EP1963665A1

EP1963665A1 - Fuel injector for an internal combustion engine

Info

Publication number: EP1963665A1
Application number: EP06842058A
Authority: EP
Inventors: Nadim Malek; André AGNERAY
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2005-12-19
Filing date: 2006-11-29
Publication date: 2008-09-03
Anticipated expiration: 2026-11-29
Also published as: ATE507391T1; US20090014554A1; DE602006021621D1; FR2895031A1; EP1963665B1; WO2007071863A1; FR2895031B1; US8038080B2; JP2009520153A

Abstract

A fuel injector for an internal combustion engine, particularly of inwards or outwards opening needle injector type, includes an injector body, e.g., forming a nozzle ending in an injection office, a mechanism for closing off the injection orifice of the injector body, the closing-off mechanism including a vibrating pintle ending in a head for closing off the injection orifice, a return mechanism returning the closing-off to the position in which they close off the injection orifice, and a mechanism for setting the pintle and/or the nozzle into cyclic longitudinal vibration so as to open and close the injection orifice alternately. The fuel injector includes a selectively activatable mechanism immobilizing the pintle with respect to the body.

Description

Fuel injector for internal combustion engine

The present invention relates to a fuel injector for an internal combustion engine, in particular Diesel intended in particular to be implemented in a motor vehicle

A conventional internal combustion engine comprises at least one cylinder in which a piston slides between two extreme positions. The piston delimits with the cylinder and a cylinder head a combustion chamber. In such an internal combustion engine, an injector serves to supply fuel. finely atomized to the combustion chamber of the internal combustion engine

Patent FR 2 801 346 in the name of the applicant, for example, discloses an injection device for an internal combustion engine comprising a fuel injector 10 as represented in FIG.

This injector 10 comprises a body 12 comprising a transducer 14 capable of generating vibrations in a longitudinal mode at ultrasonic frequencies. The transducer 14 ends in the lower part by a nozzle 16 in which the vibrations coming from the transducer 14 are amplified.

The entire transducer 14 has a first internal cavity 18 The first internal cavity 18 is intended to be filled with pressurized fuel To do this, the first cavity 18 is connected to a fuel supply port 20 adapted to be put into operation. communication with a fuel supply circuit under pressure (not shown) The first cavity 18 opens at the lower end 22 of the nozzle 16, also called the nose of the injector, through an injection port

The injector 10 also comprises a rod 24, or needle, extending mainly along the axis yy 'The rod 24 is housed axially movable inside the nozzle 16 The lower end of the needle 24 has a head shutter 26 extending outside the nozzle 16 This closure head 26 is adapted to come into contact with the inner surface of the nozzle 16 defining the injection orifice of the nozzle 16 so as to close the fuel injection port

The other end of the rod is provided with a mass 28 elastically connected by a spring 30 to the body 12 of the injector 10 The system 32 consisting of the mass 28 and the spring 30 is housed in a second cavity 34 formed in the rear part of the body 12 of the injector 10

The stem assembly 24 and elastic spring 30, exerts a desired elastic return force for applying the closure head 26 of the rod 24 to the zone of the nozzle 16 surrounding the injection orifice The applied preload allows on the one hand the sealing of the injection orifice formed at the end of the nozzle 16 when the injector 10 is supplied with fuel with a given pressure and secondly the catch of possible wear in the contact zone of the closure head 26 of the rod 24 with the nozzle 16

The mass 28 is fixed, for example, by screwing on the rod 24 so as to achieve a mechanical impedance break at the interface between the rod 24 and the mass 28.

The value of the mass 28 and the rigidity of the spring 30 are chosen to form a system having a very large response time with respect to the excitation times of the transducer 14.

The transducer 14 comprises an area consisting of a stack 36 of piezoelectric or magnetostrictive active components, which, respectively under the application of an electric or magnetic field, deform in thickness. This stack 36 is clamped between two other elements 37a, 37b made of an elastic material The connection between the active components is provided by prestressing means such as a nut 38. The stack of several active components allows adding the thickness deformations generated by each of the active components, the deformation resulting from the total displacement of the stack of active components remaining below the elastic deformation limit of the prestressing means.

Under the application of a voltage on the piezoelectric active elements, these deform and generate an elastic deformation which is transmitted to the lower end of the nozzle 16.

Preferably, the assembly 40 composed of the transducer 14 and the nozzle 16 is sized to resonate with the excitation frequency of the active components to amplify the longitudinal displacements up to the level of the lower end 22 of the nozzle 16. rod 24, initially closing the injection port by means of its closure head 26, deforms under the pulse that is provided when the nozzle 16 begins to oscillate. This deformation is distributed elastically over the entire length of the rod 24 and is reflected at the interface 42 between the rod 24 and the mass 28.

The proper responses of the rod 24 on the one hand and the nozzle 16 on the other hand make it possible to oscillate the end of the rod 24 and the opening with a variation of phase and amplitude. This variation results in the opening of a slot annular between the rod 24 and the end 22 of the nozzle 16, the width of the slot depending on the phase shift and the relative amplitude difference between the oscillation of the end 22 of the nozzle 16 and the oscillation of the shutter head 26 of the rod 24

The minimum opening time of the injector 10 is of the same order as the excitation period applied to the transducer which excitation can be done at a few tens of kilohertz typically 50 kHz, which allows a minimum opening time of the order of 20 μs This allows to deliver quantities of fuel of the order of one microliter for a short period of time

The body 12 of the injector 10 is intended to be fixed to the upper end of the engine cylinder head by non-representative means

While the injector 10 has indirect means for vibrating the stem longitudinally, injectors comprising direct means for cyclically vibrating the rod are also known. An injector comprising a stack of piezoelectric ceramics or an magnetostrictive rod mounted directly in the body of the rod and which excites the rod so as to generate elastic deformations of the rod

In the two cases of excitation, direct or indirect, of the rod of the injector, the rod is embedded at one end in a mass The role of this mass is to realize a break of impedance so that the waves of deformation propagating in the rod are reflected at the border between the rod and the mass

On the other hand, while the injector 10 is of the outgoing needle type, it is also known of the injectors of the incoming needle type In the case of an injector of the incoming needle type, the rod is plated, at rest, on the inner face of the lower end of the nozzle under the effect of a spring The spring is mounted in the second cavity is thus ensured sealing of the injection port When the body of the injector is excited, the rod is placed in longitudinal vibration The end of the rod then oscillates between its closed position of the injection orifice and an open position of this injection orifice

It should be noted that depending on the type of the injector, the spring exerts on the rod either a pulling force (in the case of an outgoing needle type injector) or a compressive force (in the case of an injector of the incoming needle type)

However, the dimensions of the injector are imposed by the space available on the engine and in the direct environment of the engine Thus, the volume of the injector being imposed, the bulk of the mass + spring system ensuring an impedance break sufficient and a satisfactory sealing force at the level of the injection orifice may correspond to a spring of a stiffness such that the spring mass system has a resonant frequency lying in the excitation range imposed by the vibrations of the motor. its resonant frequency causes an opening of the injector in a chaotic manner

A known solution to this problem is to add damping means to the system mass + spring However, this solution only partially solves the problem of the resonance of the system mass + spring, such a measure only allowing to reduce the amplitude oscillations of the mass + spring system excited at its resonant frequency

It is also known to fix, on the body of the injector, the mass in which the needle is embedded. However, such a solution has the disadvantage that, due to heating of the injector and therefore the expansion of the body of the injector and the needle, uncontrolled axial forces appear in the needle. These axial forces disturb the cyclic deformation of the needle and therefore the injection by the injector

The object of the invention is to provide a fuel injector not having the aforementioned defects and suitable, in particular, to ensure a fuel injection in the form of fine droplets better controlled relative to the constraints of the environment of the injector.

This object of the invention is achieved by means of a fuel injector for an internal combustion engine, particularly of the incoming needle type or of the outgoing needle type, comprising

an injector body forming in particular a nozzle terminated by an injection orifice,

means for closing said injection orifice of said injector body, said sealing means comprising a vibrating rod terminating in a closure head of said injection orifice,

means for returning said closure means to the closed position of said injection orifice, and

cyclic longitudinal vibration means of said rod and / or of said nozzle so as to alternately open and close the injection orifice,

According to the invention, said injector comprises selectively activatable locking means of said rod relative to said body. Thus, as will be seen in more detail in the following description, when the locking means of the rod relative to the body of the injector are activated, the rod does not oscillate and, therefore, any risk of resonance of the rod at vibration frequencies of the motor is spaced, which ensures the control of the injection To avoid problems related to the differential expansion of the rod and the body of the injector, the locking means of the rod can be disabled In this case, the return means of the closure means make it possible to reposition the closure means in a position where the stem is relieved of the stresses due to the differential expansion of the rod relative to the body

Preferably, said selectively activatable locking means of said rod are able to cooperate with said rod and / or with a mass to which said rod is fixed so as to achieve a mechanical impedance break

Preferably, said locking means comprise a piston capable of sliding in a direction substantially perpendicular to said rod

Preferably, the fuel injector according to the invention comprises a hydraulic chamber for controlling the movement of said piston.

Preferably, said hydraulic control chamber comprises at least one fuel inlet which is in fluid communication with a fuel supply orifice of said injector

Preferably, said hydraulic control chamber further comprises at least one fuel outlet orifice, the total section of said at least one inlet orifice being less than the total section of said at least one outlet orifice.

Preferably, the fuel injector according to the invention comprises means for controlling the filling or emptying of said hydraulic control chamber of the magnetostrictive or electromagnetic or electrostrictive or piezoelectric type.

Preferably, said means for cyclically vibrating said rod and / or said nozzle are of the piezoelectric and / or magnetostrictive and / or electromagnetic type.

Preferably, said means for cyclically vibrating said rod and / or said nozzle are able to cause elastic deformations of said rod and / or said nozzle at ultrasonic frequencies.

Preferably, said means for cyclically vibrating said rod and / or said nozzle are mounted integral with said body and / or said rod. Other advantages and characteristics of the invention will emerge on examining the description of the preferred embodiments which follow, which are only present as nonlimiting examples, with reference to the appended figures in which:

FIG. 1 represents a view in longitudinal section of an injector according to a first embodiment of the invention,

FIG. 2 represents a sectional view along the sectional plane A-A of the injector of FIG. 1;

FIG. 3 represents a view in longitudinal section of an injector according to a second embodiment of the invention,

FIG. 4 represents a view in longitudinal section of an injector according to a third embodiment of the invention,

FIG. 5 represents a view in longitudinal section of an injector according to a fourth embodiment of the invention, and

FIG. 6 represents a view in longitudinal section of an injector according to the state of the art

In the figures, elements that are identical or have the same function are indicated with the same numerical reference

A first embodiment of the injector 44 according to the invention is shown in longitudinal section in FIG.

The elements of the injector 44 according to the first embodiment of the invention identical to the elements of the injector of the state of the art described above with reference to FIG. 6 are not described again below.

According to the invention, the injector 44 comprises means for blocking the mass 28 relative to the body 12 which are selectively activatable

These locking means comprise a piston 46 mounted free in translation relative to the body 12 of the injector 44 along an axis xx 'substantially perpendicular to the axis yy' of the rod 24. The locking means also comprise a support piece 48 adapted to cooperate with the piston 46 so as to block the mass 28 in translation along the axis yy '

Preferably, the piston 46 and / or the support piece 48 have a bearing face on the mass 28 of shape complementary to the mass 28. Thus, the mass 28 being, in this case, cylindrical, the piston 46 and the support piece 48 has a bearing face adapted to cooperate with the mass 28 of concave shape, substantially Thus, advantageously, the locking force exerted by the locking means is optimized for a given pressure.

Preferably, the support piece 48 is made of hard steel

Also preferably, the piston 46 and the support piece 48 are substantially of the same height as the mass 28 so as to ensure a contact surface between the piston, the mass and the largest possible support piece Thus, advantageously, the locking force exerted by the locking means is optimized for a given pressure

In order to control the translation of the piston 46, the injector 44 according to the first embodiment of the invention has a hydraulic control chamber 50 This hydraulic control chamber 50 is delimited on the one hand by the body 12 of the injector 44 and secondly by the piston 46 The hydraulic control chamber 50 has a fuel inlet port 52 A fuel bypass conduit 53 opens through this fuel inlet port 52 The bypass conduit 53 opens on the other hand in the supply duct 54 of the injector 44, preferably between the supply orifice 20 and the first cavity 18

The hydraulic control chamber 50 furthermore has a hydraulic fluid outlet orifice 56 whose section is, preferably, greater than the section of the inlet orifice 52. This outlet orifice 56 is connected to the second cavity 34. The second cavity 34 is closed by a plug 58 This plug 58 has a low pressure fuel outlet pipe 60

Moreover, so as to control the filling or emptying of the hydraulic control chamber 50, the injector 44 according to the first embodiment of the invention comprises a valve 62 in this case of the electric control type, preferably of the magnetostrictive, electromagnetic or electrostrictive type This valve 62 is able to cut off the fluid communication between the hydraulic control chamber 50 and the second cavity 34

The operation and advantages of the fuel injector 44 according to the first embodiment of the invention flow directly from the description which has just been made thereof.

When the pressurized fuel enters the body 12 of the injector 44 through the supply port 20, it propagates in the first cavity 18 and in the hydraulic control chamber 50 When the valve 62 is not electrically powered, it is closed and the fluid communication between the second cavity 34 and the hydraulic control chamber 50 is interrupted. The fuel is therefore exhausted to the second cavity 34 The fuel pressure in the hydraulic control chamber 50 remains high, that is to say greater than the fuel pressure in the second cavity 34 That is why the fuel pushes the piston 46 along the axis xx 'in the direction of the mass 28 Thus, the piston 46 maintains the mass 28 in its initial position by pressing the mass 28 against the bearing piece 48 This initial position of the mass 28 and the initial tension in the rod 24 are obtained by construction, particularly at the means of the spring 30 disposed in the second cavity 34

When the valve 62 is electrically powered, it opens The fuel is then discharged to the second cavity 34 The pressure in the hydraulic control chamber 50 then drops and the piston 46 reduces its grip The mass 28 is released and the voltage in the rod 24 takes the value that the spring 30 imposes on him

This command to open the valve 62 is done periodically (for example every minute) and for very short periods, of the order of a few hundred milliseconds to allow the voltage in the rod 24 to return to the imposed value. by the spring 30, and to eliminate overvoltages which may appear in the rod 24 because of the differential expansions between the body 12 of the injector 44 and the rod 24 The opening of this valve 62 may, for example, be realized between two successive injections

It should be noted that the fuel that is always supplied under pressure by a pump, continues to exert pressure on the piston 46 So, despite the opening of the valve 62, the fuel may tend to maintain pressure in the chamber hydraulic control 50, greater than the pressure in the second cavity 34 This problem is solved by the fact that the arrival of the fuel in the hydraulic control chamber 50 is via a bypass conduit 53 end, and that the evacuation of the fuel from the hydraulic control chamber 50 is achieved by means of a discharge orifice 56 and a discharge duct 60 of larger diameter than the diameter of the bypass duct 53. The discharge of the fuel from the control chamber 50 is less than the pressure drop at the filling of this control chamber 50. It is thus possible to promote the evacuation of the fuel from the control chamber 5. 0 so as to decrease, very quickly, the fuel pressure in the control chamber 50 The valve 62 preferably offers a small pressure drop so that the pressure in the hydraulic control chamber 48 drops rapidly. The bypass duct 53 is sufficiently resistant to the rise in pressure in the hydraulic control chamber 50. the hydraulic control chamber 50 does not have time to rise to oppose the release of the mass 28

When the valve 62 is no longer powered, it closes so as to block the fluid communication between the hydraulic control chamber 50 and the second cavity 34. The pressure in the hydraulic control chamber 50 then increases. The piston 46 is then pressed against the mass 28 against the support piece 48 so as to block the mass 28, as shown in FIG. 2 Immediately after locking, the force in the rod 24 is at the value that the spring 30 imposes, the rod 24 being rid of additional efforts that may have been created following differential expansions

FIG. 3 presents a second embodiment of the injector according to the invention. The injector 66 shown in FIG. 3 differs from the injector 44 according to the first embodiment of the invention in that it is an injector of the incoming needle type. Thus, in order to close the injection orifice 68, the rod 24 is plated, at rest, on the inner face of the lower end 22 of the nozzle 16 under the effect of the spring 30 which is mounted in the second cavity 34

FIG. 4 presents a third embodiment of the injector according to the invention. The injector 70 shown in FIG. 4 differs from the injector 44 according to the first embodiment in that it does not have a stack 36 of active components, for example piezoelectric or magnetostrictive, mounted on the body of the 'injector. Indeed, a stack 72 of active components able to deform under the effect of an electric or magnetic field, preferably piezoelectric or magnetostrictive components, is mounted integral on the rod 24 so that the deformation of this stack 72 of active components directly causes the longitudinal vibration of the rod 24

FIG. 5 presents a fourth embodiment of the injector according to the invention. The injector 74 shown in FIG. 5 differs from the injector 66 according to the second embodiment in that it does not have a stack 36 of active components, for example piezoelectric or magnetostrictive, mounted on the body of the 'injector. Indeed, as has been described for the injector 70 according to the third embodiment, a stack 72 of active components capable of deform under the effect of an electric current, for example piezoelectric or magnetostrictive elements, is mounted integral on the rod 24 so that the deformation of this stack 72 of active components directly causes the longitudinal vibration of the rod 24

Naturally, the present invention is not limited to the embodiments described above by way of illustrative and non-limiting examples and many modifications are possible without departing from the scope of the invention.

Thus, the locking piston and the support piece can cooperate directly with the rod, the mass then possibly being removed.

Moreover, although the piston device 46 and support piece 48 has an advantageous embodiment of selectively activatable locking means, these elements can be replaced by any selectively activatable device that effectively makes it possible to block the mass and / or or rod One can cite, by way of examples, an electric or hydraulic cylinder or a lock by electromagnet

Claims

1 Fuel injector (44, 66, 70, 74) for an internal combustion engine, especially of the incoming needle type or the outgoing needle type, comprising

a mjector body (12) forming in particular a nozzle (16) terminated by an injection orifice,

means for closing said injection orifice of said injector body, said sealing means comprising a vibrating rod (24) terminated by a closing head (26) of said injection orifice,

- return means (30) of said closure means in the closed position of said injection port, and

means (36, 72) for cyclically longitudinal vibration of said rod (24) and / or said nozzle (16) so as to alternately open and close the injection orifice, characterized in that said injector ( 44, 66 70 74) comprises selectively activatable locking means (46, 48) of said rod (24) relative to said body (12).

2 fuel injector according to claim 1, characterized in that said selectively activatable locking means of said rod are adapted to cooperate with said rod (24) and / or with a mass (28) to which said rod (24) is fixed in order to achieve a mechanical impedance break

3 fuel injector according to one of claims 1 and 2, characterized in that said locking means (46, 48) comprise a piston (46) slidable in a direction substantially perpendicular to said rod (24)

4 fuel injector according to claim 3, characterized in that it comprises a hydraulic chamber (50) for controlling the movement of said piston (46)

A fuel injector according to claim 4, characterized in that said hydraulic control chamber (50) has at least one fuel inlet (52) which is in fluid communication with a supply port (20). fuel of said injector (44, 66, 70, 74) The fuel injector according to claim 5, characterized in that said hydraulic control chamber (50) further comprises at least one fuel outlet (56), the total section of said at least one inlet port (52). being less than the total section of said at least one outlet (56)

7 fuel injector according to one of claims 5 and 6, characterized in that it comprises means (62) for controlling the filling or emptying of said hydraulic control chamber (50) of the magnetostrictive or electromagnetic or electrostrictive or piezoelectric type

Injector according to any one of the preceding claims, characterized in that said means for cyclically vibrating said rod (24) and / or said nozzle (16) are of the piezoelectric and / or magnetostrictive and / or electromagnetic type.

Injector according to any one of the preceding claims characterized in that said means for cyclically vibrating said rod (24) and / or said nozzle (16) are able to cause elastic deformations of said rod (24) and / or said nozzle (16) at ultrasonic frequencies

Injector according to any one of the preceding claims, characterized in that said means for cyclically vibrating said rod (24) and / or said nozzle are mounted integral with said body (12) and / or said rod (24).