CA1185312A - Temperature - self regulating fuser - Google Patents
Temperature - self regulating fuserInfo
- Publication number
- CA1185312A CA1185312A CA000351063A CA351063A CA1185312A CA 1185312 A CA1185312 A CA 1185312A CA 000351063 A CA000351063 A CA 000351063A CA 351063 A CA351063 A CA 351063A CA 1185312 A CA1185312 A CA 1185312A
- Authority
- CA
- Canada
- Prior art keywords
- temperature
- fuser
- roll
- curie temperature
- member according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000001105 regulatory effect Effects 0.000 title abstract description 6
- 239000000463 material Substances 0.000 claims abstract description 36
- 238000010438 heat treatment Methods 0.000 claims abstract description 33
- 229910010293 ceramic material Inorganic materials 0.000 claims abstract description 14
- 230000007704 transition Effects 0.000 claims abstract description 6
- 230000001747 exhibiting effect Effects 0.000 claims abstract description 3
- 239000002245 particle Substances 0.000 claims description 13
- 239000000919 ceramic Substances 0.000 claims description 8
- NKZSPGSOXYXWQA-UHFFFAOYSA-N dioxido(oxo)titanium;lead(2+) Chemical compound [Pb+2].[O-][Ti]([O-])=O NKZSPGSOXYXWQA-UHFFFAOYSA-N 0.000 claims description 6
- 229910002113 barium titanate Inorganic materials 0.000 claims description 5
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims description 4
- VEALVRVVWBQVSL-UHFFFAOYSA-N strontium titanate Chemical compound [Sr+2].[O-][Ti]([O-])=O VEALVRVVWBQVSL-UHFFFAOYSA-N 0.000 claims description 4
- 229910052746 lanthanum Inorganic materials 0.000 claims description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 3
- 150000001455 metallic ions Chemical class 0.000 claims 2
- 239000000203 mixture Substances 0.000 description 7
- 238000012546 transfer Methods 0.000 description 5
- 229910052788 barium Inorganic materials 0.000 description 4
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 238000004140 cleaning Methods 0.000 description 3
- 108091008695 photoreceptors Proteins 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 230000000875 corresponding effect Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000003534 oscillatory effect Effects 0.000 description 2
- -1 polytetra-fluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 229940058401 polytetrafluoroethylene Drugs 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 241001024304 Mino Species 0.000 description 1
- 229910003781 PbTiO3 Inorganic materials 0.000 description 1
- 229910001370 Se alloy Inorganic materials 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical class [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 229910010252 TiO3 Inorganic materials 0.000 description 1
- KJNGJIPPQOFCSK-UHFFFAOYSA-N [H][Sr][H] Chemical compound [H][Sr][H] KJNGJIPPQOFCSK-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/0095—Heating devices in the form of rollers
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/20—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat
- G03G15/2003—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat
- G03G15/2014—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat
- G03G15/2053—Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
- H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
- H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
- H05B3/141—Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Fixing For Electrophotography (AREA)
- Control Of Resistance Heating (AREA)
- Resistance Heating (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A heated fuser member for use in a fusing apparatus for fixing toner images to a support surface is disclosed. The fuser member includes a heating element formed of a material which heats the fuser member to the required fusing temperature, and which is temperature-self regulating. The element is formed of a semiconducting ceramic material having a positive tempera-ture coefficient of resistivity, and exhibiting a Curie temper-ature transition point at which the resistance of the material increases with increasing temperature.
A heated fuser member for use in a fusing apparatus for fixing toner images to a support surface is disclosed. The fuser member includes a heating element formed of a material which heats the fuser member to the required fusing temperature, and which is temperature-self regulating. The element is formed of a semiconducting ceramic material having a positive tempera-ture coefficient of resistivity, and exhibiting a Curie temper-ature transition point at which the resistance of the material increases with increasing temperature.
Description
S3~
, J
BACRGROUND OE T~E DISCLOSURE , I. Field of the Invention This invention relates to a heated fuser device as is com-monly used in xero~raphic copying machines, and more particularly to a heated pressure fuser device including an improved heated fuser member whose heating elements are formed of a material that enables the fuser to be temperature-self regulating.
i33L~
II. DescriDtion of the Prior Art _ . _ In a typical xerographic process a photoconductor comprising a photoconductive composition coated on a rigid or flexible sub-strate is uniformly electrostatically charged in the dark, and then exposed by being illuminated in an image pattern in accord-ance with graphic material on an original documentO The photo-conductor becomes discharged in the areas exposed to the illum-ination, but retains its electrostatic charge in the dark areas, which areas correspond to the graphic material on the original documentO The resulting elecrostatic latent image is developed by depositing on the photoconductor a finely divided electro-statically attractable developing material (toner). The toner will normally be attracted to those areas on the photoconductor which retain a charge, thereby forming a toner image correspond--ing to the electrostatic latent image. This visible image of developing material is then transferred to a support surface, such as plain paper or any other suitable substrate, to become the ultimate copy. Any residual developing material remaining on the photoconductor is cleaned and the photoconductor is reused as described above for subsequent copies. The toner image that was transferred to the plain paper is then fixed thereto. Since the developing material is heat fusible, application of sufficient heat to the paper causes the developing material to melt and be fused into the paper so as to be permanently affixed thereto.
One very basic approach to fusing in a xerographic copying machine is the use of the so-called hot roll pressure fuser appa-ratus. Typically~ in this apparatus, the paper with the toner image thereon is passed between a pair of opposed rollers, at least one of which is heated. Generally, the heated roll is
, J
BACRGROUND OE T~E DISCLOSURE , I. Field of the Invention This invention relates to a heated fuser device as is com-monly used in xero~raphic copying machines, and more particularly to a heated pressure fuser device including an improved heated fuser member whose heating elements are formed of a material that enables the fuser to be temperature-self regulating.
i33L~
II. DescriDtion of the Prior Art _ . _ In a typical xerographic process a photoconductor comprising a photoconductive composition coated on a rigid or flexible sub-strate is uniformly electrostatically charged in the dark, and then exposed by being illuminated in an image pattern in accord-ance with graphic material on an original documentO The photo-conductor becomes discharged in the areas exposed to the illum-ination, but retains its electrostatic charge in the dark areas, which areas correspond to the graphic material on the original documentO The resulting elecrostatic latent image is developed by depositing on the photoconductor a finely divided electro-statically attractable developing material (toner). The toner will normally be attracted to those areas on the photoconductor which retain a charge, thereby forming a toner image correspond--ing to the electrostatic latent image. This visible image of developing material is then transferred to a support surface, such as plain paper or any other suitable substrate, to become the ultimate copy. Any residual developing material remaining on the photoconductor is cleaned and the photoconductor is reused as described above for subsequent copies. The toner image that was transferred to the plain paper is then fixed thereto. Since the developing material is heat fusible, application of sufficient heat to the paper causes the developing material to melt and be fused into the paper so as to be permanently affixed thereto.
One very basic approach to fusing in a xerographic copying machine is the use of the so-called hot roll pressure fuser appa-ratus. Typically~ in this apparatus, the paper with the toner image thereon is passed between a pair of opposed rollers, at least one of which is heated. Generally, the heated roll is
-2 ~ I
. ~ . , \ :
. ~ . , \ :
3~ ~
., formed of a hollow cylin2er having 2 radiant heater, such as an infrared lamp or a halogen lamp~ centrally located within the cylinder to heat the roll, in series with a bimetal thermostat.
A typical example of this type of heated fuser roll i5 illustrated in U. S. Patent No. 3,637,976. ~uring operation of the fusing apparatus, the paper to which the toner images are electrostati-cally adhered is passed through the nip formed between the rolls with the toner image contacting the fuser roll to effect heating of the toner image within the nip. Fusing is enhanced by the second roll or pressure roll as it is commonly called as the result of a biasing force which forces the rolls into engagement.
The thermostat intermittently interrupts the current flow as the roll temperature reaches a predetermined value. The roll then cools to some lower temperature whereupon the thermostat restores the current, and the roll heats up again.
Many of the problems that occur with the use of a hot roll-pressure fusing apparatus are in the heated fusing roll. In par-ticular, these problems relate to the means employed for heating the fuser roll and its control. For example, in many of the ~nown hot-roll fusers it is extremely difficult to maintain a constant temperature at the nip of the rollers where the actual fusing of the toner occurs, and where temperature control is critical. Tem-perature control is difficult because (1) it is difficult to sense the temperature in this region; t2) thermal lag, i.e., the responsiveness of roll temperature under varying demands of ther-mal output; and (3) there are both different machine modes, i.e., standby, off, continuous operation, and different si~e papers to contend with. The type of thermostat control as described above 33~
is conspicuously oscillatory in nature. The thermostat, by nec-essity being situated on the circumference of the roll in order to control the temperature of that surface, is relatively remote from the heater and, thus~ the temperature fluctuations are usually significant. Reductions in this aforesaid differential temperature characteristic requires extensive and expensive proportional feed-back control means. In addition to these problems, radiant-type heated fuser rolls generally require very high heating temperatures for the heating element to enable the roll temperature in the nip of the rollers to be high enough to melt the toner. The use of these high temperatures can result in deterioration of the fuser roll.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to over~
come many of the disadvantages of the hot roll fusers described in the prior art and to provide a material for forming the heating elements for a hot roll fuser that is temperature-self regulating and will permit relatively simple control of temperature in the critical area where fusing occurs.
! It is a further object of this invention to provide a hot roll fuser which will provide a relatively even temperature gradient along its surface, avoid large temperature fluctuations, and eliminate center to edge temperature differentials.
It is a further object of the invention to avoid the use of high temperature heating elements for heating a fuser roll thereby avoiding deterioration of the fuser roll.
3~
It is still a further object of this invention to provide a hot roll fuser which eliminates the need for a heater control system.
The foregoing objec-ts and others are accomplished in accordance with the present invention by providing a heated fuser member for use in a fusing apparatus for fixing toner images to a support surface, the fuser member including a plurality of heating elements for heating the outer surface of the fuser member, each of the elements formed of a semiconducting ceramic material having a positive temperature coefficient of resistivity, the material exhibiting a Curie temperature transition point at which the resistance of the material increases with increasing temperature, the Curie temperature of the material ranging from about 150C to about 200~C, the semiconducting ceramic material including a ceramic compound capable of adjusting the Curie temperature of the semiconducting ceramic material within the temperature range for fusing the toner particles.
The present invention relates to the application of ceramic heating elements of a class known as positive temperature coefficient materials (PTC). The preferred ceraMic material is described as ferroelectric and has -the property of possessing low resistance up to some characteristic temperature known as the Curie temperature Upon attaining this temperature, the electrical resistance of the ceramic material increases typically from 50 ohms to 5000 ohms or more within a span of less than ten (10) degrees centigrade.
It is thus to be appreciated -that such a material may be configured to furnish its own thermostat, and furthermore mg/l, - 5 -53~2 since the effec-t is internal, pronounced and confined -to a narrow tempera-ture band, the oscillatory variations of temperature may be minimi~ed. Such a system has advantages over the conventional and known methods of control. The use of these ceramic materials leads to superior control, the elimination of a conventional thermostat and there-fore a more economical device. This also leads to a more relia~le device since thermostats are somewhat prone to contact failure. The self-limiting feature el.iminates temperature overshoot and promotes rapid heat up.
.,~ mg/-, - 5a -353~2 ,~.
V .
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following detailed disclosure of this invention taken in conjunc-tion with the accompanying drawings wherein:
FIG~ 1 is a schematic sectional view of a copier; and FIGSo 2-4 are sectional views illustrating alternate embodi-ments of heating elements for use within a heated fuser member as defined by the present invention DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings and particularly to FIG~ 1 thereof, there is shown an electrophotographic copying machine employing a fusïng device in which a heated fuser member in accordance with the present invention can be utilized. The var-ious processing stations shown in FIG~ 1 will be represented in part as blocks and the processing stations will only be briefly describedO The particular copying machine illustrated in FIG~ 1 i9 merely exemplary as far as the present invention is concerned for a complete understanding of an xeroqraphic process and, in particular, how a fusing apparatus is employed in such a process.
A fusing apparatus employing a heated fuser member in accordance with the present invention may be utilized in a wide variety of devices including coated paper copiers and plain paper copiers and is not necessarily limited to the particular type of copier system shown in FIGo 1~
In FIG~ 1~ the reference numeral 10 generally designates an electrophotographic copying machine which includes a rotating drum 11 having a photoconductive surface 12 secured around the .... .. ...... ... , ,, ~ ~ . . . :
outer surface of the drumO Any of numerous inorganic or organi~
photoconductive materials can be employed such as for example, a selenium alloy. Additionally, the photoconductor can be in the form of a belt instead of a drum. As drum 11 rotates in the direction of arrow 14, it passes through the various processing stations disposed around the periphery of the drum.
First, drum 11 rotates a portion of photoconductive surface 12 through a charging apparatus which includes a corona generat-ing device 15 that is positioned closely adjacent the surface of the photoconductor. Corona generating device 15 imparts a uniform electrostatic charge to photoconductor surface 12.
An image of the document to be copied is transmitted to photo-conductor surface 12 by the exposure and imaging station generally designated 16. This station could, for example, include a recipro-cating carriage that is movably mounted on top of the copying machine cabinet. The carriage would include a transparent platen on which documents are placed faced down for copying. Overlying the platen would be a movahle cover ~onnected to one side of the carriage. An operator can raise and lower the cover and thereby place on or remove documents from the platen. A series of lamps would be used to illuminate the original document. By incorporat-ing an optical system comprising mirrors and lenses a light image of the original document to be copied is projected onto the charged portion of photoconductive surface 12. The movement of the carriage and therefore the scanning of the original document is in timed relationship with the movement of rotating drum 11. Thus photo-conductive surface 12 is selectively exposed to dissipate the .,~ .
~, !
3~2~ c charge thereon and record an electrostatic latent image corres-ponding to the indicia on the original documentO
As drum 11 rotates the latent image on photoconductive surface 12 is carried past a developer station 17. The developer material used can, for example, be a two component developer which comprises carrier particles having toner particles adhering thereto.
The carrier particles are formed of a magnetic material while the toner particles are usually a heat settable plastic. ~owever, a single component toner can also be used. Preferably a magnetic brush developing unit is used in which a rotating magnetic roll 18 picks up toner from a hopper 19 to form a rotating magnetic brush, and carries that toner into contact with the latent image on photoconductive surface 120 The charged or latent image areas of the photoreceptor electrostatically attracts and holds the toner particles, thus developing the latent image~
Transfer station 20 includes a corona transfer charging appa-ratus 21. In timed relationship with the arrival of the developed image at transfer corona 21, a copy sheet also arrives at transfer station 20. The copy sheet is fed from a supply of sheets 22 stored in removable tray 23. ~ feed roller 24 feeds the uppermost copy sheet from the supply 22~ through paper guide 25 and into the nip of queuing rollers 26. At a predetermined time in the course of a copy cycle, the queuing rollers 26 are actuated to feed the copy sheet along paper guide 27 and into contact with the developed image carried on photoreceptor surface 12. By virtue of the electric charge that is generated by transfer corona 21, toner particles are attracted from photoreceptor surface 12 toward the copy sheet to which they loosely adhere. After transferring 3~L2 ~, the toner powder to the copy sheet, tbe sheet is stripped away from drum 11 by a suitable apparatus, and advanced by, belt con-veyor 28 to fixing station 29.
The copy sheet then passes into fixing station 29 which in-cludes a fusing apparatus in which the toner material now residing on the copy paper is heated to a temperature at which the toner particles melt and are thereby fused in~o the copy paper so as to form a permanent copy of the original document. An example of a fusing apparatus including a fuser member that forms the basic sub-ject matter of the present invention is illustrated in its operative position in FIG. lo As shown, the fuser apparatus includes a heated fuser member or roll 31, and a backup member or roll 32. The copy sheet with the toner powder image thereon is interposed between fuser roll 31 and backup roll 32, A release material, e.g. polytetra-fluoroethylene, can be on tbe fuser roll to prevent offset and allow for easy release of the paper from the roll. After the toner image is permanently affixed to the copy sheet, the sheet is separated from the fuser roll and advanced to a catch tray ~3 for subsequent removal from the copier by an operator.
In order to remove residual toner particles which adhere to photoconductive surface 12 after the ~ransfer of the powder image to the copy sheet, copying machine 10 is provided with a cleaning system generally designated by reference number 34. The cleaning mechanism can, for example, include a corona generating device and a brush which contacts photoconductive surface 12. First, the remaining toner particles are brought under the influence of the corona generating device to neutralize the electrostatic _g_ ~&5~2 ' charge remaining on photoconductive surfàce 12 and that of the residual toner particles. Thereafter, the neutralized particles are removed from surface 12 by the rotatably mounted brush. After the cleaning operation, a discharge lamp can be used to discharge remaining charges on surface 12 prior to the recharging thereof at corona device 15 for the next copying cycle.
Referring now to the specific subject matter of the present invention a fusing apparatus is provided with a heated fuser member such as, for example, member 31, that includes as the means for heating the member, heating elements formed of a semiconducting ceramic material which has a positive temperature coefficient of resistivity and exhibits a Curie temperature transition point at which the resistance of the material increases with increasing temperature. The preferred semiconducting ceramic materials embodied within the present invention have a Curie temperature or transition temperature such that when the material reaches its particular Curie temperature the crystalline structure changes, i.eO from the tetragonal to the cubic phase. This transition in structure is accompanied by a marked change in electrical propertiesO
In particular, the resistance of these materials increases by several powers of ten when their temperature is raised to their respective Curie temperatures. Many of these and other physical characteristics of these materials are explained in detail in Phillips Technical Review, volume 30, page 170, 1969 in an article entitled "PTC
Thermistors as Self-Regulative Heating Elements" by E. Andrich.
The positive temperature coefficient materials embodied within the present invention when employed as the heating element for a heated fuser roll, imparts to the fuser roll the ability to operat~
as a self-regulating heat source. At a given voltage the heat-ing element in the fuser will draw a high current. This is be-cause the material is cold and its resistance is low. Within a few seconds the Curie temperature of the material is reached, there is a sharp increase in resistance, e.g. from 50 ohms to 5,000 ohms, and an immediate restriction in the amount of power absorbed. Thereafter a state of equilibrium arises in which the power absorbed adjusts itself such that it is equal to the heat dicsipatedO Thus, the material tends to keep its temperature sub-stantially in the vicinity of the Curie temperature. The partic-ular ceramic material composition that is chosen for use as the heating element, of course, depends upon the fusing temperature requirements~
Of the ceramic semiconducting materials available it has been found in accordance with the present invention that ceramic semi-conductors like barium titanate or a mixture of barium titanate with strontium titanate and/or lead titanate are suited for use as heating elements for a fusing apparatus because of the Curie tem-peratures which these materials exhibit. In accordance with the present invention, ceramic semiconducting materials that exhibit Curie temperatures within the range of about 150~C to about 220rC
are the preferred materials for use as the heating elements.
By adjusting the composition of the ceramic semiconducting materials, one can either raise or lower the Curie temperature of the material, and/or also impart semiconducting properties thereto~ ~or example, by mixing barium titanate (13aTi03) with strontium titanate (SrTiO3) or with lead titanate (PbTiO3) when manufacturing the heating elements~ compositions are obtained having a wide range of Curie temperatures, and therefor a corres-pondingly wide range of positive temperature coefficient of resistivi-ty charac-teristics. De~endincJ on -the proportion oE
strontium titanate or lead titanate in -these composi-tions, the Curie -temperature is either raised or lowered. For e~ample, the Curie -temperature for barium titana-te is abou. l~0C. In the formula (Bal ySry) TiO3 as the va]ue of ~ goes from 0.1 to 0.7, the Curie tempera~ure falls from appro~ima-tely 70C to about -110~C. On the other hand considering -the ~ormula (~al XPbx) Tio3 as the value of x goes from 0.05 to 0.6, the Curie tempera-ture of the composi-tion rises from approximately 150C to ~bou-t 380C. By adding both strontiurn titanate and lead -titanate to barium titana-te, a relatively wide range of Curie temperatures can be obtained. The addition of me-tallic ions -to these ceramic materials imparts semiconduc-ting properties there-to. For example, adding small amounts of lanthanum in -the form of lanthanum titanate (LaTiO3), i.e., 0.3 mol%, is sufficien-t to impart semiconduc-tiny proper-ties to barium ti-tana-te containing stron-tium or lead titanate.
FIGS. 2-4 illus-trate some of the various ways tha-t -the ceramic semiconducting heating elements in accordance with the present invention can be employed in a heated fuser member. In FIG. 2 the heating element is in the form of a hollow cy:linder 35~ whereas in FIG.3 several wafer shaped heating elements 36 are secured -together -to form a cylinder. FIG. 4 il:lustrates the use of heating elemen-ts in the form of a plurality o~ rods 37 spaced arouncl the circumference of a core 38. Details of heated fuser members incorpora-ting the heating elemen-ts as illus-trated in FIGS. 3 & 4 are the subject of applicant's ~.S. Pa-ten-ts ~os. 4,253,007 and 4,266,115, issued February 20, 1981 and May 5, 1981, respectively.
jrc: ' - 12 ~
53~
i As an example of the temperature-self regulating properties of a heated roll according to the present invention, a roll was manufactured whose core was constructed of a plurality of 1 1/4 diameter wafer type heating elements (similar to that shown in FIG. 3) formed of barium titanateO The heating elements were contained in a sleeve of aluminum which was overcoated with a layer of a polytetra-fluoroethylene material, i.e. Teflon ~ A
str~tched rubber silicone belt was used with the heated roll instead of the standard pressure rollO Current was applied to the roll and its outer surface temperature heated to 218F.
After passing sheets of 8 1/2" by 11" paper between the fuser roll and the belt, the temperature of the outer surface of the roll was measured by a thermocouple applied to the surface of the rollO The results are shown in the att.ached table.
Roll Number of Elapsed Temperature Sheets Time (MinO) (E)~ _ .5 207 1.5 195 2.5 198 3.5 196
., formed of a hollow cylin2er having 2 radiant heater, such as an infrared lamp or a halogen lamp~ centrally located within the cylinder to heat the roll, in series with a bimetal thermostat.
A typical example of this type of heated fuser roll i5 illustrated in U. S. Patent No. 3,637,976. ~uring operation of the fusing apparatus, the paper to which the toner images are electrostati-cally adhered is passed through the nip formed between the rolls with the toner image contacting the fuser roll to effect heating of the toner image within the nip. Fusing is enhanced by the second roll or pressure roll as it is commonly called as the result of a biasing force which forces the rolls into engagement.
The thermostat intermittently interrupts the current flow as the roll temperature reaches a predetermined value. The roll then cools to some lower temperature whereupon the thermostat restores the current, and the roll heats up again.
Many of the problems that occur with the use of a hot roll-pressure fusing apparatus are in the heated fusing roll. In par-ticular, these problems relate to the means employed for heating the fuser roll and its control. For example, in many of the ~nown hot-roll fusers it is extremely difficult to maintain a constant temperature at the nip of the rollers where the actual fusing of the toner occurs, and where temperature control is critical. Tem-perature control is difficult because (1) it is difficult to sense the temperature in this region; t2) thermal lag, i.e., the responsiveness of roll temperature under varying demands of ther-mal output; and (3) there are both different machine modes, i.e., standby, off, continuous operation, and different si~e papers to contend with. The type of thermostat control as described above 33~
is conspicuously oscillatory in nature. The thermostat, by nec-essity being situated on the circumference of the roll in order to control the temperature of that surface, is relatively remote from the heater and, thus~ the temperature fluctuations are usually significant. Reductions in this aforesaid differential temperature characteristic requires extensive and expensive proportional feed-back control means. In addition to these problems, radiant-type heated fuser rolls generally require very high heating temperatures for the heating element to enable the roll temperature in the nip of the rollers to be high enough to melt the toner. The use of these high temperatures can result in deterioration of the fuser roll.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to over~
come many of the disadvantages of the hot roll fusers described in the prior art and to provide a material for forming the heating elements for a hot roll fuser that is temperature-self regulating and will permit relatively simple control of temperature in the critical area where fusing occurs.
! It is a further object of this invention to provide a hot roll fuser which will provide a relatively even temperature gradient along its surface, avoid large temperature fluctuations, and eliminate center to edge temperature differentials.
It is a further object of the invention to avoid the use of high temperature heating elements for heating a fuser roll thereby avoiding deterioration of the fuser roll.
3~
It is still a further object of this invention to provide a hot roll fuser which eliminates the need for a heater control system.
The foregoing objec-ts and others are accomplished in accordance with the present invention by providing a heated fuser member for use in a fusing apparatus for fixing toner images to a support surface, the fuser member including a plurality of heating elements for heating the outer surface of the fuser member, each of the elements formed of a semiconducting ceramic material having a positive temperature coefficient of resistivity, the material exhibiting a Curie temperature transition point at which the resistance of the material increases with increasing temperature, the Curie temperature of the material ranging from about 150C to about 200~C, the semiconducting ceramic material including a ceramic compound capable of adjusting the Curie temperature of the semiconducting ceramic material within the temperature range for fusing the toner particles.
The present invention relates to the application of ceramic heating elements of a class known as positive temperature coefficient materials (PTC). The preferred ceraMic material is described as ferroelectric and has -the property of possessing low resistance up to some characteristic temperature known as the Curie temperature Upon attaining this temperature, the electrical resistance of the ceramic material increases typically from 50 ohms to 5000 ohms or more within a span of less than ten (10) degrees centigrade.
It is thus to be appreciated -that such a material may be configured to furnish its own thermostat, and furthermore mg/l, - 5 -53~2 since the effec-t is internal, pronounced and confined -to a narrow tempera-ture band, the oscillatory variations of temperature may be minimi~ed. Such a system has advantages over the conventional and known methods of control. The use of these ceramic materials leads to superior control, the elimination of a conventional thermostat and there-fore a more economical device. This also leads to a more relia~le device since thermostats are somewhat prone to contact failure. The self-limiting feature el.iminates temperature overshoot and promotes rapid heat up.
.,~ mg/-, - 5a -353~2 ,~.
V .
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following detailed disclosure of this invention taken in conjunc-tion with the accompanying drawings wherein:
FIG~ 1 is a schematic sectional view of a copier; and FIGSo 2-4 are sectional views illustrating alternate embodi-ments of heating elements for use within a heated fuser member as defined by the present invention DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings and particularly to FIG~ 1 thereof, there is shown an electrophotographic copying machine employing a fusïng device in which a heated fuser member in accordance with the present invention can be utilized. The var-ious processing stations shown in FIG~ 1 will be represented in part as blocks and the processing stations will only be briefly describedO The particular copying machine illustrated in FIG~ 1 i9 merely exemplary as far as the present invention is concerned for a complete understanding of an xeroqraphic process and, in particular, how a fusing apparatus is employed in such a process.
A fusing apparatus employing a heated fuser member in accordance with the present invention may be utilized in a wide variety of devices including coated paper copiers and plain paper copiers and is not necessarily limited to the particular type of copier system shown in FIGo 1~
In FIG~ 1~ the reference numeral 10 generally designates an electrophotographic copying machine which includes a rotating drum 11 having a photoconductive surface 12 secured around the .... .. ...... ... , ,, ~ ~ . . . :
outer surface of the drumO Any of numerous inorganic or organi~
photoconductive materials can be employed such as for example, a selenium alloy. Additionally, the photoconductor can be in the form of a belt instead of a drum. As drum 11 rotates in the direction of arrow 14, it passes through the various processing stations disposed around the periphery of the drum.
First, drum 11 rotates a portion of photoconductive surface 12 through a charging apparatus which includes a corona generat-ing device 15 that is positioned closely adjacent the surface of the photoconductor. Corona generating device 15 imparts a uniform electrostatic charge to photoconductor surface 12.
An image of the document to be copied is transmitted to photo-conductor surface 12 by the exposure and imaging station generally designated 16. This station could, for example, include a recipro-cating carriage that is movably mounted on top of the copying machine cabinet. The carriage would include a transparent platen on which documents are placed faced down for copying. Overlying the platen would be a movahle cover ~onnected to one side of the carriage. An operator can raise and lower the cover and thereby place on or remove documents from the platen. A series of lamps would be used to illuminate the original document. By incorporat-ing an optical system comprising mirrors and lenses a light image of the original document to be copied is projected onto the charged portion of photoconductive surface 12. The movement of the carriage and therefore the scanning of the original document is in timed relationship with the movement of rotating drum 11. Thus photo-conductive surface 12 is selectively exposed to dissipate the .,~ .
~, !
3~2~ c charge thereon and record an electrostatic latent image corres-ponding to the indicia on the original documentO
As drum 11 rotates the latent image on photoconductive surface 12 is carried past a developer station 17. The developer material used can, for example, be a two component developer which comprises carrier particles having toner particles adhering thereto.
The carrier particles are formed of a magnetic material while the toner particles are usually a heat settable plastic. ~owever, a single component toner can also be used. Preferably a magnetic brush developing unit is used in which a rotating magnetic roll 18 picks up toner from a hopper 19 to form a rotating magnetic brush, and carries that toner into contact with the latent image on photoconductive surface 120 The charged or latent image areas of the photoreceptor electrostatically attracts and holds the toner particles, thus developing the latent image~
Transfer station 20 includes a corona transfer charging appa-ratus 21. In timed relationship with the arrival of the developed image at transfer corona 21, a copy sheet also arrives at transfer station 20. The copy sheet is fed from a supply of sheets 22 stored in removable tray 23. ~ feed roller 24 feeds the uppermost copy sheet from the supply 22~ through paper guide 25 and into the nip of queuing rollers 26. At a predetermined time in the course of a copy cycle, the queuing rollers 26 are actuated to feed the copy sheet along paper guide 27 and into contact with the developed image carried on photoreceptor surface 12. By virtue of the electric charge that is generated by transfer corona 21, toner particles are attracted from photoreceptor surface 12 toward the copy sheet to which they loosely adhere. After transferring 3~L2 ~, the toner powder to the copy sheet, tbe sheet is stripped away from drum 11 by a suitable apparatus, and advanced by, belt con-veyor 28 to fixing station 29.
The copy sheet then passes into fixing station 29 which in-cludes a fusing apparatus in which the toner material now residing on the copy paper is heated to a temperature at which the toner particles melt and are thereby fused in~o the copy paper so as to form a permanent copy of the original document. An example of a fusing apparatus including a fuser member that forms the basic sub-ject matter of the present invention is illustrated in its operative position in FIG. lo As shown, the fuser apparatus includes a heated fuser member or roll 31, and a backup member or roll 32. The copy sheet with the toner powder image thereon is interposed between fuser roll 31 and backup roll 32, A release material, e.g. polytetra-fluoroethylene, can be on tbe fuser roll to prevent offset and allow for easy release of the paper from the roll. After the toner image is permanently affixed to the copy sheet, the sheet is separated from the fuser roll and advanced to a catch tray ~3 for subsequent removal from the copier by an operator.
In order to remove residual toner particles which adhere to photoconductive surface 12 after the ~ransfer of the powder image to the copy sheet, copying machine 10 is provided with a cleaning system generally designated by reference number 34. The cleaning mechanism can, for example, include a corona generating device and a brush which contacts photoconductive surface 12. First, the remaining toner particles are brought under the influence of the corona generating device to neutralize the electrostatic _g_ ~&5~2 ' charge remaining on photoconductive surfàce 12 and that of the residual toner particles. Thereafter, the neutralized particles are removed from surface 12 by the rotatably mounted brush. After the cleaning operation, a discharge lamp can be used to discharge remaining charges on surface 12 prior to the recharging thereof at corona device 15 for the next copying cycle.
Referring now to the specific subject matter of the present invention a fusing apparatus is provided with a heated fuser member such as, for example, member 31, that includes as the means for heating the member, heating elements formed of a semiconducting ceramic material which has a positive temperature coefficient of resistivity and exhibits a Curie temperature transition point at which the resistance of the material increases with increasing temperature. The preferred semiconducting ceramic materials embodied within the present invention have a Curie temperature or transition temperature such that when the material reaches its particular Curie temperature the crystalline structure changes, i.eO from the tetragonal to the cubic phase. This transition in structure is accompanied by a marked change in electrical propertiesO
In particular, the resistance of these materials increases by several powers of ten when their temperature is raised to their respective Curie temperatures. Many of these and other physical characteristics of these materials are explained in detail in Phillips Technical Review, volume 30, page 170, 1969 in an article entitled "PTC
Thermistors as Self-Regulative Heating Elements" by E. Andrich.
The positive temperature coefficient materials embodied within the present invention when employed as the heating element for a heated fuser roll, imparts to the fuser roll the ability to operat~
as a self-regulating heat source. At a given voltage the heat-ing element in the fuser will draw a high current. This is be-cause the material is cold and its resistance is low. Within a few seconds the Curie temperature of the material is reached, there is a sharp increase in resistance, e.g. from 50 ohms to 5,000 ohms, and an immediate restriction in the amount of power absorbed. Thereafter a state of equilibrium arises in which the power absorbed adjusts itself such that it is equal to the heat dicsipatedO Thus, the material tends to keep its temperature sub-stantially in the vicinity of the Curie temperature. The partic-ular ceramic material composition that is chosen for use as the heating element, of course, depends upon the fusing temperature requirements~
Of the ceramic semiconducting materials available it has been found in accordance with the present invention that ceramic semi-conductors like barium titanate or a mixture of barium titanate with strontium titanate and/or lead titanate are suited for use as heating elements for a fusing apparatus because of the Curie tem-peratures which these materials exhibit. In accordance with the present invention, ceramic semiconducting materials that exhibit Curie temperatures within the range of about 150~C to about 220rC
are the preferred materials for use as the heating elements.
By adjusting the composition of the ceramic semiconducting materials, one can either raise or lower the Curie temperature of the material, and/or also impart semiconducting properties thereto~ ~or example, by mixing barium titanate (13aTi03) with strontium titanate (SrTiO3) or with lead titanate (PbTiO3) when manufacturing the heating elements~ compositions are obtained having a wide range of Curie temperatures, and therefor a corres-pondingly wide range of positive temperature coefficient of resistivi-ty charac-teristics. De~endincJ on -the proportion oE
strontium titanate or lead titanate in -these composi-tions, the Curie -temperature is either raised or lowered. For e~ample, the Curie -temperature for barium titana-te is abou. l~0C. In the formula (Bal ySry) TiO3 as the va]ue of ~ goes from 0.1 to 0.7, the Curie tempera~ure falls from appro~ima-tely 70C to about -110~C. On the other hand considering -the ~ormula (~al XPbx) Tio3 as the value of x goes from 0.05 to 0.6, the Curie tempera-ture of the composi-tion rises from approximately 150C to ~bou-t 380C. By adding both strontiurn titanate and lead -titanate to barium titana-te, a relatively wide range of Curie temperatures can be obtained. The addition of me-tallic ions -to these ceramic materials imparts semiconduc-ting properties there-to. For example, adding small amounts of lanthanum in -the form of lanthanum titanate (LaTiO3), i.e., 0.3 mol%, is sufficien-t to impart semiconduc-tiny proper-ties to barium ti-tana-te containing stron-tium or lead titanate.
FIGS. 2-4 illus-trate some of the various ways tha-t -the ceramic semiconducting heating elements in accordance with the present invention can be employed in a heated fuser member. In FIG. 2 the heating element is in the form of a hollow cy:linder 35~ whereas in FIG.3 several wafer shaped heating elements 36 are secured -together -to form a cylinder. FIG. 4 il:lustrates the use of heating elemen-ts in the form of a plurality o~ rods 37 spaced arouncl the circumference of a core 38. Details of heated fuser members incorpora-ting the heating elemen-ts as illus-trated in FIGS. 3 & 4 are the subject of applicant's ~.S. Pa-ten-ts ~os. 4,253,007 and 4,266,115, issued February 20, 1981 and May 5, 1981, respectively.
jrc: ' - 12 ~
53~
i As an example of the temperature-self regulating properties of a heated roll according to the present invention, a roll was manufactured whose core was constructed of a plurality of 1 1/4 diameter wafer type heating elements (similar to that shown in FIG. 3) formed of barium titanateO The heating elements were contained in a sleeve of aluminum which was overcoated with a layer of a polytetra-fluoroethylene material, i.e. Teflon ~ A
str~tched rubber silicone belt was used with the heated roll instead of the standard pressure rollO Current was applied to the roll and its outer surface temperature heated to 218F.
After passing sheets of 8 1/2" by 11" paper between the fuser roll and the belt, the temperature of the outer surface of the roll was measured by a thermocouple applied to the surface of the rollO The results are shown in the att.ached table.
Roll Number of Elapsed Temperature Sheets Time (MinO) (E)~ _ .5 207 1.5 195 2.5 198 3.5 196
4.0 195 Although a slight amount of cooling of the fuser roll occurred due to the effect of the initial sheets of paper passing through the heated roll~ the barium titanate heating elements regulated the temperature of the roll to a relatively even temperature gradient and avoided any large temperature fluctuations.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A heated fuser member for use in a fusing apparatus for fixing toner images to a support surface, said fuser member including a plurality of heating elements for heating the outer surface of the fuser member, each of said elements formed of a semiconducting ceramic material having a positive temperature coefficient of resistivity, said material exhibiting a Curie temperature transition point at which the resistance of said material increases with increasing temperature, said Curie temperature of the material ranging from about 150°C to about 200°C, said semiconducting ceramic material including a ceramic compound capable of adjusting the Curie temperature of said semi-conducting ceramic material within said temperature range for fusing the toner particles.
2. A member according to claim 1 wherein said material includes barium titanate and metallic ions.
3. A member according to claim 2 wherein said metallic ion is lanthanum.
4. A member according to claim 2 wherein said Curie temperature adjusting compound comprises strontium titanate.
5. A member according to claim 1 wherein said heating element is a roll structure.
6. A member according to claim 2 wherein said Curie temperature adjusting compound comprises lead titanate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US4102479A | 1979-05-21 | 1979-05-21 | |
| US041024 | 1979-05-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1185312A true CA1185312A (en) | 1985-04-09 |
Family
ID=21914302
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000351063A Expired CA1185312A (en) | 1979-05-21 | 1980-05-01 | Temperature - self regulating fuser |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0019491A1 (en) |
| JP (1) | JPS5622459A (en) |
| CA (1) | CA1185312A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60131784A (en) * | 1983-12-19 | 1985-07-13 | キヤノン株式会社 | Heat roller |
| JPS61145574A (en) * | 1984-12-19 | 1986-07-03 | Nitto Kogyo Kk | Fixing roller of electronic copying machine or the like |
| KR960008921B1 (en) * | 1991-08-08 | 1996-07-09 | Tech K K | Fixing apparatus |
| US5245392A (en) * | 1992-10-02 | 1993-09-14 | Xerox Corporation | Donor roll for scavengeless development in a xerographic apparatus |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3610888A (en) * | 1970-01-30 | 1971-10-05 | Westinghouse Electric Corp | Oxide resistor heating element |
| US3748439A (en) * | 1971-12-27 | 1973-07-24 | Texas Instruments Inc | Heating apparatus |
| NL166808C (en) * | 1973-07-25 | 1981-09-15 | Hoechst Ag | CONTACT FIXING DEVICE. |
| CH597681A5 (en) * | 1975-09-05 | 1978-04-14 | Sulzer Ag | |
| JPS5553100Y2 (en) * | 1975-11-07 | 1980-12-09 |
-
1980
- 1980-05-01 CA CA000351063A patent/CA1185312A/en not_active Expired
- 1980-05-20 EP EP80301676A patent/EP0019491A1/en not_active Ceased
- 1980-05-20 JP JP6703180A patent/JPS5622459A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5622459A (en) | 1981-03-03 |
| EP0019491A1 (en) | 1980-11-26 |
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| MKEX | Expiry |