Abstract:
An actuator includes a coil housing supporting an electric coil and a composite armature that is slidably disposed in the housing. The armature has a ferromagnetic core and an overmolded polymeric member that can define one or more of an alignment rib, a damping element, and a valve poppet.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to vehicle actuators.  
       BACKGROUND OF THE INVENTION  
       [0002]     Actuators such as current-controlled, electro-hydraulic valves are used in vehicles in anti-lock braking systems (ABS), traction control systems, stability control systems, automatic transmissions, and other systems. These valves typically use electrically-controlled sliding plungers to selectively permit or prevent fluid flow through the actuator under particular circumstances, as required for the application. The plunger must be ferromagnetic, so that as current is passed through a wire coil that surrounds the plunger, the resulting magnetic force can move the plunger. Because of this aspect of its functionality, the plunger is sometimes referred to as an “armature”. In typical configurations, a spring and/or fluid pressure biases the plunger to a “normal” position inside the actuator when the coil is not energized.  
         [0003]     A typical plunger defines a valve element on one end that mates with a primary valve seat which is formed in a valve body of the actuator. Additional valving structure, including plunger rods that extend through the primary valve seat to move a ball toward or away from a secondary valve seat, may be provided in the valve body and coupled in various ways to plunger movement as appropriate to establish two-way valves, three-way valves, and so on.  
         [0004]     The present invention, which finds application independent of the particular valving structure, recognizes that a solenoid valve plunger must not only act as an armature and as a valve seat closure element, but depending on the application may also require structure to facilitate guiding the plunger while sliding and cushioning the plunger at the ends of its travel. As further understood herein, some plunger functions demand one particular type of material while other functions might be optimally met using other types of plunger material.  
       SUMMARY OF THE INVENTION  
       [0005]     An actuator that can establish a release valve for a vehicle anti-lock brake system (ABS) includes a coil housing supporting an electric coil, and a composite armature slidably disposed in the housing. The composite armature includes a ferromagnetic core and an overmolded polymeric member defining an alignment element and/or a damping element and/or a valve poppet.  
         [0006]     Non-limiting alignment elements may include ribs that protrude longitudinally along a cylindrical surface of the armature. Non-limiting damping elements may include collars circumscribing a cylindrical surface of the armature. An end of the polymeric member may define a valve poppet that is configured for seating against a seat of a valve body.  
         [0007]     In another aspect, a vehicle anti-lock brake system (ABS) release valve includes a coil in a housing and a valve seat. A composite armature is actuatable by the coil to move away from or toward the valve seat. The armature includes a ferromagnetic core and at least one polymeric feature attached to the core. The armature moves to selectively establish a pressure relief path in the ABS.  
         [0008]     In yet another aspect, a hydraulic actuator has a coil housing and a wire coil disposed in the housing. A composite armature is reciprocatingly disposed within an annulus defined by the coil and is made of a metal core overmolded with a plastic material which defines an operationally useful feature.  
         [0009]     The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a partial cross-sectional view of an electro-hydraulic valve showing the present composite armature;  
         [0011]      FIG. 2  is a perspective view of a first embodiment of the present composite armature, with portions shown in phantom;  
         [0012]      FIG. 3  is a perspective view of a second embodiment of the present composite armature, with portions shown in phantom;  
         [0013]      FIG. 4  is a perspective view of a third embodiment of the present composite armature, with portions shown in phantom; and  
         [0014]      FIG. 5  is a perspective view of a fourth embodiment of the present composite armature, with portions shown in phantom. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]     Referring initially to  FIG. 1 , an actuator is shown, generally designated  10 , that can be part of the fluid communication path of a control system  12  of a vehicle  14 . The control system  12  may be any suitable control system requiring actuators such as but not limited to anti-lock braking systems (ABS), traction control systems, and stability control systems. The system  12  may include various sensors and a processor in accordance with principles known in the art, with the processor selectively energizing and deenergizing the below-described coil of the actuator  10  based on signals from the sensors as appropriate to control fluid flow through the system  12 . In one embodiment the system  12  is an ABS and the actuator  10  is a normally closed ABS release valve, although the principles set forth herein can apply to other types of valves, including normally open valves.  
         [0016]     As shown in  FIG. 1 , the actuator  10  includes a rigid, hollow, preferably ferrous metal coil can  16  in which a composite armature  18 , which may be referred to herein as a plunger, is reciprocatingly disposed within an annulus defined by the below-described coil for motion along the long axis of the armature  18 . Support structure such as bushings and/or a tube  19  may be provided in the coil can to radially support the below-described alignment features of the armature  18 . A lid  19   a  may be disposed between the tube  19  and coil can  16  as shown.  
         [0017]      FIG. 1  shows that the armature  18  may have a frusto-conical shaped valve element  20  or poppet portion formed on one end of the armature  18 , it being understood that the particular contour of the valve element  20  can take on other configurations. As can be appreciated in reference to  FIG. 1 , the valve element  20  can be moved against a complementarily-shaped valve seat  22  that is defined by a valve body  24  which is joined, in some implementations by the tube  19 , to the coil can  16 . The valve seat  22  defines a fluid passageway. When the armature  18  is in the closed configuration, i.e., against the valve seat  22 , fluid flow through the fluid passageway of the valve seat  22  is prevented. On the other hand, when the armature  18  is moved away from the valve seat  22  to an open configuration, fluid flow through the fluid passageway of the valve seat  22  is permitted.  
         [0018]     The armature  18  may be actuated by selectively energizing and deenergizing a coil  26  located in the coil can  16 . The coil  26  may be wound around a coil bay  27  in the can  16 . When the coil  26  is energized an electromagnetic coupling between the coil  26  and armature  18  moves the armature  18  in one direction, while deenergizing the coil  26  causes the armature to move back in the other direction under the influence of a spring  28  which is disposed between a stator (stop)  29  and armature  18 . In the embodiment shown the valve is normally closed in that the spring  28  biases the armature  18  against the valve seat  22  with the valve being opened upon energization of the coil, it being understood that other configurations may be provided wherein the valve might be normally open (e.g., because of the influence of fluid pressure against the valve element  20 , or by a spring located on the valve seat side) and may be closed upon energization of the coil  26 .  
         [0019]      FIG. 2  shows a more detailed view of the armature  18 , wherein a cylindrical, substantially solid core  30  of the armature  18  is made of ferrous metal. As shown, at one base of the ferrous metal cylinder  30  a hollow spring pocket  32  may be formed. The spring pocket  32  may be omitted altogether if desired or formed in the stator  29 . When formed in the armature  18 , the base of the spring pocket  32  is in the same plane as that of the ferrous metal cylinder  30 , such that a hollow space is formed in the core into which the spring  28  shown in  FIG. 1  can fit.  
         [0020]     At the opposite base of the ferrous metal core  30  is a valve element or poppet portion  34  made of polymeric material. This polymeric poppet preferably is overmolded onto an end of the core  30  into any desired shape. Less desirably, the polymeric poppet  34  may be made separately from the core  30  and then attached to the core by, e.g., adhesive bonding.  
         [0021]     In the exemplary non-limiting embodiment shown in  FIG. 2 , a portion  36  of the polymeric poppet  34  is cylindrical, with the contour of the poppet  34  rapidly decreasing in diameter to a narrow portion  38  wherein the diameter is constant. It is to be understood that the poppet  34  may take on other configurations as appropriate, such as the frusto-conical configuration shown in  FIG. 1 , to mate with complementarily-shaped valve seats.  
         [0022]      FIG. 3  displays an alternate embodiment of the armature  18  which in all essential respects is identical in configuration to the armature shown in  FIG. 2 , with the following exceptions. A ferrous core  40  is completely overmolded (except for the base with a spring pocket  41 ) with polymer material  42 . The overmold of polymer material  42  is characterized by both a poppet portion  44  and at least one raised alignment feature  46  on an otherwise cylindrical surface portion  48 . In the embodiment shown in  FIG. 3 , four alignment features  46  are shown, with each alignment feature  46  essentially being a longitudinally oriented rib that is raised from the cylindrical surface portion  48 . The ribs are radially spaced equally from each other by ninety degrees. The alignment features  46  thus extend parallel to a longitudinal axis defined by the ferrous metal core  40  to guide and radially support the armature  18  as it reciprocates within the actuator  10 .  
         [0023]      FIG. 4  displays yet another alternate concept of the armature  18  that has a ferrous metal core  50  formed with a hollow spring pocket  52  and that is overmolded with polymer material  54 . The polymer overmold defines at least one and in the embodiment shown in  FIG. 4  two damping features such as collars  56  near opposite bases of the ferrous metal core  50 . Each collar  56  protrudes radially from an otherwise cylindrical surface  58  of the overmolded polymer material, and each collar  56  circumscribes the surface  58 . The damping features may or may not impact other structure, but in any case restrict fluid flow around the armature to dampen armature acceleration.  
         [0024]      FIG. 5  displays an alternate concept of the armature  18  that in all essential respects is identical in configuration to those shown above, with the following exceptions. A metal core  60  with spring pocket  62  is overmolded with polymer material  64  that defines raised alignment features  66 , but that covers only a larger diameter portion  68  of the metal core  60 . The ferrous metal core  60  is similar in form to that described in previous figures except that the core  60  is tapered down to a poppet portion  70  which protrudes out of the polymer overmold. The ferrous metal core  60  thus is extended to form the poppet of the actuator  10 .  
         [0025]     While the particular COMPOSITE ARMATURE FOR VEHICLE ACTUATOR VALVE as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. It is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. &#39;112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited as a “step” instead of an “act”. Absent express definitions herein, claim terms are to be given all ordinary and accustomed meanings that are not irreconcilable with the present specification and file history.