Patent Application
20070292150
Aspects and features of the present embodiments will become apparent as the following description proceeds and upon reference to the drawings, in which:
For a general understanding of the present embodiments, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements.
Moving now to a description of
Initially, a segment of belt 14 passes through charging station 18. At charging station 18, a corona generating device (not shown) or other charging apparatus, charges photoreceptor belt 14 to a relatively high, substantially uniform potential. Once charged, the photoreceptor belt 14 is advanced to imaging station 20.
At imaging station 20, a raster output scanner (ROS) (not shown) discharges selectively those portions of the charge corresponding to the image portions of the document to be reproduced. In this way, an electrostatic latent image is recorded on the photoconductive surface. An electronic subsystem (ESS) (not shown) controls the ROS. The ESS is adapted to receive signals from a system controller 24 and transpose these signals into suitable signals for controlling the ROS so as to record an electrostatic latent image corresponding to the document to be reproduced by the printing machine 10. Other types of imaging systems may also be used employing, for example, a pivoting or shiftable LED write bar or projection LCD (liquid crystal display) or other electro-optic display as the “write” source.
After the electrostatic latent image is recorded on photoconductive surface of belt 14, belt 14 advances to development station 28 where toner material is deposited onto the electrostatic latent image. In the development station 28, toner particles are mixed with carrier beads, generating an electrostatic charge therebetween which causes the toner particles to cling to the carrier beads to form developing material. The developing material is brought into contact with the photoreceptor belt 14 such that the latent image thereon attracts the toner particles from the developing material to develop the latent image into a visible image.
After the toner particles have been deposited onto the electrostatic latent image for creating a toner image thereof, belt 14 becomes an image bearing support surface for advancing the developed image to transfer station 30. At transfer station 30, a print substrate (not shown) is moved into contact with the developed toner image via registration subsystem 34. At transfer station 30, a corona generating device (not shown) charges the print sheet to the proper magnitude and polarity in order to establish a transfer field that is effective to tack the print sheet to photoconductive belt 14 and to attract the developed image from the photoconductive belt 14 to the print sheet.
After transfer, a corona generator (not shown) charges the print sheet with an opposite polarity to detack the print sheet, whereupon the sheet is stripped from belt 14. The substrate is subsequently separated from the belt 10 and transported to a fusing station 50. The toner image is thereby forced into contact with the substrate between fuser rollers 54 and 58 to permanently affix the toner image to substrate. After fusing, the print substrate is advanced to receiving tray 60 for subsequent removal by an operator.
Invariably, after the print substrate is separated from belt 14, some residual developing material remains adhered to the photoconductive surface of the belt 14. Thus, a final processing station, namely, cleaning station 70, is provided for removing residual toner particles from photoreceptor belt 14.
The various machine functions are regulated by a system controller 24 having a user interface. The controller 24 is preferably a programmable microprocessor that controls all of the machine functions hereinbefore described. The controller 24 may be programmed to monitor various operating parameters of the electrostatographic machine such as print substrate type, the number of documents being re-circulated, the number of print sheets selected by the operator, time delays, and jam indications, among other various functions including transfer assist actuation. Conventional sheet path sensors or switches may be utilized to keep track of the types and position of documents and print substrates in the machine. The operation of all of the exemplary systems described hereinabove may be accomplished by conventional user interface control.
The foregoing description should be sufficient for purposes of illustrating the general operation of an electrostatographic printing machine incorporating an exemplary embodiment of an apparatus for reducing transfer deletions. As described, an electrostatographic printing machine may take the form of any of several well known devices or systems. Variations of specific electrostatographic processing subsystems or processes may be expected without affecting the operation of the exemplary embodiment.
Turning now to
The particles removed from the photoreceptor surface 14 that adhere to the brush fibers 90, 94 may be removed from the brush fibers by any suitable method. In one embodiment, the toner particles are removed from the brush fibers when the fibers contact a protruding flicker bar edge 98. The flicker bar 98 dislodges the toner and other debris particles held in the brush fibers as the brush is rotating. An air passage carries the dislodged toner particles to an air manifold 104 which has a vacuum (not shown) on its opposite end creating the air flow that moves the particles away from the brush fibers 90, 94.
Referring now to
Motor controller 88 includes memory 90. The memory 90 may be a non-volatile memory such as a read only memory (ROM) or a programmable non-volatile memory such as an EEPROM or flash memory. Of course, memory 90 may be incorporated into the motor controller 88 as shown, or may be externally located. Memory 90 may include parameters stored therein which correspond to reference PWM values of the cleaner motor. The reference PWM values may comprise PWM values that correspond to the set point velocity of the cleaner motor. The set point reference PWM values may be pre-programmed into memory 90 in the motor controller 88, hard-coded into a software program or acquired by monitoring the motor PWM during normal operating conditions. Additionally, reference PWM values that correspond to threshold values of the cleaner motor such as the upper and lower design limits as well as upper and lower limits of the expected operating range of cleaner motor may be stored or programmed into the memory 90. These values may be stored in a data structure, such as a lookup table, in the memory 90.
Cleaner motor controller 88 controls the operation of cleaner motor 84 and in turn controls movement of cleaning brushes 78, 80 in response to an actuation signal from the main controller 24. In response to the actuation signal, the motor controller drives the cleaner motor, and, consequently, the cleaner brushes, at a commanded or set point motor speed. The set point speed may be supplied by the main controller 24. Alternatively, the motor controller may be programmed with the set point motor speed. In one embodiment, the motor controller generates a PWM signal having a duty cycle calculated to drive the cleaner motor at the set point speed. The motor controller may receive feedback from the cleaner motor indicating that the motor is operating above or below the set point speed. Based on the feedback, the motor controller may vary the duty cycle of the PWM control signal to adjust the cleaner motor velocity to the set point velocity.
Thus, in one embodiment, the motor controller includes a PWM generator 94 and a feedback comparator. The PWM generator 94 is configured to generate a PWM signal with a duty cycle for driving the cleaner motor at the set point speed. The PWM 94 generator may be implemented through software or firmware running on the motor controller or main system controller. Alternatively, the PWM generator may be implemented in hardware in the motor controller.
As motor 84 turns in response to the PWM signal generated by PWM generator 94, an encoder 98 generates a feedback signal that indicates actual motor speed. Encoder 98 may comprise a photo-interrupter based encoder circuit that generates output pulses at a frequency related to the motor's rotational speed. Although an encoder is illustrated, other position sensors and position sensing methods may be used, including, but not limited to, resolvers, back-EMF sensing methods, potentiometers, and position sensors using magnetic field sensing such as hall-effect devices. The feedback comparator receives the speed feedback signal from encoder 98 as one input and receives a reference (commanded or set point speed) signal as a second input. An error signal output by feedback comparator indicates error between actual and set point speed, and thus serves as a control input to PWM generator. Based on the error signal from the feedback comparator, PWM generator may adjust the duty cycle of the PWM signal to the motor 84 in order to maintain the actual motor speed at the set point speed. For example, the duty cycle of the PWM signal may be increased to increase the actual motor speed, and the duty cycle may be decreased to decrease the actual motor speed.
During normal operations of the cleaning system, the motor controller 88 may not have to substantially vary the PWM control signal away from a nominal value to maintain the set point motor speed while driving cleaner motor 84. A catastrophic stress condition, however, may result in a dramatic adjustment of the duty cycle of the PWM signal that goes beyond the design limits of the cleaner motor. For instance, a catastrophic stress condition, such as, for example, a system or hardware malfunction that prevents the motor from turning, may result in the PWM signal reaching a saturation level (100% duty cycle). Additionally, a sudden or instantaneous loss of load caused by, for example, the cleaning brushes coming uncoupled or sheared from the output shaft of the motor, may result in sudden extreme increase in the actual motor speed that causes an adjustment of the PWM duty cycle to be 0%. Thus, a catastrophic stress condition may be detected by monitoring the PWM signal to detect occurrences of duty cycles of 0% or 100%.
A stress condition on the cleaning system that is not catastrophic may also affect the cleaner motor's ability to respond to the PWM signal albeit without causing the PWM signal to reach catastrophic stress level indicators (0% or 100% PWM). A stress condition that is not catastrophic may result in characteristic adjustments of the PWM signal within the design limits of the motor. For instance, a stress condition on the cleaning system may result in an adjusted PWM duty cycle that, while not beyond design limits of the cleaner motor, is outside of the expected operating range of the PWM signal. For electrostatic imaging devices, the cleaner motor 84 typically functions within a given operating range under normal operating conditions. The expected operating range of the cleaner motor PWM under normal operating conditions may comprise a duty cycle of between 55% and 70% PWM. A stress condition may be indicated by an adjusted PWM duty cycle that is outside the expected operating range but within the design limits of the cleaner motor PWM, i.e. greater than 0% and less than 55% PWM as well as greater than 70% and less than 100% PWM.
Additionally, a stress condition on the cleaner system may result in an aberrant adjustment of the duty cycle of the PWM signal. For instance, an aberration in the duty cycle of the PWM signal may comprise a sudden increase or decrease in the duty cycle of the PWM from a nominal value of the duty cycle. For example, a paper that remains tacked to the photoreceptor and enters the cleaner housing may cause a sudden increase in the load on the cleaner motor as the paper initially comes into contact with the cleaner brushes. The sudden increase in load may cause a sudden or abrupt increase in the duty cycle of the PWM from a nominal value to adjust for the increased load.
Thus, a stress condition that is not catastrophic may be detected by monitoring the motor PWM to determine if the PWM signal is within design limits and detecting characteristic adjustments of the PWM duty cycle that, while within design limits, indicates the occurrence of a stress condition. A characteristic adjustment indicating a stress condition other than catastrophic may comprise an adjustment of the duty cycle to be outside the expected operating range of the cleaner motor but within the design limits. Additionally, a characteristic adjustment may comprise an aberrant adjustment in the duty cycle of the PWM within the expected operating range.
Thus, referring again to
The PWM monitor may compare the monitored PWM values to the set point and threshold reference PWM values to determine if the duty cycle of the PWM is within operating limits and/or within the expected operating range of the cleaner motor. If the PWM monitor determines that the duty cycle of the PWM is not within design limits, the PWM monitor may generate an alert signal indicating a catastrophic stress condition.
Similarly, if the PWM monitor determines that the duty cycle of the PWM is within design limits but outside the expected operating range or detects aberrant adjustments to the duty cycle that may indicate a stress condition, the PWM monitor may generate an alert signal indicating a non-catastrophic stress condition. Aberrant adjustments of the PWM signal may be detected, for example, by comparing the current PWM duty cycle detected to a previous PWM duty cycle and calculating the increase in the duty cycle over a unit of time (ΔPWM/Δt). To compensate for fluctuations that may occur during normal operations, the PWM monitor may be configured to only generate an alert signal in response to sudden increases or decreases that are greater than a pre-selected magnitude or that occur for longer than a pre-selected duration.
The alert signals generated by the PWM monitor may be received by the main controller 24. An alert signal may take any form suitable to indicate the occurrence of a stress condition to the controller 24. For example, an alert signal may comprise an electric signal of a pre-determined value. In one embodiment, an alert signal may comprise an electronic message such as, for example, an email, or the like, that may be sent over a network. The controller 24, in receipt of the alert signal indicating a type of stress condition, may take appropriate action such as, for example, halting operations of the imaging device and issuing an alert by displaying a message, light, emitting an audio alert, etc., indicating that the cleaning system requires servicing. As mentioned above, a stress condition on the cleaning system may cause defects in imaging operations as well as damage to equipment. By halting operations upon detection of a stress condition, print defects may be prevented in subsequent prints. Additionally, damage to equipment may be limited by halting operations as soon a stress condition is detected.
In one embodiment, detecting a characteristic adjustment of the duty cycle indicating an occurrence of a non-catastrophic stress condition in the cleaning system comprises detecting a duty cycle of the PWM signal that is within design limits and outside of an expected operating range (block 418). The expected operating range of the duty cycle of the PWM signal may be between 55-70%. In another embodiment, detecting a characteristic adjustment of the duty cycle indicating an occurrence of a non-catastrophic stress condition in the cleaning system comprises detecting a sudden increase in the duty cycle of the PWM signal that is within an expected operating range (block 420). The alert signal may be generated if the sudden increase in the duty cycle of the PWM signal is greater than a pre-selected magnitude and/or greater than a pre-selected duration.
Those skilled in the art will recognize that numerous modifications can be made to the specific implementations described above. Those skilled in the art will recognize that the electrostatographic imaging device may take the form of any of several known devices or systems. Variations of specific electrostatographic processing subsystems or processes are contemplated within the scope of this disclosure. Moreover, although xerographic imaging devices are described in the embodiments, the claimed invention is applicable to other types of printing as well, such as offset, ink-jet printing, or the like, in which one or more layers of ink/toner are built up on a surface before being transferred to paper. Therefore, the following claims are not to be limited to the specific embodiments illustrated and described above. The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
