JP2001183930A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heating device by which a body to be heated such as a recording material is smoothly fed by eliminating the sagging of film and also an image forming device which is provided with the heating device as an image heating means or a fixing means and by which an image having an excellent quality is formed. SOLUTION: In the heating device having the film 2, a heating body 3 to heat the body to be heated through the film 2 and a pressing body 4 to press the body to be heated and guided to a nip part N to the heating body 3 through the film 2 by forming the nip part N with the heating body, the aperture part of the nip part N on an upstream side in the feeding direction of the body to be heated is made to be narrower at least at one part of a longitudinal nip part than at the longitudinal center of the nip part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for heating an object to be heated and an image forming apparatus such as a copying machine or a printer using the heating device as a fixing device.

[0002]

2. Description of the Related Art Conventionally, a heating roller system has been generally used as a heating device as a fixing device for fixing a visible image formed on a heated object to the heated object. However, a large heat capacity is required, and it takes time to start up the apparatus from power-on to image output.

Therefore, recently, in order to realize power saving and shorten the time from power-on to image output, for example, JP-A-63-313182 and JP-A-2-157.
No. 878, a film heating and fixing method, that is, a heating body for heating a body to be heated via a thin film, and a pressurizing body for pressing the body to be heated to the heating body via the film It has been proposed to apply a heating device having the following as a fixing device.

FIG. 16 is a schematic configuration diagram showing a conventional heating device based on a film heating and fixing system in which the maximum sheet passing width is A3 size. 101 is a stay, and this stay 101
Is composed of a main body portion 105 having a U-shaped cross section that exposes and supports the heating body 103 and a pressing portion 106 that presses the main body portion toward the opposing pressing roller 104. Reference numeral 102 denotes a heat-resistant film (hereinafter, abbreviated as a film) having a circular cross-section and externally fitted to the stay 1.

[0005] FIG. 15 is a plan view of the heating element 103 in which a part of the heating element 103 is omitted and partially cut away. The heating element 103 is an elongated heat-resistant, insulating, and heat-conductive substrate 131 whose longitudinal direction is perpendicular to the conveying direction a of the film 102 or a recording material P such as paper as an object to be heated. 13
1, a resistance heating element 132 formed along the longitudinal direction of the substrate at the center in the short direction on the surface side, and a heat-resistant overcoat layer 13 protecting the heating element surface on which the resistance heating element is formed.
4. Power supply electrodes 133 at both longitudinal ends of the resistance heating element 132
Along with 133, a linear heating element having a low heat capacity and including a temperature detecting element 107 such as a thermistor provided on the back side of the substrate for detecting the temperature of the heating element is used as the substrate structure. In FIG. 16, the heating element 103 is provided with a resistance heating element 132 fixedly exposed downward to the lower surface of the stay 101 having rigidity and heat resistance.

The substrate 131 of the heater 103 is made of, for example, alumina or aluminum nitride having a thickness of 1 mm and a width of 10 mm.
mm and a length of 330 mm. The resistance heating element 132 is made of, for example, Ag / Pd (silver palladium), RuO
₂ , formed by applying an electric resistance material such as Ta ₂ N into a linear or narrow strip having a thickness of about 10 μm and a width of 1 to 3 mm by screen printing or the like.

The power supply electrodes 133 and 133 are made of, for example, a screen printing pattern layer of Ag or the like, and an overcoat layer 134.
Is, for example, a heat-resistant glass layer having a thickness of about 10 μm.

The pressure roller 104 forms a pressure contact nip portion (fixing nip portion) N with the film 102 interposed between the pressure roller 104 and the heat roller 103 and acts as a film outer surface contact driving means for driving the film 102 to rotate. . The film driving roller and pressure roller 104 is composed of a cored bar 104a, an elastic layer 104b made of silicon rubber or the like, and an outermost release layer 104c. The heating element 103 is disposed so as to be pressed against the surface of the heating element 103 with the element 102 interposed therebetween. The pressure roller 104 is rotated by a motor M to apply a conveying force to the film by a frictional force between the pressure roller 104 and the outer surface of the film 102.

A so-called tensionless type heating element 103 of this kind is disclosed in, for example, JP-A-4-44075 to JP-A-4-44083, JP-A-4-204980 to JP-A-4-204984, and the like. It has been disclosed.

Next, the operation will be described.

The temperature of the heating element 103 rises by supplying heat to the power supply electrodes 133 at both ends of the resistance heating element 132 so that the resistance heating element generates heat over the entire length thereof. It is detected by. The output of the temperature measuring element 107 is A / D converted and fetched into the CPU 108, and based on the information, the AC voltage of the AC power supply 110, which is energized to the resistance heating element 132 by the triac 109, is controlled by the phase, wave number, etc. Is controlled, the temperature of the heating body 103 is controlled.

That is, the power supply is controlled so that the temperature of the heating element 103 rises when the temperature detected by the temperature detection element 107 is lower than a predetermined set temperature, and the temperature of the heating element 103 decreases when the temperature is high. 103 is adjusted to a constant temperature during fixing. Thus, the temperature of the heating element 103 rises to a predetermined value, and the film 102 is rotated by the rotation of the pressure roller 104.
When the rotational peripheral speed of the recording medium P is stabilized, the recording material P on which the image is to be fixed is nipped and conveyed by the pressing nip N formed by the heating body 103 and the pressure roller 104, so that the heat of the heating body 103 is reduced. The unfixed visible image (toner image) T on the recording material P is applied to the recording material P via the film 102 and is fixed on the recording material P by heating. Then, the pressure nip N
The recording material P that has passed is separated from the surface of the film 102 and conveyed.

Since the film 102 is loosely fitted around the stay 101 with a sufficient peripheral length, there is a gap between the film 2 and the stay 1 as shown in FIG. Before entering the nip portion N, the film 2 is positioned at the end shown in FIG.
Are rotating with the same gap S0.

[0014]

However, in the conventional film heat fixing method, a recording material P (hereinafter, referred to as small size paper) having a narrow width relative to the axial length L of the film 102, for example, 2L / 3. When a recording material having a small width is continuously passed through a substantially central portion in the film axial direction, heat is not taken by the recording material in the non-paper passing portion. As a result, the temperature of the pressure roller 104 facing the non-sheet passing portion where heat is not taken away by the recording material becomes higher than the temperature of the paper passing portion where heat is taken away by the recording material. The diameter of the non-sheet passing portion is larger than that of the sheet passing portion.

Then, the peripheral speed of the pressure roller 104 is higher in the non-sheet passing portion. That is, the film 1 at the nip N
02 is higher in the non-sheet-passing portion than in the sheet-passing portion, causing a speed difference, and the film 102 is twisted between the sheet-passing portion and the non-sheet-passing portion.
And a gap weight of the end portion between the stay 1 as small as the clearance S ₁ as shown in FIG. 18 (a), the larger the clearance S ₂ as shown in FIG. 18 (b) at the central portion, S2>S0> Since the relationship S1 is established, the film 102 becomes slack like 102 'just before the nip portion N as shown in FIG.

When the recording material P enters the nip portion N in such a state, the leading end of the recording material P
The recording material P has a problem that the timing of entering the nip portion N in the longitudinal direction of the recording material varies due to the penetration resistance, and the recording material P is wrinkled.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object of the present invention is to provide a heating device capable of eliminating slack of a film and smoothly transporting an object to be heated such as a recording material. I do. It is another object of the present invention to provide an image forming apparatus which includes the heating device as an image heating unit or a fixing unit and forms a high quality image.

[0018]

Means for Solving the Problems [1]: A nip portion is formed between a film, a heating element for heating an object to be heated via the film, and the heating element. And a pressurizing unit that presses the heated body to the heated body via the film, wherein the opening of the nip portion on the upstream side in the transported direction of the heated body is formed in at least a part of the longitudinal direction of the nip portion. A heating device characterized in that it is narrower than the longitudinal center of the nip.

[2] The heating device according to [1], wherein the area having the narrowest opening is an area other than the longitudinal end of the nip.

[3]: The opening gradually narrows from the longitudinal end of the nip toward the center, becomes narrowest between the end and the center, and widens from that region toward the center. The heating device according to [1], wherein:

[4]: A film supporting means for guiding the movement of the film is provided, and a projecting portion for promoting the narrowing of the opening is formed on a part of the guide surface on the upstream side of the nip portion of the film supporting means. [1], [2]
Or the heating device according to [3].

[5] The heating device according to [4], wherein the protruding portion is formed as a smoothly changing continuous plane.

[6] The heating device according to [4] or [5], wherein the protruding portion is formed in a region between a longitudinal end of the nip portion and a central portion.

[7]: A film supporting means for guiding the movement of the film is provided, and a projecting portion for promoting the narrowing of the opening is formed on a surface opposite to a nip portion of the film supporting means. The heating device according to [1], [2] or [3], which is characterized in that:

[8]: The projecting portion is arranged at least at a central portion in the longitudinal direction of the nip portion [7].
A heating device according to claim 1.

[0026]

[9]: A film supporting means for guiding the movement of the film is provided, and a protruding portion for promoting the narrowing of the opening is formed on a part of the guide surface on the downstream side of the nip portion of the film supporting means. [1],
The heating device according to [2] or [3].

[10]: An image forming means, and an image heating means for heating the object to be heated sent from the image forming means to heat the image formed on the object to be heated, The image heating means is from [1]

[9] An image forming apparatus, which is the heating apparatus according to any one of [9].

[11]: An image forming means, and a fixing means for heating the object to be heated sent from the image forming means to fix an image formed on the object to be heated, the fixing means Is from the above [1]

[9] An image forming apparatus, which is the heating apparatus according to any one of [9].

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention will be described below.

FIGS. 1A and 1B are schematic views showing a heating device according to a first embodiment, wherein FIG. 1A is a perspective view and FIG. 1B is a side view of a part thereof. The present heating device is a heating device having a maximum sheet passing size of A3 size.

In the drawing, reference numeral 1 denotes a stay as a film supporting means. The stay 1 has a film guide 5 having a U-shaped cross section which exposes and supports the heating element 3, and is assembled to the film guide 5, and And a pressing portion 6 having a U-shaped cross section for pressing the pressing member 5 against the pressing roller 4 as a pressing member. Reference numeral 2 denotes a heat-resistant film (thin film) having a circular cross-section and externally fitted to the stay 1. The film 2 has an inner peripheral length larger than the outer peripheral length of the stay including the heating element 3 by, for example, about 3 mm. Therefore, the stay 1 is loosely fitted to the stay 1 with sufficient margin. The stay 1 is pressed in the entire longitudinal direction by a pressing roller 4 via a film 2 to form a nip portion N.

The film 2 has a thickness of 100 μm in order to reduce the heat capacity and improve the quick start property.
Hereinafter, preferably, a heat-resistant single-layer film of PTFE, PFA, FEP or the like having a heat resistance of 70 μm or less and 20 μm or more, or polyimide, polyamideimide, PEEK, PE
PTFE, PFA,
A coated multi-layer film such as FEP is used. In this embodiment, PTF is applied to the outer peripheral surface of the polyimide film.
A composite layer film coated with E is used.

In the apparatus according to the present embodiment including such components, when image formation is started by the image forming means described later, the driving of the pressure roller 4 is started to rotate the film 2 and the heating element. 3 is started, the rotation speed of the film 2 is stabilized, and the heating member 3 is adjusted to a predetermined fixing temperature. The toner image is fixed to the recording material (heat treatment) by the pressure from the nip N and the heat from the fixing roller 1. Then, the recording material is conveyed by the rotation of the pressure roller 4, and after passing through the nip portion N, the recording material separated from the film 2 is discharged out of the apparatus.

Next, the configuration of the present invention in which the opening of the nip portion is partially narrowed will be described.

As shown in FIG. 1A, the film guide 5 which is a component of the stay 1 supports the heating element 3 and
A substantially A portion of a portion between the longitudinal end and the central portion of the surface on the upstream side in the film rotation direction (hereinafter simply referred to as the upstream side) of the nip portion of the film guide 5 for guiding the film 2.
At the end position (T region in the figure) at the time of 4 vertical size paper feeding, a protruding portion 5a protruding outward from the film as compared with other portions is formed, and the thin film 2 and the pressure roller 4 upstream of the heating device are formed. The opening formed in step (A) is formed so that an area narrower than the longitudinal center of the nip portion is formed at the A4 vertical size position.

Here, in order to realize the degree of opening of the upstream opening, an area indicating the degree of opening of the opening as shown in FIG. 19 is defined. In a plane perpendicular to the rotation axis of the film 2, a tangent line v protruding outmost on the upstream side of the rotating film 2, an extension line h from the heating body surface, and an outer peripheral surface of the film 2 are surrounded. Let S be the area. For example, in FIG. 19, a dotted film line shows a state protruding outward as compared with a solid film line, and an area S (grid portion) surrounded by the dotted line is shown.
Is smaller than the area S surrounded by the solid line by the shaded portion.

When the film 2 is set on the stay 1 having the above structure, the running shape of the film 2 is urged outward by a protruding portion 5a between the longitudinal end portion and the central portion as shown in FIG. A region T having an area S indicating an opening which is smaller than an area indicating an opening formed by the film 2 and the pressure roller 4 in the portion can be formed at the position of the A4 vertical size end. Therefore, the film at the center is indented in the direction of the film rotation center from the film at the edge of the A4 vertical size.

On the other hand, when A4 vertical size paper (hereinafter, referred to as small size paper) smaller than the maximum paper width (A3 size) is continuously passed as the recording material P, the paper corresponding to the longitudinal end portion which is a non-paper passing portion is obtained. Both ends of the pressure roller 4 are heated, and the outer diameter of the pressure roller increases. Since the rotation drive of the film 2 in the heating device of the present embodiment is performed by the pressure roller 4,
Due to the outer diameter expansion of the end of the pressure roller, the transport speed of the film 2 at both ends becomes faster than the transport speed at the center. For this reason, the film 2 at the center in the longitudinal direction swells outward in the rotation direction. However, as shown in FIG.
Does not protrude in the upstream direction of the heating device as shown in FIG. For this reason, when the nip enters the nip, there is no variation in the entry timing due to contact with the film 2 at the center, and the paper tip smoothly enters the nip N from the end, causing paper wrinkles. There is no.

In the present embodiment, the paper wrinkle of A4 vertical size has been described, but B4, LGL, B5 vertical, B5
Also in the horizontal, A5 vertical, and A5 horizontal, the configuration of the present embodiment was able to prevent the occurrence of paper wrinkles. At this time, the area serving as the non-sheet passing section differs depending on various paper sizes. In any case, if the bulging of the central portion of the film can be suppressed, the required effect can be obtained, and the area formed in the A4 vertical size end area can be obtained. In this case, a sufficient effect for preventing paper wrinkles for each size was obtained.

In this embodiment, the protruding portion is formed at the end area of the A4 vertical size, but the protruding portion is formed at the end position of other size paper (for example, B4, B5 vertical, A5 vertical, etc.). The same effect was obtained for B4, B5 vertical, B5 horizontal, A5 vertical, and A5 horizontal.

FIG. 3 is a schematic view of a heating device in which a protruding portion 5b which protrudes outward compared to other portions is formed in a substantially A3 size end region (S region) of a longitudinal end portion of an upstream side surface of a stay body. is there. When the film 2 is set on the stay 1 having the above configuration, the running shape of the film is such that the end area of the A3 size is urged outward as shown in FIG. Can be formed at the position of the A3 size end portion having an area indicating a narrower opening than the area indicating the area.

In the heating device shown in FIG. 3 and the heating device using the stay shown in FIG. 2 described above, the recording material is extended in the longitudinal end direction by the shape of the pressure roller and the shape of the film guide. Large size paper wrinkles such as A3 and LDR size are prevented.

The heating device shown in FIG. 3 can also prevent small-size paper wrinkles similarly to the heating device of the present embodiment shown in FIG. 2 described above. When a wide recording material is passed, as shown in FIG. 5, the recording material end swells in the film direction at the upstream portion of the heating device nip due to the effect of stretching in the longitudinal end direction, which is a measure against the large-sized wrinkles described above. Therefore,
The unfixed image on the recording material may come into contact with the film in the upstream portion of the heating device, causing image disturbance.

On the other hand, in the heating device of the present embodiment shown in FIG. 2, wrinkles of small size paper can be prevented, and the protruding portion at the nip upstream portion is located inside the position of the large size end such as A3 size. 2 (b)
As shown in the figure, the film 2 does not protrude outward in the region where the edge of the recording material has risen. Therefore, since the opening formed by the film 2 and the pressure roller 4 is wide and there is no contact between the film and the unfixed image on the recording material, the image is not disturbed and a better image can be obtained.

(Second Embodiment) FIGS. 6A and 6B are schematic views showing a heating device according to a second embodiment, wherein FIG. 6A is a plan view and FIG. 6B is a side view of a part thereof. In this embodiment,
A stay 8 as a film supporting means is formed at both ends and a center of the stay 1 with projections 8 on the opposite surface to the surface on which the nip N is formed.

FIG. 7 is an exploded view of the components of the stay 1 excluding the film 2, wherein 5 is a film guide as a film supporting means, and 6 is a projection 8 formed on the upper surface of both ends and the center. The pressurizing portion 9 is an end member attached to the end of the pressurizing portion 6, and 10 is a pressing force applying member attached to the pressurizing portion 6 outside the end body and pressurizing the pressurizing portion.

When the film 2 is set on the stay having the above-described structure, the running shape of the film 2 is, as shown in FIG. 2 and pressure roller 4 in the upstream part of the
The area indicating the degree of opening of the opening in the M region is smaller than the area indicating the degree of opening of the opening formed by the above. FIG. 8B shows the film running shape at the center and the end, and FIG.
This is a film running shape in the region, and tension is applied to the film 2 at the longitudinal end portion and the center portion of the film by the protruding portions 8, so that the shape of the film is elongated in the J direction shown in FIG. Therefore, the length in the K direction of the longitudinal end and the central portion is shorter than the region between the longitudinal end and the central portion (region M in the drawing). For this reason, as shown in FIG. 8A, the film shape in the upstream portion of the nip is such that the central portion is depressed from the region M toward the film rotation center.

For this reason, as the recording material P, the maximum paper passing width (A
Even when paper of a size smaller than (3 size) is continuously passed, the film at the center is arranged in a recessed state in advance compared to the end region of the small size. No swelling occurs. For this reason, when the paper leading edge enters the nip, there is no variation in the entering timing due to contact with the film in the center portion, and the paper leading edge smoothly enters the nip portion N from the end portion, which may cause paper wrinkles. Absent.

Further, as in the heating device of the first embodiment, the opening formed by the film 2 and the pressure roller 4 at the longitudinal end is widened, so that the image is not disturbed by the contact with the film 2.

(Third Embodiment) FIGS. 9A and 9B are schematic views showing a heating device according to a third embodiment, wherein FIG. 9A is a perspective view and FIG. 9B is a side view of a part thereof. In this heating device, the contact surface with the film 2 on the upstream side of the film guide 5 as the film supporting means has a step like the stay 1 of the first embodiment, but passes through the projecting portion 5c from the end. The film guide surface forms a continuous wall surface that gradually changes from the center to the center. The height of the protrusion 5c in the T region is the same as the height of the protrusion 5a of the first embodiment.

According to the above configuration, compared to the case where the projecting portion has a step, the film guide 5 is less likely to receive a local force, and thus the durability of the film 2 is improved.

(Fourth Embodiment) FIG. 10 shows a fourth embodiment.
3A is a schematic view showing a heating device in FIG. 3A, FIG. 3A is a plan view, and FIG.

In this heating device, a projecting portion 5a is formed between the end of the upstream side surface of the film guide 5 as the film supporting means and the central portion, and a projecting portion 8 is formed on the upper surface of the central portion of the pressing portion 6. Configuration.

According to the above configuration, the central portion of the film 2 can be further dented in the direction of the center of rotation of the film as compared with the first embodiment. It is possible to further prevent the occurrence of paper wrinkles. Further, since the opening formed between the film 2 and the pressure roller 4 at both ends is widened, the image is not disturbed by the contact with the film 2.

(Fifth Embodiment) FIGS. 12A and 12B are schematic views showing a heating device according to a fifth embodiment, wherein FIG. 12A is a perspective view seen from the downstream of the nip, and FIGS. It is a side view of a part.

In this heating device, the configuration of the nip upstream portion of the film guide 5 is the same as that of the first embodiment shown in FIG.
In the same manner as described above, a protrusion protruding outward compared to the other portions is provided at an end position (T region) of a portion between the longitudinal end portion and the central portion of the upstream side surface of the film guide 5 when substantially A4 vertical size paper is passed. The shape 5a is formed. As shown in FIG. 12A, the configuration of the nip downstream portion is a configuration in which a protruding portion 5d is formed at the center.

According to the above configuration, the central portion of the film 2 can be further dented in the direction of the center of rotation of the film as compared with the first embodiment. This can be further prevented, and the generation of paper wrinkles can be improved. Further, since the opening formed between the film 2 and the pressure roller 4 at both ends is widened, the image is not disturbed by the contact with the film 2.

(Sixth Embodiment) FIGS. 13A and 13B are schematic views showing a heating device according to a sixth embodiment, wherein FIG. 13A is a perspective view as viewed from the downstream of the nip, and FIGS. FIG.

In this heating device, the shape of the film guide 5 is the same as that of the fifth embodiment.
Of the portion between the longitudinal end and the center of the upstream side of
At the end position (T region) at the time of 4 vertical size sheet feeding, a protruding portion 5a protruding outward in the film rotation radius as compared with other portions.
And a protruding portion 5d is formed at the center of the nip downstream portion. Also, a projecting portion 8 is formed on the surface opposite to the surface forming the nip portion at the center of the stay 1 as the film supporting means.
Is formed. Further, a protruding portion 11 is formed on the downstream side of the end body 9 that guides the end of the film.

According to the above configuration, the film at the center is moved to the first position.
As compared with the embodiment, the state can be further reduced in the direction of the center of rotation of the film, and the slack of the film 2 at the central portion when the small-size paper is passed can be further prevented, and the paper wrinkles can be further prevented.

Further, the film is tensioned by the protruding portions 11 formed on the end body 9, and the film 2 does not protrude outward in the region where the end of the recording material has risen. The opening made in is wide,
Since there is no contact between the film 2 and the unfixed image on the recording material, no image disturbance occurs, and a better image can be obtained.

In this embodiment, the protruding portion 11 is formed at the downstream portion of the end member, but the same effect can be obtained by forming the protruding portion at the end portion of the film guide downstream portion.

(Seventh Embodiment) FIG. 14 is a schematic diagram showing the configuration of an image forming apparatus of the present invention to which the above-described heating device is applied. In the figure, reference numeral 31 denotes a photosensitive drum serving as an image carrier having a diameter of, for example, 30 mm, which is driven to rotate at a predetermined speed in a direction indicated by an arrow R1 by a drive source (not shown).

Around the photosensitive drum 31, in order along the direction of rotation thereof, the surface of the photosensitive drum is charged, for example, with a diameter of 12 mm as a charging member for uniformly contacting the surface of the photosensitive drum to a predetermined potential.
A charging roller 33, a power supply unit 34 for applying a voltage on the charging roller 33, an exposure unit 35 for forming an electrostatic latent image on the photosensitive drum 31 in accordance with image information, Developing means 36 (in the first embodiment, a reversal developing system using negative toner is used) for adhering toner to make the toner image visible, and transfer paper P as a recording material using the toner image on photosensitive drum 31 as a recording material. A transfer roller 37 having a diameter of, for example, 12 mm as a transfer member, a charge eliminator 39 for removing the charge of the transfer paper P after the transfer of the toner image, and a residue attached to the surface of the photosensitive drum 31 after the transfer of the toner image. An image forming unit such as a cleaner 40 for removing and collecting the toner is provided. Reference numeral 41 denotes a fixing device to which the heating device described in any of the first to sixth embodiments is applied.

The charging roller 33 and the power supply device 34 constitute a contact charging device. The charging roller 33 has a central core 33a and a conductive rubber 33b formed on the outer surface thereof.
It is composed of Both ends of the core bar 33a are rotatably supported by a bearing member (not shown) and arranged in parallel with the photosensitive drum 31, and have a constant pressing force against the photosensitive drum 31 by a pressing member (not shown). Pressed
The photosensitive drum 31 rotates following the rotation of the photosensitive drum 31.

Next, the operation of the image forming apparatus configured as described above when forming an image will be described. Photosensitive drum 31
Is driven to rotate at a predetermined speed in the direction of arrow R1. For example, an oscillating voltage in which a DC voltage (constant voltage −625 V) is superimposed on an AC voltage (peak-to-peak voltage Vpp = 2.0 KV, sine wave having a frequency of 400 Hz) is applied to the charging roller 33 from the power supply device 34, The surface of the drum 31 is -600V
Is charged to a uniform potential.

The charged photosensitive drum 31 is exposed to the exposure means 35.
Exposure of the target image information (slit exposure of the original image,
An electrostatic latent image is formed by receiving laser beam scanning exposure or the like (in the illustrated example, slit exposure of a document image) La. Next, this electrostatic latent image is visualized with toner by the developing means 36 to become a toner image.

The transfer means 37 transfers the toner image visualized on the photosensitive drum 31 to the transfer paper P, and then the charge eliminator 39 removes the charge from the transferred transfer paper P, and then to the fixing means 41 of the present invention. The sheet is conveyed to fix the toner image on the transfer sheet P.

On the other hand, the toner remaining on the surface of the photosensitive drum 31 after the transfer is cleaned and removed by the cleaner 40, and the photosensitive drum 31 is again prepared for the next image formation.

[0070]

As described above, according to the present invention, it is possible to obtain a heating device capable of eliminating the slack of a film and smoothly transporting an object to be heated such as a recording material. Further, it is possible to obtain an image forming apparatus which includes this heating device as an image heating unit or a fixing unit and performs high quality image formation.

[Brief description of the drawings]

FIG. 1 is a schematic view of a heating device according to a first embodiment of the present invention, from which a film is removed.

FIG. 2 is a diagram illustrating a film shape of a heating device according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram of the heating device according to the first embodiment of the present invention, from which a film is removed.

FIG. 4 is a diagram illustrating a film shape of a heating device according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a film shape and a recording material conveyance shape of the heating device according to the first embodiment of the present invention.

FIG. 6 is a schematic diagram of a heating device according to a second embodiment of the present invention.

FIG. 7 is an exploded view of a main part of a heating device according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating a film shape of a heating device according to a second embodiment of the present invention.

FIG. 9 is a schematic view of a heating device according to a third embodiment of the present invention, in which a film is removed.

FIG. 10 is a schematic view of a heating device according to a fourth embodiment of the present invention, in which a film is removed.

FIG. 11 is a perspective view showing a slack of a film in an upstream portion of a nip when a small-size sheet is passed.

FIG. 12 is a schematic view of a heating device according to Embodiment 5 of the present invention, from which a film is removed.

FIG. 13 is a schematic view of a heating device according to Embodiment 6 of the present invention, from which a film is removed.

FIG. 14 is a side view of an image forming apparatus according to Embodiment 7 of the present invention.

FIG. 15 is a plan view of a heating element applied to a conventional heating device.

FIG. 16 is a sectional view showing a conventional heating device.

FIG. 17 is a schematic diagram showing a gap between a film and a stay.

FIG. 18 is a schematic diagram showing a gap between a film and a stay when a small-size sheet is passed.

FIG. 19 is a schematic diagram showing an area showing an opening of a heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stay (film support means) 2 Film 3 Heating body 4 Pressure roller (Pressing body) 5 Film guide 5a, 5b, 5c, 5d Projection 6 Pressure section 7 Form 8 Projection 8 Projection 9 End Body N Nip P Recording material

Continued on the front page (72) Inventor Satoru Taniguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Koichi Okuda 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masafumi Omata 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H033 AA14 BA11 BB33 BE03 3K058 AA00 BA18 CE13 DA04 GA06

Claims (11)

[Claims] 1. A nip portion is formed between a film, a heating element for heating an object to be heated via the film, and the heating element, and the object to be heated introduced into the nip is attached to the film. And a pressurizing body that pressurizes the heating body through the opening of the nip portion on the upstream side in the transport direction of the heated body in at least a part of the nip portion longitudinal center compared to the nip longitudinal center. A heating device characterized by being narrowed. 2. The heating apparatus according to claim 1, wherein the area having the narrowest opening is an area other than the longitudinal end of the nip. 3. The method according to claim 1, wherein the opening gradually narrows from the longitudinal end of the nip portion toward the center, is narrowest between the end and the center, and widens from the region toward the center. The heating device according to claim 1, wherein: 4. A film supporting means for guiding the movement of the film, wherein a protruding portion for promoting the narrowing of the opening is formed on a part of the nip portion upstream guide surface of the film supporting means. The heating device according to claim 1, wherein the heating device is a heating device. 5. The heating device according to claim 4, wherein the projecting portion is formed by a continually changing continuous plane. 6. The projection according to claim 4, wherein the projection is formed in a region between a longitudinal end of the nip and a central portion.
Or the heating device according to 5. 7. A film supporting means for guiding the movement of the film, wherein a projection for promoting the narrowing of the opening is formed on a surface of the film supporting means opposite to a nip portion. The heating device according to claim 1, 2, or 3. 8. The heating device according to claim 7, wherein the protruding portion is disposed at least at a central portion in a longitudinal direction of the nip portion. 9. A film supporting means for guiding the movement of the film, wherein a protruding portion for promoting the narrowing of the opening is formed on a portion of the guide surface on the downstream side of the nip portion of the film supporting means. Claim 1, 2, or 3
A heating device as described. 10. An image forming apparatus comprising: an image forming unit; and an image heating unit configured to heat an object to be heated sent from the image forming unit and heat-process an image formed on the object to be heated. An image forming apparatus, wherein the means is the heating device according to any one of claims 1 to 9. 11. An image forming apparatus comprising: an image forming unit; and a fixing unit configured to heat an object to be heated sent from the image forming unit to fix an image formed on the object to be heated. An image forming apparatus, comprising: the heating apparatus according to claim 1.