Abstract:
An emission control valve ( 10 ) for controlling flow of gases with respect to combustion chamber space of an internal combustion engine. The valve has a housing ( 12 ) providing a flow path between an inlet port ( 14 ) for receiving gases and an outlet port ( 16 ) for delivering gases to the combustion chamber space. An armature ( 40 ) forms a valve element that selectively seats on and unseats from a seat ( 32 ) to selectively close and open the flow path. A permanent magnet source ( 40 ) magnetically biases the armature toward the seat. A solenoid ( 18 ) unseats the armature from the seat. A stop ( 64, 84, 104, 124 ) limits travel of the armature away from the seat. An energy absorbing structure ( 50, 70, 90, 110 ) mounted on the armature is arranged to strike the stop and absorb kinetic energy from the armature as the armature approaches the stop.

Description:
REFERENCE TO A RELATED APPLICATION AND PRIORITY CLAIM  
       [0001]     This application claims the benefit of U.S.  
         [0002]     Provisional Application No. 60/497,718, filed 20 Aug. 2003. 
     
    
     FIELD OF THE INVENTION  
       [0003]     This invention relates to solenoid-operated control valves, especially emission control valves, such as purge valves, for automotive vehicles.  
       BACKGROUND OF THE INVENTION  
       [0004]     A known on-board evaporative emission control system in an automotive vehicle powered by a gasoline engine includes a fuel vapor collection canister that collects volatile fuel vapors from the headspace of the fuel tank and a canister purge solenoid (CPS) valve that is opened at appropriate times to purge fuel vapors collected in the canister to the engine intake system where they entrain with the fuel-air charge entering the engine for combustion. A known CPS valve comprises a solenoid actuator that is under the control of a microprocessor-based engine management system to control the opening and closing of the valve.  
         [0005]     Certain such CPS valves comprise a movable valve element that is resiliently biased against a valve seat by a mechanical spring to close flow through the valve. When electric current flows through the solenoid actuator, a resulting electromagnetic field applies force to the solenoid armature in opposition to the spring bias force to unseat the valve element and allow flow through the valve. When the electric current ceases, the electromagnetic field collapses so that its force is no longer applied to the armature, allowing the spring bias force to re-seat the valve element closed and hence disallow flow through the valve.  
         [0006]     A novel CPS valve is disclosed in commonly owned U.S. patent application Ser. No. ______ filed ______. Instead of having a spring that imparts resilient bias to the movable valve element, the armature is permanently magnetized and arranged so as to be magnetically attracted to a stop that comprises magnetically permeable material and that defines one limit of travel for the movable valve element. When the current flows through the solenoid actuator, electromagnetic force acts with sufficient intensity on the permanently magnetized armature to oppose the magnetic attraction of the armature to the stop and move the armature away from the stop. The armature motion unseats the valve element, allowing flow through the valve.  
         [0007]     Movement of the armature away from the stop is limited by abutment of the armature with an opposite stop. When electric current flow through the solenoid actuator is discontinued, the electromagnetic field collapses, allowing the magnetic force of attraction of the armature to the first stop to move the armature back against that stop, thereby re-seating the valve element closed so as to disallow flow through the valve.  
         [0008]     The armature itself may or may not form the movable valve element. When the armature forms the movable valve element, the stop toward which it is magnetically attracted forms the valve seat. An example of such an armature is a cylindrical disc that moves within a suitable guide between the opposed stops.  
         [0009]     One advantage of this novel CPS valve is that it does not require a mechanical spring to bias the valve element closed. Consequently when the armature is unseated to open the valve, the armature motion is not resisted by a bias spring. And because the electromagnetic force must be large enough to overcome not only the permanent magnet bias but also any stiction between the armature and seat, the armature is apt to strike the stop that limits its travel away from the seat while containing a significant amount of kinetic energy.  
         [0010]     Certain patents disclose various forms of impact absorbing structures in solenoid-actuated valves, such as CPS valves. Examples appear in U.S. Pat. Nos. 4,901,974; 5,538,219; 5,775,670; 5,967,487; and 6,595,485. All of those examples utilize a bias spring that biases the valve element closed, and so some of the kinetic energy of the moving armature and opening valve element will be absorbed by compression of the bias spring rather than by an energy absorbing structure on the armature.  
       SUMMARY OF THE INVENTION  
       [0011]     Accordingly, a general aspect of the invention relates to an emission control valve for controlling flow of gases with respect to combustion chamber space of an internal combustion engine. The valve has a housing providing a flow path between an inlet port for receiving gases and an outlet port for delivering gases to the combustion chamber space. An armature forms a valve element that selectively seats on and unseats from a seat to selectively close and open the flow path. A permanent magnet source magnetically biases the armature toward the seat. A solenoid unseats the armature from the seat. A stop limits travel of the armature away from the seat. An energy absorbing structure mounted on the armature is arranged to strike the stop and absorb kinetic energy from the armature as the armature approaches the stop.  
         [0012]     Another general aspect relates to a fluid valve comprising a housing having an inlet port for receiving fluid and an outlet port for delivering fluid. A solenoid is disposed within the housing. A flow path extends within the housing between the inlet port and the outlet port and passes through the solenoid. An armature is controlled by the solenoid for operation between a position seated on the solenoid to close the flow path to fluid flow and a position unseated from the solenoid to open the flow path for fluid flow. A stop is disposed to stop the armature as the armature operates toward the unseated position. An elastomeric element is disposed on the armature and comprises both an energy absorbing formation for impact with the stop to dissipate kinetic energy of the armature as the armature approaches the stop and a seal for sealing the armature to the solenoid when the armature is in the seated position.  
         [0013]     A more specific aspect is that the permanent magnet source is in the armature.  
         [0014]     Another more specific aspect is that the permanent magnet source is the sole bias source acting on the armature.  
         [0015]     Another more specific aspect is that an end of a stator of the solenoid forms the seat.  
         [0016]     More specific aspects relate to details of various embodiments of energy absorbing structures.  
         [0017]     Still more aspects will be seen in the accompanying drawings and described in the detailed description given herein. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention according to the best mode contemplated at this time, and, together with the detailed description given here, serve to disclose the various aspects and features of the invention.  
         [0019]      FIG. 1  is a longitudinal cross-section view of an exemplary CPS valve incorporating principles of the invention in a first embodiment.  
         [0020]      FIG. 2  is an enlarged fragmentary view of a portion of  FIG. 1 .  
         [0021]      FIG. 3  is an enlarged fragmentary view of a portion of  FIG. 2 .  
         [0022]      FIG. 4  is a view similar to  FIG. 3  showing a second embodiment.  
         [0023]      FIG. 5  is a view similar to  FIG. 3  showing a third embodiment.  
         [0024]      FIG. 6  is a view similar to  FIG. 3  showing a fourth embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0025]      FIGS. 1-3  show a CPS valve  10  that comprises a housing  12  having an inlet port  14  adapted to be communicated to a vapor collection canister in an automotive evaporative emission control system and an outlet port  16  adapted to be communicated to the intake system of a gasoline engine that powers the automotive vehicle.  
         [0026]     Housing  12  comprises housing parts fastened together by screws  17  with an intervening gasket  15  to enclose a solenoid  18  whose electric terminals  20  protrude through housing  12  to provide for a bobbin-mounted coil  22  of the solenoid to be electrically connected to the vehicle electrical system so as to place valve  10  under the control of an engine management system.  
         [0027]     The bobbin, designated by the reference numeral  24 , comprises a cylindrical tubular core  26  coaxial with an imaginary longitudinal axis  28  of the valve. Core  26  fits coaxially to a cylindrical tubular body  30  of a ferromagnetic stator  32  that comprises a circular flange, or lip,  34  at one end. At the same end, bobbin  24  has a shallow circular recess  36  in which flange  34  sits. The depth of recess  36  is less than the flange thickness so that the end surface of the flange is slightly beyond the end face of the bobbin.  
         [0028]     The end of stator  32  opposite flange  34  protrudes from the opposite end of bobbin core  26  to fit into the tubular wall of port  14 , with an O-ring  38  sealing between the outer perimeter of the core and the inner perimeter of the port wall. Vapor that enters port  14  is thereby constrained to pass through body  30  of stator  32  as it flows through the valve toward outlet port  16 .  
         [0029]     A circular disc armature  40  is disposed within housing  12  coaxial with axis  28  for cooperation with the end of stator  32  containing flange  34 .  FIG. 1  shows armature  40  seated on that end of the stator.  
         [0030]     When so seated, armature  40  closes the flow path through the valve to disallow flow between ports  14  and  16 .  FIG. 2  shows armature  40  unseated from the end of the stator containing flange  34 , a condition that opens the flow path through the valve to allow flow between ports  14  and  16 .  
         [0031]     Armature  40  comprises permanently magnetized material, an example of which is Neodymium (NdFeB). Because stator  32  comprises ferromagnetic material such as low carbon steel (UNS  1008 ), armature  40  is attracted toward the end containing flange  34 . The magnetic force of attraction is sufficiently large to seat armature  40  as shown in  FIG. 1 .  
         [0032]     Travel of armature  40  between closed and open positions depicted respectively by  FIGS. 1 and 2  is guided by a suitable guide within housing  12  that functions to maintain armature  40  substantially coaxial with axis  28  without hindering vapor flow while the armature is unseated.  
         [0033]     Unseating of armature  40  occurs when coil  22  is electrically energized. Coil  22  is designed to impart to armature  40  an electromagnetic force that is opposite to the force of magnetic attraction of armature  40  toward stator  32  and that is large enough to assure that the armature will unseat when coil  22  is energized. Because the magnitude of that electromagnetic force must not only accelerate the armature from zero velocity, but also break the seal (hereinafter explained) of the armature to the seat, the armature, once unseated, will have a certain inertia that must be dissipated upon stopping. If the armature is allowed to directly impact a solid stop, such as a wall of housing  12  or an adjustable stop member  64 , that is adjustable axially on the housing wall, objectionable noise may be generated upon such impact. Moreover, repeated impacting may create wear on the impacting parts due to the magnitude of impact force.  
         [0034]     In accordance with principles of the invention, energy absorbing structure is associated with armature  40  to attenuate impact force and noise that accompanies such impact. That structure can include a seal for vapor-tight sealing of the armature to the stator when the armature is seated closed on the stator.  
         [0035]     The embodiment of  FIGS. 1-3 , shows an energy absorbing element  50  associated with armature  40 . Element  50  comprises a body  52  of elastomeric material that mounts in a central through-hole  54  of complementary shape in armature  40 . Both body  52  and through-hole  54  comprise complementary shoulders  56 ,  58 . At each end, element  50  comprises a respective circular formation  60 ,  62  of uniform thickness that joins with body  52  and radially overlaps the respective armature end face around through-hole  54 .  
         [0036]     Formation  62  serves to seal armature  40  vapor-tight to the end of the solenoid when the armature is seated to disallow flow. It can also absorb impact as the armature re-seats after having been operated to open position. Formation  60  serves to absorb impact of armature  40  with stop member  64  when the armature is unseated. Stop  64  can be made adjustable along the direction of axis  28  to set the amount of armature travel.  
         [0037]      FIGS. 4, 5 , and  6  shows additional embodiments that may offer even better impact absorption because of their particular shapes.  
         [0038]      FIG. 4  shows an energy absorbing element  70  associated with armature  40 . Like element  50 , element  70  comprises a body  72  of elastomeric material that mounts in a central through-hole  74  of complementary shape in armature  40 . Both body  72  and through-hole  74  also comprise complementary shoulders  76 ,  78 , and at the end confronting the solenoid, element  70  comprises a circular formation  80  of uniform thickness that joins with body  72  to radially overlap the armature end face around through-hole  74  for sealing armature  40  vapor-tight to the end of the solenoid when the armature is seated to disallow flow. Like formation  60 , formation  80  can also absorb impact as the armature re-seats.  
         [0039]     At its opposite end, element  70  comprises a circular cylindrical post  82  projecting from body  72  substantially coaxial with axis  28 . A stop  84  is arranged for cooperation with that end of element  70  to limit armature travel away from the seat. Stop  84  differs from stop  64  in that the former comprises an annular boss  86  surrounding a blind circular hole  88 . Boss  86  and hole  88  are substantially concentric with axis  28 , with boss  86  confronting the annular portion of body  72  surrounding post  82  and with hole  88  being open toward the post.  
         [0040]     Upon armature  40  unseating to allow flow through the valve, post  82  travels ever deeper into hole  88 . This may serve to impart some pneumatic damping to the armature motion. If the post  82  is sufficiently long to strike the bottom of hole  88  before body  72  strikes boss  86 , the post will absorb some of the energy of impact. If not, energy will be absorbed by the impact of body  72  with boss  86 , and if the armature has not been fully decelerated before post  82  strikes the bottom of hole  88 , then the post may begin to share in absorbing energy to bring the armature to a complete stop. The distal end of post  82  may have a parabolic or cup-like shape for achieving a desired energy absorption rate.  
         [0041]      FIG. 5  shows an energy absorbing element  90  associated with armature  40 . Like elements  50  and  70 , element  90  comprises a body  92  of elastomeric material that mounts in a central through-hole  94  of complementary shape in armature  40 . Both body  92  and through-hole  94  also comprise complementary shoulders  96 ,  98 , and at the end confronting the solenoid, element  90  comprises a circular formation  100  of uniform thickness that joins with body  92  to radially overlap the armature end face around through-hole  94  for sealing armature  40  vapor-tight to the end of the solenoid when the armature is seated to disallow flow.  
         [0042]     At its opposite end, element  90  comprises a saucer-shaped formation  102  supported on body  92 , substantially coaxial with axis  28 . A stop  104  is arranged for cooperation with formation  102  for stopping armature travel away from the stator. Stop  104  has a flat face confronting the concave face of formation  102 .  
         [0043]     Upon armature  40  unseating to allow flow through the valve, the rim of formation  102  will strike the confronting flat face of stop  104 . Continued motion of the armature will flex formation  102 , with the flexing absorbing the impact and eventually stopping the armature. Although formation  102  may appear to have a shape like a suction cup, its rim is relieved so that it will not be forced to stick to stop  104 .  
         [0044]      FIG. 6  shows an elastomeric energy absorbing element  110  associated with armature  40 . Element  110  comprises a body  112  that mounts in a central through-hole  114  of complementary shape in armature  40 . Unlike prior embodiments however, body  112  is hollow rather than solid. The particular shape of body  112  is shown as tubular. Both body  112  and through-hole  114  also comprise complementary shoulders  116 ,  118 , making the wall of tubular body  112  thicker along a portion of its length that is toward the stator. At its end confronting the stator, element  110  comprises a circular annular formation  120  of uniform thickness that joins with the thicker-walled portion of body  112  to radially overlap the armature end face around through-hole  114  for sealing armature  40  vapor-tight to the end of the stator when the armature is seated closed to disallow flow.  
         [0045]     At its opposite end, element  110  comprises a dome-shaped formation  122  projecting from body  112 , substantially coaxial with axis  28 . The interior of formation  122  is hollow. At its base that joins with the thinner-walled portion of body  112 , formation  122  has an annular outer flange  123  that is disposed against the margin of the armature through-hole. A stop  124  is arranged for cooperation with formation  122  for stopping armature travel away from the seat. Stop  124  has a flat face confronting formation  122 .  
         [0046]     Upon armature  40  unseating to allow flow through the valve, the rounded peak of formation  122  will strike the confronting flat face of stop  124 . Continued motion of the armature will begin to flatten the peak, reducing the height of the dome-shaped formation, and as the peak flattens, the formation absorbs the impact and eventually stops the armature. The shape and thickness of the dome may be designed to achieve a desired energy absorption rate.  
         [0047]     When the solenoid of any of the CPS valves that have been described is energized, the valve will open due to the overpowering electromagnetic force that acts on the armature to unseat the armature from the seat that is provided by the end of the stator. The respective element  50 ,  70 ,  90 ,  110  will strike the respective stop  64 ,  84 ,  104 ,  124  to arrest the armature motion during the impact, attenuating the impact force and resulting noise in the process. As long as the coil remains energized by electric current, the valve stays open. When the electric current stops, the electromagnetic force applied by the solenoid actuator to the armature essentially ceases, allowing the permanent magnetism of the armature to pull the armature back to re-seat it on the end of the stator thereby closing the flow path through the valve.  
         [0048]     While the foregoing has described a preferred embodiment of the present invention, it is to be appreciated that the inventive principles may be practiced in any form that falls within the scope of the following claims.