Starter motor solenoid with variable reluctance plunger

A solenoid for a vehicle starter, the solenoid comprising:

• a spool;
• a first coil wound on the spool;
• a second coil wound on the spool adjacent to the first coil with a passage extending through the spool, the first coil and the second coil;
• and
• a substantially solid plunger moveably positioned within the passage and configured to move in an axial direction between a first position and a second position, the plunger including a substantially cylindrical outer surface portion with a circumferential notch formed in the outer surface portion;
• a plate member positioned adjacent to one end of the spool, the plate member separated from the plunger by a radial distance, wherein the radial distance varies when the plunger moves from the first position to the second position as a result of the notch moving in relation to the plate member, wherein the notch is directly opposite the plate member when the plunger is in the first position, and wherein the notch is removed from the plate member in the axial direction when the plunger is in the second position;
• and
• a tube positioned within the spool with the plunger positioned within the tube and configured to move in the axial direction relative to the tube wherein the tube extends past the plate member at the one end of the spool.

A solenoid for a vehicle starter, the solenoid comprising:

• at least one coil with a passage extending through the coil;
• a plunger positioned within the passage and configured to slide within the passage in an axial direction between a first position removed from a plunger stop and a second position where the plunger engages the plunger stop, the plunger moveable within the passage between the first position and the second position, the plunger including an outer surface with a circumferential notch;
• a contact coupled to the plunger, the contact configured to close an electrical circuit when the plunger is in the second position such that electric current is delivered to an electric motor of the vehicle starter, the contact further configured to open the electrical circuit when the plunger is in the first position;
• a radial wall removed from the plunger stop in the axial direction and separated from an outer surface of the plunger by a radial distance, wherein the radial distance varies when the plunger moves from the first position to the second position;
• and
• a solenoid case with the at least one coil positioned within the solenoid case and the radial wall connected to the solenoid case, wherein the solenoid case includes an outside wall and the radial wall is integral with the outside wall of the solenoid case;
• the circumferential notch configured on the plunger such that the radial distance between the radial wall and the outer surface of the plunger varies when the plunger moves from the first position to the second position.