Patent Application
20110168813
The present disclosure relates generally to solenoid actuators, and relates more particularly to channeling a magnetic flux and a structural load through a compound armature housing in a single-pole solenoid actuator assembly.
A wide variety of solenoid actuators and solenoid actuated devices are known in the electromechanical arts. Solenoid actuators may be broadly classified as having dual-pole or single-pole solenoids. In most dual-pole solenoid designs, an armature is spaced at an axial air gap with a stator having a coil embedded therein. Dual-pole solenoids are often identified by an armature diameter that is about the same or greater than an outer diameter of the coil winding of the stator. When the coil in a dual-pole solenoid is energized, magnetic flux is generated around the coil, and flux lines pass through the stator, to the armature and back to the stator. The resulting flux path produces a pair of magnetic north and magnetic south poles between the stator and armature on each side of the axial air gap. The flux between these poles is generally parallel to the armature motion. These opposite poles produce a force on the armature that tends to move it toward the stator and coil to accomplish some task, such as opening or closing a valve.
In a typical single-pole solenoid, the magnetic flux path also encircles the coil and passes through the stator, the armature and back to the stator. The resulting flux path also produces a pair of magnetic north and south poles between the stator and the armature. In contrast to dual-pole configurations, the flux path between the poles is parallel to armature motion for one set of poles, and perpendicular to armature motion for the other set of poles. The perpendicular portion of the flux path may traverse a sliding radial air gap between the armature and another electromagnetic component that is present to complete the magnetic circuitry. Single-pole solenoids are often identified by an armature diameter that is smaller than the inner diameter of the coil winding of the stator. Due at least in part to manufacturing considerations, the additional electromagnetic component that is present in single-pole solenoids is often not a part of the stator itself. Rather, it is generally in contact with or positioned very close to the stator. The extra electromagnetic component is also typically stationary, hence the description of the air gap between this extra component and the armature as a “sliding radial air gap.” Single-pole solenoids remain preferred in certain applications.
The extra electromagnetic component mentioned above is often referred to as a magnetic flux ring. It is common to use materials such as iron and silicon iron to form the flux ring component. While such flux rings have worked well in certain designs, they are often associated with leakage of magnetic flux out of the desired flux path. In addition, because such flux rings are typically made of materials that are not only magnetically conductive, but also electrically conductive, eddy currents can form within the flux ring. The eddy currents create magnetic fields resisting the pull-in force on the associated armature when the solenoid is energized. Certain designs have been proposed to address these issues. Among them is the proposal to form slots in the flux ring to create longer path lengths for eddy currents to travel. As a result, the magnetic fields generated by the eddy currents may be relatively weaker. While these strategies have seen some success, there remains room for improvement.
In one aspect, a solenoid actuated device includes an actuator body including a first body piece having a first clamping surface, a second body piece having a second clamping surface, and a clamping mechanism which includes a release state and a clamping state. The solenoid actuated device further include a single-pole solenoid actuator assembly positioned at least partially within the actuator body and including a stator, an armature movable relative to the stator, and a movable member coupled with the armature. The single-pole solenoid actuator assembly further includes a-one-piece compound armature housing having a load carrying component clamped between the first clamping surface and the second clamping surface, and a flux carrying component supported by the load carrying component and defining a sliding air gap with the armature. The load carrying component includes a high structural strength and a low flux permeability, and the flux carrying component includes a low structural strength and a high flux permeability.
In another aspect, a method of making a solenoid actuated device includes establishing a magnetic flux path for a single-pole solenoid actuator at least in part via placing an armature at an axial air gap with a stator, and placing the armature at a sliding radial air gap with a flux carrying component of a one-piece compound armature housing. The method further includes establishing a structural load path for the single-pole solenoid actuator at least in part via placing a load carrying component of the one-piece compound armature housing between a first actuator body piece and a second actuator body piece. The method further includes clamping the one-piece compound armature housing between the first actuator body piece and the second actuator body piece.
In still another aspect, a method of operating a single-pole solenoid actuated device includes supporting a stator, an armature and a one-piece compound armature housing of a single-pole solenoid actuated device, within an actuator body. The method further includes supporting a flux carrying component of the one-piece compound armature housing with a load carrying component of the one-piece compound armature housing. The method further includes channeling magnetic flux across a sliding air gap between the flux carrying component and the armature, and channeling a clamping load between a first actuator body piece and a second actuator body piece through the load carrying component of the one-piece compound armature housing.
Referring to
Actuator body 12 may further include a third body piece 58 wherein an outlet check 88 of fuel injector 10 is positioned. Outlet check 88 may include a conventional needle check configured to move between a closed position and an open position to fluidly connect one or more nozzle outlets 59 with fuel inlet 56 in a known manner. Control valve mechanism 54 may include a check control valve member 86 such as a ball valve. Valve member 86 may be movable in response to moving movable member 29 via actuating single-pole solenoid actuator assembly 24, again in a known manner.
In one embodiment, first body piece 14 may include a stator housing, and second body piece 18 may include a valve body. Third body piece 58 may include a nozzle body having one or more nozzle body components which define nozzle outlet 59. As further described herein, selection of materials for certain of the components of fuel injector 10, as well as forming certain components with particular geometries, is contemplated to provide a fuel injector or other solenoid actuated device having robust magnetic and structural properties.
To this end, actuator assembly 24 may further include a one-piece compound armature housing 30 having a load carrying component 32 and a flux carrying component 34 supported by load carrying component 32 within actuator body 12. Flux carrying component 34 may define a sliding air gap 36 with armature 28. Load carrying component 32 and flux carrying component 34 may have different structural, magnetic and electrical properties. In one embodiment, load carrying component 32 may include a high structural strength and a low flux permeability, whereas flux carrying component 34 may have a low structural strength and a high flux permeability. Load carrying component 32 may also include a relatively low electrical resistivity, whereas flux carrying component 34 may have a relatively high electrical resistivity, the significance of which will be apparent from the following description. It should be appreciated that the various properties of the respective components such as flux permeability may vary based on part geometry and/or operating characteristics of the associated system. For instance, variance in factors such as electrical current or voltage used in energizing solenoid actuator assembly 24, or changes in part location, dimensions or shape, may result in changes in the observed flux permeability of flux carrying component 34 or load carrying component 32. Load carrying component 32 may be formed, for example, from a relatively hard, relatively non-magnetic material such as stainless steel. Flux carrying component 34 may be formed from a relatively soft, relatively highly magnetic material such as a powder material comprised of iron particles coated with a non-conducting material. Suitable materials for forming flux carrying component 34 are available, for example, under the trade name Somaloy®. As used herein, it should be understood that the terms “relatively non-magnetic” and “relatively highly magnetic” refer to electrically induced magnetism as opposed to permanent magnetism.
It has been discovered that certain materials, such as those used for flux carrying component 34 in a practical implementation strategy, tend to be poorly suited for carrying loads, at least when used in certain types of devices. Such materials tend to crumble if subjected to repeated impacts with other components of an associated system, and can structurally fail or deform if subjected to loads. As will be further apparent from the following description, the configuration of one-piece compound armature housing 30 addresses these and other concerns.
Referring now also to
Actuator body 12 may further include a fuel injector cap 64 having a third clamping surface 66 contacting second stator housing end 62 such that first body component/stator housing 14 is clamped between fuel injector cap 64 and compound armature housing 30. In one embodiment, clamping mechanism 22 may include a first set of threads 68 which may be external threads located on fuel injector cap 64, and a second set of threads which may be internal threads 70 located on second body piece 18. In other embodiments, clamping mechanisms other than cooperating internal and external threads might be used. Moreover, rather than locating threads 68 and 70 on the body pieces shown in
In one embodiment, compound armature housing 30 may be configured to serve further functions beyond those of a flux carrier and a structural load carrier. To this end, compound armature housing 30 may define a longitudinal axis A and include an outer radial surface 38 and an inner radial surface 40 defining a guide bore 42 for movable member 29. Referring also to
Referring in particular to
In one embodiment, a one-piece compound element having a flux carrying component of Somaloy® or a similar material, and a carrier component of steel, silicon iron, or the like, such as compound armature housing 30, may be made by a process of insert molding. As mentioned above, suitable materials for forming flux carrying component 34 may include a powder of relatively highly magnetic particles, each of which is encased in a non-conductive material. Engineers have found it challenging to form such materials into parts having sufficient structural integrity to withstand the relatively harsh operating environments of a solenoid actuator. As further described herein, insert molding such materials in a carrier component has been discovered to provide a practical implementation strategy for leveraging desirable magnetic properties, while overcoming the sometimes undesirable structural properties.
In certain instances, following pressing, exposed surfaces of the flux carrying component might be ground or otherwise machined to render the compound part having desired dimensions, surface shape, and surface finish. In other instances, machining may not be required. Other solenoid actuator components for which the use of magnetic particles coated with non-conductive material is considered advantageous, such as stators and armatures, may be made by a similar insert molding process.
Once compound armature housing 30 is made, it may then be assembled with other components of fuel injector 10. In particular, compound armature housing 30 may be placed within second body component 18 with spacer 48 located between first axial segment 32 and second clamping surface 20, as shown in
Other components of actuator assembly 24 may then be positioned within second body component 18. In particular, stator 26 may be positioned in first body component/stator housing 14, then the assembly of first body component 14 and stator 26 and possibly other components may be placed in second body component 18. Positioning the assembly of first body component 14 and stator 26 within second body component 18 may include placing stator at axial air gap 72 with armature 28, and may also be understood as establishing a magnetic flux path P1. Positioning the subject assembly may also be understood as establishing a structural load path P2 for actuator assembly 24. With the components positioned as described, first clamping surface 16 may contact load carrying component 32, and spacer 48 may be positioned in contact with each of first axial segment 42 and second clamping surface 20. A stop 31 may be positioned to limit travel of movable member 29. Fuel injector cap 64 may then be coupled with second body component 18 by engaging cooperating threads 68 and 70, until third clamping surface 66 contacts axial end 62 of first body component 14, and a clamping load applied.
In certain embodiments it may be desirable to magnetically isolate compound armature housing 30 from second actuator body piece 18. Placing compound armature housing 30 at radial air gap 50 and at radial air gap 52 will position compound armature housing 30 such that it does not contact second body piece 18 at all, at least in certain embodiments. Accordingly, radial air gap 50 may prevent magnetic flux from being channeled through load carrying component 32 and into second body piece 18. This avoids losing flux to actuator body 12 which would otherwise be available to impart a pull-in force on armature 28 when solenoid 90 is energized. It will be recalled that first radial air gap 50 may be larger, for example, radially thicker, than second radial air gap 52. This design feature limits the likelihood of contact occurring between second body piece 18 and first axial segment 34, since contact would be more likely to occur, if at all, between second axial segment 46 and second body piece 18. In other words, the relatively tighter clearance between second axial segment 46 and second body piece 18 than between first axial segment 44 and second body piece 18 will tend to inhibit inadvertent positioning of first axial segment 44 in contact with second body piece 18, and thus inhibit the channeling of magnetic flux through first axial segment 44 and into second body piece 18.
Referring to the drawings generally, operating a single-pole solenoid actuated device such as fuel injector 10 may include supporting stator 26, armature 28 and compound armature housing 30 within actuator body 12. Load carrying component 32 may support flux carrying component 34 within actuator body 12 when compound armature housing 30 is positioned for service therein. Stator 26 may further include a solenoid 90 electrically connected with a set of electrical terminals 67. When electrical current is applied to electrical terminals 67 to energize solenoid 90, solenoid 90 may generate a magnetic flux. Operating fuel injector 10 may thus further include channeling magnetic flux in actuator assembly 24 according to magnetic flux path P1. Flux path P1 may pass about solenoid 90, through stator 26, through flux carrying component 34, across sliding air gap 36, and into armature 28. From armature 28, the magnetic flux may be channeled across axial air gap 74 and back into stator 26. As will be understood by those skilled in the art, energizing solenoid 90 may cause armature 28 to move towards stator 26 across axial air gap 74. Movable member 29 may contact stop 31 to limit travel of armature 28 towards stator 26 and prevent contact therewith. When solenoid 90 is de-energized, armature 28 may move in a reverse direction away from stator 26, under the influence of a return spring 19 coupled with movable member 29.
Moving armature 28 by energizing solenoid 90 may further cause movable member 29 to move from a first pin position to a second pin position. This in turn may result in movement of valve member 86 from a first valve position to a second valve position by way of a fluid pressure of fuel supplied via fuel inlet 56. Moving valve member 86 may occur during moving movable member 29, and can result in relieving a closing hydraulic pressure on outlet check 88 to enable moving outlet check 88 from a closed position to an open position to initiate fuel injection. De-energizing solenoid 90 will tend to result in closing of outlet check 88.
Operating device 10 may further include channeling a clamping load between first body piece 14 and second body piece 18 through load carrying component 32 of compound armature housing 30. As discussed above, clamping mechanism 22 may include cooperating threads 68 and 70 which enable fuel injector cap 64 to be urged downward against first body piece 14, and thereby clamp compound armature housing 30 and spacer 48 between first clamping surface 16 and second clamping surface 20. In
Turning now to
In
The improved, faster response of a device according to the present disclosure is believed due at least in part to reduced eddy currents. Since the electrical conductivity of flux carrying component 34 is less than that of conventional flux ring materials the generation of eddy currents which produce problematic magnetic fields is reduced. As a result, when magnetic flux is generated by energizing solenoid 90, or when flux decays by de-energizing solenoid 90, armature 28 is less affected, if at all, by eddy current-generated magnetic fields or residual magnetism, in comparison with earlier designs having uniform, solid flux rings and even slotted flux rings. In the particular case of actuators used for certain applications such as valve control in a fuel injector, relatively more precise and predictable operation will be possible than in earlier systems.
The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims.
