WO2011048540A1

WO2011048540A1 - Valve for egr low-pressure applications in internal combustion engines

Info

Publication number: WO2011048540A1
Application number: PCT/IB2010/054712
Authority: WO
Inventors: Pierluigi Dell'orto; Mario Marchetti; Francesco Godono; Salvatore Iovino; Felice Liccardo; Francesco Vitale; Claudio Rivieccio
Original assignee: Dell'orto S.P.A.
Priority date: 2009-10-19
Filing date: 2010-10-18
Publication date: 2011-04-28
Also published as: IT1396027B1; ITMI20091799A1

Abstract

The present invention concerns a valve assembly for low- pressure applications of the controlled recirculation of the exhaust gases of an internal combustion engine (MCI), the body whereof (1) comprises a flow conduit (Ia) with at least one entry section and one exit section, as well as at least one moving element (5) with valve function, cooperating with a valve seat (6) and consisting of the coupling of one bearing element and of one sealing element. The valve body comprises a main conduit (Ia), with a first outflow section (2) and a second outflow section (3) at the two ends, and a secondary conduit (1b), which has a third outflow section (4), at one of the ends thereof, and which, at the other end, connects to said main conduit through an interface section (9a). Said moving element (5) is a sealing element of the valve seat and, at the same time, a partialisation means of the flow rate of the flows in said main and secondary conduits; for this reason it is capable of moving, in its path between the closing position on said valve seat (6) and its fully-open position, on a first portion exclusively within the secondary conduit (1b), namely between the closing position on said valve seat (6) and said interface section (9), and subsequently, on a second portion, through the port of said primary conduit (Ia). Said moving element is in the form of a vane and disc, where the vane-shaped element takes on the flow-adjusting function and the disc- shaped element takes on the valve seat sealing function. The invention furthermore concerns a recirculation system of the exhaust gases in an internal combustion engine, wherein said valve assembly can be inserted on the (MCI) engine, intake side or discharge side.

Description

VALVE FOR EGR LOW-PRESSURE APPLICATIONS IN INTERNAL COMBUSTION ENGINES

O*O*0*O*O

FIELD OF THE INVENTION

The invention concerns a system which allows to implement the controlled recirculation of exhaust gases (EGR) in a Diesel, supercharged, internal combustion engine provided with systems which process exhaust gases (as in the case of catalysts and Diesel particulate filters, or DPF) in order to clean them be- fore releasing them into the atmosphere.

More precisely, the technical field of the invention is that of exhaust gas low-pressure recirculation systems, referred to in the following by the expression EGR (acronym of "Exhaust Gas Recycling", i.e. "Recirculation of exhaust gases") Long Route.

The recirculation of burnt gases is a highly effective method for lowering combustion temperature and for the resulting reduction of nitrogen oxides. As a matter of fact, it allows to dilute the charge of intake air with the previously produced exhaust gases, which do not take part in the combustion reaction, i.e. which take part therein only for the share of gases defined as "unburnt" . The use of EGR gases is particularly useful at medium-low rpms, while it is instead counterproductive in all those situations in which greater power is called for; in this case the EGR flow must be interrupted, and it is paramount that the relevant control valve has an excellent seal, with virtually inexistent seepage.

The advantages of EGR Long Route systems are varied:

a) they facilitate nitrogen oxide reduction,- b) recirculated gases are nearly free from carbon par- tides since they have been taken downstream of the

DPF;

c) recirculated gases have a lower temperature than those exiting from the combustion chamber;

d) fresh charge dilution;

e) system easily applicable to the engine configuration; Against such advantages the application of the controlled recirculation technique of burnt gases by means of Long-Route- type systems is remarkably difficult. In such respect it is pointed out that the path of exhaust gases runs between low- pressure points, and that requires the circuit to be characterised by high gas flow permeability. In this respect conventional mushroom valves have evident applicability limits. As a matter of fact, although such valves guarantee high resistance to seepage, on the other hand they are little efficient in terms of maximum processed flow rate and this applies both due to the limited value of the outflow coefficient, and due to the limits imposed by the maximum lift of the valve.

For Low-Pressure type EGR applications, i.e. of low-pressure exhaust gas recirculation, systems are therefore necessary which allow to process high gas flow rates and which, at the same time, guarantee a high resistance to exhaust gas seepage. The performances of EGR systems of the Long Route type can be remarkably increased if it is possible to influence the fluid dynamics of intake and/or discharge systems in the most suitable way which is functional to the aims.

The present invention proposes innovations concerning a) the system for implementing the controlled low-pressure recirculation of exhaust gases, and b) the way to optimise system performances by influencing the fluid dynamics of intake and/or discharge systems .

STATE OF THE PRIOR ART

EGR valves which allow to implement the technique of the controlled recirculation of exhaust gases are already known.

Document US-7,267,139 illustrates a Long Route EGR valve wherein two throttle-type adjusting elements are found. In particular a first element, referred to in the following as throttle 7a (see numbers in fig. 1 of the cited document) , controls the EGR gas flow, while a second element - referred to in the following as throttle 7b - controls the intake air flow to the engine. When small EGR flow rates are required, only throttle 7a intervenes in the adjustment, while throttle 7b is kept in the fully-open configuration. Greater EGR flow rates are obtained by suitably closing throttle 7b and leaving throttle 7a fully open. This creates a greater depression downstream of throttle 7a, capable of drawing through said throttle larger gas flow rates, in proportion to the created depression. Hence the combination of the closure of throttle element 7b (which causes a variation of the depression in the intake collector) and of the opening of throttle element 7a allows to have varying EGR flow rates and to control also very small flow rates . The throttle valves are actuated by a single actuation system with an electrical control . The system is designed so that at least one of the two throttles is always open and through the electric motor it is possible to adjust the two valves one at a time.

This solution evidently has the disadvantage of being exces- sively bulky and costly; moreover, if on the one hand throttle valves offer good permeability, on the other hand they do not allow to obtain good performances in terms of resistance to gas seepage in the working conditions in which - as mentioned above - it is not intended to actuate the EGR recirculation.

In the document US-6,880,572 a much more compact EGR valve is proposed which offers to the burnt gas flow a single entry section and a single exit section. Such valve comprises a valve- body wherein a single moving element referred to as 16 (in the numbering of fig. 1 of the cited document) is arranged, which is connected to the shaft 18 of an actuation system. The exhaust gas flow rate enters the valve body through the entry section, referred to as 12, passes through the internal conduit of the valve-body, and exits through the exit section referred to as 14.

During the closing manoeuvre the shaft of the actuation system is rotated so as to accomplish the coupling between the sealing surface found on moving element 16 - which has an L- shaped configuration - and the seat surface arranged in correspondence of exit section 14. When the valve is in the closing position, the moving element closes the flow passage through the exit port. VMCI versa, during the opening manoeuvre the shaft of the actuation system is rotated in an anti-clockwise direction (with respect to the drawing of fig. 1 of the cited document) causing the opening of the valve. In a fully open position the moving element of the valve allows the flow of the exhaust gases through the conduit formed in the valve body and then through the exit section. In this configuration the moving element moves as far away as possible from the conduit, within the limits of the field of movement provided, causing the minimum bulk of the outflow area and maximising valve permeability and hence the flow rate.

VMCI versa, when the actuator shaft is rotated so as to fully close the valve exit section, the sealing surface of the moving element is coupled with the seat surface,- thereby good resistance to gas seepage is accomplished, also due to the force exerted by the flow against the surface of the moving element facing the conduit.

As far as the operating conditions are concerned, it is pointed out that the EGR valve according to US-6,880,572 is provided with a safety actuation in case of failure of the actua- tion device. As a matter of fact, in case of malfunctioning of the actuation system, the valve remains closed, because the moving element is pushed by the fluid so as to take up the configuration corresponding to full valve closure. This occurs even if the malfunctioning occurs when the valve is fully open, since the fluid imparts a thrust against the moving element, so much so as to cause the rotation thereof and to bring the valve back into a closed condition. The described solution has evident limitations in terms of the reliability of the safety actuation, since it is substantially operated by the sole thrust of the fluid.

A further different arrangement is discussed in the document US-2008/0029073 , wherein an EGR valve is proposed which - as in the case just described - offers an entry section and an exit section to the burnt gas flow. Such valve comprises a valve- body, wherein a single moving element 20 is arranged (in the numbering of fig. 1 of the cited document) , which is connected to the shaft 18 of an actuation system. The actuation system is based on the use of an electric-type device, and furthermore provides the use of a gear transmission. Even according to such solution, the flow rate of EGR gases enters the valve body through an entry section, flows through the internal conduit of the valve body and flows out through an exit section. Moreover, the valve configuration provides the use of a torsional spring capable of imparting a suitable torque during valve actuation dynamics .

In the fully open configuration the moving element of the valve has a minimal influence on the flow rate of EGR gases; this is due to the fact that, in correspondence of the fully open valve configuration, it is within a compartment arranged in the valve body. Thereby the EGR valve is characterised by high permeability to the flow of EGR gases.

The valve is furthermore characterised by good resistance to gas seepage due to the presence of a flexible, and at the same time resilient, connection, between the moving element and the disc arranged thereon. Such connection causes the disc to move - in the final part of the closing manoeuvre - along a direction which is virtually parallel to that of the EGR flow, with a re^¬ sulting accurate positioning of the disc on the respective seat thereof .

Yet another known arrangement is illustrated in US- 2003/084887; the valve structure is that of a three- ( fluid) "way" valve, with one "way" dedicated to the incoming EGR flow, one "way" dedicated to the entry of intake air, and one "way" intended for the exit of intake air, mixed - when provided - with the incoming flow of EGR gases. More precisely, the three-way EGR valve consists of a rectilinear main conduit, at the ends of which a first outflow section and a second outflow section are formed, as well as a secondary conduit, which connects to said main conduit through one end and the other end of which secondary conduit has a third outflow section. In the point of con- nection between secondary conduit and main conduit a rotating (on a shaft having an axis transversal to the longitudinal axis of the main conduit) closing element of the secondary conduit is provided.

The functions of the valve are those of allowing the entry of an adjusted EGR flow rate and of obtaining the mixing of such flow rate with the flow rate of incoming intake air in the main conduit, in the measure set out by the angular position of a moving member. The structure of such moving member is a vane- and-disc structure; the disc cooperates with a closing seat arranged at the interface between the two conduits and guarantees the resistance to seepage through a closed valve, while the vane is capable of partialising the flow rate of the air circulating in the main conduit through an open valve. In particular, the ability of adjusting the EGR flow rate and hence the EGR percentage which the valve makes available for mixing with air, varies depending on the opening angle of the moving member with respect to the relative rotation axis.

In consideration of this just described general valve structure of it, the valve according to US-2003 /084887 is here considered as the closest prior art of the present invention. It must be added that, as far as the specific structure of the vane-and-disc moving member is concerned, a general shape of this type is also known from US-4171689.

However, this prior art is not free from drawbacks: on the one hand, the adjustment of the EGR mixing percentage in the in- take air is not as accurate as it is desirable; this depends on the arrangement of the moving vane-and-disc member which, as soon as it opens, in order to let a desired amount of EGR enter the main conduit, however, interferes directly with the flow of intake air. On the other hand, the structure of the moving vane- and-disc member, according to US-4 , 171 , 689 , has greater construction complexity.

PROBLEM AND SOLUTION

The present invention sets itself the aims of guaranteeing remarkably better performances in terms of: processing of high gas flow rates, when the valve is led to take up the open con^¬ figuration; accurate adjustment of the flow rate of recircula- tion gases, even without direct interference of the moving member with the intake air flow; perfect sealing, i.e. resistance to gas seepage, when the valve is led to take up the closed configuration. Unlike US-2003/084887 , the structure according to the invention has a moving member which acts as sealing and adjusting element, capable of operating a first partialisation of the flow rate flowing through the secondary conduit and then, by increasing the opening angle, of operating the partialisation of the flow rate flowing through the main conduit; by operating in this way better flow rate adjustment can be obtained".

In particular, a first problem consists in providing an EGR valve for low-pressure applications of the controlled recirculation technique of exhaust gases, which has the functional features of high permeability to the flow of recirculation gases, high resistance to seepage, accurate adjustment of the EGR flow rate and, moreover, of allowing the partialisation of intake air to the engine, grouped in a single construction unit.

A second problem consists in providing a system which in addition to the above-mentioned functional features of high perme- ability, high resistance to seepage, accurate adjustment of the EGR flow rate, allows the partialisation of the flow rate of outgoing gases from the engine exhaust system without necessarily implying burdensome complications of the construction solution of the system, such features being again grouped in a sin- gle construction unit.

However, since the configuration of the moving element of the EGR valve according to document US-2003/084887 is not such as to allow an accurate resolution of the adjustment of the EGR flow rate, it is a further object of the present invention to propose a device which - in addition to having the cited features of high permeability, of high resistance to seepage, of allowing the motion field partialisation on the intake or discharge side - allows more specifically an accurate adjustment of the EGR flow rate through simpler and better controllable means, and using a single actuator.

In particular a further problem consists in providing a sys- tern wherein the above-mentioned operating functions are achieved by introducing in the EGR valve design a single moving element actuated by a single actuator; such moving element, therefore, performing both tasks: that of adjusting element and that of sealing element.

These objects are achieved through the features mentioned in independent claims 1 and 16. Dependent claims describe preferred features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The main technical, construction and functional features of the present invention and the advantages deriving therefrom are in any case more evident from the following description of the preferred embodiments of the invention; given purely as a non- limiting example and illustrated in the attached drawings, wherein:

Fig. 1 is an isometric view of the EGR valve according to a preferred embodiment as "three-way" valve;

Fig. 2a is a cross-section view of the same EGR valve of fig. 1, with the moving element in an intermediate operating po- sition; this drawing also shows the flow directions when the valve is arranged on the intake side;

Fig. 2b is a cross-section view fully identical to that of fig. 2a, except for the fact that said moving element is in a fully-closed position;

Fig. 2c is a cross-section view fully identical to that of fig. 2a, except for the fact that said moving element is in a fully-open position, until flow partialisation in the main conduit of the valve body; this drawing also shows the flow directions when the valve operates the flow rate partialisation of the intake air;

Fig. 2d is a cross-section fully identical to that of fig. 2c, except for the fact that said valve is arranged on the discharge side; this drawing also shows the flows when the valve operates the flow rate partialisation of the exhaust gases;

Fig. 3 is a cross-section view of the moving element of the

EGR valve; Fig. 4 is a perspective view of the same moving element of the EGR valve;

Fig. 5 is an application diagram of the EGR valve in an internal combustion engine, in an arrangement which provides the flow partialisation of the intake air;

Fig. 6 is an application diagram of the EGR valve in an internal combustion engine, in an arrangement which provides the flow rate partialisation of the exhaust gases; and

Fig. 7 is a diagram showing the linear trend of the ratio between percentage flow rate of EGR (in ordinates) and moving angle of the valve moving member (in abscissae) .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown firstly in drawings 2a, 2b, 2c and 5, the Long Route EGR valve proposed by the present invention is described as a valve inserted on the intake of the MCI internal combustion engine. It is a three-way valve, in the body 1 of which there are formed: on one side, a conduit la, in the following conventionally called main conduit la, at the ends of which there are two outflow sections, i.e. an outflow section 2, which acts as entry section of the fresh intake air charge to the engine, and an outflow section 3, which acts as exit section of the mix of air and cooled EGR gases; on the other side, a conduit lb - in the following conventionally referred to as secondary conduit lb - which with one end thereof connects with main conduit la and at the other end thereof ends in an outflow section 4, which acts as entry section of the cooled EGR gas .

More precisely, conduit la is formed in a first part of body 1, having tubular geometry, while conduit lb is formed in a second part of body 1, which ends with an outflow section 4, in the terminal area 4a, wherein a ring 6 forming a valve seat is also arranged .

In the area connecting the first to the second part of body 1 there is formed an interface area 9, with a corresponding outflow section 9a. In this outflow section 9a, between main con- duit la and secondary conduit lb, there is arranged a moving valve element 5, preferably constrained to the second part of body 1; the configuration and arrangement of this element 5 are better described in the following.

In the embodiment illustrated in the drawings, said secondary conduit connects with said main conduit preferably - even though not necessarily - at an acute angle. The constraint axis of said moving element 5 is then positioned within said acute angle .

According to a first important feature of the invention, the constraint axis of said moving element 5 is arranged in corre- spondence of said acute angle and within said secondary conduit lb.

According to a further important feature, also the valve seat whereon the closing of the secondary conduit is produced is arranged within said conduit lb, at a distance from the inter- face connecting the secondary conduit to the main conduit.

As a result of these two features, the opening movement of moving element 5 occurs, for a first portion - i.e. from the closing position (shown in fig. 2b) on valve seat 6 to the position (shown in fig. 2a) of substantial alignment with interface area 9 - entirely within secondary conduit lb; while, for a second portion, moving element 5 takes up a position (shown in fig. 2c) which interferes also with the port of primary conduit la. This means that in the first portion the progressive opening movement of moving element 5 controls exclusively the amount of EGR which is sent for mixing with the entire flow of intake air; while in the second portion it interferes with - i.e. partial- ises - the flow of intake air into main conduit la.

Due to this arrangement, the adjustment of the mixing percentages of air and EGR becomes much more precisely controlla- ble.

As shown in greater detail in the cross-section view of fig. 3 and in the perspective view of fig. 4, moving element 5 con^¬ sists of two main elements 12 and 13.

Element 12 - which, by the geometric shape thereof, provided in this embodiment of the present invention, is briefly defined in the following as vane-shaped element or, more simply, as vane 12 - is rigidly coupled with a small shaft 11 which, in turn, is constrained to the second part of valve body 1, so as to have only the degree of freedom concerning the rotation about an axis orthogonal to the plane of fig. 3, and the trace of which in the same plane is referred to by X; this coupling is accomplished by means of standard tightening screws 18 (visible in the drawing of fig. 4) .

As already stated, and as can be clearly detected in fig. 2a, hinge axis X is located at the outflow area 9, within said acute angle formed between the axes of the main and secondary conduits .

With vane 12 element 13 is associated, in the form of a disc. Said disc 13 is entrusted with the function of sealing on valve seat 6, while vane 12 is entrusted especially with an EGR flow adjustment function.

According to a fundamental feature of the present invention, said coupling between vane 12 and disc 13 is accomplished by means of a connection pin 14, clearly visible in fig. 3. Such coupling takes on specific functional features due - on the one hand - to the particular geometrical configuration of both coupled elements, i.e. of disc 13 and of vane 12, and - on the other hand - due to the presence of a single elastic element 15, as better detailed in the following.

In such respect, as a matter of fact, it can be observed that vane 12 has a conical surface 12b, which contacts a spherical surface 13b, formed on disc 13 in the interface area with the vane. Overall, the coupling which is established between vane 12 and disc 13 has the functional features of a spherical joint, which are advantageous in terms of intrinsic capabilities of fine adjustment of the position of disc 13, as explained in the following.

Moreover, the only elastic element 15, which keeps disc 13 and vane 12 coupled, consists of a single Belleville washer, ar^¬ ranged between the end 14a of pin 14 and the surface 12a of the vane; on the side opposite to head 14a, pin 14 has a stop edge 14b, which rests within a housing 13c of disc 13. A further device adopted in the construction solution of the moving element of the EGR valve proposed by the present invention consists in the arrangement of a fastening element 16, which constrains disc 13 to vane 12 so as to prevent a relative rotational movement of disc 13 with respect to vane 12. Thereby the rotation of disc 13 about its own axis is prevented, which might arise during the valve opening/closing manoeuvres, which imply the rotation of the vane around axis X. The setting on of a relative displacement of disc 13 with respect to vane 12, con- sisting in a rotation of the disc about the axis of pin 14, might negatively affect the motion field of the EGR flow, and might furthermore imply undesired phenomena of local heat development, due to the friction which would arise in this relative displacement .

A torsional return spring (suitably sized, but not shown) is fastened with one end to shaft 11 and with the other end to body 1 (or possibly directly to the body 17 of the displacement system which controls the rotation of shaft 11); this fastening is not shown in detail since ' it is known per se and in any case lies within the reach of a person skilled in the field. Said torsional spring is mounted so as to act on moving element 5 pushing it towards its own closing position against seat 6.

A further feature of the construction solution of the EGR Long Route valve proposed by the present invention consists in the arrangement of a cooling circuit in the valve body, at outflow section 4, for the inflow of recirculation gas. Such cooling circuit practically consists of an entry conduit 10, a channel 10a, formed within the valve body, in the area which surrounds valve seat 6 (visible in figures 2) , and of an exit con- duit (not shown in the drawings) . The function performed by said cooling circuit is of reducing thermal stresses deriving from the presence of temperature gradients caused by the flow of recirculation gases.

Valve body 1 may consist of a single body or, as schematised in fig. 1, of two distinct bodies - the first part, with conduit la, and the second part, with conduit lb - connected together by means of conventional tightening screws 8, which allow the coupling of a certain number of suitably sized opposite edges. The coupling of valve body 1 with the engine system, i.e. with the drawing system and with the discharge one, occurs in an equally conventional fashion, by means of flange-like surfaces in the areas 7 and 4a (v. fig. 1) , on the first part and on the second part of body 1, respectively, and by means of conventional tightening screws .

The operation of the above-described valve - mounted on the intake side, as stated above - provides that the air flow directed towards the engine intake runs through entry section 2, flows within the main conduit la of the valve body and mixes with the recirculation gas flow rate coming in from the outflow section 4 and flowing through interface section 9. The mixture of the two flow rates, the intake air one and the recirculation gas one, flows out from the main conduit la of the valve through exit section 3.

The construction solution of the EGR Long Route valve according to the invention has hence distinct, fluid "three ways", i.e. three flow sections affected by flow rates which are different not only in terms of features of the motion field, but also in terms of composition: outflow section 2 for the entry of intake air flow rate; outflow section 4 for the entry of the recirculation gas flow rate; and finally outflow section 3 for the exit of the flow rate resulting from the mixing of the preceding two .

The EGR flow rate must be suitably adjusted according to a precise logic of the MCI engine management, and it is hence variable depending on the engine operating conditions .

In addition, as already stated, whenever the EGR valve is led to take up the closed configuration (fig. 2b) it is necessary that resistance to seepage of recirculation gases is kept high, despite the pressure difference existing between upstream and downstream of section 4 of the recirculated gas outflow.

All the described functions, i.e. that of adjusting the flow rate of the EGR gases coming in from outflow section 4 into sec- ondary conduit lb and/or that of adjusting fresh air flow in main conduit la, as well as that of sealing valve seat 6 due to the effect of the perfect adhesion of disc 13 on seat 6, are carried out by the cited single moving element 5 of the valve.

More in detail, the flow rate adjustment function is practically carried out by the vane, which performs a progressive par- tialisation of the incoming EGR flow rate to the valve from outflow section 4. The partialisation degree of the EGR flow rate depends on the angular position taken up by the vane, around axis X, within the angular rotation range which characterises the motion law.

As already stated above, the opening movement of moving element 5 occurs, for a first portion, entirely within secondary conduit lb: namely, for the entire travel starting from the closing position (fig. 2b) on the valve seat 6 and up to the position (fig. 2a) of substantial alignment with interface area 9. During this travel the position of moving element 5 determines exclusively the variation of the EGR amount which is sent for mixing with the amount of intake air which flows, unaffected, through primary conduit la; in other words without the vane interfering at all with the intake air flow into primary conduit la.

Then, continuing the opening movement of moving element 5, said element, in a second portion of its path, arrives at subse- guent positions (figs. 2c, 2d) which interfere also with the port of primary conduit la. This means that in this second portion it partialises, in a more or less marked way, the intake air flow in main conduit la; thereby, the moving element determines a pressure variation, i.e. a greater depression on the side of the secondary conduit, facilitating a greater supply of EGR in the outflow.

Such motion law, as already stated, is implemented by a control system known per se, which is based on an electric device, such as a direct-current electric motor, and which can make use of a transmission with one or more reduction stages . In the present invention the control system of the moving element of the EGR Long Route valve is to be intended as being known per se and therefore it is represented only through body 17 (fig. 1) which contains all the constituent elements thereof; said body is rigidly coupled with the valve body.

In greater detail, the operation of the valve according to the present invention and the advantages deriving therefrom - when the valve is mounted on the intake side of the MCI engine - are more evident from the following description of the valve- closing manoeuvre (fig. 2b) , starting from a generic open-valve configuration (fig. 2a) , and of the manoeuvre of fully opening the valve (fig. 2c) , up until comprising the partialisation of the air being taken in to the MCI .

When, starting from a generic open valve configuration (as in fig. 2a or 2c) , the closing manoeuvre is performed, then vane 12 is led to make a clockwise rotation (with respect to the drawing) around axis X, moving against the direction of the EGR flow coming from the outflow section 4 of secondary conduit lb. It is observed that at the beginning of the closing manoeuvre the surface 13a of disc 13 moves along a trajectory which is not parallel, but oblique, with respect to the direction of the EGR flow; such trajectory then becoming virtually parallel to the flow direction only in the final portion of the closing travel . The closing manoeuvre is defined so that, upon completion of such manoeuvre, the surface 13a of disc 13 abuts against the planar surface of the circumferential edge of element 6; this element, which acts as valve seat, is arranged on the secondary conduit lb of the valve body, at the outflow section 4 of the recirculation gas.

At this point the advantages deriving from the functional features of the spherical joint which characterise the coupling established between vane 12 and disc 13 can be understood. As stated before, such advantages are measured in terms of an intrinsic capability of fine adjustment of the position of disc 13 with respect to the abutment surface of valve seat 6; in par- ticular disc 13, and hence surface 13a, moves towards the abutment surface along a trajectory which, in the last portion of the valve closing travel, is virtually parallel to the EGR flow. Moreover, upon the disc 13 resting on valve seat 6, a free adjustment of disc 13 in a position of perfect coupling with valve seat 6 is possible.

When, starting from the closed-valve configuration, the manoeuvre of full valve opening is performed, then vane 12 is led to perform an anticlockwise rotation around axis X, this time moving in the same direction as the EGR flow coming from outflow section 4. Moreover, in the first portion of the opening manoeu- vre, where the moving away of surface 13a of disc 13 from the surface of seat 6 occurs, surface 13a moves along a trajectory which is virtually parallel to the flow direction of the recirculation gases .

In the opening movement from the closed position (fig. 2b) to a generic intermediate position (fig. 2a), vane 12 performs the partialisation of the EGR flow introduced - in smaller or larger amounts - into the intake air flow to the MCI engine which runs through main conduit la, from entry 2 to exit 3.

However, continuing the anticlockwise rotation of moving valve element 5, beyond the intermediate position of fig. 2a and up to the overcoming of the interface section 9 between the flows, vane 12 also accomplishes the partialisation of the intake air flow to the engine. The intake air partialisation comprises an increase of system performances in terms of permeabil- ity to recirculation gas flow. Upon reaching the configuration of full valve opening (fig. 2c) , which corresponds to the maximum angular excursion provided by the vane motion law, the maximum partialisation of the incoming air flow rate from section 2 of the main conduit la of the valve is obtained. As a matter of fact, the air flow rate is intercepted by the surface 12a of vane 12; such surface hence operates the partialisation of the intake air flow rate to the MCI engine.

For the purpose of a better understanding of the operation dynamics of the EGR valve proposed by the present invention, it is observed that during the closing manoeuvre the control system is called to guarantee to the axis of shaft 11 - whereto vane 12 is connected - the torque which is necessary for overcoming the fluid dynamic resistances and completing the manoeuvre within the desired actuation time. During this closing manoeuvre, the elastic torque of the spring works according to the torque de- veloped by the control system.

On the other hand, during the opening manoeuvre, the control system is called to guarantee to the axis of shaft 11 - whereto vane 12 is connected - the torque necessary for overcoming the elastic torque of the spring and completing the manoeuvre re- specting the predefined actuation times. During the opening manoeuvre, as a matter of fact, the elastic torque of the spring works in opposition to the torque developed by the control system, and to the one deriving from the thrust of the recirculation gas flow.

The control accuracy of the flow rate of burnt gases may be varied depending on the type of application, changing the configuration of the moving element of the valve, of the main conduit and of the secondary one, and of the respective outflow sections. The alteration of one or more of these components af- fects the actual profile of the outflow area. The control resolution of the flow rate is the ratio at which the actual outflow area changes whenever the moving element moves towards the valve seat; such ratio may be controlled and predetermined. The profile of the outflow area may be changed so that the movement progression causes - due to valve permeability - a relatively slow growth, or a proportional increase, or else a relatively fast growth.

For the definition of the profile configuration of the outflow area it can be proceeded with an experimental-type approach (laboratory fluxing tests) , but preferably the optimisation of the outflow area provides the wide use of CFD analyses during the planning phase and subsequently the experimental verifica^¬ tion, as known in the art.

Again with respect to the operation dynamics of the EGR valve discussed in the present invention, it is observed that, should a malfunctioning of the control system occur during nor- mal valve operation, it is nevertheless possible to guarantee a closing manoeuvre of the valve within a suitable time. Such safety actuation is guaranteed by the presence of the torsional spring acting on shaft 11 and hence of the elastic return torque imparted by said spring, which tends to bring vane 12 into a closed position, i.e. the surface 13a of disc 13 in abutment against the surface of seat 6.

In addition to making possible the safety actuation just described, in standard operation conditions the elastic torque of the spring contributes to the high performances of the EGR valve in terms of resistance to seepage of recirculation gases, when the valve is in the closed configuration.

The description of the embodiment of the invention discussed so far provides an application in connection with a recircula- tion system of the type schematically reported in fig. 5. It is observed here that the EGR valve, as illustrated in fig. 1, is arranged upstream of compressor C, and makes possible the parti- alisation of the LPE flow of EGR gases, cooled by cooler CO, and/or the intake air to the engine. The recirculation system considered is the conventional one of a supercharged, diesel, internal combustion engine and provided with devices for the processing of exhaust gases, such as a CAT catalytic converter and a Diesel particulate filter DPF. The other elements found in the diagram are a standard air filter AF, an air flow meter AFM, a turbine T, an Intercooler IC, and an engine block MCI, whereto the intake manifold IM and the exhaust manifold EM are connected.

The preferred embodiment of the present invention as "three- way" EGR Long Route valve - as described above with reference to the enclosed drawings - is liable of a further application with no substantial changes to the construction solution described so far being necessary. More precisely, the only change consists in the different arrangement of the "three-way" Long Route valve in the EGR recirculation system in the MCI, i.e. on the discharge side instead of on the intake side of the MCI engine . This application consists in the arrangement of the EGR valve in a recirculation diagram as reported in fig. 6, wherein the MCI engine is of the same type as the one shown in fig. 5, while the function performed by the three valve outflow sections is different, since the operating conditions of the valve differ.

Such different valve arrangement, in connection with the MCI internal combustion engine, allows to carry out a new application of the technique of the controlled recirculation of exhaust gases in an MCI and hence defines a further EGR Long Route system, which is again innovative in terms of operating features and performances .

Through this different arrangement it is possible, still in the context of the present invention, to propose a valve which, in addition to the functional features of high permeability and high resistance to seepage, can furthermore allow the partiali- sation of the gas flow rate when going out from the MCI discharge system, without necessarily implying burdensome complications of the construction solution of the system.

For a better understanding of this different arrangement of the invention, in the following a short description of how the valve should operate with reference to fig. 6 is provided, and keeping the reference to the same drawings of the enclosed drawings and in addition to fig. 2d, for what concerns the valve structure (of which, therefore, the construction features are not repeated, since they are unchanged with respect to the embodiment discussed before) .

The "three-way" EGR Long Route valve can be envisaged applied with the outflow section 3 of main conduit la as inflow section of the exhaust gases (reference EG-IN in fig. 2d) , with the outflow section 4 of the secondary conduit lb as EGR exit section (reference EGR in fig. 2d) towards the mixing with combustion air, and hence towards the engine supply, and finally with the outflow section 2 of the main conduit la as exit sec- tion (reference EG-OUT in fig. 2d) of the burnt gas flow rate not involved in recirculation. When, starting from the closed- valve configuration, the valve-opening manoeuvre is performed, then vane 12 is led again to perform an anticlockwise rotation, about axis X, and the control system is therefore called to guarantee to the axis of shaft 11, whereto vane 12 is connected, the torque necessary for overcoming the elastic torque of the spring and to complete the manoeuvre while respecting the predefined actuation times .

In a generic open-valve configuration the incoming burnt gas flow rate from the outflow section 3 of the main conduit la of the valve is partialised by moving element 5 so that only a dosed share of such flow rate flows to the outflow section 4 of the secondary conduit lb of the valve, while the remaining part of the exhaust gases flows out from outflow section 2.

The flow rate of burnt gases flowing to the outflow section 4 makes up the EGR flow rate to be sent to the intake of the MCI. The greater the width of the anticlockwise rotation - up until reaching the configuration of full-opening of the valve (fig. 2d), corresponding to the maximum angular excursion provided by the motion law of moving element 5 - the greater the flow rate of burnt gases channelled to the MCI supply. The remaining part of exhaust gases is instead caused to exit and discharged to the outside through the section 2 of main conduit lb. Continuing with the valve opening beyond the interface section 9, the partialisation of the flow rate of exhaust gases which runs through the main conduit la is obtained; this implies an improvement of the valve performances in terms of permeability to the flow of the exhaust gases to be recirculated, due to a pressure increase in the area of main conduit la upstream of the valve. Upon reaching the fully-open valve configuration (fig. 2d) , corresponding to the maximum angular excursion provided by the motion law of moving element 5, the maximum partialisation of the flow rate of exhaust gases which runs through the main conduit la is obtained. The fundamental feature of this further embodiment hence consists in the fact that the "three-way" EGR Long Route valve processes the sole flow deriving from the discharge system of the MCI, despite the number of outflow sections characterising the valve remaining equal to three.

The operation of the EGR valve is defined by a precise control logic which, through suitable circuitry, processes the signals coming from the sensors found on the device and in particu- lar from a sensor dedicated to the detection of the position taken up by the moving element 5 of the valve and, based on the type of predefined control strategy, actuates the control system of the moving element 5 of the valve so as to actuate the suitable motion law. The description of the control logic and of the type of circuitry and sensors which make it actuatable lies outside the context of the present invention.

Finally, it must be highlighted how the present invention proposes a device which, in addition to having the features of high permeability, high resistance to seepage, admitting the partialisation of the motion field (intake side or discharge side) , allows, more in particular, an accurate adjustment of the EGR flow rate with simple means which can be easily controlled, and using a single actuator. The EGR flow rate adjustment capability which can be achieved by the present invention can be de- fined through a linear characteristic between the EGR percentage flow rate and the moving angle, computed starting from the closed-valve configuration, of the moving member of the valve. Such type of feature for example is represented in the diagram reported in fig. 7, wherein the value of the opening angle of the moving element 5 of the valve is reported on the abscissa axis and the value of the corresponding EGR flow rate - expressed as flow rate percentage value - on the ordinate axis .

However, it is understood that the invention must not be considered limited to the arrangements illustrated above, which represent only exemplifying embodiments thereof, but that a number of variants are possible, all within the reach of a person skilled in the field, without departing from the scope of pro^¬ tection of the invention, as defined by the following claims. LIST OF THE REFERENCE CHARACTERS

I) valve body- la) main conduit

lb) secondary conduit

2) outflow section

3) outflow section

4) outflow section

4a) flanged area

5) moving element of the valve 6) valve seat

7) connection flange

8) tightening element

9) interface section

9a) outflow section

10) cooling circuit entry

10a) cooling circuit conduit

II) shaft

12) vane

12a) vane surface

12b) vane-disc coupling surface

13) disc

13a) disc sealing surface

13b) disc-vane coupling surface

14) disc-vane connection element 15) elastic element

16) vane-disc constraint element

17) moving device body

18) vane-shaft tightening screws

Claims

1) Valve assembly for low-pressure applications of the controlled recirculation of exhaust gases of an internal combustion engine (MCI) comprising: a valve body enclosing a main conduit (la) , with a first outflow section (2) at one of the ends thereof, and a second outflow section (3) at the other end, as well as a secondary conduit (lb) , which has a third outflow section (4) , at one end thereof, and which, at the other end, connects to said main conduit (la) through an interface section (9a); and at least one moving member (5) acting as adjustment valve of the flow which flows through said secondary conduit (lb) and which runs into said main conduit

characterised in that

one valve seat (6) is formed within said secondary conduit (lb) , at a distance from said interface section (9a) , and

in that said moving member (5) moves, in the travel thereof between the closing position on said valve seat (6) and the maximum opening position thereof, on a first portion exclusively within the secondary conduit (lb) , and precisely between the closing position on said valve seat (6) and said interface section (9) , and subsequently in a second portion, through the port of said primary conduit (la) ,

said moving element (5) thus acting as a partialisation means of the flow rate in said secondary conduit and/or in said main conduit.

2) EGR valve assembly as claimed in claim 1, characterised in that said secondary conduit connects to said main conduit at an acute angle, the hinge of said moving element being arranged within said secondary conduit, preferably near said acute angle and said interface section (9) .

3) EGR valve assembly as claimed in claim 1, characterised in that said moving element is shaped as a composite vane-and- disc element, said vane acting as flow adjustment element and said disc element essentially acting as sealing member of the valve seat, between the vane and the disc a ball-joint coupling having been accomplished through a connection pin (14), which runs through a central hole both of the vane (12) and of the disc (13), as well as through a single elastic element (15) which retains the disc (13) against the vane (12), the vane having, in correspondence of the central hole thereof, a tapered surface (12b) which offers itself to contact with an opposite spherical surface (13b) , formed as small rim projecting from the surface of the disc (13), in the interface area with the vane

(12) .

4) EGR valve assembly as claimed in claim 3, characterised in that said elastic element (5) , which keeps coupled the disc

(13) and the vane (12), is shaped as an individual Belleville washer (15) arranged between a widened head (14a) , formed at the upper end of the pin (14), and the surface (12a) of the vane

(12) .

5) EGR valve assembly as claimed in claim 3 or 4, characterised in that said connection pin (14) has, on the side opposite to the head (14a) , a stopping rim (14b) , which rests within a recessed housing (13c), formed in the lower surface (13a) of the disc (13) .

6) EGR valve assembly as claimed in one of claims 3 to 5, characterised in that a stopping pin (16) is fastened on the vane (12) and projects in an opposite recess of the disc (13), acting as constraint of the disc (13) against the rotation about the axis of the pin (14) .

7) EGR valve assembly as claimed in any one of the preceding claims, characterised in that said vane is mounted integral with a shaft (11) which is rotatable on an axis arranged within said second part of the valve body (1) , and in that on said shaft (11) there is furthermore mounted a torsional return spring, fastened with one end to said shaft (11) and with the other end on said second part of the valve body (1) , so that its action is performed in the same direction as the torque generated by said motor means on said shaft during the closing of the valve seat, so as to improve the closing against seepage and to perform a safety action during closing in case of failure of said motor means . 8) EGR valve assembly as claimed in any one of the preceding claims, characterised in that said valve seat consists of the planar surface of the circumference rim of an annular element (6) , which is made as an insert piece, housed in correspon- dence of said third outflow section (4) .

9) EGR valve assembly as claimed in any one of the preceding claims, characterised in that it comprises a cooling circuit of the valve body, made in correspondence of said third outflow section (4), on said second part of the valve body (1).

10) Recirculation system of the exhaust gases in an internal combustion engine equipped with means for controlling and adjusting at low pressure the recirculation of exhaust gases of an EGR Long Route, characterised in that said means consist of a valve assembly as claimed in any one of the preceding claims.

11) Exhaust gas recirculation system as claimed in claim

10, characterised in that said valve assembly is mounted on the engine intake side, said first outflow section (2) acting as the inlet section for the intake air to the engine (MCI) , said third outflow section (4) acting as inlet section for the recircula- tion gas, and said second outflow section (3) acting as outflow section for a mixture of air and recirculation gas.

12) Exhaust gas recirculation system as claimed in claim

11, characterised in that said vane-and-disc moving member moves starting from a sealing position on said valve seat (6), wherein any exhaust gas recirculation is prevented, progressively towards at least an intermediate position wherein it allows at least partial exhaust gas recirculation, without interfering directly with the intake air flow, and up to a fully-open position, wherein the interference with the incoming air flow into the main conduit is greatest and hence the maximum partialisa- tion of said air flow occurs.

13) Exhaust gas recirculation system as claimed in claim 10, characterised in that said valve assembly is mounted on the engine discharge side, said second outflow section (3) acting as inlet section for the burnt gases coming out of the engine (MCI) , said third outflow section (4) acting as outflow section of a controlled amount of recirculation gases, and said first outflow section (2) acting as outflow section for excess burnt gases .

14) Exhaust gas recirculation system as claimed in claim 13, characterised in that said vane-and-disc moving element moves starting from a sealing position on said valve seat (6), wherein any exhaust gas recirculation is prevented, progressively towards at least an intermediate position wherein it allows at least partial exhaust gas recirculation, without interfering di- rectly with the flow of incoming exhaust gases into the main conduit, and up to a fully-open position, wherein the interference with the exhaust gas flow in the main conduit is greatest and hence the greatest partialisation of said exhaust gas flow occurs .