JP2002260826A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press roller which correctly performs heating treatment, despite that the thermal expansion of the pressure roller becomes high as the temperature becomes high, and the number of revolution increases, and the recording paper holding and transferring speed changes. SOLUTION: The heating device comprises a pressing member arranged so as to press a heating member, a fixing film laid between the heating member and the pressing member so as to wrap the heating member insides, and a roller-shaped pressing roller driving means arranged so as to press the pressing member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating apparatus having a heat-resistant film for transmitting heat from a heater to a recording material, and to an image forming apparatus such as a copying machine or a laser beam printer using the heating apparatus as a fixing means. Things.

[0002]

2. Description of the Related Art For example, in image forming apparatuses such as copying machines, laser beam printers (LBP), facsimile machines, micro film reader printers, image display (display) devices, and recorders, electrophotography, electrostatic recording, and magnetic recording. Recording material (transfer material sheet, electrofax sheet, electrostatic recording sheet, etc.) using a developer (toner) composed of a heat-meltable resin or the like by an appropriate image forming process means such as
A heating device (an image forming apparatus) that heats and fixes an unfixed toner image corresponding to target image information formed and carried on a surface of a printing paper or the like by an indirect (transfer) method or a direct method as a permanently fixed image on the recording material surface As a heating device, an image heating and fixing device), a recording material is formed by a heating roller as a heating body maintained at a predetermined temperature, and a pressure roller as a pressure member having an elastic layer and pressed against the heating roller. A heat roller method of performing a heat treatment while nipping and transporting is widely used. Also,
In addition, flash heating method, oven heating method,
Various systems and configurations such as a hot plate heating system are known and are in practical use.

Recently, instead of such a method, a fixedly supported heating element, a heat-resistant film (fixing film) conveyed while being pressed against the heating element, and a recording medium via the film. A pressurizing member for bringing the material into close contact with the heating body, and applying the heat of the heating body to the recording material via the film, whereby the unfixed image formed and supported on the recording material surface is recorded. There has been proposed a heating device (film heating system) having a system and a structure for heating and fixing on a material surface.

[0004] This heating device is not limited to the fixing described above.
It can be widely used as a device for improving the surface properties (such as gloss) by heating a recording material carrying an image, a device for performing a temporary deposition process, and a device for heating a recording material. In addition, since this heating device uses a heating element with a low heat capacity and a thin film that heats up quickly, it is possible to save power and shorten the wait time (quick start property), and reduce the temperature rise in the device. It has the advantage that it can be effective, and is effective.

[0005]

As described above, the recording material is introduced into the press-contact nip portion between the heating member and the pressing member, and the recording material is covered by the two members, as in the above-described heating apparatus of the heat roller type or the film heating method. 2. Description of the Related Art In an apparatus that heats a recording material by nipping and conveying a recording material, the speed of nipping and conveying the recording material in the apparatus varies depending on the temperature state of the constituent members. For example, in a film heating type heating device, a pressing member (hereinafter, referred to as a pressing roller) that presses against a heating body via a film is driven to rotate, thereby causing the film to slide on the heating body. In the case of a pressure-member-driven type in which a film or a film and a material to be heated are sandwiched and conveyed together with a press-contact nip portion between a heating element and a pressure roller, the temperature of the pressure roller increases with the operation of the apparatus. The outer diameter of the pressure roller becomes large due to the thermal expansion of the rubber portion.

Since the pressure roller is normally driven to rotate at a constant rotational speed, when the pressure roller is at a high temperature, the thermal expansion is greater than at a low temperature, the rotational peripheral speed is increased, and the recording material is nipped and conveyed. Speed will be faster. That is, the recording material nipping and conveying speed by the heating device differs depending on the temperature state of the pressure roller. Therefore, for example, when this heating device is used in an image forming apparatus as an image heating and fixing device,
Since the conveyance of the recording material in the image forming unit, for example, the image transfer unit, which is the processing unit on the upstream side of the heating device, is maintained at a predetermined constant, the recording material is pressed from the transfer unit by the pressure of the recording material of the heating device. When the sheet reaches the nip (fixing section) and enters the nipping and conveying state, when the pressure roller is at a high temperature, the recording material nipping and conveying speed in the fixing section of the heating device is higher than the recording medium conveying speed in the transfer section. Occurs, and the heating device pulls the recording material, which causes image blur at the transfer portion.

In view of the recording material pulling phenomenon, if the recording material sandwiching and conveying speed by the heating device is set to be lower than the initial speed of the recording material at the transfer section, the temperature of the pressure roller will still be low. At a low point in time, an unnecessary loop (slack) is formed on the recording material in the recording material transport unit between the transfer unit and the fixing unit of the heating device, and the separation direction of the recording material after image transfer in the transfer unit, Since the angle of incidence of the recording material on the fixing unit of the heating device becomes unstable, image scattering at the time of transfer / separation and offset at the fixing unit of the heating device occur. If the recording material used is thick, the stiffness of the recording material causes a blur at the transfer portion.

In order to eliminate the adverse effects caused by the pulling phenomenon of the recording material and the unnecessary loop formation phenomenon due to the fluctuation of the recording material nipping and conveying speed of the heating device, the distance between the transfer portion and the fixing portion of the heating device is reduced. In this case, it is necessary to increase the distance of the recording material transport section to shorten the time during which the recording material is simultaneously present in the transfer section, the transfer section, and the fixing section of the heating device.

However, in the case of an image forming apparatus such as an A3 machine that uses a long recording material to pass paper, the conveyance distance of the recording material between the transfer section and the fixing section becomes too long, and the image forming apparatus main body becomes considerably large. The reality was that it would become larger.

Japanese Patent Application Laid-Open No. Hei 7-261584 proposes a method of detecting the amount of loops of a recording material or detecting the transport speed of the recording material to change the driving speed of a pressure roller. ing. However, in these methods, the control cannot be performed until the first recording material reaches the fixing unit of the heating device, and when the recording material is transported at a high speed, the control may not be performed in time.

A method has also been proposed in which the temperature of the pressure roller is measured, and the amount of expansion is predicted to change the drive speed. However, a more precise control cannot be performed due to a large error.

Therefore, there has been proposed a method in which a light reflecting portion or a light transmitting portion is provided in a part of a heat resistant film, and the speed of the film is directly detected by a reflection type sensor or a transmission type sensor. However, in this method, the sensor must be arranged near the heating body, and there is a problem that the function of the sensor may be impaired due to the temperature rise near the heating body.

All of these methods require a means for detecting a change in the recording material nipping / conveying speed and a drive control means for changing the rotation speed of the pressure roller. In addition, there is a problem that the reliability of the apparatus is reduced due to complicated control.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a heating device and an image forming apparatus that have a stable and easy configuration and maintain a constant recording material conveyance speed. I do.

[0015]

Means for Solving the Problems (1) A heat-generating member, a pressurizing member disposed to face the heat-generating member, and a heat-generating member and the pressurizing member interposed so as to include the heat-generating member. And a roller sandwiched between the film and a pressure roller driving means disposed in opposition to the pressure member.

(2) In the pressure member, the surface friction coefficient of a portion to which the drive is transmitted by the pressure roller driving means is larger than the surface friction coefficient of a portion to which the drive is not transmitted. The image forming apparatus as described in the above.

(3) The image forming apparatus according to claim 1, wherein the pressure roller driving means is a heat radiating roller.

(4) The image forming apparatus according to claim 1, wherein the drive transmission to the pressure roller driving means is of an oscillating type which is far from the axis of the pressure roller driving means. .

(5) Image forming means for forming a document image or a toner image corresponding to an input image signal on an image carrier, and transferring the toner image on the image carrier onto a recording material, and the recording material 5. An image forming apparatus comprising: a fixing unit configured to fix the toner image transferred thereon to the recording material, wherein the heating device according to claim 1 is applied as the fixing unit. 6. An image forming apparatus comprising:

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment [General Structure of Image Forming Apparatus Main Body] First, referring to FIG. 1, the general structure of an image forming apparatus main body in which a heating device of the present invention is applied as a fixing device will be described. I do. Referring to FIG. 1, an image forming apparatus main body A (hereinafter, referred to as an apparatus main body A) has a scanner section B as image reading means for reading image information of a book document at an upper portion thereof, and an image forming apparatus as an image forming means at a lower portion thereof. A portion C is further assembled with a seat deck D below.

The scanner unit B includes a scanning system light source 201,
The apparatus includes a platen glass 202, a document pressure plate 203 that can be opened and closed with respect to the apparatus main body A, a mirror 204, a lens 205, a light receiving element (photoelectric conversion element) 206, an image processing unit, and the like. And the platen glass 20
2. Place a book document or sheet document such as a book, cardboard, curled paper, etc. on the document 2 with the document surface facing down, press the back with the document pressure plate 203, set it in a stationary state, and press the read start key. , The scanning optical source 201 is the platen glass 20
2 is scanned in the direction of arrow a in FIG. 1 to read image information on the document surface. Image information of the document read by the scanning light source 201 is processed by an image processing unit, converted into an electric signal, and transmitted to the laser scanner 111.

Here, the apparatus body A functions as a copying machine when the processing signal of the image processing unit is input to the laser scanner 111, and functions as a printer when the output signal of the computer is input. Further, if a signal from another facsimile apparatus is received or a signal from the image processing unit is transmitted to another facsimile apparatus, the apparatus functions as a facsimile apparatus.

On the other hand, a sheet cassette 1 is mounted below the image forming section C, and the sheet cassette 1 is composed of a lower cassette 1a and an upper cassette 1b as one feeding unit. In the illustrated example, two feeding units U1 and U2 are mounted, and four cassettes are mounted. One upper feeding unit U1 is detachably attached to the apparatus main body A, and the lower feeding unit U2 is detachably attached to the sheet deck D.

The sheets accommodated in the cassettes 1a and 1b are fed out by a pickup roller 3 serving as a feeding rotating body as will be described later, and are separated one by one by the cooperation of a feed roller 4 and a retard roller 5. After being fed, the sheet is conveyed by conveying rollers 104 and 105, guided to a registration roller 106, and
6, the sheet is fed to the image forming section C in synchronization with the image forming operation.

In addition to the sheet cassette 1, a manual feed tray 10 is disposed on the side of the apparatus main body A.
The sheet P on the tray 10 is fed by a manual feed roller 11 to a registration roller 106 via a transport roller 105.

The image forming section C includes an electrophotographic photosensitive drum 1
12, an image writing optical system 113, a developing device 114, a transfer charging device 115, and the like. Then, the photosensitive drum 112 uniformly charged by the charger 121
A laser beam corresponding to the image information emitted from the laser scanner 111 is scanned by the image writing optical system 113 to form a latent image, and a toner image is formed on the latent image by the developing device 114. This toner image is transferred to the first surface of the sheet conveyed in synchronization with the rotation of the photosensitive drum 112 by the registration roller 106 in the transfer charger 115.

The sheet P on which the toner image has been formed is conveyed by the conveying unit 117 to the fixing device 11 to which the heating device of the present invention is applied.
After being conveyed to the sheet 8 and heated and pressed to fix the toner image on the sheet surface, the sheet is discharged and stacked on a sorter 120 disposed outside the apparatus by a discharge roller 119.

To record an image on both sides of the sheet P, the sheet P discharged from the fixing device 118 is sandwiched by discharge rollers 119, and the rear end of the sheet P is
7, the discharge roller 119 is rotated in the reverse direction, and the sheet P is once placed on the sheet double-sided tray 121. , And the image is formed on the second surface in the same manner as described above, and then discharged and stacked on the sorter 120.

[Description of Fixing Apparatus] FIG. 2 is a cross-sectional view of the apparatus main assembly A from the image transfer section to the fixing section. The fixing unit of the present embodiment is a heating device of the present invention of a tensionless type film heating system which moves following the rotation of the pressing member.

In FIG. 2, reference numeral 112 denotes a photosensitive drum, 1
Reference numeral 15 denotes a transfer charger, and 117 denotes a transport unit. Reference numeral 11 denotes a horizontally long stay made of a heat-resistant resin, which serves as an inner surface guide member of an endless heat-resistant film (fixing film) 12 described below.

The film 12 has a heater 1 as a heating element.
3 is externally fitted to the stay 11. The inner peripheral length of the film 12 and the outer peripheral length of the stay 11 that joins the heater 13 are larger than that of the film 12 by, for example, about 3 mm.
The circumference is loosely fitted to 1 with a margin.

The film 12 has a total thickness of 40 to 40 in order to improve the quick start property by reducing the heat capacity.
PTFE, PFA on the outer surface of polyimide film with heat resistance, release property, strength, durability, etc.
And a coating layer obtained by adding a conductive agent to a fluororesin such as

Reference numeral 18 denotes a pressure roller which forms a fixing portion N which is a pressure contact nip portion between the heater 13 and the film 12, and frictionally drives the film 12 with rotation. And a heat-resistant rubber elastic body 19b having good releasability, such as silicon rubber, provided on the core shaft 19a, and having a thickness of 3 mm and an outer diameter of 20 mm.
It is. The recording material P,
A coating layer in which a fluororesin is dispersed is provided for the purpose of transporting the film 12 and preventing toner contamination.

Reference numeral 50 denotes a pressure roller driving member, which is made of a metal or resin having a small change in outer diameter due to temperature (a change of less than 1% at a temperature difference of about 200 ° C.). The driving force of the pressure roller driving member 50 is transmitted from a driving motor M of the apparatus main body A via a gear or a belt.
It is rotationally driven clockwise as indicated by the arrow (e) at a constant rotational speed.

As shown in FIG. 3, the transmission of the driving force follows the change of the outer diameter due to the temperature rise of the pressure roller 18 and has no effect even if the distance between the shaft centers changes. , And is driven in the f direction in the figure.

By the rotation of the pressure roller driving member 50, the pressure roller 18 is driven to rotate in the counterclockwise direction shown by the arrow (d), and the rotation causes the inner surface of the film 12 to slide closely on the surface of the heater 13. While being rotated clockwise (C) as indicated by the arrow.

At this time, the peripheral speed of the pressure roller driving member 50 does not greatly change due to a change in ambient temperature or a rise in the temperature of the pressure roller driving member itself due to heat of the pressure roller 18. Even at the time of expansion due to heat of 18, the peripheral speed can be kept constant, and the sheet conveying speed can be kept constant.

(Second Embodiment) In the first embodiment, the contact surface of the pressure roller surface with the roller driving member 50 is the same surface that is uniform in the longitudinal direction of the pressure roller 18. The surface is a sheet (recording material) as described above.
P, a coating layer in which a fluororesin is dispersed is provided for the reason of transportability of the film 12 and prevention of toner contamination. Therefore, the friction coefficient of the surface is relatively small, the surface does not slip, and a large contact surface is required for friction driving, which may lead to an increase in the size of the device.

In the second embodiment, the contact surface 41 of the pressure roller driving member of the pressure roller 18 is set outside the conveyance region of the sheet P, and the friction coefficient of the surface of the contact surface is changed to the friction of the paper passing region. It is different from the coefficient.

In FIG. 4, the surface of the roller driving member 50 is subjected to knurling or the like to increase the surface roughness. Further, the fluororesin coating layer is not provided on the contact surface 41 of the roller driving member 50 of the pressure roller 18. Thus, the friction coefficient of the surface of the pressure roller with the roller driving member 50 is larger than the friction coefficient of the sheet passing area. Further, as other means for increasing the friction coefficient of the surface of the contact surface 41, a method of coating a heat-resistant silicon rubber-based thin film or reducing the surface of the film itself by post-processing is used. There is also. This makes it possible to obtain more stable rotational drive.

(Third Embodiment) FIG. 5 shows a third embodiment, in which a roller 45 made of aluminum is provided below the pressure roller 12 by a biasing means (not shown), for example, with a total pressure of 500 g. Or 2 kg weight contact pressure.

When the roller 45 is not mounted, and when the transfer material having a width smaller than the length of the heater 13 is continuously processed, the heater 13 and the fixing film in a portion opposed to the heater are provided in a place where the transfer material does not pass. 12 and pressure roller 1
The temperature of No. 8 becomes remarkably high, and a phenomenon called so-called edge temperature rise that causes thermal damage to components occurs.

When the roller 45 is mounted, the roller 45 rotates clockwise as the pressure roller 18 rotates. As a result, since the heat conduction of the roller 45 is good, the temperature distribution in the axial direction of the pressing roller 18 in pressure contact with the roller 45 is made uniform. Then, the temperature distribution in the longitudinal direction of not only the pressure roller 18 but also the heater 13 and the fixing film 12 can be made uniform, and the above-mentioned phenomenon of end portion temperature rise does not occur. That is, the roller 45 plays a role of a temperature rise prevention member at the end of the pressure roller 18.

In the third embodiment, the pressure roller 18 is driven to rotate by rotating the roller 45. As a result, it is possible to prevent the temperature of the end portion of the pressure roller 18 from rising and to transmit the rotational driving force of the pressure roller 18, thereby reducing the size and cost of the apparatus.

[0045]

As described above, according to the present invention,
A pressure member disposed to face the heating member; a fixing film sandwiched between the heat generation member and the pressure member so as to include the heating member; and a fixing film disposed to face the pressure member. Is configured to have a roller-shaped pressure roller driving means, so that a special speed detection means and a speed control means are not required for an outer diameter change due to the temperature of the pressure roller, and stable paper conveyance can be obtained. At the same time, it is possible to transmit the drive from the apparatus body drive source, and it is possible to reduce the size and cost of the apparatus.

According to the present invention, in the pressing member, the surface friction coefficient of the portion to which the driving force is transmitted by the pressure roller driving means is made larger than the surface friction coefficient of the portion to which the driving force is not transmitted. Therefore, the sheet passing portion can be made of a surface material that emphasizes the fixing property, and the drive transmission portion can have a surface shape that emphasizes the transmission of the driving force, so that more stable sheet conveyance can be achieved.

According to the present invention, the pressure roller driving means is constituted by a heat radiating roller to prevent the end of the fixing device from rising in temperature and to transmit the rotational driving force of the pressure roller. And cost reduction.

According to the present invention, since the driving force transmitting portion is configured to be oscillating so as to be far from the axis of the pressure roller driving means,
There is an effect that it is possible to prevent a change in driving force transmission and an increase in load due to a change in the outer diameter of the pressure roller.

According to the present invention, in an image forming apparatus,
Since the heating device of the present invention is applied as a fixing unit, it is possible to obtain an image forming apparatus capable of forming a high-quality image with a stable and easy configuration, maintaining a constant recording material conveying speed. There is a clear effect.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus main body to which a heating device of the present invention is applied as a fixing device.

FIG. 2 is a cross-sectional view of an apparatus main body from an image transfer unit to a fixing unit.

FIG. 3 is a perspective view illustrating a configuration of driving force transmission to a pressure roller according to the first embodiment.

FIG. 4 is a perspective view illustrating a configuration of driving force transmission to a pressure roller according to a second embodiment.

FIG. 5 is a perspective view showing a configuration of transmitting a driving force to a pressure roller according to a third embodiment.

[Explanation of symbols]

 112 Photoconductor drum (image forming means) 113 Optical system (image forming means) 114 Developing device (image forming means) 115 Transfer charger (image forming means) 118 Fixing means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/20 107 G03G 15/20 107 F-term (Reference) 2H033 AA09 AA14 BA08 BB28 BB37 BE03 CA40 3J051 AA01 BA10 BD01 BE03 EA10 EC07 FA10 3J103 BA03 BA43 FA01 FA18 GA57 GA58 GA60 3K058 AA43 AA86 AA95 BA18 DA21

Claims (5)

[Claims] 1. A heating member, a pressing member disposed to face the heating member, and sandwiched between the heating member and the pressing member so as to include the heating member. A heating device, comprising: a film; and a roller-shaped pressure roller driving unit disposed to face the pressure member. 2. The pressure member according to claim 1, wherein a surface friction coefficient of a portion to which drive is transmitted by the pressure roller driving means is larger than a surface friction coefficient of a portion to which drive is not transmitted. Image forming apparatus. 3. An image forming apparatus according to claim 1, wherein said pressure roller driving means is a heat radiating roller. 4. An image forming apparatus according to claim 1, wherein the drive transmission to said pressure roller driving means is of a swinging type which is distant from and away from the axis of said pressure roller driving means. 5. An image forming means for forming a document image or a toner image corresponding to an input image signal on an image carrier, and transferring the toner image on the image carrier onto a recording material, And a fixing unit for fixing the toner image transferred to the recording material to the recording material, wherein the fixing unit is any one of claims 1 to 4.
An image forming apparatus to which the heating device according to claim is applied.