Potential Control adjusts Charge/Development bias and LD power to maintain a constant image output.

Charge roller, development roller, OPC drum and laser unit involve with imaging process.

Charge bias (Vc) is a bias for charge roller. Applying a charge bias to the OPC drum increases the potential of the OPC drum.

Development bias (Vb) is a bias for development roller. When a development bias is applied to developer (carrier), the OPC drum which is charged the opposite bias from development part attracts toner.

Development potential (Vd – Vb) is the ability to attract the toner to the OPC drum. A larger development potential increases the amount of toner adhesion.

In image density adjusting, the potential control process creates an ID pattern patch using the “bias for ID pattern creation” which has a lower density and lower Charge/Development bias than for printing.

With the results of Vsp (the ID sensor output from ID pattern patch) and Vsg (the ID sensor output from bare surface of the OPC drum), the potential control process adjusts the development bias so that the amount of toner adhesion becomes a specified target value.

Charge/Development Bias is done with the following operation. The operation time differs depending on the line speed.

  • ID sensor Vsg Adjustment
    The machine adjusts the LED strength of the ID sensor so that the value of Vsg (the charge which is detected from the bare surface of the OPC drum) is in the range of 4.0V ±0.5V. When Vsg is detected as not within the target range three times, SC370 (ID sensor error) appears.
  • Developer Stirring (0 to 5 seconds)
    The machine agitates the developer and reads the µ sensor output.

  • Bias Compensation
    The machine compensates the development bias (Vb) using the Vsp/Vsg ratio. The machine also compensates charge bias (Vc) and LD power based on the Vb result.

    Vsp/Vsg

    Toner Density

    Vb Compensation SP

    High

    High

    SP3-235-011

    Slightly high

    Slightly high

    SP3-235-012

    Correct

    Correct

    SP3-235-013

    Slightly low

    Slightly low

    SP3-235-014

    Low

    Low

    SP3-235-015

    Fig. 1: Relation b/w Dev. bias and Toner adhesion amount