US3735092A - Fuser control circuit for copying apparatus - Google Patents

Fuser control circuit for copying apparatus Download PDF

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Publication number
US3735092A
US3735092A US00189859A US3735092DA US3735092A US 3735092 A US3735092 A US 3735092A US 00189859 A US00189859 A US 00189859A US 3735092D A US3735092D A US 3735092DA US 3735092 A US3735092 A US 3735092A
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United States
Prior art keywords
fuser
copying apparatus
amplifier
temperature
response
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Expired - Lifetime
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US00189859A
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English (en)
Inventor
R Traister
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Xerox Corp
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Xerox Corp
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
    • G05D23/24—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor
    • 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

Definitions

  • ..H05b 1/02 rangemem includes a thermistor to sense temperature [58] Field of Search ..2l9/494, 501, 505, di i ns within the fuser, an amplifier to amplify the 219/216 thermistor signal output to a level permitting relatively inexpensive switching devices to be used directly as References Cited fuser and reproduction machine controls without the UNITED STATES PATENTS need for relatively sensitive and correspondingly expensive intermediate comparator circuitry, and 3,337,792 8/1967 Engelson ..2l9/501 switching devices for operating the fuser heat source 3,496,339 2/1970 Forms at 111m and controlling the reproduction machine in response 3,505,497 4/1970 Lawes et al ..219/216 to predetermined fuser temperature conditions.
  • This invention relates to a fuser for electrostatic type reproduction machines, and more particularly, to a fuser for electrostatic type reproduction machines incorporating improved fuser temperature controlling means.
  • a toner delineated image of the original document being copied is electrostatically formed on the copy material.
  • the image is fused by passing copy material through a heated oven, conventionally called a fuser. There, a combination of heat and pressure melts, i.e. fuses, the toner onto the copy material to form a permanent image.
  • fuser temperatures are critical. If the fuser temperature is too low, fusing may be incomplete. This is most often evidenced by smearing or' loss of image, particularly when the copy material is handled. If the fuser temperature is too high, there is danger that the copy material may burn or char.
  • a resistive type transducer normally a thermistor
  • the thermistor which is disposed in heat exchange relationship with the fuser, is circuited to provide a signal change in response to changes in fuser temperatures, this signal being relied upon to start and stop the fuser heat source as requiredto maintain desired fuser temperatures.
  • thermistor type devices suffer from the fact that their response or sensitivity to temperature change ordinarily decreases with increasing temperature. In the relatively high operating temperature range of modern fusers, thermistor sensitivity is very low. Hence, the thermistor signal output band over the fuser operating temperature range is quite small. This, in turn, has required that relatively sensitive comparator circuits be provided if accurate control over fuser temperatures are to be obtained, particularly where other machine control functions such as overtemperature shutdown protection are provided.
  • This invention relates to a copying apparatus having a fuser for fixing the toner developed images of the copying apparatus, comprising, in combination: circuit means adapted to generate a control signal proportional to temperature conditions in the apparatus fuser, the circuit means including a temperature variable resistor in heat exchange relation with the fuser, the resistive change of the resistor in response to changes in temperature in the fuser normally being relatively small within the operating temperature range of the fuser with the result that the sensitivity of the circuit means is relatively low in the fuser operating temperature range; means for amplifying the signal output of the circuit means at least in the fuser operating temperature range whereby to avoid the need for relatively sensitive output comparator circuitry and instead permit use of relatively simple switching means; means for heating the fuser; and switching means for controlling the fuser heating means, the switching means being adapted to render the fuser heating means inoperative in response to a first amplifier means signal reflecting attainment of normal operating temperature in the fuser.
  • FIG. 1 is a schematic sectional view of an electrostatic type reproduction machine embodying the principles of the present invention
  • FIG. 2 is an enlarged cross sectional view showing the fusing apparatus of the reproduction machine shown in FIG. 1;
  • FIG. 3 is a plot of the temperature versus resistance relationship for a typical thermistor
  • FIG. 4 isa plot of the temperature versus output signal relationship for the thermistor of FIG. 3 with unamplified thermistor signal output shown in dotted lines and amplified thermistor signal output shown in solid lines;
  • FIG. 5 is a schematic circuit representation of the fuser control arrangement of the present invention.
  • an exemplary copier/reproduction machine designated generally by the numeral 10 and incorporating the fuser control arrangement of the present invention
  • a light image of a document to be reproduced is projected onto the sensitized surface of a xerographic plate to form an electrostatic latent image thereon.
  • the latent image is developed with an oppositely charged developing material to form a xerographic powder or toner image, corresponding to the latent image on the plate surface.
  • the toner image is then electrostatically transferred to a support surface where it is fused by a fusing device so that the toner image is permanently adhered to the support surface.
  • an original document 12 to be copied is placed upon a transparent support platen 14 fixedly arranged in an illumination assembly generally indicated by the reference numeral 15 and disposed at the left end of the machine. While upon the platen, the document 12 is illuminated, thereby producing image rays corresponding to the informational areas on the original. The image rays are projected by means of an optical system onto the photosensitive surface of a xerographic plate.
  • the xerographic plate is in the form of a flexible photoconductive belt 17 supported in a belt assembly 18.
  • the support assembly 18 for photoconductive belt 17 includes three rollers 20, 21 and 22 located with parallel axes at approximately the apices of a triangle.
  • the upper roller 22 is rotatably supported on shaft 23 which in turn is rotatably driven by a suitable motor and drive means (not shown) to drive belt 17 in the direction shown by the arrow in FIG. 1.
  • a suitable motor and drive means not shown to drive belt 17 in the direction shown by the arrow in FIG. 1.
  • photoconductive belt 17 carries the electrostatic image through a developing station 26 in which there is positioned a developer assembly generally indicated by the reference numeral 28. There the latent electrostatic image is developed by means of toner through the use of a multiple magnetic brush system 29.
  • the developed electrostatic image is carried by belt 17 to the transfer station 30 where the developed image is transferred to a support surface, normally a sheet of copy paper 31, brought forward between transfer roller 32 and belt 17.
  • a support surface normally a sheet of copy paper 31, brought forward between transfer roller 32 and belt 17.
  • the copy sheet 31 is moved at substantially the same speed as belt 17.
  • a sheet transport mechanism generally indicated at 34 is provided to advance copy sheets 31 from a paper handling mechanism generally indicated by the reference numeral 35 to transfer station 30.
  • the copy sheet 31 is stripped from belt 17 and conveyed through fuser 38 wherein the toner image is permanently fused or affixed thereto. Following fusing, the finished copy is discharged into output tray 39.
  • Photoconductive belt 17 comprises a photoconductive layer of selenium, which is the light receiving surface and imaging medium for the apparatus, on a conductive backing. Further details regarding the structure of the belt assembly 12 and its relationship with the machine and support therefor may be found in the copending application Ser. No. 102,312, filed Dec. 29, 1970, and assigned to the same assignee.
  • fuser 38 includes a suitable housing 40 within which is disposed a lower heated fuser roll 41 and an upper pressure roll 42, rolls 41, 42 cooperating to form a nip through which the copy sheets 31 pass.
  • Rolls 41, 42 are suitably supported for rotation and driven in unison by a suitable drive means (not shown).
  • Pressure roll 42 is comprised of a relatively soft material such as Teflon, Neoprene, and the like with the result that pressure contact between the rolls 41, 42 deforms the surface of pressure roll 42. In this way, an increased contact arc between the copy sheet and the heated fuser roll 41 is obtained.
  • fuser roll 41 is hollow, the roll 41 being formed from a suitable heat conductive material.
  • a source of heat such as lamp 44 is disposed therewithin.
  • a suitable temperature variable resistor, i.e. thermistor 45 is supported on a fuser housing 40 in heat exchange relation therewith to sense temperature conditions within the fuser housing 40.
  • the signal output of thermistor 45 across the operating temperature range of fuser 38 is amplified. This in turn enables relatively simple and inexpensive switches 55, 56, 57 to be used as control devices instead.
  • the signal output of thermistor 45 is fed to a suitable operational amplifier 50.
  • Amplifier S0 is gated to amplify thermistor signals equal to or less than v by means of a suitable source 51 of dc. voltage.
  • the signal amplification accordingly takes place at fuser temperatures equal to or above minimum fuser operating temperature T,.
  • the amplified signal from amplifier 50 is impressed on the control gate of switching amplifiers 55, 56, 57. As will appear, switching amplifiers 55, 56, 57 control fuser heating and operation of copying machine 10.
  • the switching amplifiers 55, 56, 57 are each biased to a suitable control level by voltage source 51, various resistor combinations 58, 59 being provided to obtain the different individual switching responses from each of the switching amplifiers 55, 56, 57 as required to provide the requisite copying machine control.
  • Switching amplifier 55 controls operation of fuser heating lamp 44.
  • the fuser lamp control consists of switch 60 in the power line to lamp 44 with the switch operating coil 60' in series with the output gate of amplifier 55. On triggering of switching amplifier 55 to a conducting state, coil 60 is energized to close switch 60 and complete the energizing circuit to fuser heat lamp 44.
  • Switching amplifiers 56, 57 control operation of copying machine 10, amplifier 56 serving to prevent operation of copying machine on start-up until temperatures of fuser 38 reach a predetermined level.
  • a switch '63 is provided in the copying machine operating circuit, the operating coil 63 therefor being in series relationship with the output gate of amplifier 56. Switch 63 prevents or inhibits operation of the copying machine 10 until closed by coil 63' upon energization thereof through triggering of amplifier 56 to a conducting state.
  • Switching amplifier 57 serves to shut down copy machine 10 should fuser temperatures become too high as represented by temperature T of FIGS. 3 and 4.
  • the output gate of amplifier 57 is series connected with the operating coil 67 for normally closed switch 67 in the operating circuit of copying machine 10.
  • coil 67' opens switch 67 to shut down copying machine 10.
  • the temperature of fuser 38 may be below minimum fuser operating temperature T This normally occurs when copying machine 10 is unused for a relatively long period or on first start-up following an overnight shutdown.
  • resistance of thermistor 45 is relatively high so that the signal output of thermistor 45 to amplifier 50 is relatively high. Since the thermistor signal output is greater than v the voltage for which amplifier 50 is gated to conduct, amplifier 50 is held in a non-conducting condition. Since switching amplifiers 55, 56, 57 are set to respond to predetermined signal inputs from amplifier 50, amplifiers 55, 56, 57 remain in their quiescent state.
  • switching amplifier 55 is in a conducting state while amplifiers 56, 57 are in a blocking state.
  • the signal from amplifier 55 energizes coil 60' to close switch 60 and energize fuser heating lamp 44. Lamp 44, in turn, heats fuser roll 41.
  • Switch 63 which is closed only on triggering of switching amplifier 56, is open thereby preventing operation of copying machine 10. With amplifier 57 in a blocking condition, switch 67 is closed.
  • the resistor combination 58, 59 for switching amplifier 56 is chosen so that the amplified signal V, from amplifier 50, representing attainment of the minimum operating temperature T, in fuser 38, switches amplifier 56 to a conducting state. With switching of amplifier to a conducting state, relay coil 63 is energized to close switch 63 and enable operation of copying machine 10.
  • Fuser lamp 44 continues to heat fuser 38, the rise in fuser temperature being accompanied by a continued decrease in resistance of thermistor 45 and hence a decrease in the amplified signal output from amplifier 50.
  • the signal output V from amplifier 50 switches switching amplifier 55 to a non-conducting state.
  • the resultant deenergization of relay coil 60 opens switch 60 to interrupt power to fuser lamp 44 and terminate heating of fuser 38.
  • a second control gate circuit to amplifier 50 incorporating transistor 70 is provided.
  • the base of transistor 70 is connected through adjustable resistor 71 to the output side of thermistor 45 while the emitter of transistor 70 is connected with a control gate of amplifier 70.
  • transistor 70 is conductive to provide a gate signal to amplifier 70.
  • transistor 70 is switched to a non-conducting state. This in turn causes the output voltage of amplifier 50 to drop to a low level.
  • the low level output from amplifier 50 on such failure or malfunction of thermistor 45 which is below the triggering signal V of switching amplifier 57, triggers amplifier 57 to a conducting state thereby energizing relay coil 67' and opening switch 67. Opening of switch 67 shuts down the copying machine 10 as described heretofore.
  • a suitable delay circuit 72 is provided to prevent premature triggering of switching amplifier 57 when fuser 38 is first warmed up.
  • switch 67 may comprise a manually resettable type switch requiring, once opened, manual reclosing before operation of copying machine 10 can be resumed.
  • triggering of switching amplifier 57 may also serve to actuate an alarm or signal to alert the operator to the fuser over-temperature condition.
  • circuit means for generating a control signal proportional to temperature conditions in said fuser, said circuit means including a temperature variable resistor in heat exchange relation with said fuser, the resistive change of said resistor in response to changes in temperature in said fuser normally being relatively small within the operating temperature range of said fuser whereby the sensitivity of said circuit means is relatively low in said fuser operating temperature range;
  • control means for said copying apparatus said control means including switching means operative to prevent actuation of said copying apparatus while temperature of said fuser is below a predetermined minimum, said switching means being operative on a preset signal from said amplifier means reflecting attainment of said predetermined minimum fuser temperature to enable operation of said copying apparatus.
  • the copying apparatus including means for monitoring operation of said temperature variable resistor operative on failure of said resistor to abort said amplifying means to generate said second preset signal whereby said second switching means shuts down said copying apparatus.
  • circuit means for generating a control signal proportional to temperature conditions in said fuser, said circuit means including a temperature variable resistor in heat exchange relation with said fuser, the resistive change of said resistor in response to changes in temperature in said fuser normally being relatively small within the operating temperature range of said fuser whereby the sensitivity of said circuit means is relatively low in said fuser operating temperature range;
  • switching means for controlling said fuser heating means, said switching means rendering said fuser heating means inoperative in response to a first amplifier means signal reflecting attainment of normal operating temperature in said fuser;
  • said amplifying means comprising a variable voltage amplifier gated to operate in response to a preset unamplified control signal from said circuit means reflecting attainment of minimum operating temperature in said fuser so that at fuser temperatures below said minimum operating temperature, said amplifier assumes a signal blocking condition.
  • circuit means for generating a control signal proportional to temperature conditions of said fuser, said circuit means including a temperature variable resistor in heat exchange relation with said fuser; means for heating said fuser;
  • the copying apparatus including means to delay response of said resistor monitoring means whereby to avoid premature response of said resistor monitoring means and shut down of said fuser heating means.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Fixing For Electrophotography (AREA)
  • Control Of Temperature (AREA)
US00189859A 1971-10-18 1971-10-18 Fuser control circuit for copying apparatus Expired - Lifetime US3735092A (en)

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US18985971A 1971-10-18 1971-10-18

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US (1) US3735092A (en, 2012)
JP (1) JPS5412060B2 (en, 2012)
CA (1) CA991254A (en, 2012)
GB (1) GB1406655A (en, 2012)
NL (1) NL161273C (en, 2012)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3804516A (en) * 1972-12-11 1974-04-16 Xerox Corp Fire detecting device for a photographic printing machine
US3849628A (en) * 1973-07-25 1974-11-19 Xerox Corp Non-contact temperature sensor for a roll fuser of a xerographic reproduction apparatus
US3866587A (en) * 1972-05-17 1975-02-18 Bosch Gmbh Robert Automotive fuel heating control system
US4006985A (en) * 1975-09-05 1977-02-08 Xerox Corporation Xerographic apparatus having time controlled fusing
US4046990A (en) * 1975-04-07 1977-09-06 Eastman Kodak Company Temperature sensing and control of a fusing roll
DE2608295A1 (de) * 1976-02-28 1977-09-08 Bbc Brown Boveri & Cie Elektronischer temperaturregler ueber die energiezufuhr fuer ein elektrisches heizelement
DE2717265A1 (de) * 1976-04-19 1977-11-10 Canon Kk Fixiervorrichtung eines elektrofotografischen kopiergeraets
DE3018859A1 (de) * 1979-05-17 1980-11-20 Canon Kk Bilderzeugungsgeraet
US4372675A (en) * 1980-11-28 1983-02-08 Xerox Corporation Variable power fuser control
EP0070740A3 (en) * 1981-07-21 1983-05-18 Mita Industrial Co. Ltd. Fixing and heating device for an electrostatic copying apparatus
US6188854B1 (en) * 1999-11-09 2001-02-13 Tommy C. Coleman Non-contact thermal temperature controller
US6359266B2 (en) * 1999-08-16 2002-03-19 Xerox Corporation Flicker free fuser control
US20050084276A1 (en) * 2003-10-20 2005-04-21 Mark Hirst Indicating system

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54111081A (en) * 1978-02-21 1979-08-31 Taiyou Tomuko Kk Overheating prevention circuit
JPS55164867A (en) * 1979-06-08 1980-12-22 Canon Inc Temperature control unit
JPS59214068A (ja) * 1983-05-19 1984-12-03 Fuji Xerox Co Ltd 電子複写機の定着装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3337792A (en) * 1963-07-09 1967-08-22 Loral Electronics Corp Firing angle control circuit for silicon controlled rectifiers
US3496339A (en) * 1966-04-23 1970-02-17 Dunlop Co Ltd Electrical heating systems
US3505497A (en) * 1966-04-28 1970-04-07 Arlside Ltd Reprographic apparatus heater unit control

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3337792A (en) * 1963-07-09 1967-08-22 Loral Electronics Corp Firing angle control circuit for silicon controlled rectifiers
US3496339A (en) * 1966-04-23 1970-02-17 Dunlop Co Ltd Electrical heating systems
US3505497A (en) * 1966-04-28 1970-04-07 Arlside Ltd Reprographic apparatus heater unit control

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3866587A (en) * 1972-05-17 1975-02-18 Bosch Gmbh Robert Automotive fuel heating control system
US3804516A (en) * 1972-12-11 1974-04-16 Xerox Corp Fire detecting device for a photographic printing machine
US3849628A (en) * 1973-07-25 1974-11-19 Xerox Corp Non-contact temperature sensor for a roll fuser of a xerographic reproduction apparatus
US4046990A (en) * 1975-04-07 1977-09-06 Eastman Kodak Company Temperature sensing and control of a fusing roll
US4006985A (en) * 1975-09-05 1977-02-08 Xerox Corporation Xerographic apparatus having time controlled fusing
DE2608295A1 (de) * 1976-02-28 1977-09-08 Bbc Brown Boveri & Cie Elektronischer temperaturregler ueber die energiezufuhr fuer ein elektrisches heizelement
DE2717265A1 (de) * 1976-04-19 1977-11-10 Canon Kk Fixiervorrichtung eines elektrofotografischen kopiergeraets
US4538902A (en) * 1979-05-17 1985-09-03 Canon Kabushiki Kaisha Image formation apparatus
DE3018859A1 (de) * 1979-05-17 1980-11-20 Canon Kk Bilderzeugungsgeraet
US4372675A (en) * 1980-11-28 1983-02-08 Xerox Corporation Variable power fuser control
EP0053438A3 (en) * 1980-11-28 1983-03-16 Xerox Corporation Variable power fuser control
EP0070740A3 (en) * 1981-07-21 1983-05-18 Mita Industrial Co. Ltd. Fixing and heating device for an electrostatic copying apparatus
US6359266B2 (en) * 1999-08-16 2002-03-19 Xerox Corporation Flicker free fuser control
US6188854B1 (en) * 1999-11-09 2001-02-13 Tommy C. Coleman Non-contact thermal temperature controller
US20050084276A1 (en) * 2003-10-20 2005-04-21 Mark Hirst Indicating system
US7103292B2 (en) 2003-10-20 2006-09-05 Hewlett-Packard Development Company, L.P. Heat indicating system
DE102004029083B4 (de) * 2003-10-20 2007-03-01 Hewlett-Packard Development Co., L.P., Houston Fixiereinheit mit Anzeigesystem

Also Published As

Publication number Publication date
NL161273C (nl) 1980-01-15
GB1406655A (en) 1975-09-17
CA991254A (en) 1976-06-15
NL161273B (nl) 1979-08-15
JPS5412060B2 (en, 2012) 1979-05-19
NL7213382A (en, 2012) 1972-12-27
JPS4850736A (en, 2012) 1973-07-17

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