variable

electromechanical valve train is an armature&position sensor. This sensor ensures

the exact position of the armature is !nown to the E0U at all times and allows

the magnetic coil current to be ad:usted to obtain the desired valve motion.

-eferring now to 6igures ' to ;% an electromechanical valve actuator of thepoppet valve variety is illustrated in con:unction with an inta!e or exhaust valve

((". The valve ((" includes a valve closure member (< having a cylindrical

valve stem =>" and a cylindrical valve head =(" attached to the end of the stem

=>". The valve actuator (>" of thepoppet valve system generally includes a

housing assembly =;" consisting of upper and lower tubular housing members

=?" and ;("% a magnetic #eld generator consisting of upper and lower #eld coils

;


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used and two cable rails connect the actuators to it. A ;(&volt starter&generator

provides the power. (. Electromechanical Call /alves An alternative to the

conventional poppet valve for use in camless valve trains is a ball valve. This

type of electromechanical valve system consists of a ball through which a

passage passes. If the ball is rotated such that the passage lines up with other

openings in the valve assembly% gas can pass through it. Exactly li!e the ball

valves many of us use valve is accomplished by electromagnets positionedaround its exterior. to control our boost. 3pening and closing the -eferring to

6igure '>% the valve housing " is shown in two pieces. Call valve


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engine oil% supplied to theelectro&hydraulic valves by the pressure rail =>". An

engine&driven hydraulic pump =(" supplies the oil pressure% receiving the oil

from the engine oil sump =;". The pump output pressure is also limited by an

unloader valve =?"% as controlled by an accumulator =


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controls the valve closing. The system also includes high and low&pressure chec!

valves.

6igure . ydraulic Pendulum. 9uring the valve opening% the high&pressure

solenoid valve is open% and the net pressure force pushing on the double&acting

piston accelerates the engine valve downward. $hen the solenoid valve closes%

pressure above the piston drops% and the piston decelerates pushing the Duid

from the lower volume bac! into the high&pressure reservoir. 2ow&pressure DuidDowing through the low&pressure chec! valve #lls the volume above the piston

during deceleration. $hen the downward motion of the valve stops% the chec!

valve closes% and the engine valve remains loc!ed in open position. The process

of the valve closing is similar% in principle% to that of the valve opening. The low&

pressure solenoid valve opens% the pressure above the piston drops to the level

in the low pressure reservoir% and the net pressure force acting on the piston

accelerates the engine valve upward. Then the solenoid valve closes% pressure

above the piston rises% and the piston decelerates pushing the Duid from the

volume above it through the high&pressure chec! valve bac! into the high&

pressure reservoir. The hydraulic pendulum is a spring less system. 6igure <

shows idealied graphs of acceleration% velocity and valve lift versus time for the

hydraulic pendulum system. Than!s to the absence of springs% the valve moves

with constant acceleration and deceleration. This permits toperform the re,uired

valve motion withmuch smaller net driving force% than in systems which use

springs.The advantage is further ampli#ed by the fact that in the spring

lesssystem the engine valve is the only moving mechanical mass. Tominimie the

constant driving force in the hydraulic pendulum theopening and closing

accelerations and decelerations must be e,ualsymmetric pendulum".

./ )al'e opening and "losing

A more detailed step&by&step illustration of the valve opening and closing process

is given in 6igure H. It is a six&step diagram% and in each step an analogy to a

mechanical pendulum is shown. In )tep ' the opening high& pressure" solenoid

valve is opened% and the high&pressure Duid enters the volume above the valve

piston. The pressure above and below the piston become e,ual% but% because of

the di*erence in the pressure areas% the constant net hydraulic force is directed

downward. It opens the valve and accelerates it in the direction of opening. The

other solenoid valve and the two chec! valves remain closed. In )tep ( the

opening solenoid valve closes and the pressure above the piston drops% but the

engine valve continues its downward movement due to its momentum. The low&

pressure chec! valve opens and the volume above the piston is #lled with thelow&pressure Duid. The downward motion of the piston pumps the high&pressure

Duid from the volume below the piston bac! into the high& pressure rail. This

recovers some of the energy that was previously spent to accelerate the valve.

The ratio of the high and low&pressures is selected so% that the net pressure force

is directed upward and the valve decelerates until it exhausts its !inetic energy

and its motion stops. At this point% the opening chec! valve closes% and the Duid


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above the piston is trapped. This prevents the return motion of the piston% and

the engine valve remains #xed in its open position trapped by hydraulic

pressures on both sides of the piston. This situation is illustrated in )tep =% which

is the open dwell position. The engine valve remains in the open dwell position

as long as necessary. )tep ; illustrates the beginning of the valve closing.

The closing low&pressure" solenoid valve opens and connects the volume above

the piston with the low&pressure rail. The net pressure force is directed upwardand the engine valve accelerates in the direction of closing% pumping the Duid

from the upper volume bac! into the low& pressure reservoir. The other solenoid

valve and both chec! valves remain closed during acceleration. In )tep @ the

closing solenoid valve closes and the upper volume is disconnected from the low&

pressure rail% but the engine valve continues its upward motion due to its

momentum. -ising pressure in the upper volume opens the high&pressure chec!

valve that connects this volume with the high&pressure reservoir. The upward

motion of the valve piston pumps the Duid from the volume above the piston into

the high&pressure reservoir% while the increasing volume below the piston is #lled

with Duid from the same reservoir. )ince the change of volume below the piston

is only a fraction of that above the piston% the net Dow of the Duid is into the

high&pressure reservoir. Again% as it was the case during the valve opening%

energy recovery ta!es place. Thus% in this system the energy recovery ta!es

place twice each valve event. $hen the valve exhausts its !ineti c energy% its

motion stops% and the chec! valve closes. Ideally% this should always coincide

with the valve seating on its seat. This% however% is di+cult to accomplish. A

more practical solution is to bring the valve to a complete stop a fraction of a

millimeter before it reaches the valve seat and then% brieDy open the closing

solenoid valve again. This again connects the upper volume with the however% is

di+cult to accomplish. A more practical solution is to bring the valve to a

complete stop a frac tion of a millimeter before it reaches the valve seat andthen% brieDy open the closing solenoid valve again. This again connects the

upper volume with the low&pressure reservoir% and the high pressure in the lower

volume brings the valve to its fully closed position. )tep ? illustrates the valve

seating. After that% the closing solenoid valve is deactivated again.

6or the rest of the cycle both solenoid valves and both chec! valves are closed%

the pressure above thevalve piston is e,ual to the pressure i n the low&pressure

reservoir% and the high pressure below the piston !eeps the engine valve #rmly

closed.


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)AL)E 7$ENING AN* CL7SING

,. )al'e motion "ontrol


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/arying the activation timing of both solenoids varies the timing of the engine

valve opening and closing. This% of course% also vanes the valve event duration.

/alve lift can be controlled by varying the duration of the solenoid voltage pulse.

0hanging the high pressure permits control of the valve acceleration% velocity%

and travel time. The valve can be deactivated during engine operation by simplydeactivating the pair of solenoids which control it. 9eactivation can last any

number of cycles and be as short% as one cycle.

Increasing the number of valves in each cylinder does not re,uire a

corresponding increase in the number of solenoid valves. The same pair of

solenoid valves% which controls a single valve% can also control several valves

running in&parallel. Thus% in a four&valve engine a pair of solenoid valves operates

two synchronously running inta!e valves% and another pair runs the two exhaust

valves.

3IG3 $RESS&RE RESER)I7R


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,, &nequal lift modifier

%n a four!al!e engine an actuator set consisting of t&o solenoid !al!es and t&o check !al!escontrols the operation of a pair of intake or a pair of e(haust !al!es. Solenoids and check !al!es are connected to a common control chamber ser!ing both !al!es. %n a fourcylinder engine there are total of eight control chambers connected to eight pairs of !al!es. /or each

pair" the !olumes belo& the hydraulic pistons are connected to the high pressure reser!oir !iaa de!ice called the lift modifier.


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,- C(linder 3ead

C(linder head

Two cross sections of the cylinder head are shown in Figure 12. The aluminium

casting is within the original confines and contains all hydraulic passages

connecting the system components. The high- and low-pressure hydraulicreservoirs are integrated into the casting. The reservoirs and the passages

occupy the upper levels of the cylinder head and are part of the hydraulicsystem. The hydraulic fluid is completely separated from them engine oil system.

A finite element analysis was used to assure the cylinder head integrity for fluid

pressures of up to 9 M a. The lower level of the head contains the enginecoolant.

Figure 12. Cross sections of cylinder head.

The engine valves, the chec valves and the modifiers are completely !uried inthe !ody of the head. The solenoid valves are installed on the top of the cylinder

head and are ept in their proper locations !y a cylinder head cover. "ydraulicand electric connections leading to the hydraulic pump and the electronic

controller, respectively, are at the !ac end of the cylinder head. The height of

the head assem!ly is appro#imately $% mm lower than the height of the !aseengine head. Figure 1& is a photograph of the head on the engine with the head

cover removed. 2'


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06. +omponents of camless engine

0. Engine !al!e 4. Solenoid !al!e 6. =ift modifier >. 5igh Pressure Pump ?. =o& Pressure Pump @. +ooldo&n 9ccumulator


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the )uantity of fluid delivered !y the high pressure pump with the actual needs

of the system at various engine speeds and loads is critical to assuring lowenergy consumption. To conserve the mechanical power needed to drive the

pump, its hydraulic output should closely match the needs. A varia!ledisplacement, high efficiency, a#ial plunger-type pump was initially selected for

that reason. Taing into account the prohi!itively high cost of such pump for

automotive applications, a low-cost varia!le capacity pump was conceived. Across section of the pump is shown in Figure 1'. The pump has a single

eccentric-driven plunger and a single normally-open solenoid valve. uring eachdown stroe of the plunger the solenoid valve is open, and the plunger !arrel is

filled with hydraulic fluid from the low pressure !ranch of the system. uring theupstroe of the plunger, the fluid is pushed !ac into the low pressure !ranch, as

long as the solenoid valve remains open. losing the solenoid valve causes the

plunger to pump the fluid through a chec valve into the high pressure !ranch of the system. arying the duration of the solenoid voltage pulse varies the

)uantity of the high-pressure fluid delivered !y the pump during each revolution.


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,1Low pressure pump

A small electrically driven pump pics up oil from the sump and delivers it to theinlet of the main pump. (nly a small )uantity of oil is re)uired to compensate for

the leaage through the lea-off passage, and to assure an ade)uate inletpressure for the main pump. Any e#cess oil pumped !y the small pump returns

to the sump through a low-pressure regulator. A chec valve 1 assures that theinlet to the main pump is not su!/ected to pressure fluctuations that occur in the

low-pressure reservoir.

,/ Cool down a""umulator


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The system also includes a cooldown accumulator that, during normal operation,

is fully charged with oilunder the same pressure as in the inlet to the mainpump. 0hen the engine stops running, the oil in !oth the high- and the low-

pressure !ranches cools off and shrins. As the system pressure drops, theaccumulator discharges oil into the system, thus compensating for the shrinage

and preventing formation of pocets of oil vapor. The high - pressure !ranch is

fed from the accumulator through a chec valve 2 that is installed in-parallel tothe main pump. The low-pressure !ranch is fed through an orifice that is

installed in-parallel to the chec valve 1. The orifice is small enough to preventpressure wave propagation through it during each engine cycle, !ut sufficient to

permit slow flow of oil from the accumulator to the reservoir. n someapplications, the orifice can !e incorporated directly in the chec valve. After the

oil in the system has cooled off, the accumulator maintains the system at a!ove

atmospheric pressure !y continuously replenishing the oil that slowly leas outthrough the lea-off passage. 0hen the engine is restarted, the accumulator is

recharged again. f the engine is not restarted for a very long time, as it is thecase when a vehicle is left in a long-term paring, the accumulator will

eventually !ecome fully discharged. n that case, the pressure in theaccumulator drops to an unaccepta!le level, and a pressure sensor, that

monitors the accumulator pressure, sends a signal to the engine control system

which reactivates the electric pump for a short period of time to recharge theaccumulator. This process can !e repeated many times, thus maintaining the

system under a low level of pressure until the engine is restarted. After theengine restarts it taes less than one revolution of the main pump to restore the

high pressure. (perating the hydraulic system in a closed loop contri!utes to lowenergy consumption. The amount of hydraulic power consumed !y the system is

determined !y the flow of fluid from the high- to the low-pressure reservoir

times the pressure differential !etween the outlet from and the inlet to the highpressure pump. A small loss is also associated with leaage. There are good

reasons to use high hydraulic pressure in the system, one of them !eing theneed to maintain a high value of the !ul modulus of the oil. n a closed-loop

system the pressure in the low-pressure reservoir can also !e )uite high,although lower than in the high-pressure reservoir thus the pressure in the low-

pressure rail is low only in relative terms3. "ence, the system can operate with

very high hydraulic pressure, and yet the energy consumption remains modestdue to a relatively low pressure differential. The ratio of high pressure to low

pressure must !e sufficiently higher than the ratios of the pressure areas a!oveand !elow the valve piston to assure relia!le engine valve closure.

-.Ad'antages of "amless engine

4lectrohydraulic camless valve train offers a continuously varia!le and

independent control of all aspects of valve motion. This is a significant


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advancement over the conventional mechanical valve train. t !rings a!out a

system that allows independent scheduling of valve lift, valve open duration, and

placement of the event in the engine cycle, thus creating an engine with a totally

uncompromised operation. Additionally, the 4 system is capa!le of controlling

the valve velocity, perform selective valve deactivation, and vary the activation

fre)uency. t also offers advantages in pacaging. Freedom to optimi*e all

parameters of valve motion for each engine operating condition without

compromise is e#pected to result in !etter fuel economy, higher tor)ue and

power, improved idle sta!ility, lower e#haust emissions and a num!er of other

!enefits and possi!ilities. amless engines have a num!er of advantages over

conventional engines. n a conventional engine, the camshaft controls intae and

e#haust valves. alve timing, valve lift, and event duration are all fi#ed values

specific to the camshaft design. The cams always open and close the valves atthe same precise moment in each cylinder s constantly repeated cycle of fuel-air

intae, compression, com!ustion, and e#haust. They do so regardless of whetherthe engine is idling or spinning at ma#imum rpm. As a result, engine designers

can achieve optimum performance at only one speed. Thus,the camshaft limitsengine performance in that timing, lift, and duration cannot !e varied. Theimprovement in the speed of operation valve actuation and control system can

!e readily appreciated with reference to Figure 12. t shows a comparison!etween valve speeds of a mechanical camshaft engine and the camless engine

valve actuation. The length of the valve stroe in inches versus degrees of rotation of a mechanical camshaft is illustrated. 0hen graphed, the cycle of

opening and closing of a valve driven !y a mechanical camshaft will display a

shape similar to a sine curve. The opening period as measured in cranshaftdegrees3 remains constant for any engine load or rpm. "owever, the cycle of

opening and closing of valves driven !y the electromechanical valve actuators

operates much faster. esigned to match valve-opening rates at the ma#imumengine rpm, the electromechanical valve actuators open the valve at this samerate regardless of engine operating conditions. +ecause of this improved speed,

greater fle#i!ility in programming valve events is possi!le, allowing for improved

low-end tor)ue, lower emissions and improved fuel economy. The massiveopening period for the electromechanically driven valve can also !e seen +ut in a

cam less engine, any engine valve can !e opened at any time to any lift positionand held for any duration, optimi*ing engine performance. The valve timing and

lift is controlled 1%% percent !y a microprocessor, which means lift and durationcan !e changed almost infinitely to suit changing loads and driving %conditions.

The promise is less pollution, !etter fuel economy and performance. Another

potential !enefit is the cam less engine5s fuel savings.m ompared toconventional ones, the cam less design can provide a fuel economy of almost '-

1%6 !y proper and efficient controlling of the valve lifting and valve timing. Theimplementation of camless design will result in considera!le reduction in the

engine si*e and weight. This is achieved !y the elimination of conventionalcamshafts, cams and other mechanical linages. The elimination of the

conventional camshafts, cams and other mechanical linages in the camless

design will result in increased power output. The !etter !reathing that a camlessvalve train promotes at low engine speeds can yield 1%6 to 1$6 more tor)ue.

amless engines can slash nitrogen o#ide, or (#, pollution !y a!out &%6 !ytrapping some of the e#haust gases in the cylinders !efore they can escape.

7u!stantially reduced e#haust gas " emissi ons during cold start and warm -upoperation.


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, Con"lusion

1. An electro hydraulic camless valve train was developed for a camless engine.

nitial development confirmed its functional a!ility to control the valve timing,

lift, velocity, and event duration, as well as to perform selectively varia!ledeactivation in a four -valve multicylinder engine.

2. The system employs the hydraulic pendulum principle, which contri!utes tolow hydraulic energy consumption.

&. The electro hydraulic valve train is integral with the cylinder head, whichlowers the head height and improves the engine pacaging.

8. eview of the !enefits e#pected from a camless engine points to su!stantialimprovements in performance, fuel economy, and emissions over and a!ove

what is achieva!le in engines with camshaft!ased valve trains.

$. The development of a camless engine with an electro hydraulic valvetraindescri!ed in this report is only a first step towards a complete engine

optimi*ation. Further research and development are needed to tae fulladvantage of this system e#ceptional fle#i!ility.


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-- Bibliograph(

m&&&.machinedesign.com&&&.halfbakery.com&&&.deiselnet.com

www.greendieseltechnology.co&&&.me.sc.edu

Camless Engine Report

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