EP3059436A1

EP3059436A1 - Fluid injector with a spring chamber

Info

Publication number: EP3059436A1
Application number: EP15155611.5A
Authority: EP
Inventors: Stefano Filippi; Mauro Grandi; Francesco Lenzi; Valerio Polidori
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive GmbH
Priority date: 2015-02-18
Filing date: 2015-02-18
Publication date: 2016-08-24

Abstract

Injector (1) for injecting fluid with an injector body (3), a valve assembly (5) comprising a valve body (9) and a valve needle (11), the valve body (9) having a longitudinal axis (13) and comprising a cavity (15) with a valve seat (17), an electromagnetic actuator assembly (7) comprising an armature (21), a spring chamber (27) located in the cavity (15), being fluid-tightly insulated from an exterior of the spring chamber (27), and a calibration spring (29) for axially biasing the valve needle (11) away from the closing position, being received in the spring chamber (27), being mechanically coupled to the valve needle (11) to bias the valve needle (11) with a first axial end (33) and being fixedly coupled to the injector body (3) with a second axial end (35) such that a position of the second axial end (35) is independent of pressure of fluid in the cavity (15).

Description

The invention relates to an injector for injecting fluid and relates particularly to an injector for injecting fuel into an internal combustion engine.
Fluid injectors are in widespread use, in particular for internal combustion engines where they may be arranged in order to dose the fluid into an intake manifold of the internal combustion engine or directly into the combustion chamber of a cylinder of the internal combustion engine.
Fluid injectors are manufactured in various forms in order to satisfy the various needs for the various combustion engines. Therefore, for example, their length, diameter as well as various elements of the injection valve which are responsible for the way the fluid is dosed, may vary within a wide range. In addition to that, fluid injectors may accommodate an actuator for actuating a valve needle which may, for example be an electromagnetic actuator.
In order to enhance the combustion process with regard to the reduction of unwanted emissions, fluids have to be dosed under very high pressure. The pressure may be, for example in the case of a gasoline engine, in the range of up to 400 bar, and in the case of diesel engines in the range of up to 3,500 bar.
One object of the invention is to create an injector for injecting fluid that contributes to a precise and reliable injection of the fluid independent of its fluid pressure or at least particularly insensitive to the fluid pressure.
The object is achieved an injector having the features of the independent claim. Further embodiments of the injector are given in the dependent claims.
According to one aspect of the invention, an injector for injecting fluid has an injector body and a valve assembly comprising a valve body and a valve needle. The valve body has a longitudinal axis and comprises a cavity with a valve seat.
The cavity is operable to take in the valve needle. In other words, the valve needle is received in the cavity. The valve needle is in particular axially displaceable in reciprocating fashion relative to the cavity. The cavity and the valve needle are operable to prevent an injection of fluid from the cavity to external to the injector in a closing position of the valve needle, in which the valve needle is seated on the valve seat. Moreover, the cavity and the valve needle are operable to enable the injection of fluid when the valve needle is apart from the closing position. In other words, the valve body and the valve needle interact mechanically for prevent fluid flow out of the cavity in the closing position of the valve needle and to enable fluid flow from the cavity for dispensing of fluid from the injector in further positions of the valve needle in which further positions the valve needle is spaced apart from the valve seat.
The injector further comprises an electromagnetic actuator assembly which is operable to exert a force for influencing a position of the valve needle. In particular, the actuator assembly is operable to displace the valve needle axially away from the closing position. The electromagnetic actuator assembly comprises an armature being received in the cavity and mechanically coupleable, in particular coupled, to the valve needle. The armature is in particular axially displaceable in reciprocating fashion relative to the valve body. In one embodiment, the armature is fixed to the valve needle. In another embodiment, the armature has an axial play with respect to the valve needle and is operable to engage in a form-fit connection with the valve needle for displacing the latter away from the closing position.
The injector further comprises a spring chamber located in the cavity. The spring chamber is fluid-tightly insulated from an exterior of the spring chamber. In other words, the spring chamber is hydraulically separated from the fluid which is arranged in the cavity in operation of the injector. In one embodiment, the spring chamber is filled with a gas such as air.
The injector further comprises a calibration spring for axially biasing the valve needle away from the closing position. The calibration spring is received in the spring chamber. Preferably, the calibration spring is positioned within the spring chamber in its entirety.
The calibration spring is mechanically coupled to the valve needle to bias the valve needle with a first axial end. The calibration spring is further fixedly coupled to the injector body with a second axial end, in particular such that a position of the second axial end is independent of fluid pressure of fluid in the cavity. In other words, during operation of the injector, the second axial end of the calibration spring is positionally fix relative to the valve body and the first axial end of the calibration spring is axially displaceable relative to the valve body.
A first accumulated area comprises respective surfaces of components of the injector, being in contact with fluid in the cavity, being axially movable together with the valve needle and facing towards the valve seat.
A second accumulated area comprises respective surfaces of components of the injector, being in contact with fluid in the cavity, being axially movable together with the valve needle and facing away from the valve seat.
Advantageously, the spring chamber enables the first accumulated area and the second accumulated area to be substantially equal such that when being subjected to force dependent on fluid pressure of fluid in the cavity, the valve needle is kept substantially steady. Particularly, respective forces subjected to the first accumulated area and the second accumulated area substantially compensate each other. In other words, the spring chamber contributes to a hydraulically effective area to be small in a way that the injector is substantially pressure balanced.
In this regard, the spring chamber contributes to a pressure balanced movement of the valve needle. In particular, if the injector is of an outward opening type, the spring chamber contributes to a prevention of unwanted injection of fluid due to fluid pressure, i.e. to a prevention of unwanted displacement of the valve needle away from the closing position due to the fluid pressure.
In one embodiment, a front end of the valve needle, facing away from the valve seat, is insulated from fluid due to the spring chamber such that the front end of the valve needle is substantially free of being subjected to a force dependent on fluid pressure. The front end of the valve needle is in particular that axial end of the valve needle which is remote from the axial end of the valve needle that comprises a sealing element of the valve needle. The sealing element comprises a sealing surface which is in sealing mechanical contact with the valve seat in the closing position of the valve needle.
Additionally or alternatively, a front surface of a coupling element for mechanically coupling the first axial end of a calibration spring to the valve needle, facing away from the valve seat, is insulated from fluid such that the front surface of the coupling element is free of being subjected to a force dependent on fluid pressure.
In one embodiment, the calibration spring is mechanically coupled to the valve needle such that their mechanical coupling exists independent of the fluid pressure.
In one embodiment, the calibration spring is concentrically arranged to the valve needle with respect to the longitudinal axis.
In one embodiment, the spring chamber is axially deformable. In one embodiment, the spring chamber is laterally limited by a chamber unit. The chamber unit comprises a bellow. Advantageously, the chamber unit enables the spring chamber to be fluid-tightly insulated. In particular, the bellow contributes to an axial deformability of the spring chamber in this context.
The chamber unit may further comprise a rigid element for reliably coupling the chamber unit to the injector body. In one embodiment, the bellow is made of metal. In one embodiment, the chamber unit is pressure-proof with respect to the fluid pressure, for example at least up to 300 bar, preferably at least up to 500 bar. According to a further embodiment, a wall of the cavity and the chamber unit form a channel, which allows for an axial fluid communication from a fluid inlet end of the valve body to a fluid outlet end of the valve body where the valve seat is positioned. In this way, the fluid can expediently pass the spring chamber in axial direction on its way through the cavity. Advantageously, such a configuration enables a variable position of a fluid inlet of the injector and thus contributes to its cheap manufacturing.
According to a further embodiment, the chamber unit is fixedly coupled to the armature. Advantageously, this enables the spring chamber to be reliably insulated from fluid during operation of the injector. In one embodiment, the chamber unit is welded to the armature, for example with an axial end of the bellow which faces towards the valve seat.
According to a further embodiment, the spring chamber is axially limited by the armature. Advantageously, this enables the spring chamber to be fluid-tightly insulated without a further element. This contributes to the cheap manufacturing of the injector.
According to a further embodiment, the injector comprises an adjustment pin for adjusting a position of the second axial end. The adjustment pin is fixedly coupled to the injector body, wherein the spring chamber is axially limited by the adjustment pin.
Advantageously, by adjusting the position of the second axial end, the adjustment pin allows for adjusting a bias of the calibration spring, hence contributing to an easy and precise adjustment of the injector. For example, the adjustment pin comprises a thread and a screw for biasing the calibration spring. Moreover, this enables the spring chamber to be fluid-tightly insulated without a further element, hence contributing to the cheap manufacturing of the injector.
According to a further embodiment, the chamber unit is fixedly coupled to the adjustment pin. Advantageously, this enables the spring chamber to be fluid-tightly insulated without a further element, hence contributing to the cheap manufacturing of the injector.
According to a further embodiment, the injector comprises a first O-ring, sealing a radial gap between the adjustment pin and the chamber unit. Advantageously, the first O-ring enables the spring chamber to be fluid-tightly insulated. In particular, the first O-ring contributes to a reliable prevention of fluid creeping between the chamber unit and the adjustment pin into the spring chamber. In one embodiment, the first O-ring is made of elastomer.
According to a further embodiment, the injector comprises a second O-ring, sealing a radial gap between the armature and the valve needle. Advantageously, the second O-ring contributes to a fluid tightness of a mechanical coupling of the valve needle and the armature. In particular, the second O-ring contributes to a reliable prevention of fluid creeping between the valve needle and the armature, which could cause the front end of the valve needle facing away from the valve seat to be subjected to a hydraulic force of the fluid pressure. In one embodiment, the second O-ring is made of elastomer.
According to a further embodiment, the armature has a recess, wherein the second O-ring is received in said recess. Advantageously, this contributes to the fluid tightness between the valve needle and the armature.
According to a further embodiment, the injector comprises a fluid inlet which is in particular co-axially arranged relative to the valve body and/or the valve needle with respect to the longitudinal axis. Advantageously, a co-axial arrangement of the fluid inlet contributes to the cheap manufacturing of the injector. In particular, a fluid terminal for providing fluid may be coupled to the fluid inlet of the injector by means of a further O-ring. In this context, a lateral force of fluid pressure may be used to reliably couple the injector to said fluid terminal in a cost-efficient manner.
Exemplary embodiments of the injector are explained in the following with the aid of schematic drawings and reference numbers. Identical reference numbers designate elements or components with identical functions.
In the figures:

Figure 1: shows an embodiment of an injector in a longitudinal section view, and
Figure 2: shows an enlarged longitudinal section view of the injector according to Figure 1.

Figure 1 shows one embodiment of an injector 1 for injecting fluid. In particular the injector 1 is a fuel injector for injecting fuel such as gasoline directly into a combustion chamber of an internal combustion engine.
The injector 1 has an injector body 3, a valve assembly 5 and an electromagnetic actuator assembly 7. The valve assembly 5 comprises a valve body 9 and a valve needle 11. The valve body 9 has a longitudinal axis 13 and comprises a cavity 15 with a valve seat 17.
The valve needle 11 is received in the cavity 15 and is axially movable relative to the valve body 9. The valve needle 11 is operable to prevent an injection of fluid in a closing position, in which the valve needle 11 is seated on the valve seat 17, from the cavity 15 external to the injector 1, in particular into the combustion chamber. The valve needle 11 is further operable to enable the injection of fluid when it is spaced apart from the closing position. The injector 1 may comprise a valve spring 19 for biasing the valve needle 11 towards the closing position, for example in order to contribute to a leak-tightness of the injector 1.
The electromagnetic actuator assembly 7 comprises an armature 21 and a magnetic coil 23, in particular a solenoid, the coil 23 being positioned in a housing 25. The magnetic coil 23, the housing 25, and the armature 21 form a magnetic circuit of the electromagnetic actuator assembly 7 when the magnetic coil 23 is energized.
The electromagnetic actuator assembly 7 is thus operable to exert a force for influencing a position of the valve needle 11. Particularly, the valve needle 11 may be axially displaced by the electromagnetic actuator assembly 7 relative to the valve body 9, away from the closing position.
The injector 1 further comprises a spring chamber 27 located in the cavity 15. The spring chamber 27 is fluid-tightly insulated from its exterior.
A calibration spring 29 for biasing the valve needle 11 away from the closing position is received within the spring chamber 27, for example in order to compensate a tolerance of manufacturing particularly with respect to the valve spring 19. An adjustment pin 31 received in the cavity 15 axially abuts the calibration spring 29, for example in order to allow for an adjustment of a bias of the calibration spring 29.
When the injector 1 is filled with pressurized fluid, a hydraulic force is applied on respective surfaces of components of the injector 1 which are in contact with the fluid. A first accumulated area comprises respective surfaces axially movable together with the valve needle 11 and facing towards the valve seat 17. That is, hydraulic force applied on the first accumulated area would cause the valve needle 11 to move away from the valve seat 17. A second accumulated area comprises respective surfaces axially movable together with the valve needle 11 and facing away from the valve seat 17. That is, hydraulic force applied on the second accumulated area would cause the valve needle 11 to move towards the valve seat 17.
Advantageously, the spring chamber 27 contributes to equalizing the first accumulated area and the second accumulated area such that hydraulic forces applied to the first accumulated area and the second accumulated area substantially compensate each other.
In the present embodiment, the injector 1 is of an outward opening type.
The spring chamber 27 particularly contributes to a pressure balance of the injector 1, which enables a wide operative range of fluid pressure of fluid in the cavity 15. The spring chamber 27 contributes in particular to a prevention of so called "self opening" at high fluid pressures. In addition, it allows using valve springs 19 of particularly small spring constants even for injectors 1 which are configured for operating at comparatively high fluid pressures such as 300 bar and above. In this way, operating at low pressure - as for example during a so called "limp home emergency function" - is made possible. The spring chamber 27 may contribute to a controllability of a minimum quantity of injected fluid.
Figure 2 shows an enlarged longitudinal section view of the injector according to figure 1, particularly of the spring chamber 27. The valve needle 11 is mechanically fixed to the armature 21. The armature 21 may comprise a bore for receiving the valve needle 11 with its front end facing away from the valve seat 17. For example, the valve needle 11 and the armature 21 are mechanically coupled by a press-fit connection.
The calibration spring 29 is mechanically coupled to the valve needle 11 to bias the valve needle 11 with a first axial end 33. In this embodiment, the first axial end 33 is seated on a front surface 34 of the armature 21 which is facing away from the valve seat 17.
The calibration spring 29 is further fixedly coupled to the injector body 3 with a second axial end 35. A position of the second axial end 35 is independent of fluid pressure of fluid in the cavity 15. In the present embodiment, the second axial end 35 is seated on the adjustment pin 31. The adjustment pin 31 particularly allows for an adjustment of the position of the second axial end 35 relative to the injector body 3 in order to bias the calibration spring 27. In this regard, the adjustment pin 31 is fixedly coupled to the injector body 3.
In order to fluid-tightly insulate the spring chamber 27, the spring chamber 27 may be axially limited by the adjustment pin 31 on an axial end of the spring chamber 27 facing away from the valve seat 17. In this context, the spring chamber 27 may additionally or alternatively be axially limited by the armature 21 on an axial end of the spring chamber 27 facing towards the valve seat 17.
Moreover, the spring chamber 27 is laterally limited by a chamber unit 37. The chamber unit 37 is fixedly coupled to the injector body 3, for example by means of a first laser weld 39. The chamber unit 37 is further fixedly coupled to the valve needle 11, for example by means of a second laser weld 41.
Particularly, the chamber unit 37 comprises a bellow 43 which allows for an axial deformability of the spring chamber 29 while maintaining its fluid-tightness. The bellow 43 is, for example, made of metal. The bellow 43 laterally surrounds the calibration spring 29. In particular, a spring constant of the bellow 43 is smaller than a spring constant of the calibration spring 29. For example it has a value of 20 % or less of the spring constant of the calibration spring 29.
The front surface 34 of the armature 21 is thus substantially free of fluid such that a movement of the valve needle 11 may be independent of fluid pressure of fluid within the cavity 15.
In the present embodiment, the injector 1 further comprises a first O-ring 45 surrounding the adjustment pin 31. The first O-ring 45 particularly seals a radial gap between the adjustment pin 31 and the chamber unit 37. In this context, the chamber unit 37 may further comprise a rigid element that, together with the first O-ring 45, contributes to a fluid-tightness of the spring chamber 27. In this embodiment, the rigid element is coupled to the injector body 3 with the first laser weld 39 and coupled to the bellow 43, for example by means of further welding.
In the present embodiment, the injector 1 further comprises a second O-ring 47 surrounding the valve needle 11. The second O-ring 47 particularly seals a radial gap between the valve needle 11 and the armature 21. The armature 21 may comprise a recess for receiving the second O-ring 47 in this context. The second O-ring 47 contributes to a prevention of fluid creeping between the valve needle 11 and the armature 21, particularly preventing it from contacting the front end of the valve needle 11. The front end of the valve needle 11 is thus substantially free of fluid such that a movement of the valve needle 11 may be independent of fluid pressure of fluid within the cavity 15. Moreover, a top surface 57 of the valve needle 11 within the bore of the armature 21 facing away from the valve seat 17, is free of fluid.
Particularly in the case of the injector 1 being of the outward opening type, a hydraulic surface of the valve needle 11 at its axial end opposite to the front end, facing towards the spring chamber 27 is high compared to a corresponding surface of an injector of an inward opening type. A hydraulic force applied on said hydraulic surface is compensated by a hydraulic force applied on the second O-ring 47 and/or the armature 21.
Similarly, hydraulic force applied on other hydraulic surfaces movably coupled to the valve needle 11 such as those of guiding elements of the valve needle 11 for example, cancel out each other such that a sensibility of the injector 1 to a variation of fluid pressure of fluid in the cavity 15 is kept low.
In the present embodiment, the injector 1 further comprises a fluid inlet 49 which is co-axially arranged relative to the valve body 9 with respect to the longitudinal axis 13 at an end section of the injector 1, remote from the valve seat 17. In this context, the injector may comprise a further O-ring co-axially arranged around the injector body 3, allowing for coupling a fluid terminal - such as an injector cup - to the fluid inlet 49. The fluid terminal may be fixedly coupled to the fluid inlet 49 by means of the further O-ring and radial hydraulic force caused by fluid pressure of fluid within the cavity 15.
In this regard, the chamber unit 37 and an inner wall of the valve body 9 form a fluid channel to allow for an axial fluid communication from the fluid inlet 49 towards the valve seat 17. In particular, the fluid is guided along a fluid path 51. A fluid filter 53 for filtering the fluid may be arranged in the fluid path 51. The fluid filter 53 may minimize external contamination effects.
The injector body 3 may comprise a body section 55 which is surrounded by the fluid filter 53. The body section 55 may be referred to as "fuel connector". The body section 55 and the injector body 3 may be two separate parts that are fixedly coupled.
Body section 55 has in particular a central axial opening and one or more radial bores extending through a circumferential sidewall which defines the central axial opening. An upstream end of the axial circumferential opening is fluid tightly closed, for example by means of the adjustment pin 31 and the first O-ring 45. The bellow 43 extends in the central axial opening and may or may not protrude from a downstream end of the central axial opening. A radial gap is established between the bellow 43 and the central axial opening so that fluid can enter into the body section 45 through the radial bores into the central axial opening and flow in axial direction along the central axial opening to the downstream end thereof and further towards the valve seat 17. The fluid filter 33 is in particular laterally surrounding the circumferential sidewall and connected to the circumferential sidewall in such fashion that fluid coming from the fluid inlet 49 has two pass the fluid filter 53 before entering the central axial opening of the body section 55 through the radial bores.
In order to assemble the injector 1, the armature 21 may be preassembled with the bellow 43. The armature 21 is then subsequently fixed to the valve needle 11.
The invention is not limited to specific embodiments by the description on the basis of said exemplary embodiments but comprises any combination of elements of different embodiments. Moreover, the invention comprises any combination of claims and any combination of features disclosed by the claims.

Claims

Injector (1) for injecting fluid with
- an injector body (3),

- a valve assembly (5) comprising a valve body (9) and a valve needle (11), the valve body (9) having a longitudinal axis (13) and comprising a cavity (15) with a valve seat (17), the cavity (15) being operable to take in the valve needle (11), the cavity (15) and the valve needle (11) being operable to prevent in a closing position of the valve needle (11), in which the valve needle (11) is seated on the valve seat (17), an injection of fluid from the cavity (15) to external to the injector (1), and to enable the injection of fluid when the valve needle (11) is apart from the closing position,

- an electromagnetic actuator assembly (7), which is operable to exert a force for influencing a position of the valve needle (11), comprising an armature (21) being received in the cavity (15) and mechanically coupleable to the valve needle (11),

- a spring chamber (27) located in the cavity (15), being fluid-tightly insulated from an exterior of the spring chamber (27), and

- a calibration spring (29) for axially biasing the valve needle (11) away from the closing position, being received in the spring chamber (27), being mechanically coupled to the valve needle (11) to bias the valve needle (11) with a first axial end (33) and being fixedly coupled to the injector body (3) with a second axial end (35) such that a position of the second axial end (35) is independent of fluid pressure of fluid in the cavity (15).
Injector (1) according to claim 1, wherein the spring chamber (27) is laterally limited by a chamber unit (37), the chamber unit comprising a bellow (43).
Injector (1) according to claim 2, wherein a wall of the cavity (15) and the chamber unit (27) form a channel, allowing for axial fluid communication.
Injector (1) according to any of previous claims 2 or 3, wherein the chamber unit (37) is fixedly coupled to the armature (21).
Injector (1) according to any of previous claims 1 to 4, wherein the spring chamber (27) is axially limited by the armature (21).
Injector (1) according to any of previous claims 1 to 5, comprising an adjustment pin (31) for adjusting a position of the second axial end (35), the adjustment pin (31) being fixedly coupled to the injector body (3), wherein the spring chamber (27) is axially limited by the adjustment pin (31).
Injector (1) according to claim 6, wherein the chamber unit (37) is fixedly coupled to the adjustment pin (31).
Injector (1) according to any of previous claims 6 or 7, comprising a first O-ring (45), sealing a radial gap between the adjustment pin (31) and the chamber unit (37).
Injector (1) according to any of previous claims 1 to 8, comprising a second O-ring (47), sealing a radial gap between the armature (21) and the valve needle (11).
Injector (1) according to claim 9, wherein the armature (21) has a recess, the second O-ring (47) being received in said recess.
Injector (1) according to any of previous claims 1 to 10, comprising a co-axially arranged fluid inlet (49).