ELECTROMAGNETIC ACTUATOR

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an electromagnetic actuator and, more specifically, to an electromagnetic actuator and method for producing same, which reduces the number of constituent parts while simplifying the electrical connection of the electromagnetic coil to a connector terminal providing a connection for control and supply of electrical energy to the actuator.

BACKGROUND OF THE INVENTION

In automatic engine applications, it is well known to use electromagnetic actuators in fuel injectors for controlling the injection of fuel into the cylinders of spark ignition engines such as diesel engines. The fuel injectors are generally coupled between a fuel rail and an intake manifold of an internal combustion engine. In response to an electronic control signal, the electromagnetic actuator allows the fuel injector to pass fuel from the fuel rail into the intake manifold for a predetermined time.

In conventional electromagnetic actuated fuel injectors, the electromagnetic actuator operates a valve of the fuel injector between an open and a closed position by producing an electromagnetic force on an armature coupled to the valve. The armature is biased by a spring, which exerts a counter-action force that closes the valve when the electromagnetic force produced by the electromagnetic actuator is shutoff.

Generally, the component parts of the electromagnetic actuator are assembled and welded, brazed or otherwise sealed together to provide internal fuel passages for conducting fuel through the injector.

A conventional electromagnetic actuator comprises a magnetic core and an electromagnetic coil mounted on a bobbin. The general method for mounting the electromagnetic coil consists in preparing a bobbin on which two electric terminals are mounted such as to extend upright thereof. The wire of the electromagnetic coil is wound on the bobbin and the extremities of the wire are wound and soldered, welded or electrically connected by any suitable means to the electrical terminals. The coil/bobbin assembly are then arranged in the magnetic core and electrically insulated from the core.

However, the connecting operation of the electromagnetic coil to the terminal pins is laborious to perform. In addition, the use of several "O" rings is normally required for preventing leakages of fluid into the assembled parts, for instance, for sealing the coil bobbin assembly and electric terminals from the fuel passageways.

Consequently, the assembly operation of all parts constituting an electromagnetic actuator, including the mounting of the electromagnetic coil, and its assembly in a fuel injector is particularly complex, requiring specific equipment and specialized manpower.

Therefore, the production of electromagnetic actuated injectors involves relatively high production costs and a long time for assembling.

Several methods have been proposed for simplifying the assembling process. For instance, the published European patent application EP 1 612 400 proposes a method for obtaining a fuel injector, in which the magnetic core, the bobbin coil and the pair electric terminals mounted on the bobbin are positioned inside the cavity of a mold, and plastic material is injected in the cavity for enclosing the bobbin coil, the electric terminals and part of the core. The injected material also forms a fuel passageway through the magnetic core and coil. However, according to the proposed method, the assembling of the bobbin coil, electrical terminals, and magnetic core have to be performed prior to their introduction into the mold. In addition, "O" rings still have to be used for sealing the plastic housing from the external body of the injector and the electrical contacts emerging from the housing.

United States patent 5 185 919 aims at reducing the assembly steps and the plurality of "O" rings with an injection molding process for providing a plastic housing that seals hermetically a magnetic core, a coil bobbin and electric terminals mounted on the coil bobbin. The plastic housing also forms the injector body and an axial fuel passageway. However, the proposed method has the disadvantage that the mold has to be adapted to the structural details of each fuel injector, such as external shape, the internal disposition and size of component parts. This results in a poor flexibility of the method for providing fuel injectors of different designs.

Both methods use electrical terminals for connecting to external power sources that are mounted on the bobbin coil and to which the electromagnetic coil is electrically connected prior to the molding process. Hence, the time and costs associated with the connecting operation of the coil are not eliminated. In addition, according to the above

methods, the injection process is performed at an early stage of the assembling of the electromagnetic actuator. Therefore, if the molding operation is not performed properly, the entire assembled parts are not reusable and have to be discarded.

SUMMARY OF THE INVENTION

The present invention aims at overcoming the disadvantages and shortcomings of the prior art techniques and an object thereof is to provide an electromagnetic actuator and a method for fabricating same, which allows to reduce the number of constituent parts while simplifying the electrical connections of the electromagnetic actuator.

This object is solved by the subject matter of the independent claims. Advantageous embodiments of the present invention are defined by the dependent claims.

The present invention provides an electromagnetic actuator that comprises a core, an electromagnetic coil, a housing, in which the core and the electromagnetic coil are enclosed, and a connector terminal arranged on the housing, wherein an end portion of a wire that forms the electromagnetic coil extends through the housing to the connector terminal, thereby electrically connecting the electromagnetic coil to the connector terminal.

Consequently, according to the invention, the coil of the electromagnetic actuator can be directly connected to the connector terminal without requiring the use of intermediate electrical terminals traversing the housing of the actuator.

According to an advantageous embodiment of the invention, the connector terminal is mounted on an outer surface of the housing and the end portion of the wire made to protrude out of the outer surface of the housing to connect to the connector terminal.

By providing a connector terminal that is completely external to the housing, the present invention enables that the connecting operation of the electromagnetic coil be performed after the electromagnetic coil and the magnetic core are arranged in the housing, therefore eliminating the risk of electrical connections performed prior to assembly being damaged during the assembling operation. In addition, the present invention allows that electromagnetic actuators with different configurations of connector terminals and/or housings be fabricated using the same electromagnetic coil and core, resulting in an increased flexibility in the design of the electromagnetic actuator.

In order to insulate the electromagnetic coil from the core, the electromagnetic actuator according to the invention may comprise an insulating body that is adapted to enclose a winding of the electromagnetic coil, the insulating body further comprising a sleeve adapted to enclose a part of the end portion of the wire, the end portion of the wire extending from the winding of the electromagnetic coil through the housing.

Consequently, the insulating body also fulfills the function of a supporting bobbin for carrying the electromagnetic coil and provides a supporting sleeve for leading an extremity of the magnet wire that is extended away from the winding of the electromagnetic coil and is made to pass through the housing for connecting directly to the connector terminal.

The housing may have a through-hole adapted to lead the end portion of the wire through the housing, wherein the sleeve may be comprised along one portion of a length of the through-hole.

The electromagnetic actuator may further comprise a fluid-tight seal arranged in the through-hole of the housing for sealing a space between the sleeve and the outer surface of the housing.

In this way, by providing a sleeve with a length such that the sleeve penetrates partially in the housing, the end portion of the wire is conducted by a rigid support over at least a part of its path through the housing. The provision of a fluid-tight seal to fill the space around the end portion of the wire and that is between the sleeve and the outer surface of the housing allows preventing fluid leakages into the electromagnetic coil.

The fluid-tight seal may be made of dispensed silicone or alternatively, the fluid-tight seal may be made of a material suitable for preventing fluid leakage that is filled in the space between the sleeve and the outer surface of the housing by potting.

The core may be a hollow core extending along a longitudinal axis and may comprise a coaxial blind cavity adapted to house the insulating body and the electromagnetic coil.

According to an advantageous embodiment, the insulating body comprises a first member and a second member that complement each other, each one of the first (28a) and the second (28b) members being adapted to accommodate the winding of the electromagnetic coil and to comprise a part of the sleeve of the insulating body.

According to an advantageous development of the invention, the first member is a molded member, which comprises a pocket adapted to house the winding of the electromagnetic coil and further comprises a longitudinal part of the sleeve adapted to support the part of the end portion of the wire, the end portion of the wire extending from the winding of the electromagnetic coil through the housing.

The second member may be an overmold member adapted to embed the electromagnetic coil, the part of the end portion of the wire and a part of the first member, thereby forming the insulating body. Alternatively, the first and the second members may be assembly parts adapted to engage into each other for forming the insulating body (28).

According to another advantageous embodiment, the connector terminal has two electrical contacts, the insulating body has two sleeves, and the wire that forms the electromagnetic coil has two end portions, which are respectively connected to the two electrical contacts. Each of the two end portions of the wire extends through a corresponding sleeve and through the housing to connect to each respective electrical contact.

In another advantageous embodiments, the core may be made of a magnetic material, the insulating body may be made of a non-magnetic insulating material, and the housing may be made of a thermoset material, respectively.

The electromagnetic actuator may further comprise an overmold adapted to embed at least part of the connector terminal, the fluid-tight seal and at least a part of the housing.

Consequently, the connector terminal and the overmold can be advantageously varied in size and shape to suit particular applications of the electromagnetic actuator, such as different tube assembly lengths, mounting configurations, electrical connectors, etc, while using the same assembly parts of housing, core and coil.

In addition, the overmold may also provide an additional fluid tightness among the embedded parts.

According to another advantageous embodiment, the present invention provides a method for producing an electromagnetic actuator, comprising the steps of enclosing a core and an electromagnetic coil in a housing, arranging a connector terminal on the housing, and extending an end portion of a wire that forms the electromagnetic coil

through the housing to the connector terminal, thereby electrically connecting the electromagnetic coil to the connector terminal.

The connector terminal may be mounted on an outer surface of the housing, and the end portion of the wire extended such that it protrudes out of the outer surface of the housing to connect to the connector terminal.

The method may further comprise the step of insulating the electromagnetic coil from the core with an insulating body, wherein the insulating body is adapted to enclose a winding of the electromagnetic coil and further comprises a sleeve adapted to enclose a part of the end portion of the wire, the end portion of the wire extending from the winding of the electromagnetic coil through the housing.

According to an advantageous embodiment, the method comprises a step of forming the housing with a through-hole, wherein the sleeve is comprised along one portion of a length of the through-hole and the step of extending comprising leading the end portion of the wire through the through-hole.

The method may comprise a step of arranging a fluid-tight seal in the through-hole for sealing a space between the sleeve and the outer surface of the housing. The step of arranging the fluid-tight seal may comprise dispensing silicone or filling a material suitable for preventing fluid leakage by potting in this space.

In another advantageous embodiment, the method comprises a step of forming the core as a hollow core extending along a longitudinal axis A and comprising a coaxial blind cavity adapted to house the insulating body and the electromagnetic coil.

In a further advantageous development of the invention, the method comprises a step of forming the insulating body such as to comprise a first member and a second member that complement each other, wherein each one of the first and the second members is adapted to accommodate the winding of the electromagnetic coil and comprises a complementary part of the sleeve of the insulating body.

According to an advantageous embodiment, the step of forming the insulating body comprises molding the first member such as to comprise a pocket adapted to house the winding of the electromagnetic coil and to further comprise a longitudinal part of the sleeve adapted to support the part of the end portion of the wire, the end portion of the wire extending from the winding of the electromagnetic coil through the housing,

mounting the electromagnetic coil on the first member, the mounting comprising winding the electromagnetic coil on the pocket of the first member and extending the part of the end portion of the wire from the winding of the electromagnetic coil and along the longitudinal part of the sleeve, and overmolding the second member over a part of the first member and the electromagnetic coil mounted on the first member, thereby enclosing the winding of the electromagnetic coil and the part of the end portion of the wire extended along the longitudinal part of the sleeve.

In an alternative embodiment, the step of forming the insulating body comprises molding the first member and the second member such as to be adapted to engage into each other, the first member being molded such as to comprise a pocket adapted to house the winding of the electromagnetic coil and to further comprise a longitudinal part of the sleeve adapted to support the part of the end portion of the wire, the end portion of the wire extending from the winding of the electromagnetic coil through the housing, mounting the electromagnetic coil on the first member, the mounting comprising winding the electromagnetic coil on the pocket of the first member and extending the part of the end portion of the wire from the winding of the electromagnetic coil and along the longitudinal part of the sleeve, and engaging the second member into the first member for forming the insulating body, thereby enclosing the winding of the electromagnetic coil and the part of the end portion of the wire extended along said longitudinal part of the sleeve.

In a further advantageous embodiment, the method further comprises a step of providing the connector terminal having two electrical contacts, wherein the step of forming the insulating body comprises forming two sleeves, wherein the step of extending comprises extending two end portions of the wire that forms the electromagnetic coil through the housing to the connector terminal, thereby electrically connecting each end portion of the wire to the respective electrical contacts, and wherein each of the two end portions of the wire extends through a corresponding sleeve and through the housing to connect to each respective electrical contact.

In another advantageous development of the invention, the method comprises a step of embedding at least part of the connector terminal, the fluid-tight seal and at least a part of the housing in an overmold.

The accompanying drawings are incorporated into and form a part of the specification for the purpose of explaining the principles of the invention. The drawings are not to be

construed as limiting the invention to only the illustrated and described examples of how the invention can be made and used.

BRIEF DESCRIPTION OF THE FIGURES

Further features and advantages will become apparent from the following and more particular description of the invention as illustrated in the accompanying drawings, in which:

Fig. 1 shows a perspective view illustrating a housing of an electromagnetic actuator and a connector terminal according to the invention;

Fig. 2 shows a cut-through diagram of the perspective view illustrated in figure 1 ;

Fig. 3 shows a perspective view similar to figure 2, with parts removed for illustrating the shape of the insulating body and the connection of the electromagnetic coil to the connector terminal;

Fig. 4 shows a perspective view of the electromagnetic actuator according to an embodiment of the invention, having a screw fitting for attaching the electromagnetic actuator to a second module (not shown) and an overmold covering part of the housing and part of the connector terminal;

Fig. 5 shows a cut-through diagram of the perspective view illustrated in figure 4.

DETAILED DESCRIPTION OF THE INVENTION

Advantageous embodiments of an electromagnetic actuator constituted according to the invention will now be described in further detail with reference to the accompanying drawings.

Figure 1 illustrates in a perspective view an electromagnetic actuator 1 according to the present invention.

The electromagnetic actuator 1 comprises a housing 10 and a connector terminal 12.

The housing 10 has a tubular shape extending through a longitudinal axis A from an upper end to a lower end. The housing 10 encloses a continuous passage between two coaxial opening ends that are perpendicular to the longitudinal axis A: an inlet opening

end 16 located at the upper end of the housing 10 and an outlet opening end 18 located at the lower end.

When the electromagnetic actuator is used in a fuel injector, the inlet opening end 16 is to be in fluid communication with a fuel rail (not shown) providing a supply of fuel and the outlet opening end 18 is to be connected to a second module forming the injector body (not shown).

Starting from the top, the housing 10 has an outer diameter at the inlet opening end 16 that is made smaller than an outer diameter of a substantial central part of the housing 10 and the outlet opening end 18. The inlet opening end 16 is adapted to the central part itself by an intermediate shoulder 10a orthogonal to the axis A. The shoulder 10a is set at a pre-defined distance from the inlet opening end 16 and provides a mounting or resting surface for the connector terminal 12. The shoulder 10a may be shaped on the outer surface of the housing with a mounting structure 10b providing a support for mounting the connector terminal 12 and shaped such as to fix the connector terminal 12 in a pre-defined position with respect to the housing 10. The mounting structure 10b may include an intermediate indentation that fits closely the width of the connector terminal 12, such as to fix mechanically the connector terminal 12 to the housing 10 by snapping the connector terminal 12 into the intermediate indentation.

The housing 10 further includes an external, coaxial flange 20 located at a pre-defined distance from the housing lower end for supporting a screw fitting or a ring-nut 46 (not shown). An outer seal ring 21 , such as an "O"-ring, is retained in an annular indent or groove 22, which is located at the lower end of the housing 10. The outer seal ring 21 serves for preventing fluid leakage when the electromagnetic actuator 1 is attached to the second member of the fuel injector by the screw-fitting 46 (not-shown).

The connector terminal 12 comprises at least an electrical terminal 13 or electrical pin adapted to connect directly to an outlet of an external energy source or control unit for controlling the electromagnetic actuator 1.

In the advantageous embodiment, the electrical terminal 13 has a pre-bent, continuous shape.

A first portion 13a of the electrical terminal 13 is adapted to provide a connection to an external outlet and is projected away from the longitudinal axis A of the electromagnetic actuator 1 , essentially along a diagonal direction.

A second portion 13b of the electrical terminal 13 extends transversally to the longitudinal axis A and parallel to the housing shoulder 1Oa ₁ providing a flat contact surface for mounting the electrical terminal 13 on the housing shoulder 10a. When the housing 10 includes the mounting structure 10b, the electrical terminal 13 is fixed to the housing 10 by snapping the second portion 13b in the indentation provided in the mounting structure 10b. The second portion 13b is adapted to surround partially the inlet opening end 16 of the housing 10 when the electrical terminal 13 is mounted.

A third portion 13c of the electrical terminal 13 is bent axially upwards with respect to the second portion 13b and supports a lateral connecting portion 13d adapted to provide an electrical connection to a wire emerging from the housing 10. The connecting portion 13d includes an essentially longitudinal through-hole adapted to receive the wire projected from the housing 10 for electrically connecting the wire to the electric terminal 13.

However, the shape of the electric terminal 13 is not limited to the above description and may be adapted to suit different configurations and sizes of the electromagnetic actuator 1 , such as the external shape of the housing 10 and the configuration of the outlet connector. In particular, the parts 13a, 13b and 13c may be bent with different orientation angles with respect to the longitudinal axis A. The connecting portion 13d may be omitted and the wire protruding out from the housing 10 directly soldered to the electric terminal 13. Alternatively, the electric terminal 13 may be a continuous slab that is bent into its final shape only after the electrical terminal 13 has been mounted on the housing 10. Alternatively, instead of bending, the shape of the electrical terminal 13 may be formed by fixing distinct parts of different shapes with different orientation angles.

The connector terminal 12 is also not limited in the number, shape or configuration of the electrical terminals comprised therein. In particular, the connector terminal 12 may comprise one, two or several electrical terminals.

In the advantageous embodiment illustrated in Fig. 1 , the connector terminal 12 comprises a second electrical terminal 14, whose shape is essentially a mirror projection along the longitudinal axis A of the electrical terminal 13. The electrical terminals 13 and

14 are shaped such as when mounted on the shoulder 10a or on the mounting structure 10b provided in the housing shoulder 10a, the respective first portions 13a and 14a of each terminal are separated at a distance from one another so that the connector terminal 12 is adapted to connect to an external outlet. The second portions 13b and 14b are adapted to partially surround the inlet opening end 16, respectively from each side, and the connecting portions 13d and 14d are separated at a distance adapted to allow the connection of a respective wire projected out from the housing 10.

The connector terminal 12 is then mounted on the outer surface of the housing 10, on the shoulder 10a or preferably on the mounting structure 10b on the exterior side of the housing 10, instead of a part of the connector terminal 12 being completely surrounded by or embedded in the housing 10 such as in conventional prior arts.

Figure 2 shows a cut-through diagram of the perspective view illustrated in figure 1.

The electromagnetic actuator 1 comprises a core 24, an electromagnetic coil 26 and an insulating body 28, which are arranged or assembled within the housing 10.

In an advantageous development of the invention, the electromagnetic coil 26 is housed in the core 24 that is made of a magnetic permeable material for providing a passage for the magnetic flux created by the electromagnetic coil 26.

As shown in Fig. 2, the housing 10 serves both the purpose of providing an inner, central channel for the passage of fluid and of assembling together the magnetic core 24, the electromagnetic coil 26, and the insulating body 28, maintaining their positions and relative orientations fixed. Preferably, the housing 10 is made of a thermosetting plastic or thermoset material that is molded into the desired form of the housing 10 by any method suitable for molding thermosets, such as reactive injection molding or compression molding. For applications requiring a magnetic insulation of the external body of the electromagnetic actuator 1 from the magnetic core 24, the housing 10 may be made of a non-magnetic insulating material suitable for providing a magnetic insulation as well as an electrical insulation.

The internal side of the housing 10 is shaped with a hollow that extends along the longitudinal axis A and has an internal diameter at the inlet opening end 16 adapted to a desired fluid conduct. The internal diameter of the housing 10 in enlarged at a predefined distance from the inlet opening end 16 until the lower end of the housing 10,

providing a coaxial cavity 10c adapted to enclose the magnetic core 24. The coaxial cavity 10c is defined with a diameter adapted to fit closely the shape of the magnetic core 24, surrounding the outer perimeter surface of the magnetic core 24. The coaxial cavity 10c adapts to the smaller internal diameter of the inlet opening 16 by an internal shoulder 1Od transverse to the axis A and which covers the upper part of the magnetic core 24.

In the embodiment illustrated in Fig. 2, the coaxial cavity 10c extends downwards beyond the core 24. At the lower end of the housing 10, a supporting ring 25 is arranged in the inner side of the housing 10 and after the magnetic core 24. The support ring 25 is preferably made of metal and is dimensioned such as to maintain the relative position of the core 24 inside the housing 10 when the electromagnetic actuator 1 is attached to the second member of the fuel injector (not shown).

In addition, the housing 10 includes at least a through-hole 1Oe that extends downward in parallel to the longitudinal axis A from the external shoulder 10a to the internal shoulder 1Od. The through-hole 1Oe provides a channel in the housing 10 for passing a part of a wire 36 that forms the electromagnetic coil 26 through the housing 10 as will be described later. However, other configurations of the trough-hole 1Oe can be envisaged, provided that the through-hole 10e is adapted to conduct a wire from the housing cavity 10c to the outer surface of the housing 10. In an advantageous embodiment, the housing 10 has two through-holes extending essentially in parallel through the housing 10, trespassing the internal shoulder 10d at right angles and separated by a pre-defined distance. Preferably, the housing 10 has no other external openings except for the through-holes provided for passing wires, the inlet 16 and outlet 18 opening ends.

The magnetic core 24 has a tubular shape with a central hollow that extends along the longitudinal axis A for allowing a fluid passage when the magnetic core 24 is arranged or assembled in the housing 10. The inner and outer diameter of the hollow magnetic core

24 and/or the housing cavity 10c can be defined so that when the magnetic core 24 is mounted on the housing 10, the inner diameters of the hollow core and of the inlet opening end 16 match each other, thereby defining a longitudinal fluid conduct of constant diameter. However, depending on the particular applications or design needs of the electromagnetic actuator 1 , other shapes or dimensions of the housing 10 and of the hollow magnetic core 24 can be envisaged. For instance, the inner diameters of the

hollow core 24 and of the inlet opening 16 may be different in order to provide a step for supporting a spring (not shown).

The magnetic core 24 further includes an internal cavity 30 for housing the electromagnetic coil 26.

The internal cavity 30 is preferably a blind cavity or pocket defined inside the magnetic core 24 by two longitudinal, adjacent walls that extend vertically and parallel to the wall of the hollow of the magnetic core 24. The depth and internal width of the blind cavity 30 are adapted to fit closely around part of the length of the insulating body 28, thereby ensuring that the winding of the electromagnetic coil 26 enclosed inside the insulating body 28 will be completely housed inside the magnetic core 24.

In the embodiment illustrated in Fig. 2, the blind cavity 30 opens towards the lower end of the housing 10. In addition, the magnetic core 24 further comprises a through-hole 31 (there are two according to the illustrated embodiment), starting from the bottom of the blind cavity 30 and traversing upwards the magnetic core 24. The position of the through-hole 31 in the magnetic core 24 is such as to coincide with the position of the channel constituted by the through-hole 1Oe of the housing 10 when the magnetic core 24 is arranged in the housing 10.

With reference to Figure 3, it will now be described in detail the electromagnetic coil 26, the insulating body 28, and the connection of the electromagnetic coil 26 to the connector terminal 12 according to the principles of the invention.

As mentioned before, known coil bobbins are conventionally provided with electrical terminals or pins mounted on the bobbin for connecting to an external outlet. The electrical terminals extend from the bobbin to the outside of the housing that encloses the coil and bobbin. The electromagnetic coil is generally soldered or welded to these electrical terminals before being assembled or mounted in the housing.

An advantageous embodiment of the present invention simplifies the connecting operation of the electromagnetic coil 26, by providing a connector terminal 12 that is completely external to the housing 10, and by extending an end portion 38 of a wire 36 that forms the electromagnetic coil 26 through the housing 10, preferably beyond the housing 10, to the external connector terminal 12. Hence, the electromagnetic coil 26 is

connected directly to the external connector terminal 12 using the wire 36 of the electromagnetic coil 26.

Since the present invention eliminates the need of electrical terminals mounted on the bobbin for connecting to an external source, the same parts constituting the unit of housing 10, magnetic core 24 and coil 26 can be advantageously used with or adapted to different types of connector terminals 12. In addition, the delicate operation of connecting the electromagnetic coil 26 to the connector terminal 12 is performed after the electromagnetic coil 26 and the magnetic core 24 have been assembled with each other and mounted in the housing 10.

As shown in Fig. 2, the electromagnetic coil 26 is preferably arranged in the coaxial internal cavity 30 provided in the magnetic core 24. In order to insulate electrically the electromagnetic coil 26 from the magnetic core 24, the electromagnetic coil 26 is enclosed or housed in the insulating body 28 and the unit coil/insulating body arranged in the magnetic core 24. The insulating body 28 can be made of any insulating material suitable for providing an electrical insulation such as a plastic.

The insulating body 28 is shaped so as to provide a support for the winding of the electromagnetic coil 26, functioning as a bobbin, and to provide a support for leading the end portion 38 of the wire 36 that forms the electromagnetic coil 26 away from the winding of the electromagnetic coil 26 through the housing 10.

As shown in Fig. 3, the insulating body 28 has an annular part 32 with an inner cavity for enclosing completely the winding of the electromagnetic coil 26. In addition, the insulating body 28 has an elongation or protuberant part forming a sleeve 34 that projects from the annular part 32 essentially at a right angle and extends along the longitudinal axis A. The sleeve 34 has a longitudinal hollow adapted to lead in its interior the end portion 38 of the wire 36 extending away from the winding of the electromagnetic coil 26.

The wire 36 that forms the electromagnetic coil 26 is wound inside the annular part 32 of the insulating body 28 and at least one of the extremities or end portions 38 of the coil wire 36 is extended away from the winding of the electromagnetic coil 26, essentially in a direction transverse to the winding, and is made to pass inside the sleeve 34 of the insulating body 28. The length of the end portion 38 of the wire 36 is adapted to cover at

least the distance from the end of the winding of the electromagnetic coil 26 to the outer surface of the housing 10, more specifically, to the housing shoulder 10a.

The shape of the annular part 32 of the insulating body 28 is adapted to match closely the blind cavity 30 of the magnetic core 24 in which the insulating body 28 carrying the electromagnetic coil 26 will be mounted.

The position and length of the sleeve 34 are such that the sleeve 34 coincides with the through-hole 31 of the magnetic core 24 and traverses completely the through-hole 31 when the insulating body 28 is arranged in the magnetic core 24. The longitudinal dimension of the sleeve 34 is at least the length of the through-hole 31 in the magnetic core 24 that it traverses in order to ensure the electrical insulation of the part of the end portion 38 of the magnet wire 36 that extends along the magnetic core 24. In an advantageous embodiment, the length of the sleeve 34 is such that when the insulating body 28 is arranged in the magnetic core 24, the sleeve 34 passes beyond the magnetic core 24 and penetrates partially in the through-hole 1Oe of the housing 10.

The relative positions of the sleeve 34, of the through-hole 31 in the magnetic core 24 and of the through-hole 1Oe in the housing 10 are such that they coincide with each other when the insulating body 28, the magnetic core 24 and the housing 10 are assembled together.

The cross-sections of the sleeve 34 and of the through-hole 31 may be defined such that they closely match each other. The inner and outer walls of the sleeve 34 are an extension of the inner and outer walls of the annular part 32, the radial width of the sleeve 34 being essentially equal to the radial width of the annular part 32.

The part of the end portion 38 of the wire 36 emerging from the sleeve 34 is led through the through-hole 10e to the outer surface 10a of the housing 10. In order to prevent fluid leakages from the fluid passageway to the through-hole 10e of the housing 10 and into the electromagnetic coil 26, a void space defined by the region between the end of the sleeve 34 that penetrates in the through-hole 10e and the outer surface of the housing 10 is sealed by a fluid-tight seal 39. The fluid-tight seal 39 is set in this void space and surrounds the wire that traverses the void space. The fluid-tight seal 39 may be a dispensed silicone with a shape that matches closely the void space of the through-hole 10e or by filling the void space with a material that prevents fluid leakage.

In order to reduce the cross-section of the void region in the through-hole 1Oe to be sealed, the part of the sleeve 34 that penetrates the housing 10 can be made with a smaller cross-section with respect to the part of the sleeve 34 that passes through the magnetic core 24. For instance, the width of the sleeve 34 along the perimeter of the annular part 32 may be reduced while maintaining constant the radial width of the sleeve 34. In this configuration, the cross-section of the housing through-hole 1Oe, which is adapted to fit closely the cross-section of the part of the sleeve 34 that penetrates the housing 10, is made smaller than the cross-section of the through-hole 31 in the magnetic core 24.

The part of the end portion 38 of the wire 36 that is projected to the outer surface of the housing 10 is led into the connecting portion 13d of the electrical terminal 13 and is made to penetrate the hollow of the connecting portion 13d. The wire can be electrically connected to the connecting portion 13d by means of any methods known in the art, such as by soldering or by applying a suitable mechanical pressure in the connecting portion 13d for fixing the wire, thereby connecting electrically the electromagnetic coil 26 to the electrical terminal 13.

The insulating body 28 comprises two coaxial pieces or members: an inner, first member 28a and an outer, second member 28b. Each member comprises a portion of the annular part 32 and a complementary part of the sleeve 34 of the insulating body 28. The second member 28b forms essentially the outer surface of the insulating body 28 and surrounds the first member 28a, which forms essentially the inner surface of the insulating body 28.

In an advantageous embodiment, each of the first 28a and second 28b members are made of a thermoplastic material and shaped into its final form by injecting the thermoplastic into respective molds (not shown) that have the complementary shape of the final shape of the respective first 28a and second 28b members.

The first member 28a is formed with a pocket defined along the perimeter of the outer surface of the annular part for carrying the winding of the electromagnetic coil 26, and formed with a longitudinal part of the sleeve 34 adapted to support a part of the end portion 38 of the wire 36, this part starting from the winding of the electromagnetic coil 26. In this configuration, the end portion 38 of the wire 36 that extends through the housing 10 is carried inside the sleeve 34 along a pre-defined length.

The electromagnetic coil 26 is then mounted on the first member 28a by winding the magnet wire 36 around the annular shaped part of the first member 28a, thereby accommodating the winding of the electromagnetic coil 26 inside the pocket. The end portion 38 of the magnet wire 36 is extended along the longitudinal part of the sleeve 34 formed in the first member 28a.

The second member 28b is then directly molded over the first member 28a and the mounted electromagnetic coil 26 for forming a monolithic unit of the insulating body 28 and the electromagnetic coil 26, thereby enclosing the winding of the electromagnetic coil 26 and the part of the end portion 38 of the wire 36 extended along the longitudinal part of the sleeve 34 inside the insulating body 28.

Alternatively, the first 28a and the second 28b members may be two assembly parts that are pre-shaped or molded into its final form prior to the mounting operation of the electromagnetic coil in the first member 28a. Each of the first member 28a and second member 28b includes an inner pocket formed in the annular part 32 and a complementary part of the sleeve 34. The pockets are shaped such as to form a cavity adapted to enclose or to surround the electromagnetic coil 26 when the first 28a and second 28b members are assembled together.

In this case, the first 28a and the second 28b members are held together by a detent member or locking projection for forming the insulating body 28. The first member 28a includes a locking projection that engage an engagement or receiving indentation included in the second member 28b for securing the first 28a and second 28b members together.

Preferably, two locking projections are provided in the first member 28a. A first locking projection is set along an inner perimeter at a predefined distance from the lower end of the first member 28a, and set before the pocket that retains the electromagnetic coil 26. A second locking projection is set on the opposite side of the pocket and along an inner perimeter of the first member 28a, being only interrupted in the region between the pocket and the sleeve 34, since this region is traversed by the end portion 38 of the wire 38 extending away from the electromagnetic coil 26 through the sleeve 34. The respective complementary indentations are provided in the second member 28b.

However, other joining methods such as ultrasonic welding, adhesives and heat staking may also be used to couple the second member 28b and the first 28a members together instead of using the locking projection.

In the embodiment illustrated in Fig. 3, the insulating body 28 comprises two sleeves 34, 35 of a similar shape and projected upwards in parallel from the annular part 32 and at a maximum separation distance for leading separately two extremities 38, 37 of the magnet wire 36 that forms the electromagnetic coil 26 through the housing 10.

Consequently, the electromagnetic actuator 1 may be provided in a modular assembly that can be mounted and tested separately, and then connected together to a second module (not shown) for forming a fuel injector.

Figs. 4 and 5 illustrate an electromagnetic actuator according to an embodiment of the invention.

Referring to Fig. 4, according to an advantageous embodiment the electromagnetic actuator 1 includes an overmold 40 made of a plastic material, such as a thermoplastic, that is molded directly over the housing 10 and the connector terminal 12, and covers a part of the housing 10 and a part of the connector terminal 12 of the electromagnetic actuator 1.

As shown in Fig. 5, the overmold 40 maintains the relative orientation and position of the assembly unit comprised of the housing 10, the connector terminal 12, the fluid-tight seal 39 and a part 38a of the end portion 38 of the electromagnetic coil wire 36 that is projected outside the housing 10.

The overmold 40 provides a structural case for the body of the electromagnetic actuator 1 as well as predetermined electrical and thermal insulating properties. In particular, the overmold 40 provides an electrical insulation of the part 38a of the end portion 38 of the wire 36 comprised between the outer surface of the housing 10 and the connecting portion 13d of the electrical terminal 13. In addition, since the assembly unit comprised of the housing 10, connector terminal 12 and fluid tight-seal 39 are embedded in the plastic material, the required fluid tightness may be reinforced and the number of fluid sealing gaskets or O-rings between assembled parts may be reduced.

Furthermore, a separate collar (not shown) can be connected on the overmold 40, e.g., by bonding, and can provide an application specific characteristic such as an orientation

feature or an identification feature for the electromagnetic actuator 1. Thus, the overmold 40 provides a universal arrangement that can be modified with the addition of a suitable collar.

Referring to Fig. 5, on an upper part, the overmold 40 is molded with an overmold inlet opening 44, coaxial to the inlet opening 16 of the housing 10, for allowing the passage of fluid. The outer and internal diameters of the overmold inlet opening 44 are sized for adjusting the electromagnetic actuator 1 to a fluid intake (not shown).

On a lower part, the overmold 40 is molded so as not to cover the full length of the housing 10.

The overmold 40 can also form an electrical harness connector portion 42 in which a part of the connector terminal 12 is exposed, more specifically, the portion 13a of the electrical terminal 13. The connector terminal 12 and the electrical harness connector portion 42 can engage a mating connector or outlet, such as part of a vehicle wiring harness (not shown), to facilitate connecting the electromagnetic actuator 1 to a supply of electrical power (not shown) for energizing the electromagnetic coil 26.

As such, the connector terminal 12 and overmold 40 (or collar, if used) can be varied in size and shape to suit particular applications and configurations of the electromagnetic actuator 1 , such as tube assembly lengths, mounting configurations, and electrical connectors, while using the same housing 10, core 24, bobbin 28 and coil 26 units, thereby reducing manufacturing and inventory costs of the electromagnetic actuator 1.

In an advantageous embodiment, the electromagnetic actuator 1 comprises a screw- fitting or ring-nut 46 for attaching the electromagnetic actuator 1 to a second part or module carried by the injector body (not shown). In this configuration, the overmold 40 does not extend over the full length of the housing 10. The lower part of the housing 10 that includes the flange 20 for supporting the screw-fitting 46 and the screw-fitting 46 are left uncovered by the overmold 40.

Alternatively, as a person skilled in the art would readily recognize, the electromagnetic actuator 1 can be modified for being attached by any other attachment processes.

According to the principles of the invention, the electromagnetic actuator 1 can be constructed as follows.

The first member 28a of the bobbin 28 is molded with a shape that provides a housing or casing that fits closely the winding part of the electromagnetic coil 26 and a longitudinal part of the sleeve 34 used for leading the extended end portion 38 of the electromagnetic coil wire 36. The wire of the electromagnetic coil 26 is wound around the first part 28a of the plastic bobbin 28, and a terminal portion 38 of the wire 36 is extended along the part of the sleeve 34 included in the first member 28a. The first member 28a and the mounted coil 26 are then placed inside a suitable mold (not shown), and the second member 28b is molded directly by injecting a thermoplastic over the inner face of the first member 28a and the mounted electromagnetic coil 26, thereby molding directly the second member 28b, and consequently the insulating body 28, into their final shapes.

Alternatively, the second member 28b of the insulating body 28 may be obtained by injecting directly a thermoplastic into a mold, whose shape complements the shape of the first member 28a. The pre-molded second member 28b is then fitted or placed over the first member 28a and the mounted electromagnetic coil 26, thereby enclosing the electromagnetic coil 26 and an intermediate part of the end portion 38 of the wire 36 that passes inside the sleeve 34.

The completed bobbin 28 enclosing the electromagnetic coil 26 is then assembled into the internal cavity 30 of the magnetic core 24 at a proper orientation for allowing the sleeve 34 to be inserted in the through-hole 31 of the magnetic core 24. The housing 10 is then placed over the assembly group constituted of the magnetic core 24, the insulating body 28 and the electromagnetic coil 26 and orientated such as the position of the sleeve 34 emerging from the though-hole 31 of magnetic core 24 coincides with the through-hole 1Oe.

The end portion 38 of the wire 36 emerging from the sleeve 34 is then led through the trough-hole 1Oe. The void region of the through-hole 1Oe that is trespassed by the end portion 38 of the wire 36 is sealed with a fluid-tight seal 39 for preventing fluid leakages between the housing and the bobbin 30. The fluid-tight seal 39 also helps to prevent fluid leakages into the electromagnetic coil 26 through the sleeve 34. The fluid-tight seal 39 may be provided as a dispensed silicone by filling the void space with fluid silicone that adjusts perfectly the void region or made of any material suitable for preventing fluid leakages that can be filled in the void region by potting.

The terminal part 38a of the end portion 38 of the wire 36 projected beyond the housing through-hole 1Oe is made to pass through the connecting part 13d of the electric terminal 13 mounted on the mounting structure 10b on the exterior side of the housing 10.

In case the connector terminal 12 comprises two electrical terminals 13 and 14, the electric terminals are pre-bent to a proper configuration and mounted such that the pre- aligned terminals 13 and 14 are in alignment with the harness connector 42. The harness connector 42 is then formed when a polymer is poured or injected into a mold (not shown).

The housing 10, connector terminal 12, fluid-tight seal 39, and the part 38a of the end portion 38 of the coil wire 36 extending between the housing 10 and the connector terminal 12 are then assembled together and inserted into a mold (not-shown) for injecting a thermoplastic that embeds the assembly parts and forms the overmold 40.

However, in an advantageous embodiment, the overmold 40 may be formed of two separable parts that are assembled over the housing 10, the fluid-tight seal 39, the connector terminal 12 and the part 38a of the end portion 38 of the coil wire 36.

Although some embodiments were described in view of the application of the electromagnetic actuator 1 to the field of fuel injectors, other applications of the electromagnetic actuator 1 may be readily envisaged by a person skilled in the art.

REFERENCE SIGNS

Reference Signs Description

1 Electromagnetic actuator

10 Housing

10a Housing shoulder

10b Mounting structure

10c Coaxial cavity

1Od Internal shoulder

10e Through-hole in housing

12 Connector terminal

13, 14 Electrical terminal

13a Electrical terminal first portion

13b Electrical terminal second portion

13c Electrical terminal third portion

13d, 14d Electrical terminal connecting portion

16 Inlet opening end

18 Outlet opening end

20 Coaxial flange 22 Annular groove

21 Outer seal ring

24 Magnetic core

25 Support ring

26 Electromagnetic coil 28 Insulating body 8a Inner member 8b Outer member

30 Blind cavity in core

31 Through-hole in core

32 Annular part of insulating body 34, 35 Sleeve

36 Electromagnetic coil wire

38, 37 Extended end portion of wire

38a Terminal part of the end portion of wire

Fluid-tight seal

Overmold

Harness connector

Overmold inlet opening

Screw-fitting opening