Patent Publication Number: US-9852834-B2

Title: Adjustable center pole

Description:
This application claims the benefit of U.S. Provisional Application No. 61/922,157 filed Dec. 31, 2013, which is hereby incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     The present invention relates generally to solenoid actuators, and more particularly to solenoid actuators having an adjustable pole for precisely adjusting a working air gap. 
     BACKGROUND 
     A conventional method of setting the air gap between a pole of a solenoid actuator and the plunger is to use a mechanical spacer to control the air gap. The center pole is permanently pushed into position until the mechanical stop is reached. To tune the solenoid to the system the technician must adjust the spring pressure, the amount of current, or the pulse-width modulation (PWM) signal percentage going into the solenoid. 
     SUMMARY OF INVENTION 
     Therefore, presented is a solenoid assembly with an adjustable threaded pole having an interference fit section to be used with a complementary threaded receiving (e.g., the bore of the top plate) component with a complimentary interference fit section. The adjustable threaded sections are used to pull or push the interference fit sections together and allow for precise locating of the interference fit sections and adjustment of the working air gap, thereby controlling solenoid operation without having to adjust spring pressure or coil current. Using a fast switching hydraulic pilot valve as a non-exhaustive example, the threaded pole is used to set and maintain a precision working air gap between the pole piece and the plunger of the electromagnetic solenoid assembly. The interference fit holds the pole piece into location while still allowing the solenoid to be adjustable without a loss in flux density. 
     According to one aspect of the invention, an adjustable solenoid assembly includes a solenoid body; a coil for producing a magnetic field in an area of the assembly in response to electrical energization of the coil; a plunger mounted for longitudinal movement in said area of the assembly, the plunger bounded by an outer surface extending generally adjacent the inner wall of said coil, said plunger longitudinally movable in said assembly responsive to the magnetic field produced by the coil; a receiver including a threaded portion and an interference portion; an adjustable pole receivable in the bore and including a threaded portion and an interference portion, wherein the threaded portion of the adjustable pole is complementary to and threadably engageable with the threaded portion of the receiver, and the interference portion of the adjustable pole is complementary to and interferingly engageable with the interference portion of the receiver. 
     Optionally, the adjustable solenoid assembly includes an interference relief area. 
     Optionally, the interference relief area is arranged longitudinally between the threaded portions and the interference portions. 
     According to another aspect of the invention, a method of adjusting an adjustable solenoid assembly having a coil and an adjustable pole, comprising the steps of: electrically energizing the coil; monitoring an output of the solenoid assembly while the coil is energized; and adjusting the adjustable pole while monitoring the output. 
     Optionally, the solenoid assembly includes a coil for producing a magnetic field in an area of the assembly in response to electrical energization of the coil; a plunger mounted for longitudinal movement in said area of the assembly, the plunger bounded by an outer surface extending generally adjacent the inner wall of said coil, said plunger comprised of magnetic material and longitudinally movable in said assembly responsive to the magnetic field produced by the coil; a receiver including a threaded portion and an interference portion; an adjustable pole receivable in the receiver and including a threaded portion and an interference portion, wherein the threaded portion of the adjustable pole is complementary to and threadably engageable with the threaded portion of the receiver, and the interference portion of the adjustable pole is complementary to and interferingly engageable with the interference portion of the receiver. 
     Optionally, the adjustable solenoid assembly includes an interference relief area. 
     Optionally, the interference relief area is arranged longitudinally between the threaded portions and the interference portions. 
     Optionally, the monitoring of the output further includes monitoring the output pressure of a fast switching hydraulic pilot valve. 
     The foregoing and other features of the invention are hereinafter described in greater detail with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a partial cross-sectional view of an exemplary adjustable solenoid assembly having an adjustable pole with an interference fit section; and 
         FIG. 2  shows a method of adjusting an adjustable pole in exemplary solenoid assemblies. 
     
    
    
     DETAILED DESCRIPTION 
     Electromechanical solenoid actuators include an electromagnetically inductive coil, wound around a movable armature or plunger. The coil is shaped such that the plunger can be moved in and out of the center, altering the coil&#39;s inductance and thereby becoming an electromagnet. The actuator may be used to provide a mechanical force to some mechanism such as controlling a hydraulic valve. Solenoid actuators may be controlled directly by a controller circuit, and typically have quick reaction times. 
     Generically, for a solenoid to operate two air gaps are required: one between the center pole and the plunger, and one between the solenoid body and plunger. These air gaps allow for the plunger to move based on the amount of magnetic force generated by the coil. Any additional air gaps reduce the flux density of the solenoid assembly, decreasing the efficiency of the design. The exemplary adjustable solenoid pole discussed herein does not introduce a third air gap into the system as in conventional adjustable solenoids. Exemplary embodiments utilize a press fit between the solenoid top plate (e.g., part of the solenoid body) and the pole. Threads are used to bring the press fit into position and allow for adjustment once the solenoid is assembled. The threads can move the pole in or out of the coil, increasing or decreasing the air gap between the pole and the plunger. This resulting force, or movement of the plunger, can be monitored to tune the solenoid to the desired value. In the case of a fast switching hydraulic pilot valve the output pressure can be monitored while the pole is being adjusted to achieve the desired output pressure. 
     An exemplary actuator  10  is shown in  FIG. 1  and includes a precisely adjustable pole  21  for controlling the working air gap  23  between the plunger  20  and the pole  21 . The solenoid actuator  10  includes a solenoid body  12  housing the plunger  20  which is moveable within the body via energization of a coil  34 . 
     The actuator  10  includes a cap  26  which may include a port for electrical connection of the actuator to a power source and/or controller (not shown). The cap  26  may generally seal the interior components away from the operating environment by sealingly connecting to the body  12 , thereby preventing contamination and corrosion of interior components. The coil  34  is supported in the body  12  and is connected to the power source via coil wire leads  36  passing through the cap  26 . The coil  34  may be bounded inwardly by a sleeve member (not shown). 
     The armature or plunger  20  is positioned in the body  12  and may be, for example, generally circular in cross section, although other cross-sectional shapes are possible. The plunger has an outer surface spaced from the body  12  and defining therewith a non-working air gap  13  between the plunger and the body. The plunger  20  is longitudinally moveable inside the body  12 , and the lower end of plunger  20  (not shown) may be in abutting or other contact with the element to be actuated. The plunger  20  may be permanently or temporarily secured, directly or indirectly, with the element to be actuated as is known in the art. 
     A solenoid top plate  14  may be provided as a portion of the body  12  or as a separate component (for example, for ease of coil assembly). A receiver (e.g., bore)  15  through the top plate accepts an adjustable pole  21 . In particular, pole  21  may be threadably received in the bore  15  by a threaded section  16  of the top plate, and may be press fit into the bore in a press fit or interference section  17  of the bore. 
     In operation of the actuator, electric current is supplied through the coil  34  to create an electromagnetic field. The magnetic force causes plunger  20  to move from a first position spaced apart from the pole  21  to a second position towards the pole  21  in proportion to the force of the field. The force of the plunger overcomes the opposing force of the spring  22  and thereby moves the element to be actuated. Reducing the current through coil  34  reduces the magnetic force on plunger  20  and enables spring  22  to move the plunger toward the first position. 
     In exemplary embodiments, the solenoid may be used to control the flow of a hydraulic fluid through a valve. Of course in other embodiments of the invention, the flow of other types of fluid (e.g., refrigerant material) may be controlled or other types of control elements may be used other than valve elements. Exemplary embodiments are suited for use with proportional valves and two position valves, as well as valves that are normally open or normally closed. 
     The adjustable threaded pole  21  is also provided with an interference section  19  to engage the complementary interference section  17  of a threaded receiving (e.g., the bore  15  of the top plate  26 ) component. 
     Likewise, the adjustable threaded pole  21  is provided with a threaded section  18  to engage the complementary threaded section  16  of the threaded receiving component (e.g., bore  15  of the top plate  26 ). The adjustable threaded sections are used to pull or push the interference fit sections together and allow for precise locating of the interference sections and adjustment. Using a fast switching hydraulic pilot valve as an example, the threaded pole is used to set and maintain a precision working air gap between the pole piece and the plunger of the electromagnetic solenoid assembly. The interference fit holds the pole piece into location while still allowing the solenoid to be adjustable without a loss in flux density. 
     By threaded sections  16  and  18 , it is meant that these sections each include a screw thread that, when intermeshed or engaged are used to convert rotational movement/force on the pole relative to the rest of the assembly into linear longitudinal movement/force on the pole relative to the rest of the assembly. 
     The lead of the screw threads may be chosen so that friction is sufficient to prevent the screw from slipping when linear force is applied in the absence of rotational force. Further, because fine adjustment is preferred in exemplary embodiments, the lead may be chosen to be a particularly fine lead to provide adjustment fidelity to approximately one ten-thousandths of an inch. In particular, the bore  15 , the threaded sections  16  and  18 , the pole  21  and the body  12  are configured to provide such fidelity and to allow for a final working air gap of about 9-10 thousandths of an inch. 
     By interference sections  17  and  19 , it is meant that the interference section  17  includes a diameter corresponding to the diameter of a corresponding interference section  19  of the adjustable pole  21  for providing an interference fit therebetween. The interference sections, therefore, at least partially overlap in a longitudinal direction (i.e., along the stroke direction of the plunger). The interference fit may be a press fit in which the outer diameter of the pole is larger than the inner diameter of the bore. 
     The pole  21  may include an exterior end face  40  including a tool engagement portion  41  for allowing a tool to be used to rotate the pole  21  with respect to the rest of the solenoid assembly  10  and thereby longitudinally adjust the pole  21 . The tool engagement portion  41  may be any appropriate form such as a hexagonal bolt end for interfacing with a socket, a socket for engaging with a hex-key tool, or a slot or cross for engaging with a screw driver. Alternatively, a proprietary or specialized form may be used to prevent unauthorized tampering. 
     Optionally, a relief section  24  of the bore  15  may be included in which the inner diameter is greater than the outer diameter of a corresponding relief section  25  of the pole  15 . These relief sections at least partially overlap in the longitudinal direction and allow for control of the size of the overlapped portion of the longitudinally overlapping interference sections. 
     In an embodiment, the interference sections  17  and  19  are longitudinally spaced from the end of the adjustable pole  21  proximate the plunger  20 . In an embodiment, the interference sections  17  and  19  are longitudinally spaced from the end of the adjustable pole  21  distal the plunger  20 . In an embodiment, the interference sections  17  and  19  are longitudinally proximal to but not overlapping the coil  34 . 
     In an embodiment, the threaded sections  16  and  18  are longitudinally spaced from the interference sections  17  and  19 . In an embodiment, the threaded sections  16  and  18  are adjacent the end of the adjustable pole distal the plunger  20 . 
     In an embodiment, the relief sections  24  and  25  may be longitudinally intermediate between the interference sections  17  and  19  and the threaded sections  16  and  18 . 
     Lubricating coatings can also be applied to the adjustable pole  21  or the solenoid top plate  14  to ease in the assembly of the interference fit. Coatings such as oil, grease, or wax can reduce the torque required to turn the center pole  21  into position and prevent galling. 
     A difference between exemplary embodiments and conventional solenoids is the ability of exemplary embodiments to precisely set and/or adjust the air gap, or magnetic force, for a constant input current. This provides the device the ability to be tuned to a specified air gap, or magnetic force, for a specific current input. This has the benefit of being able to consistently produce a set threshold or maximum output for the solenoid device. By being able to accurately tune the solenoid, replacement parts could be introduced into the system with little or no control system adjustment. Adjustments could also be made in the field to further tune the solenoid without requiring special tools or test equipment. The field technician could adjust the coil center pole, increasing or decreasing the air gap, or magnetic force, until the desired setting is reached. Using the fast switching hydraulic pilot valve as an example, the technician could monitor the pressure controlled by the valve solenoid and increase it or decrease it as required in the system. 
     Exemplary embodiments also have the benefit of allowing adjustment with a minimal amount (or no) axial force being applied to the solenoid assembly. This is advantageous because it prevents adjustments of the air gap that are made in the field from resulting in valve misalignment when the solenoid assembly is being used to actuate a valve. 
     Exemplary embodiments also have the added benefit of being adjustable while not introducing a third air gap for the adjustment. This prevents a loss in flux density resulting in a stronger magnetic force for the amount of current supplied to the solenoid. 
     Turning to  FIG. 2 , shown is a method  100  for adjusting an air gap between an adjustable pole and a plunger of an adjustable solenoid controlling a valve. Although it is understood that this method may be applied to other situations, the example given herein of controlling a valve is used for clarity and expediency. 
     At block  110 , the solenoid coil is activated, for example, by applying a current to the coil. This current may be supplied by a controller integrated into the system of which the solenoid is a part, or may be a stand-alone power supply. Use of an integrated power supply (e.g., using the system controller) that is part of the system the solenoid is a part of may more accurately predict actual system performance. The current supplied may be any appropriate current for the solenoid, for example 200 mA. 
     At block  120 , the plunger of the solenoid moves in response to the activated coil. 
     At block  130 , a measurement of the output of the system controlled by the solenoid is obtained. Direct measurement of the displacement of the solenoid plunger may be measured. Alternatively, measurement of the mechanism moved by the plunger may be measured to better reflect actual system performance. Alternatively, measurement of another variable that provides the critical output of the device or system the solenoid is being used on may provide the most accurate reflection of future system performance. For example, at block  130 , measurement of pressure at a control port of a valve may be obtained. 
     At block  140 , adjustment of the adjustable pole is performed. In particular, the adjustable pole is rotated in the appropriate direction to move the pole in the longitudinal direction and thereby increase or decrease the working air gap between the pole and the plunger. 
     Blocks  130  and  140  may be continuously and/or iteratively performed until the desired result (e.g., pressure) is obtained. 
     Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.