Patent Grant
7653331
The disclosure is directed to an image forming devices and, more particularly, to a method and an apparatus for correcting transfer and photoreceptor belt misalignment in an image forming device.
Apparatuses that form images on a sheet, such as electro-photographic reproduction machine and printers are equipped with mechanisms to rotate a continuous belt at various locations inside the apparatus. The continuous belts used in conjunction with such mechanisms include a photoreceptor belt and transfer belt. Flexible electrostatographic belt imaging members are well known in the art. Typical electrostatographic flexible belt imaging members include, for example, photoreceptors for electrophotographic imaging systems; electroreceptors or flexible ionographic imaging members for electrographic imaging systems; and flexible intermediate transfer belts for transferring toner images in electrophotographic and electrographic imaging systems.
To insure proper operation of the flexible electrostatographic belt imaging members it is important to limit shifts along the axes of rotation and lateral position as it rotates. Shifts in lateral position results in imaging degradation and damage, with repeated operations, to the belt itself. A source of shifting in lateral position can arise when the photoreceptor belt and transfer belt interact. This belt interaction creates a meandering force or contact force that leads to misalignment or shifting of the belt in a lateral position. The misalignment causes the edge portions of the respective belts to be damaged by the meandering belts. Another source is differences in speed of the belts, too much velocity variation or misalignment can cause belt ripple, image distortion, or abrasive degradation.
According to aspects of the embodiments, there is provided methods of optimizing contact forces between transfer and photoreceptor belts in image forming devices. The method acquires initial and operational set point data for the photoreceptor and transfer belt at different stages of engagement. Yaw motion is applied to reduce any misalignment between the belts based on the acquired data. A processor is used to determine misalignment between the photoreceptor belt and the transfer belt, and an actuator can be used to apply yaw motion. The yaw motion can return the transfer belt and the photoreceptor belt to their initial set position, or return a steering subsystem actuator to its setting prior to engagement of the belts. Set point data can be from the respective transfer steering subsystem for the photoreceptor and the transfer belts.
Aspects of the disclosed embodiments relate to methods for optimizing contact forces between transfer and photoreceptor belts, and corresponding apparatus to reduce misalignment between interacting belts and image forming device with controller to reduce misalignment between photoreceptor and transfer belts. The disclosed embodiments minimize misalignment that could cause belt ripple, image distortion or abrasive degradation. The disclosed embodiments provide a lateral adjustment (yaw motion) on the bias transfer module (BTB) module assembly so the speed of the interacting belts can be synchronized and misalignment reduced.
The disclosed embodiments include methods for optimizing contact forces between a transfer belt and a photoreceptor belt by applying yaw motion to the bias transfer module when misalignment is found to have occurred. The yaw motion acts to bring either the transfer belt or the photoreceptor belt to a position where misalignment is minimized.
The disclosed embodiments further include an apparatus having a back up roll and bias roll positioned to form a nip. A print media and portions of the transfer and the photoreceptor belts move through the formed nip. An aptly programmed processor \controller is provided to determine if misalignment exist between the transfer belt and the photoreceptor belt. If a misalignment is determined, an actuator is used to apply yaw motion to reduce the misalignment.
The disclosed embodiments further include an image forming device consisting of a plurality of rollers mounted to a frame, a photoreceptor belt, a transfer belt, and processors and controller for minimizing misalignment between the belts.
A printing process such as an electrophotographic process must charge the relevant photoreceptor surface. The initial charging may be performed by a charge source 16. The charged portions of the photoreceptor 12 may then be selectively discharged in a configuration corresponding to the desired image to be printed by a raster output scanner (ROS) 18. The ROS 18 may include a laser source (not shown) and a rotatable mirror (also not shown) acting together in a manner known in the art to discharge certain areas of the charged photoreceptor 12. It should be appreciated that other systems may be used for this purpose including, for example, an LED bar or a light lens system instead of the laser source. The laser source may be modulated in accordance with digital image data fed into it and the rotating mirror may cause the modulated beam from the laser source to move in a fast scan direction perpendicular to the process direction of the photoreceptor 12. The laser source may output a laser beam of sufficient power to charge or discharge the exposed surface on photoreceptor 12 in accordance with a specific machine design.
After selected areas of the photoreceptor 12 are discharged by the laser source, remaining charged areas may be developed by developer unit 20 causing a supply of dry toner to contact the surface of photoreceptor 12. The developed image may then be advanced by the motion of photoreceptor 12 to a transfer station including a transfer device 22, causing the toner adhering to the photoreceptor 12 to be electrically transferred to a print media or substrate, which is typically a sheet of paper, to form the image thereon. The sheet of paper with the toner image may then pass through a fuser 24, causing the toner to melt or fuse into the sheet of paper to create a permanent image.
As shown, a densitometer 26 may be used after the developing step to measure the optical density of the halftone density test patch created on the photoreceptor 12 in a manner known in the art. A tone reproduction curve (TRC) or tone reproduction table (TRT) can be used with the data from the densitometer to ascertain the quality of the print. As used herein, the densitometer is intended to apply to any device for determining the density of print material on a surface, such as a visible light densitometer, an infrared densitometer, an electrostatic voltmeter, or any other such device that makes a physical measurement from which the density of print material may be determined.
The sensors 210 can include one or more light source with one or more photodetector, strain gauge, or any other position-determining sensor that outputs position data in accordance with detected position-determining marks on a belt that can be detected by the position-determining sensor. A suitable light source could be one or more light emitting diode (LED). Regardless of the type of sensor used the signal from each individual sensor is a digital representation of the belt's current lateral position, with an accuracy defined by the sensor or the distance between two adjacent sensors when used in combination to determined position. Furthermore, position-determining marks with an encoder can generate a belt-conveying signal indicative of the belt movement in the conveying direction. Various sensors and methodologies can provide the controller with a real-time indication of the lateral position and the speed of each belt.
The motor 230 is inclusive of a driving mechanism that can comprise driving rollers that rotate and drive a belt, a driving motor that provides a driving force to a driving roller, and a driving motor controller that controls a driving motor to maintain the speed of the motor and to limit transient conditions.
The steering 240 is inclusive of a steering motor controller that can control the positioning of the belt based on data from sensors 220, belt controller 210, and storage device 250. Storage device 250 stores data including minimum weaving of a belt, initial belt position, initial set point data, position of the steering roller that corresponds to a position of a belt in real-time, and a snapshot of operational data that indicates the operation of the belt. This data is made available to all processing systems in image forming device 100.
The transfer belt 310 interacts with photoreceptor belt 320 and back up roll 330. As noted above in
The pressing of back up roll 330 against bias roll 350 causes a nip 380 to form between the photoreceptor belt 320 and the transfer belt 310. Engagement and disengagement of the respective nips is automated by at least one actuator, such as a cam and stepper motor mechanism, where the at least one actuator is controlled by controller 840. At the nip, the belts pressed against each other and upon contact, equal and opposite forces will act to disturb the belt steering regulation for each belt mechanism. The magnitude of each belt steering subsystem 200 response is expected to be different, but in opposite directions.
The presence of a greater than zero relative velocity component is inferred by the required belt steering control actions of the photoreceptor and transfer belt steering subsystems. Belt interaction and variations in the manufacturing of components have been known to give rise to a greater than zero relative velocity. Regardless of the cause, velocity differences between the photoreceptor belt and transfer belt could cause belt ripple, image distortion/degradation or abrasive action to occur. An appropriate measure of transfer belt abrasive action is given by the following equation:
ABRACT=NL*M*BC
Where NL is the length of the nip 380 formed between the rolls; M is the misalignment angle between the belts; and, BC is the number of belt cycles. So for an expected nip length of 4 mm (4×10−3), a misalignment angle of one degree (17.45×10−3 radians); and one mega cycles at the photoreceptor belt. A transfer belt slips with respect to the photoreceptor by 70 meters. Variations in the manufacturing process such as in the motor or gear mechanism can be handled by the individual belt steering subsystem. The greater than zero relative velocity due to belt interaction can be managed by minimizing the misalignment of the belts.
Applying lateral motion to either belt is one way for correcting misalignment between the photoreceptor belt 320 and the transfer belt. Yaw motion as used herein includes lateral motion and controlling the respective belt steering mechanism. Yaw motion could be used to return the belts to their set points prior to engagement. In the alternative or in combination with returning the belts to their set points prior to engagement, the yaw motion could return each belt steering subsystem actuator to its setting prior to engagement. As shown in
Yaw steering mechanism 402 is any rod or actuator that can apply a lateral force to the transfer or photoreceptor belt so as to minimize misalignment. Yaw steering mechanism 402 can be a respective belt steering subsystem 200 or actuators in the respective belts.
In particular, graphical representation 500 shows an X-Y axis of photoreceptor belt steering actuator set point 510 and transfer belt steering actuator set point 520. Image forming device 100 is initially adjusted prior to contact between the transfer belt and photoreceptor belt. Points X1 and Y1 represent initial setpoint 530 for both subsystems. Upon contact, equal and opposite forces will act to disturb the belt steering regulation algorithm for the transfer and photoreceptor belts. The magnitudes of each subsystem responses are expected to be different, but in opposite directions. It is assumed that each belt steering algorithm has a sensor that provides position feedback at sufficient resolution. Points X2 and Y2 represent the operational set point 540 for both subsystems.
The difference between the set points represents the misalignment of the belts. The misalignment of the belts can be reduced by changing the set point of the belt steering subsystem. Points X3 and Y3 represent the corrected set point 550 for both subsystems. It should be noted, that the overall strategy of lowering misalignment between the belts can be accomplished by changing one or all the set points of the respective belt steering subsystem. Placing an actuator on the transfer belt module or the photoreceptor belt module would change the set point for that module. In
Misalignment between the belts can be viewed as a difference in belt velocity 580. Vector 560 represents the vector components for transfer belt velocity and photoreceptor belt velocity. Angle 570 is a measure of the misalignment between the belts. Angle 570 is the slip velocity between the belts.
In action 630, a misalignment is determined. As noted above with reference to
Photoreceptor belt input signal 710 is processed by first processor 730 to determine the deviation of the photoreceptor belt from an initial position. Transfer belt input signal 720 is processed by second processor 740 to determine the deviation of the transfer belt from an initial position. The deviation of the respective belts, as determined by the first processor 730 and second processor 740, is then processed by controller 750 so as to determine misalignment of the belts. The first processor 730, second processor 740, and controller 750 could be encased in a yaw control module 760. Controller 750 generates a lateral force signal 770 that when acted upon causes the actuator 780 to apply yaw motion to an attached belt module such as transfer belt 310 shown in
In the illustrated embodiment, the controller 840 may be implemented with a general-purpose processor. However, it will be appreciated by those skilled in the art that the controller 840 may be implemented using a single special purpose integrated circuit (e.g., ASIC, FPGA) having a main or central processor section for overall, system-level control, and separate sections dedicated to performing various different specific computations, functions and other processes under control of the central processor section. The controller 840 may be a plurality of separate dedicated or programmable integrated or other electronic circuits or devices (e.g., hardwired electronic or logic circuits such as discrete element circuits, or programmable logic devices such as PLDs, PLAs, PALs or the like). The controller 840 may be suitably programmed for use with a general purpose computer, e.g., a microprocessor, microcontroller or other processor device (CPU or MPU), either alone or in conjunction with one or more peripheral (e.g., integrated circuit) data and signal processing devices. In general, any device or assembly of devices on which a finite state machine capable of implementing the procedures described herein can be used as the controller 840. A distributed processing architecture can be used for maximum data/signal processing capability and speed.
Embodiments as disclosed herein may include computer-readable medium for carrying or having computer-executable instructions or data structures stored thereon. Such computer-readable medium can be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable medium can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code means in the form of computer-executable instructions or data structures. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or combination thereof) to a computer, the computer properly views the connection as a computer-readable medium. Thus, any such connection is properly termed a computer-readable medium. Combinations of the above should also be included within the scope of the computer-readable medium.
Computer-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. Computer-executable instructions also include program modules that are executed by computers in stand-alone or network environments. Generally, program modules include routines, programs, objects, components, and data structures, and the like that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of the program code means for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described therein. The instructions for carrying out the functionality of the disclosed embodiments may be stored on such a computer-readable medium.
The instructions from a computer-readable medium may be used by an electronic device, such as controllers 210, 750, 800, to cause the functionality of the embodiments to occur. These instructions may be loaded into a memory to be executed by a processor as needed.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5077795 | Rourke et al. | Dec 1991 | A |
| 5296904 | Jackson | Mar 1994 | A |
| 6088558 | Yamada et al. | Jul 2000 | A |
| 7242894 | Kuo et al. | Jul 2007 | B2 |
| 20040052555 | Berkes et al. | Mar 2004 | A1 |
| 20040146796 | Gross et al. | Jul 2004 | A1 |
| 20050095024 | Gross et al. | May 2005 | A1 |
| 20060034634 | Yu | Feb 2006 | A1 |
| 20060104678 | Kuo et al. | May 2006 | A1 |
| 20060245773 | Gross et al. | Nov 2006 | A1 |
| 20070183821 | Parks | Aug 2007 | A1 |
| 20080088691 | Fitzpatrick et al. | Apr 2008 | A1 |
| 20080089703 | Calamita | Apr 2008 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20090297221 A1 | Dec 2009 | US |
