Electrophotography – Control of electrophotography process – Control of developing
Reexamination Certificate
2001-03-14
2003-04-01
Grainger, Quana M. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of developing
C399S058000
Reexamination Certificate
active
06542704
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printing device and method including a liquid developing device, a liquid developing method and a related printer including the device, and more particularly, to a liquid developing device which can retain an ink concentration and ink amount for use during printing.
2. Description of the Related Art
A liquid developing device forms a developing unit included in a wet-type electrophotographic printer, such as a printer, copier, facsimile device, for example. The liquid developing device includes a storage tank which stores ink, which is a mixture of toner and carrier, and supplies a developing unit with the stored ink. The developing unit develops an electrostatic latent image formed on a photoconductor belt with the ink. The toner included in the ink is attracted onto the photoconductor belt by electric charge. The toner travels inside the carrier, is adhered onto the photoconductor belt, and forms a toner image corresponding to the electrostatic latent image. The toner image is transferred onto a paper so as to form a desired image thereon.
The ink which includes the toner remaining after being used for developing the image is collected into the storage tank. The collected ink mainly includes carrier, thus the concentration of the ink in the storage tank becomes low. The liquid developing device uses ink, whose concentration is 3% and volume is 400 ml, for example. In this case, if the liquid developing device successively prints a predetermined image onto 400 to 500 papers with printing density of 5%, the concentration of the ink becomes lower than 2%. Thus, the printing can not be properly accomplished. The concentration of ink indicates the weight percentage of toner included in the ink. The printing density indicates the percentage of an area occupied by an output image in the entire printing area on the paper.
Some carrier is adhered onto the photoconductor belt without being collected into the storage tank. This results in a decrease in the amount of ink inside the storage tank, hence failing in printing performance.
In this structure, hence, the liquid developing device needs to adjust the concentration and amount of the ink stored in the storage tank. Such a liquid developing device is disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H11-184258. When the concentration of the ink stored in the storage tank is equal to or lower than a predetermined level, the liquid developing device discharges the stored ink, and adds concentrated ink and carrier, thereby to keep a predetermined amount of the ink stored in the storage tank.
While adjusting the concentration of the ink, the liquid developing device needs to suspend the printing operation. That is, the adjusting and the printing can not be performed at the same time. Hence, if the concentration of the ink gets lower while successively developing images onto a large number of papers, the liquid developing device adjusts the concentration during the suspension of the developing. Hence, the printing is achieved only with low efficiency.
Generally speaking, some colors of inks are more likely to be used. Thus, if the adjustment of the concentration is not successfully performed before the developing, an image is output with the frequently-used inks having insufficient concentration of toner. In consideration of this, if an arithmetic logic unit which can perform data processing speedily is employed in the liquid developing device, the problem is that the liquid developing device is manufactured at a high cost.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above. It is accordingly an object of the present invention to provide a liquid developing device, adjusting a concentration and amount of ink while developing is still performed, a liquid developing device, and a printer including the device.
Another object thereof is to provide a liquid developing device, for reducing unevenness of toner colors at a low cost, a liquid developing device, and a printer including the device.
In order to achieve the above objects, according to the first aspect of the present invention, there is provided a liquid developing device comprising:
a storage tank which stores an ink, including a toner and a carrier, for developing an electrostatic latent image on a photoconductor;
an ink supply pump which sends an ink from the storage tank to the photoconductor;
a concentration sensor which measures a toner concentration of the ink to be sent to the photoconductor;
a storage-amount sensor which measures an amount of ink stored in the storage tank;
a concentrated-ink supply pump which sends a concentrated ink from an ink cartridge for storing an concentrated ink to the storage tank;
a carrier supply pump which sends a carrier from a carrier cartridge for storing a carrier to the storage tank;
an ink discharge pump which discharges an excessive ink from the storage tank to a discharge cartridge; and
a controller which controlls the concentrated-ink supply pump, the carrier supply pump, and the ink discharge pump, so as to retain a predetermined level of the toner concentration of the ink stored in the storage tank and a predetermined amount of the ink, based on a measurement value from the concentration sensor and a measurement amount from the storage-amount sensor.
According to the above structure, the ink supply pump sends the ink from the storage tank to the photoconductor. The concentrated-ink supply pump sends the concentrated ink to the storage tank. The carrier supply pump sends the carrier to the storage tank. The ink discharge pump discharges the excessive ink from the storage tank. In this structure, the liquid developing device can develop the photoconductor with the stored ink, and can retain the predetermined levels of the toner concentration and the amount of the stored ink. Therefore, the liquid developing device can successively print with ink whose toner concentration is stably controlled.
The controller may supplement the storage tank with a concentrated ink using the concentrated-ink supply pump, supplement the storage tank with a carrier using the carrier supply pump, and discharge an excessive ink from the storage tank using the ink discharge pump, based on an error between a measurement value from the concentration sensor and a predetermined value of the concentration and an error between a measurement amount from the storage-amount sensor and a predetermined amount, so that the toner concentration of the ink stored in the storage tank and the amount of the ink approach the predetermined value of the concentration and the predetermined amount, respectively.
In the above structure, the controller stores a controlling program, so as to perform PID (Proportional Integration and Derivation) controlling, proportional controlling, proportional integration controlling, etc. based on the error between the measurement value sent form the concentration sensor and the predetermined value (target value). The controller can control each of the concentrated-ink supply pump, the carrier supply pump, and the ink discharge pump, so as to approach the error between the measurement value and the predetermined value and the error between the measurement amount and the predetermined amount to 0, in accordance with the controlling program.
The controller may drive each of the concentrated-ink supply pump, the carrier supply pump, the ink discharge pump, so as to supply a concentrated ink or a carrier to the storage tank, in accordance with at least one of the error between the measurement value from the concentration sensor and the predetermined value of the toner concentration, an integrated result of the error, and a differentiated result of the error, and to supply a concentrated ink and a carrier to the storage tank or to discharge an excessive ink from the storage tank, in accordance with at least one of the error between the measurement amount from the level sensor and the predetermined amount,
Fuji 'Xerox Co., Ltd.
Grainger Quana M.
Ostrolenk Faber Gerb & Soffen, LLP
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