DE2611503C2 - Electrostatic copier - Google Patents

Description

The invention relates to an electrostatic copier having a recording surface on an electrically conductive, grounded carrier, several corona discharge devices, the discharge electrodes of which are from are surrounded by an electrically conductive shield and which direct a current of corona ions onto the recording surface output, furthermore with separate energy sources, which are connected to the discharge electrodes and supply certain input currents to each of the corona discharge devices, one variable Proportion of the generated corona ion current of each discharge device flows to its shielding and as Partial flow of the input flow flows away.

In such copiers it is known that the total amount of charge given off by the discharge electrode and also the percentage that hits the shield in relation to the percentage, which reaches the recording surface of the image carrier to be charged, to a certain extent during the work process of the copier fluctuates even if the input voltage is kept constant. These Values are influenced by the charge that is previously applied to the image carrier surface, as well as due to humidity, atmospheric pressure, pollution and oxidation, the speed of movement the recording surface to be charged, etc. It is known that controlling and measuring the Total input current to a corona discharge device does not represent a sufficiently precise measure.

3. 4th

the real output current of the corona discharge cannot be detected. Namely, work more

generation device, which acts as a corona discharge device on the surface to be charged at the same time, then

meets to measure or control. As a result, the measuring devices located in the earthing path of the drum can vary.

most arrangements have been proposed, the alignment measuring only the sum of the charge currents,

A corona discharge device 5 is not able to transfer the currents to the individual

control for xerography more directly or to divide up corona discharge devices. The Sy-

to eat. stern can therefore not the conditions in normal operation

One known device that measures output charge, i. H. the charge currents of the individual corona sets to measure a corona discharge device, discharge devices in normal copier operation consists in placing a conductive test area in place of the io of the copier.

It is also known to set part of the light image carrier surface that is actually applied to an image carrier surface underneath the corona discharge device due to the discharge of a corona charge. The current that the conductive discharge direction receives charge during the test area of each corona discharge device of the copier operation of a copier is then measured individually. The total input line is measured by measuring the charge that the corona discharge device is fed to an area of the image carrier surface downstream of which is then set so that the test surface is measured by the corona discharge device, or with the desired current the corona discharge means anunter the next corona discharge means comparable parent electrometer the corona output tab above and the process is repeated, this system 20 dung volume determines this charge measurement can Maecht it necessary to remove the image carrier surface advantageously be used \ y? \ different and by a other and not exactly the same corona discharge devices to replace the landing discharge area, and also can control any amount. These electrometer systems only require individual corona discharge devices independently, however, it is apparent that electrometers are turned on and set out of relation to the others. 25 places, and these require a considerable amount of space

In reality, however, the individuals influence each other in terms of area and can only charge the charge Measure corona discharge devices in the operation of an electronic device at the points where they are located. It is not trostatic copier among each other. This is economical and undesirable for reasons of space, hence that the electrometer, other than a corona discharge device, is used to measure the charge The charge applied to the image bearing surface is one in the running 30 of the image bearing surface downstream of most of the corona direction downstream corona discharge device discharge devices within a copier can influence their charge delivery. to arrange. Moving an electrometer between dies is a variable that, by contrast, requires time due to the conductivity of the seeing different places Image carrier area is affected and which also fluctuates and makes it impossible to take measurements at the same time with the charge decay in the dark close to 35 to be carried out.

The arranged corona discharge devices can, finally, the conductive shielding is known In their charge flow, there are also direct and / or the grid of a corona charging device on the side influence. In the transmission station you can electrically isolate and with Often the corona discharge devices for part of the power supply are able to be connected in a conductive manner the image transfer and for the detachment of the sheet 40 and / or as part of the corona flow control to be mutually exclusive influence, with both turning again. In devices of this type, sensors are also through Whether or not a copy sheet is present is influenced by electrodes for controlling a corona discharge or not and what conductivity it has. The direction of flow is known

Ability of the copy sheet varies greatly with the object of the invention is to be an electrostatic Moisture and depending on the material itself What 45 copier of the type mentioned to run in such a way that will be explained in more detail later, that of each individual corona discharge device The fact that a considerable part of the transfer actually delivered charge current to simple Stromes that gets on the copy sheet, often determined by manner and accordingly according to each Page along the sheet is derived because the requirements are controlled. Is resolved

Another well-known: method of measurement and so this task, starting from an electrostatic

Controlling the charge delivery of a corona discharge copier of the type mentioned in the introduction according to

device is based on the electrical potential of the invention in that each energy source for control

Image carrier surface and the conductive carrier over the grain of the effectively used corona flow low-voltage

To let sepotential float by, for example, a voltage side via its own control circuit and a

xerographic image carrier drum is stored isolated 55 of these downstream, optionally as a setting counter-

and the electrical connection with the aid of a measuring resistor formed by a slip ring with Masst ^ or. He-

gen is produced. The current measuring arrangement can de connected that the shields of the corona

then between the floating bilateral carrier substrate and discharge devices opposite one another

Ground are switched on. It can then be a coroder of the recording material and grounded

naentladungseinrichtung turned on at the time and their 60 are arranged isolated from ground that to each

Charge current to the image carrier through this current shield a separate current feedback circuit

measuring device can be determined. This measuring arrangement is closed, the foot over the shielding

tion has the obvious disadvantage that a non-variable partial flow of the input current over the

grounded image carrier substrate must be used. Low voltage side of the associated energy source in

In addition, it has the same disadvantages as the 65 the input circuit of the corona discharge device.

previously described measuring devices adhered, fed back and at least through the measuring resistor

namely that the mutual influence of the corona is separated from the mass or earth, and that the

discharge devices and their charge currents measurement resistance or that from the

5 6

Electrode and recording surface lying discharge Further features of the invention are in the underground section, the respective energy source and the claims under protection, The invention is explained in more detail with reference to the drawing in connection with the corona discharge device to be selected, with exemplary embodiments. It by means of a switch having a switch 5 shows

tion a voltage measuring circuit for the determination of the F i g. 1 a schematic overview image of an electrical

effective to act on the recording surface of the copier operating under statography in which

used corona current can be switched in parallel. a control system for the generation of a transmission

With the invention it is possible to use an exact measurement corona charge according to the invention;

and control of the actually delivered charge io F i g. 2 an electrical switching device for the

currents of the individual corona discharge devices advises according to FIG. 1 for switching and measuring the corona

in a copier under dynamic working conditions - current signals.

to undertake. That is, the actual La- In FIG. 1 shows an electrophotographic copy output current of a specific corona discharge device 10 by placing images on a photoconductive The device can be measured while the surface 12 is being generated and then transferred from it to the normal copier with further corona discharges. Various effects act on the image carrier surface 12 devices, which also emit charge to the image carrier controlled corona discharge devices (corona surface, on a copy sheet, etc.,. Never place the Qe image carrier surface with its substrate in the usual

In principle, with the invention, the part of the stream can be completely conventional, with each corona discharge device that reaches the individual workstation conductive shielding shown briefly from the overall entrance of the copier 10 in FIG. 1 addressed current that is supplied to this corona discharge device. The image carrier surface 12 is initially peeled off by means of a tet, in order to obtain a measured value of the charge corona discharge device 14, hereinafter referred to as costrom, which is actually referred to by the corona generator. Then, a charging means to the image carrier surface reaches latent ^B: d on the image bearing surface 12 by optical This measure is based on the consideration that the exposure to an optical original scan 16 all of the Koronaentladungseinnchtung supplied formed 30 that selectively the image bearing surface 12 in the pattern of current either on the image carrier surface or on that of the original to be copied. The latent elek shielding must meet, and that if the current of trostatic image on the image carrier surface 12 then the shielding is slightly developed at a potential above in the usual way, here with one Toner powder is held, it can be returned and subtracted, in a development station 20 with magnetic brushes, in order to obtain the measured value for the actual device, which has several rotating magnetic developments, image carrier charge flow and thus the feed rollers 22. These developing rollers get 22 th charge. These measurements of the actual are applied to a voltage so that between them and the charge current can then be used to create an electric field on the image carrier surface 12. Current constant during real dynamic charging The image carrier surface 12 is next to be maintained by changing the corona input current corresponding to the corona voltage and corona discharge (with an overlaid corona discharge. This measurement can also be used for direct voltage) from one before the Transfer case, other investigation and control purposes located corona generator 24 treated. The deprived, manually or automatically, as well as wrapped and pretreated toner image is then applied to z. B. for an automatic compensation for the downstream of the image carrier surface 12 in the transfer station initiate the copy sheet in the transfer station. 45, where it is taken from the copy carrier sheet 26 by one. Each corona discharge device has two image receiving material sheets 26, hereinafter copy-separated current loops. A current loop runs from the sheet labeled, covered, which is synchronized with that of the high-voltage side of the energy source to the toner image by conventional conveying devices 28 over the circuit of the discharge electrode, then over the ionized conventional conductive sheet guide elements 13 in-air path for shielding and then over the back 50 leads. The reverse side of the copy sheet 26 is a guide loop to the low-potential side of the same energy source from a common direct voltage supra-power source. The other and separate current loop corona generator 32, a corona outlet, is exposed to the energy generation current from the same high potential side 55 on the copy sheet immediately following the transfer corona generator 32, which is connected to the carrier of the image carrier area, with an alternation to the earthed device and via earth via the voltage (possibly superimposed DC voltage) resistance current measuring circuit to the low-potential operated detachment corona generator 34 a. side of the same energy source. The current measuring circuit The lifting of the copy sheet is only in this second current loop in the illustration. It is indicated by a second copy sheet 26a, which can be seen from FIG. 4, that the entire charge current going from the electrode to a common wiper finger 40 from the image carrier / image carrier surface, but not the surface 12, has been lifted. The copy sheet 26a is carried by the stream of the shielding by the current measuring slidably by a known suction shoe 42, circuitry in this second current loop flows the RE of the ^Kopiebiatt: n a nip of a roll angel circuit is responsive only to changes in the actual 65 pair introduces which As a fusing station 44 the output current of the corona discharge device acts. Finally, the image carrier surface 12 is a change while changes in the shielding current have no self-voltage corona emission of a pre-cleaning co-influence. ronagenerators 46 exposed before the image carrier

surface with the help of an ordinary cleaning scraper 50 the toner residues are removed.

F i g. 1 shows that each of the corona generators mentioned has its own, electrical from the others independent energy supply is provided. Any power supply to the corona generators is Electrically isolated from the others on the high-voltage side and from ground. Are on the low voltage side the power supplies, however, via a resistor arrangement connected to ground, which will be described in more detail below. These energy supplies, the DC voltages or variable voltages to the discharge electrodes of the other devices Supply AC voltages with variable DC voltage superimposition are all shown here schematically, since such supply circuits are known in detail to the person skilled in the art. It goes without saying that different components of the power supply shown as a whole or individually for several Corona generators can be used together, as long as it is only possible to use the draining mass Measure the currents of each individual corona generator individually. For example, common Transformers with separate secondary windings are used to provide electrical input power to create the individual service allocations.

It is also understood that, although individually shielded corona generators are drawn, for individual ones Cases several corona generators can have a common shield. It is also known that with the term corona generator both those with multiple wires or needle assemblies as well those with single wires are meant.

It should also be especially pointed out that any conductive shielding of the corona generators is electrically isolated from the others as well as from the image carrier surface i2 and from ground. About that in addition, each corona generator shield has its own feedback loop only with its respective one individual energy supply connected. In this way the current feedback loop is each of these shields electrically isolated both from the image carrier surface and from ground the current of the shield directly back to the power source of the corona generator.

As already mentioned above, this shielding current is a variable part of the input current of the discharge electrode of the corona generator and does not flow from the discharge electrode to the image carrier surface, but rather for shielding. The return of this shielding current is in contrast to the conventional one electrophotographic devices in which the shields of the corona generators are generally electrical are led to ground Here the corona currents to the ground side, i.e. H. to the low voltage side their own energy supply or their energy source fed back, d. H. the shields are on Low potential. The ground ropes, the power supplies are located here, for technical reasons, slightly above the ground potential, since they are connected to ground via a measuring resistor circuit. This resistor circuit creates a small one Voltage drop across the resistor that is directly proportional to the one flowing through the resistor Electricity is, & h. the current between power supply and ground. This ground path current is a measure of represents the actual output current of the corona generator flowing over the image carrier surface 12. Das is related to the fact that the entire charge current transferred from the corona generator to the image carrier surface can only flow back to the ground side of the power supply via the current measuring circuit, which is formed by this resistive ground path. It is important that the shielding current of each Corona generator does not flow back through this ground path.

ίο The image carrier surface 12 is, as is the case with electrophotographic Devices is common and as it is also desirable here, grounded by providing a grounded conductive Has support that is directly connected to the earthed machine frame. The image carrier surface 12 can consist of a known thin closed layer of photoconductive material on top of this electrically grounded carriers exist. In this way, all of the charges to be dissipated from the image carrier surface 12 are removed derived directly from the carrier to ground. This way all of the different corona generators will be generated currents flowing over the image carrier surface without the possibility of differentiation in this common, leading over the conductive support of the image carrier surface and the machine earth Ground path summarized. With the circuit described, however, the combined currents for the discrete measurements in the individual return paths to the respective energy supplies separated again. In contrast to the facilities with a conventional structure, where the electricity between an electrically "floating" image carrier drum and the earth can be measured in the present If all corona generators are in operation at the same time, and yet their individual effective currents can be measured separately.

Although the corona generator shields are not directly connected to ground, they are almost in contact Ground potential. Their potential can only be very slightly above ground, corresponding to the low voltage drop on the current measuring resistor in the grounding path of the power supply. This tension corresponds to that Charge current from the corona electrode to the image carrier surface multiplied by this measuring resistor value So there is no safety hazard for the operator if he touches the shield Likewise, there is no increased risk of arcing from the shields to the Image carrier area and also no significant increase in the toner attraction by the shields. It understands however, that in individual cases, this should be expedient, the shielding on a clearer above ground potential can be brought, which is advisable for some purposes, such as e.g. to control the corona generator output current.

There is now a special control circuit for a corona generator, namely that of the supercharging corona generator 14 described. The drawing shows that the corona emitting electrode 52 is directly connected to an electrical Lead wire connected to the high voltage side of the DC variable voltage power supply 54 The low voltage side of the power supply 54 is only via a resistor series connection from resistors 56 and 58 to ground. These two resistors have a low resistance value They create a small but measurable voltage drop when the charge current flowing from the Corona generator flows to the image carrier surface, there

flows through. The shield 60 of the corona generator 14 is directly connected to the low-voltage side via a line 62 connected to the power supply 54 and thus separated from ground via the resistors 56 and 58.

This return line 62 for the entire current of the shield forms a first current loop. Only this current of the shielding finds a direct return to the energy supply 54 through the line 62. The effective charge current of the corona generator 14 from the corona electrode 52 to the image carrier surface 12 flows in a second current loop via the grounded carrier of the image carrier surface and the resistors 56 and 58 from the high-voltage side of the power supply 54 back to its low-voltage side. No current loop of any other corona generator is closed via the same current loop. It is thus possible in this way to measure the effective effective output current of the corona generator i4 at a reference terminal A at the resistor 58 without being influenced by the shielding current and independently of the other corona generators. This resistor 58 is adjustable so that a certain initial calibration and / or scale calibration can be carried out.

Since the corona generator 14 here with a control grid is provided, which does not apply to the other corona generators, he has an additional line 64, over which is given a potential from the power supply 54 to the control grid. Create the grid wires yourself however, no corona, so the current in line 64 can only be that which the grid is from the electrode 52 generating the corona discharge. Line 64 carries the entire grid current back to the power supply 54 in a separate current loop that takes the return path the resistor 58 does not affect.

With the circuit described, the desired independent and precise measurement of the effectively effective corona current of the corona generator 14 can be achieved. However, as can be seen from the illustration, a further resistor 56 and an additional return line 65 are provided. This feedback line 65 is connected at one end to a variable tap on the resistor 56 and at the other end to the power supply 54 via a very common control amplifier. This additional circuit arrangement represents a feedback circuit for automatic regulation or preselected control of the power output of the energy supply 54. This control circuit only reacts to changes in the effective corona current of the corona generator 14, while changes in the shielding current have no influence, since the resistors 56 and 58, which supply the control voltage for the control amplifier, only the effective corona current to be controlled flows through. It should also be noted that the adjustable separate control resistor 56 is not absolutely necessary, and the feedback line 65 could also be connected to point A , so that there would only be a dependence on the voltage at resistor 58. However, the additional resistor 56, which is variable by tapping, provides a separate sensitivity setting and / or a preset output level control can be created. It will be understood that both return line 65 and resistor 56 can be totally accidental if only conventional control of the

Energy supply 54 is desired in manual mode. In this case, the end of the resistor 58 with the reference point A which is at a higher potential is connected directly to the low-voltage side of the energy supply 54.

The other independent energy supplies with the measuring devices for their output currents and their control circuits are, as can be seen from the drawing, basically the same, so that the description of the corona generator 14 can essentially be transferred to them. Their current measurement connections are labeled B, C, D, E and F. With "B" there is no corona current measurement. As already stated, the other corona generators do not have control grids and therefore do not have any return lines like the return line 64.

The AC corona generators are the pre-transfer corona generator 24, the peel corona generator 34, and the pre-cleaning corona generator 4b. These include output connections C, E and F. They are connected to the associated AC voltage power supplies via electrically shielded cables so that the cables do not emit any high-voltage stray fields. The conductive shields, like the corona generator shields, are connected to the low-voltage side of the power supplies via return lines. They can easily be conductively connected to the corona generator shields. The AC leakage current of the lines is then returned directly to the low-voltage side, the line shields and the corona shields being electrically isolated from ground, as is also the case with the shielding return line 62 of the corona generator 14 described, so that the current loop for these currents is separated from the path of the effective corona charge current to be measured.

05 Be nOCn ucincriCt, uäu Clic WcCnSciSpännürigS-Kü-

corona generators can be of the type in which there is a dielectric shield between the corona generating Electrode and the conductive part of the corona generator shield is provided as indicated is known. Furthermore, the AC voltage corona generator can be constructed so that the corona shield is exclusively dielectric, so that no corona shielding current can flow, so that too no current feedback loop is required for energy supply. In that case there is only a current return path for the conductive shielding of the line between the power supply and the corona generator.

In summary it can be said that all AC high voltage line losses caught individually by shields and directly to the respective energy supplies of the individual AC corona generators are returned. On the other hand, alternating current would come from the energy supply lines can reach the ground connection of the device, it would be the low-voltage side of the power supply via the current measuring loop (i.e. the resistance path between the low voltage side of the power supply and ground). This would falsify the measured effective output current of the AC voltage corona generator result.

Next, the development station 20 will be considered along with the circuitry by which the developer rollers 22 a DC voltage potential is supplied. The drawing shows that a current

11 12

The measuring device is provided at an output terminal B via the copy sheet directly onto the guide rows, which is the same as the circuit arrangement which elements 30 and the suction shoe 42 are output when they come into direct electrical contact with the corona generators. The chip was. It goes without saying that for the development at the shield 33 it remains essentially desirable or necessary for the biasing device to remain constant and almost at ground potential. As can be the case, a return line corresponding to the shielding 60 of the corona generator 14 is to be provided for all devices 62 for returning any shielding components 30, 33 and 42 to a slightly above current, which in the present case is not ground potential Potential, where the span is set. The circuit shown, however, can result from the size of the voltage difference resulting from the Ko point B, a voltage that speaks to the current ent- io ronagenerator passing over to the image carrier surface, which from the developer rollers 22 to the image current multiplied by the resistance im Measurement path support surface 12 passes if it is assumed that between all these components and mass. These leakage currents via other paths to these rollers are not resistance value due to resistances are correspondingly substantial. This arrangement makes it clear that the resistors 56 and 58 formed and can be smaller, although the main function of the circuit 15 described, than 10,000 ohms, ie many times smaller than that, an accurate measurement of the effective Koronagenera- impedance of the corona generator 32 itself In order to be able to carry out the Imtor output currents, there is also a dépedance between the corona generator electrode (.nd right parts of the device, via which the currents to the image carrier surface or the image carrier surface It is an important advantage that all these components can be practically and also held in the entire measuring switching device at a potential that will be described below.
Another source of a current that is applied to the image carriers. Parts 30 and 42 are only used here as examples

gerfläche transitions, a voltage-connected transferring various common input and output device roller system be, as it is from the US-PS gen, which handle the copy sheet, lead or turn-38 60,436, for example, is known and desirably 25 as used in a broadcast station be selective which will be at potential transmission. All other conductive elements associated with the roller to connect to the same current measuring circuit, copy sheet come into contact while part of the around the current to the sheet passing over to the image carrier surface is in the area of action of the transfer comess. ronagenerators are preferably located in the

The voltage supply can be connected to the return line 35 by measuring the same type, see above Current between ground and power supply because they control the power output of the Energiedes lower voltage level can be better controlled. as if the current at a high potential does not affect gate, d. H. help make this only would be measured (e.g. at the output of the energy depending on the directly via the image carrier supply) or between the image carrier surface and the surface 12 effectively effective current er-mass, follows.

The next step is the transmission corona generator. In the introductory part of the description,

32 i.inc! its associated power supply 36 says that a problem which the described structure with the associated measuring circuit are considered, where and the electrical connections are intended to remedy, which in FIG. 1 shows that the power supply is the fact that in the seconds Korcna transfer measurement circuitry is practically the same as that described in connection with the transfer system, the charging corona generator 14 applied to the copy sheet. There is, however, an essential difference between conditions and certain copy sheet material, usually the pre-transfer area and the post-transfer charge, to a considerable extent along the co-transfer area in this electrographic pie sheet, e.g. B. through the paper, so to speak in the advises against the conditions in other electrical paper path are passed. That is, copy sheets with graphic equipment. All conductive machine parts that have a relatively low resistance value can normally come into contact with the copy sheet during the time in which the sheet is in the transfer corona generator when the sheet is in the transfer. which are isolated in contact with the copy sheet and directly connected to the shield 33 of the transmission, while the sheet is connected through the transmission corona generator. Special is to nagenerator being charged; These parts are about the recognizable that the two sheet guides 30 and the sheet guides 30 and the suction shoe 42. This special suction shoe 42 is only directly electrically connected here to the grounding paths for the output La shield 33, so that their entire The use of the transmission corona generator reduces leakage currents via the same return line 35, the effect of the Lazur low-voltage side of the transmission energy carriers discharged onto the copy sheet, since part of the charge is diverted from the actual supply 36. However, you can also use one. Transmission area C flows sideways This has particular return line. The feedback can lead to the fact that the transmission efficiency line 35 is lower than the return line 62 in the case of the corona 60, which is expressed in "hollow" letters generator 14 equivalent, ie it carries the current that can by the maximum effective transmission field, shielding 33 to the energy supply 36 in a separate current loop which is generated with the same charge supplied and which is different from that of the ringer. This also differentiates the accuracy of the measuring circuit with the output at point D. Transmission D determined current value the total amount of charge of the transmission transferred to the copy-corona generator on the shield 33 sheet. Rather, it also includes the leakage currents, the corona generator 32 does not give an exact measure

13 14

is because the through the side through the copy sheet, to have a low surface resistance. if

On the low-voltage side of the energy supply, the output of the transmission corona generator is reduced The current generated by the charges increases sharply (in the attempt to produce a desired

stood and the control resistance path flows and so upright as the value of the maximum transmission field strength

not to get effective current component at the terminal D in the 5), conducts the lateral charge conductivity of the

Measurement with incoming sheet these charges along the sheet in the fore

In the case of the transfer device according to the transfer area in which the sheet is not yet an exemplary embodiment of the invention, however, all machines are on the image carrier surface d. L the clay parts to be transmitted are isolated from the ground in order to have such a distancer image. This can prevent undesired currents. All of these leakage currents will occur via an air gap (a so-called toner jump, bypassing the control and measuring resistors), which leads to fuzzy, washed-out return line 35 directly to the formation of low voltage. This possibility of undesirable vernungsseite the power supply fed back, so as frühter transmission thus sets a limit for in they would flows from the shield 33. The current extent to which the output current of the transmission measurement on the Punkt_ D thus detected only the part of the laser 15 corona generator 32 can be increased in order to compensate for a dung output of the transfer corona generator 32, a drop in the peak value of the transfer field strength in which reaches the copy sheet 26 or 26a and via the consequent lateral discharge. With the rear image carrier surface flowing for the transfer effective management control device in the illustrated embodiment and compensated by readjusting the charge, the transfer output current can be kept constant by the transfer corona generator output by 20, or it is possible to increase only components 30 and 42 caused power losses. to allow within specified limits or with

The control circuit 37 thus corresponds to that of the coefficient as a function of a predetermined rate of increase

rona generator 14. This control circuit 37 scans the potential in the transmission range,

at least z. T. a compensation for the loss of the next, a switching device will be described,

Charge through the lateral discharge as a result of the lateral 25 the in the Fi g. 2 is shown and selected with the

conductivity of the copy sheet. between the measuring connections A to Fin F i g. 1 shell

Apart from increasing the charge release, it is possible to individually determine the effective corona

To compensate for this leakage, measure the generator current at the output. It belongs to this switching

of the transmission corona flow, the transmission device is a packet switching system that switches in three levels.

Corona flow essentially constant, which would be more than 100 with the usual shaft rotation of the individual

worth seeing is a constant transmission field contact arms of each packet layer The three layers

to maintain strength. are designated here by 101, 102 and 103, their associated

It is known per se. Rollers or other parts that contact arms with 105, 106 and 107. The inputs come into contact with the copy, to prevent switch 100 are the lines that are connected to measuring points A to F with the individual transfer of a charge to ground , as well as Einänisolieren. It is also known that the shielding from other elements that need to be measured should be used. The output is the line 200 from the contact arm 106 copy sheet to be coated with a dielectric layer to the measuring circuit 202. The switch 100 and the measuring units. The coated metallic parts are then circuit 202 are constructed in such a way that they are usually grounded separately, but can also have any given bias voltage on one of the alternating current and direct current components. On the other hand, it is possible to measure the corona generator current, where the charge output of a corona generator from an instantaneous value is recorded and stored depending on fluctuations in the resistance value, this is held and then the measurement of the area to be charged can be changed. An er · can be carried out.

protection path for the shielding of a development card 45 The circuit according to FIG. 1 allows each individual

ronagenerators be provided, which is partly via ne current between the corona generators and the

a photoconductive recording element is guided, image bearing surface, d. H. so the real charge current output

in order to measure the potential of the shielding depending on the gang, individually at the respective measuring connections.

Changes in resistance in the recording element can be measured, even if there are still several corona-

change and thus the total corona flow itself 50 generators are in operation. The outcome of every single one

Subject to change. Corona generator can be measured while the

The described control of the output of the over-copier works normally These current measurements Carrying corona generator 32 or other corona can be made for every moment, generators may be desirable in individual cases by taking the instantaneous value and adding it to a if such a corona generator is stored in voltage memory, as it is in the circuit 202 This is true if dynamic current is provided or with the help of an oscilloscope beam output of the corona generator increases with decrease and the like. This instantaneous current measurement is sore potential of the area to which the charge is delivered worth seeing for examinations in which the discharge is. In the case of the transfer corona generator 32, movement of various copy sheets is performed is this potential influencing the output that the charge 60 should be observed in the transmission range, dung on the layering of paper, toner, air and or where the effect on the output values of the Image carrier area within the transmission area. Corona generators are to be determined, the Än-This potential is brought about by the above-described changes in the image to be developed borrowed discharge of the charge through the copy paper or the like.

the transmission range reduces the lateral deflection 65 A pre-settable, fixed reference voltage source

transmission of transfer charges is quite considerable, it can be in the individual power supplies or on a

for papers that are installed in a relatively humid environment with a common reference point. For

exercise or which have already taken measurements for the purpose of regulating the energy supply

a comparison can be made between this reference voltage and the current-dependent voltage at the points AF , but not against ground.

With the switching device shown in Figure 2 the measuring circuit 202 can be used jointly for all measuring points, so that it is not necessary to provide a separate measuring circuit for each corona generator. The switch 100 ensures that the Current measuring circuit 202 provided for all measuring points can be connected to the measuring current path of each individual energy supply. Furthermore, precautions have been taken to be able to measure the direct current and alternating current components separately. this is achieved in the present case in that an inductive filter 300 and a capacitive filter 302 and a circuit arrangement is provided which switches back and forth between them, depending on the desired measurement of the direct current or alternating current component. This switching arrangement is in the present

3 ΪΤ_Ι1 _; _ r »__ t_ Ij MJC * _l_ - 1 * 4ΛΛ. I _-TI

gciiucii rau cui Drauuniicu un ocimiicis iw uiiu wiiu brought about with the help of the package layers 102,103 and the switching arms 106, 107 and the associated connections

It is now the switching arrangement shown as an example with a common measuring circuit of FIG. 2 are considered in detail, the output current measuring resistances of the individual power supplies (corresponding to the resistor 58 of the corona generator 14) are all preset to a suitable value for the measurement purpose. To measure the output of each corona generator, the switch 100 is rotated only in a position in which the desired corona generator is selected The switch 100 is shown here in a position in which the OFF ⁰ Sn ** C of Koroü3 ^a ensrators 24 voni pre-overexcitation range is selected. In the package layer 101, the contact finger 105 is both connected to the same output terminal C in two different switch positions. In both switch bars, the voltage present at point C is passed on via capacitor 302 and inductive choke 300, which are parallel to one another common high-impedance "audio" choke for choke 300 can be cited. The AC voltage components of the voltage at terminal Can are passed on to the outer contact ring 109 of the package layer 102 via the capacitor 302. The direct voltage component of the connection point C goes through the choke 300 to the inner contact ring 110 of the packet layer 102. The contact finger 106 is alternately in the switch positions in connection with the contact ring 109 or the contact ring UO. In the position shown in solid lines, the contact finger 106 is in connection with the inner contact ring HO. This means that the output line 200 of the switch 100 is only supplied with the direct current component of the input signal flowing in via the throttle 300.In the next following position, which is indicated by dashed lines, the contact finger conducts the alternating current component of the input signal from the terminal C via the capacitor 302 to the output line 200.

The third package layer 103 connects the component to ground via its contact finger 107 here, which is currently not being measured via the output line 200. The contact finger 107 is connected to ground, while the inner contact ring is connected to the outer contact ring 109 of the second package layer 102 and the outer contact ring with the inner contact ring 110 of the second packet layer 102 are connected. The solid drawn contact finger position means that the alternating current component over the Capacitor 302 and contact finger 107 is connected to ground, while the direct voltage component

ίο is measured. The reverse occurs with the next switch position.

It goes without saying that a division of the measurement into direct current and alternating current components is not desired in all cases. wisely bypassed with the help of a two-pole two-position switch that is assigned to the two filters will.

The measuring circuit 202 represents a somewhat more complicated measuring device, through which with the help of opera- tion amplifiers 204 and 206 a signal separation, as well as an AügcTibücks-V / ert detection and storage together with an optionally actuatable Switch 205 and a storage capacitor 208 is achieved. The switch 205 is shown as a relay which can be closed from a switching signal input at 210 either manually or on the basis of a signal from the device control to the instantaneous Input voltage on input line 200 at any desired time to capacitor 208, where the value is stored at a level that is present at the moment the switch 205 is opened. This tension can then become arbitrary Time can be evaluated and measured on an ordinary voltmeter 212, since the second operational amplifier 206 is separated from the input line 200. Of course, the output voltage measurement can be analog or digital, depending on what a control function is to be derived from it. When using logical impulses within the existing device controls that determine Corresponding to operating points or operating conditions, for brief impulses for the switching relay 205 at relay input 210, points in time of the machine cycle cycle can be selected very precisely and compared before different machine cycles are employed between the same sequence cycle points. As an an example it should be noted that the DC component of the output current of the corona generator 24 in the pre-transfer area will readily do at the moment

so when the leading edge of the developed image passes through this area, the switching relay 205 dependent on one? Machine control signal that feeds the copy sheet into the transfer station indicates is provided with a pulse.

Usually, adjustable time delay means can be used to track the actual time to delay the actuation of the switch 205 if a pulse from the machine control is not available at the exact desired measurement instant.

The operational amplifiers 204 and 206 can be formed by simple, commercially available dual operational amplifiers in an integrated circuit.

The illustrated selection and storage circuit in the measuring circuit 202 is for DC voltage values be it's correct. Will the measurement of AC compo Nenten required, then the values on the switch output line 200 can be measured directly with an AC voltmeter. The Opera-

17th

tion amplifier 204 can also be connected in such a way that that the AC voltage signals are rectified. An ordinary rectifier bridge can also be used to convert the alternating current value into a direct current value, or ac- tive filter circuits can be used.

Since the resistors 58 connected to the fixed ground connection have a low impedance value and they are all in parallel with the current measuring circuit shown, the output currents of the coro- regenerators by switching on the impedance of the Measuring circuit 202 is not influenced. These resistors in the ground path can be the normal variable resistors which are already contained in the power supply itself, so that the measuring circuit is then an integral Is part of the energy supply

With the circuit described, the shielding currents, the actually used currents themselves or the leakage currents can be measured or controlled individually or in any combination, since they can be recorded in separate or combined stripes, so that measured variables and control signals can be derived from them. The control circuit, which is formed, for example, from feedback resistor 56 and feedback path 65, can automatically keep the corona generator output current actually used constant. In this way, every corona generator can be made really insensitive to voltage at will. The amount of initial corona charge will then not fluctuate, even if there are changes in the charge on the image carrier surface. However, in some cases it is not at all desirable to keep this output constant, ie it is sometimes desired to have a dependence on changes in potential on the image carrier surface * u. For the charging corona generator 14, therefore, another shield current feedback line 62a is shown in phantom, which leads to a point between the resistors 56 and 58. During the measurement, the output terminal A still only detects the corona generator current through the measuring resistor 58, but the control line 65 now detects the sum of the output current actually used and the shielding current, because both currents now flow back to the power supply via the control resistor 56. The energy supply 54 is now controlled in such a way that the sum of the shielding current and the useful current is kept constant and not just the useful current alone.

For this purpose 2 sheets of drawings

60

65

Claims (9)

Patent claims: 1. Electrostatic copier having a recording surface on an electrically conductive, grounded Carrier, several corona discharge devices, the discharge electrodes of which from one Electrically conductive shield are surrounded and a corona ion flow on the recording surface output, furthermore with separate energy sources, which are connected to the discharge electrodes and supply certain input currents to each of the corona discharge devices, one variable Share of the corona ion flow generated by each discharge device for its shielding flows and flows off as a variable partial flow of the input flow, characterized in that that any energy source to control the effectively used corona current is low voltage via its own control circuit (56, 65) and one of these downstream »optionally as a setting resistor formed measuring resistor (58) is connected to ground or earth that the shields of the corona discharge devices against each other with respect to the grounded carrier of the recording material and are arranged isolated from ground, that each shield has its own Current feedback circuit (62,62a, 35 etc.) connected is the variable partial current of the input current flowing through the shielding the low voltage side of the associated energy source (54) into the input circuit of the corona discharge device -returned and at least through the measuring resistor {58) of mass or earth is separated, and that the sense of measurement (58), or that of the between the discharge electrode and the recording surface lying discharge path, the respective energy source and the control circuit (56,65) existing series connection, any corona discharge device to be selected at will, by means of a switching device (100) having a switch (101, 105), a voltage measuring circuit (202) for the determination of the corona flow effectively grooved to act on the recording surface can be switched in parallel 2. Copier according to claim 1, characterized in that the switching device (100) has a Switches (102,106,109,110) for two separately switchable Measuring circuits (300,302) for splitting the measuring current into a direct current and an alternating current component having. 3. Copier according to claim 2, characterized in that for splitting the measuring current into the Both components have a DC filter in one and an AC filter in the other Measuring circuit is arranged. 4. Copier according to claim 2 or 3, characterized in that the switching device (100) has a Earthing switch (103, 107) for earthing the respective unselected measuring circuit (300 or 302) having. 5. Copier according to claims 2, 3 or 4, characterized in that the switches of the switching device (100) are positively coupled to one another. 6. Electrostatic copier with at least one attachable to a controllable bias voltage source Development electrode, characterized by the features according to one of Claims 1 to 5 and characterized in that the development electrode or electrodes (22) like the Corona discharge devices have their own energy source and a control device for the bias voltage have, and can be connected to the voltage measuring circuit (202) via the switching device (100) are. 7. Copier according to one of claims 1 to 6, ι ο characterized in that the control circuit is off a variable resistor (56), which is connected to the low-voltage side the energy source (54) and by means of an adjustable tap with the Energy source is connected via a feedback line (65) 8. Copier according to one of claims 1 to 7, characterized in that the energy supply line of corona discharge devices to be operated with alternating current an electrically conductive, have isolated shielding from ground or earth, which is connected to the respective current feedback circuit the shielding of the corona discharge device is connected 9. Electrostatic copier with a transfer station with at least one corona discharge device arranged in the transfer station and electrically conductive guide devices for an image receiving material, characterized by the features according to one of claims 1 to 8 and characterized in that the guide devices (30, 44) with respect to ground or Earth is arranged insulated and are connected to the current feedback circuit (35) of the corona discharge device or corona discharge devices.