JP2002244458A - Image heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning means for preventing an offset toner Tc attracted by a heat discharging roller 30 once from flowing back to a pressure roller 22 again, and capable of stably removing the toner, irrespective of a use situation, in an image heating device 100 provided with heating means 1 and 21, and a pressure rotating body 22 for forming a nip part N in contact with the heating means and for holding and carrying a recording material with a toner image formed, and heating the toner image at the nip part. SOLUTION: The heat radiating roller pressing the pressure rotating body 22 is constituted of a hollow heat pipe 30, and a magnet 31 is arranged inside the heat pipe in a non-contact state, the magnetic toner to be shifted from the pressure rotating body 22 and stuck to the heat pipe 30 is attracted to the heat pipe 30 by the attracting force of the magnet 31 arranged inside the heat pipe, then, melt-sticking toner is prevented from flowing back to the pressure rotating body 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image heating apparatus (heat fixing apparatus) for applying heat energy to a recording material carrying an unfixed toner image to heat and fix the toner image, and heating the recording material carrying the toner image. The present invention relates to an image heating device for improving surface properties such as gloss, an image heating device for performing a temporary deposition process, and an image forming apparatus having the image heating device.

[0002]

2. Description of the Related Art For example, a heat fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile, etc., that is, an image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. Indirect (transfer) or direct image formation on the surface of recording materials (transfer material sheets, printing paper, electrofax sheets, electrostatic recording sheets, etc.) using an agent (toner) to support the target image information As an image heating device for thermally fixing an unfixed toner image on a recording material surface, a heat roller type device has been generally used in general.

[0003] The heating device of the heating roller type is a pressing nip portion between a heating roller (fixing roller) heated by a built-in heat source such as a halogen heater to maintain a predetermined temperature, and an elastic pressing roller pressed against the heating roller. (Fixing nip)
The recording material carrying the unfixed toner image is introduced thereinto and nipped and conveyed, whereby the unfixed toner image on the recording material surface is thermally fixed by the heat of the heating roller.

Recently, a heating device of a film heating type has been proposed and put into practical use (Japanese Patent Application Laid-Open No. 63-31818).
No. 2, Japanese Patent Laid-Open No. 1-263679, Japanese Patent Laid-Open No. 2-263679
No. 157878 / JP-A-4-44075-4408
No. 3, JP-A-4-204980-204984, etc.).

In this heating apparatus, a material to be heated is brought into close contact with a heating member fixedly supported by a supporting member via a heat-resistant thin-walled film material, and the film material is slid and moved to the heating member to heat the heating member. Is applied to a material to be heated via a film material, and can be utilized as an apparatus for thermally fixing an unfixed toner image as a permanent fixed image on a recording material surface carrying the image. Further, for example, it can be widely used as a device that heats a recording material carrying a toner image to improve the surface properties such as gloss, a device that performs a temporary deposition process, and a device that heats a sheet-shaped material to be heated.

[0006] Such a film heating type heating device,
As the heating element, a basic element having a low heat capacity with a rapid temperature rise, for example, a ceramic substrate having an insulating property and a good thermal conductivity, and a resistance heating layer provided on the surface of the substrate and generating heat by energization. A so-called ceramic heater can be used, and since a thin film having a low heat capacity can be used as a film material, the temperature of the heating body rises in a short time, and there is no need to supply power to the heating body during standby. Even if the recording material as the material to be heated is immediately passed, the heating element can be sufficiently heated to a predetermined temperature before the recording material reaches the fixing portion, and the weight time can be reduced (quick start property). : Operate on demand) and save power.
It has an advantage that the temperature rise in the apparatus such as an image forming apparatus can be reduced, and is effective.

In the above-described fixing device of the film heating type, when an unfixed toner image is fixed on the surface of a recording material by forming a nip portion by contacting an elastic pressure roller as a pressure rotating body. In addition, it is known that a small amount of molten toner is offset from the recording material on the surface of the fixing film.

Further, the offset fused toner further includes:
Revolves around the surface of the recording material by driving around,
If the recording material does not exist in the nip portion, the surface of the pressure roller may be stained with the molten toner by offsetting the nip portion to the pressure roller again.

As a means for removing the offset molten toner, a cleaning means for abutting a nonwoven fabric sheet to wipe off the toner on the surface is known.

Further, as described in Japanese Patent Application Laid-Open No. 8-179624, there is provided a means for preventing offset of a toner image without adding a dedicated cleaning device. According to the method of the offset prevention means of the fixing device, a lower fixing roller (pressure roller) that presses a heater of a heating element from below to fix an image on the recording material to the recording material, and contacts the lower fixing roller. A fixing device having a heat radiating roller that absorbs the amount of heat held by the lower fixing roller, wherein the fixing lower roller and the heat radiating roller achieve different rotation speeds. Depending on the lap difference of
Rubbing occurs between the two, and the friction makes it possible to more efficiently remove the toner adhered to the surface of the lower fixing roller.

Further, the toner adhering to the heat radiating roller is
Since the temperature of the heat-dissipating roller is lowered by the heat-dissipating action, the heat-dissipating roller is designed to be able to adhere to the heat-dissipating roller as it is.

In the case of the above-described film heating type fixing device, for example, a fixing film / recording material heating device formed by pressing a heater as a heating member and an elastic pressing roller as a pressing rotating member with a fixing film interposed therebetween. The pressure distribution along the longitudinal direction of the fixing nip portion, which is a portion, is bent at the center in the longitudinal direction of the fixing nip portion because the elastic pressure roller bends because the pressure is applied by being supported at both ends. The pressure may be reduced (pressure drop at the center in the longitudinal direction of the fixing nip portion).

[0013] The heat supply from the heater to the fixing film is less in the pressure drop portion of such a pressure distribution than in other portions, so that the image fixability of the recording material may become non-uniform.

Further, the temperature distribution along the longitudinal direction of the fixing nip portion may take such a form that heat is taken to the surroundings through the core metal of the elastic pressure roller and the temperature at both ends decreases ( Heat dissipation loss at the end).

In such a case, the image fixing property of the recording material portion corresponding to both ends in the longitudinal direction of the fixing nip portion where the temperature is lowered deteriorates, and the image fixing property of the recording material becomes non-uniform. There is.

If the temperature at the recording material entrance of the fixing nip is higher than a predetermined temperature, the recording material that has entered the fixing nip is heated rapidly at the fixing nip entrance. The so-called “tailing” phenomenon in which the unfixed toner image on the recording material is blown backward in the recording material conveyance direction due to the applied water vapor pressure, and the image quality is reduced.

Therefore, it is possible to easily provide a desired heat supply amount distribution in the longitudinal direction and the width direction of the material to be heated of the heating body, that is, the entire surface of the material to be heated is heated. In the fixing device, it is possible to easily adjust the thermal temperature distribution as desired, thereby correcting the pressure drop portion and the radiation loss portion of the fixing nip portion which is the recording material heating portion ( Compensation) or easily adjust the distribution of heat supply in the heating surface of the material to be heated, as desired, so as not to raise the temperature of the inlet of the fixing nip.
Various attempts have been made to ensure uniform fixing properties and to prevent tailing.

Further, in order to stabilize the temperature distribution of the heater or the pressure roller as a heating element in a uniform direction in a short time, the heat radiation roller is made of a heat pipe of aluminum or the like, and the heat conductivity is reduced by reducing the thickness. Was also taking measures to improve

[0019]

However, on the other hand,
Since the heat radiation roller can easily reach high temperature early,
Originally, a low temperature, which is a cleaning effect, promotes the offset of the molten toner and lowers the performance of solidifying the surface of the heat radiating roller.

In a fixing device of an image forming apparatus which is increased in speed and width, the temperature of the ceramic heater is required to be large enough to fix the recording material in accordance with the passing speed of the recording material. Therefore, a considerable amount of heat is required, and since the high-speed fixing device consumes a large amount of recording material continuously, the temperature of the fixing device as a whole rises, and every time the number of sheets passed is increased. In addition, there is a problem that the temperature of the heat radiating roller rises and the effect of adsorbing and holding the toner on the surface of the pressure roller decreases.

As a countermeasure against this, it is necessary to form an air passage for heat shielding or cooling and to provide a cooling fan to suppress a rise in the temperature of the heat radiating roller. To increase the power,
In addition to the possibility that the original performance of the fixing device cannot be fully utilized, there is a problem that the cost is increased.

However, in order to surely prevent the deterioration of the image quality due to the toner offset without impairing the characteristics of the heat pipe for quickly stabilizing the temperature balance in the longitudinal nip direction of the heater, the toner once adsorbed is easily removed. There has been a demand for a cleaning means that does not fall off.

According to the present invention, there is provided a heating means, and a pressurizing rotating body which forms a nip by being pressed against the heating means, wherein the recording material carrying the toner image is nipped and conveyed by the nip to heat the toner image. As described above, the present invention provides a cleaning means for preventing the offset toner once adsorbed on the heat radiating roller from flowing back to the pressure roller again, and for stably removing the toner regardless of the use condition. The purpose is to do.

[0024]

According to the present invention, there is provided an image heating apparatus and an image forming apparatus having the following constitutions.

(1) A heating means, and a pressurizing rotating body which forms a nip by pressing against the heating means, wherein the recording material carrying the toner image is nipped and conveyed by the nip to heat the toner image. An image heating apparatus, comprising: a cylindrical heat pipe that rotates in contact with the surface of the pressure rotating body; and a magnet disposed inside the heat pipe.

(2) The heat pipe is in contact with the heating means and the pressure rotating body on the recording material discharge side of the pressure rotating body, and rotates in a direction opposite to the rotation direction of the pressure rotating body. The image heating apparatus according to (1), wherein:

(3) The magnet is disposed in non-contact with the inner peripheral portion of the heat pipe. (1)
Or the image heating device according to (2).

(4) The magnet is disposed in the inner peripheral portion of the heat pipe in a direction intersecting the N-pole and the S-pole with respect to the sheet passing direction, and magnetic poles are alternately arranged in a circumferential direction. The image heating device according to any one of (1) to (3), wherein the image heating device is disposed in a direction extending in a longitudinal direction of the heat pipe.

(5) The magnet is located at a position corresponding to the nip portion on the inner periphery of the heat pipe.
The image heating apparatus according to any one of (1) to (3), wherein an N pole or an S pole is provided, and the N pole or the S pole is provided in a direction extending in a longitudinal direction of the heat pipe.

(6) In an image forming apparatus having an image forming means for forming and carrying an unfixed toner image on a recording material and a fixing device for thermally fixing the unfixed toner image on the recording material, the fixing device may be composed of ( An image forming apparatus, which is the image heating apparatus according to any one of (1) to (5).

<Operation> The toner offset to the pressure rotating body is adsorbed and held by a cylindrical heat pipe which is a heat radiating roller which rotates in contact with the pressure rotating body, and is further disposed inside the heat pipe. Is securely held magnetically on the heat pipe surface by the magnetic force of the magnet, and the backflow to the pressurizing rotating body side is prevented again.

By disposing the magnet in a non-contact manner with the inner peripheral portion of the heat pipe, a space is provided for preventing a decrease in the heat conduction performance of the heat pipe. This allows
Without increasing the heat capacity of the hollow heat pipe,
It is intended to prevent a decrease in performance related to heat conduction.

The magnets disposed inside the hollow heat pipe are arranged in a direction intersecting the N-pole and the S-pole in the heat pipe inner peripheral portion with respect to the paper passing direction, and the magnetic poles are alternately arranged in the circumferential direction. In addition to the arrangement, the magnetic circuit for preventing the detachment of the toner adsorbed and held on the surface of the hollow heat pipe was finely arranged by disposing in the direction extending in the longitudinal direction of the hollow heat pipe. Thereby, a toner adsorption layer can be formed on the surface of the hollow heat pipe with a uniform thickness.

The magnet disposed inside the hollow heat pipe has an N pole or an S pole at a position corresponding to the nip portion on the inner periphery of the heat pipe,
By arranging the heat pipe in the longitudinal direction, it is possible to minimize the variation in the magnetic force distribution in the nip and to maintain a constant toner magnetic attraction force in the nip.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (FIGS. 1 to 4) (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this embodiment is a laser beam printer using a transfer type electrophotographic process.

Reference numeral 101 denotes a photosensitive drum as an image carrier, which is formed of a photosensitive material such as an OPC (organic photoconductor), amorphous Se, or amorphous Si on a cylindrical substrate such as aluminum or nickel.

The photosensitive drum 101 is driven to rotate at a predetermined peripheral speed (process speed) in the clockwise direction indicated by an arrow.
During the rotation process, the charging roller 102 as a charging unit is uniformly charged to a predetermined polarity and potential.

Next, the charge control surface of the rotating photosensitive drum 101 is subjected to modulation control (corresponding to a time-series electric digital pixel signal of target image information output from a laser scanning exposure apparatus (laser beam scanner) 103). ON / OF
The scanning exposure is performed by the laser beam L subjected to the F control, and an electrostatic latent image corresponding to target image information is formed on the rotating photosensitive drum surface.

The electrostatic latent image formed on the surface of the rotating photosensitive drum is developed (visualized) as a toner image by the developing device 104. As a development method, a jumping development method, a two-component development method, an FEED development method, or the like is used, and a combination of image exposure and reversal development is often used.

On the other hand, a recording material (transfer material) is fed from a paper feed mechanism (not shown) to a nip portion (transfer nip portion) n between the rotating photosensitive drum 101 and a transfer roller 105 as a transfer means in contact with the drum. P) is fed at a predetermined control timing, and is nipped and conveyed at a constant pressing force between the transfer nip portion n, ie, between the photosensitive drum 101 and the transfer roller 105, so that the toner image on the surface of the rotating photosensitive drum 101 is It is sequentially transferred to the surface.

The recording material P to which the toner image has been transferred at the transfer nip n is separated from the surface of the photosensitive drum 101, and is conveyed to a heat fixing device 100 as an image heating device, where the toner image is heated and fixed, and discharged and conveyed. Is done.

After the transfer of the toner image onto the recording material P, the surface of the photosensitive drum 101 is cleaned by the cleaning device 106 after removing the residual toner and other contaminants remaining after transfer, and is repeatedly used for image formation.

(2) Heat fixing device 100 a) Overall schematic structure of the device 100 FIG. 2 is a schematic cross-sectional view showing the schematic structure of the heat fixing device 100 of this embodiment, and FIG. 3 is an elastic pressure roller and a heat pipe portion. 4A is an enlarged cross-sectional model diagram of a fixing nip portion, and FIG. 4B is a plan model diagram of a back side of a ceramic heater as a heating element.

The heat fixing device 100 of this embodiment is disclosed in
No. 4,075,440-83, and the like.

In FIG. 2, reference numeral 1 denotes a ceramic heater as a heating element (hereinafter, referred to as a heater), reference numeral 20 denotes a heater holder (heating element support member), and reference numeral 21 denotes a cylindrical heat-resistant film material (hereinafter, referred to as a fixing film). ) And 22 are elastic pressure rollers (hereinafter referred to as pressure rollers) as rotating pressure bodies, and 30 is a cylindrical hollow heat pipe as a heat radiation roller.

The heater 1 is a horizontally long and thin plate-shaped member having a low heat capacity, the length of which is a direction intersecting the paper passing direction.
The temperature is quickly raised by applying power to the heat generating layer provided therein to control the temperature to a predetermined temperature. Further details of the heater 1 will be described later.

The heater holder 20 is a trough-shaped member having a substantially semicircular cross section formed of liquid crystal polymer, phenolic resin, PPS, PEEK, or the like. 1 is fitted and fixedly supported.

The cylindrical fixing film 21 is loosely fitted to the heater holder 20 on which the heater 1 is fixedly supported.

The pressure roller 22 includes a core 2 (shaft).
2a, and an elastic layer 22b formed by foaming heat-resistant rubber such as silicone rubber or fluorine rubber or silicone rubber on the outside thereof. Further P is added to the outside of the elastic layer 22b.
A release layer such as FA / PTFE / FEP may be formed. This pressure roller 22 is a core metal 22 as shown in FIG.
The two ends of a are rotatably supported between the driving side plate 37 and the supporting side plate 38 of the apparatus via bearings 39 such as bearings. A drive gear 40 is fixed to the driving-side end of the cored bar 22a, and a rotational force is transmitted to the drive gear 40 from a drive mechanism (not shown) so that the pressure roller 22 is moved counterclockwise in FIG. At a predetermined peripheral speed.

On the upper side of the pressure roller 22, the above-described assembly (heating means) of the heater 1, the heater holder 20, and the fixing film 21 is arranged in parallel with the pressure roller 22 with the heater 1 side facing downward. 20 is applied to the elastic layer 22 of the pressure roller
b by pressing downward with a predetermined pressing force against the elasticity of the fixing film 21 so that the heater 1
By pressing the pressure roller 22 and the pressure roller 22, a fixing nip portion N having a predetermined width as a heating portion is formed.

The cylindrical fixing film 21 is formed by the contact frictional force at the fixing nip portion N between the roller 22 and the outer surface of the fixing film 21 by the rotational driving of the pressure roller 22.
The fixing film 21 rotates clockwise as indicated by an arrow in FIG. 2 while the inner surface of the film slides on the outer periphery of the heater holder 20 at the fixing nip portion N in close contact with the downward surface of the heater 1.

When the fixing film 21 is rotated by the rotation of the pressing roller 22 and the heater 1 is heated to a predetermined temperature by energizing the heater 1, the fixing film 21 in the fixing nip N and the elastic pressing roller 22 are rotated.
4A, a recording material P carrying an unfixed toner image T is introduced as shown in FIG. 4A, and the toner image carrying surface is brought into close contact with the outer surface of the fixing film 21 to form a fixing nip together with the fixing film 21. By passing through N, the heat of the heater 1 is applied to the recording material P via the fixing film 21, and the unfixed toner image T is heat-fixed Ta on the surface of the recording material P. The recording material P that has passed through the fixing nip N is separated from the surface of the fixing film 21 by a curvature and is discharged and conveyed.

The heater holder 20 functions as a support member for the heater 1 and pressurizes the fixing nip N.
It also serves to improve the rotational conveyance stability of the cylindrical fixing film 21.

The fixing film 21 has an inner surface on the lower surface of the heater 1 at the fixing nip portion N and a fixing nip portion N
Is rotated while sliding on the outer surface of the heater holder 20 in the vicinity of. In order to rotate the fixing film 21 smoothly with low torque, the frictional resistance between the heater 1 and the heater holder 20 and the fixing film 21 is reduced. Therefore, a small amount of lubricant such as heat-resistant grease is interposed between the fixing film 21 and the heater 1 and the heater holder 20. Thus, the fixing film 21 can rotate smoothly.

The fixing film 21 is a member having a small heat capacity.
Polyimide, polyamide imide, PEEK, PES, PPS, PFA, with heat resistance and thermoplasticity with the following thickness
Films such as PTFE and FEP. Further, a film having sufficient strength and excellent durability for constituting a heat fixing device having a long service life is required to have a thickness of 20 μm or more. Therefore, the thickness of the fixing film 21 is 20 μm.
It is optimal that the thickness is at least m and at most 100 μm. Further, in order to prevent offset and ensure the separating property of the recording material, the surface layer of the fixing film is coated with a heat-resistant resin having good releasability, such as PFA, PTFE, FEP, or silicone resin, or coated alone.

The heat pipe 30 is provided with the elastic pressure roller 2.
2, and has a length substantially the same as that of the pressure roller 2, and is rotatably supported between the side plates 37 and 38 of the apparatus via bearings 36 and 36 so as to be in contact with the elastic pressure roller 22. It rotates following the rotation of 22. A magnet 31 is built in the heat pipe 30.

The offset toner Tb (FIG. 2) adhered to the surface of the pressure roller 22 is transferred and adhered Tc to the surface of the heat pipe 30 by the heat pipe 30 and removed from the surface of the pressure roller 22. The details of the heat pipe 30 will be described later.

B) Heater 1 As shown in FIG. 4, the heater 1 in this embodiment has a ceramic base (heater base) 2 and a ceramic base 2
Is a heating layer pattern (a resistance heating element layer that generates heat by energization) 3 provided on one side (back side) of the ceramic base 2 and the substrate surface of the ceramic base 2 provided with the heating layer pattern 3 The opposite substrate surface (surface side) is a surface for applying thermal energy to the recording material P, and the pattern layer 13 is made of a material having a lower thermal conductivity than the ceramic substrate 2 on the substrate surface side.
(Hereinafter referred to as a low thermal conductivity pattern layer) is a backside heating type ceramic heater in which a desired heat supply distribution is provided within a heating surface of the heater 1.

The fixing film 21 slides in contact with the heater surface, that is, the surface of the ceramic substrate 2 on which the low thermal conductivity pattern layer 13 has been formed, in the fixing nip portion N, and slides. Is transmitted to the fixing film 21 and the recording material P through the ceramic substrate 2.

The ceramic substrate 2 as a heater substrate is made of, for example, alumina (Al ₂ O ₃ ) / aluminum nitride (Al
N) and the like, for example, a horizontally long plate material having a length of 240 mm, a width of 10 mm, and a thickness of 1 mm.

In this embodiment, the low thermal conductivity pattern layer 13 is, for example, a glass coat having a thickness of about 50 μm. Usually, the thermal conductivity of glass is 2-3 × 10 ⁻³ (ca1 / cm · se).
c · K), and the thermal conductivity is 1 to 100 times lower than that of the ceramic substrate. By the way, the thermal conductivity of alumina is 5 ×
It is about 10 ⁻² (cal / cm · sec · K), and about 5 × 10 ⁻¹ (caI / cm · sec · K) for aluminum nitride.

The heating layer pattern 3 is made of, for example, an electric resistance material paste (resistance paste) such as silver palladium or (Ag / Pd) .Ta ₂ N, for example, with a thickness of 10 μm and a width of 1 to 3.
It is formed by coating and baking a thin strip of mm along the length of the back surface of the heater substrate by screen printing or the like.

Reference numeral 4 denotes a conductor pattern (A) formed along the length of the back surface of the heater base material in parallel with the heating layer pattern 3.
C heating section), the heat generating layer pattern 3 and the conductor pattern 4
Are electrically connected to each other on the same side. 4a
Reference numeral 4b denotes an electrode portion (AC electrode portion) electrically connected to the other end portions of the heating layer pattern 3 and the conductor pattern 4, respectively.

Reference numeral 12 denotes a thermistor chip as a temperature detecting element, which is disposed substantially at the center in the longitudinal direction of the back surface of the heater base material. 9.9, 9a and 9b are thermistor chips 1
2 are a wiring pattern portion (DC energizing portion) and an electrode portion (DC electrode portion). The thermistor chip 12 is provided by bonding electrodes on the thermistor chip 12 side to the wiring portions 9 with a conductive adhesive.

The above-described conductor pattern 4 and electrode portions 4a and 4
b, the wiring pattern portions 9 and the electrode portions 9a and 9b are all formed by applying a pattern of a conductive material paste such as Ag on the back surface of the heater base material 2 by screen printing or the like and firing the paste.

The heater 1 is energized from the power supply circuit (not shown) to the heat generating layer pattern 3 via the electrode portions 4a and 4b and the conductor pattern 4 to generate heat over the entire length of the heat generating layer pattern 3. The temperature of the entire heater 1 rises rapidly.

The temperature rise of the heater 1 is detected by the thermistor chip 12, and the detected temperature information is transmitted to the wiring section 9.
9. The signal is fed back to a temperature control circuit (not shown) via the electrodes 9a and 9b. The temperature control circuit controls the power supply from the power supply circuit unit to the heating layer pattern 3 so that the heater temperature detected by the thermistor chip 12 is maintained at a predetermined substantially constant temperature (fixing temperature). That is, the heater 1 is heated and adjusted to a predetermined fixing temperature.

The fixing nip N is heated by the heat of the heater 1 via the fixing film 21, and the recording material P introduced into the fixing nip N is
Is heated through.

Such a film heating type heating apparatus can use a so-called ceramic heater 1 having a low heat capacity and a rapid heating as a heating element, and a thin film film having a low heat capacity as the film material 21. A pressure roller 22 having an elastic layer for high rigidity 1 is flattened at a pressure contact portion following a flat lower surface of the heater 1 pressed against the pressure roller 22 to form a fixing nip portion N having a predetermined width. By heating only the fixing nip N, a quick start can be achieved compared to other heating devices such as a hot roller system.
It achieves power-saving heat fixing.

The fixing film 21 slides in contact with the heater surface, that is, the surface of the ceramic substrate 2 on which the low thermal conductivity pattern layer 13 has been formed, in the fixing nip portion N, and slides. Is transmitted to the fixing film 21 and the recording material P through the ceramic substrate 2.

In some cases, the glass coat 13 as a low thermal conductivity pattern layer formed on the front surface side of the heater corrects the pressure distribution in the longitudinal direction of the fixing nip N and corrects the pressure distribution in the longitudinal direction of the fixing nip N. The pattern is such that the heat supply amount distribution is substantially uniform.

That is, the pressure distribution along the longitudinal direction of the fixing nip N formed by pressing the heater 1 and the pressure roller 22 with the fixing film 21 interposed therebetween is such that the pressure roller 22 is supported at both ends and the pressure distribution is When the fixing nip N is bent, the pressure at the central portion in the longitudinal direction of the fixing nip portion N may be reduced (pressure drop at the central portion in the longitudinal direction of the fixing nip portion N). In the pressure drop portion of such a pressure distribution, the heater 1 feeds the fixing film 21.
When the amount of heat supplied to the side becomes smaller than that of other portions, the image fixing property of the recording material may become non-uniform.

Therefore, in the case of this example, the pattern of the glass coat 13 as the low thermal conductivity pattern layer formed on the front surface side of the heater is changed to the central portion corresponding to the pressure drop portion of the pressure distribution in the longitudinal direction of the fixing nip portion N. The width at
The pattern is configured to be narrower than the width of both end portions. Thus, the heater 1 at the central portion corresponding to the pressure drop portion of the pressure distribution in the longitudinal direction of the fixing nip portion N
Therefore, the amount of heat supply to the fixing film 21 side can be increased as compared with the both end portions, and the shortage of the pressure at the central portion in the longitudinal direction of the fixing nip portion N can be compensated by heat.
Uniform fixability can be secured.

Further, the temperature distribution along the longitudinal direction of the fixing nip portion N may be such that heat is taken to the surroundings through the core metal 22a of the elastic pressure roller 22 and the temperature at both ends decreases. Possible (heat dissipation loss at the edge). Then, the image fixing property of the recording material portion corresponding to both ends in the longitudinal direction of the fixing nip portion where the temperature is lowered may deteriorate, and the image fixing property of the recording material may become non-uniform.

In such a case, on the heater surface side, a glass coat is formed at the central portion in the longitudinal direction of the fixing nip portion N, and both ends are not coated with the glass coat. By forming and providing the layer 13, the heat supply amount at both end portions in the longitudinal direction of the fixing nip portion N can be relatively increased as compared with the central portion, so that the fixability at the end portions can also be improved.

As described above, the pattern of the glass coat 13 as the low thermal conductivity pattern layer makes it possible to easily have a desired distribution of the amount of heat supply in the recording material heating surface of the heater 1, so that the heating and fixing device can be used. If so, problems such as poor fixing and tailing can be solved.

C) Heat Pipe 30 The heat pipe 30 removes the offset toner Tb (FIG. 2) from the surface of the pressure roller 22 by transferring and transferring the offset toner Tb (FIG. 2) to the surface of the heat pipe 30. I do. That is, the heater 1 and the pressure roller 22 contact the surface of the elastic pressure roller 22 in the upstream direction near the recording material discharge side between the heater 1 and the pressure roller 22 in the direction opposite to the rotation direction of the pressure roller 22 as shown by the arrow. A cylindrical hollow heat pipe 30 for forming a rotating nip, in which magnets 31 are arranged as shown in N and S in FIG. Orbiting the surface of the fixing film 21,
The toner again reaches the nip portion and adheres to the pressure roller 22 by offset, or the toner from the recording material is re-applied to the surface of the pressure roller, which is a lower surface generated when images are formed on both sides of the recording material. The toner Tb offset from the fixing nip N to the elastic pressure roller 22 contacts the surface of the heat pipe 30 due to the offset caused by melting, and the temperature difference between the heat pipe 30 and the pressure roller 22 and the internal temperature. Is attracted and held on the roller surface of the heat pipe 30 by the magnetic attraction force of the magnet 31, and the attracted and held toner Tc is prevented from flowing back to the elastic pressure roller 22 again.

As shown in the figure, a magnet 31 is provided inside a hollow heat pipe 30 so that toner, which is a magnetic substance, is attracted to the surface of the heat pipe 30 so that the toner is securely held. is there.

The heat pipe 30 has a temperature correcting function for quickly and uniformly making the temperature of the surface of the heater 1 and the temperature of the pressure roller 22 uniform in the longitudinal direction of the cylinder. When a small-sized recording material having a narrow width in the direction is continuously passed, the temperature of the portion of the heater 1 where the recording material P is deprived of heat in the longitudinal nip portion N decreases. When the thermistor 12, which is a means, detects the current, it works to increase and stabilize the current in order to return to a specified temperature by electrical control.

At this time, a current flows similarly at both ends of the heater 1 through which the small-sized recording material P does not pass in the longitudinal direction of the heater 1 in spite of a small heat loss.
Conversely, the temperature will exceed the specified temperature.

The heat of the heater 1 is transferred to the pressure roller 22
Then, the heat is conducted by the contact of the fixing nip N, and the temperature of the pressure roller 22 is increased.

The pressure roller 22 has a low thermal conductivity because it is mainly composed of rubber, and the surface of the pressure roller 22 has a temperature difference between a small-size paper-passing region and a non-paper-passing region of the recording P, and then has a large width. When the recording material passes, the temperature difference of the toner T deviates from the optimum fixing temperature due to a temperature difference, and the temperature condition of the offset is deteriorated. Is significantly reduced.

In order to prevent such a situation, the cylindrical heat pipe 30 is brought into contact with the pressure roller 22 so that the heat of the high temperature part can be reduced by utilizing the heat conductivity of the heat pipe 30. And the temperature gradient on the surface of the pressure roller 22 must be quickly reduced to a minimum.

Therefore, it is preferable that the heat pipe 30 is made of a material such as aluminum or magnesium having a good thermal conductivity and made thin (about 1 mm thick) into a cylindrical shape.

Further, the surface can be provided with fine irregularities such as satin, so that the toner adsorbing property can be improved to further increase the holding power.

The magnet 31 disposed inside the hollow heat pipe 30 is arranged in non-contact with the inner peripheral portion of the heat pipe, so that the heat capacity of the hollow heat pipe 30 can be increased or the heat conductivity can be reduced. Without loss
This is achieved by providing a space for preventing a decrease in performance related to heat conduction.

As shown in FIGS. 2 and 3, the heat pipe 3
Numeral 0 has a hollow cylindrical shape, and the magnet 31 and the space 32 are formed at both ends by flange-shaped lids 42 and fixed to the shaft 35.

The magnet 31 is positioned and held and fixed to a magnet holder 34 having a plurality of grooves by using fixing means such as bonding.

Further, the shaft 35 and the magnet holder 34
The heat pipe 30 abuts on the surface of the elastic pressure roller 22 while applying an appropriate urging force while performing thermal insulation while minimizing thermal loss while providing friction by the elastic heat insulator 41 therebetween. It is like that.

The elastic heat insulator 41 can satisfy the above function by using a material such as foamed silicone rubber or foamed urethane rubber.

The shaft 35 extends in the longitudinal direction.
It is rotatably held via bearings 36 and 36 and is mounted between the side plates 37 and 38 of the apparatus.

Even if the temperature of both ends of the pressure roller 22 rises, heat is conducted to the heat pipe 30 in contact with the small-sized recording material passing through the longitudinal center portion, and the heat pipe 30 is quickly heated by the heat pipe 30. Is diffused and moved, and the temperature is reduced in the central temperature-lowering portion, so that heat is transmitted to the pressing roller 22 that is in contact with the pressure roller 22 so that the temperature imbalance can be made to be substantially constant in a short time. is there.

In this manner, the cleaning conditions for the offset toner can be made linear so that the heat pipe 30
The temperature condition for uniformly adsorbing the toner can be set on the surface of.

The magnet 31 inside the heat pipe 30 attracts and holds the magnetic toner by a magnetic force, so that the cleaned toner is prevented from being again offset to the pressure roller 22 again.

As another method for applying friction to the heat pipe 30, the elastic heat insulator 41 is set as a solid material of heat insulating material (for example, heat-resistant plastic), and the bearing 36 is separately provided with a long hole-shaped guide, and a coil spring or the like is provided. It is also possible to give friction by using a spring, and it is also possible to balance the contact pressure with a spring.

<Embodiment 2> (FIG. 5) A magnet 31 provided inside a hollow heat pipe 30 which is a heat radiation roller in FIG. The north pole and the south pole are arranged in a direction intersecting the paper passing direction.
5 is also integrally formed with the shaft 35 as in the apparatus of FIG. 4, so that the magnetic poles N and S of the magnet 31 also rotate. .

Therefore, the toner Tc adsorbed on the surface of the heat pipe 30 is reliably held by the attraction of the magnet 31.

Further, in order to finely arrange the magnetic circuit for preventing the detachment of the toner adsorbed and held on the surface of the hollow heat pipe 30, the magnetic force on the surface of the hollow heat pipe is increased by increasing the number of magnetic poles of NS. Can be made closer to linear, the thickness of the deposited toner adsorbed by cleaning can be made more uniform, and a toner adsorption layer can be formed.

On the other hand, in the magnet 31, the N and S poles can be formed by laminating ring magnets in the longitudinal direction of the cylindrical shape of the heat radiating roller 43.

In this case, by arranging the magnetic force of the magnet in the vicinity of the size of the recording material P, the arrangement is such that the thickness of the toner layers can be made uniform and the toner layer can be prevented from being separated again. It is possible to set it as possible.

Specifically, in the image forming apparatus,
The recording material P to be applied is a postcard, B5, A5, B5, A
There are various types such as 4, B4, and A3 sizes. When an image is formed, the sheet passes through the heat fixing device. However, as described above, when the sheet is continuously passed, a temperature difference occurs between the sheet passing portion and the non-sheet passing portion, Here, when recording materials of different sizes pass, the offset of the toner tends to occur easily.

On the other hand, the toner on the toner image surface is offset and adsorbed on the heat pipe 30 to be cleaned. At this time, a small amount of paper dust, dirt, dust and the like are also cleaned while adhering to the molten toner. Therefore, the toner layer stack deposited on the heat pipe 30 contains various foreign substances.

Since these foreign matters accumulate in accordance with the width of the recording material, heat pipes 3 corresponding to different widths are used.
Steps are formed on the zero surface according to the number of durable sheets and the used paper size.

Since the step is stressed by the nip pressure, the nip pressure causes fluidization during heating,
Cracks are likely to occur during cooling.

According to the present invention, by setting the attraction force, which is the magnetic force of the magnet 31 at a position corresponding to this stress, to be high, the toner flows back to the pressure roller 22 which is likely to be generated at the time of heating flow. Pressure roller 22 so as to prevent the toner lamination portion from being separated or peeled off by a crack generated due to stress in the nip portion.
This prevents the toner from flowing backward.

It is also possible to use an anisotropic magnet in an endless cylindrical shape, and the same effect as described above can be obtained.

<Embodiment 3> (FIGS. 6 and 7) FIGS. 6 and 7 show another embodiment. In this embodiment, inside the hollow cylindrical heat pipe 30,
The magnet 31 of either the N or S magnetic pole shown in the figure is fixedly disposed on the pressing roller 22.

The magnet 31 disposed inside the heat pipe 30 has an N-pole or S-pole magnet at the nip portion which is in contact with the pressure roller 22 at the inner periphery of the heat pipe. With deployment,
By arranging the hollow heat pipe 30 in a direction extending in the longitudinal direction, the magnetic force in the nip portion is united to minimize the variation in the magnetic force distribution with respect to the nip, and the toner magnetic force is always constant in the nip portion. The suction force can be maintained.

The temperature of the heat pipe 30, which is a heat-radiating roller, reaches the highest temperature because the nip portion receives heat from the pressure roller 22, and the temperature gradually decreases along the rotation direction of the arrow.

Accordingly, the cleaning action is offset from the pressure roller 22 to the surface of the heat pipe 30 at the nip portion. However, a large magnet 31 must be provided and installed in the internal nip portion so as to surely clean the molten pipe in the molten state. Thus, the backflow of the toner is prevented and the toner is surely adsorbed.

As shown in FIG. 7, the support shaft 45 of the heat pipe 30 is fixed to the drive side plate 37 so as not to rotate like the fixing means 46. In this case, the holes are engaged with the D-cut holes, but fixing means such as screws may be used.

Further, bearings 44, 44 are arranged near both ends of the support shaft 45, and these bearings are pressed into the heat pipe 30 and fixed thereto, so that the heat pipe 30 is connected to the support shaft 45.
Is rotatable around bearings 44 via bearings 44, 44, and rotates following the rotation of the pressure roller 22.

On the other hand, the magnet 31 is fitted to the magnet holder 34 held and fixed to the support shaft 45 by using a fixing means such as bonding, and a space 32 is provided between the magnet 31 and the inner surface of the heat pipe 30 so that a gap is formed. The magnet 31 is fixed to the contact nip between the pressure roller 22 and the heat pipe 30, and only the heat pipe 30 between the nip and the magnet 31 is freely rotatably disposed.

Since the hollow heat pipe 30 does not come into contact with the heat absorber other than the bearings 44, the heat of the pressure roller 22 can be efficiently diffused and conducted.

With a simple and inexpensive configuration without increasing the number of magnetic poles, the cleaning effect can be maintained stably and without impairing the thermal efficiency, and the backflow of the toner layer adsorbed on the heat pipe 30 can be prevented. It was done.

In addition, the same cleaning effect can be obtained even if the anisotropic magnet of the magnet 31 shown in FIG. 5 is similarly arranged as shown in FIG.

As described above, in the heat fixing device of each embodiment, in order to prevent the toner offset phenomenon occurring at the time of heat fixing, the toner backflow phenomenon at the time of cleaning by the heat radiating roller contacting the elastic pressure roller. By using a magnet to adsorb, it is possible to provide a cleaning means capable of coping with high speed and high durability by eliminating a problem at the time of adsorbing due to a conventional temperature difference and enabling reliable cleaning. The effect was obtained.

Further, since it is possible to minimize the deterioration of the image quality due to the re-fixing of the offset toner caused by the offset phenomenon, it is possible to provide a heat fixing device of a higher quality and higher quality image forming apparatus. The effect was obtained.

<Others> 1) The pressure rotating body 22 is not limited to a roller body, but may be a rotating belt body.

2) Ceramic heater 1 as heating element
Is not limited to the backside heating type of the embodiment, but may be a so-called surface heating type, and the specific configuration is also arbitrary. Further, the heating element may be a heater using an electromagnetic induction heating member.

3) In a film type image heating apparatus,
The fixing film 21 is not limited to the endless shape, but may be a device structure in which a harmful film is fed out and run as a rolled ended web-like film.

4) In the present invention, the constitution of the heating means is optional, and the present invention is also applied to an image heating apparatus such as a heat roller fixing apparatus of a type in which fixing is performed by a heating roller having a heating means inside a roller member. Applicable.

5) The image heating apparatus of the present invention is not limited to the fixing apparatus of the embodiment, but may be an image heating apparatus which heats a recording material carrying an image to improve the surface properties such as gloss, and an image heating apparatus which performs a presumed deposition process. It can also be used effectively as such.

[0124]

As described above, according to the present invention, there is provided a recording device having a heating means and a pressure rotating body which forms a nip portion by pressing against the heating means, and which carries a toner image in the nip portion. In an image heating device that heats a toner image by nipping and conveying a material, a toner reverse flow phenomenon when a toner offset to a pressing rotator is cleaned by a heat radiating roller (heat pipe) in contact with the pressing rotator is magnetized. It is possible to provide a cleaning means that can respond to high speed and high durability by eliminating the problem of adsorption by the conventional temperature difference and eliminating the problem of adsorption by the conventional temperature difference. The effect was obtained.

Further, since it is possible to minimize the deterioration in image quality due to the re-fixing of the offset toner caused by the offset phenomenon, it is possible to provide an image heating device of a higher quality and higher quality image forming apparatus. The effect was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus.

FIG. 2 is a schematic cross-sectional view showing a schematic configuration of a heat fixing device according to the first embodiment.

FIG. 3 is a model diagram of a longitudinal section of an elastic pressure roller and a heat pipe portion.

4A is an enlarged cross-sectional model diagram of a fixing nip portion, and FIG. 4B is a plan model diagram of a back side of a ceramic heater as a heating element.

FIG. 5 is a schematic longitudinal cross-sectional view of a main part of a heat fixing device according to a second embodiment.

FIG. 6 is a schematic diagram illustrating a configuration of a heat fixing device according to the first embodiment.

FIG. 7 is a schematic longitudinal sectional view of a main part of a heat fixing device according to a third embodiment;

[Explanation of symbols]

 Reference Signs List 101 photosensitive drum (image carrier) 102 charging roller 103 laser beam scanner 104 developing device 105 transfer roller 106 cleaning device 100 heating fixing device 1 heating member 20 heating member support member (heater holder) 21 fixing film (heat resistant thin film material) 22) Elastic pressure roller (pressure roller) 2 Heating substrate (heater substrate) 3 Heat generation layer 12 Temperature detector (thermistor) 13 Low thermal conductivity pattern layer (glass layer) N Fixing nip P Recording material (transfer material) ) 30 heat pipe 31 magnet 32 space (gap) 34 magnet holder 35 shaft 36 bearing 37 drive side plate 38 support side plate 39 bearing 40 gear 41 elastic heat insulator 42 lid 44 bearing 45 support shaft 46 fixing means

Claims (6)

[Claims] An image forming apparatus comprising: a heating unit; and a pressurizing rotating body that forms a nip by being pressed against the heating unit, and heats the toner image by nipping and conveying a recording material carrying a toner image in the nip. An image heating apparatus, comprising: a cylindrical heat pipe that rotates in contact with a surface of the pressure rotating body; and a magnet disposed inside the heat pipe. 2. The heat pipe contacts the heating means and the pressure rotating body on the recording material discharge side of the pressure rotating body,
The image heating apparatus according to claim 1, wherein the image heating apparatus rotates in a direction opposite to a rotation direction of the pressure rotating body. 3. The image heating apparatus according to claim 1, wherein the magnet is provided in non-contact with an inner peripheral portion of the heat pipe. 4. The magnet according to claim 1, wherein the magnet is arranged in a direction intersecting a paper passing direction in an inner peripheral portion of the heat pipe, and magnetic poles are alternately arranged in a circumferential direction. 4. The image heating apparatus according to claim 1, wherein the image heating apparatus is arranged in a direction extending in a longitudinal direction of the pipe. 5. The magnet is provided with an N pole or an S pole at a position corresponding to the nip portion on an inner peripheral portion of the heat pipe, and is disposed in a direction extending in a longitudinal direction of the heat pipe. 2. The method according to claim 1, wherein
4. The image heating device according to any one of claims 1 to 3, wherein 6. An image forming apparatus comprising: image forming means for forming and carrying an unfixed toner image on a recording material; and a fixing device for thermally fixing the unfixed toner image to the recording material.
6. An image forming apparatus, wherein the fixing device is the image heating device according to claim 1.