Patent Application
20150345442
This disclosure relates to fuel injectors including an injection control valve having a stator.
Solenoid actuated fuel injectors are one type of fuel injector used to supply fuel to a combustion chamber of an internal combustion engine. Such fuel injectors are relatively efficient to manufacture, have proven reliability, and are widely available. One characteristic of such fuel injectors is the time it takes to energize and de-energize an actuator that controls a fuel injection event.
Embodiments of this disclosure include a fuel injector having an injector body and an injection control valve. The injection control valve is positioned in the injector body and includes a stator housing and a stator core. The stator housing includes a first stator housing portion, and at least one of an inner stator housing portion extending longitudinally from the first stator housing portion and an outer stator housing portion extending longitudinally from the first stator housing portion. The stator core includes a first annulated wall having an inner surface, a second annulated wall having an outer surface, a radially extending wall connecting the first annulated wall to the second annulated wall and including an exterior surface, a radially extending slot extending through the first annulated wall, the radially extending wall, and the second annulated wall, and an annular coil assembly positioned between the first annulated wall and the second annulated wall. The stator core is positioned on the stator housing and includes an electrically insulating material separating the radially extending wall exterior surface from the stator housing, and separating at least one of: the first annulated wall from the inner stator housing portion along an extent of the first annulated wall; the second annulated wall from the outer stator housing portion along an extent of the second annulated wall; and the second annulated wall from the injector body along the extent of the second annulated wall.
Embodiments of this disclosure also include a fuel injector having a fuel injector body, a stator housing, and a stator core. The stator housing is positioned in the fuel injector body. The stator core is positioned in the fuel injector body and includes an inner surface, an outer surface, a radially extending slot extending from the inner surface to the outer surface, and an annular coil assembly positioned on the stator core between the inner surface and the outer surface. The stator core is positioned to contact only one of: the stator housing at only one azimuthal location on the inner surface; the stator housing at only one azimuthal location on the outer surface; the fuel injector body at only one azimuthal location on the outer surface; and the stator housing at only one azimuthal location on the transversely extending surface.
Embodiments of this disclosure also include a method of reducing an eddy current in a fuel injector. The method includes positioning a stator housing and a stator core in a fuel injector body of the fuel injector, the stator core including a slot extending radially through the stator core from an inner surface of the stator core through an outer surface of the stator core. The method further comprises positioning the stator core to place the stator core in contact with only one of: the stator housing at only one azimuthal location on the inner surface; the stator housing at only one azimuthal location on the outer surface; the fuel injector body at only one azimuthal location on the outer surface; and the stator housing at only one azimuthal location on the transversely extending surface.
Advantages and features of the embodiments of this disclosure will become more apparent from the following detailed description of exemplary embodiments when viewed in conjunction with the accompanying drawings.
Rising or falling magnetic fields in electrically conductive parts of an actuator of a fuel injector may create eddy currents in the actuator, increasing the time it takes to fully open and close a nozzle or needle valve element of the fuel injector, which may lead to non-optimized fuel delivery to the combustion chamber of an engine. Fuel injectors according to embodiments of the present disclosure may facilitate reduction of such eddy currents, which may shorten the time for magnetic flux density to rise when the actuator of the fuel injector is energized, which may cause the nozzle or needle valve element to fully open faster than in conventional fuel injectors. Additionally, this decrease in eddy currents also may cause the actuator to de-energize more quickly than in a conventional fuel injector, which may cause the nozzle or needle valve element to fully close faster than in conventional fuel injectors.
Referring to
Fuel injector 18 includes an injector body 28, an injection control valve assembly 30, a nozzle module 32 and a longitudinal axis 34. In embodiments, the structural and functional details of fuel injector 18 may be similar to those are disclosed in U.S. Pat. Nos. 5,676,114, 6,155,503, and 7,156,368, the entire contents of which are hereby incorporated by reference. Injector body 28 may include an outer housing 36, which secures injection control valve assembly 30, nozzle module 32, and other elements of fuel injector 18 in a fixed relationship, and a valve housing 38. Valve housing 38 includes a valve cavity 40 for receiving injection control valve assembly 30. Injection control valve assembly 30 is adapted to receive a control signal from a controller (not shown) to energize, which causes nozzle module 32 to permit fuel flow into combustion chamber 26. Injection control valve assembly 30 includes valve housing 38 having valve cavity 40 formed by a valve housing interior surface 42, and a fuel injector control valve 44 positioned within valve cavity 40.
Referring now to
Stator housing 52 includes a first portion 64 and a second, inner stator housing portion 66 extending longitudinally therefrom. As best seen in
As shown in
According to embodiments, electrically insulating material 82 may be an epoxy applied to the inner surface 70 of first annulated wall 68 (or a portion thereof) and to the exterior surface 78 of radially extending wall 76 (or a portion thereof). For example, electrically insulating material 82 may be applied to every portion of inner surface 70 and every portion of exterior surface 78 that could provide a path for electrical current to stator housing 52 when stator core 54 is positioned on stator housing 52. That is, in embodiments, electrically insulating material 82 may be applied to all longitudinally extending locations on inner surface 70 that are adjacent to a surface of stator housing 52 and all radially extending locations on exterior surface 78 that are adjacent to a surface of stator housing 52. As shown in
Referring now to
In embodiments, electrically insulating material 82 may be an epoxy applied to the inner surface 70 of first annulated wall 68 (or a portion thereof), to the exterior surface 78 of radially extending wall 76 (or a portion thereof), and to the outer surface 74 of second annulated wall 72 (or a portion thereof). For example, electrically insulating material 82 may be applied to every portion of inner surface 70, outer surface 74, and exterior surface 78 that could provide a path for electrical current to stator housing 102 when stator core 54 is positioned on stator housing 102. This may include, in embodiments, all longitudinally extending locations on inner surface 70 that are adjacent to a surface of stator housing 102, all radially extending locations on exterior surface 78 that are adjacent to a surface of stator housing 102, and all longitudinally extending locations on outer surface 74 that are adjacent to a surface of stator housing 102. To verify the efficacy and integrity of the electrically insulating material 82, a hi-pot test may be performed on a subassembly that includes stator housing 102, stator core 54, and electrically insulating material 82, prior to installation of the subassembly in fuel injector 18.
Referring now to
In embodiments, electrically insulating material 82 may be an epoxy applied to the inner surface 70 of first annulated wall 68 (or a portion thereof), to the exterior surface 78 of radially extending wall 76 (or a portion thereof), and to the outer surface 74 of second annulated wall 72 (or a portion thereof). That is, for example, electrically insulating material 82 may be applied to any portion of inner surface 70, outer surface 74, and exterior surface 78 that could provide a path for electrical current to stator housing 114 or to injector body 120 when stator core 54 is positioned on stator housing 114. In embodiments, electrically insulating material 82 may be applied at all longitudinally extending locations on inner surface 70 that are adjacent to a surface of stator housing 114, all radially extending locations on exterior surface 78 that are adjacent to a surface of stator housing 114, and all longitudinally extending locations on outer surface 74 that are adjacent to a surface of injector body 120. In embodiments, to verify the efficacy and integrity of the electrically insulating material 82, a hi-pot test may be performed on a subassembly that includes stator housing 114, stator core 54, and electrically insulating material 82, prior to installation of the subassembly in fuel injector 18.
While the embodiments of
Providing electrically insulating material 82, as described in various embodiments, may prevent formation of eddy currents in the stator cores of the various embodiments. These eddy currents may delay the transition of control valve member 46 between the closed and open positions and the open and the closed positions. In embodiments, the addition of insulating material at locations as described herein, may decrease the transition time between the closed and open positions by approximately 50%, which may improve control of fuel into combustion chamber 26.
According to embodiments, limiting contact between the stator core and the stator housing, fuel injector body, and/or valve housing, to only one azimuthal or circumferential location on the stator core also may provide similar advantages, since such contact at one azimuthal or circumferential location keeps all other annulated surface portions or azimuthal locations of the stator core a spaced distance from the injector body and the stator housing and keeps the stator core electrically isolated at all annulated surface portions or locations on the fuel injector body and the stator housing, except at the contact location. In this manner, because the contact location is at one azimuthal location, no electrical path exists which would allow eddy currents to circumvent slot 80. Referring to
The contact at the azimuthal location may be a relatively small area, such as a single non-linear contact location shown at third azimuthal location 128, which may be described as a point contact though the actual contact area is physically larger than a literal point. The contact at the azimuthal location may be a longitudinally extending contact, such as shown at second azimuthal location 126 and which may be described as a continuous, longitudinally extending line. The contact at the azimuthal location may be a plurality of contact points, which may be a plurality of non-linear contact locations, extending longitudinally or axially along either inner surface 70 or outer surface 74, as shown at first azimuthal location 124. According to embodiments, these contact points may prevent an electrical circuit from being formed from a first portion 130 that is on a first side of radially extending slot 80 to a second portion 132 that is on a second side of radially extending slot 80. Such circuit may allow the flow of eddy currents around slot 80, thereby mitigating various benefits facilitated by embodiments of the present disclosure. Thus, in embodiments, contact may be permitted at only one azimuthal location on stator core 54. It should be apparent and understood that bias force 122 may be applied in any one or more of a number of azimuthal locations, and the locations shown in
Referring to
In embodiments, the protrusion 216 may be linear. In embodiments, the protrusions 218 may be a series of protrusions 218. Such contact may tend to tip stator core 200, which may create contact points at other locations on stator core 200. To maintain the position of stator core 200 with respect to the stator housing or the fuel injector body, an adhesive may be applied to inner surface 210, outer surface 214, and transversely extending surface 212, as appropriate to the embodiment, and stator core 200 may be held in position until the adhesive dries or cures, which would thus fix the position of stator core 200. In embodiments, the adhesive may be the epoxy described above. In embodiments, to hold stator core 200 in place, a non-electrically conductive shim may be used to wedge stator core 200 against one of the annulated surfaces of stator housing 52, 102, or 114, or against injector body 120.
While various embodiments of the disclosure have been shown and described, it is understood that these embodiments are not limited thereto. The embodiments may be changed, modified and further applied by those skilled in the art. Therefore, these embodiments are not limited to the detail shown and described previously, but also include all such changes and modifications.
