US3849628A

US3849628A - Non-contact temperature sensor for a roll fuser of a xerographic reproduction apparatus

Info

Publication number: US3849628A
Application number: US00382434A
Authority: US
Inventors: G Abowitz; F Ruckdeschel; R Gerace
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-07-25
Filing date: 1973-07-25
Publication date: 1974-11-19
Anticipated expiration: 1991-11-19
Also published as: FR2238964A1; CA1021012A; NL7405481A; DE2420161A1; JPS5044839A

Abstract

Apparatus for fusing toner material to a substrate by passing the substrate between a pair of rollers at least one of which is heated. The surface temperature of the heated roller at an area where it contacts the toner material is maintained at a substantially constant value by means of a non-contact sensor comprising a part of a control for the heated roll.

Description

[ Nov. 19, 1974 United States Patent [191 Abowitz et al.

X on H 00 3 3 1 NON-CONTACT TEMPERATURE SENSOR 3,189,729 6/1965 Lusebrink........................... FOR A ROLL FUSER OF A XEROGRAPHIC 3,369,106 2/1968 Troll REPRODUCTION APPARATUS 3,654,463 4/1972 Geuslc et a1.

3,697,726 10/1972 Geromme [75] Inventors: Gerald Abowitz, Rochester; 3,725,310 4/1973 Donohue......

Frederick Robert Ruckdeschel, 3,735,092 5/1973 Traister......,,. Webster; Robert Eugene Gerace 3,742,191 6/1973 Poole et Fairport, all of NY.

OTHER PUBLICATIONS D. N. Neal, G. C. Greuling, IBM Technical Disclosure Bulletin, Moving Surface Temperature Sensor, Vol. 14, No. 6, November 1971 [73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: July 25, 1973 App]. No.: 382,434 Primary Examiner-C. L, Albritton [52] US. 219/216, 219/471, 338/15 [51] Int. Cl. H05b l/00 [58] Field of Search.................... 219/216, 469-471;

References Cited UNITED STATES PATENTS f o t vm 0. m. mm S Cm. m H m u .mo .We m0 F a g aw .m bn w La s llr admD mmw dM Q, e m n C .l mn a toea .m h 33 7 m m 8 SI .mwm rem m w y mba 2,627,182 Quereau et a1. 338/25 X 3,093,744 250/239 S C. R.

CONTROLLER A.C. TO D.C.

CONVERT LAMP SOURCE PATENTE 510v 1 91914 sum 1 or a PATENI'E rm 1 91914 sum 2 or 3 PATENTE HEY I 9 I974 NEH 3m 3 I I u.v.

HEAT HEAT LIGHT FUSER l SILICONE l PHOSPHOR l u.vv

LA MP RUBBER RoI I STRIP LAMP VISABLE LIGHT REG. zav us.

58 56 4a 59 I I s. c. R. PHOTORESISTIVE POWER AMPLIFIER CONTROLLER 7 CELL SUPPLY CONTROL RES. T VOLTAGE CHARGE I20 v. I20 v.

A0. T0 0.0. s. c. R.

CONVERT V CONTROLLER 46 LAMP SOURCE ROLL FUSER OF A XEROGRAPHIC REPRODUCTION APPARATUS BACKGROUND OF THE INVENTION This invention relates, in general, to heated roll fuser apparatus for affixing toner material to a substrate to form permanent images thereon and, more particularly, to means for controlling the power input to the heated roll for maintaining substantially constant the surface temperature of the heated roll at an area where it contacts the toner material.

In the process of xerography, a light image of an original to be copied is typically recorded in the fonn of a latent electrostatic image on a photosensitive member with subsequent rendering of the latent image visible by the application of electroscopic marking particles, commonly referred to as toner. The visual image can be either fixed directly upon the photosensitive member or transferred from the member to a sheet of plain paper with subsequent affixing of the image thereto.

In order to permanently affix or fuse an electroscopic toner material onto a support member by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This action causes the toner to be absorbed to some extent into the fibers of the support member which in many instances constitutes plain paper. Thereafter, as the toner material is cooled, solidification of the toner material occurs causing the toner material to be firmly bonded to the support member.

In both the xerographic as well as the electrographic recording arts, the use of thermal energyfor fixing toner images onto a support member is old and wellknown.

One approach to thermal fusing of electroscopic toner images onto a support has been to pass the support with the toner images thereon between a pair of opposed rollers, at least one of which is either externally or internally heated. In this type of arrangement, the toner image contacts the surface of the heated roller member in the nip between rollers to thereby produce heating of the toner image within the nip.

In apparatus utilizing a fuser roll pair as described above, it is important that the heated roll surface be maintained within a suitable range to properly fuse the toner image to its paper support sheet. The foregoing is accomplished in a conventional manner by the employment of a temperature sensitive resistance device commonly referred to as a thermistorwhich is placed in physical contact with the heated roll.

In a conventional roll fuser, the fuser roll or heated member is almost always provided with a release agent applied to the surface thereof in order to prevent offsetting of toner material to the fuser roll. The release agent is, at least at the time that the application to the fuser roll has been accomplished, in the form of a liquid and has the effect of minimizing the thermal energy generated by frictional forces due to rubbing between the fuser roll surface and the thermistor.

Where, as in the case of the present invention, the fuser .roll surface comprises an elastomeric or other highly susceptible heat generating material that does not have a release agent applied to the surface thereof, the heat developed due to friction has a considerable effect on the temperature sensing device. For example, if the control setting of the temperature sensor is at a particular setting corresponding to the temperature of the fuser roll desired, the temperature sensor due to frictional forces will sense temperatures on the order to 20 higher than the actual surface temperature of the fuser roll. As will be appreciated, this creates all sorts of problems resulting in an unsatisfactory control of the fuser device.

One solution to the problem would be to set the control temperature of the sensor or probe at a setting 20 higher than that to which the fuser roll surface is to be maintained, in an area just preceding the nip. This would result in an elevated temperature resulting in *overshoot" presenting the problem of hot offsetting" as well as causing drying out of the paper resulting in paper curling leading to paper jams or potential fire hazards.

Overshoot occurs when the temperature sensor shuts off the fuser heater, due to the fact that the thermal energy accumulated at the center of the fuser roll continues after heater deenergization to be transferred radially outward to the surface of the fuser roll. Hot offsetting occurs when the surface of the fuser is raised to a level sufficient to melt the toner particles thereby creating a condition where the toner material splits resulting in some of the toner being picked up by the fuser roll surface.

Other solutions to the problem have been envisioned but they have resulted in more expensive or more complicated control devices than warranted by other'machine requirements.

Accordingly, it is a primary object of this invention to provide a new and improved electrostatic reproducing apparatus employing heat to fuse toner images to the support paper.

Another object of this invention is to provide a new and improved fusing device for an electrostatic copier wherein toner images are formed on a copy paper.

Still another object of the present invention is to provide a new and improved fusing device for a xerographic reproducing apparatus including a novel method of controlling the surface temperature of the fuser roll.

Yet another object of this invention is to provide a new and improved thermal fusing device for xerographic reproducing apparatus wherein the improvements in the fusing device are accomplished by the provision of a non-contact sensor.

A BRIEF DISCLOSURE OF THE INVENTION Briefly, the above-cited objects are accomplished by the provision of a non-contact sensor and control therefor for maintaining the temperature of the fuser roll substantially constant in an area where it contacts toner material.

More specifically, the objects of the present invention are accomplished by the provision of a photodiode for measuring the light output of a phosphor material which in one embodiment of the invention is formed integrally with the surface of the fuser roll. Since the light emissions from the phosphor material can be correlated to the temperature of the phosphor material which in turn is a function of the surface temperature of the roll, the surface temperature can be accurately measured and used for controlling the power input to the fuser roll for the purpose of maintaining the temperature thereof, substantially constant.

In other embodiments of the invention, the phosphor material may comprise a part of a device which is mounted adjacent the fuser roll and whose light emissive characteristics are measured in the same manner as mentioned above.

Where the phosphor material is an integral part of the fuser roll, it may be uniformly dispersed throughout the surface of the fuser roll or may constitute a continuous or broken stripe about the circumference of the roll.

Further objects of this invention, together with additional features contributing thereto and advantages accruing therefrom, will become readily apparent from the following description of the preferred embodiment of the invention when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a front elevational view of an automatic xerographic reproducing apparatus utilizing the present invention;

FIG. 2 is a perspective view partly in section of a fusing device incorporated in the apparatus of FIG. 1;

FIG. 3 is a schematic diagram of a fuser control used in conjunction with the fuser apparatus illustrated in FIG. 1;

FIG. 4 is a schematic representation of a modified form of control illustrated in FIG. 3 for controlling the surface temperature of the fuser roll;

FIG. 5 is a fragmentary view of another modification of the invention; and

FIG. 6 is yet another modification of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there is shown an embodiment of the subject invention in a suitable environment such as an automatic xerographic reproducing machine having a xerographic plate including a photoconductive layer or light sensitive surface on a conductive backing and formed in the shape of a drum 10 which is mounted on a shaft journaled in a frame to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For purposes of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally as follows:

A charging station A at which the photoconductive layer of the xerographic drum is uniformly charged;

An exposure station B at which a light or radiation pattern of a document to be reproduced is projected onto the drum surface to dissipate the drum charges in the exposed areas thereof, thereby forming a latent electrostatic image of the copy to be reproduced;

A transfer station B at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer support material; and

A drum cleaning and discharge station E at which the drum surface is brushed to remove residual toner particles remaining thereon after image transfer, and at which the drum surface is exposed at a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

At the transfer station D, a transfer of the xerographic powder image from the drum surface to the sheets of support material is effected by means of a corona transfer device 16 which is located at or immediately after the line of contact between support material and the rotating drum. In operation, the electrostatic field created by the corona transfer device is effective to tack the support material electrostatically to the drum surface whereby the support material moves synchronously with the drum while in contact therewith. Simultaneously with the tacking action, the electrostatic field is effective to attract the toner particles comprising the xerographic powder image from the drum surface and cause them to adhere electrostatically to the surface of the support material.

Immediately subsequent to the image transfer station, there is positioned a stripping apparatus 18 for removing the sheets of support material from the drum surface. The heat stripping apparatus is adapted to strip the leading edge of the support material from the drum surface and to direct it onto an endless conveyor 20 which carries the sheet material to a heated fusing roll apparatus 30. The support material is passed through a top roll or cylinder 34 and a lower roll 36, which is displaceable, to permanently affix or fuse the image by a combination of heat and pressure. The roll 34 has an outer cover 37 made of silicone rubber or other suitable elastromeric material, supported by a rigid base 38 and having a thicker elastomeric layer 39 interposed therebetween.

A quartz lamp 40 and reflector 42 therefor are disposed adjacent the fuser roll 34 and are coextensive with the longitudinal axis of the fuser roll. The lamp 40 has a maximum output of 1100 watts when provided with power from a volt-60 cycle source. With an 1,100 watt output, the lamp can raise the surface temperature of the fuser roll 34 to a level which will cause coalescence of the toner particles which level, as will be appreciated, will vary in accordance with the thermal characteristics of the toner material employed. With such an arrangement, the surface temperature of the fuser roll will be on the order of 200 to 400F. The actual output from the lamp will be controlled in accordance with the actual temperature of the roll surface and with the desired temperature. To this end, the roll as illustrated in FIG. 2 contains a stripe 44 of thermographic phosphor material and a source 46 of ultraviolet light is positioned adjacent to the roll 34 such that the phosphor material is excited by the ultraviolet light. An electro-optical detector, for example, a photoresistive member or cell 48 is also supported adjacent the fuser roll 34 such that the light emissions from the phosphor stripe are presented thereto for purposes to be explained hereinbelow, Thermographic phosphors have the property that when excited by ultraviolet light, they emit visible light, the intensity of which is dependent upon the density recombination levels near the valance band edge. A rise in temperature of the phosphor with a constant source of UV reduces the number of levels available for radiative recombination and thereby diminishes the light output. Several such phosphors are available from US. Radium Company under the trade name Radelin. The mid-range brightness of such phosphors is on the order of l erg. per cm second which is easily detected by inexpensive commercially available photodiodes. The-sensitivity of these materials in l5percentK.

While the phosphor material which is integral with the fuser roll 34, is illustrated as being applied to the surface of the roll in the form of a continuous stripe around the circumference, it will be appreciated that it could be applied to the whole surface or a broken or segmented stripe (FIG. 4) or as a single spot. Clear RTV compounds have been found suitable as binder materials for the phosphor.

The source 46, preferably a 2 watt UV lamp commercially available from the General Electric Company, and the photoresistive member 48 may as shown in FIG. 2, be contained in a common holder 50 fabricated from aluminum or other suitable material. When so mounted, the light emitted from the phosphor is transmitted by a fiber bundle 52 to the photoresistive member 48.

FIG. 3 illustrates a closed loop control system wherein the output signal (corresponding to the roll surface temperature) of the photoresistive cell 48 is amplified by an amplifier 56, the amplified signal being transmitted to an SCR controller 58 which provides power to the lamp 40 in accordance with the temperature sensor and the resulting signals generated. In operation, the heat raises the surface temperature of the roll to a point where the amplified signal approaches the set point of the SCR resulting in the reduction of power to the lamp thereby maintaining the fuser temperature to a substantially constant value. Surface temperature control within plus or minus 2F. has been obtained under constant thermal loading. A power supply 59 providing a regulated 28 volt D.C. supply is provided for the UV lamp 46.

FIG. 4 illustrates a modified form of the invention wherein the fuser roll 34 is replaced by a roll 60 having segments 62 of phosphor material extending about the circumference of the roll 60. Unlike the DC. signal generated by the continuous stripe 44, the segments 62 will generate sinusoidal signals which have the advantage of an AC. amplifier which is more stable than the DC. signal and a more even temperature gradient across the broken path formed by the segments 62. In this embodiment, the A.C. signal from a photoresistive element 64 is preamplified in a preamplifier 66 with subsequent amplification by an amplifier 68. The AC. signal is converted by an A.C. to DC. converter 70 and transmitted to an SCR controller 72 which as in the case of the embodiment of FIG. 3 is utilized to regulate the output of the lamp.

As illustrated in FIG. 5, the phosphor material need not form an integral part of the fuser roll but may form a part of a thin, heat-resistant substrate 76, for example, mica, which is disposed adjacent to the surface of a fuser roll 78. In this case, the detector and signal generator is in the form of a photodiode 80 having a UV attenuator 82 (glass) at the entrance thereof.

Asillustrated in FIG. 6, the phosphor may form an integral part of an electroluminescent panel 86 also positioned adjacent the fuser roll 78.

While the invention has been described with reference to specific embodiments disclosed, it will be appreciated that certain modifications will appear to those skilled in the art without departing from the spirit and scope of this invention. It is, therefore, intended that the invention not be limited by the embodiments disclosed but that the protection sought be limited only by the claims appended hereto which would include those modifications mentioned above.

What is claimed is:

l. Fuser apparatus comprising:

a first roller;

a second roller cooperating with said first roller to form a nip through which a substrate supporting toner material is moved;

means for heating at least one of said rollers to elevate the surface temperature thereof to a level sufficient to render the toner material tacky;

means out of contact from said at least one of said rollers for sensing the surface temperature thereof; and

means responsive to the temperature sensed for controlling said heating for maintaining the surface temperature of said at least one of said rollers constant in an area where the toner material is contacted thereby, said means for sensing temperature comprising means for converting thermal radiation to light radiation representative of said surface temperature whereby said temperature sensing means senses said light radiation.

2. Apparatus according to claim 1 wherein said sensing means comprises means for generating electrical signals representative of the temperature of said at least one roller.

3. Apparatus according to claim 2 wherein said converting means comprises a phosphor material and means for exciting said phosphor material to thereby emit visible radiation, said phosphor material being so disposed relative to said at least one roller as to receive thermal energy therefrom in accordance with the temperature thereof.

4. Apparatus according to claim 3 wherein said phosphor material comprises a continuous stripe about the circumference of said at least one roller.

5. Apparatus according to claim 3 wherein said phosphor material comprises a plurality of segments extending about the circumference of said at least one roller.

6. Apparatus according to claim 3 wherein said phosphor material comprises a substrate positioned adjacent said at least one roller.

7. Apparatus according to claim 3 wherein said phosphor material comprises an electroluminescent panel positioned adjacent said at least one roller.

Claims

1. Fuser apparatus comprising: a first roller; a second roller cooperating with said first roller to form a nip through which a substrate supporting toner material is moved; means for heating at least one of said rollers to elevate the surface temperature thereof to a level sufficient to render the toner material tacky; means out of contact from said at least one of said rollers for sensing the surface temperature thereof; and means responsive to the temperature sensed for controlling said heating for maintaining the surface temperature of said at least one of said rollers constant in an area where the toner material is contacted thereby, said means for sensing temperature comprising means for converting thermal radiation to light radiation representative of said surface temperature whereby said temperature sensing means senses said light radiation.