Valves and valve actuation – Electrically actuated valve – Including solenoid
Reexamination Certificate
1999-10-14
2001-10-09
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Electrically actuated valve
Including solenoid
C251S077000
Reexamination Certificate
active
06299130
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to EGR valves for automotive engines. More particularly, it relates to apparatus and methods for supporting solenoid armatures for electronic EGR valves.
BACKGROUND OF THE INVENTION
Almost all modern automotive engines have an electronic exhaust gas recirculation valve (EEGR valve) to recycle a portion of the exhaust gases of the engine into the intake air stream of the engine. The exhaust gases, especially those from spark-ignition gasoline engines, include a substantial amount of incomplete combustion products, including unburned fuel, oxides of nitrogen and other compounds. These gases contribute substantially to air pollution. EGR valves, and the more recent EEGR valves were installed on automotive engines to reduce this exhaust gas pollution by recycling a portion of the exhaust gases back into the intake air stream, thereby recombusting the exhaust gases and reducing pollution.
The EGR valves are subjected to severe environmental conditions that cause premature failure and require premature replacement. EGR valves are located in the engine compartments of automobiles and are typically mounted directly on the engine. As a result, they are subjected to extremes in temperature due to thermal conduction and convection from the engine, and due to the extremely hot exhaust gas stream that they are designed to throttle. Engine compartment temperatures commonly vary from −20C to 160C. In addition to thermal stresses, EGRs are subject to extreme vibration as they are directly mounted to automobile engines that vibrate. Finally, since the underside of most automobiles are not enclosed, the engine compartment air is often filled with dirt, dust, oil, chemical vapours, moisture and road salt. All of these factors cause the premature failure of EGRs and necessitate their premature replacement.
Electronic EGR valves are particularly subject to premature failure due to their design. Modern EEGR valves are unlike earlier EGR valves in that they use an electrical actuator, typically a linear solenoid to open the valve itself instead of the older and more robust diaphragm arrangement of earlier EGRs. As a result EEGRs have more parts to fail, they require tighter tolerances to operate properly, and they have more sliding surfaces that can rapidly wear due to fouling by contaminants such as oil, dirt, dust and the like. In addition, the thermal extremes cause uneven expansion and contraction which can cause components to bind rather than slide with respect to each other. Linear solenoids are particularly subject to damage due to the relatively large diameter of the solenoid armatures (the moving part of the solenoid) and the relatively large excursion of the armature required to fully open the valve itself. As a result, they have large surface areas in sliding contact and correspondingly large bearings.
It is the purpose of this invention to provide a novel means of supporting the armature of an EEGR valve that reduces the premature EEGR wear and failure by reducing the amount of sliding contact between the armature and the stator.
SUMMARY OF THE PRESENT INVENTION
In accordance with the first embodiment of the invention an EEGR valve for an internal combustion is provided including a solenoid having a toroidal electrical coil, a cylindrical armature disposed inside the toroidal coil and two bearings coupled to the armature and to a substantially stationary portion of the solenoid, wherein the bearings each include a disk having a plurality of rings of slits, each of the rings being radially spaced apart, and a valve assembly including a valve pintle coaxial with the armature and disposed to abut and be moved by the solenoid, the pintle including a head with a conical sealing surface, and a circular valve seat surrounding the head and disposed for sealing engagement with the conical surface to throttle the flow of exhaust gas. Each of the plurality of rings of slits may be angularly offset with respect to each other about the longitudinal axis of the armature. The plurality of rings may include at least four rings of slits. The valve may also include a spring disposed to hold the bearings in a deflected position when the valve assembly is in a closed position. Each of the plurality of rings of slits may include at least four slits. Each of the four slits in each of the plurality of rings may have the same length as the others of the four slits in the same ring. The four slits in each of the plurality of rings may describe an arc that has a center point near the center of the disk. The center points of the arc defined by each of the four slits in each of the plurality of rings may be substantially the same.
In accordance with the second embodiment of the invention, a solenoid is provided including a toroidal electrical coil, a cylindrical armature disposed inside the toroidal coil, and a first planar bearing coupled to and supporting the armature and also coupled to a substantially stationary portion of the solenoid, wherein the bearing includes a disk having a plurality of rings of penetrations, each of the rings being radially spaced with respect to the other rings. A second planar bearing may be coupled to the armature to support it. This bearing may be coupled to a substantially stationary portion of the solenoid. It may have a plurality of rings of penetrations each being radially spaced with respect to the others. The first and second bearings may be circular and may be fixed to first and second stationary portions of the solenoid, respectively. The first stationary portion may be an upper stator and the second stationary portion may be a lower stator. The upper stator may include a first plurality of posts to which the first bearing is fixed. The lower stator may include a second plurality of posts to which the second bearing is fixed. The armature may include a metal shaft having an upper end and a lower end and further the upper end of the shaft may be fixed to the first bearing and the lower end of the shaft may be fixed to the second bearing. The first and second plurality of posts may be spaced substantially equiangularly about the longitudinal axis and may be spaced a substantially constant distance from the longitudinal axis.
In accordance with a third embodiment of the invention, a method of driving a solenoid having a toroidal coil, an armature disposed inside the toroidal coil and first and second planar bearings coupled to and supporting the armature within the toroidal coil, and first and second fixed bearing mounts, the method including the steps of coupling a first end of the armature to the first planar bearing, fixing the periphery of the first planar bearing to the first fixed bearing mounts, coupling a second end of the armature to the second planar bearings, fixing the periphery of the second planar bearing to the second fixed bearing mounts, moving the armature to a first preloaded position in which the first and second bearings are deflected from a rest position to a preloaded position and the first and second bearings are concave in a first direction, holding the armature in the first preloaded position with a spring, deflecting the armature and the first and second bearings to a second deflected position in which the first and second bearings are concave in a second direction that is opposite the first direction, by applying an electrical signal to the solenoid. The method may further include the step of forming a first and second plurality of slots in the first and second bearings by fine blanking the first and second bearings, respectively. The method may also include the step of providing a stress relief at each end of the first and second plurality of slots by fine blanking. The method may also include the step of disposing the first plurality of slots in a radially extending series of concentric circular rings about a center of the first bearing, and the step of disposing the second plurality of slots in a radially extending series of concentric circular rings about a center of the second bearing
Cook John Edward
Yew Kwang
Bastianelli John
Shaver Kevin
Siemens Canada Limited
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