Electrophotography – Control of electrophotography process – Having temperature or humidity detection
Reexamination Certificate
1999-07-06
2001-02-06
Brase, Sandra (Department: 2852)
Electrophotography
Control of electrophotography process
Having temperature or humidity detection
Reexamination Certificate
active
06185382
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an operational method for a developer station, in particular for an electrographically operating printer or copier, in which toner is supplied in a controlled manner to a developer and the two components are mixed to form a homogenous developer mixture.
DESCRIPTION OF THE RELATED ART
In electrography, also called xerography, an original to be duplicated is imaged, by means of exposure, on a uniformly charged semiconductor material with high dark resistance (also known as a photoconductor). The charge image that arises on the semiconductor material by partial discharge of the semiconductor material is exposed in the developer station to a powder material (developer/toner mixture) that consists of very fine particles of thermoplastic material that are standardly colored as needed, and that have previously been electrostatically charged. The particles thereby adhere to the still-charged points of the charge image, which thereby becomes visible. This powder image, or toner image, is then transferred onto an insulating print material, e.g. a sheet of paper, a film, or the like, by for example applying the print material onto the toner image and electrically charging it from the back. In the subsequent fixing station, the toner image transferred onto the print material is fixed, e.g. by means of heat, which causes the thermoplastic powder to melt, or by means of chemical solvents that are sprayed on.
In the developer station, toner is supplied to the developer in controlled fashion. In order to achieve a uniform distribution of toner, the two components must be mixed. This causes the temperature of the mixture to increase. In addition, temperature increases occur in the developer mixture due to supply of heat via already-fixed papers during duplex printing via the photoconductor. High external temperatures in the region of the developer station can also lead to an increase of temperature of the mixture.
If an upper limit temperature of the developer mixture of approximately 46° C. is exceeded, clots can occur in the developer mixture that lead to errors in the print image. In addition, the coloring of the photoconductor drum, which takes place in the developer station, and thus the print quality, change dependent on the operating temperature of the developer mixture. This is the case in particular after the activation of the apparatus during the transition from the first printing with a “cold mixture” to the “warmed-up for operation” apparatus.
German published patent document DE 38 18 352 A1 specifies an image production means with a developer station. The heat produced by the various aggregates is carried away to the outside. The image production means contains a temperature sensor whose signal controls a means for dissipating the heat dependent on the set temperature.
From Japanese patent document JP 61-120176 A (cf. abstract in “Pat. Abstr. JP Sect. P. 140, P 507), it is known to cool the developer station in order to keep the developer substance at a constant quality. The heat of an inner container that houses the developer station is carried away, with the aid of a liquid, to an outer container that surrounds the inner container, which outer container contains a thermoelectrical cooling element.
From the Japanese patent documents JP-A-58-083875, JP-A-62-050851 and JP-A-03-172876, respective developer stations are known in which the temperature of the developer mixture is determined directly or indirectly with the aid of temperature sensors. On the basis of the determined temperature, an operational variable of the developer station is generally influenced.
SUMMARY OF THE INVENTION
The present invention is based on the object of providing a method for a developer station that enables a print image that is as uniform as possible, independent of the operating temperature of the developer mixture.
This object is achieved by a method for monitoring and controlling the temperature of the developer station and its developer mixture, in particular of the developer/toner mixture of an electrographically operating printer or copier, having the following steps: production of a temperature signal of the developer/toner mixture by means of a temperature sensor, supplying of the temperature signal to a control unit, influencing of at least one operational variable of the developer station by the control unit on the basis of the temperature signal of the developer/toner mixture produced by the temperature sensor, the discharging of the photoconductor drums and the illumination strength of the exposure units being corrected individually on the basis of the acquired temperature of the developer mixture for the influencing thereof in order to obtain a maximally uniform print image from the first printing up to the apparatus warmed-up for operation.
The at least one temperature sensor is advantageously arranged in the developer/toner mixture. By this means, it can acquire the actual temperature of the mixture. Through the use of several sensors, a better assessment of the temperature situation in the developer station can be obtained independently of local temperature deviations.
In the invention, the temperature sensor is arranged on the housing of the developer station, whereby the housing is made of heat-conducting material. By this means, on the one hand local temperature peaks of the developer station that can lead to local clottings are compensated by the conducting of heat via the housing, and on the other hand a possibility of economical external attachment of the temperature sensor(s) is created.
In addition, at least one additional temperature sensor is arranged in the developer/toner mixture. This arrangement of sensors both on the housing and in the interior of the developer station is particularly advantageous if the temperature difference between the inner and the outer region is of interest specifically at the beginning of operation or after a forced pause in the ready-for-operation mode.
In the inventive method for monitoring and controlling the temperature of the developer station and its developer mixture, in particular of the developer/toner mixture of an electrographically operating printer or copier, the following steps are executed:
production of a temperature signal of the developer/toner mixture by means of a temperature sensor
supplying of the temperature signal to a control means
influencing of at least one operational variable of the developer station by the control means, on the basis of the temperature signal, produced by the temperature sensor, of the developer/toner mixture.
According to the invention, the influencing of at least one operational variable is the correction only of the temperature of the developer station, e.g. by specific cooling using one or more cooling assemblies, or by means of temporary deactivation of the fixing station, and thus deactivation of the copying or printing operation.
According to the invention, the discharging of the photoconductor drums and the illumination strength of the exposure units is corrected individually on the basis of the acquired temperature of the developer mixture, in order, as mentioned above, to obtain a maximally uniform print image from the first printing (“cold mixture”) up to the apparatus “warmed up for operation.”
In a specific construction, the at least one operating variable is the temperature of the developer/toner mixture, and its influencing takes place by means of deactivation of the developer station if the temperature exceeds an upper boundary value. Clots are likewise avoided by this means. The entire copier and print operation is preferably halted. The copier or, respectively, printer can thereby remain in a ready-for-operation mode, until the temperature has again fallen below the upper boundary temperature.
Further advantages, features and possible applications of the invention result from the following specification of an embodiment on the basis of the drawing.
REFERENCES:
patent: 4888618 (1989-12-01), Ishikawa
patent: 5034772 (1991
Bremmer Peter
Knott Joseph
Thiemann Peter
Brase Sandra
Oce Printing Systems GmbH
Schiff & Hardin & Waite
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