Bias charge roller with optimally induced AC corona
AssigneeXerox Corporation
InventorsJohn S. Facci, Michael J. Levy, Paul W. Morehouse, Jr., Rachael L. McGrath
Life of this patent
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Abstract
An apparatus and process for applying an electrical charge to a photoreceptor wherein a bias charge roll member is situated in contact or in close proximity with a surface of a member to be charged such as a photoreceptor. The bias charge roll member is supplied with an electrical bias having a variable voltage waveform onto which a DC bias is superimposed. The amount of DC bias is selected to set the signal voltage such that a minimally acceptable amount of AC corona is created sufficient for uniform photoreceptor charging while avoiding unnecessary excessive positive corona that causes excessive photoreceptor wear.
Claims21
An apparatus for applying an electrical charge to a member to be charged, comprising:
- a. a charge roll member situated proximately to a surface of the member to be charged;
- b. a power supply for supplying an oscillating voltage signal to the charge roll member;
- c. a device, interposed between the power supply and the charge roll member, for removing a selected polarity component of the oscillating voltage signal, thereby supplying a voltage signal to the charge roll member comprised of a rectified waveform with a DC bias offset;
- wherein a first and second Paschen threshold voltage exist between the charge roll member and a member to be charged;
- wherein a portion of the voltage signal exceeds the first Paschen threshold voltage, thereby inducing a corona of the same polarity as the rectified waveform;
- and
- wherein a portion of the voltage signal exceeds the second Paschen threshold voltage, thereby inducing a corona of the opposite polarity of the rectified waveform.
An apparatus for applying an electrical charge to a member to be charged, comprising:
- a. a charge roll member situated proximately to a surface of the member to be charged;
- and
- b. a power supply for supplying an oscillating polarity voltage signal to the member to be charged;
- wherein a first and a second Paschen threshold voltage exist between the charge roll member and the member to be charged;
- wherein a portion of the voltage signal exceeds the first Paschen threshold voltage, thereby inducing a first corona of the same polarity as the portion of the voltage signal that exceeds the first Paschen threshold voltage;
- and
- wherein a portion of the voltage signal exceeds the second Paschen threshold voltage by not more than about 200 volts, thereby inducing a corona of opposite polarity from the first corona.
An electrostatographic imaging system, comprising:
- a. a member to be charged;
- b. a charge roll member situated proximately to a surface of the member to be charged:
- c. a power supply for supplying an oscillating voltage signal to the charge roll member, and
- d. a device for removing a selected polarity component of the oscillating voltage signal, thereby supplying a voltage signal to the charge roll member comprised of a rectified waveform with a DC bias offset;
- wherein a first and a second Paschen threshold voltage exist between the charge roll member and the member to be charged;
- wherein a portion of the voltage signal exceeds the first Paschen threshold voltage, thereby inducing a corona of the same polarity as the rectified waveform, and
- wherein a portion of the voltage signal exceeds the second Paschen threshold voltage, thereby inducing a corona of the opposite polarity of the rectified waveform.
A process for applying an electrical charge to a member to be charged, comprising:
- a. determining a first relationship between a voltage potential of the member to be charged and various levels of direct current voltage signals supplied to a charge roll member situated in proximity to a surface of the member to be charged;
- b. selecting a desired level of voltage potential of the member to be charged;
- c. identifying a second relationship between the voltage potential of the member to be charged and various levels of input voltage signals that comprise variable voltage components in which a portion of the voltage signal exceeds a second Paschen threshold voltage, said variable voltage signals being supplied to the charge roll member situated in proximity to the surface of the member to be charged;
- d. combining the first relationship and the second relationship to determine various variable voltage signals that achieve the selected desired level of voltage potential of the member to be charged;
- e. choosing the variable voltage signal that provides essentially minimally sufficient alternating polarity corona for uniformly charging the member to be charged.
Dependencies are inferred from the claim text.