Abstract:
A valve assembly includes a housing having a valve bore, a valve seat, and at least one port communicating with the bore. A moveable plunger resides in the valve bore and selectively seals against the valve seat. A bobbin integral with the housing has a solenoid bore adjacent to and coaxial with the valve bore. A moveable armature resides in the solenoid bore and has an operating rod connected to the plunger. A pole piece resides in the solenoid bore adjacent the armature. A solenoid coil is wound about the bobbin. A flux conductor partially surrounding the bobbin, pole piece, and armature. An assembly method includes flowing air through the port, inserting the plunger or another sealing element into the bore while monitoring the fluid flow; and stopping the plunger or sealing element when the flow is at a preselected condition.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to valves and more particularly to a solenoid operated poppet valve. 
     Fluid flow systems often utilize one or more valves to control the flow of fluid therethrough. One particular kind of valve is a “poppet” valve. A poppet refers to the mating of a seat feature and a seal feature. When the two features are forced against each other, the result is a blockage that prohibits the flow of a fluid through a pathway. When the features are separated, the pathway is opened, allowing the fluid to flow freely. 
     Poppet valves are often operated by a solenoid including a coil which creates a magnetic field when electrically charged. The magnetic field creates a force that causes components to move causing separation of the seal and the seat, thereby activating the valve. 
     While they are required elements in most fluid flow systems, valves are also the source of losses and excess energy consumption in these systems. For example, the fluid flow through the valve body and poppet experiences pressure losses as compared to a straight tube or pipe. 
     The solenoid may also be the cause of inefficiencies. If the solenoid coil induces more flux energy than the magnetic circuit can convert to mechanical force, saturation will occur and power going into the coil will be wasted. This condition will also generate excess heat. On the opposite extreme, if the coil is not large enough, the full potential of the magnetic circuit will not be achieved and the overall valve will have very limited capabilities. 
     Accordingly, there is a need for a solenoid valve which operates efficiently both electrically and fluidically. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, it is an object of the invention to provide a combination valve and solenoid. 
     It is another object of the invention to provide a solenoid valve have increased electrical operating efficiency. 
     It is another object of the invention to provide a solenoid valve having increased fluid efficiency. 
     It is yet another object of the invention to provide a method for assembling a valve which compensates for manufacturing tolerances of the various components. 
     These and other objects are met by the above-mentioned need is met by the present invention, which according to one embodiment provides valve assembly, including: an elongated valve body defining: an integral valve housing having a valve bore, a proximate valve seat, and at least one port disposed in fluid communication with the bore; a moveable plunger disposed in the valve bore and adapted to selectively seal against the valve seat; and a generally cylindrical bobbin defining a solenoid bore disposed adjacent to and coaxial with the valve bore. A moveable, magnetically permeable armature is disposed in the solenoid bore and has an operating rod which extends into the valve bore and is connected to the plunger. A magnetically permeable pole piece is disposed in the solenoid bore adjacent the armature. A solenoid coil is wound about an exterior of the bobbin; and a flux conductor partially surrounds the bobbin, the pole piece, and the armature. 
     According to another embodiment of the invention, valve bore is open-ended, and further includes an end cap received in the bore which defines a distal valve seat opposite the proximate valve seat. 
     According to another embodiment of the invention, the valve assembly further includes: first, second, and third ports in fluid communication with the valve bore, wherein the first and third ports, are disposed on opposite sides of the distal valve seat, and the second and third ports are disposed on opposite sides of the proximate valve seat. 
     According to another embodiment of the invention, the flux conductor includes: a longitudinal portion; a first end wall extending radially from the longitudinal portion and having a first cutout disposed between a first pair of radially-extending legs, the first cutout surrounding the pole piece. A second end wall extends radially from the longitudinal portion and has a second cutout disposed between a second pair of radially-extending legs. The second cutout surrounds the armature. 
     According to another embodiment of the invention, the valve assembly further includes a filler piece disposed in the second cutout, such that the second end wall effectively encircles the entire perimeter of the armature. 
     According to another embodiment of the invention, the filler piece is secured to the second end wall by crimping the second pair of legs around the filler piece. 
     According to another embodiment of the invention, a ratio of a longitudinal length of the coil to a cross-sectional area of the coil is 11:1 to about 15:1. 
     According to another embodiment of the invention, the ratio of the longitudinal length of the coil to the cross-sectional area of the coil is at least about 13:1. 
     According to another embodiment of the invention, a ratio a cross-sectional area of the coil a cross-sectional area of the armature is about 2:1 to about 3:1. 
     According to another embodiment of the invention, the ratio of the cross-sectional area of the coil to a cross-sectional area of the armature is at least about 2.4 to 1. 
     According to another embodiment of the invention, a solenoid includes: a generally cylindrical bobbin defining a solenoid bore; a moveable, magnetically permeable armature disposed in the solenoid bore and having an operating rod extending therefrom; a magnetically permeable pole piece disposed in the solenoid bore adjacent the armature; a solenoid coil wound about an exterior of the bobbin; and a flux conductor partially surrounding the bobbin, the pole piece, and the armature. 
     According to another embodiment of the invention, a method of assembling a valve includes: providing a valve housing having a bore therein, and at least one port in flow communication with the bore; providing at least one sealing element receivable in the bore, wherein the position of the element affects the flow through the port; flowing air through the port; inserting the sealing element into the bore while monitoring the fluid flow; and stopping the sealing element when the flow is at a preselected condition. 
     According to another embodiment of the invention, a method of assembling a valve includes: providing a valve housing having: an open-ended bore; first, second, and third ports disposed in flow communication with the bore; and first valve seat disposed between the second port and the third port. An end cap is provided which is adapted to be received in the bore and defining a second valve seat disposed between the first port and the third port; An operating rod is disposed in the bore and moveable between a first position adjacent the first valve seat, and a second position away from the first valve seat; a plunger is adapted to fit in the bore and be attached to the operating rod. The plunger has: a first seal adapted to engage the first valve seat; and a second seal adapted to engage the second valve seat. The operating rod is moved to the first position a first flow of fluid is created through the third port; The plunger is inserted into the bore and moved towards the first seat while monitoring a flow rate of the first flow. The plunger is stopped at a position where the first flow is terminated; and the plunger is secured to the operating rod. 
     According to another embodiment of the invention, the method further includes: after stopping the plunger at a position where the first flow is terminated, continuing to move the plunger towards the seat until the first seal is compressed to a selected degree. 
     According to another embodiment of the invention, the method further includes: creating a second flow of fluid through the first port; inserting the end cap into the bore and moving the end cap towards the first seat while monitoring a flow rate of the second flow; stopping the end cap at a position where the second flow equals a predetermined value; and securing the end cap to the valve housing. 
     According to another embodiment of the invention, the method further includes: moving the plunger against the second valve seat; creating a third flow of fluid through the second port; inserting the end cap into the bore and moving the end cap towards the first seat while monitoring a flow rate of the third flow; stopping the end cap at a position where the third flow equals a predetermined value; and securing the end cap to the valve housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter that is regarded as the invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
         FIG. 1  is a side cross-sectional view of a valve assembly constructed in accordance with the present invention; 
         FIG. 2  is a partial cross-sectional view of the valve shown in  FIG. 1 , in an activated position; 
         FIG. 3  is an exploded cross-sectional view of a portion of the valve assembly of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the valve assembly of  FIG. 3  in a partially assembled condition; 
         FIG. 5  is a cross-sectional view of the valve assembly of  FIG. 3  in an assembled condition; 
         FIG. 6  is a perspective view of a portion of the valve assembly of  FIG. 1 ; 
         FIG. 7  is an end view of the valve assembly shown in  FIG. 6 , shown a pre-assembly condition; 
         FIG. 8  is an end view of the valve assembly shown in  FIG. 6  after a crimping operation has been completed; 
         FIG. 9  is another perspective view of a portion of the valve assembly of  FIG. 1 ; 
         FIG. 10  is an end view of the valve assembly shown in  FIG. 9 , shown a pre-assembly condition; 
         FIG. 11  is an end view of the valve assembly shown in  FIG. 9  after a crimping operation has been completed; 
         FIG. 12  is an exploded cross-sectional view of a portion of the valve assembly of  FIG. 1  showing a first method of assembly; 
         FIG. 13  is another view of the valve assembly of  FIG. 12  showing an end cap partially installed therein; 
         FIG. 14  is another view of the valve assembly of  FIG. 12  showing an end cap locked into position therein; 
         FIG. 15  is an exploded cross-sectional view of a portion of the valve assembly of  FIG. 1  showing an alternate method of assembly; 
         FIG. 16  is another view of the valve assembly of  FIG. 15  showing an end cap partially installed therein; and 
         FIG. 17  is another view of the valve assembly of  FIG. 15  showing an end cap locked into position therein. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,  FIGS. 1-5  illustrate an exemplary valve assembly  10  constructed in accordance with the present invention. The basic components of the valve assembly are a valve body  12  defining a housing  14  and a bobbin  16 , an end cap  18 , a plunger  20 , a spring  54 , an armature  22 , a pole piece  24 , a coil  26 , and a flux conductor  28 . The internal components each slide or are pressed into the valve body  12 , as shown in  FIGS. 3 and 4 . The bobbin  16 , armature  22 , pole piece  24 , coil  26 , and flux conductor  28 , collectively form a solenoid  30 . 
     The housing  14  includes a valve bore  32  having a first end  34  and a second end  36  which receives the plunger  20 . A “normally closed” first or distal valve seat  38  is formed at the first end of the valve bore  32 , and a “normally open” second or proximate valve seat  40  is formed at the second end  36  of the valve bore  32 . The plunger  20  carries resilient first and second seals  42  and  44  on opposed faces thereof. In the illustrated example, the first and second seals  42  and  44  are through-molded to the plunger  20  as a single piece and are connected to each other by a neck  46  which extends through a central opening  48  in the plunger  20 . 
     The plunger  20  is slidably mounted in the valve bore  32  such that the first seal  42  contacts the first valve seat  38  when the plunger  20  is positioned at the first end  34  of the valve bore  32 , and the second seal  44  contacts the second valve seat  4 Q when the plunger  20  is positioned at the second end  36  of the valve bore  32 . A first port  50  is disposed in fluid communication with the first valve seat  38 , and a second port  52  is disposed in fluid communication with the second valve seat  40 . Biasing means such as spring  54  may be provided to urge the plunger  20  towards the first end  34 . Thus, when the valve is not activated, the first port  50  is “normally closed” and the second port  52  is “normally open”. A common port  56  is disposed such that it is in fluid communication with either the first port  50  or the second port  52  depending upon the position of the plunger  20 . In  FIG. 1 , the first port  50  is closed off and the common port  56  is in flow communication with the second port  52 , while in  FIG. 2  the second port  52  is closed off and the common port  56  is in flow communication with the first port  50 . 
     In the illustrated example, the end cap  18  forms part of the housing  14 . The end cap  18  is generally cylindrical and has features formed therein which define the first valve seat  38  and a portion of the first port  50 . The end cap  18  is slidably received in the first end  34  of the valve bore  32  and is appropriately sealed against leakage, for example by first and second O-rings  58  and  60 . 
     The valve assembly  10  includes several features to improve the flow efficiency therethrough. The fluidic performance capability of a valve is generally controlled by the area, or “orifice” of the smallest section of the flow path that the fluid travels through. This area is defined as the valve orifice or “measured” orifice. This limiting section could potentially be located anywhere within the flow path. 
     The valve assembly  10  is designed such that the measured orifice is substantially the same for the first, second, and common ports  50 ,  52 , and  56 , respectively, so as not to create disproportionate performance characteristics for the different pathways. 
     The valve assembly  10  is designed with the shortest internal flow paths possible. This is done by placing the first, second, and common ports  50 ,  52 , and  56  on the same end of the valve assembly  10  and by keeping the distance between the ports as small as possible. 
     The valve assembly  10  also incorporates the largest possible area in all fluid pathways. The valve assembly  10  has a preselected nominal measured orifice size, i.e. a design point diameter, which in this example is 1.9 mm (0.075 in.) The various fluid pathways have a flow area that matches the measured orifice size only where required by the design, i.e., at entrances of the first, second, and common ports  50 ,  52 , and  56 . At all other points, the pathways are greater in flow area than the measured orifice. For example, each of the first, second, and common ports has an added volume associated therewith formed in the housing  14 . These volumes are labeled  62 ,  64 , and  66 , respectively. These added volumes ensure that the “effective” orifice, which is affected by loss-causing features, is as close as possible to the measured orifice, for each flowpath. 
     The bobbin  16  is an elongated structure that is integrally formed with the housing  14 . The bobbin  16  defines a solenoid bore  67  and has a first end  68  disposed next to the second end  36  of the valve bore  32  which carries an outwardly-extending first flange  70 , and a spaced-apart second end  72  which carries an outwardly-extending second flange  74 . 
     The conductive armature  22 , made of a suitable magnetically permeable material such as steel, is disposed inside the solenoid bore  67 . The armature  22  is generally cylindrical and has a first end  76  which is flat-faced and a second end  78  which includes a tapered section  80  and an operating rod  82 . The operating rod  82  is connected to the plunger  20  such that motion of the armature  22  is transferred to the plunger  20 . In the illustrated example, the operating rod  82  is received in the central opening  48  of the plunger  20  and secured thereto by an interference fit, which may be facilitated by providing outwardly-extending barbs (not shown) disposed on the operating rod  82 . 
     The conductive pole piece  24 , also made of a suitable magnetically permeable material such as steel, is disposed inside the solenoid bore  67  near the second end  72  of the bobbin  16 . In the illustrated example, the pole piece  24  is generally cylindrical with flat-faced ends, and is secured to the bobbin  16  by a tapered annular ridge  84  formed thereon which engages a groove  86  in the solenoid bore  67 . 
     The coil  26  which comprises multiple turns of wire is wound about the exterior of the bobbin  16  between the first flange  70  and the second flange  74 . Suitable means of a known type (not shown) are provided for connecting the coil to a source of electrical power. A ratio of coil length to cross-sectional area in the range of about 11:1 to about 15:1, preferably at least 13:1, combined with a ratio of coil cross-sectional area to pole or armature cross-sectional area in the range of about 2:1 to about 3:1, and preferably at least 2.4:1, has been found to give an efficiently design which fits within the package width of a 10 mm nominal size valve assembly  10 . 
     When assembled, there is a radial gap “R” present between the outer surface of the armature  22  and the flux conductor  28 . The bobbin  16 , which has essentially the same magnetic permeability as air, fills this radial gap R. There is also a “stroke gap”, denoted “S”, between the ends of the armature  22  and the pole piece  24  when the coil  26  is not energized. 
     The flux conductor  28  partially surrounds the bobbin  16 , pole piece  24 , and armature  22 . The flux conductor  28  is preferably made from a material of high magnetic permeability. One suitable material is a high iron-based steel. It is preferred that the flux conductor  28  to have the least contribution to the overall magnetic system reluctance relative to the remainder of the components within the solenoid  30 . 
     The radial gap “R”, and therefore any magnetic flux losses therethrough, is minimized by providing the bobbin  16  with a very thin wall section located where the radial gap R is located. For example, the wall thickness may be about 0.33 mm (0.013 in.) To accomplish this, a material is used which meets the structural and thermal requirements for the valve assembly  10  and is also able to be molded to very thin wall thicknesses. A non-limiting example of a suitable material is a blend of PolyPhenylene Ether Co-polymer (PPE) and Polyamide (PA) plastic resin. 
     The area of the radial gap R that the flux conductor  28  covers is controlled by the thickness of the material used for the flux conductor  28  and the amount of the circumference that the flux conductor  28  extends over. For the illustrated valve assembly having a nominal 1.9 mm (0.075 in.) orifice diameter, the flux conductor  28  may be about 1.57 mm (0.062 in.) thick, thus covering that much of the longitudinal length “L” of the radial gap R. 
     The thickness of the flux conductor  28  drives how much area can be made available for the flux path both through the flux conductor  28  and at the radial gap R. The valve assembly  10  in the illustrated example has a ratio of the thickness of the flux conductor  28  relative to the area of the pole  24  and armature  22  of about 3.5 to 1, which is far greater than for prior art solenoids of this type. 
     To achieve full coverage of the perimeter of the radial gap R, the flux conductor  28  is fabricated in two sections that, when assembled, will cover the full 360° of the radial gap R. 
       FIG. 6  depicts the solenoid portion of the valve assembly  10  and illustrates how the flux conductor  28  is secured to the bobbin  16 . The flux conductor  28  has a longitudinal portion  88  and a first end wall  90  which extends downward from the longitudinal portion  88  in a radial direction. The first end wall  90  has a first cutout  92  formed between a first pair of legs  94 A and  94 B. The first end wall  90  is assembled to the pole piece  24  by placing the first cutout  92  down over the perimeter of the pole piece  24  as shown in  FIG. 7 . The legs  94 A and  94 B are then crimped inward to firmly clamp the pole piece  24 , as shown in  FIG. 8 . The crimping process is facilitated by a pair of notches  96 A and  96 B which are formed respectively in the legs  94 A and  94 B. 
       FIG. 9  depicts the opposite end of the solenoid portion of the valve assembly  10  and further illustrates how the flux conductor  28  is secured to the bobbin  16 . The flux conductor  28  has a second end wall  98  which extends downward from the longitudinal portion  88  in a radial direction. The second end wall  98  has a second cutout  100  formed between a second pair of legs  102 A and  102 B. The second end wall  98  is assembled to the first end  68  of the bobbin  16  by placing the second cutout  100  down over the perimeter of the first end  68  of the bobbin  16  as shown in  FIG. 10 . A filler piece  104  is placed underneath the bobbin  16  and between the second pair of legs  102 A,  102 B The legs  102 A and  102 B are then crimped inward to firmly clamp the filler piece  104  and the bobbin  16 , as shown in  FIG. 11 . The crimping process is facilitated by a pair of notches  106 A and  106 B which are formed respectively in the legs  102 A and  102 B. 
     When assembled as described above, the mean diameter of the radial gap R is about 4.2 mm (0.164 in.) This generates a flux path area of about 20.6 mm 2  (0.032 in. 2 ) which is almost twice as much as the area of the flux path found at the pole piece  24  and armature  22 . This gives a ratio of 1.8:1 of the flux path area of the radial gap R relative to the stroke gap S. The larger this ratio, the better the efficiency, and preferably this ratio is about 1.6:1 or greater. 
     Because solenoid valves are constructed of several components, the stack-up of tolerances of these components will have a distinct effect on the fluidic performance of the valve. This effect will be a considerable variance in the fluidic flow capacity of the valve. The quantity and construction of components used in the design of the valve will have a direct impact on the magnitude of this effect. The greater the number of components, the greater the stack-up of tolerances will be. Additionally, the less precise the method of fabrication, the greater the variances will be and the greater the effect on the fluidic flow. 
     Accordingly, the valve assembly  10  may be assembled by a method that removes virtually all effect of the tolerance stack-up of the components and of the inherent variances produced by the assorted fabrication methods. By applying a fluidic source to the valve and actively monitoring the fluidic flow during the assembly process, any performance characteristic associated with that level of assembly can be monitored and is used to confirm correct assembly position of the components being installed. This method allows a precise flow to be achieved limited in accuracy only by the gauging used to measure the flow. 
     The assembly method is illustrated in  FIGS. 12-14 . The plunger  20  with first and second seals  42  and  44  and spring  54  is installed directly to the operating rod  82  of the armature  22  that has already been assembled with the valve body  12 . When the plunger  20  is inserted into the valve bore  32 , the armature  22  is forced into the “activated” (i.e. coil energized) position. During the installation of the plunger  20 , a regulated air source (not shown) is connected to the second (i.e. normally open) port  52 . The plunger  20  with first and second seals  42  and  44  and spring  54  is then inserted in place to what will be the activated position and assembled to the point that the airflow through the second port  52  is completely stopped. At this point, the second seal  44  is pressed against the second valve seat  40  to a level that inhibits a set airflow. Depending on the planned valve configuration, the plunger  20  is inserted some amount further to force a certain percentage of compression against the second seal  44 . This allows for future compression set that may be seen in the resilient second seal  44 . 
     Next, the end cap  18 , which contains the first (normally closed) valve seat  38 , is inserted to a particular depth that is known to be less than its optimal position range, as shown in  FIG. 13 . A regulated air source (not shown) is connected to the first (normally closed) port  50  while a calibrated flow meter (also not shown) is connected to the common port  56 . The armature  22  is forced to its activated position so that the first port  50  is opened creating a clear flowpath to common port  56  thus allowing airflow through the valve assembly  10  that is measured by the flow meter. 
     The end cap  18  is then inserted further into position while the airflow is being monitored, as shown in  FIG. 14 . Once a target airflow for the desired configuration is achieved, the end cap  18  is permanently secured in place by a known method, for example by using fasteners, adhesives, staking, crimping, or the like. 
       FIGS. 15-17  illustrate an alternative assembly method, which differs from the method noted above in that the assembly is performed with the armature  22  in an un-activated state. The plunger  20  with first and second seals  42  and  44  and spring  54  is installed directly to the operating rod  82  of the armature  22  that has already been assembled with the valve body  12 . When the plunger  20  is inserted into the valve bore  32 , the armature  22  is forced into the “activated” (i.e. coil energized) position. During the installation of the plunger  20 , a regulated air source (not shown) is connected to the second (i.e. normally open) port  52 . The plunger  20  with first and second seals  42  and  44  and spring  54  is then inserted in place to what will be the activated position and assembled to the point that the airflow through the second port  52  is completely stopped. At this point, the second seal  44  is pressed against the second valve seat  40  to a level that inhibits a set airflow. Depending on the planned valve configuration, the plunger  20  is inserted some amount further to force a certain percentage of compression against the second seal  44 . This allows for future compression set that may be seen in the resilient second seal  44 . 
     Next, the end cap  18 , which contains the first (normally closed) valve seat  38 , is inserted to a particular depth that is known to be less than its optimal position range, as shown in  FIG. 16 . A regulated air source (not shown) is connected to the second (normally open) port  52  while a calibrated flow meter (also not shown) is connected to the common port  56 . The coil  26  is deactivated, allowing the spring  54  to force the armature  22  to its un-activated position. The second port  52  is opened creating a clear flowpath to common port  56  thus allowing airflow through the valve assembly  10  that is measured by the flow meter. 
     The end cap  18  is then inserted further into position while the airflow is being monitored, as shown in  FIG. 17 . Once a target airflow for the desired configuration is achieved, the end cap  18  is permanently secured in place by a known method, for example by using fasteners, adhesives, staking, crimping, or the like. 
     The ability to monitor the fluidic performance of the valve assembly  10  during the assembly process gives an additional capability to tune the valve assembly  10  to a specific performance point during the production assembly without having any components or operations added. This assembly procedure completely prevents the variance in the lengths of the valve body  12 , armature  22 , pole piece  24 , plunger  20  with seals  42  and  44 , and end cap  18  from affecting the fluidic performance of the final assembly. This method also overcomes the effects of wear on any tooling used to fabricate the various components such as injection molds or elastomer compression molds. Only the level of accuracy and repeatability of the equipment used to measure the fluidic parameters limit the repetitiveness of this method. 
     Utilizing the above-described features, it has been found that, at a given pressure point, the herein described valve assembly  10  allows about two times the fluidic flow, and requires only about half of the input power to actuate, than similar prior art valves. 
     A valve assembly including an integral solenoid has been disclosed. Various details of the invention may be changed without departing from its scope. Furthermore, the foregoing description of the preferred embodiments of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation.