EP1714236B1 - Control device and method for controlling an electrophotographic printer or copy machine - Google Patents

Abstract

In a method or control device for controlling an electrophotographic printer or copier that has at least two developer stations, during a print operation print data is used to determine which developer stations are needed for printing of the data. In the event it is established that a developer station was not need or will not be needed for a predetermined time span, the developer station is shifted into a standby state in which at least one part of mechanical actuators of the developer station is stopped.

Description

The present invention relates to a method of controlling an electrophotographic printer or copier having at least one developer station for developing a charge latent image on a photoconductor with toner. Furthermore, it relates to a control device for such a printer or copier.

Known methods of the type mentioned initially provide different operating states or operating modes that the printer or copier can assume during operation. Examples of such operating conditions are a standby mode in which typically the functional voltages and currents of the developer stations needed to develop a charge image are shut off and the mechanical drives of the developer station are stopped. Such a standby mode is typically adopted when the printer or copier is turned on but no print data is present.

Another common operating condition is the print mode of operation, in which typically all functional voltages and currents of the developer stations are switched to nominal parameters and all drives are run with nominal parameters. Such a printing operation mode is usually started as soon as printing data exists and maintained as long as the printing data is present. During this printing operation, as stated, the drives of all developer stations run in normal operation, ie all mixing devices such as paddle wheels, paddle wheels, mixing dredgers and the like for mixing the developer and all devices for application of the developer from the developer station to the photoconductor are in operation during the print mode.

During such a printing operation, it may happen that one or more developer stations for a long time has only a very little or no toner discharge. By the term "developer" is meant in the present specification either a mixture of toner and carrier particles or a one-component developer. In the case of the one-component developer, the terms "developer" and "toner" refer to the same thing. The case of small or fading toner output occurs relatively frequently in color printers in which each color component (cyan, yellow, magenta and black) has its own developer station, if the print data does not have a color component for a long time or only to a limited extent. However, sustained low toner discharge can also occur with single-color printers, namely when a plurality of successive printed pages with little content is printed.

It has been found that in printing operation with continued low toner discharge, the developer is aged or damaged relatively rapidly, i. wears out in the developer station and only leads to poor printing results. Moreover, if a developer station is not needed for a long time during the printing operation, it itself is subject to unnecessary wear.

From the document DE 102 12 840 For example, a color electrophotographic printer having a photoconductor belt whose outer peripheral surface is chargeable with latent charge images is known. The color printer contains two developer stations. The claims are delimited against this document.

document DE 199 00 164 concerns a laser printer. After printing a large number of sheets, the normal printing operation is interrupted to the current developer conditions using a toner mark printed on the photoconductor drum. The toner mark is removed afterwards.

From the US 2002/44784 A1 For example, an electrophotographic printer or copier comprising four developer stations for developing a latent charge image on a photoconductor is known. Print data is used to determine which of the developer stations are needed to print the data. For a certain period of time, unneeded developer stations are placed in a standby state, in which a part of the mechanical drives of the developer station are stopped.

The invention has for its object to provide a method and a control device of the type mentioned, which reduces the wear of the developer and / or the device.

The invention is defined by the independent claims.

Advantageous developments are specified in the dependent claims.

In the method according to the first aspect of the invention, the toner discharge from the developer station is detected during the printing operation, and in the event that the detected toner discharge satisfies a predetermined first regeneration criterion, a developer regeneration process is started in which a charge image is formed on the photoconductor, the charge image is developed by the developer station and the developed image is removed from a cleaning device without being transferred to a record carrier and in which new toner is introduced into the developer station. Initially, the regeneration criterion is not restricted, but it is such that it indicates a persistently low toner discharge.

In the context of the solution according to the invention, the developed charge image can be removed directly from the photoconductor by a cleaning device, but it can also be first completely or partially transferred to an intermediate carrier and removed therefrom by a cleaning device. It is in the claims 1 and 26 deliberately left open, whether it is a cleaning device of the photoconductor, a possibly used intermediate carrier or both. All that is essential is that in the developer regeneration process the developed image is neither directly nor indirectly transferred to a record carrier.

Thus, by this method, deterioration of the developer can be prevented by monitoring the toner discharge, and if it is persistently low, an artificial toner flow rate is caused in the developer regeneration process. For this purpose, an "artificial" or "arbitrary" charge image is generated on the photoconductor in the developer regeneration process, the charge image is developed by the developer station and new toner is introduced into the developer station. The developed image is not transferred to a record carrier so that no record carrier committee is formed. Instead, the developed image is removed from a cleaning device, as explained in more detail below.

The first regeneration criterion is chosen to initiate the regeneration process in a timely manner before the developer is damaged or aged, but not unnecessarily early to minimize toner depletion and to avoid unnecessary interruption of printing operation. Characteristics of the printer or copier and of the developer and empirical variables are thus typically included in the selection of the first regeneration criterion.

In an advantageous development of the method, the toner discharge is determined for time intervals of a predetermined length, and the first regeneration criterion is satisfied if the average toner discharge was below a predetermined threshold value for a predetermined number of successive time intervals. A short-term increase in toner discharge in a phase with otherwise low toner discharge, which is insufficient to sustainably regenerate the developer, will not be sufficient to increase the average value of the toner discharge for this interval above the threshold, given a suitable length of the intervals. In such a case, the need for a regeneration process is still considered to exist. If, on the contrary the average value of the toner discharge during one of these intervals is above the threshold, it is assumed that the developer has been sufficiently regenerated and initially no further regeneration process is required.

The toner discharge is preferably determined on the basis of print data. In this case, preferably the number of pixels to be printed or printed is weighted with its coloring step. This is a technically very simple way to determine the toner discharge from the developer station.

If the printer or copier comprises a plurality of developer stations, it is preferable to detect the toner discharge of each of these developer stations and, in the case where the developer station development developer regeneration process is started, check to see if the detected toner discharge from the remaining developer stations meets a second regeneration criterion, and to developer stations in which the second regeneration criterion is met, a developer regeneration process has also been started. The second regeneration criterion indicates that while a developer regeneration process is not yet required, it may become necessary in the foreseeable future. Since the printing operation must be interrupted for each regeneration process, it is advantageous to carry out several regeneration processes directly after one another in this way, ie. H. to concentrate in time.

The second regeneration criterion may be a weakened or less restrictive version of the first regeneration criterion. In the context of the above-mentioned advantageous example of the first regeneration criterion, the second regeneration criterion may require that the average toner output be less than a predetermined number of consecutive time intervals the number of time intervals in the first regeneration criterion was below a predetermined threshold.

The method according to the second aspect of the invention relates to printers or copiers having at least two developer stations for developing a latent charge image on a photoconductor. According to the second aspect of the invention, during the printing operation, it is determined by the printing data which developer stations are needed to print the data, and if it is determined that a developer station was not needed for a predetermined period of time, this developer station is placed in a standby state which at least a part of the mechanical drives of the developer station are stopped.

In this state of readiness thus the mechanical components of the developer station are spared and their wear is reduced. At the same time, the developer contained in the developer station is protected because it is damaged or aged by a continuous mixing and activation, which is carried out in the printing operation. In this respect, the second aspect is closely related in content to the first aspect of the invention. While the first aspect of the invention as described above relates to a novel special mode for regenerating and thereby protecting the developer while the toner discharge remains low, the second aspect of the invention relates to a novel special mode for protecting the developer and the developer station in the event that the developer station is longer is not needed as a predetermined period of time.

In the standby state, the developer station is preferably switched so that no toner transfer between the developer station and the photoconductor can take place, for example by a suitable choice of the functional Voltages and currents. In an advantageous development, the developer station is pivoted away from the photoconductor in the standby state.

Preferably, the standby state is terminated when it is determined from the print data that the developer station is needed to print the data. The print data are preferably analyzed so far ahead that the time interval between the analysis of the print data and the time at which the image corresponding to this data is to be developed by the associated developer station is sufficient to put this developer station from the ready state into the print operating state ,

Usually, the developer must be activated in the developer station in order to be transferred to the intermediate carrier for developing the latent charge image. In a developer mixture of toner and carrier particles, this activation usually consists of mixing the developer mixture in which the toner particles are charged triboelectrically to the carrier particles. Preferably, during the standby state of a developer station, the developer contained therein is activated at predetermined intervals. Then, the developer is immediately ready for use when the developer station is returned from the standby state to the printing mode.

In an advantageous development, the number of times the developer has been activated during a standby state is counted, and if the number or total duration of the activations exceeds a predetermined threshold value, no further activations are carried out for the duration of the standby state. In this case, the developer always remains ready for operation in the standby states of shorter duration, while in the standby states it is longer Duration is waived on activations to protect the developer.

As already mentioned above, the two aspects of the invention are closely related and, like the described advantageous developments, can be combined with each other in an advantageous manner. For example, in an advantageous development, which includes both aspects of the invention, during the standby state of a developer station, the developer is activated at predetermined intervals until the first regeneration criterion is met, whereupon no further developer activations are performed in the developer station for the remaining duration of the standby state and the developer regeneration process waits until the developer station is needed to develop or until another developer station of the printer or copier launches a developer regeneration process.

In this way, on the one hand, the developer is spared during a longer standby state, on the other hand, the printing operation is not interrupted for a developer regeneration process as long as the developer station is in the standby state, i. as long as it is not needed for development. Thus, the regeneration processes can be better concentrated in time, and the number of interruptions of the printing operation can be reduced.

Figur 1

ein Blockdiagramm, das die Bestandteile eines Verfahrens nach einer Weiterbildung der Erfindung zeigt,

Figur 2

ein Flussdiagramm, das ein Verfahren zur Auswertung des Toneraustrags zeigt,

Figur 3

ein Flussdiagramm, das ein Verfahren zum Verwalten von Zuständen einer Entwicklerstation zeigt,

Figur 4

ein Flussdiagramm, das ein Verfahren zur Bereitschaftsverwaltung zeigt,

Figur 5

ein Flussdiagramm, das die zeitliche Synchronisierung von Entwickler-Regenerationsprozessen bei mehreren Entwicklerstationen eines Druckers zeigt,

Figur 6

ein Flussdiagramm, das die Einbindung eines Verfahrens nach einer Weiterbildung der Erfindung in ein herkömmliches Verfahren zum Steuern eines Druckers zeigt, und wobei

Figur 7

eine Schnittdarstellung eines Druckers ist.

For a better understanding of the present invention, reference will now be made to the preferred embodiment illustrated in the drawings, which is described by reference to specific terminology. It should be noted, however, that the scope of the invention should not be so limited since such changes and other modifications are shown in the Methods and apparatus shown, as well as such other applications of the invention as set forth therein, are considered to be common current and future knowledge of a person skilled in the art. The figures show an embodiment of the invention, wherein

FIG. 1

a block diagram showing the components of a method according to an embodiment of the invention,

FIG. 2

a flow chart showing a method for evaluating the toner discharge,

FIG. 3

a flowchart showing a method for managing states of a developer station,

FIG. 4

a flowchart showing a method for standby management,

FIG. 5

a flowchart showing the timing synchronization of developer regeneration processes at multiple developer stations of a printer,

FIG. 6

a flowchart showing the incorporation of a method according to a development of the invention in a conventional method for controlling a printer, and wherein

FIG. 7

is a sectional view of a printer.

In FIG. 7 a printer 10 is shown in a sectional view. The printer 10 has an upper printing unit 12 and a lower printing unit 14, which are of the same construction, and whose components are designated by the same reference numerals become. The printing units 12 and 14 each have a photoconductor belt 16 which is electrically charged by a charging device not shown in detail, and which is discharged point by point to generate a charge image from a character generator 18 by illumination.

The photoconductor belt 16 passes at five developer stations 20, 22, 24, 26 and 28, of which in FIG. 7 only that with reference number 20 is shown in detail, and the rest are symbolically represented by triangles. The developer stations 20 to 28 are each for developing a color component of a color image. The color components are preferably formed by the colors cyan, yellow, magenta, black and a spot color, but they can be any other color.

To generate a color component of a printed image, the character generator 18 generates a charge image on the photoconductor 16 corresponding to the color component, and this charge image is developed by the associated color toner developer station. The toner image of the color component thus obtained is at a first transfer point 29 on an intermediate carrier, here in the form of a transfer belt 30, re-printed. As an intermediate carrier but also, for example, an intermediate carrier drum can be used. The residual toner remaining in the transfer printing on the photoconductor 16 is removed from the photoconductor belt 16 by a cleaning device 32. Thereafter, the photoconductor is recharged, generated by the character generator 18, the charge image for another color component on the photoconductor 16, developed by the associated developer station 20, 22, 24, 26 or 28 and also transferred to the transfer tape 30 in such a way that superimpose the individual color components on the transfer belt 30 into a multi-color image.

Thus, a maximum of five monochrome images in the component colors mentioned above are superimposed on the transfer belt 30 to form a multicolor image (color image). Then, the transfer belt 30 is pivoted to a paper web 34, and the color image is transferred at a second transfer point 36 from the transfer belt 30 to the paper web 34 is printed. In the presentation of FIG. 7 the transfer belts 30 are shown in the pivoted to the paper web 34 state in which simultaneously the front and the back of the paper web 34 can be printed.

The residual toner, which remains on the transfer belt 30 after the transfer to the paper web 34, is removed by a transfer belt cleaning device 38. The reprinted color images are then fixed in a fuser 40 on the paper web 34.

In a conventional method of controlling the printer 10, all the developer stations 20, 22, 24, 26 and 28 are in a so-called "color ready state" during the printing operation. During the color ready state, the developer stations 20, 22, 24, 26, and 28 are mechanically pivoted into an operating position on the photoconductor. All mechanical drives of the developer stations run with nominal parameters. The mechanical drives include drives for mixing devices such as paddle wheels, mixing dredgers and / or screws as well as drives for magnetic rollers and other functional rollers for the development of the charge image. Only the functional stresses, ie the voltages required for the toner transfer between the developer station 20, 22, 24, 26 or 28 and the photoconductor belt 16 are still switched so that no toner transfer can take place. From this color ready state, the developer station can be brought to development operation in a very short time, typically less than 0.2 seconds.

The constant mixing of the developer with a paddle wheel, a screw or the like is necessary as explained above to activate the developer. Depending on the nature of the print data, however, it may be that a color component is only weakly represented for a longer period of time. This leads to a persistently low toner discharge from the developer component associated with the color component. If the developer is constantly mixed with sustained low toner discharge, it is damaged in a relatively short time and allows only a poor print image quality. In particular, there may be the case that a color component is not needed at all for a long time because the print data does not provide that color component for that time. Also in this case, the developer of the developer station, which is in Farbbereitschaft, constantly activated and therefore damaged or subjected to aging process. In addition, the developer station is operated unnecessarily, which increases its wear.

The embodiment described below shows a method of controlling the printer 10 resulting in reduced wear of the developer and developer stations 20, 22, 24, 26, and 28. This method is carried out by means of an electronic control device, which is not shown in the figures.

In FIG. 1 the essential components of a method for controlling the printer 10 according to an embodiment of the invention are shown in a block diagram. After a start in step 42, the counters BD and ts are initialized in step 44, the function of which will be explained below. Thereafter, control proceeds to a toner discharge evaluation procedure 46 in which it is determined whether the toner discharge from the developer station to which this part of the controller is related has been below a predetermined value for a long time.

If so, a developer regeneration process 48 is started. If not, control proceeds to a state manager 50 for the particular developer station. In the developer station state management 50, it is checked whether the developer station has not been or will not be needed for a predetermined period of time. If this is not the case, control returns to the toner discharge evaluation 46. However, if so, the developer station is placed in a standby state where all or at least a portion of the developer station's mechanical drives are stopped, and control proceeds to the developer station standby manager 52.

During standby management 52 it is checked if there is a color request for the color of the developer station, i. whether the developer station is needed in the foreseeable future. If so, control proceeds to step 54 where the developer station is brought into the color ready state described above. Further, under circumstances discussed below, the standby manager 52 may also start a developer regeneration process 48 from a standby state.

In FIG. 2 a flowchart of the evaluation procedure 46 of the toner discharge is shown. After a start in step 56, during the printing operation (58) in step 60, the average toner discharge from the relevant developer station is determined for a time interval of a predetermined length. In step 62, the determined average toner discharge is compared with a threshold value y. If the average toner discharge is greater than or equal to the threshold y, a regeneration monitoring counter (RZD) is set to 0 in step 64 and control proceeds to developer station state management 50 (see FIG. 1 ) Ahead.

If the average toner discharge in step 62 was less than the threshold value y, RZZ is incremented by a first increment R1 in step 66. Then it is checked in step 68 whether ROZ is above a threshold x. If not, control also proceeds to Developer Station State Manager 50. However, if RZT has reached threshold x in step 68, a first regeneration criterion is met. This first regeneration criterion indicates that the average toner discharge was below the threshold value y for a certain period of time. Prolonged low toner output would damage the developer in the developer station. In order to prevent this, the developer regeneration process 48 (see also FIG FIG. 1 ) started.

In the developer regeneration process 48 (not shown in the diagrams), the normal printing operation is initially interrupted. The character generator 18 (see FIG. 7 ) generates an artificial charge image on the photoconductor 16, which is not provided in the print data, and which is designed as a whole-area pattern with a coverage of 10% to 50%. The developed charge image is at the first transfer point 29 (see FIG. 7 ) is transferred to the transfer belt 30.

Unlike the usual transfer printing during the printing operation, the voltages and currents relevant for the transfer printing at the first transfer printing point 29 can be switched in a first embodiment such that only about 50% of the toner image is transferred from the photoconductor 16 to the transfer belt 30. The transfer belt 30 is also moved away from the transport path of the paper web 34, ie pivoted away, so that no toner from the transfer belt 30 on the paper web 34 passes. Instead, the reprinted Proportion of the toner image from the transfer belt cleaning device 38 from the transfer belt 30 cleaned. Similarly, the unimaged portion of the toner image is cleaned by the photoconductive cleaning device 32 from the photoconductor 16. By the Umdruckwirkungsgrad at the first transfer point 29 of about 50%, the cleaning work on the two cleaning devices 32 and 38 is evenly distributed.

In a second embodiment variant, the voltages and currents relevant to the transfer at the first transfer point 29 are switched so that between 75% and 100% of the toner image is transferred from the photoconductor 16 to the transfer belt 30. This proportionately larger transfer printing compared to the first variant is useful when toner marks on the photoconductor 16 are generated and analyzed to calibrate the electrophotographic components. For correct analysis of the toner mark, it is important that the photoconductor on which the toner mark is generated is free of residual toner. In the developer regeneration process, if the transfer efficiency from the photoconductor to the subcarrier is relatively low, the cleaner 32 must clear relatively much toner from the photoconductor 16 so that too much residual toner on the photoconductor 16 may remain after a cleaning pass (one revolution of the photoconductor belt) could be to produce a reliable toner brand. Therefore, in the second embodiment, a higher transfer efficiency of 75% to 100% is selected in the developer regeneration process. The remaining less than 25% of the sample can then be thoroughly cleaned by the cleaning device 32 in a cleaning cycle.

In the developer regeneration process 48, an arbitrary toner discharge from the developer station is caused. In addition, a corresponding amount of fresh toner is replenished in the developer station.

This artificial toner throughput prevents damage, aging or wear of the developer in the developer station.

To calculate the average toner discharge in step 60 of FIG FIG. 2 On the basis of the print data, the number of pixels in the color corresponding to the developer station is summed up with its coloration level. This provides a simple and sufficiently accurate method for determining toner output.

In the printer 10 of FIG. 7 In addition, the print data are stored in a page buffer (not shown) some time before the time at which the image corresponding to this data is to be developed by the developer station.

In FIG. 3 FIG. 10 is a flowchart of the developer station state management 50 of FIG FIG. 1 shown. After a start in step 70, the page buffer is evaluated with the print data in step 72. In step 74, it is determined on the basis of the print data in the page buffer whether a color request for the relevant developer station is present, ie whether print data is to be developed with the color of the toner of the developer station. If this is not the case, a counter ts is incremented by an increment dt in step 76. Then, in step 78, it is checked whether the counter ts is less than or equal to a threshold tsmax. If so, the controller exits the state manager 50 in step 80. Control could return to the toner outflow evaluation 46 in step 80, for example, but the exact relationship of the individual process parts is not specified. In any case, the toner discharge evaluation 46 and the developer station state management 50 may be parallel to each other.

However, if the counter ts has reached the threshold value tsmax in step 78, it is first checked in step 81 whether there are color requests for further colors of the print path. On the printer 10 of FIG. 7 This means that it is checked whether additional developer stations of the same printing unit 12 or 14 are required. If so, in step 82 the controller starts the standby management 52 (see FIG. 1 ) for the developer station concerned and puts this developer station in the standby state described above.

However, if it is determined in step 81 that there are no color requests for all the developer stations 20, 22, 24, 26 and 28 of the print path (ie, print engine 12 or 14), then in step 84 the standby manager 52 is also started and the developer station is placed in the ready state , In addition, however, in step 86, the electrophotography device of the print path is turned off. Relative to the printer 10 of FIG. 7 This case may occur, for example, if the paper web 34 is only printed simply, so one of the printing units 12 or 14 is not used. In this case, the electrophotography device of the printing unit which is not required is shut down in order to protect its components, for example the photoconductor 16, the character generator 18, the cleaning device 32, etc.

Briefly, steps 76-86 of state management 50 cause a developer station to go into the ready state if it has not been needed for a long time, namely, when ts is greater than tsmax. Then, with some probability, it can be assumed that the developer station will not be needed for another time, so it pays to put them in the ready state to spare their mechanical components.

If in step 74 the state management 50 of FIG. 3 a color request for the relevant developer station is detected, the counter ts is set to 0 in step 88. Then, in step 90, it is checked whether the developer station is in the standby state. If this is not the case, the status management 50 is exited in step 92.

However, if the developer station is in the standby state, it is checked in step 92 whether the electrophotography device of the printing path to which the developer station concerned belongs is switched off. If the electrophotography device is turned off, it is turned on in step 94. Thereafter, in step 96, a color request is sent to the developer station standby manager 52.

In FIG. 4 is the developer station standby 52 of FIG. 1 shown in a flow chart. After a start in step 98, a standby counter BD is initialized in step 100. In step 102, the counter BD is incremented by the increment dBD. In step 104 it is checked whether there is a color request for the relevant developer station.

If this is not the case, it is checked in step 106 whether the counter BD corresponds to a threshold value r. If not, control returns to step 102.

When the counter BD has reached the threshold r, in step 108 the developer in the developer station is activated.

In step 110, the regeneration monitoring counter (RZZ) is incremented by a second increment R2, which is incremented from the first increment R1 from step 66 of FIG FIG. 2 different can be. Then it is checked in step 112, if RÜZ is still smaller than the threshold value x, ie whether the first regeneration criterion is met.

If RÜZ is less than or equal to x in step 112, that is, no developer regeneration process is yet needed, control returns to step 100. As long as there is no color request in step 104, steps 100 through 112 are performed as described above. In this case, the developer is activated at regular time intervals whose length is predetermined by the variable r (see step 108), whereby the developer is initially kept ready for use.

If it is determined in step 112 that RZT has reached the threshold value x, ie the first regeneration criterion is met, in step 114 the developer station is swung away from the photoconductor 16. Although the first regeneration criterion is met in this state, the regeneration process 48 (see FIG. 1 ) initially not started. Instead, control proceeds to step 102. In step 102, the counter BD is again increased by the increment dBD, so that it is now greater than r. As a result, the counter BD is always greater than r in step 106, and thus the controller cyclically executes steps 102, 104, and 106 until a color request is made in step 104. In particular, no further activation of the developer is made until further notice because step 108 is no longer achieved, thereby reducing wear and aging of the developer.

If there is a color request in step 104, it is first checked in step 116 whether BD ≤ r. If so, no further activation of the developer is necessary. The counter BD then becomes 0 in step 118 and the developer station is set in the color ready state 54 described above.

If the counter BD is greater than r in step 116, the developer station is pivoted to the photoconductor 16 in step 122 and the developer is activated in step 120. The counter BD is set equal to 0 in step 124, and the developer regeneration process 48 is started.

Like the flowchart of FIG. 4 can be seen, in the standby state of the developer station, a developer regeneration process 48 is delayed despite meeting the first regeneration criterion until a color request is present in step 104, that is, until the developer station is actually needed again. This has the advantage that the printing operation does not need to be interrupted unnecessarily. Rather, in this way it is possible to synchronize the regeneration processes of different developer stations with one another, ie to concentrate them as chronologically as possible, as described below with reference to FIG FIG. 5 is explained in more detail.

FIG. 5 shows a flowchart of how the developer regeneration processes 48 different developer stations can be synchronized with each other. The synchronization process begins in step 126 with regeneration process 48 for one of the five developer stations 20, 22, 24, 26, and 28 of upper print engine 12 or lower print engine 14 (FIG. Fig. 7 ) is started, for example, by the step 68 in the toner discharge evaluation 46 of FIG. 2 , The various developer stations of the printing unit 12 or 14 are shown in the flow chart of FIG. 5 characterized by a running variable or index i, i = 1 ... 5. The counters RÜZ and BD of the i-th developer station are also provided with the index i and thus to RÜZi and BDi.

In step 128, it is checked for the upper or first printing unit 12 (DW1) and for the lower or second printing unit 14 (DW2) for all developer stations i = 1... 5 whether the associated regeneration monitoring counter (RÜZi) ≦ xi - ci is. This inequality represents for each developer station a second regeneration criterion, which is less restrictive than the first regeneration criterion, which generally has the form ROZi = xi (cf. Fig. 2 , Step 68). In this case, the index i at the threshold x indicates that different threshold values xi may be present for the different developer stations. ci is a positive number for each developer station i. Accordingly, the second regeneration criterion is met if a regeneration process in the ith developer station is not currently needed, but would become necessary in the foreseeable future represented by the variable ci.

In step 128, the control branches into two branches, namely a first branch, which begins in step 130 and in which the temporal sequence of the regeneration processes of the printing unit (DW1 or DW2) to which the regeneration process triggering developer station belongs, and a branch starting in step 132, in which the order of the regeneration processes of the developer stations of the other printing unit (DW2 or DW1) is determined.

1. 1. Die Entwicklerstation, die den Regenerationsprozess ausgelöst hat. Sie wird in Fig. 5 gekennzeichnet durch i = m. Für sie gilt, BDm = 0 und RÜZm = xm.
2. 2. Entwicklerstationen, die sich in der Toneraustrags-Auswertung 46 befinden und das zweite Regenerationskriterium erfüllen. Solche Entwicklerstationen sind in Fig. 5 gekennzeichnet durch i = n. Für sie gilt: BDn = 0 und RÜZn ≥ xn - cn.
3. 3. Entwicklerstationen, die sich im Bereitschaftszustand befinden, das zweite Regenerationskriterium erfüllen, aber das erste Regenerationskriterium nicht erfüllen. Solche Entwicklerstationen sind in Fig. 5 gekennzeichnet durch i = b. Für sie gilt: BDb ≤ rb und RüZb ≥ xb - cb.
4. 4. Entwicklerstationen, die sich im Bereitschaftszustand befinden, die das erste Regenerationskriterium erfüllen, für die jedoch keine Farbanforderung vorliegt. Solche Entwicklerstationen sind mit i = w bezeichnet. Für sie gilt: BDw > r und RÜZw > xw.

In the following, the developer stations 20, 22, 24, 26 and 28 are subdivided according to their current state into the following four classes:

1. 1. The developer station that triggered the regeneration process. She will be in Fig. 5 characterized by i = m. For them, BDm = 0 and RÜZm = xm.
2. 2. Developer stations that are in the toner output evaluation 46 and meet the second regeneration criterion. Such developer stations are in Fig. 5 characterized by i = n. For them: BDn = 0 and RZZn ≥ xn - cn.
3. 3. Developer stations, which are in the standby state, meet the second regeneration criterion, but do not meet the first regeneration criterion. Such developer stations are in Fig. 5 characterized by i = b. For them: BDb ≤ rb and RüZb ≥ xb - cb.
4. 4. Developer stations that are in the standby state that meet the first regeneration criterion, but for which there is no color request. Such developer stations are designated by i = w. For them: BDw> r and RÜZw> xw.

In the left branch of the flowchart of FIG. 5 After step 130, in step 134, the developer regeneration process for the mth developer station, ie, the developer station triggering the regeneration process, is started and RÜZm = 0 is set. In parallel, in step 136, it is checked for all the developer stations that satisfy the second regeneration criterion whether BDi = 0. If so, these developer stations are second-class developer stations labeled i = n. For the second-class developer stations, the developer regeneration process is started with a second temporal priority, ie immediately after the regeneration process of the triggering, ie m-th developer station in step 138.

If it is determined in step 136 that BDi ≠ 0, this developer station is in the standby state and thus falls into the third or fourth class.

In order for a developer regeneration process to be performed on such developer stations, these developer stations must first be brought from the standby state to the color ready state. Since this may take some time, it is preferable as in FIG. 5 3, it is first shown to perform the developer regeneration process for the first and second class developer stations. During the time required to do so, the third and fourth grade developer stations can then be brought from the standby state to the color ready state.

In step 138, it is also checked if BDi ≤ r. If so, no toner activation is needed for the particular developer station. The developer station thus belongs to the third class (i = b) and its developer regeneration process is performed in step 140 with third temporal priority. In addition, in step 140, the variables or counters BDb and RÜZb are set equal to 0.

If BDi is greater than r in step 138, the developer station belongs to the fourth class, which is indicated by i = w. For them, the toner is first activated in step 142 and BDw is set to zero. Subsequently, the developer regeneration process is started for these developer stations in step 144 with a fourth and thus lowest temporal priority, and the counter RÜZw is set to zero. The timing preference of the third category developer stations over those of the fourth category is justified by the fact that in those of the fourth category additional toner activation is to be performed which can be performed while waiting for completion of the regeneration process of the third class developer station or developer stations.

The right branch of the flowchart of FIG. 5 is essentially identical to the left branch, except that there is no first class developer station of which there is only one and that has been handled in the left branch. In particular, steps 146 to 154 of the right branch correspond exactly to steps 136 to 144 of the left branch. Step 156 waits until all developer regeneration processes are completed. Thereafter, control proceeds to the toner discharge evaluation 46.

In FIG. 6 a flow chart is shown, by which the integration of in FIGS. 1 to 5 described embodiment is explained in a known controller for a printer. Control begins in step 158 with the printer 10 turning on. In step 160, the printer 10 is in a standby mode and is waiting for data. After printing data has been received in step 162, a toner-discharge calibration process is performed in steps 164/1, 164/2 and 164/3 in developer stations 1 to 3. For the sake of clarity, the flowchart of FIG. 6 only three developer stations are used instead of the five developer stations per printing unit of FIG. 7 ,

The calibration in step 164 is a preparation mode into which the printer 10 is placed prior to the beginning of the printing operation. In the calibration step 164, operating parameters are calibrated. In this case, a transient process for regulating circuits for regulating operating parameters, which relate, for example, to the charging of the photoconductor belt 16, the discharge of the photoconductor belt 16, the toner concentration in the developer mixture or the inking, is carried out. After completion of the calibration in step 164, all three developer stations are brought into the color ready state in steps 166/1 to 166/3.

Step 168 waits until all three developer stations have assumed the color ready state. In step 170, heating of the fuser 40 (see FIG FIG. 7 ) began. In step 172, the printer 10 is in printing operation in which printing data is present. If the print data breaks down during printing, a short caster starts. If the print data aborts for longer than the post-run time, the printer is stopped in step 174. After the printer is stopped in step 176, control returns to step 160.

The toner evaluation 46 and the developer station state management 50 run as stand-alone processes besides the printing operation (step 172) and are therefore in FIG. 6 listed separately. The developer station state manager 50 proactively analyzes the page buffer of the print data and acts on the method by setting unneeded developer stations in the standby state or in color request from the standby state into color ready. The interaction of the developer station state management 50 with the method of FIG. 6 is generally symbolized by the circle "1".

Specifically, the state manager 50 monitors the print data during the printing operation (step 172) and sets one or more of the developer stations 1 to 3 in steps 178/1 to 178/3 according to the method of FIG FIG. 3 in the standby state when the counter ts has reached the threshold tsmax (see FIG. 3 , Step 78). This effect on the printing operation is in FIG. 6 represented symbolically by the circle "1-a". If a color request according to step 104 of FIG FIG. 4 is present, the developer stations are brought from the state management 50 from the standby state and the calibration (step 164) and the Color readiness (step 166) brought back into the printing process.

During calibration (step 164), blank pages are typically printed, that is, charge images are generated that can be developed but not transcoded. For example, as part of the calibration, toner marks can be printed that will not be reprinted. However, in the usual calibration, no whole-area toner patterns are produced on the photoconductor 16, as used in the developer regeneration process. This calibration is in FIG. 6 referred to as "calibration without toner discharge" (see step 164).

If a developer regeneration process is pending after completion of the standby state, it is realized by performing the calibration in step 164 with toner discharge. In this way, the regeneration process can be easily linked to a printer state or preparation mode, which is provided anyway in the printer control. Thus, for toner regeneration, no new printer state needs to be implemented.

Further, during the printing operation (step 172), the toner discharge evaluation 46 may determine whether the first regeneration criterion for a developer station that is not in the standby state is met (see FIG. Fig. 2 , Step 68). In this case, the printing operation (step 172) is interrupted and the toner regeneration process is performed by performing the calibration in step 164 with toner discharge without previously putting the developer station in the standby state. In addition, the toner output evaluation 46 tells developer station state management 50 of the need for the regeneration process, which then synchronizes possibly pending regeneration processes of the remaining developer stations according to FIG. 5 takes over.

Although a preferred embodiment has been shown and described in detail in the drawings and foregoing description, this should be considered as illustrative and not restrictive of the invention.

LIST OF REFERENCE NUMBERS

10

Electrophotographic printer

12

Upper printing unit

14

Lower printing unit

16

Photoconductive belt

18

character generator

20 to 28

developer station

29

First transfer area

30

transfer tape

32

Photoconductor cleaning device

34

paper web

36

Second transfer area

38

Transfer belt cleaning device

40

fuser

42

Start of the procedure

44

Initialization of the counters

46

Toner discharge evaluation

48

Developer regeneration process

50

Developer station state administration

52

Developers station readiness management

54

color readiness

56 to 68

Process steps of the toner discharge evaluation 46

70 to 96

Process steps of the developer station state management 50

98 to 124

Process steps of developer station standby management 52

126 to 156

Procedural steps in the synchronization of developer regeneration processes

158 to 178

Procedural steps in an implementation in a conventional control method

Claims (49)

1. Method for controlling an electrophotographic printer or copier (10) that has at least one developer station (20, 22, 24, 26, 28) for developing a latent charge image on a photoconductor (16) with toner,
   characterized in that the toner discharge from the developer station (20, 22, 24, 26, 28) is detected during the print operation and a developer regeneration process (48) is started for the case that the detected toner discharge fulfils a predetermined first regeneration criterion, comprising the steps:

   generating a charge image on the photoconductor (16), the charge image being developed by the developer station and the developed image being removed by a cleaning device (32, 38) without being transfer-printed onto a recording medium (34),

   and introducing new toner into the developer station (20, 22, 24, 26, 28).
2. Method according to claim 1, in which the average toner discharge is determined for time intervals of predetermined length,
   and in which the first regeneration criterion is fulfilled when the average toner discharge has lain below a predetermined threshold for a predetermined number of successive time intervals.
3. Method according to claim 1 or 2, in which the printer (10) or copier has a transfer belt (30) on which the developed toner image is transfer-printed from the photoconductor (16) in normal operation and from which the transfer-printed toner image is transfer-printed onto the recording medium (34).
4. Method according to claim 3, in which, in the developer regeneration process (48), the developed image is wholly or partially transfer-printed onto the transfer belt (30) and the transfer-printed portion of the image is removed from the transfer belt (30) by a transfer belt cleaning device (38), and
   in which the portion of the image that is not transfer-printed is removed from the photoconductor (16) by a photoconductor cleaning device (32).
5. Method according to claim 4, in which the developed image is transfer-printed onto the transfer belt (30) at 75% to 100% in the developer regeneration process (48).
6. Method according to any of the claims 3 to 5, in which the transfer belt (30) is moved forward of the transport path of the recording medium (34) in the developer regeneration process (48).
7. Method according to any of the preceding claims, in which whole-area patterns with a surface coverage of 10% to 50% are generated on the photoconductor in the developer regeneration process (48).
8. Method according to any of the preceding claims, in which the toner discharge is determined using print data.
9. Method according to claim 8, in which the toner discharge is determined in that the printed pixel count or the pixel count to be printed is added up, weighted with its inking level.
10. Method according to any of the preceding claims that provides a preparation mode (164) into which the printer (10) or copier is brought before the beginning of the print operation,
    and in which the printer (10) or copier is brought into the preparation mode (164) at the beginning of the developer regeneration process (48).
11. Method according to claim 10, in which the preparation mode (164) comprises one or more of the following operations:

    - powering up the developer station (20, 22, 24, 26, 28),

    - function test of the developer station (20, 22, 24, 26, 28),

    - activation of the developer,

    - calibration of the operating parameters.
12. Method according to any of the preceding claims, in which the printer or copier comprises a plurality of developer stations (20, 22, 24, 26, 28) whose toner discharge is respectively detected and in which
    for the case that the developer regeneration process (48) is started for one developer station (20, 22, 24, 26, 28), it is checked whether the detected toner discharge of the remaining developer stations (20, 22, 24, 26, 28) fulfils a second regeneration criterion, and
    in which a developer regeneration process (48) is likewise started for developer stations (20, 22, 24, 26, 28) in which the second regeneration criterion is fulfilled.
13. Method according to claim 2 and claim 12, in which the second regeneration criterion is fulfilled when the average toner discharge has lain below a predetermined threshold for a predetermined number of successive time intervals that is less than the number in the first regeneration criterion.
14. Method for controlling an electrophotographic printer (10) or copier that has at least two developer stations (20, 22, 24, 26, 28) for developing a latent charge image on a photoconductor (16),
    characterized in that during the print operation (172) it is determined using the print data which developer stations (20, 22, 24, 26, 28) are needed for printing of the data, and
    in the event that it is established that a developer station (20, 22, 24, 26, 28) was not needed or will not be needed for a predetermined time span, this developer station is shifted into a standby state in which at least one part of the mechanical actuators of the developer station (20, 22, 24, 26, 28) are stopped.
15. Method according to claim 14, in which the functional voltages of the developer station (20, 22, 24, 26, 28) are connected in the standby state such that no toner transfer can occur between the developer station (20, 22, 24, 26, 28) and the photoconductor (16).
16. Method according to claim 14 or 15, in which the developer station (20, 22, 24, 26, 28) is pivoted away from the photoconductor (16) in the standby state.
17. Method according to claim 16, in which the developer station (20, 22, 24, 26, 28) is pivoted away from the photoconductor during the standby state when the temporal duration of the standby state exceeds a predetermined threshold.
18. Method according to any of the claims 14 to 17, in which the standby state is ended when, using the print data, it is established that the developer station (20, 22, 24, 26, 28) is required for printing of the data.
19. Method according to claim 18, in which the print data are anticipatorily analyzed such that the time interval between the analysis of the print data and the point in time at which the image corresponding to these data is to be developed by the associated developer station (20, 22, 24, 26, 28) is sufficient in order to shift this developer station (20,22, 24, 26, 28) from the standby state into the print operation state.
20. Method according to any of the claims 14 to 19 in which, during the standby state of a developer station (20, 22, 24, 26, 28), the developer contained therein is activated at predetermined intervals.
21. Method according to claim 20, in which it is determined how often or how long the developer has been activated during a standby state, and
    in the event that the number of the activations or, respectively, the duration of the activation exceeds a predetermined threshold, no further activations are implemented for the duration of the standby state.
22. Method according to any of the claims 14 to 21, in which at least two printing groups (12, 14) with respectively one separate electrophotography device are provided in the printer (10) or copier, and
    in which at least a portion of the components of the electrophotography device is shut down when the last developer station (20, 22, 24, 26, 28) of the printing group (12, 14) is shifted into the standby state.
23. Method according to any of the claims 1 to 13 and any of the claims 14 to 22.
24. Method according to claim 23 in which, during the standby state of a developer station (20, 22, 24, 26, 28), the developer is activated at predetermined intervals until the first regeneration criterion is fulfilled,
    then no further developer activations are implemented in the developer station (20, 22, 24, 26, 28) for the remaining duration of the standby state, and with the developer regeneration process it is waited until the developer station is required for development or until another developer station of the printer or copier starts a developer regeneration process (48).
25. Method according to one of the claims 12 or 13 and claim 24 in which, for the case that the developer regeneration process (48) is started for one developer station (20, 22, 24, 26, 28), the developer regeneration processes (48) of the further developer stations (20, 22, 24, 26, 28) whose detected toner discharge fulfils the second or the first regeneration criterion are implemented in the following order:

    1. Developer stations that are not found in the standby state,

    2. Developer stations that are found in the standby state and that do not fulfil the first regeneration criterion, and

    3. Developer stations that are found in the standby state and that fulfil the first regeneration criterion.
26. Control device for an electrophotographic printer (10) or copier that has at least one developer station (20, 22, 24, 26, 28) for developing a latent charge image on a photoconductor (16) with toner,
    characterized in that the control device is suited to detect the toner discharge from the developer station (20, 22, 24, 26, 28) during the print operation and
    means are provided to start a developer regeneration process (48) for the case that the detected toner discharge fulfils a predetermined first regeneration criterion,
    in which developer regeneration process (48) a charge image is generated on the photoconductor (16), the charge image is developed by the developer station and the developed image is removed by a cleaning device (32, 38) without being transfer-printed onto a recording medium (34),
    and in which new toner is introduced into the developer station (20, 22, 24, 26, 28).
27. Control device according to claim 26 that is suited to determine the average toner discharge for time intervals of predetermined length,
    and in which the first regeneration criterion is fulfilled when the average toner discharge has lain below a predetermined threshold for a predetermined number of successive time intervals.
28. Control device according to claim 26 or 27, whereby the printer (10) or copier has a transfer belt (30) on which the developed toner image is transfer-printed from the photoconductor (16) in normal operation and from which the transfer-printed toner image is transfer-printed onto the recording medium (34).
29. Control device according to claim 28, whereby in the developer regeneration process (48) the developed image is wholly or partially transfer-printed onto the transfer belt (30) and the transfer-printed portion of the image is removed from the transfer belt (30) by a transfer belt cleaning device (38), and
    whereby the portion of the image that is not transfer-printed is removed from the photoconductor (16) by a photoconductor cleaning device (32).
30. Control device according to claim 29, whereby the developed image is transfer-printed onto the transfer belt (30) at 75% to 100% in the developer regeneration process (48).
31. Control device according to any of the claims 28 to 30 that triggers that the transfer belt (30) is moved forward of the transport path of the recording medium (34) in the developer regeneration process (48).
32. Control device according to any of the claims 26 to 31 that determines the toner discharge using print data.
33. Control device according to claim 32 that determines the toner discharge in that the printed pixel count or the pixel count to be printed is added up, weighted with its inking level.
34. Control device according to any of the claims 26 to 33 that provides a preparation mode (164) into which the printer (10) or copier is brought before the beginning of the print operation,
    and that brings the printer (10) or copier into the preparation mode (164) at the beginning of the developer regeneration process (48).
35. Control device according to claim 34, in which the preparation mode (164) comprises one or more of the following operations:

    - powering up the developer station (20, 22, 24, 26, 28),

    - function test of the developer station (20, 22, 24, 26, 28),

    - activation of the developer,

    - calibration of the operating parameters.
36. Control device according to any of the claims 26 to 35, wherein the printer or copier comprises a plurality of developer stations (20, 22, 24, 26, 28) whose toner discharge is respectively detected and
    that, for the case that it starts the developer regeneration process (48) for one developer station (20, 22, 24, 26, 28), checks whether the detected toner discharge of the remaining developer stations (20, 22, 24, 26, 28) fulfils a second regeneration criterion, and
    that likewise starts a developer regeneration process (48) for developer stations (20, 22, 24, 26, 28) in which the second regeneration criterion is fulfilled.
37. Control device according to claim 27 and claim 36, wherein the second regeneration criterion is fulfilled when the average toner discharge has lain below a predetermined threshold for a predetermined number of successive time intervals that is lower than the number given the first regeneration criterion.
38. Control device for an electrophotographic printer (10) or copier that has at least two developer stations (20, 22, 24, 26, 28) for development of a latent charge image on a photoconductor (16),
    characterized in that the control device, using the print data during the print operation (172), is suited to determine which developer stations (20, 22, 24, 26, 28) are required for printing of the data and,
    in the event that it determines that a developer station (20, 22, 24, 26, 28) has not been required or will not be required for a predetermined time span, means are provided to initiate that this developer station is shifted into a standby state in which at least a portion of the mechanical actuators of the developer station (20, 22, 24, 26, 28) are stopped.
39. Control device according to claim 38, wherein in the standby state the functional voltages of the developer station (20, 22, 24, 26, 28) are connected such that no toner transfer can occur between the developer station (20, 22, 24, 26, 28) and the photoconductor (16).
40. Control device according to claim 38 or 39, wherein the developer station (20, 22, 24, 26, 28) is pivoted away from the photoconductor (16) in the standby state.
41. Control device according to claim 40 that triggers that the developer station (20, 22, 24, 26, 28) is pivoted away from the photoconductor during the standby state when the temporal duration of the standby state exceeds a predetermined threshold.
42. Control device according to any of the claims 38 to 41 that triggers that the standby state is ended when, using the print data, it is established that the developer station (20, 22, 24, 26, 28) is required for printing of the data.
43. Control device according to claim 42 that is suited to anticipatorily analyze the print data such that the time interval between the analysis of the print data and the point in time at which the image corresponding to these data is to be developed by the associated developer station (20, 22, 24, 26, 28) is sufficient in order to shift this developer station (20, 22, 24, 26, 28) from the standby state into the print operation state.
44. Control device according to any of the claims 38 to 43, that during the standby state of a developer station (20, 22, 24, 26, 28), triggers that the developer contained therein is activated at predetermined intervals.
45. Control device according to claim 44 that determines how often or how long the developer has been activated during a standby state and,
    in the event that the number of the activations or, respectively, the duration of the activation exceeds a predetermined threshold, triggers that no further activations are implemented for the duration of the standby state.
46. Control device according to any of the claims 38 to 45, wherein at least two printing groups (12, 14) with respectively one separate electrophotography device are provided in the printer (10) or copier, and
    wherein the control device triggers that at least a portion of the components of the electrophotography device is shut down when the last developer station (20, 22, 24, 26, 28) of the printing group (12, 14) is shifted into the standby state.
47. Control device according to any of the claims 26 to 37 and any of the claims 38 to 46.
48. Control device according to claim 47 that, during the standby state of a developer station (20, 22, 24, 26, 28), triggers that the developer is activated at predetermined intervals until the first regeneration criterion is fulfilled, then no further developer activations are implemented in the developer station (20, 22, 24, 26, 28) for the remaining duration of the standby state, and with the developer regeneration process it is waited until the developer station is required for development or until another developer station of the printer or copier starts a developer regeneration process (48).
49. Control device according to one of the claims 36 or 37 and claim 48 that, for the case that the developer regeneration process (48) is started for one developer station (20, 22, 24, 26, 28), triggers that the developer regeneration processes (48) of the further developer stations (20, 22, 24, 26, 28) whose detected toner discharge fulfils the second or the first regeneration criterion are implemented in the following order:

    1. Developer stations that are not found in the standby state,

    2. Developer stations that are found in the standby state and that do not fulfil the first regeneration criterion, and

    3. Developer stations that are found in the standby state and that fulfil the first regeneration criterion.

Images