Patent Application
20150086231
None.
None.
1. Field of the Disclosure
The present disclosure relates generally to controlling a fuser assembly in an electrophotographic imaging device, and particularly to maintaining temperature levels in the fuser assembly to allow for multiple media widths to print at full speed without overheating any portion of the fuser assembly.
2. Description of the Related Art
In an electrophotographic (EP) imaging process used in printers, copiers and the like, a photosensitive member, such as a photoconductive drum or belt, is uniformly charged over an outer surface. An electrostatic latent image is formed by selectively exposing the uniformly charged surface of the photosensitive member. Toner particles are applied to the electrostatic latent image, and thereafter the toner image is transferred to a media sheet intended to receive the final image. The toner image is fixed to the media sheet by the application of heat and pressure in a fuser assembly. The fuser assembly may include a heated roll and a backup roll forming a fuser nip through which the media sheet passes. Alternatively, the fuser assembly may include a fuser belt, a heater disposed within the belt around which the belt rotates, and an opposing backup member, such as a backup roll.
In a belt fusing system, an endless belt surrounds a ceramic heater element. The belt is pushed against the heater element by a pressure roller to create a fusing nip. To be able to fuse the widest media that the printer is designed to print, the length of the heating region is typically about the same width or slightly longer than the width of the widest media supported by the printer. The fusing heat is typically controlled by measuring the temperature of the heating region with a thermistor held in intimate contact with the ceramic heater element and feeding the temperature information to a microprocessor-controlled power supply in the printer, which in turn applies power to the heater element when the temperature drops below a first predetermined level, and which interrupts power when the temperature exceeds a second predetermined level. In this way, the fuser is maintained within an acceptable range of fusing temperatures.
When a to-be-printed media sheet has a width narrower than the width of the widest media supported by the printer, overheating problems may occur because the media sheet removes heat from the fuser only in the portion of the fuser contacting the media. As the portion of the fuser beyond the width of the media sheet does not lose any heat to the media sheet, such portion of the fuser becomes hotter than the portion contacting the media sheet and can be damaged due to high temperature.
Since excessive thermal energy accumulated at the portion of the fuser not contacting the media (hereinafter “non-media portion”) during narrow media printing can cause damage to the fuser, it is desirable to control the amount of thermal energy accumulated at the non-media portion to be below a certain level so that the fuser will not be damaged. To control the thermal energy accumulated at the non-media portion of the fuser, prior attempts used sensors and/or user-provided information to detect media width. If the media width is less than the full width, process speed is typically reduced and/or the interpage gap is increased to limit the overheating of the non-media portion. By doing so, however, throughput of the printer is reduced when printing media sheet sizes that are less than the widest supported media size leading to reduced performance levels.
Further, as machine speeds increase, the tolerable range of media width variation at full speed becomes smaller. For example, in the case of printers operating at 60 ppm and above, a media width difference of 3-4 mm may be enough to cause problematic overheating in the small portion of the fuser beyond the media. In other example cases, printers are equipped with letter width or A4 width heaters. However, if the heater width does not match the media width, problems may occur. For example, printers designed for letter width media and operating at 60 ppm or greater may cause the non-media portion of the fuser to overheat if A4 width media is used. Conversely, if letter width media is used in a printer designed for A4 width media, toner that is on the portion of the letter width media beyond the A4 edge may not be sufficiently fused.
Accordingly, there is a need for an improved system for controlling thermal energy in a fuser assembly.
Embodiments of the present disclosure provide systems for controlling temperature of portions of a heater of a fuser assembly that would allow for an image forming device to operate substantially at full speed regardless of the width of a media being fused and without user intervention.
In one example embodiment, a fuser assembly for an electrophotographic imaging device includes a housing, an endless belt rotatably positioned about the housing and having an inner surface, a backup roll disposed substantially against the endless belt proximal to an outer surface thereof so as to form a fuser nip with the belt, and a heater disposed substantially within the housing. The heater includes a substrate and at least one resistive trace disposed along a surface of the substrate, running a length of the substrate and generating heat for fusing toner to a sheet of media when a current is passed therethrough. The heater further includes at least three conductors for passing current through the at least one resistive trace. The at least three conductors include a first conductor connected to a first end portion of the at least one resistive trace, a second conductor connected to a second end portion of the at least one resistive trace, and a third conductor connected to the at least one resistive trace at a first location between the first end portion and the second end portion of the at least one resistive trace. A temperature sensor is disposed on the substrate to sense a temperature thereof at a location that is offset from the first location for generating a signal having a value that is based upon the sensed temperature. Circuitry is communicatively coupled to the temperature sensor and the first and third conductors for comparing the signal generated by the temperature sensor with a predetermined value. Based upon the comparison, the circuitry selects between the first conductor and the third conductor for passing current through the at least one resistive trace.
In another example embodiment, the at least three conductors further includes a fourth conductor connected to the at least one resistive trace at a second location between the second end portion and the first location of the at least one resistive trace. The circuitry selects between the second conductor and the fourth conductor for passing the current through the at least one resistive trace based upon the comparison.
The above-mentioned and other features and advantages of the disclosed example embodiments, and the manner of attaining them, will become more apparent and will be better understood by reference to the following description of the disclosed example embodiments in conjunction with the accompanying drawings, wherein:
It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. Terms such as “first”, “second”, and the like, are used to describe various elements, regions, sections, etc. and are not intended to be limiting. Further, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Furthermore, and as described in subsequent paragraphs, the specific configurations illustrated in the drawings are intended to exemplify embodiments of the disclosure and that other alternative configurations are possible.
Reference will now be made in detail to the example embodiments, as illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.
Each developer unit 20 is operably connected to a toner reservoir 35 for receiving toner for use in a printing operation. Each toner reservoir 35 is controlled to supply toner as needed to its corresponding developer unit 20. Each developer unit 20 is associated with a photoconductive member 40 that receives toner therefrom during toner development to form a toned image thereon. Each photoconductive member 40 is paired with a transfer member 45 to define a transfer station 50 for use in transferring toner to ITM 30 at first transfer area 15.
During color image formation, the surface of each photoconductive member 40 is charged to a specified voltage by a charge roller 55. At least one laser beam LB from a printhead or laser scanning unit (LSU) 60 is directed to the surface of each photoconductive member 40 and discharges those areas it contacts to form a latent image thereon. In one embodiment, areas on the photoconductive member 40 illuminated by the laser beam LB are discharged. The developer unit 20 then transfers toner to photoconductive member 40 to form a toner image thereon. The toner is attracted to the areas of the surface of photoconductive member 40 that are discharged by the laser beam LB from LSU 60.
ITM 30 is disposed adjacent to each of developer unit 20. In this embodiment, ITM 30 is formed as an endless ITM disposed about a drive roller and other rollers. During image forming operations, ITM 30 moves past photoconductive members 40 in a clockwise direction as viewed in
ITM 30 rotates and collects the one or more toner images from the one or more photoconductive members 40 and then conveys the one or more toner images to a media sheet at a second transfer area 65. Second transfer area 65 includes a second transfer nip formed between a back-up roller 70 and a second transfer member 75.
A fuser assembly 80 is disposed downstream of second transfer area 65 and receives media sheets with the unfused toner images superposed thereon. In general terms, fuser assembly 80 applies heat and pressure to the media sheets in order to fuse toner thereto. After leaving fuser assembly 80, a media sheet is either deposited into an output media area 85 or enters duplex media path 90 for transport to second transfer area 65 for imaging on a second surface of the media sheet.
Image forming device 10 is depicted in
Image forming device 10 further includes a controller 95 and an associated memory 97. Memory 97 may be any volatile and/or non-volatile memory such as, for example, random access memory (RAM), read only memory (ROM), flash memory and/or non-volatile RAM (NVRAM). Alternatively, memory 97 may be in the form of a separate electronic memory (e.g., RAM, ROM, and/or NVRAM), a hard drive, a CD or DVD drive, or any memory device convenient for use with controller 95. Though not shown in
With reference to
Fuser belt 120 is disposed around housing 110 and heater element 115. Backup roll 105 contacts fuser belt 120 such that fuser belt 120 rotates about housing 110 and heater element 115 in response to backup roll 105 rotating. With fuser belt 120 rotating around housing 110 and heater element 115, the inner surface of fuser belt 120 contacts heater element 115 so as to heat fuser belt 120 to a temperature sufficient to perform a fusing operation to fuse toner to sheets of media.
Fuser assembly 80 may be configured for fusing toner to media sheets of different widths. With reference to
Referring now to
Conductors 135 generally provide paths for electrical energy from power supply 145 to travel through resistive trace 130. In the example shown, first conductor 135A, second conductor 135B, and third conductor 135C are connected to resistive trace 130 at different locations thereof. In particular, first conductor 135A is connected to the first end portion 130A, second conductor 135B is connected to the second end portion 130B, and third conductor 135C is connected to resistive trace 130 at a location 130C that is laterally offset from the first end portion 130A and between the first and second end portions 130A, 130B. A temperature sensor 150 is coupled to substrate 125 at a location between the locations at which first conductor 135A and third conductor 135C are connected to resistive trace 130 for sensing a temperature of a substrate region corresponding to an edge segment 155 of the length of resistive trace 130. Temperature sensor 150 may be disposed on the side of heater element 115 opposite the surface along which resistive trace 130 is disposed.
In an example embodiment, the location at which first conductor 135A is connected to resistive trace 130 may correspond to an edge 160 (
One or more of conductors 135 may be selectively coupled to power supply 145 by a control circuit 200 to control the flow of current through resistive trace 130 based on the temperature sensed by temperature sensor 150. In an example embodiment, control circuit 200 may be contained within fuser assembly 80. For example, control circuit 200 may be disposed on or within fuser housing 98. In addition, control circuit 200 may operate independently from controller 95. In particular, in the embodiment of
Control circuit 200 may include a comparator circuit 205 and a switch 210. As shown in
In operation, controller 95 may control power supply 145 to provide electrical power to resistive trace 130 via first and second terminals 145A, 145B for heating heater element 115 to a target fusing temperature level. Switch 210 may connect first conduction terminal 210A to second conduction terminal 210B, as shown in
When fusing toner onto a sheet of narrower supported media while current flows between first conductor 135A and second conductor 135B of heater element 115, the temperature of the portion of heater element 115 corresponding to edge segment 155 may increase more rapidly than the temperature of the length of heater element 115 corresponding to the width of narrower supported media. In an example embodiment, detecting a temperature that exceeds the first predetermined temperature level may indicate that the region corresponding to the edge segment 155 of heater element 115 is overheating due to the sheet of narrower media passing through fuser nip N and absorbing heat energy of heater element 115 only along the length thereof contacted by the media sheet. Accordingly, if the temperature sensed by temperature sensor 150 exceeds the first predetermined temperature level, comparator circuit 205 compares the voltage corresponding to the sensed temperature with the voltage corresponding to the first predetermined temperature level and in response causes its output to switch binary states, which thereby causes switch 210 to disconnect its first conduction terminal 210A from second conduction terminal 210B so as to decouple first conductor 135A from power supply 145, and to connect third conduction terminal 210C to second conduction terminal 210B to couple third conductor 135C to power supply 145 and thereby cause current to flow between and through third conductor 135C and second conductor 135B. In this way, the current flow path is redirected such that only the length of heater element 115 contacted by the narrower media sheet is substantially heated to the target temperature level while preventing overheating at the non-media portion. In other words, a current path through heater element 115 is selected so that only the portion of heater element 115 corresponding to the location of the narrower media sheet is heated as the sheet is passed through fuser assembly 80.
In an example embodiment, comparator circuit 205 may further be configured to compare the voltage corresponding to the temperature sensed by temperature sensor 150 to a voltage corresponding to a second predetermined temperature level that is less than the first predetermined temperature level. The second predetermined temperature level may correspond to a temperature level in which the amount of thermal energy is not sufficient for fusing toner onto a sheet of media. Comparator circuit 205 comparing the voltage corresponding to the sensed temperature to voltages corresponding to both the first and second predetermined temperature levels is accomplished by comparator circuit 205 having hysteresis with switching voltages being the voltages corresponding to the first and second predetermined temperature levels. Comparator circuits having hysteresis are well known in the art such that a detailed description thereof will not be provided for reasons of simplicity. It is understood that the comparator circuits described below include hysteresis.
Heat generated by passing current through the portion of resistive trace 130 between and through third conductor 135C and second conductor 135B may transfer and/or dissipate in the longitudinal direction of heater element 115 and into edge segment 155, thereby heating edge segment 155 to some extent. In the event that a sheet of widest supported media is fed into fuser nip N while the current of resistive trace 130 passes through third conductor 135C, any heat transferred to edge segment 155 from the portion of heater element 115 between second conductor 135B and third conductor 135C may be absorbed by the sheet of media which may cause the temperature of edge segment 155 to drop below the second predetermined temperature level. In an example embodiment, detecting a temperature that is below the second predetermined temperature level may indicate that the sheet of media passing through fuser nip N is a widest supported media while heater element 115 is heated for fusing narrower media. If the sensed temperature is below the second predetermined temperature level, comparator circuit 205 may compare the voltage corresponding to the sensed temperature to the voltage corresponding to the second predetermined level and cause its output to change binary states to disconnect its third conduction terminal 210C from second conduction terminal 210B and thereby decouple third conductor 135C from power supply 145, and to connect first conduction terminal 210A to second conduction terminal 210A to couple first conductor 135A to power supply 145. This coupling establishes the current of resistive trace 130 to flow through first conductor 135A and second conductor 135B. Thus, control circuit 200 selects the current path through resistive trace 130 such that entire length L1 of heater element 115 is substantially heated to the target temperature level to accommodate the sheet of widest supported media.
In an alternative example embodiment, control circuit 200 may employ a shunt configuration for switching the current between flowing through first conductor 135A and flowing through third conductor 135C. For example, in the embodiment shown in
In operation, when passing current through first conductor 135A (i.e., switch 212 being open for fusing wider media), in the event the temperature sensed by temperature sensor 150 exceeds the first predetermined temperature level (indicating narrower media being fused), comparator circuit 205 compares the voltage corresponding to the sensed temperature with the voltage corresponding to the first predetermined temperature level and causes the output of comparator circuit 205 to change binary state which closes switch 212 so that current is thereafter redirected through third conductor 135C (for fusing narrower media). In addition, when passing current through third conductor 135C (i.e., switch 212 being closed for fusing narrower media), in the event the temperature sensed by temperature sensor 150 falls below the second predetermined temperature level (indicating wider media being fused), comparator circuit 205 compares the voltage corresponding to the sensed temperature with the voltage corresponding to the second predetermined temperature level and causes the output of comparator circuit 205 to change binary state which opens switch 212 so that the current is redirected through first conductor 135A (for fusing wider media).
The above example embodiments have been described with respect to a reference-edge media feed system where one side of the media sheet is in a substantially constant location within fuser assembly 80 regardless of the media width. In another example embodiment, the applications described herein may also be used in center-referenced media feed systems where media sheets move at a center position along the media path and locations of both edges of the media sheet vary with media width.
With reference to
Referring now to
A first edge temperature sensor 250A may be coupled to the substrate of heater element 115 on a side opposite from the surface along which resistive trace 230 is disposed and at a location between the locations at which first and third conductors 235A, 235C are connected to resistive trace 230 for sensing a temperature of a region corresponding to a first edge segment 255A of resistive trace 230. Additionally or optionally, a second edge temperature sensor 250B may be coupled to the substrate of heater element 115 at a location between the locations at which second and fourth conductors 235B, 235D are connected to resistive trace 230 for sensing a temperature of a region corresponding to a second edge segment 255B of resistive trace 230 opposite the first edge segment 255A thereof.
Conductors 235 may be selectively coupled to power supply 145 by a control circuit 300 to control the flow of current through resistive trace 230 based on the temperature sensed by at least one of the first and second edge temperature sensors 250A, 250B. Control circuit 300 may include a comparator circuit 305 having hysteresis as described above, a first switch 310, and a second switch 315. Comparator circuit 305 has an input coupled to first edge temperature sensor 250A and an output coupled to first and second switches 310, 315. If second edge temperature sensor 250B is used, comparator circuit 305 may have a second input coupled thereto. Comparator circuit 305 may receive signals generated by each of the first and second edge temperature sensors 250A, 250B having values that are based upon temperatures sensed thereby, compare the received signals with one or more predetermined values corresponding to one or more predetermined temperature levels, and output a signal based upon the comparison.
Each of first switch 310 and second switch 315 includes a plurality of conduction terminals, such as first conduction terminals 310A, 315A, second conduction terminals 310B, 315B, and third conduction terminals 310C, 315C, respectively. First conduction terminals 310A, 315A are connected to first and second conductors 235A, 235B, respectively, while third conduction terminals 310C, 315C are connected to third and fourth conductors 235C, 235D, respectively. Second conduction terminal 310B of first switch 310 is connected to second terminal 145B of power supply 145 and second conduction terminal 315B of second switch 315 is connected to first terminal 145A of power supply 145. Control circuit 300 may select the conductors 235 for passing current through resistive trace 230 and specifically control current to flow either through first and second conductors 235A, 235B or through third and fourth conductors 235C, 235D. Comparator circuit 305 actuates first and second switches 310, 315 based on the temperature(s) sensed by at least one of the first and second edge temperature sensors 250A, 250B in order to control the generation of heat across at least portions of the length of resistive trace 230 to prevent overheating.
In operation, controller 95 may control power supply 145 to provide electrical power to resistive trace 230 via first and second terminals 145A, 145B for heating heater element 115 to a target fusing temperature level. First switch 310A is controlled to connect its first conduction terminal 310A to second conduction terminal 310B and second switch 315 is controlled to connect its first conduction terminal 315A to second conduction terminal 315B to cause current to flow in resistive trace 230 through conductors 235A and 235B. First and second edge temperature sensors 250A, 250B positioned proximate to the first and second end portions 230A, 230B of resistive trace 230 measure the temperature of the regions corresponding to first and second edge segments 255A, 255B, respectively.
Comparator circuit 305 compares the voltage corresponding to the temperature sensed by one or more of edge temperature sensors 250A, 250B to the voltage corresponding to the first predetermined temperature level. If the temperature(s) sensed is less than the first predetermined temperature level, it is indicative of a sheet of media having a width corresponding to media sheet M1 that does not result in overheating, and control circuit 300 may maintain current flow through resistive trace 230 via conductors 235A and 235B to accommodate fusing of media sheet M1. If any temperature sensed exceeds the first predetermined temperature level, it is indicative of overheating at regions corresponding to first edge segment 255A and/or second edge segment 255B due to narrower media sheet M2 being fused. In response, comparator circuit 305 actuates first and second switches 310, 315 which in turn disconnect corresponding first conduction terminals 310A, 315A from respective second conduction terminals 310B, 315B and connect corresponding third conduction terminals 310C, 315C to respective second conduction terminals 310B, 315B. Accordingly, a current flow path is established which allows current to flow through resistive trace 230 via third and fourth conductors 235C, 235D. In this way, current flow may be controlled to follow a path defined by the inner conductors such that fusing temperature levels may exist only within functional areas of heater element 115 corresponding to the width of the narrower sheet of media M2 while preventing overheating at the non-media portions.
In the event that a sheet of media M1 is fed into fuser nip N while the third and fourth conductors 235C, 235D are used to provide current through resistive trace 130, heat of the region corresponding to the edge segments 255A, 255B may drop due to heat absorption by the sheet of media at the edges thereof. In an example embodiment, comparator circuit 305 may further be configured to compare the voltage corresponding to the temperature sensed by at least one of the edge temperature sensors 250A, 250B to the voltage corresponding to the second predetermined temperature level. If the temperature sensed by one of the edge temperature sensors 250A, 250B falls below the second predetermined temperature level, and if the temperature sensed by the other edge temperature sensor 250A, 250B is below the first predetermined temperature, the output of comparator circuit 305 changes binary state to actuate first and second switches 310, 315 to disconnect corresponding third conduction terminals 310C, 315C from respective second conduction terminals 310B, 315B and connect corresponding first conduction terminals 310A, 315A to respective second conduction terminals 310B, 315B. Accordingly, a resistive trace current flow path is established through first and second conductors 235A and 235B, respectively, such that the length of heater element 115 corresponding to the width of the sheet of media M1 is heated to the target temperature level to accommodate fusing of the entire width of the sheet of media.
In an alternative example embodiment shown in
In another example embodiment, heater element 115 may include a plurality of resistive traces of differing lengths to accommodate multiple media sheet sizes in a center-referenced feed system. For example, in
Illustrative examples of control configurations have been described using three or four conductors, one or two resistive traces, and a given number of comparator circuits and switches that would accommodate two different media sheet sizes. However, it is understood that a multiplicity of conductors, resistive traces, and any number of comparator circuits or switches may be implemented to accommodate more than two media sheet sizes.
With the above example embodiments, one or both edges of the heater element 115 may be equipped with self-controlling segments to prevent overheating the edge segments thereof. Temperature information sensed by temperature sensor(s) at the edge segments may be fed to one or more control circuits which in turn controls the switching of one or more switches to select a current path through and otherwise control the flow of current through the resistive trace and, consequently, control at least portions of the resistive trace to heat to desired temperature levels based on the temperature information. Accordingly, no operator intervention may be needed to configure fuser assembly 80 for the media width being used, and fuser assembly 80 can operate substantially at full speed regardless of which media width is being used. Additionally, since control circuitries are contained within the fuser assembly 80 and since no logic, temperature feedback, or additional interaction/communication is required between the fuser assembly control circuitry and the image forming device controller, any image forming device can be configured as a multiple-media width imaging device by simply removing a traditional single-width fuser and installing a multiple-width fuser equipped with self-controlling segments described herein.
The foregoing description of several example embodiments of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.
Pursuant to 35 U.S.C. §119, this application claims the benefit of the earlier filing date of Provisional Application Ser. No. 61/883,036, filed Sep. 26, 2013, entitled “Fuser with Automatic Paper Width Sensing and Thermal Compensation,” the content of which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61883036 | Sep 2013 | US |
