The present invention refers to an electromechanical actuator for machine valves and to an electronic control system equipped with such actuator.

The increasing use of drives of mechanical members through the control electronics in the automotive (mechatronic) field implies an increase of the confidence and of the chance of controlling some statuses which so far could appear mechanically "constrained" (or subordinate to others) .

The most widespreaded operating fluid system is the internal combustion engine (MCI), and it is defined as thermal driving machine which allows converting the chemical energy, owned by an air- fuel mixture, into a mechanical work available onto the shaft. The conversion occurs in the combustion chamber, where burnt gases push the piston downwards, while this latter one, in turn, rotates the drive shaft. The mixture consists in a fuel which can be gasoline, diesel oil, GPL or other petrol derivatives (or other mixtures such as alcohol or colza or others), while air oxygen operates as comburent. The type of fuel determines the engine characteristics and therefore its application in the various fields.

The class of internal combustion engines comprises a wide variety of different types.

In particular:

volumetric engines, wherein engine fluid is periodically processed inside a well defined volume and cyclically generated by the motion of some mechanical members

reciprocal movement engines, wherein the reciprocal movement of the pistons is transformed into a rotary movement through a rotary through crank gear

- rotary movement engines, where the piston or rotor has not a reciprocal movement, but a more or less constant rotary movement, acording to the type of engine

continuous engines, wherein driving fluid is processed continuously in a particular area of the engine with non-variable volume: this latter type of engine is therefore like a mechanical energetic outflow system.

Reciprocating engines are divided, depending on the thermo-dynamic cycle type, into:

- engine with controlled switching-on, improperly defined as "explosion engine" (Otto cycle)

engine with spontaneous switching-on (Diesel cycle) ,

or depending on how the cycle on the reciprocating motion is fractioned:

- two-stroke engine

- hybrid two/four-stroke engine

- four-stroke engine.

The four-stroke reciprocating volumetric engine is the type of engine which provides mechanical energy to almost all rubber-type transport means, to motor boats (excluding ships which use the supercharged two-stroke engine) and some trains. It is also used on small propeller- type airplanes and to produce low-voltage electric energy.

The volumetric engine, in order to operate, needs several members: the proposed system intervenes on distribution mmebers, which are those allowing to move the valves.

The invention in fact deals with an innovative system, applied to operating fluid machines, for controlling the movements of valves and for inlet and discharge in and from the combustion chamber, applied to one or more cylinders.

Currently, the opening and closing control of the valves of a machine with operating fluid, such as an internal combustion engine, is provided by the camshaft stiffly connected to the drive shaft: transforming rotary movement into axial movement determines its Lift/Rest/Closing stroke in a timed but fixed way, depending on engine revolutions.

Currently, systems are being introduced on the market which are capable of optimizing part of the operating cycle. These very complex and costly systems, however, do not allow a modular check of single valves such as to optimize engine performances.

For example, if the valves were directly controlled, always depending on engine pulses, but not stiffly interconnected, modularity could then be obtained. This direct control would allow a quicker, safe, reliable, flexible and non-hysteresis control of actuating times (Lift/Rest/Closure) , optimizing engine performances.

As regards the main characteristics of valve controlling systems for internal combustion engines, an important aspect of the actual suction and exhaust operation, present in every engine, is managing valve spark advances. It is easy to imagine how any action does not perfectly istantaneously occur, but that instead a certain time, even short but not null, is required.

Actually, valve movements occur in a time which is comparable with about one operating phace, namely (referred to a four-stroke internal combustion engine) in a quarter of a cycle.

Therefore, if opening of suction valves starts at the Top Dead Center, and a closure is imposed at the Bottom Dead Center, the valve will not be perfectly open during this phase, but, at the beginning, it will only partially be open: therefore, it will be completely open only around half of the phase and will already be again partially closed at the end of the phase. This complicates a lot the gas flow in suction and exhaust ducts, because, as stated, during the phase the valve will stay more time in its partially open/closed position than in its open position. In order to compensate for this problem, it is necessary to advance the time in which valves open, and delay the time in which they close - with respect to the ideal time - so that, upon reaching it, the valve is open or close enough to "well perform its tasks".

The above opening advance/closing delay however means that, for example in the first part of the compression, the suction valve is still open (with the risk that part of the fuel-comburent mixture is pushed outside instead of being compressed) or that, in the last expansion phase before explosion, part of the thrust gets lost (due to burnt gases which go out of the exhaust valve which is opening) .

Object of the present invention is solving the above prior art problems, by providing an electromechanical actuator which, being externally controlled, allows more actuation and control flexibility for the valve stroke movements (Lift/Rest/Closure) in a direct way, without the help of systems which are stiffly connected to the engine (such as camshaft, pulleys, belts, etc.).

Another object of the present invention is providing an electronic control system equipped with the above described actuator.

The above and other objects and advantages of the invention, as will appear from the following description, are obtained by an electro-mechanical actuator for machine valves and an electronic control system equipped with such actuator as claimed in the respective independent claims. Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims .

It is intended that all enclosed claims are an integral part of the present description.

The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which:

- Figure 1 is a functional block diagram of a system which uses an actuator according to the present invention;

- Figure 2 is a side sectional view of a first preferred embodiment of the actuator of the present invention;

- Figure 3 is a side sectional view of a second preferred embodiment of the actuator of the present invention; and

- Figure 4 is a side sectional view of a comparison between a prior art actuator and an actuator of the present invention.

With reference to the Figures, a preferred embodiment of the electro-mechanical actuator for machine valves and of the electronic control system equipped with such actuator of the present invention are shown and described. It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionalities) could be made to what is described, without departing from the scope of the invention as appears from the enclosed claims.

With reference initially to Figure 1, it shows a functional diagram of the electro-mechanical system EVA to which the present invention is applied.

In Figure 1, reference numbers designate: 1 a control drive of the propulsors, 2 a data processing unit (ECU) , 3 a plurality of auxiliary propulsors, 4 a corresponding plurality of actuators, 5 a continuous detector of the position of the drive shaft, and 6 a corresponding plurality of valves, coupled and operatively connected to the actuators 4 controlled by the propulsors 3.

Handling and stroke of valves 6 (as shown in Figure 1) are performed by an actuator 4 which in turn is externally controlled and driven, but not mechanically constrained, by the drive shaft (not shown) .

Therefore, control and handling of the valve 6 are obtained by transforming the rotary movement (provided by an auxiliary propulsor 3) into a translating movement of the valves through a precision, coaxial joining system composed of a mobile coupling between the valve 6 itself and any mechanical device (which will be shown below) adapted to perform an axial displacement (such parts are the actuator 4) .

The auxiliary propulsor 3, placed in control of any mechanical device adapted to perform an axial movement, with its own position sensor, allows such performances as to obtain a response time with immediate control, without hysteresis and with reduced strokes (due to the provided accuracy) . It is electronically driven by a drive 1 which, in real time, transmits the necessary current for its handling.

A data processing unit (or ECU) 2, depending both on signals received by the continous detector 5 of the position of the drive shaft, and on data supplied by the various sensors and on engine conditions (load), sends a command to the drive 1 for suitably managing the single propulsors 3.

Every command processed by the ECU 2 is defined by a dedicated software, optimized depending on the actual needs expressed by operating and environemtal conditions of the engine, in addition to different regulating conditions of the valves 6 (stroke, operating powers, times and phasing, etc.).

Figure 2 shows a first preferred, but absolutely not limiting, embodiment of the electromechanical actuator 4 of the present invention and of its related mechanical components.

Figure 2 shows an electro-mechanical actuator 4, with fixed coupling element, for controlling movements of the valve 6.

It is composed of any device 10 adapted to switch the rotary movement of the propulsor 3 into a translating movement of the valve 6, keyed-in directly (or by means of a joint) onto the shaft 14 of the auxiliary propulsor 3, completed with position detector which transmits the rotary movement .

The actuator further comprises a coupling element 7 of any device 10 switching the rotary movement into translating movement, which is constrained by rotation-preventing sliders and/or bearings 8, which therefore allow only its translating movement.

In its lower part, the locking ring nut 11, with its related NP half-cones 12, blocks the valve NP 6.

The actuator 4 is fastened to the engine overhead through a blocking system 9.

Summarising, Figure 2 shows an actuator 4 with fixed coupling element (for example a ball- recirculation nut screw) , comprising an auxiliary propulsor 3, a valve NP 6, a coupling element 7 of any mechanical device switching the rotary movement into translating movement (for example a ball- recirculation nut screw) , sliders/bearings 8 for preventing the rotation of the nut screw 7, a blocking system 9, a mechanical device 10 switching the rotary movement into translating movement (for example a ball-recirculation nut) , a ring nut 11 for blocking the valve 6, NP half-cones 12 and a shaft 14 of the propulsor 3. Reference number 13 then designates the maximum stroke, which can be optimized, of the inventive actuator 4.

Figure 3, instead, shows another preferred embodiment of the inventive electro-mechanical actuator 4.

The shaft 14 of the propulsor 3, completed with position detector, is stiffly keyed-in to a coupling element (for example a rotary ball- recirculation nut screw) 7 of any mechanical device (for example a ball-recirculation nut) 10 switching the translating movement into rotary movement. The propulsor 3 is fastened through a blocking system 9. The coupling element 7 is further constrained to the valve over-head 16 by thrust bearings 17, through the locking ring nut 15, in which such thrust bearings 17 allow only its rotation. In this case, the mechanical device 10 switching the rotary movement into translating movement is directly obtained onto the stem of the valve 6.

The rotation-preventing bearings 18, which allow only translating movements, are fastenend onto the stem of the valve 6, and are opposed by the rotation preventing sliders/contrast bearings 19.

Figure 3 also shows, with reference number 13, the maximum stroke, which can be optimized, obtained by the inventive actuator 4.

Figure 4 finally shows a comparison between a traditional mechanical control S2 and the electromechanical arrangement SI proposed for operating/handling the valves 6 in an engine with operating fluid, such as an internal combustion engine, keeping part of the NP components.

The electro-mechanical system S2 EVA of the invention includes:

- an auxiliary propulsor 3 with dedicated performances for controlling the actuator 4

- a mechanical actuator 4 equipped with any mechanical device switching the rotary movement into translating movement and fixed or rotary coupling element

- cylinder valves 6

- a control unit ECU 2

- a sensor 5 for the continuous detection of the position of the drive shaft The control system, for a suitable handling of the single propulsors 3 connected through the actuators 4 to the valves 6, provides for a continuous detector 5 of the position of the drive shaft, which sends a signal to the ECU 2, which (depending on the conditions of the sensors and the conditions of the engine or load) respectively allows :

- managing responce times;

- opening the valves;

- managing the stroke;

- managing advances/delays;

- managing the (opening and closing) length;

- managing the (opening and closing) stay.

As shown in Figure 4, the arrangement allows a reduction of mechanical moving parts (the replacement of the camshaft and of the related mechanical connections is pointed out) , due to the adoption of a system equipped with any mechanical device switching the rotary movement into translating movement and fixed or rotary coupling element .

The actuator system composed of any mechanical device 4 switching the rotary movement into translating movement, set in an axial-rotary movement, by coupling to the auxiliary propulsor 3 (with its own position sensor) , allows obtaining high performances.

Through a better accuracy, though keeping part of the NP components (valve 6 and fastening half- cones 12 in case of a fixed coupling element, for example) it is possible to remove the hysteresis and optimize the stroke 13, to thereby allow a response time with immediate control.

The engine working conditions (cycle phases) are sent to the ECU 2 through a continuous positioning sensor 5, coupled with the usual parameter-detecting sensors.

The ECU 2, managed by a software, therefore transmits a control/drive signal, which determines and communicates in real time the necessary control signal for Lift/Rest/Closure movements of the valve 6 through the auxiliary propulsor 3.

The presented system allows:

a increasing the valve stroke performances b optimizing the combustion

c obtaining a better system modularity

d simplifying the engine architecture

e increasing the system reliability

f optimizing consumptions and NVH g- reducing design and operating costs

As regards the analysis of the advantages of the application, in its various aspects, the following are obtained:

A) VALVE STROKE

- better Lift/Rest/Closure control

- check of real stroke need / position

- reduction of valve stem (length)

- self-regulation/compensation for thermal dilatations and wear (elongation of mechanical components)

B) COMBUSTION OPTIMIZATION

- through an immediate opening and closing of the valves depending on the required engine instant (real stroke)

chance of keeping the valves at a fixed point (constrained by engine rotation) , to improve the efficiency in the combustion chamber: continuous stroke modulation versus valve lift depending on actual engine load

- chance of changing the compression ratio

- chance of switching on with open valves: reduction of the power absorbed by the starter due to the absence of the compression effect in the first starting cycle

reduction and optimization of emission and combustion (reduction of consumes)

C) SYSTEM MODULARITY

separate management for every single cylinder

- chance of driving the cylinders during both active and passive phases (engine brake efficiency adapted to be modulated)

- flexibility of use of different fuels and working/operating cycles

- better self-adaptation to environmental and operating conditions

D) ENGINE ARCHITECTURE SIMPLIFICATION

- design simplification and reduction of the number of components: absence of camshaft and of the whole rotation kinematic chain

- removal of recall springs for compensating hysteresis, small glasses and plates, rods E) RELIABILITY

- optimization of engine balancing

- reduction of moving members and of their stress reduction of frictions for a lower absorbed power and therefore less wear

reduction of the circulating lubricant amount less maintenance and regulation

electronic management of working phases

FUEL AND NVH CONSUMPTION

reduction of consumptions and emissions combustion optimization due to a more accurate and quicker handling of the valves

friction reduction due to the reduction of moving members

better efficiency during the start-up phase (more quickness upon starting)

noise reduction

reduction of absorbed power for controlling the auxiliary members

REDUCTION OF COSTS

removal of camshafts and of their related mechanical workings for housing them

removal of components for moving the valves (springs, rods, small glasses, etc.)

possible reduction of cylinder head height reduction of valve stem length

reduction of weights and moving members reduction of lubrifying oil amount

lower component wear

reduction of working, component, building, assembling, regulation and calibration (end of line) costs