EP3009657A1

EP3009657A1 - Housing assembly for a fuel injector, fuel injector and method for producing the housing assembly

Info

Publication number: EP3009657A1
Application number: EP14189088.9A
Authority: EP
Inventors: Valerio Polidori; Stefano Filippi; Mauro Grandi; Francesco Lenzi
Original assignee: Continental Automotive GmbH
Current assignee: Vitesco Technologies GmbH
Priority date: 2014-10-15
Filing date: 2014-10-15
Publication date: 2016-04-20
Anticipated expiration: 2034-10-15
Also published as: EP3009657B1

Abstract

A housing Assembly (1) for a fuel injector is disclosed. It has a connection tube (3), a separation disc (9) and a fuel tube (5) which are arranged along a longitudinal axis (L) to enable a streaming fluid pass through respective penetrating openings (11, 13, 17). It further comprises a housing (7) which extends circumferentially around a portion of the fuel tube (5). A first end (21) of the connection tube (3) at least partially contacts a first side (23) of the separation disc (9) and a second side (25) of the separation disc (9) at least partially contacts the housing (7). A sleeve (10) is configured to surround the housing (7) and the separation disc (9) and is at least partially connected to an outside surface (27) of the connection tube (3) or of the separation disc (9) and to an outside surface (29) of the fuel tube (5) to fasten the separation disc (9) to the housing (7).

Description

The invention relates to a housing assembly for a fuel injector, to a fuel injector and to a method for producing the housing assembly.
Injectors are in widespread use, in particular for combustion engines, where they may be arranged to dose a fluid into an intake manifold of the combustion engine or directly into a combustion chamber of a cylinder of the combustion engine.
In general a reliable and secure function of an injector inside a combustion engine is required and for this reason it is a task to counteract undesirable effects constantly. For example, regarding a solenoid outward opening injector the force given by a magnetic circuit is one of the most important parameters for a reliable performance of the injector.
One object of the invention is to create a housing assembly for a reliable and secure function for a fuel injector for a combustion engine to enable a reliable injector performance.
The object is achieved by the features of the independent claims. Advantageous embodiments of the invention are given in the dependent claims.
According to a first aspect of the invention, a housing assembly for a fuel injector is disclosed. According to a second aspect, a fuel injector with the housing assembly is disclosed. The fuel injector preferably has a solenoid actuator comprising a coil and an armature.
The housing assembly comprises at least the following components: a connection tube, a fuel tube, a housing, a separation disc and a sleeve. The components are arrangeable along a longitudinal axis and comprise penetrating openings respectively with respect to the longitudinal axis, in particular to arrange the components at least partially with each other and to enable a streaming fluid pass during an operation of the assembly.
Specifically, the connection tube, the separation disc, and the fuel tube may be arranged along the longitudinal axis to enable a streaming fluid pass through the penetrating openings during an operation of the assembly. In this way, the connection tube, the fuel tube and the separation disc form a fluid channel. The armature is preferably positioned in the fluid channel, particularly preferably in a region of the connection tube adjacent to the separation disc. In particular, the armature is axially displaceable in the fluid channel relative to the connection tube and the axial displaceability is limited by the separation disc.
The fuel tube is arranged inside the opening of the housing. In other words, the housing may extend circumferentially around a portion of the fuel tube which portion is in particular positioned inside the opening of the housing. The housing is in particular a coil housing for accommodating the coil. The housing is hydraulically separated from the fluid channel by the connection tube, the separation disc and the fuel tube. Preferably, a magnetic circuit of the solenoid actuator extends from the housing through the separation disc to the armature. The separation disc may be configured to contribute to shaping the magnetic flux of the magnetic circuit.
In a mounted configuration of the housing assembly, a first end of the connection tube at least partially contacts a first side of the separation disc and a second side of the separation disc at least partially contacts the housing. In particular the first side and the second side are understood to mean a first surface and a second surface of the separation disc which face in opposite axial directions, preferably at opposite axial ends of the separation disc.
Further, the fuel tube is partially arranged inside the opening of the separation disc. Preferably, it axially extends completely through the separation disc.
In an expedient embodiment, the housing is axially locked in place by means of a form-fit connection with the second side of the separation disc at one axial end of the housing and by means of a form-fit connection with a step of the fuel tube at the opposite axial end of the housing. In particular, the housing is pressed against the second side of the separation disc by means of mechanical interaction with the step.
The sleeve is configured to surround the housing and the separation disc and is at least partially connected to an outside surface of the connection tube or of the separation disc and to an outside surface of the fuel tube in a mounted configuration of the assembly to fasten the separation disc to the housing. The sleeve fastens the separation disc to the housing in particular by means of blocking axial displacement of the second side of the separation disc away from the step of the fuel tube. This is preferably achieved by means of the connections of the sleeve to the outside surfaces of the connection tube or of the separation disc, respectively, and of the fuel tube.
With advantage, the risk for undesirable air gaps, in particular between the separation disc and the coil housing is particularly small in this way. The magnetic circuit of the solenoid actuator may be particularly efficient in this way.
In an assembled configuration the sleeve is a component to fasten the separation disc to the housing and hence prevents or at least decreases a generation of an undesirable air gap between the mentioned components during an operation of the assembly.
During production of the housing assembly, the separation disc may be welded to the fuel tube. For example due to the effect of welding shrinkage, the separation disc may tend to move axially away from the housing in a conventional housing assembly. This movement may result in an undesirable air gap that causes a lack of magnetic force during an operation of the injector, which may advantageously be avoided by the housing assembly according to the present invention.
By using the housing assembly with the sleeve as a connecting component, it is not necessary to change other components for example in consideration of a shape or a roughness. In this way, a reliable and secure functioning of the fuel injector can be easily realised.
In an expedient embodiment, the fuel tube has a circumferential protrusion which forms the step and which is in form-fit engagement with the sleeve to limit displacement of the sleeve in axial direction from the step towards the separation disc. In another expedient embodiment, a form-fit connection and/or a welded connection is established between the first side of the separation disc and the connection tube to block axial movement of the separation disc towards the connection tube. In this way, the sleeve is operable to retain the housing in contact with the separation disc in particularly simple and reliable fashion.
According to one embodiment, the connection tube and the sleeve are connected by a welding connection. In this way, the sleeve is particularly securely connected to the connection tube and hence the risk of contact loss between housing and separation disc during an operation of the injector is particularly small. The welding connecting between the sleeve and the connection tube realises a reliable and competitive way to bond these components and because the sleeve is also connected to the fuel tube, the fuel tube and the housing may be pressed to the separation disc due to the effect of welding shrinkage at the welding connection between sleeve and connection tube. This ensures the contact of the housing to the separation disc and hence prevents or at least decreases an undesirable air gap during an operation of the assembly.
According to a further embodiment of the first aspect the fuel tube and the sleeve are connected by means of a form- and/or force-fit connection. This enables a simple configuration of the assembly to connect the sleeve to the fuel tube and hence to achieve a reliable and secure connection and functioning of the injector.
In one embodiment, the sleeve may comprise a radially inward extending flange that is in contact with a radial protrusion of the fuel tube to establish the form-fit connection. The flange is in particular positioned at an axial end of the sleeve remote from a contact region of the sleeve with the connection tube or separation disc, respectively.
According to a further embodiment, the housing assembly comprises at least one coil - i.e. in particular the at least one coil of the solenoid actuator - that is arranged in a recess of the housing.
In a further embodiment, the fuel injector comprises a valve needle which is at least partially arranged in the opening of the fuel tube and which is configured to prevent a fluid flow through the injector in coaction with a seal seat in a closed position or otherwise to enable it. In one embodiment, the fuel injector is an outward opening injector.
According to a third aspect of the invention a method for producing a housing assembly for a fuel injector comprises providing a connection tube, a fuel tube, a housing, a separation disc and a sleeve that comprise penetrating openings respectively with respect to a longitudinal axis. The method further comprises assembling the housing onto the fuel tube from a first direction with respect to the longitudinal axis so that the fuel tube is partially arranged inside the opening of the housing. The method further comprises press-fitting the separation disc and the connection tube onto the fuel tube from the first direction with respect to the longitudinal axis until the separation disc contacts the housing. Moreover, the method comprises shifting the sleeve onto the fuel tube from a second direction with respect to the longitudinal axis until the sleeve contacts an outside surface of the fuel tube and an outside surface of the connection tube. The method further comprises connecting the sleeve to the connection tube by a welding connection and connecting the separation disc to the fuel tube by a further welding connection.
This aspect of the invention describes a method for construction of the assembly for example to create an injector which is enabled to prevent an undesirable air gap and to avoid a lack of force during an operation. This enables a reliable and secure functioning and an improved controlling of the injector.
The welding connections between the connection tube and the sleeve as well as the separation disc and the fuel tube enable a simple and competitive possibility for construction of the assembly as described above.
In an expedient embodiment, press-fitting the sleeve onto the fuel tube comprises press-fitting the sleeve onto the fuel tube from the second direction until the sleeve comes in contact with the outside surface of the connection tube and establishes a form-fit connection with the protrusion of the fuel tube at the outside surface of the fuel tube. In a further embodiment, assembling the housing onto the fuel tube comprises shifting the housing over the fuel tube in the first direction until the housing is in form-fit engagement with the step of the fuel tube which is formed by the protrusion. In this way, an air gap between the housing and the separation disc can be prevented particularly well.
In one embodiment, welding of the sleeve to the connection tube is done before welding of the separation disc to the fuel tube. Therefore, one function of the sleeve may be to pull down the separation disc to the housing due to the effect of welding shrinkage given by the welding joint between the sleeve and the connection tube. In this way, the second side of the separation disc may be pressed against the housing. A particularly good contact between these two components may be established in this way.
According to one embodiment, the method comprises connecting the separation disc to the connection tube by a further welding connection.
This configuration describes a simple and reliable way to connect the mentioned components just by means of welding and hence enables a reliable and competitive way of manufacturing the assembly or the injector as mentioned above.
For example, the welding connection between the separation disc and the connection tube is already done before the other both mentioned welding connections. In this case, the separation disc is forced in its position and when it is welded to the fuel tube it cannot move away from the housing due to the sleeve that is welded to the connection tube and pulls the connection tube as well as the separation disc in direction to the housing.
By using the described method for construction of the housing assembly, an injector can be created which enables an improved performance during operation and which in particular makes a contribution to prevent a lack of force and undesirable air gaps or at least decreases it.
Exemplary embodiments of the invention are explained in the following with the aid of schematic drawings and reference numbers. Identical reference numbers designate elements or components with identical functions. The figures show:

Figure 1: a fuel injector for a combustion engine with a housing assembly;
Figure 2: an exemplary embodiment of a housing assembly;
Figures 3a to 3e: method steps of a method for producing a housing assembly for a fuel injector according to an exemplary embodiment;
Figures 4a and 4b: an exemplary embodiment of a housing assembly in different side views.

Figure 1 shows a fuel injector 30 which has a longitudinal axis L and comprises a valve needle 31 and a seal seat 33. The valve needle 31 is arranged axially movable with respect to a longitudinal axis L relative to the seal seat 33. In the present embodiment, the injector 30 is an outward opening injector 30.
The valve needle 31 is biased by a spring element 32 towards the seal seat 33. The valve needle 31 sealingly rests on the seal seat 33 in a closing position due to forces acting on it, amongst others one force being a spring force by the spring element 32.
Depending on the force balance, the valve needle 31 is axially moved away from its closing position or moved into its closing position and hence a flow of a fluid through the injector 30 is enabled or prevented. One actuating force is exerted by the spring element 32, another actuating force is exerted by an actuator in order to move the valve needle 31 with respect to the longitudinal axis L. Furthermore, a hydraulic force which is exerted by the fluid is a further force acting on the valve needle 31.
The actuator element may be an electromagnetic actuator, also denoted as solenoid actuator. In this example, the actuator comprises a coil 22 which generates a magnetic force on an armature 40. The armature 40 is mechanically coupled to the valve needle 31. It is movable in reciprocating fashion along the longitudinal axis L and is axially displaced towards the coil 22 to move the valve needle 31 away from the closing position. The coil 22 is arranged in a recess 24 of a housing 7.
The injector 30 comprises a housing assembly 1, which comprises a connection tube 3, a fuel tube 5, the housing 7, a separation disc 9 and a sleeve 10. These mentioned components comprise several openings 11, 13, 15, 17, 19 to arrange the components at least partially with each other and to enable the streaming fluid pass the assembly 1 and the injector 30. Thereby, the connection tube 3 comprises the opening 11, the fuel tube 5 comprises the opening 13, the housing 7 comprises the opening 15, the separation disc 9 comprises the opening 17 and the sleeve 10 comprises the opening 19. Further details of the assembly 1 are illustrated below in the following figures 2 to 4. The connection tube 3, the fuel tube 5 and the separation disc 9 form a fluid channel. The connection tube 3, the fuel tube 5 and the separation disc 9 hydraulically separate the housing 7from the fluid channel. The sleeve 10 circumferential surrounds the housing 7, the separation disc 9, a portion of the connection tube 3 and a portion of the fuel tube 5.
Figure 2 shows an enlarged view of the housing assembly 1. In this exemplary embodiment, the separation disc 9 is connected to the connection tube 3 by a welding connection 36 and forms a bottom of the connection tube 3. The separation disc 9 is one fluid leading component and forms one part of an exterior wall of the fluid channel. Moreover, the separation disc 9 has a magnetic function to enable a magnetic coupling between the coil 22 and corresponding movable injector components like the armature 40.
The separation disc 9 comprises a first side 23, i.e. a first surface, which forms a bottom area of the connection tube 3 and a second side 25, i.e. a second surface, which faces and contacts the housing 7 in an assembled configuration. The housing 7 is axially locked in place by means of a form-fit connection with the second side 25 of the separation disc 9 at one axial end of the housing 7 and by means of a form-fit connection with a step 140 of the fuel tube 5, i.e. in particular a step 140 of the outside surface 29 of the fuel tube 5, at the opposite axial end of the housing 7.
At a first end 21 of the connection tube 3, adjacent to the separation disc 9, the sleeve 10 is connected to an outside surface 27 of the connection tube 3. For example, the sleeve 10 is connected to the connection tube 3 by means of a welding connection.
The sleeve 10 is further connected to an outside surface 29 of the fuel tube 5. For example, the sleeve 10 is connected to the fuel tube 5 due to form fit and/or force fit. In the present exemplary embodiment, the sleeve 10 comprises a radially inward extending flange 12 which is in form-fit engagement with a radially extending circumferential protrusion 14 of the fuel tube 5.
By means of these connections, the connection tube 3, the separation disc 9 and the fuel tube 5 are coupled by the sleeve 10 in such fashion that axial displacement of the second side 25 of the separation disc 9 away from the step 140 of the fuel tube 5 is blocked. This allows to keep the contact of the separation disc 9 to the housing 7. In this way, magnetic losses due to contact loss between the housing 7 and the separation disc 9 during an operation of the assembly 1 or the injector 30 are avoidable.
Figures 3a to 3e illustrate method steps of an exemplary method for producing the housing assembly 1.
In a first method step, the housing 7 is assembled onto the fuel tube 5 from a first direction D1 with respect to the longitudinal axis L. The fuel tube 5 is shifted into the opening 13 of the housing 7 until a bottom side of the housing 7 contacts a step 140 in the outside surface 29 of the fuel tube 5and establishes a form-fit engagement with the step 140.
A subsequent second method step is illustrated in figure 3b. In this method step, the separation disc 9 and the connection tube 3 are press-fitted onto the fuel tube 5 from the first direction D1 until the second side 25 of the separation disc 9 contacts an upper side of the housing 7 with respect to the longitudinal axis L. The term press-fit is illustrated in this figure 3b by two bold arrows to indicate a force that presses the separation disc 9 to the housing 7.
A subsequent third method step is shown in Figure 3c. In this method step, the sleeve 10 is shifted onto the fuel tube 5 from a second direction D2 with respect to the longitudinal axis L until the sleeve 10 comes in contact with the outside surface 27 of the connection tube 3 at one axial end of the sleeve 10 and establishes a form-fit connection by means of its flange 12 with a protrusion 14 of the fuel tube 5 at the outside surface 29 of the fuel tube 5. The sleeve 10 then contacts the outside surface 27 of the connection tube 3 in the region of the separation disc 9 at the first end 21 of the connection tube 3 and it contacts the protrusion 14 of the fuel tube 5 with its radially inward extending flange 12. The protrusion 14 forms the above mentioned step 140 of the outside surface 29 of the fuel tube 5. The form-fit connection with the protrusion 14 blocks further displacement of the sleeve 10 in the second direction D2 relative to the fuel tube 5.
A subsequent forth method step is illustrated in Figure 3d. In this method step, a reliable and secure connection between the sleeve 10 and the connection tube 3 is made by a welding connection 26 to fasten the sleeve 10 to the connection tube 3. Because of the effect of welding shrinkage at the welding connection 26 and the form-fit connection of the sleeve 10 with the protrusion 14 of the fuel tube 5, the connection tube 3, the separation disc 9 and the fuel tube 5 are pressed together in direction of the longitudinal axis L by the sleeve 10 so that axial displacement of the second side 25 of the separation disc 9 away from the step 140 is blocked an the housing 7 is axially compressed between the second side 25 and the step 140 to avoid an air gap between the separation disc 9 and the housing 7. This enables a simple construction of the assembly 1 and hence a reliable and secure functioning of the injector 30 wherein a lack of force and an undesirable air gap between the separation disc 9 and the housing 7 is prevented or at least decreased.
In Figure 3e, a subsequent fifth method step is shown. In this method step, a welding connection 28 is produced between the separation disc 9 and the fuel tube 5, for example by laser welding. Producing of this welding connection 28 in principle tends to separate the separation disc 9 from the housing 7 due to welding shrinkage. However, since the sleeve 10 blocks displacement of the separation disc 9 in axial direction away from the step 140, such separation is advantageously avoided. Therefore, an improved magnetic performance of the injector 30 is achieved while at the same time the mechanical stability and the fluid-tightness of the assembly 1 is further enhanced.
In reference to the exemplary method steps the sleeve 10 is assembled and welded to the connection tube 3 before the separation disc 9 is welded to the fuel tube 5. This means, that the separation disc 9 is forced in its position and when it is welded to the fuel tube 5 it cannot move away from the housing 7 since the sleeve 10 that is already welded to the connection tube 3 and pulls the connection tube 3 as well as the separation disc 9 down to the housing 7 in the first direction D1 with respect to the longitudinal axis L.
In the figures 4a and 4b, the housing assembly 1 is shown in a mounted configuration in different side views corresponding to a side view and a top view of an electrical connector inlet of the housing 7. In these figures it is apparent that the sleeve 10 surrounds the housing 7 and the separation disc 9 and is connected to the connection tube 3 by the welding connection 26 and to the fuel tube 5 due form-fit by the radially inward extending flange 12 and the corresponding protrusion 14 which is not visible in these figures.
In this exemplary embodiment, the sleeve 10 further comprises a recess 35 for reasons of electrical connections for example which is represented by an electrical connector 38. Such a recess 35 may be useful to expose the electrical connector inlet of the housing 7. In such a case, the sleeve 10 only partly circumferentially surrounds the housing 7 and the separation disc 9.
By manufacturing and assembling - i.e. producing - the housing assembly 1 for the injector 30 with the sleeve 10 as a connecting component, it is not necessary to change existing components for example in consideration of a shape or a roughness. In this way, a reliable and secure functioning of the injector 30 can be easily realised without expensive adaptions like interferences between components, weldings or others.

Claims

Housing Assembly (1) for a fuel injector comprising following components:
- a connection tube (3),

- a fuel tube (5),

- a housing (7),

- a separation disc (9) and

- a sleeve (10),
wherein

- the connection tube (3), the separation disc (9) and the fuel tube (5) each comprise a penetrating opening (11, 13, 17) with respect to a longitudinal axis (L) and are arranged along the longitudinal axis (L) to enable a streaming fluid pass through the penetrating openings (11, 13, 17) during an operation of the assembly (1),

- the fuel tube (5) is partially arranged inside the opening (17) of the separation disc (9),

- the housing (7) comprises a penetrating opening (15) with respect to the longitudinal axis (L) and extends circumferentially around a portion of the fuel tube (5) which is positioned inside the opening (15) of the housing (7),

- a first end (21) of the connection tube (3) at least partially contacts a first side (23) of the separation disc (9) and a second side (25) of the separation disc (9) at least partially contacts the housing (7), and

- the sleeve (10) is configured to surround the housing (7) and the separation disc (9) and is at least partially connected to an outside surface (27) of the connection tube (3) or of the separation disc (9) and to an outside surface (29) of the fuel tube (5) to fasten the separation disc (9) to the housing (7).
Housing assembly (1) in accordance with the preceding claim, wherein
- the housing (7) is axially locked in place by means of a form-fit connection with the second side (25) of the separation disc (9) at one axial end of the housing (7) and by means of a form-fit connection with a step (140) of the fuel tube (5) at the opposite axial end of the housing (7) and

- axial displacement of the second side (25) of the separation disc (9) away from the step of the fuel tube (5) is blocked by means of the connections of the sleeve (10) to the outside surfaces (27, 29) of the connection tube (3) or of the separation disc (9), respectively, and of the fuel tube (5).
Housing assembly (1) in accordance with the preceding claim, wherein the fuel tube (5) has a circumferential protrusion (14) which forms the step (140) and which is form-fit engagement with the sleeve (10) to limit displacement of the sleeve (10) in axial direction from the step (140) towards the separation disc (9).
Housing assembly (1) in accordance with one of the preceding claims, wherein the connection tube (3) and the sleeve (10) are connected by a welding connection (26).
Housing assembly (1) in accordance with one of the preceding claims, wherein the fuel tube (5) and the sleeve (10) are connected by means of a form- and/or force-fit connection.
Housing assembly (1) in accordance with one of the preceding claims, wherein the connection tube (3) and the separation disc (9) are connected by a welding connection (36).
Housing assembly (1) in accordance with one of the preceding claims, comprising at least one coil (22) that is arranged in a recess (24) of the housing (7).
Injector (30) for a combustion engine comprising
- a housing assembly (1) in accordance with one of the preceding claims, and

- a valve needle (31) which is at least partially arranged in the opening (13) of the fuel tube (5) and which is configured to prevent a fluid flow through the injector (30) in coaction with a seal seat (33) in a closed position or otherwise to enable it.
Method for producing a housing assembly (1) for a fuel injector, comprising
- providing a connection tube (3), a fuel tube (5), a housing (7), a separation disc (9) and a sleeve (10) that comprise penetrating openings (11, 13, 15, 17, 19) respectively with respect to a longitudinal axis (L),

- assembling the housing (7) onto the fuel tube (5) from a first direction (D1) with respect to the longitudinal axis (L) so that the fuel tube (5) is partially arranged inside the opening (15) of the housing (7),

- press-fitting the separation disc (9) and the connection tube (3) onto the fuel tube (5) from the first direction (D1) with respect to the longitudinal axis (L) until the separation disc (9) contacts the housing (7),

- shifting the sleeve (10) onto the fuel tube (5) from a second direction (D2) with respect to the longitudinal axis (L) until the sleeve (10) comes in contact with an outside surface (27) of the connection tube (3) and establishes a form-fit connection with a protrusion (14) of the fuel tube (5) at an outside surface (29) of the fuel tube (5),

- connecting the sleeve (10) to the connection tube (3) by a welding connection (26), and

- connecting the separation disc (9) to the fuel tube (5) by a welding connection (28).
Method in accordance with claim 9, wherein assembling the housing (7) onto the fuel tube (5) comprises shifting the housing (7) over the fuel tube (5) in the first direction (D1) until the housing (7) is in form-fit engagement with a step (140) of the fuel tube (5) which is formed by the protrusion (14).
Method in accordance with claim 9 or 10, comprising connecting the separation disc (9) to the connection tube (3) by a welding connection (36).