EP3094853B1

EP3094853B1 - Bobbin with venting conduit

Info

Publication number: EP3094853B1
Application number: EP14806214.4A
Authority: EP
Inventors: Anthony Piton; Philippe Barbier; Thierry Thibault
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2014-01-15
Filing date: 2014-11-25
Publication date: 2020-09-02
Anticipated expiration: 2034-11-25
Also published as: CN106133305A; GB201400650D0; EP3094853A1; KR102204703B1; KR20160107287A; WO2015106866A1; CN106133305B

Description

TECHNICAL FIELD

The present invention relates to a method for process manufacturing of a bobbin assembly and has particular but not exclusive application to fuel injectors for use in delivering fuel under pressure to a combustion space of an internal combustion engine.

BACKGROUND OF THE INVENTION

A known fuel injector for use in such a fuel system is illustrated in fig 1 and includes a nozzle needle 10 slidable within a bore. The needle 10 is slipping within a bore formed in a nozzle body 17 and engageable with a seating to control fuel delivery through one or more outlet openings. Movement of the nozzle needle 10 occurs rapidly, in use, the periods during which fuel injection occurs being of short duration. A similar fuel injector is disclosed in EP2320066A1 .
The movement of the needle is controlled using two chambers, a high pressure control chamber 12 and a low pressure chamber 16, which communicates with low pressure drain reservoir 22. When injection starts, an actuator 30 is energized (opening phase), which urges an armature 29 and a valve member 25 in contact therewith, identified as a control valve 15, located in the chamber to move upwards against the action of a bobbin spring 33 of the actuator 30. At this stage, the length of the spring 33 is reduced and then the pressure within the bobbin spring area 43 increases, thus there is a movement of the fluid in the spring area 43 which perturbs the displacement of the armature 29 secured to the valve member 25 . This problem will be solved by the present invention, which will further be described.

SUMMARY OF THE INVENTION

A bobbin assembly of an electromagnetic actuator is adapted to be in a fuel injector. The bobbin assembly comprises a core extending along a main axis, a wire coil arranged around the core. The coil is over-moulded so that it has a cylindrical external surface extending axially from a first surface to a second surface and an axial blind bore extending axially and inwardly inside the bobbin assembly from the first surface to the distal end. Moreover the blind bore is adapted to accommodate a spring for biasing a magnetic armature. Furthermore the bobbin assembly is provided with a venting conduit extending through the over-moulding from the blind axial bore to the external cylindrical surface.
In addition the venting conduit is arranged proximal to the distal end. Moreover the venting conduit is proximal to the first face of the bobbin and comprises at least one groove in the first radial surface. Besides the venting conduit makes an angle with the main axis between 80 degrees and 120 degrees. Additionally the angle can be preferably 90 degrees. In addition the actuator of the fuel injector comprises the bobbin assembly and the fuel injector comprises the actuator . A method for process manufacturing of the bobbin assembly comprises the following steps:

winding of the wire on the sub assembly, wrapping of the wire on one end of the terminals, an installation of the covers on the wrapping , welding of the covers , fit of a jacket on the area of the wire winding, then over-moulding and grinding of the bobbin assembly and providing the venting conduit in the over-moulding of the bobbin assembly. Moreover the venting conduit is made by drilling the venting conduit in the over-moulding.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig 1 is a sectional view of the overall assembly of a known injector
Fig 2 and Fig 3 are the sectional views of a fuel injector with the venting conduit in different phases (opening).
Figure 4 is a sectional view of the bobbin assembly area and the venting conduit.
Fig 5 is a sectional view of a inclined venting conduit
Fig 6 and Fig 7 are the sectional views of the manufacturing the bobbin assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

PRIOR ART (Fig 1)

In the following description, similar parts will be described by the same references. To be concise and for clarity of the description, the upper and lower orientation will be used as the orientation of the figures with no limitation for the scope of the protection, in particular in regard to the different embodiments. Words like "upper, lower, top bottom... "will be used without limitative intent.
According to a known fuel injector for use in such a fuel system in illustrated in fig 1 and includes a valve needle 10 slidable within a bore 11. The bore 11 takes the form of a blind bore formed in a nozzle body 17; the bore 11 is supplied with fuel under high pressure. The needle 10 includes a surface exposed to the fuel pressure within a control chamber 12. The control chamber 12 is supplied with fuel under high pressure from a supply passage 13 dimensioned such that fuel is only permitted to flow to the control chamber 12 at a restricted rate.
A spring 20 is located within the control chamber 12, the spring acting to apply a biasing force to the needle 10 urging the needle 10 into engagement with the seating.
The movement of the needle is controlled using two chambers, a high pressure control chamber 12 and a low pressure chamber 16, which communicates with low pressure drain reservoir 22. When injection starts, an actuator 30, which comprises a bobbin assembly 44 and a control valve 15, is energized (opening phase), which urges an armature 29 and a valve member 25 in contact therewith, identified as a control valve 15, located in the chamber 16 to move upwards against the action of a bobbin spring 33 of the actuator 30, lifting the valve member 25 away for its seating. As a result, fuel is able to escape from the control chamber 12 to the chamber 16 which is at a low pressure, due to its connection with the low pressure reservoir by a return passage 27 (not shown in figures) .As a result, the fuel pressure in the control chamber 12 falls, and as a result, the force applied to the needle 10 urging the needle 10 to is seating also falls. A point will be reached beyond which the fuel pressure acting upon a thrust surface 10a is sufficient to lift the needle 10 away from its seating, and permitting fuel from the bore 11 to flow past the seating to the outlet openings and into the combustion space with which the injector is associated.

EMBODIEMENT: FIGURES 2, 3, 4, 5, 6 and 7.

As illustrated in figure 2, when the electromagnetic control valve 15 is not energized, the valve member 25 engages its seating 46, and then the bore 11 and the control chamber 12 will contain fluid under high pressure. The action of the high pressure in the control chamber 12 and the action of the spring 20 is sufficient to ensure that the needle 10 remains in engagement in its seating and the injector 5 is closed with no injection of fluid.
As illustrated in figure 2, the control chamber 12 is supplied with fuel from an INO orifice 52, conduit which supplied fuel from the common rail (not shown), through a hemispheric part 50, dimensioned such that fuel is only permitted to flow to the control chamber 12 at a restricted rate. The spring 20 is within the control chamber 12, the spring 20 acting to apply a biasing force to the needle 10, urging the needle 10 into engagement with its seating.
As illustrated in figure 3, when the injection is to start, an actuator 30, which includes the control valve 15 and a bobbin assembly 44 which includes a sub assembly 90, is energized, urging the armature 29 and valve member 25 to move upwards against the action of the spring 33, lifting the valve member 25 away for its seating. As a result, fuel is able to escape from the control chamber 12 to the chamber 16 (fig 3) which is at a low pressure, through an hemispheric part 51 and then through a spill canal SPO 54 (figure 3), and then the fuel escape from the chamber 16 to a return passage 27 (figure 3).
In the control chamber 12, there are 2 orifices; one is the INO orifice 52 (fig 2) which fills in the chamber 12 with fuel and the SPO orifice 54 (fig 3) which empty the chamber of its fluid. Then the ratio INO/SPO is calculated in order to empty quicker than to fill-in.
A first embodiment is now described in reference to figure 4.
When the actuator 30 is energized, the actuator spring 33 is compressed by the pressure urged by the armature 29, thus the pressure in an axial blind bore 43 increases. During the opening phase of the control valve 15, the length of the spring 33 is reduced so the volume of the axial bore 43 is reduced so the pressure increases. The armature 29, moving upwards, urges the fluid in the axial bore 43, which is a blind bore and the fluid wave moves back downwards to the armature 29 and the fluid wave perturbs the control valve 15. The overpressure within the axial bore 43 is suppressed by a venting conduit 42 which is fluidically connected to the axial bore 43 by one end and by the other end to a low pressure area 41, which communicates to a return circuit 40. The venting conduit 42 is within an over-moulded coil 96, from the axial bore (43), which is the area of the spring 33, to the external cylindrical surface (108)
Furthermore the venting conduit 42 is at the proximal portion of upper part of the axial bore 43. Moreover the venting conduit 42 make an angle of 90 degree to the main axis of the injector 5 and the shape of the venting conduit 42 is round or square or conical. The venting conduit 42 is made by machining, drilling or with the use of an insert during the over moulding 96 of the bobbin assembly 44. In a further embodiment, the venting conduit 42, makes an angle, for instance between 80 degrees and 120 degrees from the main axis (vertical) of the injector 5 and the shape of the venting conduit 42 is round or square or conical. The venting hole is made by machining, drilling or with the use of an insert during the over-moulding 96 of the bobbin assembly 44.
In another aspect of the invention, the manufacturing process is now described. As shown in the figure 6 and 7, the bobbin assembly 44 includes the sub assembly 90 which includes a coil 92, two terminals 94, an over moulding 96 and a jacket 98. The bobbin assembly 44 starts with the following steps:

winding of the wire 92 on the sub assembly 90 and then;
wrapping of the wire 92 ends on the low end of the terminals 94 and then;
installation of the covers 95 down on the lower ends of the terminals 94 and then;
welding of the cover 95 on the lower ends of the terminals 94 then;
fit of a jacket 98 on the area of the wire winding (92) and then;
over-moulding and grinding of the bobbin assembly (44) ;
Providing the venting conduit (42) by the use of insert in the over moulding phase of the bobbin assembly (44) or by drilling after the over-moulding of the bobbin assembly.
Insert of the washer 100 and the joint 102 in the terminal end side of the bobbin assembly (44);

Claims

Method for process manufacturing of a bobbin assembly (44) comprising a core (93) extending along a main axis,
a coil (92) arranged around the core (93), the coil being over-moulded so that it has a cylindrical external surface (108) extending axially from a first surface (104) to a second surface and an axial blind bore (43) extending axially and inwardly inside the bobbin assembly (44) from the first surface (104) to a distal end (106), the blind bore (43) adapted to accommodate a spring (33) for biasing a magnetic armature; the bobbin assembly (44) further provided with a venting conduit (42) extending through the over-moulding (96) from the blind axial bore (43) to the external cylindrical surface (108), the method for process manufacturing of a bobbin assembly (44) comprising the following steps:
- winding of a coil (92) on a sub assembly (90) comprising terminals (94),

- wrapping of the coil (92) on one end of the terminals (94) and then;

- installation of a cover (95) on the wrapping and welding of the cover (95) then;

- fit of a jacket (98) on the area of a wire winding and then;

- over-moulding and grinding of the bobbin assembly (44) and then;

- providing a venting conduit (42) in the over-moulding (96) of the bobbin assembly (44); the venting conduit (42) made by drilling the venting conduit (42) in the over-moulding (96), and wherein the venting conduit (42) makes an angle with the main axis between 80 degrees and 120 degrees.
Method for process manufacturing of a bobbin assembly (44) as set in claim 1, wherein the venting conduit (42) is arranged proximal to the distal end (106)
Method for process manufacturing of a bobbin assembly (44) as set in claim 1, wherein the venting conduit (42) is proximal to the first face (104) of the bobbin (44).
Method for process manufacturing of a bobbin assembly (44) as set in claim 1, wherein the venting conduit 42 makes an angle of 90 degree to the main axis .
Method for process manufacturing of a bobbin assembly (44) as set in any one of claims 1 to 4, wherein an actuator (30) comprises the bobbin assembly (44).
Method for process manufacturing of a bobbin assembly (44) as set in claim 5, wherein an injector (5) comprises the actuator (30).