EP1156380B1 - Electrophotographic process control and diagnostic system - Google Patents

Description

The present invention relates to electrophotographic marking machines, and more particularly to inspecting subsystems of the electrophotographic process and providing adjustment operations for particular subsystems in relation to predetermined parameters.

The electrophotographic marking process is relatively complicated and involves a variety of subsystems, each of which must function properly. However, because these subsystems are interconnected, it is often difficult to diagnose and isolate the function of a particular subsystem. This is especially true for electrophotographic imaging and image development processes, since an examination of room lighting with the naked eye is mostly impossible.

Therefore, there is a need for analysis and diagnostic testing of an electrophotographic process in which certain subsystems can be compared with satisfactory operating parameters and appropriate remedial action taken. The object of the present invention is therefore to provide an analysis and diagnostic test method, with which certain subsystems can be compared with satisfactory operating parameters and appropriate remedial measures can be taken.

From the prior art are known:

The document US5012279 discloses a primary test for an electrophotographic tag, wherein the subsystems are tested without a reference standard bias in a test mode. US5862433 discloses the concept of film reference voltage, however subsystems are tested and adjusted by densitometric means during normal operation and during auto-setup. The document US5897238 discloses a functional test and for the primary charge device and the corresponding adjustment of the distance of the charge device to the photoconductor.

This is achieved according to the invention by a method having the features of claim 1 and a device having the features of claim 4. Further features emerge from the subclaims.

The present invention provides selective control of an electrophotographic marking apparatus which enables functional testing of the subsystems. In a further embodiment, the invention provides automatic subsystem function testing and thus supplements subsystem specific diagnostic and verification programs.

The present invention provides a reference voltage on a photoconductive element such as e.g. a tape, wherein the tape is passed in non-printing operation past a predetermined subsystem, the resulting tension is measured and compared to predetermined acceptable limits. Then, a regeneration cycle is provided to allow the electrophotographic marking apparatus to be set to print.

The invention will be described below with reference to the drawings based on preferred embodiments.

Fig. 1

eine schematische Seitenansicht eines typischen elektrofotografischen Markierungsapparats, auf den die vorliegende Erfindung anwendbar ist.

Fig. 2

ein Blockdiagramm einer Logik- und Steuereinheit von Fig. 1.

Fig. 3

ein Flussdiagramm eines Teils der Vorgänge, die von der Logik- und Steuereinheit ausgeführt werden.

In the drawings show:

Fig. 1

a schematic side view of a typical electrophotographic marking apparatus to which the present invention is applicable.

Fig. 2

a block diagram of a logic and control unit of Fig. 1 ,

Fig. 3

a flowchart of a part of the operations that are performed by the logic and control unit.

In Fig. 1 An electrographic marking apparatus 10 is shown. The present invention will be described with reference to a particular electrographic marking apparatus 10 such as a copier or printer. It should be noted, however, that while the invention is suitable for use in such apparatus, it may also be used with other types of electrophotographic copiers and printers.

As electrophotographic marking machines of the type described herein are known, the present description is particularly directed to the elements which are part of or directly related to the present invention.

• V₀ = Haupt/Primärspannung (relativ zur Erdung) auf dem Fotoleiter, wie sie direkt nach der ersten Ladeeinrichtung gemessen wird. Sie wird manchmal auch als "Anfangsspannung" bezeichnet.
• V_0(m) = Mittelwert der einzelnen V₀ Werte.
• V_B = Elektrodenvorspannung der Entwicklereinheit.

To facilitate understanding, the following definitions are defined:

• V ₀ = main / primary voltage (relative to ground) on the photoconductor, as measured directly after the first charger. It is sometimes referred to as "initial tension".
• V _{0 (m)} = average of the individual V ₀ values.
• V _B = electrode bias of the developer unit.

In the in FIG. 1 As shown in Figure 6, a movable image bearing member, such as a photoconductive belt 18, is stretched about a plurality of rollers, one of which is driven by a motor to pass the belt past a series of processing stations of the printer. The image bearing member may also be configured as a drum. The logic and control unit (LCU) 24, which may include a digital computer, has a stored program for sequentially operating the various processing stations or subordinate systems of the apparatus 10.

A charging station sensitizes the belt 18 by applying a uniform electrostatic charge of predetermined primary voltage V ₀ to the surface of the belt. The power of the first charging station is regulated by a programmable controlled power supply 30, which in turn is controlled by the LCU 24 to adjust the primary voltage V _0, for example by controlling the electrical potential (V _Grid ) on a grid electrode 28b, which detects the movement of the charged ions , which is caused by the operation of the charging wires 28a, controls on the surface of the support member. In the present example, a negative electrical bias is applied to the grid electrodes 28b, eg between -350 and -750 volts; a desired bias voltage can be -500 volts.

At an exposure station, the projected light from a write head 34 modulates the electrical charge on the photoconductive belt 18 to form an electrostatic latent image a document to be copied or printed. The write head preferably comprises a series of light emitting diodes (LEDs) or other light source, such as a laser or other exposure source for exposing the photoconductive belt. The exposure is pixel by pixel with a regulated intensity in accordance with the signals from the LCU to the write head interface 32, the write head interface comprising a programmable controller. Alternatively, the exposure may be by optical projection of an image of a document onto the photoconductive element 18.

When an LED or other electro-optical exposure source is used, the image data to be recorded is provided by a data source 36 for generating electrical image signals, e.g. from a computer, a document scanner, a memory or a data network. Signals from the data source and / or LCU may also output control signals to a recorder network and so on.

The movement of the belt 18 in the direction of the arrow A passes the areas carrying the latent electrostatographic charge images past a developer station 38. The toner or developer unit has one or more (several different colors) magnetic brushes adjacent to but spaced from the belt.
Magnetic brush developer units are known from US 4,473,029 and 4,546,060 known.

The LCU 24 selectively actuates the developer unit in relation to the passing image areas carrying the latent images. The magnetic brush is selectively brought into contact with or at a small distance from the belt 18. The charged toner particles of the contacted magnetic brush are attracted to the latent image pattern as an image to develop the pattern. At the same time, the calibration marks used for process control are being developed.

As is known in the art, the conductive parts of the developer unit, such as conductive applicator cylinders, act as electrodes. The electrodes are connected to a variable supply of DC potential V _B , which is supplied by a programmable controller 40 is regulated. The details regarding the developer units are set forth by way of example, but are not essential to the invention.

In this example, the development corresponds to a DAD (Discharge Area Development) process in which negatively charged toner particles selectively develop into relatively discharged areas of the light guide. Other types of developer units are known and can be used as well.

A transfer unit 46, as it is also known, is provided in order to bring a receiving sheet S in registration with the image into contact with the light-guiding element. In this way, the image is transferred to a recording sheet, for example made of paper, or a plastic sheet. Alternatively, the image can first be transferred to an intermediate element and then to the recording sheet. In the embodiment of the FIG. 1 the transmission unit comprises a transmission corona charger 47.

The electrostatic transfer of the toner image is performed with a suitable voltage applied to the transfer charger 47 to generate a constant current, as described below. The back surface of the receiver sheet is positively charged by the transfer charger in this example while the receiver sheet contacts the toner image on the photoconductor member to draw the toner image onto the receiver sheet.

After transfer, the receiving sheet may be released from the belt 18 by means of a known non-stick corona charger (not shown). A cleaning brush 48 or knife is also provided downstream of the transfer unit to remove the toner from the belt 18 to allow reuse of the surface to form additional images. In order to facilitate removal of the toner remnants and other particles from the brush 48, a charger 43 is usually provided to neutralize positive charge on the light guide or the electrostatic adhesion of the remaining particles in this case to reduce the band 18. The voltage of the cleaning and treatment charger is controlled by a power supply 42. While separate power supplies are shown for each charger, multiple power supply power may be used instead of multiple power supplies.

After transferring the unfixed toner images onto a receiver sheet, the receiver sheet is conveyed to a fusing unit 49, where the image is fixed.

A densitometer 76 is disposed between the developer unit 38 and the transfer unit 46. The densitometer 76 monitors the development of the regions of the photoconductive belt 18 as known in the art.

A second sensor, which is also preferably provided for process control, is an electrostatic voltmeter 50. A voltage meter of the first loading station 28 is preferably arranged downstream located to provide readings of the measured V ₀ s or V _{0 (m)} s. The voltmeter is preferably fixed relative to the band 18, thus reducing alignment and adjustment problems associated with the transmittable voltmeter, particularly with respect to the band 18. The voltmeter (electrometer) 18 can sense both polarities of the voltage measure and is therefore needed to determine all voltage tests.

The output V _{0 (m)} s and densities determined by the densitometer 76 are applied to the LCU 24, which generates new setpoints for E ₀ , V ₀ , V ₀ and the toner replenishment operation in accordance with a process control program. In addition, the process controller may be used to adjust the transfer current strength generated by the transfer charger 46 by changing the programmable power supply 51. A preferred electrometer is in the US 5,956,544 described.

Apparatus 24 may be defined as a variety of subsystems, including, but not limited to, the general descriptions of a cargo system Exposure unit, a developer subsystem, a transfer subsystem, an aftertreatment subsystem, a fuser system, said subsystems comprising the previously described components such as the photoconductive member, the first charging station, the bias shift, the after-treatment charging station and the transfer rollers.

In addition, the LCU 24 provides overall control of the device and its various subordinate systems. The programming of commercially available microprocessors is familiar to the person skilled in the art. The following disclosure is intended to enable a programmer to write a suitable control program for such a microprocessor.

The logic operations described in this document, apart from microprocessors, may also be provided by or in cooperation with non-programmable (hardware) or programmable logic devices. To accurately control the timing of the various processing devices, encoders are commonly used in conjunction with indicators on the photoconductive element to promptly output signals indicative of the image frame areas and their position relative to the various units. Other types of timing control may also be used.

Fig. 2 Figure 12 shows a block diagram of a typical LCU 24. The typical LCU 24 includes a temporary data memory 152, the central processing unit 154, the process and task check module 155, the timing and cycle control unit 156, and the stored program control 158. The data input and output is sequential or under the supervision of program control.

Input data is fed either through the input signal buffer 160 into an input data processor 162 or through an interrupt signal processor 164. The input signals are derived from various switches, sensors, and analog-to-digital converters that are portions of the apparatus 10 or from external sources passed him. The output data and control signals are fed directly or through a latch 166 into appropriate output drivers 168. The output drivers are connected to the appropriate subordinate systems.

The LCU 24 is set up to perform a series of subsystem tests. In performing these checks, the LCU 24 provides for the normal printing operation of the apparatus 10. In addition, the LCU 24 is set to operate the apparatus in test mode, thereby performing the entire photoelectric process.

In the present test (non-printing) operation, the LCU 24 is generally set to generate a predetermined voltage on the belt 18 and subsequently select a particular subsystem, the subsystem generating a corresponding variation in belt tension. The LCU 24 causes rotation of the belt 18 to the voltmeter 50 where the resulting belt tension is measured. The measured voltage is compared by LCU 24 with a predetermined set of allowable values. In addition, the deviation is forwarded to the engineer in the field if the measured voltage is outside the predetermined frame.

The LCU 24 is further configured to isolate the unchecked subsystems to reduce the risk of damaging particular subsystems.

The LCU 24 also includes regeneration operations that correspond to each of the subsystem checks. The regeneration operations may return the apparatus 10 to normal printing operation. Optionally, the regeneration operations may prepare the apparatus 10 for testing additional subsystems. In Fig. 3 2, a flow chart of the process and task check program of the LCU 24 is shown.

More specifically, the LCU 24 measures a voltage of the first charging station and stores a resultant voltage on the photoconductive member as measured on the electrometer 50. The voltage of the photoconductor element is compared with the measured voltage to determine charge efficiency. As is known in the art, an increase in charge efficiency indicates increased contamination in the first charging station. Thus, the initial test / first test allows an engineer on site to check the functionality of the first charging station.

wobei $\left(\frac{V_{0\mathit{grid}}}{V_{0\mathit{film}}}\right)$

die anhand der bei der Prüfung der ersten Ladestation erhaltenen Werte bestimmte Ladungseffizienz ist. Die LCU sorgt somit dafür, dass jede Prüfung auf eine bekannte und bestimmte Referenzspannung standardisiert ist.Since the performance of some subsystems is measured by their effect on the photoconductor _voltage , it is desirable to _apply a film reference _voltage V _0ref to the photoconductor prior to testing the subsystems. The reference voltage is achieved by setting the grid voltage of the first charging station as follows: $V_{\mathit{grid}}=\left(\frac{V_{0\mathit{grid}}}{V_{0\mathit{Movie}}}\right)\cdot V_{0\mathit{ref}}.$

in which $\left(\frac{V_{0\mathit{grid}}}{V_{0\mathit{Movie}}}\right)$

is the charge efficiency obtained from the test of the first charging station. The LCU thus ensures that each test is standardized to a known and specific reference voltage.

The electrophotographic marking apparatus 10 is not in printing operation and the reference voltage V ₀ is transferred to the belt 18. A particular subassembly is then switched, which creates a tension on the photoconductive belt 18 or transfers it to the belt 18. The LCU 24 then rotates the belt 18 along its path so that the resulting tension on the belt is measured at the electrometer 50. That is, the LCU 24 causes the resulting voltage to be brought to the electrometer 50 instead of moving the electrometer to the resulting voltage.

The resulting voltage of the photoconductive element 18 is then compared to a predetermined series of acceptable voltages to establish criteria that decide the further course.

In addition, the deviation of the measured voltage from the particular subsystem is made available to the operator so that predictions can be made about his life.

1. A. Haupantriebsprüfung - Diese Prüfung überprüft Hauptzeitgebung, Übergangsstellendetektion und die Filmspur für den Markierungsapparat.
2. B. Automatische Set-Up Phase I- In der ersten Phase der automatischen Set-up Prüfung werden das Densitometer und das Fotoleitelement überprüft. Dann erfolgt eine Analyse des Verunreinigungsgrades.
3. C. Automatische Set-Up Phase II - In der zweiten Phase der automatischen Set-Up Prüfung werden das Laden und die Kalibrierung des Elektrometers sowie der Vorspannungsoffset überprüft.
4. D. Automatische Set-Up Phase III - In der dritten Phase der automatischen Set-Up Prüfung werden die Prozesssteuerung und die Sollwerte des Elektrofotografen überprüft.
5. E. Automatische Set-Up Phase IV - In der vierten Phase der automatischen Set-Up Prüfung werden der Belichtungsgrad und die Spannung des fotoleitenden Elements überprüft.
6. F. Erste Ladestation - Die erste Ladestation überprüft den Verunreinigungsgrad der ersten Ladestation und sorgt für eine Übereinstimmung mit den vorbestimmten Sollwerten.
7. G. Vor-Reinigungsladestation - Diese Prüfung überprüft den Film für das Reinigen nach der Übertragung und vor der Reinigung.
8. H. Nachbehandlungsladestation - Das Nachbehandlungsladestationsprogramm sorgt für die Prüfung der Nachbehandlungsladestation sowie für die Überprüfung deren Verschmutzungs- und Leistungsgrad.
9. I. Übertragungswalze - Die Übertragungswalzenprüfung überprüft die Übertragungsladestation und die Walzenpunkte.
10. J. Nach-Entwicklungslöschung -Das Nachentwicklungslöschungsprogramm überprüft die Löschungsspannung auf dem fotoleitfähigen Band.
11. K. Interne Trägerpartikelentfernungsvorrichtung - die interne Trägerpartikelentfernungsvorrichtung liefert bei der Prüfung keine dazugehörige Spannung, da bei dem Untersuchen von falschen Entladungen nicht solche Spannungen auftreten.
12. L. Externe Trägerpartikelentfernungsvorrichtung - die externe Trägerpartikelentfernungsvorrichtung liefert ebenfalls keine dazugehörige Spannung, da bei dem Untersuchen von falschen Entladungen nicht solche Spannungen auftreten

Thus, the LCU can perform the following checks:

1. A. Main Drive Test - This test checks the main timing, transition point detection, and the movie track for the marker.
2. B. Automatic Set-Up Phase I- In the first phase of the automatic set-up test, the densitometer and photoconductor are inspected. Then an analysis of the degree of contamination takes place.
3. C. Automatic Set-Up Phase II - In the second phase of the automatic set-up test, the charging and calibration of the electrometer and the bias offset are checked.
4. D. Automatic Set-Up Phase III - In the third phase of the automatic set-up test, the process control and setpoints of the electrophotographer are checked.
5. E. Automatic Set-Up Phase IV - In the fourth phase of the automatic set-up test, the exposure level and the voltage of the photoconductive element are checked.
6. F. First Charging Station - The first charging station checks the degree of contamination of the first charging station and ensures compliance with the predetermined reference values.
7. G. Pre-Clean Charge Station - This test checks the film for cleaning after transfer and before cleaning.
8. H. Post-Treatment Charging Station - The post-treatment charging station program will check the post-treatment charging station and check its degree of soiling and efficiency.
9. I. Transfer Roller - The transfer roller inspection checks the Transfer Loading Station and the roller points.
10. J. Post-Development Erase - The post-development erase program checks the erase voltage on the photoconductive belt.
11. K. Internal Carrier Particle Removal Device - The internal carrier particle removal device does not provide an associated voltage during the test, as such stresses do not occur in the investigation of false discharges.
12. L. External Carrier Particle Removal Device - The External Carrier Particle Removal Device also does not provide any associated stress because such stresses do not occur in examining false discharges

In one embodiment, all of the tests A to J are performed sequentially. Alternatively, the tests may be isolated from each other to optimize the diagnosis of the apparatus 10.

The subsystem checks GJ are evaluated by the electrometer 50, which is located at the end of the exposure process. The sequencing of the machine is selected to treat these charges for only one photoconductor rotation without the first charging station to prevent damage to the photoconductive properties of the photoconductor. This process is initiated by the timing of the LCU 24, which determines the check routines of the operation. In the preferred embodiment, tests G through J are preceded by test F to measure the current charge efficiency.

In addition, the subsystems can be activated and reactivated at certain locations on the photoconductor path. Furthermore, the electrometer measurements can be synchronized so that the collected data corresponds to the particular subsystem test.

Photoconductor revolutions to the normal electrophotographic conditions precede and follow the measurement revolution of the photoconductive element to form a regeneration cycle.

The LCU 24 is set to perform comprehensive self-checks of the subsystems involved in the generation of an output image. The task check program of the LCU 24 ensures that the subsystems necessary for imaging (such as the first loading station, the bias offset, and the exposure) are functional. In addition, the program checks used to determine whether the subsystems that do not directly contribute to imaging (such as post-treatment charging station, pre-cleaning charging station, post-development erasure, and carrier particle removal bias) are within normal operating tolerances or conditions.

The data obtained in each subsystem check is compared with the normal operating values and applicable error limits to determine a pass or fail status for each test. In this way, a service technician can quickly determine which subsystems are within acceptable limits and determine the relative lifetime of other subsystems.

The LCU 24 sets the electrophotographic marking apparatus 10 in a normal printing operation in which a user can use the apparatus for his job of producing electrophotographically produced copies or prints. Additionally poses the LCU 24 places the apparatus 10 in a non-printing mode which is selectively controlled by the LCU to enable subsystem analysis.

List of reference numbers

10

marking machine

18

photoconductive belt

24

Logic and Control Unit (LCU)

28

first charging station

28a

Aufladedrähte

28b

grid electrodes

30

power supply

32

interface

34

Stylus

36

Data Source

38

developer unit

40

programmable controller

42

power supply

43

loader

46

transmission unit

47

corona charger

48

brush

49

Einschmelzeinheit

50

sensor

51

power supply

76

densitometer

152

temporary data store

154

central processing unit

155

Process and process module

156

Timing and cycle control unit

158

stored program control

160

Input signal buffers

162

Input data processor

164

Interrupt signal processor

166

latch

168

output driver

S

bow

Claims (5)

1. A method of operating an electrophotographic marking machine (10) having a plurality of subsystems (24, 28, 30, 34, 38, 40, 42, 43, 46, 47, 48, 49, 50, 51, 76), the method comprising the steps of:

   a) disposing the marking machine in a test mode;

   b) operating a first charger (28) of the marking machine (10) to establish a first electrostatic charge on a photoconductor (18) of the marking machine (10);

   c) measuring voltage of the first electrostatic charge on the photoconductor (18) and determining a measured charge value (V_0film) for the first electrostatic charge; characterized in that:

   d) a grid electrode (28b), associated with the primary charger, is operated at a known grid voltage (V_0grid) to establish the first electrostatic charge in step b);

   e) establishing a further electrostatic charge on the photoconductor (18) that comprises a reference voltage (V_0ref) that is established by adjusting a grid voltage (V_grid) of the grid electrode (28b) in accordance with charging efficiency of the first charger (28), wherein charging efficiency is a function of the ratio of the known grid voltage (V_0grid) of the grid electrode (28b) in step d) to the measured charge value (V_0film) of the first electrostatic charge on the photoconductor (18) as determined in step c);

   f) with the primary electrostatic charge on said photoconductor established to said reference voltage (V_0ref), actuating in said test mode one of the subsystems (34,43,47, 48) for imparting a resulting voltage on the photoconductor (18);

   g) measuring the resulting voltage on the photoconductor; and

   h) comparing the resulting voltage to a predetermined range of acceptable voltages for said one subsystem.
2. The method of one of the preceding claims, wherein in steps c) and g) the respective voltages are measured by moving the photoconductor (18) to a stationary sensor (50) and using the sensor (50) to measure the respective voltages.
3. The method of one of the preceding claims, further comprising the step of isolating subsystems (34, 43, 47, 48) not being tested.
4. An electrophotographic marking machine (10) having a plurality of subsystems (24, 28, 30, 34, 38, 40, 42, 43, 46, 47, 48, 49, 50, 51, 76), the marking machine comprising:

   a logic and control unit (24) configured to dispose the marking machine in a test mode;

   a photoconductor (18) that is movable along a path past at least some of said subsystems (28, 34, 38, 43, 46, 47,48, 50, 76) ;

   a primary charger (28) for establishing a electrostatic charge upon the photoconductor (18) ; and

   a voltmeter (50) for sensing a electrostatic charge upon the photoconductor (18) which is coupled to the logic and control unit (24);

   the logic and control unit (24) being configured to determine a measured charge value for the electrostatic charge sensed by the voltmeter;

   characterized by,
   a grid electrode (28b) which is associated with the primary charger (28) and is connected to the logic and control unit (24), the logic and control unit (24) being configured to: control the grid electrode (28b) to operate at a known grid voltage of the grid electrode (28b) to establish a first primary electrostatic charge sensed by the voltmeter (50);
   control the grid electrode (28b) to establish a further electrostatic charge, having a reference voltage (V_0ref), on the photoconductor(18), wherein the reference voltage (V_0ref) is established by adjusting the grid voltage (V_grid) of the grid electrode (28b) in accordance with a charging efficiency of the primary charger (28), wherein charging efficiency is a function of the ratio of the known voltage (V_0grid) of the grid electrode to the measured charge value (V_0film) of the first electrostatic charge on the photoconductor (18);
   with the electrostatic charge having said reference voltage (V_0ref) on said photoconductor (18) being established selectively actuated in a test mode one of the subsystems (34, 43, 47, 48) for imparting a resulting voltage on the photoconductor (18);
   to move the photoconductor past the voltmeter (50) and to perform a voltage measurement of the resulting voltage by the voltmeter; and
   to compare the resulting voltage on the photoconductor to a predetermined range of acceptable voltages for said one subsystem (34, 43, 47, 48).
5. The electrophotographic marking engine (10) according to Claim 4 and wherein the logic and control unit (24) is further configured to isolate subsystems not being tested.

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