Adjustable center pole

#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.

#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.

#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.

#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.

#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'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.