Browse Prior Art Database

AUTOMATIC TONER CONCENTRATION CONTROL

IP.com Disclosure Number: IPCOM000025659D
Original Publication Date: 1987-Feb-28
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 164K

Publishing Venue

Xerox Disclosure Journal

Abstract

Automatic Developer Control Systems suffer from several shortcomings. They often use D.C. signals which are subject to drift, there are significant phase lags around the control loop, sensor response is usually non-linear and dirt build up can be a problem for systems that use optical detection.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 4

XEROX DISCLOSURE JOURNAL

AUTOMATIC TONER CONCEN- Proposed Classification TRATION CONTROL U.S. C1.355/3DD Brian E. Springett Int. C1. G03g 15/00

Volume 12 Number 1 January/February 1987 25

[This page contains 1 picture or other non-text object]

Page 2 of 4

AUTOMATIC TONER CONCENTRATION CONTROL (Cont'd)

Automatic Developer Control Systems suffer from several shortcomings. They often use D.C. signals which are subject to drift, there are significant phase lags around the control loop, sensor response is usually non-linear and dirt build up can be a problem for systems that use optical detection.

An automatic developer control system which utilizes A.C. signals, senses the developer brush directly, is relatively linear and does not use optical detection takes advantage of developers such as conductive magnetic brush developers which are characterized by a non-linear conductivity that is dependent upon toner concentration. More specifically, an approach is proposed which involves applying an A.C. voltage of frequency, a, whose amplitude is considerably less than the normally applied D.C. bias necessary for development. A metal electrode sufficiently large to produce some degree of averaging is placed in contact with the developer brush. A current detector having a narrow band-pass filter centered at 2 GI is positioned on the input to this detector. Since the conductivity of the developer is non-linear, a second harmonic signal (as well as higher harmonics) is produced. This second harmonic signal is compared to a reference signal and the difference signal is used as a feedback control.

In examining the generation of the second harmonic signal, the conductive magnetic brush developer conductivity may be presented by:

o(v)=ooexp (CdV) (1 1

A signal represented by V=Vp+V, cos wt. is applied to the developer. Its relationship can be presented by:

o(V)=o(V )+ow )V"coSWt.+&J"W )V~cos?wt. + ... (2)

B P P

Since it is the second harmonic term that is being detected, the third term on the right side of equation (2) is selected to derive the following equation:

If V, is small compared to Vp, the D.C. Conductivity and resulting developability is relatively unperturbed. Algebraically, equation (3) may be written as:

26 XEROX DHCLOSURE JOURNAL

Volume 12 Number 1 January/February 1987

[This page contains 1 picture or other non-text object]

Page 3 of 4

AUTOMATIC TONER CONCENTRATION CONTROL (Cont'd)

Thus, the amplitude of the second harmonic depends upon the characteristics of the developer; the D.C. conductivity at the bias Vp and the constant c which characterizes the non-linearity. Since both of these may be expected to be dependent upon Tc in a quasai-linear fashion, maintaining the factor in front of cos2 wt. constant in equation (4) provides a means for keeping Tc constant.

One means of implementing the foreg...