Electrophotography – Control of electrophotography process – Control of developing
Reexamination Certificate
1999-08-06
2001-12-11
Grainger, Quana M. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of developing
C399S062000
Reexamination Certificate
active
06330406
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a toner concentration detecting apparatus and a program storage medium for this apparatus, which is utilized for an image forming apparatus such as an electrophotographic printing apparatus used a liquid developing system.
Description of the Related Art
In a conventional image forming process using a developer that contains charged toner particles in a carrier liquid, the image quality is influenced by the concentration of toner particles and the electric charge of toner particles in the developer. Consequently, it is necessary that the concentration of toner particles in the developer is kept stable. Therefore, for example, Japanese Patent Application Laid-Open No. HEI 11-52737 discloses a technology that controls the toner concentration by detecting the electric conductivity of the developer, by using orthogonal electric fields. In another technology, a light transparency factor is used to control the toner concentration.
However, in the method detecting the light transparency factor, there are problems that dust on an optical window has to be cleaned and a method for a color image has to be established. And in the method detecting the electric conductivity, there exists the influence of ions (counter ions and excess ions) besides the toner particles. Therefore, there is a problem to be solved how to detect the electric conductivity by only the toner particles, by eliminating or decreasing the influence of the counter ions and excess ions.
Japanese Patent Application Laid-Open No. SHO 50-145146 discloses a toner concentration controlling method and an apparatus thereof, which disposes a pair of electrodes and applies an alternating pulse to the electrodes and detects a toner concentration by measuring the electric conductivity between the electrodes. However, in this method, the influence of ions contained in the developer is not considered, therefore there is a problem that the toner concentration can not be detected accurately.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a toner concentration detecting apparatus and a program storage medium for this apparatus and a data storage medium for this apparatus, which can eliminate the influence of ions and can accurately measure a toner concentration in a developer that contains charged toner particles in the carrier liquid, by eliminating the influence of ions by switching the direction of electric field generated by electrodes disposed facing each other with the developer between the electrodes.
According to the present invention, for achieving the objects mentioned above, there is provided a toner concentration detecting apparatus, including a first electrode and a second electrode which are disposed face to face with a developer between said electrodes, two power supplies having opposite polarities, each of which is connectable for applying a voltage to said first electrode and said second electrode at the same time, a switching means which switches the polarity of said first and second electrodes by switching from one power supply to the other power supply, after one power supply has applied a voltage to said first electrode and said second electrode for a designated time, a detecting means which detects current flowing between said first electrode and said second electrode, at the time after applying voltage to said first electrode and said second electrode and after the polarity of said electrodes has been switched, and a calculating means which calculates a toner concentration of said developer, based on detected current values.
According to the present invention, in a toner concentration detecting apparatus, there is provided a program storage medium, in which the following steps are included: applying voltage to a first electrode and a second electrode which are disposed face to face with a developer between said electrodes from one of a plurality of power supplies for a designated time, switching polarity of said power supplies by switching from one of the power supplies to the other of the power supplies, after said voltage is applied to said electrodes from one of the power supplies, detecting current flowing between said first electrode and said second electrode, at the time after applying voltage to said first electrode and said second electrode and after switching the polarity of said power supplies, and calculating a toner concentration of said developer, based on detected current values.
According to the present invention, in a toner concentration detecting apparatus and a program storage medium for this toner concentration detecting apparatus, said toner concentration may be calculated by using a table which shows the relation between the toner concentration and the current values which change under the influence of the concentration of toner particles. Or said toner concentration may be calculated by using a peak value of a detected current due to the concentration of toner particles in a range in which said detected current values change. Or said toner concentration may be calculated according to a slope in a graph of detected current from the time when said electric field is reversed to the time when said detected current values reach a peak value due to concentration of toner particles in a range where a change in said detected current values occurs. Or said toner concentration may be calculated according to a time from the time when said polarity of said power supplies is switched to the time when said detected current values reach a peak value due to toner particles at a certain range where said detected current values change. Or said toner concentration may be calculated by the relation between a current value due to ions and a current value due to toner particles at a certain range where said detected current values change.
According to the present invention, said first electrode and said second electrode may be rotating cylindrical electrodes, and additionally cleaners, which clean surfaces of said rotating cylindrical electrodes, can be provided.
According to the present invention, in a toner concentration detecting apparatus, a data storage medium is provided, which stores data constituting a table, which shows the relation between the toner concentration and the current values due to toner particles flowing between a first electrode and a second electrode disposed face to face with a developer between the electrodes.
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patent: 915982 (1997-01-01), None
patent: 11-52737 (1999-02-01), None
patent: 11-65297 (1999-03-01), None
Grainger Quana M.
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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