EP0372518B1 - Fixing apparatus - Google Patents

Fixing apparatus Download PDF

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Publication number
EP0372518B1
EP0372518B1 EP89122471A EP89122471A EP0372518B1 EP 0372518 B1 EP0372518 B1 EP 0372518B1 EP 89122471 A EP89122471 A EP 89122471A EP 89122471 A EP89122471 A EP 89122471A EP 0372518 B1 EP0372518 B1 EP 0372518B1
Authority
EP
European Patent Office
Prior art keywords
toner
charge
fixing
fixing roller
roller
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 - Lifetime
Application number
EP89122471A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0372518A3 (en
EP0372518A2 (en
Inventor
Koichi Okuda
Yoji Tomoyuki
Toshio Miyamoto
Junji Araya
Yukihiro Ohzeki
Masanobu Saito
Shunji Nakamura
Yasumasa Ohtsuka
Tatsunori Ishiyama
Katsuhiko Nishimura
Akira Hayakawa
Yasushi Sato
Kimio Nakahata
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
Original Assignee
Canon Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from JP63307929A external-priority patent/JP2575093B2/ja
Priority claimed from JP1073795A external-priority patent/JP2596530B2/ja
Priority claimed from JP1285899A external-priority patent/JP2592967B2/ja
Priority claimed from JP1285900A external-priority patent/JP2592968B2/ja
Application filed by Canon Inc filed Critical Canon Inc
Publication of EP0372518A2 publication Critical patent/EP0372518A2/en
Publication of EP0372518A3 publication Critical patent/EP0372518A3/en
Application granted granted Critical
Publication of EP0372518B1 publication Critical patent/EP0372518B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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
    • 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
    • G03G15/2064—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat combined with pressure

Definitions

  • the present invention relates to a fixing apparatus used with electrophotographic systems such as a copying machine, electrophotographic printer and the like and with image forming systems such as an electrostatic recording apparatus and the like, for fixing or fusing a non-fixed toner image formed on a recording sheet material, and more particularly, it relates to a fixing apparatus for fixing a non-fixed toner image onto a recording sheet material by pinching and conveying the recording sheet material bearing the non-fixed toner image thereon by means of a pair of rotary members.
  • a fixing apparatus of roller type comprising a fixing roller incorporating a heating source such as a halogen heater therein and a pressure roller urged against the fixing roller to be rotated therewith and having an outer elastic layer made of silicone rubber has generally been utilized.
  • a fixing apparatus of roller type has been commonly in practice, since it is more excellent than any other fixing apparatuses in view of reliable conveyance of a recording sheet and/or good safety against fire, which might result from the overheating of the heater.
  • the offset phenomena generated in the above-mentioned fixing apparatus can be divided into two groups, i.e., thermal offset (offset due to temperature) and electrostatic offset (offset due to electrostatics).
  • the former i.e. thermal offset
  • thermal offset includes a low temperature offset wherein the temperature of the toner in the fixing apparatus is too low to be fixed onto the recording sheet, thus causing the offset, and a high temperature offset wherein the toner temperature in the apparatus is high enough to melt the toner, thus causing the offset.
  • a temperature controlling means such as a thermistor on the basis of the feature of the developer (toner), conveying speed of the recording sheet and roller pressure.
  • the latter i.e. electrostatic offset
  • electrostatic offset may be caused by the fact that the charged toner on the recording sheet is transferred onto the fixing roller electrostatically. Since this offset phenomenon largely depends upon the kind of the recording sheet and circumferential condition, it is difficult to control the transfer of the toner (from the recording sheet to the fixing roller).
  • the disadvantage due to the electrostatic offset such as the jamming of the recording sheet which may be caused by the smudge of the recording sheet and/or fixing roller due to the offset toner has been partly eliminated by removing the offset toner transferred to the fixing roller by means of a cleaning means such as a felt pad or cleaning blade pressed against the fixing roller. Therefore, the electrostatic offset problem has not yet still been solved.
  • the fixing roller is electrically held in the floating condition, particularly in the low moisture circumstances, the fixing roller is charged to have a value of a few kV due to the friction with the recording paper, thus causing a discharging phenomenon, which may generate electric noise leading to an erroneous operation of the image forming system.
  • An object of the present invention is to provide a fixing apparatus which can avoid an electrostatic offset of toner.
  • Another object of the present invention is to provide a fixing apparatus which can prevent an excessive charging of rotary members such as a fixing roller to minimize electric noise, thus preventing an erroneous operation of an image forming system.
  • a fixing apparatus comprising a movable member used for pinching and conveying a supporting material bearing a non-fixed toner image thereon, thereby fixing, in use, the non-fixed toner image on said supporting material; the fixing apparatus being characterized by further comprising a rectifier element connected between said movable member and an earth, said rectifier element being so connected that said movable member holds a charge to prevent, in use, a toner offset.
  • the fixing apparatus F comprises a pair of movable members, i.e., a fixing roller 1 and a pressure roller 2 pressed against the fixing roller 1 and rotated together with the latter.
  • the fixing roller 1 contacts a non-fixed toner image ta formed on a recording sheet P (image bearing sheet).
  • the movable members 1,2 are embodied as rollers, the movable members 1,2 are not limited to such rollers, but may comprise endless movable members such as endless belts.
  • the upper fixing roller 1 comprises a hollow core made of aluminium, iron and the like, and a cover layer covering an outer cylindrical surface of the core and made of material having good toner-separating ability, such as PTFE, PFA or silicone.
  • a heater h such as a halogen lamp by which the fixing roller 1 is heated.
  • the lower pressure roller 2 comprises a core made of iron, stainless steel and the like. An outer cylindrical surface of the core is coated by toner-separable elastomer such as silicone rubber, fluororubber and the like.
  • the fixing roller 1 and the pressure roller 2 are urged against each other by an appropriate bias means such as a spring (not shown) and are rotated in directions shown by the arrows.
  • a temperature sensing element 3 such as a thermistor is arranged to contact the surface of the fixing roller 1, and detects the surface temperature of the fixing roller 1.
  • the energization of the heater h is controlled by a temperature adjusting circuit on the basis of the surface temperature detected by the temperature sensing element 3, whereby the surface temperature of the fixing roller 1 is automatically maintained in a predetermined fixing temperature.
  • the reference numeral 4 designates a separating pawl or claw for separating the recording sheet P from the fixing roller 1. An edge of the free end of the separating pawl 4 is pressed against the surface of the fixing roller 1 at an appropriate pressure.
  • the reference numeral 5 designates a cleaner such as a felt urged against the surface of the fixing roller 1, which cleaner 5 can sweep away the toner and/or paper powder adhered to the surface of the fixing roller 1.
  • the reference numerals 6 and 7 designate an inlet guide and an outlet guide, respectively, which can guide the recording sheet P and are attached to a frame of the fixing apparatus F.
  • a toner image formed on a surface of a photo-sensitive drum (image bearing member) is transferred onto the recording sheet P by means of a transfer charger (transfer charger means). Thereafter, the recording sheet P is conveyed or fed through the inlet guide 6 to the fixing apparatus F, wherein the recording sheet P is introduced into a nip between the fixing roller 1 and the pressure roller 2 which are pressed against each other and are rotated altogether. While passing through the nip, the non-fixed toner image ta on the recording sheet P is thermally fixed on the recording sheet P as a permanent fixed image tb by the heat from the fixing roller 1 and the pressure between the rollers 1 and 2.
  • the recording sheet P which has passed through the nip between the rollers 1, 2 and on which the images has been fixed is separated, at its leading edge, from the fixing roller 1 by means of the separating pawl 4, and then is fed to a sheet path (not shown) through the outlet guide 7. In this way, the recording sheet P is ejected onto an ejector tray.
  • offset toner transferred from the recording sheet P to the fixing roller 1 and adhered to the surface of the fixing roller 1 due to the offset phenomenon is shown as tc.
  • the present invention aims to minimize an amount of such offset toner tc.
  • Fig. 1 shows an example that the toner as the developer forming the non-fixed toner image ta on the recording sheet P to be fed to the fixing apparatus is charged negatively (minus charge), whereas, Fig. 2 shows an example that such toner is charged positively (plus charge).
  • the fixing roller 1 comprises a hollow core 1b and a toner-separable coating layer 1a surrounding an outer surface of the hollow core 1b.
  • the pressure roller 2 comprises a central core 2b and an outer elastic layer 2a.
  • the hollow core 1b of the fixing roller 1 is earthed through a diode 100 acting as a rectifier element, a connection direction of which is so selected that the fixing roller 1 can hold the electric charge having the same polarity as that of the toner, both in Fig. 1 and Fig. 2.
  • Fig. 4 shows a characteristic curve of the current and voltage of the diode 100.
  • the voltage does not increase in an area A where the diode 100 is connected in a normal direction.
  • the diode 100 in an area B where the diode 100 is connected in a reverse direction, only small current flow causes the voltage to increase up to the voltage yielding point C, and then, if a further current flows, the voltage does not increase so much.
  • the diode 100 is connected to the fixing roller 1 in the connection direction as shown in Fig. 1 and Fig. 2.
  • the potential of the fixing roller 1 is changed to have the same charge polarity as that of the toner, thus creating a repulsion force between the fixing roller 1 and the toner, whereby the offset of the toner can be reduced.
  • the fixing roller 1 in the low moisture circumstances, if the fixing roller 1 is charged by other causes than the offset of the toner, for example, if the fixing roller 1 is charged to have the charge polarity opposite to that of the toner, the fixing roller 1 becomes substantially in the earthed condition. Whereas, even if the fixing roller 1 is charged to have the same charge polarity as that of the toner, the voltage does not increase more than the voltage yielding point C (Fig. 4). Accordingly, it does not have to be feared that the fixing roller 1 is charged up excessively.
  • the electrostatic capacity of the diode 100 the more the amount of the offset toner tc could be reduced.
  • the reason may be that, for example, when the same amount of toner is offset or transferred to the fixing roller 1, the smaller the connection capacity between the fixing roller 1 and a chassis, the greater the potential fluctuation of the fixing roller 1, and thus, the greater the electric field for repulsion against the toner on the recording sheet P.
  • the electrostatic capacity of the diode 100 required to prevent the offset of the toner was preferably 100 pF or less.
  • electrostatic capacity corresponds to an electrostatic capacity when the reverse bias in an area D, i.e. the reverse bias having a value below the voltage yielding point C in the reverse direction (reverse direction voltage yielding point) is applied to the diode 100.
  • a diode 100 having the reverse direction voltage yielding point C (Fig. 4) of 50 V or more was desirable to prevent the toner offset.
  • the reason may be that, if the reverse direction yielding voltage of the diode 100 is small, when the toner is offset, since the potential of the fixing roller 1 cannot reach above the reverse direction yielding voltage, the electric field sufficient to repulse the toner on the recording sheet P cannot be obtained.
  • Fig. 5 shows an example wherein the present invention is applied to an image forming system including a transfer means comprising a transfer member such as a transfer roller 50 (transfer movable member) for transferring the non-fixed toner image ta formed on the image bearing member 10 onto the recording sheet P.
  • a transfer means comprising a transfer member such as a transfer roller 50 (transfer movable member) for transferring the non-fixed toner image ta formed on the image bearing member 10 onto the recording sheet P.
  • the transfer roller 50 acting as the transfer member comprises a metallic core 50b made of iron, stainless steel and the like and an outer conductive elastomer layer 50a.
  • the transfer roller 50 is subjected to a bias voltage from an appropriate power source (not shown).
  • an appropriate power source not shown.
  • the transfer roller 50 can apply the bias voltage to the recording sheet P by directly contacting the latter, it has an advantage that the erroneous or poor transfer does not occur even in the high moisture circumstances.
  • the conventional fixing apparatus including the fixing roller 1 had a disadvantage that, in the high moisture circumstances, the transferring current flows to the fixing roller 1 through the transfer paper (recording sheet) P which is wet to reduce its resistance, whereby the surface of the fixing roller 1 is charged to have the same polarity as that of the transfer roller 50, thus attracting the toner toward the fixing roller 1 to offset the toner.
  • the embodiment shown in Fig. 5 aims to eliminate such disadvantage.
  • This example shows the case wherein the toner has the negative polarity.
  • This embodiment is realized to reduce the electrostatic offset which may be caused by the fact that the transferring charge applied to the back of the recording sheet P and having the charge polarity opposite to that of the toner leaks through the pressure roller 2.
  • Fig. 6 is a sectional view showing a main portion of the image forming system incorporating a fixing apparatus according to the second embodiment.
  • a fixing roller 1 comprises a hollow metallic core made of aluminium, iron and the like, an outer surface of which is coated by good toner-separable material or tube such as PTFE, PFA or silicone rubber, and a heating source such as a harogen lamp arranged within the core.
  • the outer surface of the fixing roller 1 is maintained to a given temperature by means of an appropriate temperature controlling means (not shown).
  • a pressure roller 2 pressed against the fixing roller 1 and driven by the rotation of the fixing roller 1 comprises a central metallic core made of iron, stainless steel and the like, and an outer elastic layer made of silicone rubber of fluororubber.
  • the core of the pressure roller 2 is connected to GND (earth) through a diode 101 acting as a rectifier element in such a manner that the electric charge having the charge polarity opposite to that of the non-fixed toner image ta is held on the pressure roller 2; whereas, the core of the fixing roller 1 is also connected to GND through a diode 102 acting as a rectifier element in such a manner that the electric charge having the same charge polarity as that of the non-fixed toner image ta is held on the fixing roller 1.
  • GND earth
  • a diode 101 acting as a rectifier element
  • a latent image is formed on a photosensitive drum 10 acting as an image bearing member, by the charge from a charger 11 and the illumination 11 of light information according to image information.
  • the latent image is developed by the developer (toner) in a developing device 13 to form a toner image.
  • the reference numeral 14 designates a cleaner for cleaning the photosensitive drum 10.
  • the toner image formed on the surface of the photosensitive drum 10 is transferred onto the recording sheet P by applying the charge having the charge polarity (in this case, positive or plus polarity) opposite to that of the toner to the back of the recording sheet P by means of a transfer charger means 15.
  • the recording sheet P on which the toner image has been transferred is introduced into the nip between the fixing roller 1 and the pressure roller 2, where the toner image is thermally fixed onto the recording sheet P.
  • the non-fixed toner image ta transferred from the image bearing member 10 to the recording sheet P by means of the transfer charger means 15 is strongly held on the recording sheet P by the charge of the toner and the transferring charge having the polarity opposite to that of the toner and applied to the back of the recording sheet P.
  • the electrostatic toner offset was caused by the fact that the transferring charge having the charge polarity opposite to that of the toner and applied to the back of the recording sheet P to electrostatically hold the toner on the recording sheet P leaks in the fixing apparatus through the pressure roller 2 contacting with the back of the recording sheet P.
  • the electrostatic offset occurs noticeably in the case where a recording sheet P such as an OHP transparent film of sandwich structure obtained by coating middle-resistive material having a surface resistance of about 109 - 1012 ⁇ on both surfaces of dielectric film which has been widely utilized is used, rather than a plain paper.
  • a recording sheet P such as an OHP transparent film of sandwich structure obtained by coating middle-resistive material having a surface resistance of about 109 - 1012 ⁇ on both surfaces of dielectric film which has been widely utilized is used, rather than a plain paper.
  • the reverse charge - Q′ depending upon the transferring charge + Q applied in the transfer charging process is applied to a recording surface (surface on which the toner image is transferred) of the OHP film by the separating discharge.
  • the reverse charge Q′ was about 50 to 90% of the transferring charge Q. Accordingly, it is considered that, if the transferring charge leaks through the pressure roller 2, since the separating charge remains on the recording surface of the OHP film, the electrostatic force for holding the toner is reduced quickly, thus causing the toner offset.
  • the resistance of the pressure roller 2 was obtained in such a manner that a metallic roller made of stainless steel was pressed against the fixing roller 1 to create the nip of about 2 - 3 mm and the resistance between the core of the pressure roller 2 and the metallic roller was measured by a resistance meter. Further, the fixing roller 1 was formed from a cylindrical body made of aluminium and coated by an insulating PFA tube having a thickness of about 30 ⁇ m therearound.
  • the transferring charge ⁇ on the back of the recording sheet P is beginning to flow as the leak current I P to the GND through the pressure roller 2.
  • the leak current increases.
  • the charge ⁇ having the same polarity as that of the toner and being applied to the recording surface of the OHP sheet loses its holding force, and, thus, the charge ⁇ is beginning to leak onto the surface of the fixing roller 1, whereby the current I F flowing from the GND to the core of the fixing roller 1 can be measured. If the resistance of the pressure roller 2 decreases below 1012 ⁇ , the amount of the toner offset decreases more and more. On the other hand, if the resistance of the pressure roller 2 is above 1013 ⁇ , the leak current I P cannot be measured, but the toner offset does not cease.
  • the pressure roller 2 having the resistance of 1012 ⁇ or less.
  • the diode 102 acting as the rectifier element is interposed between the fixing roller 1 and the earth in such a manner that a charge having the same charge polarity as that of the toner is maintained, and the diode 101 acting as the rectifier element is interposed between the pressure roller 2 and the earth in such a manner that a charge having the charge polarity opposite to that of the toner is maintained.
  • Table 2 shows the leak current while passing through the OHP sheet, offset, potential of the core of the fixing roller 1, and potential of the core of the pressure roller 2, when diodes 101, 102 having the yielding voltage of 1 kV are used in this embodiment.
  • the fixing roller 1 having a diameter of 20 mm and made of an aluminium tube coated by a PFA tube having a thickness of 30 ⁇ m was used.
  • the transferring current of 1.5 ⁇ A was applied to the OHP sheet moving at a speed of 24 mm/sec.
  • a diode having a voltage yielding point C of 3 kV or less, preferably 2 kV or less.
  • Fig. 8 is a sectional view of a fixing apparatus according to an alteration of the aforementioned embodiment.
  • a charge removing brush 16 contacting the back of the recording sheet P and connected to the GND is arranged at an outlet of the fixing apparatus.
  • the pressure roller 2 was the resistance of 1010 - 1012 ⁇ , as in the previous embodiment.
  • the current of 100 - 200 nA flows through the charge removing brush 16 in a direction from the OHP sheet to the GND, thus removing the charge.
  • the holding force given by the electrostatic force of the charge having the same polarity as that of the toner remaining on the recording surface of the OHP sheet decreases quickly.
  • the current of 10 - 20 nA flowed in a direction from the GND to the core of the fixing roller 1, and, thus, the toner offset occured.
  • the diode 102 is interposed between the fixing roller 1 and the GND, such current does not flow, but the potential of the core of the fixing roller 1 1 is increased up to about - 600 V, whereby the non-fixed toner image ta having a charge ⁇ on the OHP sheet is subjected to the electrostatic force directing toward the back of the OHP sheet, thus preventing the occurrence of the toner offset.
  • the diodes may be connected in reverse directions opposite to those in the aforementioned embodiment. Also in this case, the same technical effect can be obtained.
  • This embodiment is realized to minimize the electrostatic offset which may be caused when the roller surface is charged by the friction charge between the roller and the recording sheet P.
  • a fixing roller 1 comprises a hollow metallic core 1b made of aluminium, iron and the like, an outer surface of which is coated by a toner separable and heat-durable resin layer 1a made of PTFE or PFA.
  • a pressure roller 2 urged against the fixing roller 1 comprises a central metallic core 2b made of iron, stainless steel and the like, and an outer toner-separable elastic layer 2a made of silicone rubber, fluororubber and the like.
  • the core 1b of the fixing roller 1 is electrically connected to the core 2b of the pressure roller 2, and these cores are connected to the earth through a rectifier element 103 in a normal connection direction.
  • the toner having the minus charge is used was explained, as to the toner having the plus charge, as shown in Fig. 11, only the connection direction of the rectifier element 103 may be reversed.
  • the rectifier element 103 By connecting the rectifier element 103 in the reverse direction, the minus charge stored in the pressure roller 2 escapes to the ground; whereas, the outer surface 1a of the fixing roller 1 is charged to the plus charge. Accordingly, the repulsion force is generated between the toner and the fixing roller 1, thus preventing the toner offset.
  • test conditions were as follows.
  • the fixing roller 1 comprising the core 1b having an outer diameter of 20 mm and a wall thickness of 2 mm and coated by the resin tube layer 1a made of PFA and having a thickness of 30 microns, and the pressure roller 2 comprising the core 2b having an outer diameter of 10 mm and the outer elastic layer 2a made of LTV silicone rubber and having a wall thickness of 3 mm were used.
  • Coating lengths (longitudinal lengths) of the PFA resin layer and silicone rubber layer were 226 mm and 222 mm, respectively.
  • the cores of these two rollers were electrically connected to each other and were also connected to the earth through a diode DSA-1A4 manufactured by HITACHI SEISAKUSHO Co., Ltd. (Japan), as shown in Fig. 10.
  • rollers were urged against each other to form a nip having a width (length in a circumferential direction) of 2 mm and the OHP sheet was passed through the nip.
  • the toner having the minus charge was used.
  • the surface of the pressure roller 2 was frictionally charged to - 2000 V, and this charge was supplied to the core 1b of the fixing roller 1 to charge the core 1b to have a value of - 750 V, with the result that the surface of the fixing roller 1 was charged to - 250 V to generate the repulsion force between the toner and the fixing roller 1, whereby the toner offset was prevented.
  • the rectifier element 103 which was used here has the yielding voltage of 50 V to 500 V, because if the yielding voltage of the rectifier element 103 is below 50 V it is impossible to apply the adequate charge to the fixing roller 1 and to maintain such charge in the fixing roller 1, whereas if the yielding voltage is above 500 V the discharge will be generated in the low moisture circumstances, thus creating the electric noise which leads to the erroneous operation of the image forming system.
  • Fig. 12 shows a fixing apparatus used with the toner having the minus charge polarity.
  • the fixing roller 1 is connected to the pressure roller 2 through a rectifier element 104 so that the fixing roller 1 is connected in the normal direction with respect to the pressure roller 2, the core 1b of the fixing roller 1 is charged to the minus charge more strongly.
  • the potentials of the cores of the fixing roller 1 and the pressure roller 2 were compared between the apparatuses shown in Figs. 10 and 12 using the same roller pair as shown in the aforementioned test.
  • the potentials of the cores 1b, 2b of two rollers were the same and had a value of - 750 V.
  • the potential of the core lb of the fixing roller 1 was - 950 V
  • the potential of the core 2b of the pressure roller 2 was - 650 V.
  • Fig. 13 shows a fixing apparatus used with the toner having the plus charge polarity.
  • the rectifier element 104 is connected so that the plus charge can be easily stored in the core 1b of the fixing roller 1. Also in the embodiment shown in Fig. 13, the same technical effect as mentioned above was obtained.
  • the material of the surface 1a of the fixing roller 1 was fluororesin such as PFA and the material of the surface 2a of the pressure roller 2 was silicone rubber
  • the material of the surface of the fixing roller 1 is constituted by a thin elastic layer 1c made of silicone rubber
  • the material of the surface of the pressure roller 2 is constituted by a fluororesin layer 2c such as PFA.
  • the pressure roller 2 comprises a core 2b and a silicone rubber layer 2a, and further includes an outer PFA tube 2c surrounding the silicone rubber layer 2a.
  • the fixing roller 1 By constituting the surface of the fixing roller 1 with the elastic material in this way, the fixing ability is increased, and the overpressure to the image is prevented, thus obtaining a good image.
  • Fig. 14 shows the embodiment with a toner having the minus charge polarity.
  • the surface of the fixing roller 1 is covered by the silicone rubber, the surface is apt to be charged to the minus charge polarity. Accordingly, the rectifier element 104 is connected in the normal connection direction so that the potential of the core 1b charged by the charge generated on the surface of the fixing roller 1 is held to the more minus charged condition.
  • the potential of the surface of the fixing roller 1 becomes - 2 kV to generate a strong repulsion force against the toner having the minus charge, thus preventing the toner offset.
  • the surface of the pressure roller 2 is charged to + 250 V, and the rectifier element 103 is connected in such a manner that the plus charge in the core 2b cannot be easily escape to the ground. In this way, since an attracting force for attracting the toner toward the pressure roller 2 from the back of the recording sheet P, the offset preventing effect is still improved.
  • Fig. 15 shows the embodiment with a toner having the plus charge polarity.
  • the offset is prevented by designing that the plus charge is apt to be stored in the core 1b of the fixing roller 1 and the minus charge is apt to be stored in the core 2b of the pressure roller 2.
  • the fixing roller 1 and the pressure roller 2 are connected to each other and are also connected to the earth through the rectifier element so that the charge having the same polarity as that of the toner can be maintained, even if the surface of the fixing roller 1 is charged to the charge polarity opposite to that of the toner or developer, the offset can be prevented, and, since the rollers are connected to the earth through the rectifier element, the electric noise due to the discharge can be avoided, thus preventing the erroneous operation of the image forming system.
  • the rectifier element to the fixing movable member such as a roller, belt, endless sheet and the like in consideration of the connection direction thereof properly, the electrostatic toner offset can be prevented. Further, the electric noise generated by the excessive charging of the fixing movable member can also be avoided, thus preventing the image forming system from operating erroneously due to the electric noise.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fixing For Electrophotography (AREA)
EP89122471A 1988-12-07 1989-12-06 Fixing apparatus Expired - Lifetime EP0372518B1 (en)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
JP307929/88 1988-12-07
JP63307929A JP2575093B2 (ja) 1988-12-07 1988-12-07 定着装置
JP1073795A JP2596530B2 (ja) 1989-03-28 1989-03-28 定着装置
JP73795/89 1989-03-28
JP1285899A JP2592967B2 (ja) 1989-10-31 1989-10-31 画像形成装置
JP1285900A JP2592968B2 (ja) 1989-10-31 1989-10-31 定着装置
JP285900/89 1989-10-31
JP285899/89 1989-10-31

Publications (3)

Publication Number Publication Date
EP0372518A2 EP0372518A2 (en) 1990-06-13
EP0372518A3 EP0372518A3 (en) 1990-11-07
EP0372518B1 true EP0372518B1 (en) 1994-09-14

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP89122471A Expired - Lifetime EP0372518B1 (en) 1988-12-07 1989-12-06 Fixing apparatus

Country Status (3)

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EP (1) EP0372518B1 (ko)
KR (1) KR950014876B1 (ko)
DE (1) DE68918243T2 (ko)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69111326T2 (de) * 1990-08-03 1996-01-11 Canon Kk Elastische Rolle und diese verwendendes Fixiergerät.
JP3696642B2 (ja) * 1995-02-08 2005-09-21 キヤノン株式会社 電子写真装置の定着装置
US11340546B2 (en) 2019-02-18 2022-05-24 Nok Corporation Fuser device

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57172371A (en) * 1981-04-16 1982-10-23 Canon Inc Picture forming device
JPS5934573A (ja) * 1982-08-21 1984-02-24 Canon Inc 画像形成装置
JPS5974577A (ja) * 1982-10-20 1984-04-27 Canon Inc 定着装置
JPS5990874A (ja) * 1982-11-16 1984-05-25 Canon Inc 画像形成装置
JPS60140280A (ja) * 1983-12-27 1985-07-25 Sharp Corp トナ−のオフセツト防止方法

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Publication number Publication date
EP0372518A3 (en) 1990-11-07
KR950014876B1 (ko) 1995-12-16
DE68918243T2 (de) 1995-01-26
KR900010494A (ko) 1990-07-07
DE68918243D1 (de) 1994-10-20
EP0372518A2 (en) 1990-06-13

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