Solenoid device and image forming apparatus therewith

A solenoid device comprising:

• a solenoid including;
• a solenoid body,
• a plunger arranged selectively either in an attracted position where the plunger is pulled into the solenoid body or in a returning position where the plunger protrudes out of the solenoid body,
• an attracting coil arranged in the solenoid body, the attracting coil generating, when a voltage is applied thereto, an attracting force that causes the plunger to move from the returning position to the attracted position,
• a retaining coil arranged in the solenoid body, the retaining coil generating, when a voltage is applied thereto, a retaining force that causes the plunger to move to the attracted position and that is weaker than the attracting force of the attracting coil, and
• a biasing member which biases the plunger toward the returning position;
• and
• a control portion which controls operation of the solenoid, wherein
• when performing attracting operation to move the plunger from the returning position to the attracted position, the control portion first starts to apply the voltage to the retaining coil and then starts to apply the voltage to the attracting coil, and,
• when performing returning operation to move the plunger from the attracted position to the returning position, the control portion first stops applying the voltage to the retaining coil and then applies a voltage to the retaining coil immediately prior to completion of the returning operation.

An image forming apparatus comprising:

• a solenoid device including:
• a solenoid including;
• a solenoid body,
• a plunger arranged selectively either in an attracted position where the plunger is pulled into the solenoid body or in a returning position where the plunger protrudes out of the solenoid body,
• an attracting coil arranged in the solenoid body, the attracting coil generating, when a voltage is applied thereto, an attracting force that causes the plunger to move from the returning position to the attracted position,
• a retaining coil arranged in the solenoid body, the retaining coil generating, when a voltage is applied thereto, a retaining force that causes the plunger to move to the attracted position and that is weaker than the attracting force of the attracting coil, and
• a biasing member which biases the plunger toward the returning position;
• and
• a control portion which controls operation of the solenoid, wherein
• when performing attracting operation to move the plunger from the returning position to the attracted position, the control portion first starts to apply the voltage to the retaining coil and then starts to apply the voltage to the attracting coil;
• an image forming portion forming an image on a sheet;
• a sheet conveying passage conveying the sheet to the image forming portion;
• and
• a movable member driven by the plunger of the solenoid device.