Variable force solenoid

A solenoid comprising:

• coil means for inducing a magnetic flux when supplied with electrical current;
• an actuator supported for linear displacement;
• first spring means having a positive spring constant for applying to the actuator a force that changes as the displacement of the actuator changes from a reference position;
• second spring means having a negative spring constant over the operating range of actuator displacement for applying to the actuator a force that changes in the opposite direction and by substantially the same amount as the change of force of the first spring means as the displacement of the actuator position changes from a reference position;
• a magnetic circuit through which the induced magnetic flux passes tending to displace the actuator in accordance with the magnitude of electrical current supplied to the coil means;
• and
• bearing means for supporting the actuator against movement transverse to the direction of actuator displacement and for permitting relative and substantially unrestricted displacement of the actuator in the displacement direction.

A solenoid comprising:

• coil means for inducing a magnetic flux when supplied with electrical current;
• an actuator supported for linear displacement;
• first spring means having a positive spring constant for applying to the actuator a force that changes as the displacement of the actuator changes from a reference position;
• second spring means having a negative spring constant over the operating range of actuator displacement for applying to the actuator a force that changes in the opposite direction and by substantially the same amount as the change of force of the first spring means as the displacement of the actuator position changes from a reference position;
• a magnetic circuit through which the induced magnetic flux passes tending to displace the actuator in accordance with the magnitude of electrical current supplied to the coil means;
• and
• a valve that includes:
• a valve body defining a bore therein;
• a source of pressurized fluid;
• an inlet port connecting the fluid pressure source to the valve bore;
• an outlet port connected to the valve bore for supplying fluid to a hydraulic circuit;
• an exhaust port connecting the valve bore to a relative low pressure;
• a valve element moveable within the valve bore by the actuator having means for opening the closing communication between the inlet port and the outlet port and between the outlet port and exhaust port;
• and
• feedback means for tending to move the valve element toward the position where communication is closed between the inlet port and outlet port.

A solenoid comprising:

• coil means for inducing a magnetic flux when supplied with electrical current;
• an actuator supported for linear displacement;
• first spring means having a positive spring constant for applying to the actuator a force that changes as the displacement of the actuator changes;
• second spring means having a negative spring constant for applying to the actuator a force that changes as the displacement of the actuator position changes;
• a magnetic circuit through which the induced magnetic flux passes tending to displace the actuator in accordance with the magnitude of electrical current supplied to the coil means;
• first means for adjusting the actuator to a first extremity of its operating displacement range while the coil means is electrically deenergized;
• and
• second means for adjusting the actuator to a second extremity of its operating displacement range while the coil means is supplied with its maximum operating electrical current.