TECHNICAL FIELD

The invention relates to an injector for a system for feeding gas fuel to an internal combustion engine, in particular of an automotive vehicle.

BACKGROUND ART

Known gas fuel feeding systems basically comprise a tank for a fuel in the form of liquefied gas, a pressure reduction device, which is fluidically connected to the tank and is adapted to reduce the pressure of the fuel until it reaches the transition to the gaseous state, and one or more injectors, which are fluidically connected, on opposite sides thereof, to the pressure reduction device and to respective cylinders of the engine, so as to selective inject, according to predetermined time laws, the gas fuel into the cylinders.

More in detail, each injector comprises a hollow casing defining an inlet mouth, which is fluidically connected to the pressure reduction device, and one or more outlet mouths, which are fluidically connected to respective cylinders of the engine. The casing further houses, for the sole outlet mouth available or for each outlet mouth in case there are different outlet paths for the fuel, a relative anchor made of ferromagnetic material, which is movable, due to the action of a respective electromagnet controlled by a control unit, between a first closing operative configuration and a second opening operative configuration, in which it respectively prevents or allows the gas fuel present inside the casing from flowing or to flow through the outlet mouth and from being injected or to be injected, by means of a respective intake pipe, into a relative cylinder.

More in detail, the anchor comprises a shutter, which is adapted to selective strike against the relative outlet mouth .

When the anchor is arranged in the first closing operative configuration, the relative shutter is held by a spring so as to strike against the relative outlet mouth of the injector, in order to prevent the gas fuel from being supplied to the relative intake pipe and, subsequently, to the relative cylinder.

When the anchor is arranged in the second opening operative configuration, the relative shutter does not interfere with the relative outlet mouth, thus allowing the gas fuel to be supplied to the relative cylinder.

The electromagnet usually consists of a core made of magnetic material and of a coil wound on the core, which can be electrically powered in a selective manner. An example of a known injector of the type described above is shown in US 7, 857, 283; in this case, the shutter carried by the relative anchor ends its movement towards the second opening operative configuration against a plate of non-magnetic material fulfilling both the aim of dampening the impact of the anchor on the core of the relative electromagnet, thus reducing the wear thereof, and of avoiding the gluing effect generated by the incomplete extinction of the magnetic field after the deactivation of the coil.

The contact of the two planar surfaces of the anchor and of the plate of non-magnetic material ends with the switching off of the electric control and the consequent closing of the shutter due to the elastic load applied by the sprig and to the pressure present inside the casing (self-closing effect) .

The feeding of gas in internal combustion engines currently involves the use of two types of fuels:

- compressed natural gas, which, because of its own nature, has features that are substantially constant in the different production sites, even though in some cases it can have foreign components, such as oils and other fluids; and

- LPG, which, on the other hand, as it is a product deriving from oil refining, can have features that are highly variable depending on the place of production, with frequent presence of oils and other chemical components in the fluid state .

The presence of oils and other fluids can determine an adhesion effect between the surface of the anchor and the one of the plate of non-magnetic material, against which the former ends, in use, its opening stroke. A similar adhesion effect could also be generated between the anchor and the core, if the plate of non-magnetic material were not present.

In both cases, this adhesion can cause a delay in the times of movement of the anchor to the first closing operative configuration upon deactivation of the coil.

Given the variable features of gas fuels, this delay is inconstant and unforeseeable and it can cause an incorrect operation not only of the injectors, but also of the entire feeding system.

As a matter of fact, direct, sequential and phased feeding systems require injectors with very precise delivery times, characterized by extremely rapid opening and closing times, in the range of milliseconds or even less.

DISCLOSURE OF INVENTION

The object of the invention is to provide an injector for a system for feeding gas fuel to an internal combustion engine, which is capable of overcoming, in a simple and economic fashion, the drawbacks affecting known injectors described above. The aforesaid object is reached by the invention, as it relates to an injector for a system for feeding gas fuel to an internal combustion engine according to claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be best understood upon perusal of the following detailed description of a preferred embodiment, which is provided by mere way of non-limiting example, with reference to the accompanying drawings, in which :

- figure 1 shows, in a perspective view, a system for feeding gas fuel to an internal combustion engine comprising an injector according to the invention;

- figure 2 shows, in an exploded perspective view, the injector of figure 1 ;

- figure 3 is a cross-section, on a larger scale and along line III-III of figure 1, showing the injector according to the invention in a closing operative configuration;

- figure 4 is cross-section, similar to the one of figure 3, showing the injector in an opening operative configuration;

- figures 5 and 6 show, in two different perspective views on a larger scale, a detail of the injector according to the invention;

- figure 7 shows, in a perspective view, a possible variant of the detail of figures 5 and 6; and

- figure 8 shows, in an exploded perspective view, a further possible variant of the detail of figures 5 and 6.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to figures from 1 to 4, number 1 indicates, as a whole, an injector for a system 2 (schematically shown in figure 1) for feeding gas fuel to an internal combustion engine in an automotive vehicle.

In particular, the system 2 basically comprises a tank 3 containing the fuel in the form of liquefied gas, a pressure reduction device 4, which is fluidically connected to the tank 3 and is adapted to reduce the pressure of the fuel until it reaches the transition to the gaseous state, and one or more injectors 1 (a single one in the example shown) , which are fed with the gas fuel flowing out of the pressure reduction device 4 and supply one or more corresponding cylinders 5 of the internal combustion engine.

The description below will make reference to a system 2 of the type shown in figure 1, namely comprising one single injector 1 and one single cylinder 5.

With reference to the figures from 1 to 4, the injector 1 basically comprises:

a hollow casing 6, preferably made of a plastic material, which is provided with an inlet mouth 7 and with an outlet mouth, which are fluidically connected to the pressure reduction device 4 and to the cylinder 5 of the engine, respectively;

- an anchor 10 (figures 2, 3 and 4), which is housed inside the casing 6 between the inlet mouth 7 and the outlet mouth 8 and is selectively available in a first closing operative configuration (figure 3) or in a second opening operative configuration (figure 4), in which it respectively closes or opens the fluidic connection between the mouths 7 and 8, so as to prevent or allow the delivery of the gas fuel to the cylinder 5; and

an electromagnet 11 (figures 2, 3 and 4) to selectively operate the anchor 10.

More in detail, the inlet and outlet mouths 7, 8 project on opposite sides of the casing 6 and extend along one single axis A. Alternatively, the inlet and outlet mouths 7, 8 could extend along parallel and non-aligned axes.

In the example shown, the inlet and outlet mouths 7, 8 are further connected to the pressure reduction device 4 and to the cylinder 5, respectively, by means of fluidic connection means. In particular, the fluidic connection means comprise an inlet pipe 12, which is interposed between the pressure reduction device 4 and the inlet mouth 7, and an outlet pipe 13, which is interposed between the outlet mouth 8 and the cylinder 5. Therefore, the outlet pipe 13 defines an intake pipe for the cylinder 5. With particular reference to figures 3 and 4, the inlet mouth 7 has an end opening 14, which faces the inside of the casing 6, and an end opening 15, which is axially opposite to the opening 14. The opening 15 is fluidically connected to the pressure reduction reduction device 4 by means of the inlet pipe 12 (figure 1) .

The outlet mouth 8, just like the inlet mouth 7, has an end opening 16 (figures 3 and 4), which faces the inside of the casing 6, and an end opening 17 (figures 1, 3 and 4) , which is axially opposite to the opening 16 and is fluidically connected to the cylinder 5. In particular, the cylinder 5 and the opening 16 are fluidically connected to one another by means of the outlet pipe 13 (figure 1) .

Thanks the casing 6 being hollow, the opening 14 of the inlet mouth 7 and the opening 16 of the outlet mouth 8 are open towards a housing compartment 18 for the anchor 10 and the electromagnet 11 (figures 3 and 4); therefore, the outlet mouth 8 is selectively traversable by the fuel coming from the inlet mouth 7.

With reference to the figures from 2 to 4, the anchor

10 is housed inside the compartment 18 of the casing 6 so as to be interposed, along the axis A, between the inlet and outlet mouths 7, 8 and, more precisely, between the openings 14 and 16. More in detail, the anchor 10 is interposed, along the axis A, between the electromagnet 11 and the opening 16 of the outlet mouth 8.

In the example shown, the anchor 10 comprises a plate 20 made of ferromagnetic material, which extends orthogonally to the axis A in the second operative configuration and has an oblong shape in a direction X, which is also orthogonal to the axis A in the aforesaid second operative configuration.

The plate 20 has opposite surfaces 21, 22 (figures 2 to 4), which respectively face the electromagnet 6 and the opening 16 of the outlet mouth 8.

The anchor 10 is further provided with a shutter disc 23, which is made of an elastomer material and is fixed on a side portion 24 of the plate 20, on the side of the surface 22 in a position facing the opening 16 of the outlet pipe 8.

With reference to figures 3 and 4, the injector 1 further comprises a cylindrical spiral spring 25 extending parallel to the axis A and in a position spaced apart from the latter.

The spring 25 has an axial end 26, which cooperates with the casing 6, and an end 27, which is opposite to the end 26 and cooperates with a bar 28 (figures 2, 3 and 4) made of an elastically yielding material. The bar 28 extends along a direction that is substantially parallel to the lying plane of the plate 20 and orthogonal to the axis A.

The bar 28 cooperates, on the side opposite to the spring 25, with the surface 22 of the plate 20. Moore precisely, the bar 28 cooperates with a side portion 30 of the plate 20 opposite to the side portion 24 carrying the shutter disc 23.

The spring 25 is designed so as to pre-load the anchor

10 towards the first closing operative configuration (figure 3), in which the plate 20 is slightly inclined with respect to the axis A and the shutter disc 23 engages the opening 16 of the outlet mouth 8 in a gas-tight manner. By so doing, the shutter disc 23 forbids the fluidic connection between the outlet mouth 8 and the inlet mouth 7 and, consequently, prevents the delivery of the gas fuel to the cylinder 5.

The anchor 10 is further fitted inside the compartment 18 of the casing 8 so as to rotate around an axis B (figures 3 and 4), which is parallel to the direction of extension of the bar 28 and not aligned with respect to the latter both in a direction parallel to the axis A and parallely to the direction X of extension of the plate 20.

More precisely, in the example shown, the anchor 10, by means of its own surface 21, rests on one of the delimiting walls of the compartment 18 by means of a cylindrical pin 31 made of a stiff material, for example a metal material; the anchor 10 rests on the pin 31 along a contact line defining the axis B. The pin 31 extends parallely to the bar 28 and in a position interposed between the shutter disc 23 and the bar 28 parallely to the direction X. The pin 31 is further arranged in a position close to the bar 28.

With reference - again - to figures 3 and 4, the electromagnet 11 comprises a core 32 made of a magnetic material and a coil 33, which is wound on the core 32 and can be electrically powered in a selective manner. In particular, the coil 33 can be electrically powered by means of a plurality of electric terminals and a control unit (not shown) , so as to generate a magnetic field on the anchor 10 opposite to the force exerted by the spring 25 upon the anchor 10 itself.

The electromagnet 11 is housed inside a cup-shaped section 35 extending along an axis that is parallel to the axis A.

In particular, the section 35 comprises a axial end bottom wall 36, which has a rectangular shape and an extension orthogonal to the axis A, and is crossed by an end portion of the inlet mouth 7 adjacent to the opening 14. The section 35 further comprises a prismatic side wall 37, which projects cantilevered from the bottom wall 36 towards the outlet mouth 8 and has respective faces that are parallel to the axis A and extend around the latter.

The section 35 is preferably made of a material having a high magnetic flux conveying ability, such as for example a ferrous material with low carbon content. When the coil 33 of the electromagnet 1 is flown through by an electric current, it generates a magnetic field, which is amplified by the core 32. Said magnetic field determines, in a known manner, a magnetic force on the anchor 10, which is substantially oriented parallel to the axis A.

In particular, the application points of the magnetic force and of the returning force of the spring 25 on the plate 20 of the anchor 10 are distinct from one another and are both spaced apart from the axis B. Therefore, the spring 25 and the circulation of current in the coil 33 generate two opposite rotation torques on the plate 20 of the anchor 10. The electromagnet 11 is powered by the control unit so as to generate a rotation torque on the plate 20 of the anchor 10, which has an opposite direction and a greater modulus compared to the rotation torque generated by the spring 25 on the plate 20.

The resultant of the aforesaid torques determines the rotation of the anchor 10 around the axis B, in particular shown in figures 3 and 4 in a counterclockwise direction. At the end of this rotation, the anchor 10 is arranged in the second opening operative configuration (figure 4), in which it keeps the shutter disc 23 detached from the opening 16 of the outlet mouth 8, so as to allow the fuel entering the casing 6 through the inlet mouth 7 to flow into the outlet mouth 8 and, from there, towards the cylinder 5. By so doing, the outlet mouth 8 and the inlet mouth 7 are fluidically connected to one another and the fuel can cross the casing 6, the outlet mouth 8, the outlet pipe 13 and reach the cylinder 5 of the engine.

As you can clearly see in figures 1 to 4, the spring 25 has an axial pre-load that can be adjusted so as to vary the magnetic force needed to the move the plate 20 of the anchor

10 from the first closing operative configuration to the second opening operative configuration; by so doing, another aspect turns out to be variable, which is the time needed to move the plate 20 back from the second opening operative configuration to the first closing operative configuration, once the control unit has stopped powering the electromagnet

11 by means of the electric terminals.

More in particular (figures 3and 4), the end 26 of the spring 25 cooperates with a screw adjustment element 34, which is coupled in a cavity 34a of the casing 6. In particular, the adjustment element 34 and the cavity 34a are coaxial to one another and coaxial to the spring 25.

The adjustment element 34 engages, with an outer thread of its own, a corresponding thread obtained in the cavity 34a.

The adjustment element 34 has an axial end opposite to the end 26 of the spring 25, which is adapted to be engaged, in use, by a suitable wrench, so as to vary the relative axial position between the threads of the adjustment element 34 and of the cavity 34a and, consequently, the axial pre ^¬ load of the spring 25.

Advantageously, the injector 1 further comprises:

- a magnetic flux conveying element 38, preferably plate-shaped, which is arranged inside the compartment 18 in a position interposed between the electromagnet 11 and the anchor 10 and is separated from the core 32 by an air gap; and

- a spacer 39 interposed between the side portion 24 of the anchor 10 and the magnetic flux conveying element 38, so as to maintain an air gap between them with the exception of the action area of the spacer 39 itself.

In particular, as you can see in figure 4, the magnetic flux conveying element 38 substantially extends parallel to the anchor 10 in the second opening operative configuration.

The anchor 10 (figures 2 to 8) further comprises a preferably tubular shank 40, which projects towards the core 32 through a through opening 41 of the magnetic flux conveying element 38 and is held, by the pin 31, by the spacer 39 and by the magnetic flux conveying element 38, in a position facing the core 32 and separated from the latter by an air gap in the operative configuration of the anchor 10.

Basically, the spacer 39 and the pin 31 define, as a whole, positioning means for the anchor 10 inside the casing 6, which are configured to keep, in the second operative configuration of the anchor 10, the portion thereof directly facing the core 32, namely the shank 40, separated from the aforesaid core 32 by an air gap

As you can see in figures 3 and 4, the pin 31 engages a through opening 31a of the magnetic flux conveying element 38 and has a size in a direction parallel to the axis A, namely a diameter, that is greater than the thickness of the magnetic flux conveying element 38 in a direction parallel to the axis A. This feature, together with the presence of the spacer 39, allows a predetermined air gap to be maintained between the anchor 10 and the magnetic flux conveying element 38 in the second operative configuration of the anchor 10.

The magnetic flux conveying element 38 is preferably made of a ferrous material with low carbon content.

In the example shown, the magnetic flux conveying element 38 rests on the free end edge of the side wall 37 of the section 35, opposite to the bottom wall 36; the side wall 37 advantageously has a height, in a direction parallel to the axis A, that is greater than the height, in the same direction, of the core 32, so as to ensure the presence of an air gap between the core 32 and the magnetic flux conveying element 38. In the embodiment shown in figures 3 to 6, the spacer 39 consists of a projection 42, which is carried by the plate and protrudes from the surface 21 towards the magnetic flux conveying element 38. Preferably, the projection 48 is made as one single piece, hence of an elastomer material, together with the shutter disc 23, to which it is connected by means of a joining strip 43 extending around the end corner of the plate 20 delimiting the side portion 24. The projection 42 has a prismatic shape.

The variant of figure 7 shows a spacer 39 similar to the spacer 39 of figures 3 to 6, but different from the latter because of the sole fact that the prismatic projection 42 is replaced by two raised discs 44 besides one another and joined together, so that there is no joining strip between the shutter disc 23 and the discs 44 themselves.

The variant of figure 8 shows a spacer 39 with a concept different from the ones of figures 3 to 7; in this case, the spacer 39 is carried by the magnetic flux conveying element 38 and preferably consists of a cylindrical bar 45, in particular made of an elastomer material, which is housed in cavity 46 of the magnetic flux conveying element 38 itself, extends parallely to the pin 31 and to the bar 28 and projects towards the anchor 10.

As you can see in figure 1, the injector 1, in use, is fitted and positioned inside the engine compartment (not shown) of the automotive vehicle exclusively through the coupling between the inlet and outlet mouths 7, 8 and the relative inlet 12 and outlet pipes 13, both made of a flexible material, so as to be easily bent according to a desired bend radius.

In use, the liquefied gas contained in the tank 3 flows through the pressure reduction device 4, where it is decompressed until it reaches the gaseous state.

The fuel gas, through the inlet pipe 12, reaches the inlet mouth 7 of the injector 1, which selectively permits or forbids the flow of the fuel gas through the outlet pipe 13 and the consequent injection into the cylinder 5.

The operation of the injector 1 is described below starting from a condition in which the anchor 10 is in the first closing operative configuration (figure 3) .

In this first operative configuration, the shutter disc 23 engages the opening 16 of the outlet mouth 8 in a gas- tight manner, thus preventing the gas led by the inlet pipe 12 into the casing 6 from flowing through the outlet pipe 13 and from reaching the cylinder 5.

The anchor 10 is loaded towards the first closing operative configuration of the spring 25 and of the bar 28, which act upon the side portion 30 of the plate 20.

Due to the action of an external control, for example the lowering of a pedal, the anchor 10 moves from the first closing operative configuration to the second opening operative configuration (figure 4) .

More in detail, following the external control, the control unit powers the electric terminals and supplies the coil 33 with an electric current.

The electric current flowing through the coil 33 determines a magnetic field, whose intensity is amplified by the core 32.

The actions of the spring 25 and of the magnetic field of the coil 33 have application points on the plate 20 of the anchor 10 that are spaced apart from one another and spaced apart from the axis B.

Therefore, the plate 20 is subjected to two rotation torques around the axis B, one generated by the spring 25 and the other one generated by the coil 33, which, because of the current flowing through the coil 33, have a different modulus and opposite directions.

The resultant of the these torques determines the rotation of the anchor 10 around the axis B against the action of the spring 25 and in a counterclockwise direction.

The spring 25 is compressed and the shutter disc 23 disengages (figure 4) the opening 16, thus establishing a fluidic connection between the inlet mouth 7 and the outlet mouth 8.

Thus, the fuel gas contained inside the casing 6 can flow through the opening 16, the outlet mouth 8 and the outlet pipe 13 and be injected into the cylinder 15.

It should be pointed out that the magnetic flux generated by the electric current circulating in the coil 33 spreads through the core 32, the magnetic flux conveying element 38, the section 35 and the shank 40, so as to finally exert an attraction action upon the anchor 10.

When the control signal is deactivated, the control unit interrupts the circulation of electric current inside the coil 33 and, therefore, there is no more magnetic force acting upon the anchor 10.

Consequently, the anchor 10 moves back from the second opening operative configuration to the first closing operative configuration.

More in detail, the spring 25 stretches, thus determining the rotation, in a clockwise direction, of the anchor 10 around the axis B. This rotation stops when the shutter disc 23 strikes, in a gas-tight manner, against the opening 16 of the outlet mouth 8, thus preventing the delivery of the fuel gas to the outlet pipe 13 and to the cylinder 5.

The magnetic force needed to overcome the action of the spring 25 and the time needed to move the anchor 10 back from the second opening operative configuration to the first closing operative configuration are selectively varied by acting, with a suitable wrench, upon the screw 34, so as to change the pre-load of the spring 25.

More precisely, by acting upon the screw 34, you can change the relative axial position between the threads of the screw 34 and of the cavity 34a and, consequently, the pre-load of the spring 25.

The injector 1 according to the invention leads to evident advantages that can be obtained using it.

In particular, the injector 1 ensures the presence of an air gap between the anchor 10 and the core 32 in the second opening operative configuration. In the presence of oils or other impurities in the gas fuel, this allows manufacturers to avoid any adhesion between the anchor 10 and the core 32 and, as a consequence, possible delays in the closing of the anchor 10.

Therefore, the injector 1 is characterized by very precise delivery times, regardless of the type of gas fuel used .

Furthermore, the presence of the magnetic flux conveying element 38, which is also separated from the core 32 and from the anchor 10 by respective air gaps, allows manufacturers to increase the attractive action of the magnetic field exerted upon the anchor 10 by the activation of the coil 33; this increase makes up for the probable reduction in the magnetic force of attraction exerted upon the anchor 10, due to the air gap between the latter and the core 32.

Finally, the injector 1 described herein can be subjected to changes and variants, which do not go beyond the scope of protection set forth in the appended claims.