EP1141787B2 - Method and device for adjusting toner concentration in an electrographic process - Google Patents

Abstract

The invention relates to a method for adjusting an electrographic printing or copying process. Information to be printed is generated as a toner intermediate image on a support for intermediate images (4, 122, 130, 136, 144) and is subsequently transmitted from a reprinting surface (130, 144) to a recording medium (2, 114) in a reprinting zone (5, 132, 146). A toner mark is produced on a electrographic support for intermediate images (4, 130, 144). Said toner mark is at least partially scanned on the support for intermediate images (4, 122, 136) and then removed from the support for intermediate images (4, 122, 136). The toner concentration is adjusted in a developing station (8) by means of the measured value. Transfer of the toner intermediate image from the reprinting surface (130, 144) to the recording medium (2, 114) is at least temporarily prevented in the period between the production and the removal of the toner mark. The invention especially provides two operating states.

Description

The invention relates to a method and a device for controlling an electrographic printing or copying process. More particularly, the invention relates to a method and system for controlling toner concentration in a toner / developer mixture.

In the EP 403 523 B1 An electrographic process is described in which a number of process parameters are monitored and controlled, including toner concentration in a developer station. For this purpose, it is provided to produce a toner mark on a photoconductor drum, to scan the mark with a reflection light sensor on the photoconductor drum and to use the measured value for controlling the toner replenishment in the developer station. The full-area toner mark is generated at the lateral edge of the photoconductor drum, so that it is only in the region of the edge holes and thus not in the actual writing area of the recording medium or the photoconductive drum with respect to the web-shaped, provided with edge holes recording medium. This results in a number of disadvantages:

For the first, the toner mark is thus to make only relatively small, whereby the scanning surface and thus the measurement accuracy is limited, in particular transversely to the transport direction of the photoconductive drum or the recording medium. Second, it is sometimes useful to control a variety of parameters of the electrographic process, apply a toner mark in the actual writing area of the photoconductor drum and scan. In particular when using sheet-shaped recording media, e.g. of so-called continuous paper, but then creates waste, because the so-printed record carrier for printing with other information is no longer available. Third, due to the process, edge effects occur at the edges of a photoconductor, e.g. of the electric field, whereby the validity of a measurement in this area is weakened. The narrower a toner mark is, the more such edge effects overlap.

In the WO 97/17535 A an electrophotographic printing apparatus is described which contains compensating elements, in particular rockers, springs and other tendons, which are intended to avoid variations in the position of the recording medium in the region of the transfer printing zone. This is particularly necessary in a duplex mode in which the web-shaped recording medium is passed twice through the same transfer station. With regard to the regulation of the electrographic process, however, nothing significant can be inferred from this publication.

In the DE 198 01 521.6 (Sign of the applicant 980102DE A control method for the toner-developer mixture, a so-called two-component developing system, in an electrographic printer or copier is described. In this method, a toner mark is scanned at at least two locations with respect to the transport direction of the photoconductor drum. To achieve sufficient scanning accuracy with this method, it is necessary that the toner mark be sufficiently wide. It would be particularly advantageous if the toner mark could also extend into the actual writing area of the photoconductor drum.

In the DE 197 49 651.2 (Sign of the applicant 971104DE ) an electrophotographic printer is described, which can process both recording medium with edge perforation and recording medium without edge perforation. For this purpose, an aggregate with a friction drive is provided, which can be swiveled in and out of a photoconductor drum so precisely that the recording medium returns to its original position after swiveling off and on again with respect to the photoconductive drum. The components described there are designed so that the pivoting on and off, for example, in the course of a service operation. On the other hand, such a printer is suitable for printing a recording medium without edge perforation wider than a recording medium with edge perforation. An edge hole-free recording medium can then be printed by the photoconductive drum in the region of the drum in which the edge perforation is located in the case of an edge-punched recording medium. With this advantage, however, there is the disadvantage that the toner mark on the unperforated web-shaped recording medium in its writing area must be re-printed and thus in turn waste arises.

From the US 5,387,965 A and from the US 4,468,112 A are known electrographic processes in which the toner concentration is determined in a developer station and compared with a desired value. The setpoint is dependent on a second measurement in which a toner mark is evaluated.

It is an object of the invention to provide a method and an electrographic system in which a toner density monitoring can take place and at the same time the highest possible printing width can be achieved on the recording medium.

This object is achieved by the invention specified in the independent claims. Advantageous developments of the invention are the subject of the dependent claims.

According to a first aspect of the invention, the information to be printed is produced as a toner intermediate image on an intermediate image carrier with a photoconductor drum and later in a transfer zone from a transfer printing surface, for example from the surface of the photoconductor drum or from a transfer transfer ribbon, to a recording medium transfer. To control the toner density, a toner mark is produced on the electrographic intermediate image carrier, the toner mark is scanned on the intermediate image carrier at least in regions, and the toner mark is subsequently removed again from the intermediate image carrier. In particular, the density is scanned at the toner mark. The toner concentration is then controlled with the measured value, in particular density value, in a developer station, so that the coloration can be kept constant. In the period between the generation of the toner mark on the intermediate image carrier and the removal of the toner mark from the intermediate image carrier, a transfer of the toner intermediate image from the transfer printing surface to the recording medium is at least temporarily prevented. This inhibition of the transfer is prevented in particular during a period by the toner mark passes the transfer zone. The prevention of the transfer can be done in particular by separating / lifting the recording medium from the transfer printing surface.

The invention provides for the operation of an electrographic printing or copying device in particular two operating states. In the first operating state, the so-called measuring cycle, a toner mark is produced on the intermediate image carrier, the density of the toner mark is scanned, and the toner mark is then removed again from the intermediate image carrier. The sampled toner density value is used to control the toner concentration in the developer station, and finds particular influence in a toner concentration set point and / or in a control threshold. In the second operating state, information to be printed is generated on the intermediate image carrier as a toner image and later transferred to the recording medium. In the second operating state, the toner concentration is controlled in particular with the toner concentration or control threshold determined from the first operating state.

According to the invention, in the first operating state, the recording medium is at least temporarily separated or lifted from the transfer printing surface, in particular from the intermediate image carrier. The invention is therefore suitable for producing the toner mark on the intermediate image carrier in a region in which the information to be printed on the recording medium is also output. The recording medium is in particular web-shaped and can be made of paper, for example.

As an intermediate carrier on which the toner mark is produced, in particular a photoconductor drum is provided. The record carrier is separated from it for at least one revolution or lifted off. In a further embodiment of the invention, a photoconductor belt is used as the first intermediate image carrier and / or a transfer belt as the second intermediate image carrier. Information to be printed is generated on the first intermediate image carrier, then transferred to the transfer belt and finally transferred from the transfer belt to the recording medium.

In particular, density values of a plurality of toner marks can be used to determine the desired value in the toner concentration control. The different toner marks may come from a plurality of measuring cycles which are far apart in time or may be formed in a continuous measuring cycle, in particular with one or more revolutions of the photoconductive drum.

For separating the recording medium from the transfer printing surface, it is possible in particular to use a fast-switching, high-precision mechanical lifting device. In this case, it is particularly provided that the recording medium before lifting and after Wiederanschwenken with respect to the transfer station both in the transport direction and transverse to the transport direction in almost the same position. In order to separate the recording medium from the transfer printing surface, it is optionally possible to move the recording medium or to move the transfer printing surface or the transfer printing element. In a further variant for preventing the transfer printing, instead of or in addition to the mechanical movement, an electrophotographic variable in the region of the transfer printing station is changed so that a transfer printing is prevented. For example, to reduce the electrical voltage on a transfer corotron.

By the invention, two operating states of the device are created, which are used alternately in time. The operating state in which the toner mark is generated and evaluated and no transfer to the Auzeichnungsträger takes place is timed between the other operating state in which printing information is printed on the recording medium.

An advantage of the invention is in particular that the toner mark can be designed very wide, up to the entire width of the intermediate image carrier, such as a photoconductor drum. This allows the toner mark in particular after in the DE 198 01 521.6 be evaluated in several places.

The toner mark can also be positioned anywhere within the printing width of the intermediate image carrier. These capabilities not only increase the accuracy of measurement against narrow toner marks, but also provide the ability to use different methods of evaluating the toner brand rather than evaluating the toner density. For example, an evaluation of the shape of the toner mark produced is possible or its comparison with a desired shape. This further makes it possible to optimize the color toner evaluation methods. Different evaluation methods can be combined into one overall evaluation, eg color-specific evaluation methods differing with respect to the toner color and / or color-specific properties of the toner mark sensor are taken into account.

Due to the adaptability of the toner mark, the toner marker's evaluation method can be designed with regard to its position, size and shape in such a way that independence from the toner color can be achieved. This is particularly true even in the case where an optoelectronic toner mark sensor operates in a narrow wavelength spectrum of light, e.g. only in one color, and its light has a direct effect on the reflection and absorption behavior of the toner pigments. In this case, in particular, the shape recognition of a large-area mark can be advantageously used.

In a second aspect of the invention, toner marks are cyclically generated and scanned in relatively large page intervals in an electrographic process, for example only after a few thousand pages of printing. In the intervening printing intervals, the toner concentration then becomes otherwise, i. only based on other measured variables. Such another measurand may e.g. the toner concentration measured in the developer station with a toner concentration sensor. From the measured value (toner density, toner mark shape, etc.) determined by the toner mark, a desired value is determined, e.g. for the toner concentration or for a control threshold and the toner concentration regulated with it. This toner concentration control to be used in the intervals between the toner mark measurements in a developer station can be carried out in a manner known per se.

According to the second aspect of the invention, the toner post-discharge is otherwise controlled over relatively large print intervals (between the toner mark evaluation cycles). Instead of or in addition to the toner concentration control just described, the toner consumption can also be determined from the printed information, in particular the total number of printed pixels. This determination can also be made as a function of the contrast ratio set on the printing device, a specific transfer printing efficiency, the age of the toner / developer mixture, the type of toner and / or other influencing variables. With the sizes determined in this way, the toner supply to the developer station can then be regulated from a toner reservoir.

With the second aspect of the invention, the object is achieved in the intervals between the formation and measurement of the toner mark to be able to carry out a largely independent control of toner coloration in an electrophotographic process.

Embodiments of the invention will be explained in more detail with reference to some figures. From this, further advantages and effects of the invention will become apparent.

Figur 1

eine schematische Schnittdarstellung einer elektrofotografischen Druckeinrichtung,

Figur 2

elektronische Komponenten der Druckeinrichtung,

Figur 3

ein Ablaufdiagramm zum Drucken und Erzeugen einer Tonermarke und

Figur 4

eine zweite elektrografische Druckeinrichtung.

Show it:

FIG. 1

a schematic sectional view of an electrophotographic printing device,

FIG. 2

electronic components of the printing device,

FIG. 3

a flow chart for printing and generating a toner mark and

FIG. 4

a second electrographic printing device.

In FIG. 1 is a working according to the principle of electrophotography printing device 1 for web-shaped recording medium shown schematically. The web-shaped recording medium in the form of a paper web 2 is thereby supplied by a drive unit 3 with a motor-driven friction roller 19 in the direction A _{1 of} a photoconductor drum 4. Details of the drive unit 3 and other components are the DE 197 49 651.2 to be taken into the present description. The unit additionally contains movable pivot elements 15, with which the paper web 2 can be pressed against the surface of the photoconductor drum or lifted off it. They are automatically movable with an electric actuator 20, such as a stepper motor or lifting magnet. Details of suitable pivot elements are in the form of Umdruckschwingen for example from WO 97/17635 A1 known. In particular, they may be designed like the rockers 40 and 44 shown in FIG. 5 of the WO publication, and may be mounted pivotably on axes in such a way that the paper web can be swiveled in and out of length-neutral with regard to parts of the drive assembly located farther away. The content of WO 97/17635 A1 is also incorporated herein by reference.

Coming back to FIG. 1 the paper web 2 is printed in a transfer printing zone 5. For this purpose, the photoconductive drum 4, which is driven by a motor, is acted upon by different, coupled aggregates with a toner intermediate image, which is transferred to the paper web 2 in the transfer printing zone 5. A first unit is a character generator 6, which contains a light-emitting diode comb with individual controllable lighting elements and which, for example, according to WO 96/3782 A1 can be constructed. The character generator 6 can be regulated by varying the drive voltage or the drive current in its light intensity. An electronic control controls the individual LEDs according to the image information to be printed. at. The loading station is adjoined by a charging sensor 7, which measures the surface potential on the photoconductive drum 4 and emits a signal in dependence thereon. The image generated on the photoconductor 4 character dependent with the character generator 6 (charge image) is using a developer station 8 colored. The developer station 8 contains a toner reservoir 9 for receiving toner and a metering device 10 in the form of a metering roller. Depending on the toner consumption, the metering roller 10 supplies toner to a mixing chamber 11. In the mixing chamber 11 is a toner / developer mixture of ferromagnetic carrier particles and toner particles. The toner mixture is fed to a developer roller 12. The developer roller 12 acts as a so-called magnetic brush roller and consists of a hollow cylinder with magnetic strips arranged therein. The developer roller 12 transports the developer mixture to a development nip 13 between the photoconductive drum 4 and the developer roller 12. Excess developer mixture is transported back to the mixing chamber 11 via the developer roller 12. With regard to the direction of rotation B _{1 of} the photoconductive drum 4, the developer station 11 is followed by a toner mark sensor 14. The toner mark sensor 14 is an optoelectronic scanner, which may be designed, for example, as a reflection light barrier. It consists of a light source and a phototransistor as a receiver. The output signal of the phototransistor is dependent on the reflectance of the applied on the photoconductor drum 4 and colored by the developer station information. With the sensor, in particular, a toner mark is scanned, which serves to determine the color saturation, ie the applied optical density of the toner mark. The wavelength of the reflection light barrier is selected so that the scanning light has no influence on the function of the photoconductive drum 4.

The toner brand is started when calling a test routine or automatically on a regular basis, for example after 2000 printed pages. The toner mark then produced is scanned and the test pattern is evaluated, for example, in terms of color density and / or color saturation.

During the passage of the test routine or the generation of the toner mark, the paper web 2 is pivoted away from the photoconductor drum 4, so that it does not touch the surface 4a of the photoconductive drum 4 in the transfer printing zone 5. The drive unit 3 or the pressure element 15 which presses the paper web 2 against the photoconductive drum 4 are then swung away from the photoconductive drum 4.

As seen in the direction of rotation of the photoconductive drum 4 behind the transfer printing zone 5, there is a cleaning device 16, with the residual toner, which has not been released from the photoconductive drum 4 or transferred to the paper 2 in the region of the transfer printing zone 5, being removed from the photoconductive drum 4. The cleaning station 16 is constructed in a conventional manner and contains, for example, a stripping element 17, which strips off the excess toner or the carrier particles from the photoconductive drum 4. The cleaning process is assisted by a corona device 18. Moreover, further corona devices are provided in a manner known per se in the pressure device. These include, for example, a loading corotron, which is provided between the cleaning device 16 and the character generator 6. Exposure devices which serve to discharge the photoconductor drum 4 can also be arranged in the device. Further details of the electrophotographic process and the associated facilities are, for example, in the EP 403 523 B1 described.

In FIG. 2 a device controller 25 of the electrographic printer is shown, which is connected to all electronic components of the various aggregates of the device, so that the processes can be coordinated with each other. The device controller 25 is connected on the one hand to a controller 26, received in the print data to be printed and in pointwise converts the light emitting diodes of the character generator 6 controllable signals. These signals are transmitted to the controller 27 of the character generator. Furthermore, the device controller 25 is connected to a controller 28 which controls electrophotographic parameters such as the voltages of corotron wires.

The photocell drum 4 scanning toner mark sensor 14 has electronic components 29, which are also in communication with the device controller 25. The controller 30 of the developer station 8 exchanges data with the device controller 25 on two sides. The toner concentration sensor 21, which measures the concentration of the toner in the toner / developer mixture in the mixing chamber 11 of the developer station 8, has an electronic assembly 31, which is also connected to the device controller 25.

Finally, the device control 25 is still connected to the electronic control 32 of the drive unit 3. In particular, the controller 32 controls components 33 of the stepping motor which moves the paper web 2 and the electronic components 34 which activates the stepping motor 20 or a corresponding lifting magnet for the pressing elements 15. Of course, the various pressure elements 15 may also be equipped with their own stepper motors or solenoids, so as to be able to accomplish an individual pressure of the rockers. Furthermore, the device controller 25 is connected to an electronic unit 35, which effects the toner delivery from an external toner reservoir into the developer station. Within the developer station, further electronics can be provided which controls the metering of the toner from the toner reservoir 9 into the mixing chamber 11 by means of the metering roller 10.

Based on FIG. 3 Now, the operation of printing and the toner concentration control will be described in more detail. In the method steps S1 to S5, a first operating state is shown in which printing data are transferred to the paper web 2. In step S1, it is checked if print data exists. If this is not the case, the printing device switches to a stand-by state, in which various units such as the photoconductive drum, transfer corotrons, the transport unit etc. are set to a low power consumption.

As soon as the device controller 25 receives a signal from the controller 26 that pressure data is available, it activates the aggregates involved, in step S3 the electro-photographic relevant aggregates and in step S4 the transport unit 3. Here, in particular, the servomotor 20 is activated by which the paper web 2 is pivoted to the surface of the photoconductor drum 4. Furthermore, the drive motor is activated, which is the friction transport roller 19 is set to transport the paper web in motion. Thereafter, the print data to be output via the character generator 6 written on the photoconductor drum 4 as a toner intermediate image, the toner intermediate image on the photoconductor drum in the developer gap 13 of the developer station 8 applied to the photoconductive drum 4 and reprinted in the transfer zone 5 on the paper web 2. Later, the thus-printed toner image is fixed on the recording medium 2 in a fixing device. During the normal printing phase (steps S1 to S5), the toner concentration in the developer station 8 is controlled by a toner concentration control. With the sensor 21, the toner concentration in the developer station 8 is permanently detected and maintained by appropriate Nachförderung with the conveyor 10, a constant toner developer mixture in the mixing chamber 11.

As an alternative to controlling the toner concentration with the toner concentration sensor 21, it is also possible to control the amount of toner per unit of time conveyed by the device 10 by counting the converted, set pixels in the controller 26 and / or other toner consumption determining quantities. such as use the contrast adjustment of the image, the temperature of the photoconductive drum or the like to determine the toner delivery amount.

In step S6 it is checked whether the end of a print job has been reached. If this is the case, the printing procedure is finished. If not, then in step S7 it is checked whether a page counter which is successively equal to zero with each print page from an initial count N ₀ = 2000. If not, the page counter is decremented by one value in step S8, and the next page can be reprinted (step S5).

If the page counter N = 0, the printing operation is terminated in step S11 and a second operation mode for generating a toner mark is started. At the same time = 2000 is set at step S10, the page counter to the initial value N _0th

After 2000 pages in each case, the normal printing process is interrupted and a review of the current development conditions carried out using a toner mark. For this purpose, first the paper web 2 in the transfer printing zone 5 is swiveled away from the surface of the photoconductive drum 4 by means of the pressing elements 15. The paper transport is also stopped.

In step 59, the value of the page counter is stored in a memory of the printer controller 25.

The steps S12 to S17 describe a second operation state in which a toner mark is written on the photoconductor 4 and evaluated to modify the toner conveyance control which occurs during the transfer printing phase (S5) in the normal printing operation.

In step S12, one or more toner marks are sequentially written on the photoconductive drum 4. The toner marks may be generated during one revolution of the photoconductive drum or, alternatively, several toner marks over several revolutions of the photoconductive drum 4. The toner marks are so wide as to enter the writing area of the photoconductive drum in which printing information is output during normal printing operation (step S5) normally be transferred to the paper web 2. If necessary, the toner mark can even extend over the entire width of the photoconductive drum 4.

Toner brands or marks produced in this way on the photoconductor drum 4 are scanned with the sensor 14 in step S13 and evaluated in the controller 25. The evaluation may be made as to the toner density produced and / or the shape of the toner mark. Depending on the type of toner used (e.g., different colors), the toner brand (s) may have different densities and / or dimensions. From the values, a value is then derived, which is compared in step S14 with a control threshold RS. If the toner density value OD of the toner marks is in the interval [RS-Δ, ..., RS + Δ], the operating mode of the toner-mark printing may be aborted in step S17 and returned to the normal printing operation mode.

On the other hand, if the toner density OD is outside the interval [RS-Δ, ..., RS + Δ], in step S15 a toner delivery is initiated and a further toner mark is produced according to step S12. This process (steps S12 to S15) is repeated until the coloring OD of the toner mark is in the required interval. Finally, at least one correction value is determined from the operating mode of the toner mark generation in step S16, with which the regulation of the toner concentration in the normal printing phase (steps S S5 to S8) is adjusted. In particular, a control threshold for the toner concentration is changed.

The toner concentration control in the printing intervals that lie between the adjustment operating conditions in which toner marks are formed and evaluated, for example, according to the in the US 4,468,112 A or US 5,387,965 A described method. Its contents are hereby incorporated by reference into the present specification. In the calibration operating state is doing From the measured toner density and the target value of the toner density, a difference is formed and the difference value used to determine a new toner concentration setpoint or a threshold for toner concentration control.

In a somewhat altered toner concentration control, a toner density measurement factor uses a factor to change a toner concentration setpoint and / or a toner concentration control threshold.

In a somewhat simplified variation of the adjustment of the toner concentration control, in which no toner concentration sensor is needed (but which may nevertheless be helpful), the amount of toner delivered to the developer station per unit time can also be adjusted in step S12. In the regulation of toner delivery during the normal printing process, other parameters such as the sum of set (i.e., black pixels), the temperature of the photoconductive drum, or the adjusted image contrast may be taken into account for more precise control.

In the FIG. 4 a further printing device is described in which at least one latent image is generated on a photoconductor belt 122 in a first printing unit 150 by a first character generator 124. With a multiplicity of developer stations 126a, 126b,... 126e, which contain toners of different colors, one or more toner intermediate images are produced on the photoconductor belt 122 in the direction of movement B. This band is a carrier of a temporary image and is therefore called an intermediate image carrier. Accordingly, latent images and toner intermediate images of different colors are generated by a second character generator 138 and a plurality of developer stations 140a to 140 in a second printing unit 152 on a second photoconductor belt 136 in the direction of movement D. This printing device is in the German patent application DE 198 561 45.8 the applicant (internal sign 981101DE ) described in detail.

The intermediate toner images are transferred at a first transfer point 128 from the first photoconductor belt 122 to a first transfer belt 130 running in the direction C and correspondingly at a third transfer point 142 from the second photoconductor belt 136 to a second transfer belt 144 which moves in the direction E. The transfer belts 130, 132 respectively collect the intermediate toner images of the different color separations and then print the full-color image on both sides, ie duplex, at a second transfer station 132 or a fourth transfer station 146 on the web-shaped recording medium 114. The recording medium 114 driven by friction rollers 116 passes through a fixing station 118 in the transport direction A for fixing the two toner images and is then cooled in a cooling device 120.

Also in this device is in accordance with the in FIGS. 1 to 3 described embodiments with the present invention carried out an operating state in which a toner mark from the character generators 124 and 138 and at least one of the developer stations 126a to 126e and 140a to 140e on at least one photoconductor 122, 136 is generated. The toner mark is then transferred to one of the transfer belts 130, 144, scanned thereon by one of the opto-electronic sensors 154, 156 and removed from the transfer belt without being printed on the paper web 114. For this purpose, the two transfer belts 130 and 144 can be lifted off the paper web 114 in the region of the transfer printing stations 132 and 146, so that the transfer to the paper 114 can be prevented.

As an alternative to the scanning of the toner mark on the transfer belts 130, 144, the toner mark can also be scanned on the photoconductor belts 122, 136 by corresponding sensors. Then either the transfer to the surfaces 130a, 144a of the transfer belt 130, 144 or the transfer to the paper web 114 is prevented. In order to lift off the transfer belts 130, 144 from the paper web 114 and / or the transfer belts 130, 144 from the photoconductor belts 122, 136, correspondingly fast switching means are provided in the region of the transfer printing zones 132, 146 and / or 128, 142.

Although the invention has been described as having between approximately 2000 print pages of the second mode of operation between two toner mark evaluation cycles (i.e., between automatically starting the first mode), this number of pages may be varied depending on the given stability of the toner concentration control, i. be increased or decreased. In the second operating state, the coloration is determined in particular only by the toner concentration control, wherein at least one of its control variables, e.g. the control threshold of the toner concentration, determined by the first operating state, namely the generation of the toner mark. This variant of the invention is therefore also to be regarded as a toner-brand-controlled toner concentration control.

Instead of in a printing device for web-shaped recording medium, the invention can also be used in a device for single sheets. The prevention of the transfer in the operating state in which a toner mark is formed and evaluated may be e.g. done in the way that the supply of a sheet-shaped recording medium is completely suppressed to the transfer station.

LIST OF REFERENCE NUMBERS

1

printing device

2

Record carrier (paper web)

3

power unit

4

Photoconductor drum

4a

Surface of the photoconductor drum

5

transfer printing

6

character generator

7

loading sensor

8th

developer station

9

Toner reservoir

10

metering

11

mixing chamber

12

developer roller

13

developer gap

14

Toner mark sensor

15

presser

16

cleaning device

17

stripping element

18

Corona facility

19

drive roller

20

Anschwenk servomotor

21

Tonerkonzentratios sensor

25

device control

26

controller

27

ZG control

28

Electrophotography control

29

Electronics of the toner mark sensor

30

Control of the E-Station

31

Electronics from 21

32

Electronics from 3

33

Electronics of the engine

34

Electronics of the actuators

35

Electronics for toner extraction

114

paper web

116

capstan

118

fuser

120

cooling device

122

first photoconductor band

124

first character generator

126a..126e

developer stations

128

first transfer point

130

first transfer band

130a

Surface of the first transfer belt

132

second transfer point

136

second photoconductor band

138

second character generator

140a..140e

developer stations

142

third transfer point

144

second transfer band

144a

Surface of the second transfer belt

146

fourth transfer point

150

first printing unit

152

second printing unit

154

Toner mark sensor

156

Toner mark sensor

A, A ₁

Paper transport direction

B

Direction of movement of the first photoconductor belt

B ₁

Direction of rotation of the photoconductive drum

C

Direction of movement of the first transfer belt

D

Direction of movement of the second photoconductor belt

C

Direction of movement of the second transfer belt

Claims (14)

1. A method of regulating an electrographic printing or copying process, in which information to be printed is generated as an intermediate toner image
   on an intermediate image carrier (4, 122, 130, 136, 144)
   and is later transferred from a transfer printing surface (4a, 130a, 144a) of the intermediate image carrier (4, 122, 130, 136, 144) onto a recording medium (2, 114) in a transfer printing zone (5, 132, 146), wherein
   a toner mark is generated as an intermediate toner image on the particularly electrographic intermediate image carrier (4, 130, 144),
   the toner mark on the intermediate image carrier (4, 122, 136) is sensed at least in regions
   and the toner mark is subsequently again removed from the intermediate image carrier (4, 122, 136),
   the toner concentration in a developer station is regulated with the sensed value, particularly density value,
   the transfer of the intermediate toner image of the toner mark from the transfer printing surface (4a, 130a, 144a) of the intermediate image carrier (4, 122, 130, 136, 144) onto the recording medium (2, 114) is at least temporarily prevented in the time span between the generation and the removal of the toner mark in that the recording medium (2, 114) is lifted off from the transfer printing surface (4, 130a, 144a) of the intermediate image carrier (4, 122, 130, 136, 144) and the recording medium (2, 114) is stopped, and wherein
   the recording medium (2, 114) is present in the transfer printing zone (5, 132, 146) during the time span.
2. The method according to claim 1, wherein the prevention of the transfer printing is effected during the time span during which the toner mark passes the transfer printing zone (5, 128, 132, 142, 146).
3. The method according to one of the claims 1 or 2, wherein the toner mark is generated on the intermediate image carrier (4, 122, 136, 130, 144) in a region in which the information to be printed onto the recording medium (2, 114) is also output.
4. The method according to one of the preceding claims, wherein the recording medium (2, 114) is web-shaped and in particular, composed of paper.
5. The method according to one of the preceding claims, wherein a photoconductor drum (4) is employed as an intermediate image carrier and the surface of the photoconductor drum (4) is employed as a transfer printing surface.
6. The method according to claim 5, wherein the recording medium is lifted off from the transfer printing surface of the photoconductor drum (4) for one revolution thereof.
7. The method according to one of the claims 1 to 4, wherein a photoconductor belt (122, 136) or a photoconductor drum (4) is employed as a first intermediate image carrier and a transfer belt (130, 144) is employed as a second intermediate image carrier, the information to be printed being generated on the first intermediate image carrier (122, 136) and being subsequently transferred onto the transfer belt (130, 144), and the surface of the transfer belt (130, 144) being employed as a transfer printing surface.
8. The method according to claim 7, wherein the sensing of the toner mark takes place on the transfer belt (130, 144).
9. A method of operating an electrographic printing or copying device having an intermediate image carrier (4, 122, 136) on which an intermediate image can be generated corresponding to the information to be printed on a recording medium (2, 114), and having a developer station (8, 126a to 126e, 140a to 140e), comprising:

   - a first operating state in which a toner mark is generated on the intermediate image carrier (4, 122, 136, 130, 144), the toner mark is subsequently sensed, particularly with regard to its density, and is then again removed from the intermediate image carrier (4, 122, 136, 130, 144), and the sensed value, particularly toner density value, is employed for the regulation of the toner concentration in the developer station (8, 126a...126e, 140a...140e), as well as

   - a second operating state in which information is generated on an intermediate image carrier (4, 122, 136, 130, 144) as a toner image and is transfer-printed onto the recording medium (2, 114) later, wherein

   - in the first operating state, the recording medium (2, 114) is present in the transfer printing zone (5, 132, 146) and the recording medium (2, 114) is at least temporarily lifted off from the surface of the intermediate image carrier (4, 122, 136, 130, 144), wherein the recording medium (2, 114) is stopped.
10. The method according to claim 9, wherein a switch into the first operating state is made after a predetermined number of printed pages of the second operating state.
11. The method according to claim 10, wherein the sensed density values of a plurality of toner marks, particularly a plurality of toner marks between which device operating phases of the second operating state have been, are employed in common for the regulation of the toner concentration in the developer station (8).
12. The method according to one of the claims 9 to 11, wherein the toner concentration in the developer station (8, 126a to 126e, 140a to 140e) is regulated in the second operating state in that a rated toner concentration value or a regulation threshold is formed from a toner density value determined in the preceding first operating state and in that the toner concentration in the developer station (8, 126a to 126e, 140a to 140e) is identified with a toner concentration sensor (21).
13. The method according to one of the preceding claims, wherein the sensed density value of the toner mark is employed for regulating the toner delivery in the developer station (8, 126a to 126e, 140a to 140e) of the device.
14. An electrographic printing or copying device having an intermediate image carrier (4, 122, 136, 130, 144) on which an intermediate image can be generated corresponding to the information to be printed onto a recording medium (2, 114), comprising

    a) a control (25)

    a1) for producing a first operating state in which a toner mark is generated on the intermediate image carrier (4, 122, 136, 130, 144), the toner mark is subsequently sensed and is then again removed from the intermediate image carrier (4, 122, 136, 130, 144), and

    a2) for producing a second operating state in which information is generated on the intermediate image carrier (4, 122, 136, 130, 144) as a toner image and is transfer-printed onto the recording medium (2, 114) later, wherein

    a3) the transfer printing of information onto the recording medium (2, 114) is at least temporarily prevented in the first operating state, wherein the recording medium (2, 114) is stopped, and

    b) having transfer printing prevention means (15, 20) for preventing the transfer printing in the first operating state in which the recording medium (2, 114) is present in the transfer printing zone (5, 132, 146),

    b1) wherein the transfer printing prevention means (15, 20) lift the recording medium (2, 114) off from the surface of the intermediate image carrier (130, 144).

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