JP2010281887A - Image heating device in image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the damage of the edge of a film caused by biasing of an endless film. <P>SOLUTION: In an image heating device including the rotatable and movable endless film and a heater heating an image on a recording material by heat from the film, a biasing preventing member 28 is provided at the edge of the film 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a film heating type heating apparatus that heats a recording material carrying an image, and an image forming apparatus including the heating apparatus.

  Conventionally, as an image heating device represented by a heat fixing device, a contact heating type fixing device such as a heat roller method or a film heating method has been widely used, and these devices use a current to a halogen lamp and a heating resistor. To generate heat and heat the toner image via a roller or film. Therefore, there is a slight distance between the heat generating position and the toner even in the case of a film heating type fixing device, and the energy consumption efficiency has to be reduced accordingly.

  Various heating devices of the film heating method have already been proposed by the present applicant (Patent Document 1, etc.).

  Basically, a heat-resistant film is sandwiched between a heating element such as a ceramic heater and a pressure contact member to form a heating nip portion, and a material to be heated is placed between the film in the heating nip portion and the pressure contact member. By introducing the film and nipping and conveying it together with the film, the heat of the heating body is applied to the heated material through the film and heated in the heating nip portion. It is possible to construct an on-demand type device with features such as quick start and power saving by reducing the heat capacity of the heating element and film. For example, in image forming devices such as printers, facsimiles, and copiers. Therefore, it can be effectively used as a fixing device for heating and fixing an unfixed image (unfixed toner image) formed and supported on a recording material.

  FIG. 2 shows a cross-sectional model diagram of an example of a film heating type heating apparatus.

  Reference numeral 1 denotes a heating member support member also serving as a film guide having a substantially semicircular cross section. Reference numeral 3 denotes a heating body, which is fitted and held in a slot 1a provided along the length of the member (perpendicular to the drawing) at a substantially central portion of the lower surface of the heating body support member 1. The heating element 3 uses a so-called ceramic heater having a low heat capacity.

  Reference numeral 2 denotes a cylindrical (endless) heat-resistant film which is externally fitted to the heating body support member 1 on which the heating body 3 is fixed and held. The inner peripheral length of the cylindrical film 2 and the outer peripheral length of the heating body support member 1 including the heating body 3 are larger than the film 2 by, for example, about 3 mm. The length fits loosely on the loose.

  Reference numeral 4 denotes an elastic pressure roller as a pressure member, which includes a core metal 4-a and a heat-resistant rubber layer 4-b having good releasability such as silicon rubber. The heating body 3 and the pressure roller 4 are pressed against each other with a predetermined pressing force against the elasticity of the pressure roller 4 with the film 2 interposed therebetween, and a heating nip portion (hereinafter referred to as a heating nip portion) having a predetermined width Wn in the recording material conveyance direction. A fixing nip portion).

  In the fixing device of this example, the inner diameter of the cylindrical film 2 is 30 mm, and the width Wk of the heating element 3 in the recording material conveyance direction is 7.0 mm. The core metal 4-a of the elastic pressure roller 4 has a diameter of 14 mm, the rubber-containing portion 4-b has an outer diameter of 20 mm, and a hardness of 45 ° (ASKER-C total weight 5.88N). The pressurizing force for forming the fixing nip portion is weighted 98.07N. In this state, the fixing nip width Wn is 6.0 mm.

  In order to reduce the heat capacity and improve the quick start property, the film 2 has a film thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more of heat-resistant single layer of PTFE, PFA, FEP, polyimide, polyamideimide, A composite layer film in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of PEEK, PES, PPS or the like can be used. In this example, the outer peripheral surface of the polyimide film is coated with PTFE.

A ceramic heater as the heating element 3 is formed on the surface of a heater substrate 5 made of Al ₂ O ₃ , AlN, or the like on a surface of a heater member (hereinafter referred to as a resistance heating element) 6 such as Ag / Pd (silver palladium). The resistance material is formed to have a thickness of about 15 μm and the width Wt in the recording material conveyance direction is set to 1 to 3 mm by screen printing or the like, and the protective layer 7 is coated with glass, fluorine resin, or the like. A thermistor 8 serving as a heating element temperature detecting element is provided on the surface of the heater substrate 5 opposite to the surface on which the resistance heating element 6 is formed. The thermistor 8 is arranged at a position that fits within the minimum size width of the recording material that can be passed. The protective layer 7 surface side of the heating body 3 is the heater surface side on which the inner surface of the film 2 is in close contact and slides, and the heater surface side is exposed downward to fit into the slot 1a of the heating body support member 1. And fixedly held.

  The pressure roller 4 is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed by a drive system M (not shown). As the pressure roller 4 is driven to rotate, the fixing film 2 slides with its inner surface in close contact with the lower surface of the heating body 3 and slides around the outer periphery of the heating body support member 1 in the clockwise direction as indicated by the broken line. Rotate to.

  Further, as shown in FIG. 2, the heating element 3 is energized from the power supply circuit 14 to the energization heating element 6 so that the temperature of the heating element 3 is quickly raised by the heat generated by the resistance heating element 6 and the temperature state of the heating element 3 is detected by the thermistor 8. Is done. The output of the thermistor 8 is A / D converted by the A / D converter 11 and taken into the control circuit (CPU) 12, and the AC voltage of the power feeding circuit 14 is phase-controlled and wave number controlled by the triac 13 based on the information. Thus, the energization power of the heating element 3 to the resistance heating element 6 is controlled, and the temperature of the heating element 3 is controlled to a predetermined fixing temperature.

  Then, when the pressure roller 4 and the film 2 are rotated as described above and the heating body 3 is energized and adjusted to a predetermined fixing temperature, the film 2 and the pressure roller 4 at the fixing nip portion By introducing the recording material P carrying the unfixed toner image t between them and transporting the recording material P, the unfixed toner image t is heated by the heat from the heating body 3 applied through the film 2 and the pressing force of the fixing nip portion. Is fixed to the recording material P as a fixed image ta by heat and pressure.

Japanese Patent Laid-Open No. 2001-100556

  However, film-type fixing devices using the above-described fixing device have been in the direction of increasing stress on the film and other parts due to, for example, speeding up of the device and long life. In particular, when the jammed paper stays in the fixing unit, when the jammed paper is carelessly pulled diagonally when it is jammed, the film approaches the longitudinal end. There is a possibility that the longitudinal end of the film may be damaged by rubbing between the film end and the side plate of the fixing device. Also, if the film is caught in the gap between the flange that supports the film at the end face and the film guide, the end face of the film may be damaged, or stress may be applied to the center part due to the hook, causing wrinkles in the center part of the film. There was a possibility of being fooled.

  As described above, in order to solve the above problems, the present invention relates to an endless film that can be rotated and an image heating apparatus that heats an image on a recording material by heat from the film. According to the first and fourth aspects of the present invention, by providing the elastic member attached to the film end in the direction orthogonal to the moving direction of the film and the support member for holding the elastic member, the film end contacts the peripheral member. Therefore, the film can be prevented from being damaged. In addition, according to the fifth aspect of the invention, since the film is bent in the nip portion, the film and the peripheral members are not distorted and bent, resulting in a long life state. Moreover, according to the sixth to seventh inventions, the film potential can be kept in a good state. Furthermore, there is an effect of satisfying the safety standard, and this case can provide a detent structure having a plurality of effects other than film breakage.

  As described above, according to the present invention, damage and deterioration of the film edge can be prevented, the apparatus can be reduced in size, increased in speed and increased in durability, and further, the electrical safety standard can be satisfied. .

Sectional drawing of the longitudinal end part of the heat fixing apparatus which is the 1st Embodiment of this invention Figure of conventional fuser Diagram of conventional image forming apparatus Figure of conventional fuser 1 is an exploded perspective view of a longitudinal end portion of the heat fixing apparatus of FIG. FIG. 4 is a diagram of a fixing device configuration according to the first embodiment and a diagram of a force applied to a film during jam processing. Example 2 Fixer Configuration

Example 1
FIG. 3 is a cross-sectional view of an image forming apparatus using the image heating apparatus according to the embodiment of the present invention as a fixing device.

  Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier. The photosensitive drum 1 is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed), and is charged uniformly to a predetermined negative dark potential VD by a primary charger (charging roller) 2 during the rotation process. .

  Reference numeral 3 denotes a laser beam scanner, which outputs a laser beam modulated in accordance with a time-series electric digital image signal of target image information inputted from a host device such as an image reading device (not shown), a word processor, a computer, As described above, the surface of the photosensitive drum 1 negatively charged uniformly by the primary charger 2 is scanned and exposed with a laser beam, so that the absolute value of the exposed portion becomes small and becomes a bright potential VL on the surface of the rotating photosensitive drum 1. An electrostatic latent image corresponding to the target image information is formed.

  Next, the latent image is reversely developed with a negatively charged powder toner by the developing device 4 (toner is attached to the laser exposure portion VL) to be visualized.

  The developing device 4 has a developing sleeve 4a that is rotationally driven. A thin layer of toner having a negative charge is coated on the outer peripheral surface of the developing device 4 so as to face the surface of the drum 1, and the absolute value of the sleeve 4a is a drum. Since the developing bias potential VDC that is smaller than the dark potential VD of 1 and larger than the bright potential VL is applied, the toner on the sleeve 4a is transferred only to the portion of the photosensitive drum 1 where the light potential VL is present, and a latent image is formed. It is visualized (reversal development).

  On the other hand, the recording material P stacked and set on the paper feed tray 14 is fed out and fed to one sheet by the drive of the paper feed roller 13, and passes through the conveyance guide 12 a, the pair of registration rollers 10 and 11, and the transfer guides 8 and 9. Then, the photosensitive drum 1 is fed at an appropriate timing synchronized with the rotation of the photosensitive drum 1 to the nip (transfer portion) m of the transfer roller 5 as a transfer member to which a transfer bias is applied in contact with the photosensitive drum 1. Thus, the toner image on the surface of the photosensitive drum 1 is sequentially transferred onto the surface of the recording material P. The volume resistance value of the transfer roller 5 as a transfer member is suitably about 10 8 to 10 9 Ωcm.

  The recording material 15 that has passed through the transfer portion is separated from the surface of the photosensitive drum 1, introduced into the fixing device 7 that is an image heating device by the conveyance guide 12 b, receives the heat fixing of the transferred toner image, and is discharged as an image formation (print). Output to the paper tray 16. The surface of the photosensitive drum 1 after the separation of the recording material is cleaned by the cleaning device 6 after removal of the transfer drum residual toner and other photosensitive drum surface residues, and is repeatedly used for image formation.

  Next, a fixing device which is an image heating device according to an embodiment of the present invention will be described in detail.

  First, the configuration of the entire fixing device will be described.

  FIG. 2 is a cross-sectional view of the fixing device according to the present invention, which is based on a fixing device that uses an endless film by generating heat from a heater in a holder.

  On the other hand, this case can be applied to a fixing device that generates heat by passing a magnetic flux using a high permeability core through a metal film. I will also describe this fuser (Fig. 4).

  The heat generating layer 20a is preferably made of a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, or nickel-cobalt alloy and has a thickness of 1 to 100 μm. The elastic layer 20b preferably has a thickness of 10 to 500 μm made of a material having good heat resistance and thermal conductivity such as silicon rubber, fluorine rubber, and fluorosilicon rubber.

  The release layer 20c has a thickness of 1 to 100 μm made of a material having good release properties and heat resistance such as fluororesin (PFA, PTFE, FEP, etc.), silicon resin, fluorosilicone rubber, fluororubber, silicone rubber and the like. Is preferred. That is, the high-permeability core 22 is made of a material used for a transformer core such as ferrite or permalloy, and more preferably ferrite having a low loss even at 100 kHz or higher. A coil 23 wound around the core 22 is used as the high-permeability core 22. A magnetic flux is generated by applying a high frequency current of 20 kHz to 500 kHz from an excitation circuit (not shown), and an eddy current is generated in the heat generating layer 20a due to the change in the magnetic flux, and heat is generated by Joule heat based on the specific resistance of the heat generating layer 20a. Will occur.

  On the other hand, on the fixing film 20 configured as described above, a pressure roller 24 composed of a core metal 24a and a silicon rubber layer 24b is disposed as a pressure member so as to be in pressure contact therewith. Then, heat fixing is performed by passing a recording material P on which an unfixed toner image T as a material to be heated is passed through a nip n formed by the fixing film 20.

  That is, the generated heat propagated to the fixing film 20 as described above is transmitted to the nip n, and the recording material 15 being nipped and conveyed by the nip n and the toner T on the recording material 15 are heated. Inside, the toner T melts and passes through the nip n, and then is cooled to form a fixed image, and fixing is performed.

  By the way, when using a fixing device using a film in this way, a shift force is generated on the film depending on the tolerance, alignment or mounting state of the parts, and the end of the film and the side plate of the fixing device rub against each other. Could be damaged. In addition, the recording material may stagnate in the apparatus for some reason such as a power failure or skew. At this time, it is necessary to perform jam processing for removing the recording material. Jam processing refers to an operation of removing the jammed paper from the apparatus by pulling out the recording material from a position where the recording material can be gripped by holding the paper stuck in the apparatus while the apparatus is stopped. At this time, if the jammed paper is forcibly pulled or the recording material is pulled out at an angle with respect to the conveyance direction of the recording material, the recording material will be stressed and the recording material may be torn in the middle, and the recording material and film Due to the frictional resistance of the film, the film and jammed paper may move together, hitting the flange that supports the film at the end, and the end may be damaged.

  Therefore, in the present embodiment, the configuration shown in FIGS. 1 and 5 is adopted. FIG. 1 is a longitudinal end view of the fixing device that best represents the features of the first embodiment of the present invention. FIG. 2 is an exploded perspective view of the longitudinal end portion of the fixing device that best represents the characteristics of the present embodiment.

  1 and 5, reference numeral 25a denotes a heat-resistant fixing cover made of PBT, PPS or LCP, which is provided to cover the entire fixing device and increase the strength of the fixing device. In addition, the fixing cover serves to protect the heated fixing device from being touched even when a user inserts a hand into the apparatus. A detent rib 25b is provided in the conveying direction of the fixing cover. The ribs are close to the film and play a role of preventing the film from shifting (moving) in a thrust direction (perpendicular to the conveying direction) of a locking member 28 described later. A stay (not shown) is included inside the film, and this is pressed by a spring (not shown) or the like, and a pressure roller forms a predetermined fixing nip.

  As the stopper member 28, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, fluororesin (PFA, PTFE, FEPetc.), LCP (liquid crystal polymer) resin , A silicon resin, or a material having a thickness of 0.5 to 3 mm made of a heat-resistant material such as a mixture thereof is preferable. That is, when the thickness is small, the stopper rib 25b is difficult to contact the stopper itself, and the effect of restricting the offset of the film is reduced. On the contrary, if the thickness is large, a force in the peeling direction is easily generated with respect to the adhesion of the stopper member to the film, and the possibility that the stopper member fixed to the film is removed increases. On the other hand, it is preferable that the width of the stopper member 28 in the thrust direction is 1.0 to 5.0 mm. When this width is small, the area of the stopper itself fixed to the entire film is small and smaller than the force in the thrust direction caused by rotation or the force caused by jamming, etc. This is because there is a high possibility that the stopper member is removed. As shown in FIG. 3, when the offset member is large, the size W of the film unit itself including the offset is the width w of the offset, the width kw of the recording material, and the clearance from the recording material end surface to the offset (safety). Design value: Margin width for preventing recording material and stopper from contacting each other) α, W = kw + 2α + 2w.

  Next, the adhesive force Ys at which the stopper is adhered to the film will be described (FIG. 6).

  The fixing unit used in this embodiment forms a fixing nip by pressing a film unit against a pressure roller (not shown) with a total load of 15 kgf. The pressure roller uses a product with a hardness of 40 °, and uses a core of φ11. The surface of the bonding part is roughened for bonding in order to bond the elastic layer, and a silicon adhesive is used. It is applied as a primer, and an elastic layer of silicon rubber is formed thereon with a thickness of 3.5 mm. In order to apply a fluorine tube such as PFA or PTFE on the surface layer, a silicon-based elastic layer is formed between the elastic layer and the tube. Adhesive is applied as a primer. Using such a pressure roller, the width of the fixing nip and about 7.5 mm ± 1.0 mm are formed. The apparatus of this embodiment having such a fixing device uses an image forming apparatus in which the recording material conveyance speed (process speed) is set to about 90 mm / sec. In addition, as a control temperature of a temperature detection element (thermistor) (not shown) arranged in the film unit, the temperature of the heating body itself included in the film unit can be adjusted to about 180 ° C. The tone is controlled.

  When such an image forming apparatus is normally used, about 200 gf of force (shifting force) that moves the film in the end surface direction is applied due to rotation of rollers, component tolerance and alignment of each component, and the like. On the other hand, when jam processing or the like is performed, a force of about 0.5 kgf to 2.0 kgf is applied to the film end surface. Although the stress on the film edge due to the jam treatment depends on the jammed state, the toner remains in the fixing nip, or the OHT that is not intended to be used (unusually coated with resin, etc.) The film and jammed paper are in close contact (adhesion), forcibly jammed, or the transport direction and angle. When the jam processing is performed, the offset force increases extremely and jumps up to about 1.0 kgf to 4.0 kgf.

  That is, the adhesive force between the film and the stopper must be 4.0 kgf or more in the thrust direction in the present configuration. However, depending on the configuration of the apparatus, when the applied pressure increases, the value of Ts needs to be increased.

  In this case, the film surface layer at the position where the detent is adhered is roughened by about several μm, and a silicon adhesive is applied as a primer between the roughened surface and the detent member. By doing so, the adhesive strength between the film and the stopper is about 5.0 kgf or more, so that the device and the film are not broken without being peeled off even in the irregular processing. It can have a function.

  Next, as shown in Fig. 1, the positional relationship between the stopper rib and the stopper member is arranged outside the stopper rib in this case so that the stopper rib always contacts the inside of the stopper. It is arranged. This is because when a thin film is used, if the movement of the film is suppressed from the outside of the detent member, the film itself cannot withstand and the film itself may be destroyed. That is, the inner end of the detent rib is in contact with the outer surface of the detent so that the film end, and thus the detent end, does not contact the wall surface. In addition, when the wall for constituting the fixing device or the wall for regulating the position in the longitudinal direction of the film is the K position, the distance from the detent member is β, and the distance from the regulating member is γ, β It is necessary to satisfy> γ. This is because when the film is thrust in the longitudinal direction, if β <α, the detent member may come into contact with the wall, and at this time, the end of the film may be destroyed. . Therefore, by setting β> α, even if the film depends on the end portion, only the inner surface of the detent on the opposite side to the side on which the film approaches and the outer surface of the regulating member are in contact with each other, and the film end surface contacts the wall There is no longer to do. Further, by keeping the tension on the film, it is possible to always maintain the tension on the film.

  This configuration is also effective when a material having an extremely weak state at the other end portion or a material weak against bending such as metal is used.

  Other than this configuration, if you change the device configuration or increase the buckling strength of the film, that is, increase the thickness, or use a metal film such as SUS or iron, The positional relationship is not limited to this, and it is also possible to form a stop by the outer surface of the rib if there is a buckling force of the film. In this case, since the total film pressure of the film is set to 60 μm, only the former configuration is adopted.

  By taking the configuration as described above, the stress on the film can be alleviated and the stress can be absorbed by the locking member and the rib. For example, when the device is increased in speed or the durability is further improved. Even in this case, it is possible to prevent breakage, breakage, and buckling of the film end, and it is possible to prevent breakage of the end face. In addition, the stopper prevents the film from getting into the gap between the film guide and the flange due to the effect of the width of the stopper to destroy the end face of the film. It is possible to adopt a long life configuration.

(Example 2)
FIG. 7 shows a second embodiment of the present invention.

  In the second embodiment, the anti-shift member in the first embodiment is provided with a resistance value equal to or lower than the middle resistance.

Specifically, the resistance value of the stopper is 3 × 10 ⁸ Ω or less.

  As shown in Fig. 7-a, the conventional fixing film is composed of a fluorine-based top layer, a conductive primer layer for adjusting the film potential by bonding the top layer and the base layer, and the film base. It has a three-layer structure called a PI-based base layer.

  FIG. 7B shows a horizontal view of the fixing device, and the conductive rubber ring (conducting ring on the roller side in the upper drawing) provided conventionally is removed on the pressure roller side. Instead, the above-mentioned detent rib (conducting agent such as carbon is included in the fixing cover) in this case is used as a conductive component. For the purpose of use, in order to adjust the film potential, a part of the conductive primer layer is exposed, the stopper is brought into contact, and the stopper rib is brought into contact with the surface of the stopper member. The stopper rib is dropped to the ground via a diode. The film potential can be kept constant by passing through a diode. The purpose of adjusting the potential of the film is to prevent offset images (image defects caused when toner is not fixed on the paper and part of it adheres to the film side) by keeping the film potential constant. . In addition, it is possible to keep the film potential more constant by applying a voltage to the primer layer of the film using a bias application path (not shown).

  In this way, the stopper is made conductive, and by using various configurations as described above, the stopper of the present invention can be used as an alternative to the conductive rubber ring that has been used as a separate part in the past, and film breakage can be further prevented. By adding a function other than the purpose of preventing shifting, it becomes possible to prevent image defects and to manufacture a cheaper fixing device. Further, as shown in the first embodiment. In addition, it is advantageous for the deterioration and breakage of the film edge, and it is possible to increase the speed and durability of the apparatus.

(Example 3)
In the third embodiment, the detent member in the second embodiment is provided with a resistance value excluding the low resistance side. Specifically, the resistance value of 1.5 MΩ is set as the lower limit.

  This purpose is to satisfy safety standards.

  Since the unfixed toner needs to be melted and fixed on the recording material, the fixing device has a heating element. An alternating current (primary current) is passed through the heating element to generate heat. There is a safety standard that requires basic insulation between the primary grounds defined in the safety standard.

  Here, the stopper according to the present invention is arranged at a position interposed between the primary and the ground. In other words, if the stopper has a resistance value to ensure a safety standard, it is not necessary to separately provide a resistor chip, a safety distance and an intervening member to satisfy the safety standard, thereby reducing costs and reducing the size of the device. Can be made compatible with film edge destruction.

1 Film guide
2 film
4 Pressure roller
20 Example fixing film
28 Stop guide
Ys Adhesive strength of stopper
A Film end face polishing

Claims (7)

A heating body, a support member that holds the heating body, a film that slides on the heating body and the support member, and a pressure that presses against the support member and the heating body via the film to form a nip. A recording material carrying an image between the film in the nip and the pressure member and sandwiching and conveying the recording material to apply the thermal energy of the heating body to the recording material through the film. In an image heating apparatus having a heating device, an endless film that can rotate and a heater for heating the film,
An image heating apparatus comprising: an elastic member fixed to at least a part of an end portion of the film in a direction perpendicular to the sheet passing direction of the recording material.   The image heating apparatus according to claim 1, further comprising a restricting member that restricts a shift of the film, wherein at least the elastic member is in contact with the restricting member.   2. The image heating apparatus according to claim 1, wherein the elastic member of the film and the regulating member are in sliding contact during rotation.   The image heating apparatus according to claim 1, wherein an outer side of the elastic member is regulated by an inner portion of the regulating member.   2. The image heating apparatus according to claim 1, wherein the elastic member has a JIS-A hardness of 40 to 80 [deg.]. The image heating apparatus according to claim 1, wherein the elastic member has an electric resistance of 1.5 × 10 ⁶ or more and 3 × 10 ⁸ or less.   The image heating apparatus according to claim 1, wherein the film is grounded through the support member.

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