JP2000162907A - Image heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating element, and a film having one surface sliding with the heating element and the other surface being in contact with and moving together with a recording material carrying an image. In an image heating device that heats the image on the recording material by the heat from the heating element, preventing poor heating at the edge of large-size paper and twisting of the film after passing small-size paper, increasing the throughput, regardless of the usage environment After passing the small-size paper, the large-size paper is heated to the end portion in a predetermined manner. SOLUTION: A heating body 11 heats a large-size recording material heating element 11b1 for heating a recording material having a maximum sheet passing width A and a small-size recording material heating element for heating a recording material narrower than the recording material having a maximum sheet passing width. The heating element for the small-size recording material has a heating element 11b2 of the paper-passing portion B at the outside of the paper-passing portion C of the small-size recording material.
The heat-generating units outside the paper-passing unit 11b3 and 11 have a heat generation amount per unit length smaller than that of the heat-generating unit, and have a heat-generating distribution such that the temperature distribution in the longitudinal direction of the heater when the small-size recording material passes is substantially uniform.
b3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film heating type image heating apparatus and an image forming apparatus provided with the image heating apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copying machine, and a facsimile, a recording material (transfer material, photosensitive paper,
As a device for heating and fixing an unfixed image (toner image) formed and supported by a transfer (indirect) method or a direct method on electrostatic recording paper, printing paper, etc., a heat roller type device is widely used. .

A heat roller type apparatus has a fixing roller (heat roller, heat roller) as a fixing member and a pressing roller as a pressing member, which are rotated while being pressed against each other. Fixing nip (heating nip)
An unfixed image is formed and carried on the recording material, and the sheet is nipped and conveyed, whereby the unfixed image is heated and fixed as a permanently fixed image on the recording material surface by the heat of the fixing roller and the pressing force of the fixing nip portion. Things.

Recently, from the viewpoint of promoting energy saving,
2. Description of the Related Art A film heating type apparatus has been put to practical use as an on-demand image heating apparatus having a high heat transfer efficiency and a quick start-up of the apparatus.

This is described, for example, in Japanese Patent Application Laid-Open No. 63-313182.
JP-A-2-1577878, JP-A-4-440
Nos. 75-44083, 4-204980-204
No. 984, etc., in which a fixedly supported heating element, a heat-resistant film that slides on the heating element, and a pressure for forming a fixing nip by pressing the heating element with the film interposed therebetween. The heating element is heated and controlled to a predetermined temperature, and a recording material on which an unfixed image is formed and supported is introduced between the film at the fixing nip and the pressing member, and is fixed together with the film. By nipping and transporting the nip, the unfixed image is heated and fixed as a permanently fixed image on the recording material surface by the heat from the heating body via the film and the pressing force of the fixing nip.

In such a film heating type image heating apparatus, a linear heating element having a low heat capacity, such as a so-called ceramic heater, is used as a heating element, and a thin heat-resistant film having a low heat capacity is used as a heat transfer member. As a result, the temperature of the heating element can be raised in a short time and the heating element or the fixing nip can quickly rise to a predetermined temperature. Therefore, power is not supplied to the apparatus (heating element) during standby.
The power consumption can be reduced as much as possible, the power consumption can be reduced and the wait time can be shortened (quick start property) as compared with other image heating apparatuses such as a heat roller method, and an on-demand image heating apparatus can be configured. be able to.

FIG. 9 is a schematic configuration diagram of a main part of an example of a film heating type image heating apparatus (heating fixing apparatus).

That is, a stay holder (heater support) 1
2, a heater 11 (hereinafter referred to as a heater) fixedly supported on the heater 2, and a heat-resistant thin film 13
An elastic pressure roller 20 is formed by forming a fixing nip portion N having a predetermined nip width with a fixing nip portion N interposed therebetween (hereinafter referred to as a fixing film).

The heater 11 is heated and adjusted to a predetermined temperature by energization.

The fixing film 13 is a cylindrical member, an endless belt member, or a rolled endless web member.
Of the heater 1 in the fixing nip N
The sheet is conveyed and moved in the direction of arrow a while closely contacting and sliding on one surface.

The heater 11 is heated and controlled to a predetermined temperature, and the fixing film 13 is conveyed and moved in the direction of arrow a. When a recording material P on which an unfixed toner image t is formed and supported as a material to be heated is introduced, the recording material P comes into close contact with the surface of the fixing film 13 and is fixed to the fixing film 1.
The fixing nip N is conveyed together with the fixing nip N.

In the fixing nip N, the recording material P
The toner image t is transferred to the fixing film 13 by the heater 11.
And the toner image t on the recording material P is heated and fixed.

The recording material passing through the fixing nip N is peeled off from the surface of the fixing film 13 and conveyed.

As the heater 11, a ceramic heater is generally used. FIG. 10 (a) is a partially cutaway plan view of the front side (heating side) of an example of the ceramic heater 11, and FIG. 10 (b) is a plan view of the back side (anti-heating side).

That is, for example, an electric insulating property such as alumina
A heat-generating resistance layer (heat generation) of silver palladium (Ag / Pd), Ta ₂ N, etc., on the surface side (the surface facing the fixing film 13) of the ceramic substrate 11a having good thermal conductivity and low heat capacity along the substrate length. Body 11b is formed by screen printing or the like, and the surface on which the current-generating resistance layer is formed is covered with a thin glass protective layer 11c. In the heater 11, when electricity is supplied from the power supply electrode portion 11d, the energized heating resistor layer 11b generates heat, and the entire heater rapidly rises in temperature.

The temperature rise of the heater 11 is detected by a temperature detecting means 14 disposed on the back surface of the heater 11 and is not shown via an electric circuit pattern 11e, a through hole 11f, and an electrode 11g for output to a temperature controller. This is fed back to the energization control unit.

The power supply control unit controls the power supply to the power supply heating resistor layer 11b so that the heater temperature detected by the temperature detecting means 14 is maintained at a predetermined substantially constant temperature (fixing temperature). That is, the heater 11 is heated and adjusted to a predetermined fixing temperature.

The thickness of the fixing film 13 is as small as 20 to 70 μm in order to efficiently apply the heat of the heater 11 to the recording material P as a material to be heated in the fixing nip portion N. The fixing film 13 has a three-layer structure including a film base layer, a primer layer, and a release layer. The film base layer side is the heater 11 side, and the release layer side is the pressure roller 20 side. Film base layer is heater 1
A polyimide having a higher insulating property than the glass protective layer 11c,
Polyamide imide, PEEK, etc., having heat resistance and high elasticity. Further, the mechanical strength such as the tear strength of the entire fixing film 13 is maintained by the film base layer. The primer layer is formed as a thin layer having a thickness of about 2 to 6 μm. The release layer is a toner offset prevention layer for the fixing film 13, and is formed by coating a fluororesin such as PFA, PTFE, FEP or the like to a thickness of about 10 μm.

The stay holder 12 is formed of, for example, a heat-resistant plastic member and holds the heater 11 and also serves as a conveyance guide for the fixing film 13.

In such a heating apparatus of the film heating type using the thin film 13 for fixing, the pressing roller 20 having an elastic layer due to the high rigidity of the ceramic heater 11 applies the film 13 to the film 13. Following the flat lower surface of the heater 11 brought into pressure contact with the heater, the flattened portion is formed at the pressure contact portion to form a fixing nip portion N having a predetermined width, and only the fixing nip portion N is heated, thereby realizing the heat fixing of the quick start. are doing.

S is a recording material conveyance standard (paper passing standard),
In the case of the apparatus of this example, the apparatus is a “center reference” apparatus in which a reference is provided at the center in the longitudinal direction of the recording material conveyance area of the image forming apparatus main body.

The width of the heating resistor layer 11b of the heater 11 in the longitudinal direction, that is, the effective heating area W is determined by the fixing film 13
The width of the elastic layer of the pressure roller 20 that is brought into contact with the heater 11 through the pressure roller 20 is slightly smaller than the width D (the pressure roller contact area). This is to prevent the energized heating resistance layer 11b from locally rising due to protruding from the pressing roller 20 and being damaged by the thermal stress.

The effective heat generating area W of the current-carrying resistance layer 11b is formed to have a width sufficiently larger than the maximum width of the recording material conveyance area that can be used for the apparatus, that is, the large-size paper passing section A. This can eliminate the influence of the end temperature droop (due to heat leak to the electrical contacts at the end of the heater 11 and the connectors 31 and 32), thereby providing good fixing performance over the entire surface of the recording material P. Is obtained.

Further, an electric heating resistor layer 11b at the end of the paper passing area.
In some cases, the width of the edge is narrowed to increase the amount of heat generated at the ends, thereby compensating for the fixability at the ends.

As a result, the heat generated by energizing the energizing heating resistance layer 11b of the heater 11
3 is applied to the recording material P conveyed between the pressure roller 3 and the pressure roller 20, and acts to melt and fix the toner image t on the recording material P.

On the back side of the heater 11, a temperature detecting element 14 such as a thermistor and a thermoprotector 15 such as a temperature fuse or a thermoswitch for shutting off the power supply to the current-carrying resistance layer 11b of the heater 11 when runaway occurs. These temperature sensing elements 1
The thermo-protector 4 and the thermoprotector 15 are arranged in a conveyance area B of a recording material P having a minimum width that can be conveyed by the image forming apparatus, that is, in a small-size paper passing portion (a recording material minimum width conveyance area). The thermo protector 15 is interposed in series with a power supply line for the current-carrying resistance layer 11b.

Here, with respect to the temperature detecting element 14, even when the recording material P having the minimum width that can be conveyed by the image forming apparatus main body is conveyed, the toner image t on the recording material P is not fixed properly, In order to heat and fix at an appropriate fixing temperature without causing a problem such as offset, it is provided in the small-size paper passing portion B.

On the other hand, also when the recording material P having the minimum width is conveyed, the thermoprotector 15 is moved from the small-size paper passing portion B which is the conveying region in the non-conveying region, that is, the small-size paper non-passing portion C. The overheating is performed in the small-size paper non-transporting area C where the thermal resistance is small. It is provided in the paper passing section B.

By bringing the thermoprotector 15 into contact with the back surface of the heater 11, the heat generated in the current-carrying resistance layer 11b is taken away by the thermoprotector 15, so that the recording material P is not given a sufficient heat. A fixing failure may occur at the contact position of the protector 15. In order to prevent this, the heat generating resistance layer 11b
In the position corresponding to the thermoprotector contact, the width is slightly narrowed like 11b ', and the resistance of the energized heating resistor layer 11b' is made larger than that of the other energized heating resistor layers to secure the heat generation. . As a result, the amount of heat supplied to the recording material P is kept constant in the longitudinal direction of the heater, and good heat fixing without fixing unevenness is realized.

Since the temperature detecting element 14 is also brought into contact with the back surface of the heater 11 similarly to the thermoprotector 15, the heat generated by the energized heat generating resistance layer 11b is similarly taken by the temperature detecting element 14. However, by using the temperature detecting element 14 having a small heat capacity such as a chip thermistor, the amount of heat taken from the heater 11 can be reduced. For this reason, even if the same countermeasures as those of the thermoprotector 15 are not taken, uniform fixing can be performed without impairing the fixing uniformity of the recording material in the longitudinal direction of the heater.

[0031]

In a film heating type image heating apparatus as shown in the above-mentioned conventional example, when a recording material having a small paper width (small size paper) is continuously passed, a small size paper passing section is required. Although the temperature of B is adjusted to a predetermined value, the temperature of the small-size paper non-sheet passing portion C in which the heat is not deprived by the paper gradually increases as the continuous paper is passed (non-sheet passing portion temperature rising phenomenon). Eventually, the heater, the stay holder, the pressure roller and the like may be melted or damaged.

Therefore, when passing small-size paper,
By lowering the throughput, the temperature rise and the heat radiation of the small-size paper non-sheet passing portion C are balanced so that the temperature does not rise above a certain temperature.

However, due to an increase in fixing temperature and an increase in input power due to the recent increase in the speed of the printer, the temperature of the non-sheet passing portion C of the small-size paper increases sharply. The throughput when passing small-size paper must be further reduced.

In order to solve the above-mentioned problem, a method has been attempted in which a plurality of heating elements (conduction heating layers) corresponding to the paper size are provided in the heater and the heating area of the heater is changed according to the paper size. ing.

However, when the heating and fixing is performed by the heating element according to the paper size as described above, the temperature of the heater in the non-paper passing portion during the passing of the small size paper remains low.
When passing normal-size paper after passing small-size paper, a fixing failure may occur at the position corresponding to the non-paper passing area of the small-size paper, or wait until the edge temperature rises to fix the entire surface. Needed.

In a device driven by a pressure roller,
Due to the difference in the outer diameter of the pressure roller due to the temperature difference between the pressure roller and the non-paper-passing part, a difference occurs in the film feed speed in the longitudinal direction of the fixing nip, which may cause film twisting. is there.

Accordingly, the present invention is directed to an image heating apparatus of a film heating type and an image forming apparatus provided with the image heating apparatus, which solves the above-mentioned problems and solves the problem of the end of a large-size paper sheet after passing a small-size paper sheet. It is possible to prevent poor heating and twisting of the film, and at the same time, increase the throughput.Moreover, it is possible to heat the large-size paper after the small-size paper is passed to the outermost end regardless of the use environment. The purpose is to be able to.

[0038]

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

(1) having a heating element and a film having one surface sliding on the heating element and the other surface moving in contact with the recording material bearing the image; In the image heating apparatus for heating an image on a recording material by heat of the recording material, the heating element includes a heating element for a large-size recording material that heats a recording material having a maximum sheet passing width, and a recording element having a width narrower than the recording material having a maximum sheet passing width. A heating element for the small-sized recording material for heating the recording material, wherein the heating element for the small-sized recording material has a calorific value per unit length outside the paper-passing portion of the small-size recording material more than the heating element in the paper-passing portion; An image heating apparatus comprising: a heating element outside the sheet passing portion having a small heat generation and a heat generation distribution such that a temperature distribution in a longitudinal direction of the heating element when a small-sized recording material is passed is substantially uniform.

With this apparatus configuration, it is possible to prevent a heating failure at the end of a large-sized paper and a twisting of a film after the small-sized paper is passed.

(2) A mode of heating the image on the recording material by turning on the large-sized recording material heating element and the small-sized recording material heating element of the heating element at a predetermined lighting ratio. The image heating apparatus according to (1).

With this apparatus configuration, it is possible to prevent a large-sized paper end portion from being insufficiently heated after the small-sized paper is passed or to prevent the film from being twisted. The throughput of the recording material of the size can be increased.

(3) In the heating element outside the sheet passing portion of the heating element for small-size recording material, the amount of heat generation per unit length is larger at the end than in (1) or (2). The image heating device according to claim 1.

With this apparatus configuration, it is possible to prevent the large-sized paper end from being heated poorly and the film from being twisted after the small-sized paper is passed, and to remove the large-sized paper after passing the small-sized paper to the extreme end regardless of the use environment. The part can be heated to a predetermined value.

(4) The image heating apparatus according to any one of (1) to (3), further comprising a pressure member for forming a heating nip by pressing the heating body with a film interposed therebetween.

(5) In an image forming apparatus having an image forming means for forming an unfixed image on a recording material and a heat fixing means for fixing the unfixed image as a permanent image on the recording material, the heat fixing means is An image forming apparatus, which is the image heating apparatus according to any one of (1) to (4).

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (FIGS. 1 to 5) (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 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier. OP
A photosensitive material layer of C, amorphous Se, amorphous Si or the like is formed on a cylindrical conductive substrate of aluminum or nickel. The photosensitive drum 1 is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed).

In the rotation process, first, the photosensitive drum 1
The surface is uniformly charged to a predetermined polarity and potential by a charging roller 2 as a charging device.

Next, a laser beam scanning exposure 3 corresponding to a target image information pattern is received by a laser scanner (not shown) as an exposure device. As a result, an electrostatic latent image corresponding to the target image information pattern is formed on the surface of the rotating photosensitive drum 1.

The laser scanner outputs a laser beam whose ON / OFF is controlled in response to a time-series electric digital pixel signal of an image information pattern sent from an external device or the like such as a host computer. 1 is uniformly exposed to scanning.

The electrostatic latent image formed on the surface of the rotating photosensitive drum 1 is visualized by developing the toner in the developing device 4. Development methods include a jumping development method, a two-component development method, and F
An EED development method or the like is used, and a combination of image exposure and reversal development is often used.

The toner image formed on the surface of the rotating photosensitive drum 1 is transferred to a transfer nip portion T formed by the photosensitive drum 1 and a transfer roller 5 as a transfer device brought into contact with the photosensitive drum 1 with a constant pressure. The image is sequentially transferred to a recording material (transfer material) P fed from a paper supply unit (not shown) to the transfer nip portion T at a predetermined control timing.

A predetermined transfer bias is applied to the transfer roller 5 from a power supply (not shown) at a predetermined control timing, and the toner image on the surface of the photosensitive drum 1 is acted upon by the transfer bias.
The transfer nip portion T is sequentially transferred to the surface of the recording material P which is nipped and conveyed.

The recording material P, which has received the transfer of the toner image at the transfer nip T and passed through the transfer nip T, is separated from the surface of the rotating photosensitive drum 1 and is conveyed to a fixing device 6 as an image heating device. The image is fixed as a permanent image.

On the other hand, the transfer residual toner remaining on the photosensitive drum 1 is removed from the surface of the photosensitive drum 1 by the cleaning device 7.

The process speed of the image forming apparatus in this embodiment is 151 mm / s, and the throughput is 24 p.
pm (A4).

(2) Fixing Device 6 The fixing device 6 as the image heating device in this embodiment is a film heating system using a cylindrical fixing film and pressure disclosed in JP-A-4-44075-44083. This is a roller-driven, tensionless type heat fixing device.
FIG. 2 is a schematic cross-sectional view of the device 6.

Reference numerals 10 and 20 denote a fixing member and a pressure member which are in contact with each other to form a fixing nip N.

The fixing member 10 includes a heating element 11 (hereinafter, referred to as a heater), a heat insulating stay holder 12, a fixing film 13, and the like. The pressure member 20 is an elastic pressure roller.

The heater 11 is made of Al ₂ O having high thermal conductivity.
_A thin and horizontally long ceramic heater made of ₃ or AlN substrate. In this embodiment, a backside heating type ceramic heater was used. The heater 11 will be described in detail in the following section (3).

The heat insulating stay holder 12 is
1 to prevent heat radiation in the direction opposite to the fixing nip portion N. The liquid crystal polymer, phenol resin, PPS,
It is formed of PEEK or the like. The heat-insulating stay holder 12 of this example has a substantially semicircular trough-shaped trough shape in cross section, and has heat resistance,
The heater 11 is electrically insulative and can withstand a high load. The heater 11 is fitted into a groove provided along the longitudinal direction of the member at substantially the center of the lower surface of the heat-insulating stay holder 12 with its front side exposed downward. It is fixed and supported.

The fixing film 13 is a cylindrical heat-resistant film, and the heat insulating stay holder 1 including the heater 11 is provided.
The heat-insulating stay holder 12 supports the fixing film 13 from the inner surface by loosely fitting the outer periphery of the fixing film 13 with a margin in the circumference.

The fixing film 13 has a small heat capacity, and has a total thickness of 100 to enable quick start.
Heat-resistant, thermoplastic polyimide, polyamideimide, PEEK, PES, PPS, P
It is a film based on FA, PTFE, FEP or the like. In addition, a film having sufficient strength to constitute a long-life heat fixing device and having excellent durability has a total thickness of 2 mm.
A thickness of 0 μm or more is required. Therefore, fixing film 1
The total thickness of 3 is optimally 20 μm or more and 100 μm or less. Further, in order to prevent offset and ensure the separating property of the recording material, the surface layer is coated with a heat-resistant resin having good releasability, such as PFA, PTFE, FEP, or silicone resin, or coated alone.

The elastic pressure roller 20 as a pressure member is
A core metal 21 and an elastic layer 22 formed by foaming heat-resistant rubber such as silicon rubber or fluorine rubber or silicon rubber on the outside of the core metal 21, and PFA, PRF
A release layer 23 such as E or FEP may be formed.

The elastic pressure roller 20 is held by a bearing member (not shown), and the fixing film 13 is sandwiched between the downward surface of the heater 11 fixed and supported on the lower surface side of the heat insulating stay holder 12. The pressure is sufficiently applied from both ends in the longitudinal direction to form a fixing nip portion N required for heat fixing by the illustrated pressing means.

The pressure roller 20 is driven to rotate in a counterclockwise direction indicated by an arrow by driving means (not shown). This pressure roller 2
0, a rotational force is applied to the fixing film 13 by a press-contact frictional force at the fixing nip portion N between the outer surface of the roller 20 and the outer surface of the fixing film 13 due to the rotation of the fixing film 13. Heater 1 in N
The outer peripheral surface of the heat insulating stay holder 12 is driven to rotate in a clockwise direction indicated by an arrow at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 20 while sliding in close contact with the downward surface of the stay 1.

In this case, the cylindrical fixing film 13 that is driven to rotate around the outer periphery of the heat insulating stay holder 12 has a fixing free nip portion N having a peripheral length and a fixing film portion other than the fixing film portion near the fixing nip portion N. (Not added).

Since the inner surface of the fixing film 13 rotates while rubbing a part of the outer surface of the heater 11 and the heat insulating stay holder 12, the frictional resistance between the heater 11 and the heat insulating stay holder 12 and the fixing film 13 is reduced. It needs to be kept small. Therefore, a small amount of a lubricant such as heat-resistant grease is interposed between the surfaces of the heater 11 and the heat insulating stay holder 12. Thus, the fixing film 13 can rotate smoothly.

Thus, the pressure roller 20 is driven to rotate,
Accordingly, the cylindrical fixing film 13 is driven to rotate around the outer periphery of the heat insulating stay holder 12, and electricity is supplied to the heater 11, and the heat of the heater 11 causes the temperature of the fixing nip N to rise to a predetermined value, thereby increasing the temperature. In the adjusted state, the recording material P on which the unfixed toner image t is formed and carried is introduced into the fixing nip N, and the unfixed toner image carrying surface side of the recording material P is fixed to the outer surface of the fixing film 13 in the fixing nip N. The fixing nip N is conveyed while being held in contact with the fixing film 13.

In the process of nipping and transporting the recording material P, the heat of the heater 11 is applied to the recording material via the fixing film 13, and the unfixed toner image t on the recording material P is hot-pressed and fixed.

When the recording material P passes through the fixing nip N, the recording material P is separated from the outer surface of the fixing film 13 by a curvature and discharged onto a discharge tray (not shown).

(3) Heater 11 FIG. 3A is an enlarged schematic cross-sectional view of the heater 11.
(B) is a plan model diagram of the back side, and (c) is a pattern model diagram of a heating element for a large-size recording material and a heating element for a small-size recording material.

The heater 11 in this embodiment is a backside heating type ceramic heater. That is, Al which has high thermal conductivity
_A heating element (Ag / Pd.Ta ₂ N) is provided on the back side (anti-heating side) of the ceramic substrate such as ₂ O ₃ or AlN opposite to the front side (heating side, the side facing the fixing film). , Etc.).

The heater 11 of this embodiment has a large-sized recording material heating element 11b1 and a small-sized recording material heating element 11b3 + 11b2 + 11b3 formed along the length on the back side of the ceramic substrate 11a. is there. 1
Reference numerals 1d1 and 11d1 denote power supply electrodes formed to be electrically connected to both ends of the heating element for large-size recording materials. 11
Reference numerals d2 and 11d2 denote power supply electrode portions that are formed so as to be electrically connected to both end portions of the small-sized recording material heating element. 11c
Is a thin glass protective layer formed so as to cover the large-sized and small-sized recording material heating element forming surfaces. 14
And 15 are a temperature detecting means (thermistor) and a thermoprotector, and the glass protective layer 1 on the back side of the heater.
It is arranged in contact with the surface 1c.

S is a recording material conveyance standard (paper passing standard),
In the case of the apparatus of this example, the apparatus is a “center reference” apparatus in which a reference is provided at the center in the longitudinal direction of the recording material conveyance area of the image forming apparatus main body.

The heating element for large-size recording material 11b1
4.Large-size recording materials such as LTR and LGL (Large-size paper)
For use, the length La is set to 222 mm (= effective heat generation area W), and the width wa is set to 3 mm.

Heating element 11b3 + 11b for small-size recording material
In 2 + 11b3, the heating element 11b2 at the center is D
For envelopes of L, com10, monarch, etc. (for small size paper)
And the length Lb
Is set to 116 mm, and the width wb is set to 1.57 mm.
The heating elements 11b3 and 11b3 on both sides thereof correspond to the small-size paper non-sheet passing sections C and C, respectively, as the heating elements outside the sheet passing section, and have a length Lc of 53 mm and a width wc of the sheet passing section B, respectively. 4.71 m which is three times the width wb of the heating element 11b2
m. With this configuration, the heating value ratio per unit length of the heating element 11b2 corresponding to the small-size paper passing portion B and the heating element 11b3 corresponding to the small-size non-paper passing portion C of the small-size recording material heating elements 11b3 + 11b2 + 11b3. Is 3: 1 (sheet passing portion B: non-sheet passing portion C).

Further, the heater 11 in this embodiment
Is a heating element 1 for a large-size recording material to reduce manufacturing costs.
1b1 and heating element for small-size recording material 11b3 + 11b2 +
11b3 is screen-printed at once with the same heating element material. Therefore, if the heating element 11b2 corresponding to the small-size sheet passing portion B of the small-size recording material heating element is to be formed to have the same width as the large-size recording material heating element 11b1, the total resistance value is reduced by the short longitudinal length. And the power consumption during energization increases, so that electrical noise (flicker, harmonic distortion, etc.) increases, and the rating of electrical components for energizing the heater must be increased more than necessary (small size Since the resistance value of the heating element 11b3 corresponding to the paper non-sheet passing portion C is lower than the resistance value of the heating element 11b2 corresponding to the small-size paper passing portion B, the influence on the total resistance value is small. In order to prevent these problems, the width wb of the heating element 11b2 corresponding to the small-size paper passing portion B of the heating element for small-size recording material is expressed as wb = (Lb /
La) × wa and the length of the heating element are made as narrow as about the ratio of the total resistance value of the two heating elements to the same value.

The temperature detecting means 14 and the thermoprotector 1
Reference numeral 5 is provided in the small-size paper passing portion B.

When passing large-size paper, the power supply electrode 11
When power is supplied between d1 and 11d1, the heating element 11b1 for large-size recording material generates heat, and the entire heater rapidly rises in temperature. The temperature rise of the heater 11 is detected by the temperature detecting means 14 and is fed back to a power supply control unit (not shown). The power supply control unit controls the power supply to the large-size recording material heating element 11b1 such that the heater temperature detected by the temperature detection unit 14 is maintained at a predetermined substantially constant temperature (fixing temperature).

When small-size paper is passed, the power supply electrode 11
When power is supplied between d2 and 11d2, the small-sized recording material heating elements 11b3 + 11b2 + 11b3 generate heat.
In this case, as described above, the heating value ratio per unit length of the heating element 11b2 corresponding to the small-size paper passing portion B and the heating element 11b3 corresponding to the small-size non-sheet passing portions C and C is 3:
1 (paper passing portion B: non-paper passing portion C). The heater temperature corresponding to the small-size paper passing section B is detected by the temperature detecting means 14 and is fed back to the power supply control section. The power supply controller controls the power supply to the small-sized recording material heating elements 11b3 + 11b2 + 11b3 so that the heater temperature detected by the temperature detecting means 14 is maintained at a predetermined substantially constant temperature (fixing temperature).

FIGS. 4 and 5 respectively show the small-size paper non-sheet passing portion C of the heater 11 when the envelope (com10) is passed as a small-size recording material at a throughput of 24 ppm.
4 shows the temperature distribution along the longitudinal direction of the heater when there is no heating element 11b3 outside the paper passage portion and when there is no heating element 11b3.

When there is no heating element 11b3 outside the paper passing unit,
As can be seen from FIG. 4, the temperature of the small-size paper passing portion B rises to a temperature at which fixing is possible and is temperature-controlled, whereas the temperature of the small-size paper non-passing portion C is low. Has become. Therefore, in such a state, A4, LTR
Even if the power supply is switched to the large-sized recording material heating element 11b1 in order to pass large-sized paper, such as the above, the end heater temperature does not rise immediately, and a fixing failure occurs at the end. Further, even when the next print is made to wait until the end temperature rises, the thermistor 14 for controlling the temperature is located in the warm center, so that it is difficult to supply power, and the time is longer than the normal heater start-up time. Is required.

Further, as with the temperature distribution of the heater 11, the temperature distribution of the pressure roller is also the same as that of FIG. Due to the diameter difference, a difference occurs in the feeding speed of the fixing film 13, and the fixing film may be twisted.

On the other hand, as in the present embodiment, when there are heating elements 11b3, 11b3 outside the paper passing portion corresponding to the small paper non-paper passing portions C, C of the heater 11, the heater 1
As shown in FIG. 5, the temperature distribution along the length of No. 1 is substantially uniform, and the large-size paper after passing the small-size paper can be uniformly fixed over the entire surface without waiting for printing. Further, twisting of the fixing film does not occur. Table 1 shows a case where there is no heating element 11b3 outside the sheet passing portion corresponding to the small size sheet non-sheet passing portion C of the heater 11 (FIG. 4) and a case where it is present (FIG. 5).
The presence or absence of occurrence of twisting of the fixing film during the passing of the envelope (comO), the edge fixing property when the LTR size paper is immediately passed, and the waiting time required until the entire surface can be fixed. Is shown.

[0087]

[Table 1] As can be seen from Table 1, when there is no heating element 11b3 outside the paper passing portion corresponding to the small paper non-paper passing portion C, the fixing film may be twisted.
When b3 is present, it is understood that film twist does not occur. Also, if you pass large-size paper after passing the envelope,
The temperature distribution in the longitudinal direction of the heater is reduced by heat transfer,
In order to be able to fix the entire surface, the heating element 11b outside the paper passing unit is required.
If there is no 3, it is necessary to wait for printing for about 40 to 60 seconds.

In this embodiment, the small-size paper passing portion B of the small-size recording material heating elements 11b3 + 11b2 + 11b3 is used.
The heat generation amount ratio R when the heat generation amount per unit length of the heat generation element 11b2 corresponding to the heat generation element 11b2 and the heat generation element 11b3 corresponding to the small size non-sheet passing portion C is Q1 and Q2, respectively, is R = Q1 / Q2.
= 3, but the upper limit of this value R is determined by the twisting of the fixing film and the fixability of the large-size paper after passing the small-size paper, and the lower limit is determined by the temperature rise at the edge when the small-size paper is passed. Therefore, on the condition that the fixing film is not twisted and that the fixing of the large-size paper can be performed with a waiting time of about 10 seconds after the passing of the small-size paper, the lower limit is set to 2 which is the throughput of the large-size paper.
Under the condition that the paper can be passed at / 3 or more, the appropriate value of R is 1.4 ≦ R ≦ 5, and almost the same effect as in the present embodiment could be obtained in this range. The heating value ratio R was controlled by making the widths wb and wc of the heating elements 11b2 and 11b3 different between the small-size paper passing portion B and the small-size paper non-passing portion C. The heating value can be controlled by changing the heating element material, and the same effect is obtained.

As described above, in the small-size paper non-sheet passing portion C,
By providing the heat-generating body 11b3 outside the paper-passing portion having a smaller amount of heat generation per unit length than the heat-generating body 11b2 of the small-size paper-passing portion B, a temperature distribution substantially uniform in the longitudinal direction of the heater even when small-size paper is passed. Can be obtained, and it is possible to prevent the fixing failure of the end portion of the normal size paper after the small size paper is passed and the twisting of the fixing film.

<Second Embodiment> (FIGS. 6 and 7) In the present embodiment, the heat generation corresponding to the small-size paper passing portion B of the small-size recording material heating elements 11b3 + 11b2 + 11b3 in the first embodiment is described. The length Lb of the body 11b2 (11
6 mm) and the length L of the large-sized recording material heating element 11b1.
a (222 mm) medium-size recording material such as B5
Heating element for large-size recording material 1
1b1 and heating element for small-size recording material 11b3 + 11b2 +
11b3 is controlled to be lit at a predetermined lighting ratio, and is fixed by heating.

In the present embodiment, as shown in FIG.
A thermistor 14a (end thermistor) for measuring the temperature rise of the heater end portion is provided at the heater portion corresponding to the non-sheet passing portion D of the E-size recording material, and a control system (not shown) increases the size according to the detected temperature. Lighting switching between the recording material heating element 11b1 and the small-size recording material heating element 11b3 + 11b2 + 11b3 is performed.

The other conditions are the same as those in the first embodiment, and the description will not be repeated.

Referring to FIG. 7, heating element 1 for large-size recording material
A lighting switching algorithm of 1b1 (a large-sized heating element) and small-sized recording material heating elements 11b3 + 11b2 + 11b3 (a small-sized heating element) will be described.

First, when a print command is received, paper conveyance is started with the large-size heating element 11b1 turned on (S10).
TEPI), by a paper width sensor on the paper transport path, etc.
Heating element for small size 11b3 + 11 for transported paper
It is detected that the paper width is wider than the heating element 11b2 corresponding to the small-size paper passing portion B of b2 + 11b3 (STEP
2).

Next, the temperature rise at the end of the heater 11 is measured by the end thermistor 14a to determine whether the temperature rises, that is, whether the transported paper is large-size paper (A4,
Detects whether the paper width is smaller than LTR) (STEP
3) When the end temperature rises, the heating element for small size 11
b3 + 11b2 + 11b3 (STE
P4).

After the switching, if the temperature of the end portion falls below 250 ° C. when the temperature of the paper passing portion falls below the feasible temperature, the power supply to the large-size heating element 11b1 is switched (STEP 5).

By the above algorithm, B5, EXE
And fixing of medium-size paper.

By the above algorithm, the large-sized heating element 11b1 and the small-sized heating element 11b3 + 11b2 +
By switching 11b3, the temperature distribution in the B5, EXE system paper passing area can be maintained at a fixing temperature as shown by the curves (a) and (b) in FIG.

Table 2 shows that, according to the above algorithm, the bonding paper which is disadvantageous for fixing among the B5 and EXE systems can be fixed with and without the heating element 11b3 outside the sheet passing section in the small sheet non-sheet passing section C. High throughput.

[0100]

[Table 2] As can be seen from Table 2, when the small-size paper non-paper passing portion C is provided with the heating element 11b3 outside the paper passing portion by the above algorithm, 1.5 times the throughput can be obtained as compared with the case where the heating element 11b3 is not provided. When the small-size paper non-sheet passing portion C does not have the heat-generating body 11b3 outside the paper-passing portion, the amount of heat generated outside the heating member 11b2 corresponding to the small-size paper passing portion B inside the B5 and EXE sizes is insufficient. As shown by the curve (c) in FIG. 6, the temperature of that portion decreased as the paper was passed, and the throughput could not be increased above 12 ppm.

In this embodiment, the fixing is performed according to the above-described algorithm. However, the same effect can be obtained by lighting the large-sized heating element 11b1 and the small-sized heating elements 11b3 + 11b2 + 11b3 at a fixed lighting ratio. was gotten.

In this embodiment, the heating element 11 for small size is used.
The heating value ratio per unit length of the heating element 11b2 corresponding to the small-size paper passing portion B of b3 + 11b2 + 11b3 and the heating element 11b3 corresponding to the small-size non-paper passing portion C was R = 3, but R ≦ 4. The same effect as in the present embodiment is obtained, and R> 4
In the case of (3), a fixing failure occurred at the end of the medium-size paper such as B5 or EXE. Therefore, in the range of 1.4 ≦ R ≦ 4, substantially the same effects as in the present embodiment can be obtained.

As described above, by increasing the calorific value at the end of the non-sheet-passing portion of the heating element for small-size paper from the inside of the paper area, twisting when small-size paper passes and subsequent large-size paper It is possible to prevent the fixing failure of the non-sheet passing portion when the sheet is passed, and at the same time, it is possible to increase the throughput of intermediate size sheets such as B5 and EXE sizes.

<Third Embodiment> (FIG. 8) In this embodiment, the heat generating members 11b3 + 11b2 + 11b for the small-size recording material as shown in FIG.
The small heat-generating units 11b3, 11b3 corresponding to the small-size paper non-sheet-passing units C, C3 of FIG. The heater temperature distribution during paper passing was made uniform to the end. As a result, good fixability can be obtained up to the end even on large-size paper after passing small-size paper.

Table 3 shows the result of comparison between the squeezing amount at the end and the end fixing property of the normal size paper (LTR) after passing the small size paper.

[0106]

[Table 3] As can be seen from Table 3, by setting the end reduction amount to about 10%, a low-temperature and low-humidity environment (L / L: 15 ° C., humidity 1)
0%), sufficient fixability can be obtained up to the end of the large-size paper after passing the small-size paper.

In the present embodiment, the method of reducing the width of the heating element is used as a method of increasing the amount of heat generated outside the paper passing area. However, the resistance value may be controlled by changing the thickness or the material of the heating element. A similar effect was obtained.

As described above, the heating element 1 for small-size recording material
1b3 + 11b2 + 11b3 small-size paper non-sheet passing portion C
By increasing the amount of heat generated at the ends of the heat-generating elements 11b3 outside the paper-passing portion corresponding to C, the fixability of the end of the large-size paper after the small-size paper is passed is ensured regardless of the use environment. And good fixability can be obtained over the entire area of the paper passing area.

<Others> 1) The heater 11 is not limited to the back (back) heating type of the embodiment, but may be a conventional type (surface heating type).

2) It is needless to say that the reference for passing the recording material P may be the one-side reference.

3) The image heating apparatus of the present invention is not limited to the fixing apparatus of each of the embodiments, but may be an apparatus for heating a recording material carrying an image to improve the surface properties such as gloss, or an apparatus for temporarily attaching. It can be widely used as a means and a device for heating a material to be heated, such as a heating device, a device for heating and drying a material to be heated, a heating laminating device, and the like.

4) Unfixed toner image t on recording material P
The formation principle and process are not limited and are optional.

[0113]

As described above, according to the present invention, large-size paper after passing small-size paper, which has conventionally been a problem in an image heating apparatus of a film heating type and an image forming apparatus equipped with the image heating apparatus. Insufficient heating of the edge and twisting of the film can be prevented. At the same time, the throughput can be increased. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to a first embodiment.

FIG. 2 is a schematic cross-sectional view of a fixing device.

FIG. 3 is a diagram illustrating the configuration of a heating element.

FIG. 4 is a temperature distribution diagram along the length of the heating element when the small-size paper is passed when there is no heating element outside the small-size paper passing portion.

FIG. 5 is a temperature distribution diagram along the length of the heating element when the small-size paper passes when there is a heating element outside the small-size paper passing portion.

FIG. 6 is a diagram illustrating a configuration of a heating body and a temperature distribution along a length of the heating body in a second embodiment.

FIG. 7 is a diagram showing a heating element switching algorithm.

FIG. 8 is a diagram illustrating a configuration of a heating element according to a third embodiment.

FIG. 9 is a schematic configuration diagram of a main part of an example of a film heating type image heating device (heating fixing device).

FIG. 10 (a) is a partially cutaway plan view of the surface side (heating surface side) of an example of a heating element (ceramic heater);
(B) is a model plan view of the back side (anti-heating side).

[Explanation of symbols]

11 heating element (heating heater), 11a ceramic substrate, 11b1 heating element for large-size recording material, 11b3
・ 11b2 ・ 11b3} Heating element for small size recording material, 1
1c thin protective glass layer, 12 stay holder,
13mm thin film (fixing film), 14.14a
{Temperature detection element (thermistor), 15} Thermo protector, 20} Pressure roller

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenji Kanari 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Toshio Miyamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Junji Naito 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) 2H033 AA03 BA27 BB18 BE03 CA17

Claims (5)

[Claims] 1. A heating element comprising: a heating member; and a film having one surface sliding with the heating member and the other surface moving in contact with a recording material bearing an image. In an image heating apparatus for heating an image on a recording material by heat, the heating element includes a heating element for a large-size recording material that heats a recording material having a maximum sheet passing width, and a recording material having a width smaller than the recording material having a maximum sheet passing width. The heating element for a small-size recording material has a heating value per unit length outside the paper-passing portion of the small-size recording material that is smaller than that of the paper-passing portion. An image heating apparatus comprising: a heating element outside a sheet passing portion having a heat generation distribution such that a temperature distribution in a longitudinal direction of the heating element when a small, small-sized recording material is passed is substantially uniform. 2. A heating mode for heating an image on a recording material by lighting the heating element for a large-sized recording material and the heating element for a small-sized recording material at a predetermined lighting ratio. The image heating device according to claim 1. 3. The image according to claim 1, wherein, in the heating element outside the sheet passing portion of the heating element for a small-sized recording material, the amount of heat generated per unit length is larger at an end portion. Heating equipment. 4. An image heating apparatus according to claim 1, further comprising a pressure member for forming a heating nip by pressing said heating member with a film interposed therebetween. 5. An image forming apparatus comprising: an image forming unit for forming an unfixed image on a recording material; and a heat fixing unit for fixing the unfixed image as a permanent image on the recording material. Item 5. An image forming apparatus, comprising: the image heating apparatus according to any one of Items 1 to 4.