DE102008056967A1 - Method for regulating width of characters to be printed on print substrate by electrographic printer, involves comparing measurement signal with preset threshold signal based on which light energy transferred from generator is controlled - Google Patents

Abstract

The method involves charging a photoconductor with a charging potential (EP). An area comprising a pixel on the photoconductor is exposed and discharged as a raster field by a character generator. The field is developed with a toner by a developing unit of a developing station. An amount of toner on the raster toner field is measured by a sensor e.g. capacitive sensor or optical sensor, and a measurement signal is produced. The signal is compared with a preset threshold signal, and light energy (L1) transferred from the generator is controlled based on the comparison result. An independent claim is also included for an arrangement for regulating width of characters to be printed on a print substrate by an electrographic printer.

Description

Electrographic printing or copying machines are known, see, for. B. WO 98/39691 A2 ( US 6,246,856 B1 ). In such a printing or copying device are charged to a charged by a charger to a charging photoconductor element, for. As a photoconductor belt or a photoconductor drum, generated by a character generator charge images of the images to be printed by discharging to a discharge potential. Subsequently, the photoconductor element is moved past developer stations, one color per color in color printing. These transport z. B. toner and carrier existing developer to the photoconductor element. According to the charge images on the photoconductor element, toner is transferred to the photoconductive element and colors it. In color printing, the toner images are collected on a transfer ribbon to Farbtonerbild and finally transferred to a printing substrate and fixed on this. The exact course of the printing process can WO 98/39691 A2 are removed, the contents of which are hereby incorporated into the disclosure.

The respective image to be printed is stored as an electronic image z. B. in a printer control of the printing device. This controls the character generator, z. As an LED comb, the one the electronic Image corresponding optical image generated by exposure transferred to the charged photoconductor element as a charge image becomes. A developer station then adds the charge image developed a toner image on the photoconductor element.

• – die Aufladung des Fotoleiterelements auf ein Aufladepotential;
• – die Entladung des Fotoleiterelements auf ein Entladepotential;
• – die Einfärbung der Ladungsbilder auf dem Fotoleiterelement durch die Entwicklerstationen;
• – den Umdruck der Tonerbilder auf ein Transferband und auf einen Bedruckstoff.

The conversion of the electronic image into a toner image on the photoconductor element is thus controlled by the printer controller, which has to regulate the process parameters relevant to the generation of the toner images. These process parameters concern

• The charging of the photoconductor element to a charging potential;
• The discharge of the photoconductor element to a discharge potential;
• The coloring of the charge images on the photoconductor element by the developer stations;
• - The transfer of toner images on a transfer belt and on a substrate.

• – Bei der Regelung der Aufladung des Fotoleiterelements kann das Oberflächenpotential des Fotoleiterelements gemessen werden, z. B. mit einem Potentialsensor, und in Abhängigkeit des Messwertes z. B. der Koronastrom eines Aufladekorotrons so eingestellt werden, dass das Aufladepotential auf dem Fotoleiterelement einen vorgegebenen Sollwert annimmt.
• – Die Tiefe der Entladung des Fotoleiterelements durch den Zeichengenerator zur Erzeugung der Ladungsbilder kann ebenfalls über die Messung des Potentials von entladenen Bereichen auf dem Fotoleiterelement auf einen Sollwert geregelt Werden. Dabei wird die Lichtenergie des Zeichengenerators so eingestellt, dass die Entladetiefe auf dem Fotoleiterelement entsprechend dem eingestellten Druckkontrast-Sollwert erreicht wird.
• – Die Einfärbung der Ladungsbilder durch eine Entwicklerstation kann schließlich mit Hilfe einer Tonermarke auf dem Fotoleiterelement geregelt werden. Dazu kann z. B. ein BIAS-Potential an einer das Fotoleiterelement einfärbenden Entwicklerwalze geregelt werden, z. B. wenn die Entwicklung der Ladungsbilder nach dem Jumpprinzip erfolgt. In Abhängigkeit der zwischen den Ladungsbildern und der Entwicklerwalze bestehenden Potentialdifferenz werden die Ladungsbilder mehr oder weniger stark einge färbt. Dabei ist die Einfärbung der Ladungsbilder vom eingestellten Druckkontrast abhängig.

In DE 10 2006 058 580 A1 ( WO 2008/071741 A1 ) describes how the process parameters can be regulated:

• In controlling the charging of the photoconductor element, the surface potential of the photoconductor element can be measured, e.g. B. with a potential sensor, and depending on the measured value z. B. the corona of a Aufladekorotrons be adjusted so that the charging potential on the photoconductor element assumes a predetermined setpoint.
• The depth of the discharge of the photoconductor element by the character generator for generating the charge images can also be regulated to a desired value by measuring the potential of discharged regions on the photoconductor element. In this case, the light energy of the character generator is adjusted so that the discharge depth is achieved on the photoconductor element according to the set pressure contrast setpoint.
• The coloring of the charge images by a developer station can finally be regulated by means of a toner mark on the photoconductor element. This can z. B. a BIAS potential on a photoconductive element coloring developer roller can be controlled, for. B. if the development of the charge images takes place according to the jump principle. Depending on the existing between the charge images and the developer roller potential difference, the charge images are colored more or less strongly. The coloring of the charge images depends on the set pressure contrast.

Out DE 102 46 733 A1 a method is known which indicates how a change in the setting of the print contrast (light, dark, economic) z. B. can be implemented by an operator delay on the printed image. For this purpose, the setpoint of the toner mark control, the depth of discharge or the BIAS potential at the developer station is changed accordingly. The new setting of one or more of these parameters causes the charge images on the photoconductor element to be colored according to the newly adjusted print contrast.

In DE 102 50 827 B3 ( US 7,927,078 ), a method is described in which the temperature dependence of the photoconductive element is compensated. This dependence is that the photoconductive element becomes more sensitive to rising temperature and discharges deeper at a given light energy. To compensate for this temperature dependence, it is proposed to regulate the light energy to be emitted by the character generator in such a way that the discharge depth does not change. For this purpose, a discharge mark is applied to the photoconductor element by the character generator, which is measured by a potential sensor. Depending on the measured value, the character generator is controlled in such a way that the depth of discharge on the photoconductor element does not change despite changing the temperature.

Out EP 0 916 113 B1 ( US 6,081,677 A ) discloses a method for optimizing halftone display on a photoconductor. The process parameters influencing the print image are set as a function of a raster toner mark. This is the optical density of the raster toner brand determined and dependent on the BIAS potential of the developer roller or the toner concentration changed in the developer station.

By Control of the bias potential at the developer roller can be the character / font width be set. By character / font width is meant how wide or how fat a pressure device a given Speaks character or font. By changing the Character width can be the appearance of the printed image and the Affect toner consumption. The following is only of character width spoken.

In the control of the character width is according to the in EP 0 916 113 B1 Halftone method described a raster controller used in which an optical sensor measures the amount of toner on a raster toner brand and the BIAS voltage of the developer roller varies depending on the measurement result. However, this variation can lead to negative effects. For too much variation z. B. against the BIAS potential in Volltoneinfärbung the Volltoneinfärbung may be impaired or there may be air breakthroughs, air discharges or flashovers in the gap between the developer roller and the photoconductive element.

The to be solved by the invention problem is a Specify a method and arrangement for controlling the character width, where the negative effects mentioned above do not occur.

This Problem is with a method according to the features of claim 1 and with an arrangement according to the Characteristics of claim 8 solved.

• – ein Bildpunkte aufweisender Bereich auf einem vorher aufgeladenen Fotoleiterelement wird durch einen Zeichengenerator als Rasterfeld durch Entladung erzeugt,
• – das Rasterfeld wird durch eine Entwicklereinheit einer Entwicklerstation mit Toner eingefärbt und damit zu einem Rastertonerfeld entwickelt,
• – die Tonermenge wird auf dem Rastertonerfeld durch einen Sensor gemessen und ein davon abhängiges Messsignal erzeugt,
• – das Messsignal wird mit einem vorgegebenen Sollsignal, das der angestrebten Zeichenbreite zugeordnet ist, verglichen und in Abhängigkeit der evtl. Abweichung wird die vom Zeichengenerator abzugebende Lichtenergie z. B. durch PI-Regelung solange verändert bis Messsignal und Sollsignal gleich sind.

In the method according to the invention, the following steps are carried out to control the character width:

• A pixel area on a previously charged photoconductor element is generated by a character generator as a grid by discharge,
• The grid is colored by a developer unit of a developer station with toner and thus developed into a halftone toner field,
• The amount of toner is measured on the raster toner field by a sensor and a measurement signal dependent thereon is generated,
• - The measurement signal is compared with a predetermined desired signal, which is associated with the desired character width, and depending on the possible deviation is emitted from the character generator light energy z. B. changed by PI control until the measuring signal and setpoint signal are the same.

The grid can, as in EP 0 916 113 B1 described, consist of pixels, wherein the size of the pixels determines the printed image. By changing the light energy emitted by the character generator, the size of the pixels can be adjusted with the result that the printed image on the printing material is lighter or darker. If the pixels overlap on the photoconductor element, the solid coloration is achieved.

further developments The invention will become apparent from the dependent claims.

As a sensor, a capacitive sensor or an optical sensor can be used. Their structure is known, he can z. B. EP 0 946 905 B1 be removed.

The Raster toner field can be at different points of the printing unit be measured after its production in the developer station. For example, at the exit of the developer station on the photoconductor element, on the transfer element (eg in color printing) or on the substrate be measured.

So long the pixels do not overlap, so not completely form exposed surface, it is advantageous that the Character generator can be controlled so that its emitted light energy in the region of saturation of the photoconductor element at fully exposed areas. you can thus be optimal for the generation of the pixels Adjust light energy.

• – eine Aufladeeinheit, die ein Fotoleiterelement auf ein Aufladepotential auflädt,
• – einen Zeichengenerator, der auf dem aufgeladenen Fotoleiterelement ein aus Bildpunkten zusammengesetztes Rasterfeld entlädt,
• – eine Entwicklereinheit einer Entwicklerstation, die das Rasterfeld zu einem Rastertonerfeld entwickelt,
• – einen Sensor, der die Tonermenge auf dem Rastertonerfeld oder dessen optische Dichte misst und ein davon abhängiges Messsignal abgibt,
• – eine Regelschaltung, die die Differenz zwischen Messsignal und einem der einzustellenden Zeichnbreite entsprechendes Sollsignal ermittelt und in Abhängigkeit der Abweichung den Zeichengenerator derart steuert, dass die von ihm abgegebene Lichtenergie ein Rasterfeld erzeugt, dessen vom Sensor gemessenes Messsignal dem Sollsignal entspricht.

An arrangement for regulating the character width of printed characters generated by an electrographic printing device can have the following features:

• A charging unit that charges a photoconductive element to a charging potential,
• A character generator which discharges on the charged photoconductor element a grid composed of picture elements,
• A development unit of a developer station which develops the grid into a halftone toner field,
• A sensor which measures the toner quantity on the halftone toner field or its optical density and emits a measurement signal dependent thereon,
• - A control circuit which determines the difference between the measurement signal and one of the set drawing width corresponding desired signal and controls the character generator in response to the deviation such that the light energy emitted by it generates a grid whose measured by the sensor measurement signal corresponds to the desired signal.

By the method according to the invention the initially described negative print image effects, such as air breakthroughs, air discharges in the developer gap or impairment of the Volltoneinfärbung be avoided because the BIAS potential is no longer varied, but the light energy of the character generator.

Based an embodiment shown in the figures is, the invention will be further explained.

It demonstrate

1 a section of a printing unit with a photoconductor element with functional units arranged thereon and with a transfer belt;

2 a characteristic that represents the dependence of the discharge potential of the light energy at full-surface exposure.

In the explanation of the invention is based on a printing device, as in DE 102 50 827 B3 is described DE 102 50 827 B3 is hereby incorporated into the disclosure. The printing device works accordingly DE 102 50 827 B3 , it is referred to. A photoconductor element 1 is through a charger 2 , z. B. a corotron, charged to a charging potential. Subsequently, by a character generator 3 , z. As an LED comb, on the photoconductor element 1 Generates charge images of the images to be printed. This is the photoconductor element 1 discharged. Through at least one developer station 4 with a developer roller 5 As an example of a developer unit, the charge images are toned with toner into toner images. The following is called a developer unit 5 a developer roller 5 z. B. a jump roller used at such a BIAS potential (in 1 not shown) so that the charge images on the photoconductor element 1 Be colored according to the set pressure contrast. For color printing z. B. five developer stations 4.1 . 4.2 . 4.3 . 4.4 and 4.5 along the photoconductor element 1 arranged, which dye one after the other charge images with different colors. The individual color toner images are transferred to a transfer belt 6 at a transfer station 7 reprinted and collected on this to the color image. The color image is finally at a transfer station 9 on a substrate 8th reprinted and fixed there. This operation of a printing device is off DE 102 50 827 B3 is known and will therefore not be explained further. The rest along the photoconductor element 1 arranged units, such as a cleaning unit 10 , or along the transfer belt 6 arranged units such as cleaning corotron 11 , Cleaning brush 12 , Toner transfer unit 13 are known on DE 102 50 827 B3 will be referred to.

Between the character generator 3 and the first developer station 4.1 can be a potential sensor 14 can be arranged, the potential of on the photoconductor element 1 produced brands. For example, a charging mark can by the charger 2 on the photoconductor element 1 be applied, whose potential from the potential sensor 14 is measured in order to regulate the charger. This mark can be applied in a mark track outside the printing area. As a potential sensor, a sensor accordingly EP 0 946 905 B1 be used.

According to the invention, the output of the developer station 4 another sensor 15 arranged with the amount of toner one of the developer unit 5 developed Rastertonerfeldes can be measured. Sensors that can be used for this measurement are known. They can be realized as a capacitive sensor or optical sensor. Examples of such sensors are in EP 0 946 905 B1 described. The measurement result can then z. B. are used to adjust the light energy of the character generator.

For example, before the transfer station 7 such a sensor 15 adjacent to the photoconductor element 1 be arranged so that it the amount of toner one on the photoconductor element 1 generated grid can measure. The amount of toner can be on the transfer element 6 or the substrate 8th be measured. This is made up of pixels or raster points. This can be done by the character generator 3 on the photoconductor element 1 an area hereinafter referred to as a grid to unload a charge image, which is composed of individual pixels that form the grid. Depending on the desired brightness of the printed image, the pixels cover more or less the grid. An example of such a grid can EP 0 916 113 B1 be removed.

The grid is toned by the respective developer station with toner and thus developed into a halftone toner field. The amount of toner on the halftone toner patch is a measure of the amount of toning and coverage of the screen with toner. This amount of toner is passed through the sensor 15 measured and depending on the measurement result of the character generator 3 readjusted so that the light energy emitted by him generates a grid that corresponds to the desired target grid. By selecting the desired grid z. B. in the printer control then the character width of the characters to be printed can be set.

In 2 shows the dependence of the discharge potential EP of the light energy LI at full-surface exposure. With rising of the character generator 3 emitted light energy becomes the photo conductor element 1 discharge more until saturation is reached. Subsequently, the discharge potential no longer changes. Since the grid consists of pixels, the character generator can 3 be controlled so that it operates in the saturation region. By adjusting the light energy with which the character generator 3 the photoconductor element 1 exposed, the size of the pixels can be influenced.

Because the light energy of the character generator 3 is controlled by the grid coloring control, a special discharge depth control is no longer required.

The grid may in turn be in the mark track of the photoconductor element 1 can be arranged to avoid interference with the printed image.

The for the regulation of the character generator 3 required control circuit can be integrated into the printer control. Your construction can be appropriate DE 10 2006 058 580 A1 be executed.

The halftone toner field can be measured at various points on the printing device. This can be done by the sensor 15 adjacent to the photoconductor element 1 in front of the transfer station 7 be arranged as in 1 shown. The sensor 15 can also be adjacent to the transfer element 6 can be arranged to the raster toner field on the transfer element 6 to eat. Finally, the sensor can 15 adjacent to the substrate 8th be arranged so that the raster toner field on the substrate 8th is measured.

1

Photoconductor element

2

Charger

3

character generator

4

developer station

5

developer roller

6

transfer tape

7

transfer station

8th

substrate

9

transfer station

10

cleaning unit

11

Reinigungskorotron

12

cleaning brush

13

transfer unit

14

potential sensor

15

capacitive or optical sensor

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 98/39691 A2 [0001, 0001]
• - US 6246856 B1 [0001]
• - DE 102006058580 A1 [0004, 0032]
• - WO 2008/071741 A1 [0004]
• - DE 10246733 A1 [0005]
• - DE 10250827 B3 [0006, 0024, 0024, 0024, 0024, 0024]
• US 7927078 [0006]
• - EP 0916113 B1 [0007, 0009, 0013, 0027]
• - US 6081677 A [0007]
• - EP 0946905 B1 [0015, 0025, 0026]

Claims (13)

Method for controlling the character width of characters to be printed by an electrographic printing device on a printing substrate, - in which a photoconductive element ( 1 ) by a charger ( 2 ) is charged to a charging potential, - in the area having a pixel on the charged photoconductor element ( 1 ) as a grid by a character generator ( 3 ) is exposed and unloaded in places, - in which the grid by a developer unit ( 5 ) a developer station ( 4 ) is developed with toner to a raster toner field, - in which the amount of toner on the raster toner array by a sensor ( 15 ) is measured and a dependent measurement signal is generated and - in which the measurement signal is compared with a predetermined desired signal and the light energy to be output from the character generator is controlled in dependence of a deviation. Method according to Claim 1, in which the sensor ( 15 ) is realized as a capacitive sensor Method according to Claim 2, in which the sensor ( 15 ) is realized as an optical sensor. Method according to one of Claims 1 to 3, in which the raster toner field at the output of the developer station ( 4 ) is measured. Method according to one of Claims 2 to 4, in which the halftone toner field is formed on a transfer element ( 6 ) is measured. Method according to Claim 5, in which the halftone toner field is printed on the printing substrate ( 8th ) is measured. Method according to one of the preceding claims, in which the character generator ( 3 ) is controlled in such a way that in the area of the saturation of the photoconductive element in the case of full surface exposure ( 1 ) is working. Arrangement for controlling the character width of characters produced by an electrographic printing device on a printing substrate, - in which a charging unit ( 2 ), which is a photoconductive element ( 1 ) charges to a charging potential, - in which a character generator ( 3 ) provided on the charged photoconductive element ( 1 ) discharges a pixel-containing grid onto a discharge potential, - in which a developer unit ( 5 ) a developer station ( 4 ), which develops the grid to a raster toner field, - in which a sensor ( 15 ), which measures the amount of toner on the raster toner field and outputs a measurement signal dependent thereon, and - in which a control circuit is provided which determines the difference between the measurement signal and a desired signal of a predetermined Rastersollfeldes and controls the character generator in response to the deviation such that the generated by him light energy generates a grid that corresponds to the grid target field. Arrangement according to Claim 8, in which the sensor ( 15 ) is a capacitive sensor. Arrangement according to Claim 8, in which the sensor ( 15 ) is an optical sensor. Arrangement according to Claim 8, 9 or 10, in which the sensor ( 15 ) in front of the transfer station ( 7 ) adjacent to the photoconductor element ( 1 ) is arranged. Arrangement according to Claim 8, 9 or 10, in which the sensor ( 15 ) adjacent to the transfer element ( 6 ) is arranged to the raster toner field on the transfer element ( 6 ) to eat. Arrangement according to Claim 8, 9 or 10, in which the sensor ( 15 ) adjacent the substrate ( 8th ) is arranged to the Rasterertonerfeld on the substrate ( 8th ) to eat.