JP2011145626A - Image heating device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the surface of a flexible sleeve from being shaved by the end of a recording material, and to prevent the occurrence of image-peeling, image-offsetting, or the like. <P>SOLUTION: In a heater 3, heat-generating resistors H6 and H7 are respectively provided so as to respectively and independently generate heat on both sides, in a longitudinal direction with respect to the center section of a nip part N in the longitudinal direction; and each time a preset number of recording materials pass through the nip part N, the heat-generating resistors H6 and H7 are made to alternately generate heat, in a state where a film 2 is rotated and in a state where the recording material is not conveyed being sandwiched at the nip part N, and where the viscosity of lubricant oil is reduced in an area made to generate heat. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer having a function of forming an image on a recording material such as a sheet, and more particularly to an image heating apparatus provided in these apparatuses.

The film heating type fixing device applied to the image forming apparatus can use a low heat capacity linear heating element as a heater and a thin film with a low heat capacity as a film as a flexible sleeve. Time shortening (quick start) is possible.
In the film heating type fixing device, there are two methods for driving the film. One is a system in which a film is transported between a pressure roller as a pressure member while applying tension using a dedicated roller for transporting the film and a driven roller. The other is a tensionless system in which the cylindrical fixing film is driven by the conveying force of the pressure roller by rotationally driving a pressure roller as a pressure member.
The former has the advantage that the transportability of the film can be increased, and the latter has the advantage that the apparatus configuration can be simplified and a low-cost apparatus can be realized. As a document disclosing related conventional examples, there is Patent Document 1.

JP 2007-240606 A

  By the way, in the heat fixing apparatus using a film, the film continues to rotate at a fixed position in the longitudinal direction. For this reason, when the recording material of the same size is continuously conveyed, the end portion of the recording material (hereinafter referred to as a paper edge portion) continues to contact at the same position in the longitudinal direction of the film surface, and the paper edge portion There is a concern that the film surface may be scraped. In the image forming apparatus described in Patent Document 1, since the recording material conveyance is based on one-side conveyance, one end of the recording material always abuts at the same position in the longitudinal direction of the film surface regardless of the size of the recording material. Will continue. When the surface of the film is scraped, the releasability is reduced, and paper dust or toner adheres to the film, resulting in film stains, and offsets and image stripping occur on the part. There is concern.

  The present invention has been made in view of the circumstances as described above, and suppresses the surface of the flexible sleeve from being scraped off by the end portion of the recording material, thereby suppressing the occurrence of image peeling or offset. With the goal.

In order to achieve the above object, the present invention provides:
A heater,
A flexible sleeve which is rotatably provided and slides on the heater;
Lubricating oil interposed in a sliding region between the heater and the flexible sleeve;
A pressure member that forms a nip portion with the heater via the flexible sleeve;
Have
In the image heating apparatus for sandwiching and conveying the recording material on which the developer image is formed between the flexible sleeve and the pressure member in the nip portion,
The heater is provided with at least one heating element on each side of the longitudinal direction with respect to the longitudinal central portion of the nip portion so as to be able to generate heat independently.
Each time a preset number of recording materials pass through the nip portion,
In a state where the flexible sleeve is rotating and the recording material is not nipped and conveyed by the nip portion,
At least one heating element located on one side in the longitudinal direction and at least one heating element located on the other side in the longitudinal direction are alternately caused to generate heat with respect to the central portion in the longitudinal direction of the nip portion. And a control means for reducing the viscosity of the lubricating oil in the heated region.

  According to the present invention, it is possible to suppress the surface of the flexible sleeve from being scraped by the end portion of the recording material, and it is possible to suppress the occurrence of image peeling or offset.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment. 1 is a cross-sectional view illustrating a schematic configuration of a fixing device according to an embodiment. 1 is a schematic diagram illustrating a fixing device according to an embodiment. FIG. 3 is a diagram for explaining Example 1; FIG. 6 is a diagram for explaining Example 2; FIG. 6 is a schematic diagram for explaining a configuration of a heater according to a third embodiment. FIG. 10 is a diagram illustrating the drive timing of the heater according to the third embodiment. FIG. 10 is a diagram showing the shifting force of the film of Example 3.

DETAILED DESCRIPTION Exemplary embodiments for carrying out the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.
The present invention relates to an electrophotographic image forming apparatus such as a printer, and more particularly to a technique for providing a high-quality image throughout the life without damaging the electrophotographic image forming apparatus.

<Image forming apparatus body configuration>
FIG. 1 is a cross-sectional view showing a schematic configuration of a laser beam printer (hereinafter referred to as a printer) 50 as an image forming apparatus of the present embodiment.
In the printer 50, 51 is an organic photosensitive drum (hereinafter referred to as photosensitive drum) as an image carrier, 52 is a charging roller as charging means, and 53 is a laser exposure apparatus. Reference numeral 54 denotes a developing sleeve, a developing blade, and a developing device composed of a one-component magnetic toner as a developer, 55 denotes a cleaning blade, 56 denotes a transfer roller, and 57 denotes a fixing device as an image heating device.
The photosensitive drum 51 is uniformly charged to a negative charge by the charging roller 52, and an electrostatic latent image is formed on the photosensitive drum 51 by the laser beam from the laser exposure device 53. Next, the toner T charged in the developing device 54 adheres to the electrostatic latent image on the photosensitive drum 51 to become a visible image (toner image as a developer image), and is transferred onto the recording material P on the transfer roller 56. Then, the image is fixed by the fixing device 57. The cleaning blade 55 removes the toner remaining on the photosensitive drum 51. An image is formed by the function of each unit described above. Here, the photosensitive drum 51, the charging roller 52, the laser exposure device 53, the developing device 54, and the transfer roller 56 constitute an image forming unit that forms a developer image on the recording material.

FIG. 2 is a cross-sectional view showing a schematic configuration of a tensionless film heating type fixing device of the present embodiment.
1 is a resin stay provided along the longitudinal direction, and an inner surface guide of an endless (endless) heat-resistant film (fixing film, hereinafter referred to as film) 2 as a flexible sleeve provided rotatably. It becomes a member. The film 2 circumscribes the stay 1 including the heater (heating body) 3 and is provided so as to slide on the heater 3. Reference numeral 4 denotes a thermistor for detecting the temperature of the heater 3. The inner peripheral length of the film 2 and the outer peripheral length of the stay 1 including the heater 3 are, for example, about 3 mm larger than that of the film 2. Is circumscribed loosely.

FIG. 3A is a schematic view of the fixing device 57 viewed from the upstream in the recording material conveyance direction.
The fixing flanges 21 and 24 support the inner peripheral surface of the end portion of the film 2 with support portions 22 and 25, and the end portion restricting members 23 and 26 restrict movement in the longitudinal direction. Since the length of the film 2 in the longitudinal direction is 240 mm and the distance between the regulating member 23 and the regulating member 26 is 246 mm, the support is regulated with a margin of 6 mm. Here, the longitudinal direction refers to the width direction of the recording material orthogonal to the recording material conveyance direction (the rotational axis direction of the pressure roller 6 described later, the rotational axis direction of the photosensitive drum 51).

On the inner peripheral surface of the film 2 (surface (region) that slides on the heater 3), grease as a lubricating oil is applied and present in order to improve slidability. In this embodiment, 500 mg of grease is uniformly applied on a heating resistor as a heating element provided in the heater 3 in an initial state (when the fixing device is assembled and shipped from the factory), so that the heater 3 and the film 2 are coated. It is interposed in the sliding area between. Since the heater 3 is a characteristic part in this embodiment, it will be described in detail later.
A pressure roller 6 as a pressure member (pressure rotator) is a silicone foam having a length of 240 mm and a thickness of 3 mm as a heat-resistant elastic layer on an aluminum core having an outer diameter of 13 mm connected to a driving device. The body is covered. The pressure roller 6 is configured to drive the film 2 by forming a nip portion (fixing nip portion) N by sandwiching the film 2 between the pressure roller 6 and the heater 3. The core bar material of the pressure roller 6 may be iron, stainless steel, or the like. The pressure roller 6 is configured to rotate when a driving force is transmitted from a driving motor provided in the driving device.
The recording material P on which the toner image T is formed (carrying the toner image) passes through the nip portion N formed by sandwiching the film 2 between the pressure roller 6 and the heater 3 (pinched by the nip portion N). (It is nipped and conveyed between the pressure roller 6 and the film 2 in the nip portion N)). As a result, the toner image T is heated and pressurized, and the toner image T is fixed on the recording material P.

The film 2 has a total thickness of about 100 μm or less in order to reduce the heat capacity and improve the quick start property. The film 2 is preferably composed of a single layer of PTFE, PFA, and FEP having heat resistance, releasability, strength, durability, and the like. Here, PTFE is polytetrafluoroethylene, PFA is a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, and FEP is a tetrafluoroethylene hexafluoropropylene copolymer.
The film 2 includes a base layer made of polyimide, polyamideimide, PEEK, PES, PPS, a primer layer as an adhesive layer provided on the outer peripheral surface of the base layer, and PTFE, PFA provided on the outer peripheral surface. It may be composed of a release layer containing as a main component. Here, PEEK is polyetheretherketone, PES is polyethersulfone, and PPS is polyphenylene sulfide.
In order to increase the thermal conductivity of the film 2 itself, a filler such as boron nitride, aluminum nitride, or carbon fiber is blended. A heat conductive filler can be mix | blended with any layer or all the layers of a base layer, a primer layer, or a top layer (release layer). The film in this example has an outer diameter of 18 mm, polyimide is used for the base layer, the thickness is 60 μm, the primer layer is 6 μm made of fluororesin and carbon, the top layer is 15 μm made of PFA and PTFE, and the total film thickness is 81 μm. It becomes a three-layer structure.

<Heater configuration>
Next, the configuration of the heater 3 that is a feature of the present embodiment will be described. FIG. 3B is a schematic diagram for explaining the configuration of the heater 3.
The heater 3 is a planar heater, and includes a planar substrate H1 having good thermal conductivity as a substrate. On the planar substrate H1 (on the substrate), electrode patterns H2 and H3, strip-shaped heating resistors H6, power feeding patterns H8 and H9 are provided, and further, the electrode patterns H4 and H5, strip-shaped heating resistors. A body H7 and power supply patterns H10 and H11 are provided.
Here, the electrode patterns H2 and H3 are connected to a power source. The heating resistor H6 is printed and fired on the planar substrate H1. The power supply pattern H8 has one end connected to the electrode pattern H3 and the other end connected to the heating resistor H6. The power supply pattern H9 has one end connected to the electrode pattern H2 and the other end connected to the heating resistor H6. The electrode patterns H4 and H5 are connected to a power source. The heating resistor H7 is printed and fired on the planar substrate H1. The power supply pattern H10 has one end connected to the electrode pattern H4 and the other end connected to the heating resistor H7. The power supply pattern H11 has one end connected to the electrode pattern H5 and the other end connected to the heating resistor H7. The heating resistors H6 and H7 are arranged side by side in the longitudinal direction of the planar substrate H1 and generate heat when energized (power is supplied), and are provided so as to be able to generate heat independently.

  In other words, the heating resistor of the present embodiment is configured to include two heating resistors that can be driven independently on the left and right. H12 is an insulating protective layer such as glass that covers the power feeding pattern and the heating resistor. In this embodiment, the glass layer is covered.

<Heating resistor drive timing>
Next, a driving (operation) method of the heater 3 having two independent heating resistors will be described.
The timing for driving only one independent heating resistor is a state in which the film 2 is rotating, and the recording material P does not pass through the nip portion N (not pinched and conveyed by the nip portion N). It is. When the recording material P is rotated before reaching the temperature control to be fixed, or while the recording material passes through the nip portion, the two heating resistors are driven. By causing only one heating resistor to generate heat at the above timing, the viscosity of the grease on the side where heat is generated is reduced, and in the film 2, a shearing force acts on the side where the viscosity of the grease is reduced.
This is due to the following actions. The grease on the side where the heating resistor generates heat becomes soft as the viscosity decreases. On the other hand, since the viscosity of the grease on the side where the heating resistor does not generate heat does not change, it remains harder than the grease on the side where the heating resistor generates heat. As a result, the sliding resistance between the heater 3 and the stay 1 and the film 2 becomes smaller on the side where the heating resistor generates heat than on the side where the heating resistor does not generate heat. Will be improved. When the film 2 rotates in such a state, a force that tries to move (moves) in a direction in which the film 2 easily rotates is exerted on the film. In this way, a biasing force acts on the film 2 in the direction where the viscosity of the grease is lowered.
In this way, the film 2 approaches the side on which the heating resistor generates heat. The heater 3 is driven by a power supply unit that supplies power to the heating resistor by a control unit provided in the image forming apparatus.

<Example 1>
Using the configuration as described above, an experiment for confirming the state of the film 2 and the level of dirt on the film 2 was performed.

(Experimental conditions)
[Environment] 15 ° C., 10% R.D. H.
[Image forming apparatus body] [Process speed] 80 mm / s based on Laserjet 1020 manufactured by HP (Hewlett-Packard Company)
[Passing paper] Sanichigo (product name) 70 g / m ² papers [Number of passing papers] 50000 sheets Continuous feeding [heater heating resistor drive timing]
(1) Passing 100 sheets (2) Stopping for 2 seconds (3) Empty rotation for 10 seconds-Heat generation resistor H7 generates heat during idle rotation (4) Stop for 2 seconds (5) Passing 100 sheets (6) 2 seconds Stop (7) idle rotation for 10 seconds-heat generation resistor H6 generates heat during idle rotation (8) stop for 2 seconds The above (1) to (8) were repeated until 50,000 sheets were passed (conveyed).
FIG. 4A is a diagram illustrating the drive timing of the heaters (1) to (8).

[Configuration of measurement system]
A piezoelectric element is provided at the flange portion at the end of the film 2, and the pressure (film offset force) when it abuts against the flange is measured. FIG. 4B shows the shifting force of the film 2 measured at that time. In the figure, the vertical axis represents the offset force of the film 2 and 1 gf = 9.8 mN.
As a comparative example, an image forming apparatus equipped with a heater having a single heating resistor in the longitudinal direction and a fixing device that does not allow film shift control was checked for the shift force of film 2 and the level of dirt on the film.
Table 1 shows the results of confirming contamination on the film in Example 1 and Comparative Example 1.

As for Comparative Example 1, 15,000 sheets were stained on the surface of the film 2 at the contact position of the paper edge. This is due to the fact that the edge of the paper passes through the same position on the film because the position of the film is at the same place in the longitudinal direction throughout the durability. Since the paper edge passes through the same position on the film, the film surface is scratched by rubbing with the paper edge portion, and paper dust and toner adhere to that part and appear as dirt.
Regarding Example 1, the stain on the film 2 did not occur up to 50,000 sheets. This is because the film 2 moves in the direction in which the heat generating resistor generates heat by causing the heat generating resistors that are independently provided in the longitudinal direction to generate heat one by one every 100 sheets. This is because there is no constant contact with the same place.

  From FIG. 4 (b), it can be seen that the shifting force of the film 2 toward the heated side is generated when the shifting force of the film 2 during idling where only one side is heated is observed. As a result, the film 2 repeatedly moves left and right (reciprocating in the longitudinal direction), so that the surface of the film 2 is less likely to be scratched and the occurrence of dirt can be suppressed.

As described above, in this embodiment, every time a predetermined (preset) number of recording materials pass through the nip portion N, two heating resistors independent in the longitudinal direction are heated one by one at a predetermined timing. By doing so, the viscosity of the lubricating oil in the heated region is lowered. Here, the predetermined timing is a timing when the film 2 is rotating and the recording material P is not being nipped and conveyed by the nip portion N.
As a result, it is possible to generate a shift force in the longitudinal direction on the film 2, move the film 2, and shift the position in the longitudinal direction, thereby preventing scraping at the paper edge portion on the surface of the film 2, It is possible to prevent the occurrence of an offset or the like.

<Example 2>
In the second embodiment, only the heating resistor driving timing of the heater 3 is changed, and the other configuration is the same as that of the first embodiment. Therefore, detailed description of the same components as those of the first embodiment is omitted.
In this example, the state of the film 2 when the sheet was intermittently passed through 50000 sheets and the stain level on the film 2 were confirmed. The driving timing of the heating resistor in this embodiment is as follows.
(1) Pass one sheet (2) Turn the heating resistor H7 10 seconds later (3) Stop 2 seconds (4) Pass the sheet 1 (5) Turn 10 seconds later and heat the heating resistor H6 .
(6) Stop for 2 seconds The above (1) to (6) were repeated until 50,000 sheets were passed.

Fig.5 (a) is a figure which shows the drive timing of the heater of (1)-(6). FIG. 5B is a diagram showing the offset force of the film 2.
Also in this example, no stain on the film 2 occurred up to 50,000 sheets. This is because the film 2 moves in the direction in which the heating resistor generates heat by heating two heating resistors independently provided in the longitudinal direction for each intermittent print. This is because there is no constant contact with the same place in FIG.
From FIG. 5 (b), it can be seen that the shifting force of the film 2 toward the heated side is generated when the shifting force of the film 2 during idling where only one side is heated is observed. As a result, the film 2 repeatedly moves left and right (reciprocating in the longitudinal direction), so that the surface of the film 2 is less likely to be scratched and the occurrence of dirt can be suppressed, and the same effect as in Example 1 can be obtained. it can.

<Example 3>
Example 3 has a configuration in which the heater 3 has three heating resistors in the longitudinal direction, and the experimental conditions other than the heater heating resistor driving timing are the same as in Example 1, and the same as in Example 1. A description of the components is omitted. FIG. 6 is a schematic diagram for explaining the configuration of the heater 3 of the present embodiment.

In the present embodiment, as shown in FIG. 6, the heater 3 includes a planar substrate H51 having good thermal conductivity. On the planar substrate H51, electrode patterns H52, H53, H54, H55, H56, H57, power supply patterns H61, H62, H63, H64, H65, H66, heating resistors (patterns) H58, H59, H60 are provided. Is provided. These power feeding pattern and heating resistor are covered with a glass layer H67 which is an insulating protective layer. The three heating resistors H58, H59, and H60 are juxtaposed in the longitudinal direction of the planar substrate H51 and generate heat when energized, and can be driven independently. Normally, the three heating resistors H58, H59, and H60 are heated when power is supplied to the three heating resistors at the same time when normal A4 size or letter size paper is passed through, such as envelopes and postcards. When a narrow sheet of paper is passed, control is performed so that the non-passed portion does not generate heat. That is, as a countermeasure against temperature increase in the non-sheet passing portion, when a narrow paper such as an envelope or a postcard is passed, power is not supplied to the heating resistors H58 and H60, and power is supplied only to the heating resistor H59. To generate heat.

In this embodiment, when the recording material is not passed, only the heating resistor H58 or only the heating resistor H60 is independently driven to control the fixing film in one direction.
In the present embodiment, the state of the fixing film when the sheet is continuously fed through 50,000 sheets and the level of dirt on the fixing film were confirmed. The drive timing of the heating resistor in this embodiment is as follows.
(1) Passing 100 sheets (2) Stopping for 2 seconds (3) Empty rotation for 10 seconds-Heating the heating resistor H58 during idle rotation (4) Stopping for 2 seconds (5) Passing 100 sheets (6) 2 seconds Stop (7) idle rotation for 10 seconds-heat generation resistor H60 generates heat during idle rotation (8) stop for 2 seconds The above (1) to (8) were repeated until 50,000 sheets were passed.
FIG. 7 is a diagram illustrating the drive timing of the heaters (1) to (8). FIG. 8 is a diagram showing the offset force of the film 2.

In this example, no stain on the film 2 occurred up to 50,000 sheets. This is because the heating resistors present at both ends in the longitudinal direction among the heating resistors provided independently in the longitudinal direction for every 100 sheets are each independently heated to generate a film in the direction in which the heating resistors generate heat. This is because 2 moves. Thereby, the paper edge portion does not always come into contact with the same place on the film 2.
From FIG. 8, it can be seen that the shifting force of the film 2 to the heated side is generated when the shifting force of the film 2 during idling where only one side is heated is observed. As a result, the film 2 repeatedly moves left and right (reciprocating in the longitudinal direction), so that the surface of the film 2 is hardly scratched and the occurrence of dirt can be suppressed.

As described above, in this embodiment, every time a predetermined number of recording materials pass through the nip portion N, the heating resistors provided at both ends in the longitudinal direction among the plurality of heating resistors are provided at a predetermined timing. Heat is alternately generated one by one to reduce the viscosity of the grease. Here, the predetermined timing is a timing when the film 2 is rotating and the recording material P is not being nipped and conveyed by the nip portion N.
In the film 2, since the shearing force works in the direction in which the viscosity of the grease decreases, the film 2 repeats reciprocation in the longitudinal direction, so that the surface of the film 2 is hardly scratched and the occurrence of dirt can be suppressed. The same effect as in Example 1 can be obtained.

In the first and second embodiments, the configuration in which the heater 3 has two heating resistors in the longitudinal direction will be described. In the third embodiment, the configuration in which the heater 3 has three heating resistors in the longitudinal direction will be described. However, it is not limited to this.
The heater 3 according to the present embodiment is not limited as long as at least one heating resistor is provided on each side of the longitudinal direction with respect to the longitudinal center of the nip portion N so as to be able to generate heat independently. . In this case, any heating resistor may be used as long as it generates heat as follows. That is, for every predetermined number of sheets, at least one heating resistor located on one side (one end side) in the longitudinal direction with respect to the center portion in the longitudinal direction of the nip portion N, and the other side in the longitudinal direction (the other end) Any one may be used as long as it heats at least one heating resistor located on the side) alternately. Here, the heater only needs to be provided with at least one heating resistor on each side in the longitudinal direction with respect to the longitudinal center of the nip portion N. For example, in a region on one side or the other side in the longitudinal direction, a plurality of heating resistors may be provided sequentially (in parallel) in the longitudinal direction, and a plurality of heating resistors in order in the recording material conveyance direction. May be provided. Thereby, the film 2 can be reciprocated in the longitudinal direction, and the surface of the film 2 is less likely to be scratched and the occurrence of dirt can be suppressed.
In the above-described embodiment, the heating resistor on one side in the longitudinal direction and the other side in the longitudinal direction are alternately heated for every predetermined number of sheets, but the measurement of the predetermined number is actually passed. The number of recording materials may be measured, or it may be equivalent to this. For example, it may be an integrated value of the operation time of the fixing device (the time during which the heating resistor is energized for the fixing operation). The predetermined number of sheets may be set as appropriate according to the material, thickness, etc. of the recording material.
Further, the image heating apparatus according to the present invention is not limited to the example in the case of functioning as the above-described fixing device, and can also be applied as an apparatus for giving gloss to a toner image fixed on a sheet. .

2 Film 3 Heater 6 Pressure roller 57 Fixing device H6, H7 Heating resistor N Nip part P Recording material T Toner image

Claims (2)

A heater,
A flexible sleeve which is rotatably provided and slides on the heater;
Lubricating oil interposed in a sliding region between the heater and the flexible sleeve;
A pressure member that forms a nip portion with the heater via the flexible sleeve;
Have
In the image heating apparatus for sandwiching and conveying the recording material on which the developer image is formed between the flexible sleeve and the pressure member in the nip portion,
The heater is provided with at least one heating element on each side of the longitudinal direction with respect to the longitudinal central portion of the nip portion so as to be able to generate heat independently.
Each time a preset number of recording materials pass through the nip portion,
In a state where the flexible sleeve is rotating and the recording material is not nipped and conveyed by the nip portion,
At least one heating element located on one side in the longitudinal direction and at least one heating element located on the other side in the longitudinal direction are alternately caused to generate heat with respect to the central portion in the longitudinal direction of the nip portion. An image heating apparatus comprising a control means for reducing the viscosity of the lubricating oil in the heated area. Image forming means for forming a developer image on the recording material;
An image heating apparatus according to claim 1;
With
An image forming apparatus, wherein the developer image formed on the recording material by the image forming means is heated by the image heating device.

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