DE202015009430U1 - Atomizer of an electric injection nozzle for an injection system for an internal combustion engine - Google Patents

Abstract

An atomizer (10) of an electric injection nozzle (1) for an injection system for an internal combustion engine, the atomizer comprising a nozzle (11), comprising: - a passage (13) extending along a longitudinal axis (5) and a guide hole (46 ); - A front surface (40) which lies outside of the passage (13); - a seal seat (21) formed by a chamfer or a groove connecting a cylindrical surface (41) of the passage (13) with the front surface (40); the atomiser further comprising a needle (27), comprising: - a head (20) connectable to the seal seat (21); - A rod (43) which has a smaller diameter than the head (20), axially from the head (20) protrudes and in the passage (13) engages; the rod (43) and the nozzle (11) forming therebetween radially a passage (16) through which a stream of high pressure fuel can flow; and - a first carriage portion (25) connected in an axially slidable manner to the guide hole (46) so as to form a dynamic seat; wherein the needle (27) is axially movable at an opening stroke directed axially outwardly from the passage (13), starting from a closed position in which the head (20) is connected to the seal seat (21) to form a static fit and close the nozzle (11); the seal seat (21) and the head (20) forming an output section (14) which is annular and has a width which increases as the opening stroke of the needle (27) progresses; characterized in that - the cylinder surface (41) has a diameter equal to that of the guide hole (46); - The diameter of the guide hole (46) is between 2.5 and 3.3 mm; - The seal seat (21) has an average diameter which is greater than the diameter of the guide hole (46), wherein the difference (R) between these two diameters causes the fuel pressure exerts an opening, unbalanced force on the needle (27) when the nozzle (11) is closed: wherein the mean diameter of the seal seat (21) is such that the opening unbalanced force is less than or equal to 50 Newtons when the feed pressure of the fuel in the passageway (16) is a value from 2400 bar.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an atomizer for an electric injector, particularly in the piezoelectric or magnetostrictive type, for a high-pressure injection system for an internal combustion engine. More particularly, the present invention relates to an electric injector for a common rail type injection system for a diesel engine.

STATE OF THE ART

In internal combustion engines, the injectors are provided with a nebulizer having a nozzle and a needle which moves under the action of an actuator to open and close a seal seat provided on the nozzle.

In other solutions, the atomizer has a needle of the so-called pin construction, that is, a nozzle that opens when the needle moves outward (nozzle type opening outward). In other words, in this type of atomizer, the nozzle is opened by pressing the needle by means of a piezoelectric or magnetostrictive actuator.

Solutions of this type are described, for example, in EP1559904 and FR2941745 ,

In this type of solution, the electrical control signal supplied to the actuator causes the actuator to be elongated in proportion to the electrical control signal supplied, and this elongation in turn causes the needle to shift in a direction coincident with the aforementioned elongation. If no electrical control signal is present, the actuator automatically shortens to its initial length. It will be understood that the axial position of the needle and thus the round cross-section of the fuel delivery will vary continuously and not discretely according to the electrical control signal applied to the actuator.

In the EP1559904 described solution works directly. In other words, the elongation of the actuator causes an identical axial displacement of the needle. Instead, in the in FR2941745 described solution, the actuator by means of a hydraulic connection, namely a fuel-filled chamber connected to the needle. This chamber is intended to compensate for the play in the assembly phase and the dimensional changes of the needle during operation.

However, in FR2941745 affects the axial movement of the injection needle through the entirety of the fuel pressure surrounding the injection needle when the seal seat is closed.

In addition, it appears that the seal seat of the nozzle has a sharp circular edge which could cause high stress on the nozzle material and thus the occurrence of nozzle defects or breakage.

A similar solution too FR2941745 is in the European Patent Application 13189601.1 on behalf of the same Applicant and on the priority date of this application. This document shows a needle which is axially balanced with respect to the fuel pressure when the nozzle is closed by a connection head of the needle. In particular, the needle comprises an area opposite this head and coupled to a guide seat in an axially displaceable manner to form a so-called "dynamic seat" between fuel contained in the nozzle and fuel contained in the intermediate part of the injector. The guide seat, or dynamic seat, has a diameter equal to that of the static seal seat of the nozzle. Therefore, when the nozzle is closed, the thrust acting on one side on the end portion of the needle and the head on the head from the other side are equal to each other and therefore cancel each other out. This strategy significantly reduces the force on the static seal seat of the nozzle.

The balancing of the needle is a very important aspect for the behavioral stability of the nebulizer during the various injection events, as this allows to reduce the work sensitivity to the fact that the fuel supply pressure is variable depending on different rotational speeds of the engine. In particular, this supply pressure can have values of over 2200 bar in modern injection systems.

However, tests on this injector have revealed the occurrence of defects and breakage of the needle and / or nozzle due to the high stresses to which they are subjected. To avoid these disadvantages, the most obvious solution would be to increase the diameter of the needle significantly, so as to increase the rigidity and to reduce a contact load between the needle and the nozzle.

A thoughtless increase in this diameter, however, could bring other problems.

In particular, a general increase in the diameter of the needle also leads to an increase in the diameter of the sealing zones of the needle. Because of this increase in axial area, when the nozzle is closed, the fuel pressure induces a greater amount of strain on the needle, even when the latter is "balanced," and this stretch condition causes the needle to stretch, thus causing undesirable elongation.

In addition, an increase in the diameter of the seal zone on the dynamic seat causes an undesirable increase in fuel loss from the nozzles at the intermediate part of the injector: the clutch play on the dynamic seat could be reduced as a countermeasure, but this would entail an increase in production costs and secondly Increase the risk of making the needle hyperstatically, thereby impairing its proper closure.

Further, with an increase in the seal diameter at the seal seat of the nozzle, it would be necessary to reduce the stroke of the needle to obtain the same outlet area and thus the same amount of injected fuel (for the same fuel supply pressure). This reduction in stroke also reduces the accuracy and precision of the amount of injected fuel: in fact, with a large seal diameter, even small errors in the trajectory of the actuator, and thus in the needle stroke, have a decidedly more pronounced effect on the amount effectively injected Fuel, especially for operating conditions with minimum or partial engine load, ie for small volumes of fuel that need to be injected into the combustion chamber. In other words, these small errors cause greater inaccuracy in injection relative to that dictated by design, and thus make emissions significantly worse.

Finally, the end of the needle is exposed to the pressure in the combustion chamber, which can reach up to 200 bar and produce a closing force, the total of which is proportional to the static seal diameter and must be overcome to open the nozzle and thus inject fuel As a result, a larger static seal diameter causes a higher closing force exerted by the pressure in the combustion chamber and would require a more powerful actuator with an undesirable increase in cost.

US Pat. No. 7,942,349 B1 discloses a further atomizer with a needle in so-called pin-type construction. This document discloses a metering element that restricts fuel flow in a passage into which a rod of the needle engages. In the US Pat. No. 7,942,349 B1 The disclosed injector is considered to be balanced under pressure when the injector is closed.

SCOPE AND SUMMARY OF THE INVENTION

The object of the present invention is to provide an atomizer of an electric injector for an injection system for an internal combustion engine with which the above-described disadvantages are solved in a simple and inexpensive manner, and preferably the right compromise for the diameter of the needle and, quite generally, for the geometry and configuration of the nebulizer.

According to the present invention, there is provided an atomizer for an electric injection nozzle for an injection system for an internal combustion engine according to claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, some preferred embodiments will now be described by way of non-limiting example only and with reference to the accompanying drawings, in which:

1 shows in cross-section along a longitudinal section a first preferred embodiment of the atomizer of an electric injection nozzle for an injection system for an internal combustion engine according to the present invention;

2 an enlargement of the atomizer in 1 is;

3 a perspective sectional view of a detail 2 shows;

4 similar 2 and showing a variant of the nebulizer according to the present invention;

5 in perspective a detail 4 shows; and

6 similar 5 is and shows a further variant of the atomizer according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described in detail with reference to the accompanying drawings in order to enable one skilled in the art to make and use the same.

In 1 gives reference signs 1 as a whole, an electric injector (shown schematically) forming part of a high pressure injection system for injecting fuel into a combustion chamber (not shown) of an internal combustion engine. In particular, the injection system is in the design of a common rail for a diesel engine.

The electric injector 1 includes an injection body 4 that extends along a longitudinal axis 5 extends, preferably formed by a number of parts fastened together and an inlet 6 to obtain high-pressure fuel supplied, in particular at a pressure in the range between 600 and 2800 bar. In particular, the inlet 6 (in a manner not shown) connected to a common rail, which in turn is connected to a high-pressure pump (not shown), which also forms part of the injection system.

The electric injector 1 ends in a fuel atomizer 10 with a nozzle 11 attached to the injection body 4 is attached. The electric injector 1 includes a valve needle 12 , which are along the axis 5 extends and axially into an axial seat or passage 13 for opening / closing the nozzle 11 is movable, with an opening shock directly axially from the seat to the outside and a closing impact directly into the nozzle 11 of the injection body 4 is performed inside.

With this given motion configuration, this type of electric injector becomes 1 generally referred to as "outwardly opening nozzle type" or as "nozzle pin".

In the in 1 example shown is the valve needle 12 formed by two separate parts, which are arranged axially adjacent to each other. In particular, the valve needle 12 formed by a needle 27 which part of the atomizer 10 is, and by a drive rod 28 in an intermediate zone of the seat 13 of the injection body 4 is arranged. Alternatively, the valve needle 12 formed by a single component.

The nozzle 11 includes a seal seat 21 which together with a head 20 the needle 27 a delivery cross-section 14 for the fuel. The delivery cross section 14 has a continuous circular, crown-like shape, with a width that is constant along the circumference, but with progressing opening stroke of the valve needle 13 continuously increases.

The fuel is therefore injected with a Sprühfächer in the combustion chamber, along the circumference of the output cross-section 14 is homogeneous, ie a conical or "screen" spray fan, and with a variable flow rate proportional to the axial stroke of the needle 27 is.

As explained below and as in 3 can be seen, the seal seat 21 not formed by a sharp edge, but by a chamfer or a radius of curvature, which is a front surface 40 , outside the seat 13 and the seal seat 21 , with a cylindrical surface 41 inside the seat 13 connects to the pressure or the specific load of the head 20 on the nozzle 11 during the closing process, thus reducing stress and risks of fatigue failure.

The head 20 has an outer diameter that is greater than the maximum diameter of the seal seat 21 and the rest of the needle 27 , Near the nozzle 11 is the head 20 through a surface 42 limited to the seal seat 21 closing abut and by a truncated cone or a convex segment of a sphere, symmetrical with respect to the axis 5 , is formed. These two components, when in contact, form a single "static seal", ie, a seal that provides perfect closure of the outlet of the nozzle 11 guaranteed.

The seal seat 21 is advantageously formed by a chamfer, which has a cone angle equal to the surface 42 has and thus complementary to the surface 42 so as to ensure that a contact is formed by a surface, rather than a circular line, such that the specific load is reduced. In addition, this configuration allows the design-specific entirety or extent of the seal seat 21 is achieved in a relatively accurate manner by the machining of the chamfer.

The angle at the vertex passing through the cone of the surface 42 is formed, is preferably between 100 ° and 150 °. This angle must be during design according to the characteristics of the engine (for example, the bore and / or the shape of the combustion chamber, the tumble index, etc.), other characteristics of the injector 1 (through the actuator 32 defined maximum impact, diameter of the static seal, etc.) and characteristics of the injection system ( maximum injection pressure, type of injection strategies, etc.). For example, if it is desired to apply the smallest possible static seal diameter, it is necessary to have the largest possible angle at the vertex of the surface 42 to take (between 140 ° and 150 °), so a more salient output cross-section 14 sure.

According to a variant which is not shown, the seal seat becomes 21 formed by a radius of curvature, the area 42 has a recess or notch defined by the inverse of this radius of curvature, ie, by a concave surface complementary to that of the radius of curvature. Also in this case the contact is formed by an annular surface.

From the point of view of manufacture it is possible to have this recess on the surface 42 to get by in a temperature controlled environment the nozzle 11 and the needle 27 are set in a mutual rotation and for a predetermined machining time, a certain axial load is applied and preferably a fluid containing abrasive microparticles are applied to the friction surfaces.

Alternatively, a contact is made on the seal seat 21 along a circular line and not on a surface, for example in the case where the seal seat 21 is formed by a bevel and the surface 42 is formed by a convex segment of a ball (with the advantage of automatically centering the needle 27 in the closing phase with respect to the nozzle); or in the case where the seal seat 21 is formed by a radius of curvature and the surface of the seal seat 21 has a truncated cone shape.

These solutions with a circular contact line are still advantageous even if the specific load is not reduced. In fact, predictive computer simulations and some experimental fatigue life tests on similar products have found overloading on the material of the nozzle 11 at the seal seat 21 however, it is less in relation to a state of contact with a sharp edge of the nozzle 11 ,

As mentioned above, the seal seat 21 and the needle 27 so that they have an output cross-section 14 which varies continuously and not in a stepwise discrete manner as the axial position of the needle increases 27 changed. In particular, starting from the closed position in which the head 20 on the seal seat 21 stores and the nozzle 11 therefore closed, the outward opening impact of the needle 27 an initial opening of the nozzle 11 and then a progressive increase in the delivery cross-section 14 for the fuel.

Therefore, with a relatively small opening shock, the discharge cross section 14 also relatively small, and so the fuel is injected with a high degree of atomization and characterized by a moderate penetration Sprühfächer. For a relatively long opening shock is the output cross section 14 also relatively long: Thus, taking into account the special geometry of the head 20 the fuel is injected with a spray fan characterized by high penetration. This variability of the output cross section 14 may be advantageous in implementing a mixed-mode engine operation mode, namely HCCI (Homogeneous-Charge-Compression-Ignition) mode at low and medium loads, at a fuel atomization degree in the combustion chamber, and a conventional CI type ( Compressed Ignition) mode at high loads, with high fuel penetration in the combustion chamber.

Regarding 2 has the atomizer 10 a passageway 16 , which has at least one channel with the inlet 6 permanently communicates, in the injection body 4 and in the nozzle 11 is formed and by a rod 43 the needle 27 and through the nozzle 11 is defined radially.

The passageway 16 has a passage cross-section which is sufficiently large to allow pressure drops in the nozzle during the injection phase 11 to limit to a minimum. Thus, high pressure fuel does not flow through any microholes, and the amount of fuel injected depends solely on the size of the delivery area 14 and the pressure difference between the annular passageway 16 and the combustion chamber.

At one axial end, the passageway includes 16 an area 44 which is annular and the outlet of the nozzle 11 at the seal seat 21 forms, so that fuel can be injected into the combustion chamber.

In the particular example shown, at the opposite axial end comprises with respect to the area 44 the passageway 16 an annular chamber 18 commonly referred to as a "kidney", which has a wider cross-section than the remainder of the passageway 16 has and pressurized fuel from a channel (not shown) that receives the chamber 18 in communication with the inlet 6 puts. It is therefore plausible that the passageway 16 forms part of a high pressure environment defined by the feed pressure of the fuel. As in 1 is visible, the injector has 4 also a low pressure environment 22 which with an outlet 23 in use, connected to conduits (not shown) which return the fuel to a fuel tank and which are at a low pressure, for example about 2 bar.

to 2 Coming back includes the nozzle 11 at the opposite end with respect to the seal seat 21 a back guide area 45 with a leadership hole 46 passing through a cross section of the seat 13 is defined and in an axially sliding manner by a slider 25 the needle 27 is engaged.

The coupling zone between the area 25 and the leadership hole 46 forms a so-called "dynamic seat". In general, the term "dynamic seat" should be understood as a sealing zone formed by a shaft / hole type coupling with a sliding action and / or a guide between the two components, with clearance in the radial direction being sufficiently small to neglect the amount of fuel that seeps through it. In particular, this clearance of the radial clutch is less than or equal to 2 microns. Also, due to the small size of this radial clearance, a relatively small amount of fuel escapes from the chamber 18 : This fuel then becomes the outlet 23 flow to return to the fuel tank. Preferably, but not exclusively, the above-mentioned "dynamic seat" separates the chamber 18 the passageway 16 axially from the low pressure environment 22 ,

The diameter of the area 41 at the outlet of the seat 13 is equal to the guide hole 46 while in the other zones of the passageway 16 the inner diameter of the nozzle 11 greater than or equal to this value. In this way it is possible to provide a needle 27 , which is formed by a one-piece body, during the assembly of the injector 1 the area 25 the needle 27 through the outlet of the nozzle 11 introduce.

Regarding 3 has due to the radius of curvature or bevel, the / the seal seat 21 forms, this a mean diameter, which is slightly larger than the diameter of the guide hole and the surface 41 ,

The difference R between the diameter of the dynamic seat at the guide hole 46 and the median diameter of the static seal on the seal seat 21 cause an imbalance in the fuel pressure on the needle 27 applied axial forces when the nozzle 11 through the head 20 the needle 27 closed is.

In other words, the slightly larger diameter of the "static seat" relative to the "dynamic seat" causes the fuel pressure to have an opening force on the needle 27 exerts when the nozzle 11 closed is. According to one aspect of the present invention, the average diameter of the "static seat" is designed such that this "unbalanced" opening force is less than 50 N, even if the injection pressure is equal to the maximum value given by the design.

Regarding 1 includes the electric injector 1 to a displacement of the valve needle 12 to induce an actuator 30 , which in turn is an electrically controlled actuator 32 that is, an actuator controlled by an electronic control unit (not shown) programmed for each injection phase of the fuel and the associated combustion cycle in the combustion chamber, about the actuator 32 with one or more electrical control signals to perform corresponding injections of the fuel.

The construction of the actuator 32 is such that an axial displacement is defined in proportion to the obtained electrical control signal: for example, the actuator could 32 be formed by a piezoelectric actuator or by a magnetostrictive actuator. The control device 30 further comprises a spring 35 , which is biased to an axial compression on the actuator 32 exercise to increase the efficiency.

The excitation given by the electrical control signal causes a corresponding axial expansion of the actuator 32 and thus a corresponding axial displacement of a piston 34 coaxially disposed and relative to an axial end of the actuator 32 is attached. In the in 1 shown special example holds the same spring 35 the piston 34 in a fixed position with respect to the actuator 32 ,

The axial displacement of the piston 34 presses on the valve needle 12 and thus causes the opening of the nozzle 11 , against the action of a spring 31 that is biased to the needle 27 to push axially inward, and consequently the nozzle 11 close.

In particular, the spring 31 , as in 2 It can be seen axially between an axial end shoulder of the nozzle 11 , by reference 48 indicated, and an end region 49 the needle 27 arranged. Preferably, the spring is stored 31 on one side axially on a half ring 83 which in turn reaches the end area 49 abuts, and on the other side to a spacer 84 , which in turn axially a half ring 84 abuts, which is stored on the shoulder. Alternatively, the spacer could 84 between the spring 31 and the half ring 83 be arranged. The axial thickness of the spacer 84 can be chosen to match the preload of the spring 31 adjust. The half ring 83 is easy on the needle 27 pushed or is at the needle 27 fastened, for example by welding or interference fit. According to a variant which is not shown, the half-ring is 85 not present while the spacer 84 right on the shoulder 48 outsourced.

Preferably, the spring 31 in a section of the seat 13 arranged, the part of the low pressure environment 22 is.

The feather 31 forms part of the atomizer 10 and advantageously has a preload between 60 and 150 N, so as to exert a sufficient closing force to overcome the above imbalance and the needle 27 immediately return to the closed position as soon as the action of the actuator 32 eliminated. In particular, the bias value of the spring 31 be chosen in the design phase in a proportional manner to the diameter of the static seat, ie the mean diameter of the seal seat 21 , and in a proportional manner to the maximum value of the feed pressure of the fuel.

Regarding 1 is the actuator 32 preferably, but not exclusively, by a hydraulic connection 36 with the valve needle 12 coupled. The hydraulic connection 36 includes a pressure chamber 37 , which with the valve needle 12 and the piston 34 is coaxial and forms a control volume which is filled with fuel, which, once compressed, the axial thrust of the piston 34 to the valve needle 12 transfers. The amount of fuel in the control volume of the pressure chamber 37 varies automatically to the axial play and the dimensional variations of the valve needle 12 during operation in a manner not described in detail.

As in the 2 and 5 seen, the needle is 27 not just through the leadership hole 46 but also through a zone 50 the area 51 axially guided. The needle 27 includes a plurality of sectors 51 , which off the rack 53 protrude radially, so as to the zone 50 be coupled in an axially sliding manner, axially from the head 20 and the area 25 are arranged away and separated by gaps, which form part of the passageway 16 form the axial passage of the fuel toward the area 44 permit.

The cross section of the passage area for the fuel at such gaps is relatively large, namely this is greater than the area of the passage cross-section 14 even if the stroke of the needle 27 reaches its highest value, so that this forms no restriction in the flow and therefore no restriction in the flow rate of the fuel, which only by the stroke of the needle 27 has to be defined.

According to the variant of 6 are the sectors 51 through protrusions 51a replaced, which is not a straight line parallel to the axis 5 but have a helical or twisted profile, and which with the zone 50 connected to the function of a carriage. With this configuration, it confers in the passageway during each injection event 16 in the direction of the seal seat 21 flowing fuel of the needle 27 a rotational movement in relation to the axis 5 , This strategy causes relative rotation between the nozzle 11 and the needle 27 To avoid the formation of craters, any residue in the passageway 16 smeared, removed and prevented the formation of coking between the two contact surfaces.

Furthermore, the protrusions give 51a the atomizer 10 leaving fuel an angular motion component, so as to favor the combustion conditions in the combustion chamber.

In the in 2 As shown, the rod extends 43 from the area 25 with a smaller diameter than that of the area 25 so as to have a step or axial shoulder on the chamber 18 to build.

Instead, in the variant in the 4 and 5 the pole 43 : an area 53 that has the same diameter as the area 25 has and an axial extent of the range 25 forms; an area 54 that has a smaller diameter and a smaller length relative to the area 53 and the latter with the sectors 51 axially connecting; and an area 55 who (as in 2 ) the area 44 the passageway 16 forms radially and also a smaller diameter than the area 25 Has. At the same time includes the nozzle 11 a cylindrical zone 57 which covers the entire area 53 the pole 43 facing radially and has a larger diameter than the zone 50 so as to form a widening to the correct passage cross section of the passageway 16 to ensure.

This configuration allows reinforcement of the rod 43 the needle 27 without having to excessively increase the diameter of the above-mentioned static and dynamic seats.

Preferably, the passageway has 16 no chamber 18 because the zone 57 axially with the same diameter up to the guide area 45 extends. The fact that the kidney 18 is omitted, allows an enhancement of the structure of the nozzle 11 and makes them less sensitive to fuel pressure resulting in deformation of the nozzle 11 and consequently to a change in the stroke of the valve needle 12 in relation to the one specified by the design leads.

According to one aspect of the present invention, the diameter of the guide hole is 46 and area 25 between 2.5 and 3.3 mm, so sufficient rigidity and resistance for the needle 27 but without the rise of the valve needle 12 having to change excessively to obtain the desired fuel flow during each injection event and without having a significant increase in fuel loss through the dynamic seal described above.

From simulations performed by the Applicant, the rating given above is for the gauge diameter of the needle 27 and the right compromise to maintain structural integrity while minimizing sensitivity to variations in the feed pressure of the fuel and in the pressure present in the combustion chamber during the injection process.

D [m]

= Durchmesser des dynamischen Sitzes (d.h. des Führungsloches 46, ausschließlich leichter Differenzen aufgrund des radialen Kupplungsspiels mit Bereich 25);

R [m]

= Differenz zwischen dem mittleren Durchmesser des statischen Sitzes und dem Durchmesser des dynamischen Sitzes;

Pmax [Pa]

= gestaltungsspezifischer maximaler Zuführdruck des Brennstoffs für das Einspritzsystem, in welchem die Einspritzdüse 1 installiert ist.

In order to meet the maximum 50 N imbalance requirement, the radial size R of the bevel or groove that defines the seal seat 21 forms that satisfy the following equation: 0 <((D + R) ^ 2 - D ^ 2) Pmaxπ / 4 ≤ 50 in which:

D [m]

= Diameter of the dynamic seat (ie the guide hole 46 , only slight differences due to the radial coupling clearance with range 25 );

R [m]

= Difference between the mean diameter of the static seat and the diameter of the dynamic seat;

P max [Pa]

= design-specific maximum feed pressure of the fuel for the injection system, in which the injector 1 is installed.

By choosing, for example:
Pmax = 2400 bar
D = 3.3 mm
results in: 0 <R ≤ 40 μm.

This is the needle 27 a largely balanced type in relation to the effects of thrust when the nozzle 11 is closed, and so are the operation and the axial impact of the needle 27 minimally sensitive to variations in the feed pressure of the fuel.

Given the geometry of the nozzle 11 , according to the diameter of the guide hole 46 equal to the diameter of the cylindrical surface 41 at the axial end of the seat 13 is, the value R = 0 (equivalent to the perfect balance of the needle 27 against pressure effects when the seal seat 21 is closed) in the embodiment in the 2 and 3 can not be reached.

In the case of a seal seat 21 which is formed by a bevel, which with a frustoconical surface 42 is coupled, a contact takes place along a circular crown. The chamfer has a radial size substantially equal to the above R value. As mentioned above, the presence of a contact surface - and not a circular contact line - between the two components is important to the specific contact load on the seal seat 21 decrease during the closure.

In the case where the seal seat 21 is defined by a radius of curvature that is equal to r - and not by a chamfer - is a recess or notch on the surface 42 Of the head 20 formed complementary to the rounding radius r, to obtain a surface contact and to avoid a linear contact.

It is clear from the above that the design of the atomizer described above 10 Finding the right compromise to increase the life of the injector with respect to known solutions without compromising the operating method.

In fact, it has been found that the seal diameter introduced above and the maximum imbalance set in the opening direction make it possible to achieve a relatively robust solution without further operating characteristics of the injector 1 to impair.

Other advantages have been discussed above or are within the skill of one of ordinary skill in the atomizer art 10 clearly, to which was executed here.

In any case, different modifications can be made to the atomizer 10 carried out The generic principles described may be applied to other embodiments and applications without departing from the scope of the present invention as defined in the appended claims. Therefore, the present invention should not be considered limited to the embodiments described and illustrated herein, but should be accorded the broadest scope consistent with the principles and characteristics claimed herein.

In particular, the nozzle could 11 through an end portion of the injection body 4 be formed, and / or the management area 45 could be a part of the body, separate from the nozzle 11 form, and / or the passageway 16 be replaced by a passage shaped in a different way than shown in the attached figures.

In addition, the pressure chamber could 37 and not an intermediate zone of passage 13 be provided over the dynamic seat.

Furthermore, the valve needle could 12 operated directly, that is, the injector 1 could be without the pressure chamber 37 be.

Finally, the shape of the protrusions 51a in atomizers and injectors having different structural characteristics and / or dimensions than those given above.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1559904 [0004, 0006]
• FR 2941745 [0004, 0006, 0007, 0009]
• EP 13189601 [0009]
• US Pat. No. 7942349 B1 [0017, 0017]

Claims (11)

Atomizer ( 10 ) an electric injection nozzle ( 1 ) for an injection system for an internal combustion engine, wherein the atomizer has a nozzle ( 11 ), comprising: - a passageway ( 13 ) which extends along a longitudinal axis ( 5 ) and a guide hole ( 46 ); - a front surface ( 40 ), which are outside the passage ( 13 ) lies; - a seal seat ( 21 ), which is formed by a chamfer or a groove, which a cylindrical surface ( 41 ) of the passage ( 13 ) with the front surface ( 40 ) connects; the atomizer further comprising a needle ( 27 ), comprising: - a head ( 20 ), which with the seal seat ( 21 ) can be connected; - a pole ( 43 ), which has a smaller diameter than the head ( 20 ), axially from the head ( 20 ) and in the passage ( 13 ) intervenes; with the rod ( 43 ) and the nozzle ( 11 ) between a radial passage ( 16 ) through which a stream of high pressure fuel can flow; and a first carriage area ( 25 ), which in an axially sliding manner with the guide hole ( 46 ) so as to form a dynamic seat; the needle ( 27 ) at one of the passage ( 13 ) axially outwardly opening shock is axially movable, starting from a closed position in which the head ( 20 ) with the seal seat ( 21 ) is connected to form a static seat and the nozzle ( 11 ) close; the seal seat ( 21 ) and the head ( 20 ) an output cross section ( 14 ), which is annular and has a width which increases with the opening of the needle ( 27 ) increases; characterized in that - the cylindrical surface ( 41 ) has a diameter equal to that of the guide hole ( 46 ); - the diameter of the guide hole ( 46 ) is between 2.5 and 3.3 mm; - the seal seat ( 21 ) has an average diameter greater than the diameter of the guide hole ( 46 ), wherein the difference (R) between these two diameters causes the fuel pressure to cause an opening, unbalanced force on the needle (FIG. 27 ) when the nozzle ( 11 ) is closed: wherein the average diameter of the seal seat ( 21 ) has a value such that the opening, unbalanced force is less than or equal to 50 Newton is when the feed pressure of the fuel in the passageway ( 16 ) has a value of 2400 bar. An atomiser according to claim 1, characterized in that the head ( 20 ) through a frustoconical surface ( 42 ) is limited to the seal seat ( 21 ) axially facing; the sealing zone ( 21 ) is formed by a chamfer which has a cone angle to this frustoconical surface ( 42 ) Has. An atomiser according to claim 1, characterized in that the sealing seat ( 21 ) is formed by a radius of curvature and that the head ( 20 ) one to the seal seat ( 21 ) has complementary recess and from the seal seat ( 21 ) is engaged in the closed position. An atomiser according to claim 2, characterized in that the frustoconical surface ( 42 ) forms an angle between 100 ° and 150 ° at the apex. A nebulizer according to any one of the preceding claims, further characterized by a spring ( 31 ) with a bias that exerts a thrust force to the needle ( 27 ) to move to the closed position; where the preload is between 60 and 150N. Atomiser according to one of the preceding claims, characterized in that the cylindrical surface ( 41 ) a guiding zone ( 50 ) separated from the guide hole and axially spaced; with the rod ( 43 ) a second carriage area ( 51 ), which in an axially sliding manner with the guide zone ( 50 ) and at least one, a free space forming part of the passage ( 16 ) for the passage of the fuel in the direction of the seal seat ( 21 ). An atomiser according to claim 6, characterized in that the second carriage area ( 51 ) is formed by at least one projection having a substantially helical profile. Atomiser according to one of the preceding claims, characterized in that the rod ( 43 ) comprises: - a first area ( 53 ), which has an axial extent of the first carriage area (FIG. 25 ) forms; and a second area ( 54 ), which has a smaller diameter and a smaller length in relation to the first area (FIG. 53 ) Has; the nozzle ( 11 ) an extended cylinder zone ( 57 ), which covers the entire first area ( 53 ) is radially facing and has a larger diameter than the cylindrical surface ( 41 ) Has. An atomiser according to claim 8, characterized in that the extended cylinder zone ( 57 ) has a constant diameter and axially on the guide hole ( 46 ) ends. An atomiser according to claims 6 and 8, characterized in that the second region ( 54 ) the first area ( 53 ) with the second carriage area ( 51 ) axially connects. Atomiser according to one of the preceding claims, characterized in that the needle ( 27 ) is formed by a one-piece body.

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