JP2002372884A - Fixing device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device in which a driving gear made of synthetic resin is not broken even when a thinned roll is used as a fixing roll, and the thinned fixing roll is stably driven and rotated without causing cost rise or shortening the life of the fixing device, and an image forming device using the fixing device. SOLUTION: In the fixing device using a thin cylindrical fixing roller, a detent part in which the key part of a driving gear for driving and rotating the fixing roller is fit is provided at the end in the shaft direction of the thin cylindrical fixing roller. A contact area increase member for increasing contact area with the key part of the driving gear is provided at the edge part of the detent part of the fixing roller on the downstream side in the roller rotating direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic system,
A fixing device used in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which adopts an image forming method such as an electrostatic recording method, an ionography, and a magnetic recording method, and forms a color or black and white image. More particularly, the present invention relates to a fixing device capable of saving power and shortening a first printout time (a time from when the power is turned on until the first print can be performed), and an image forming apparatus using the fixing device. It is about.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer or a facsimile which employs an image forming method such as the electrophotographic method described above, it is needless to say that image quality such as full color and high image quality is required. Satisfies various requirements, such as miniaturization of equipment, long life, high productivity, power saving, and reduction of first printout time (time from power-on until printing of the first sheet becomes possible). Is being sought.

The present applicant has proposed various image forming apparatuses in order to meet the needs of such image forming apparatuses such as copying machines and printers.
As disclosed in Japanese Patent Application Laid-Open No. 0-78686, an image forming apparatus capable of reducing the size of an apparatus and forming a high-quality color image without using a complicated image misalignment prevention technique. The device has already been proposed.

The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. H10-78686 includes various embodiments. As one of the embodiments, two image bearing members and one intermediate transfer member are used. , And a unit structure composed of the other two photoreceptors and one intermediate transfer member, and one of the two intermediate transfer members further includes
A structure in which two intermediate transfer members are in contact with each other has been proposed. The four photoconductors shown here have a common tangent line, and therefore, a charging device, an exposure device, a developing device, and a cleaning device disposed around these four photoconductors are respectively provided with respective photoconductors. Are arranged at the same position, and devices are shared for each device type.

In this image forming apparatus, each toner image formed on the two photosensitive members is transferred to an intermediate transfer member, then transferred to a third intermediate transfer member, and is transferred onto the other two photosensitive members. Each of the formed toner images is transferred to the other intermediate transfer member, and then transferred to the third intermediate transfer member. The toner images transferred to the third intermediate transfer member are collectively transferred onto the recording paper that has been conveyed. Is transcribed. The toner image transferred onto the paper P is fixed on the recording paper by a fixing device. Since the intermediate transfer body is a drum type and is made of a rigid body, a misalignment between toner images hardly occurs.

By the way, a fixing device used in a so-called tandem type image forming apparatus of this type has a power saving and a first printout time (the time from when the power is turned on until the first sheet can be printed). It is required to satisfy requirements such as shortening.

[0007] As a fixing device meeting such a demand, a heating roll having a heating source therein, a fixing belt formed in an endless belt shape, a belt guide member rotatably supporting both ends of the fixing belt, and A pressure-contact member disposed inside the fixing belt to press the fixing belt against the surface of the heating roller, and a nip portion formed between the heating roller and the fixing belt carries an unfixed toner image. There is a configuration in which a fixing process is performed by heat and pressure by passing through a recording medium.

[0008] In this fixing device, a fixing belt in which a pressing member is not a roll-shaped member but an endless belt is formed.
Since the pressure roller is configured to be brought into pressure contact with the heating roll by the pressure contact member, the heat capacity of the pressure member can be reduced, the thickness of the heating roll can be reduced, and the heating roll can be heated to a predetermined fixing temperature. Power can be reduced and time can be reduced, and power can be saved and the first printout time (the time from when the power is turned on until the first print can be performed) can be reduced. .

In this fixing device, in order to drive the heating roll to rotate, the heating roll is attached to an end of a cylindrical core of the heating roll in a state in which a synthetic resin drive gear is fitted. The key portion of the synthetic resin drive gear is fitted in the key groove of the cylindrical cored bar to prevent the drive gear from rotating.

[0010]

However, the prior art described above has the following problems. That is, in the case of the fixing device used in the above-described conventional image forming apparatus, the thickness of the heating roll is reduced in order to achieve power saving and shorten the first printout time. Therefore, to rotate the heating roll,
A synthetic resin drive gear is fitted to the end of the cylindrical core of the heating roll, and a key portion of the synthetic resin drive gear is fitted to a key groove of the cylindrical core, When the rotation of the drive gear is stopped, the knife-edge-shaped edge portion of the key groove of the thinned cylindrical metal core directly contacts the key portion of the synthetic resin drive gear. Therefore, when the driving force is transmitted by another gear that meshes with the drive gear in order to rotate the heating roll, the knife edge of the key groove of the thinned cylindrical metal core is attached to the key portion of the synthetic resin drive gear. The key portion of the synthetic resin drive gear breaks, and the heating roll can be rotationally driven while the edge portion of the shape directly abuts and a shearing force acts to repeatedly rotate the heating roll. And the fixing device becomes unusable.

In order to solve such a problem, a metal gear may be used as a drive gear for rotating the heating roll. In this case, the metal gear is made of a synthetic resin. Since it is more expensive than a gear, there is a new problem that the cost is increased. Further, when a metal gear is used as a drive gear for rotating and driving the heating roll, a load is applied to the key groove of the thinned cylindrical core, and the key of the cylindrical core is changed. The groove may be deformed, making it difficult to stably rotate the heating roll, and in any case, there is a problem that the life of the fixing device is shortened.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a fixing roll made of a synthetic resin even if a thinned roll is used. And a fixing device capable of stably rotating a thinned fixing roll without causing breakage of the driving gear and without increasing the cost or shortening the life of the fixing device. An object of the present invention is to provide an image forming apparatus.

[0013]

According to a first aspect of the present invention, there is provided a fixing device using a thin-walled cylindrical fixing roller. An end portion is provided with a detent portion for fitting a key portion of a driving gear for rotationally driving the fixing roller, and an edge portion of the detent portion of the fixing roller on the downstream side in the roller rotation direction is provided with the detent portion. A fixing device is provided with a contact area increasing member for increasing a contact area of a drive gear with a key portion.

Further, the invention described in claim 2 is characterized in that the contact area increasing member is a member in which a rotation preventing portion of the fixing roller is bent inward.
3. The fixing device according to item 1.

Further, according to a third aspect of the present invention, in the fixing device according to the first aspect, the contact area increasing member comprises a separate member fitted to the rotation preventing portion of the fixing roller. Device.

According to a fourth aspect of the present invention, the contact area increasing member is disposed at a predetermined distance inward from an axial end of the fixing roller. 3. The fixing device according to any one of 3.

Further, according to a fifth aspect of the present invention, there is provided a method for transferring toner images having different colors formed on a plurality of image carriers onto a recording medium via one or more intermediate transfer members. In an image forming apparatus for forming an image by fixing with a fixing device using a thin cylindrical fixing roller, the fixing device rotates the fixing roller at an axial end of the thin cylindrical fixing roller. A detent portion for fitting a key portion of the drive gear for driving is provided, and an edge portion of the detent portion of the fixing roller on the downstream side in the roller rotation direction has a contact area with the key portion of the drive gear. An image forming apparatus is provided with a contact area increasing member for increasing the number of contacts.

The intermediate transfer member is, for example,
Although a plurality of intermediate transfer members are used, the image forming apparatus provided with only one intermediate transfer member may of course be used.

The plurality of image carriers include, for example, cyan (C), magenta (M), yellow (Y),
And black (K) toner images are used, but the order and type of these colors may of course be other.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a tandem-type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.

In FIG. 2, reference numeral 01 denotes a main body of a tandem type full-color printer.
The print head device (Print Head Device) 02 for performing full-color image formation is roughly divided into 01 inside.
An ROS (Raster Output Scanner) 03 as an exposure device for exposing four photosensitive drums 11, 12, 13, and 14 as image carriers of the print head device 02, and developing each color of the print head device 02. Equipment 41, 42,
Four toner boxes 04Y, 04M, 04C, and 04K for supplying toners of colors corresponding to 43 and 44, a paper feed cassette 05 for supplying recording paper P as a recording medium to the print head device 02, and the print head A fixing device 70 that performs a fixing process on the recording paper P on which the toner image has been transferred from the device 02 and a recording paper P on which an image is fixed on one side by the fixing device 70 are again turned upside down. A double-sided conveyance path 07 for conveying to the transfer section of the print head device 02, a manual paper feeding unit 08 for feeding desired recording paper P from outside the printer main body 01, and a controller 09 for controlling the operation of the printer; An electric circuit 10 including an image processing circuit for performing image processing on an image signal and a high-voltage power supply circuit is provided. In FIG. 2, T indicates a discharge toilet for discharging the recording paper P on which an image has been formed, and the discharge toilet T is integrally disposed on the upper portion of the printer main body 01.

Of the various members disposed inside the printer main body 01, ROS03 as an exposure device corresponds to each color of yellow (Y), magenta (M), cyan (C), and black (K). Four semiconductor lasers that are turned on and driven based on the obtained image data, an f-θ lens or a polygon mirror for deflecting and scanning four laser lights emitted from these four semiconductor lasers, or a plurality of reflections It is composed of a mirror and the like.

FIG. 3 shows a print head device of a tandem type full color printer as an image forming apparatus according to Embodiment 1 of the present invention. In addition, the arrow in FIG. 3 has shown the rotation direction of each rotating member.

As shown in FIG. 3, the print head device 02 includes photosensitive drums (image carriers) 11, 12 for yellow (Y), magenta (M), cyan (C), and black (K). Forming units 1, 2, 3, including
4 and a primary charging charging roller (contact type charging device) 21, 22, 23, 2 for contacting the photosensitive drums 11, 12, 13, 14.
4 and laser beams 31, 32, 33, 33 of yellow (Y), magenta (M), cyan (C), and black (K).
An ROS (exposure device) 03 (see FIG. 2) that irradiates the photosensitive drums 11, 12, 13, and 14 with yellow (Y), magenta (M), and cyan (C),
A developing device 41 for developing with toner of each color of black (K),
42, 43, 44 and the above four photosensitive drums 11, 12, 13, 14
The first primary intermediate transfer drum (intermediate transfer member) 51 that contacts two of the photosensitive drums 11 and 12 and the second primary intermediate transfer drum (intermediate) that contacts the other two photosensitive drums 13 and 14 Transfer member) 52, a secondary intermediate transfer drum (intermediate transfer member) 53 that contacts the first and second primary intermediate transfer drums 51 and 52, and a final transfer roll (contact member) that contacts the secondary intermediate transfer drum 53. The main part thereof is constituted by the transfer member) 60.

The photosensitive drums 11, 12, 13, and 14 are arranged at regular intervals so as to have a common tangent plane M. Further, the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52 have their respective rotating shafts of the photosensitive drums 11, 1.
They are arranged so as to be parallel to the axes 2, 13 and 14 and have a plane-symmetric relation with a predetermined plane of symmetry as a boundary. Further, the secondary intermediate transfer drum 53 includes the photosensitive drums 11, 12, 13, 14
And the rotation axis are parallel to each other.

Signals corresponding to the image information for each color are rasterized by an image processing circuit provided in the electric circuit 10 (see FIG. 2) and input to the ROS03. This ROS
In 03, laser beams 31, 32, 33, and 33 of each color of yellow (Y), magenta (M), cyan (C), and black (K)
34 is modulated, and the photoconductor drums 11, 12, 13,
Irradiated at 14.

Around the photosensitive drums 11, 12, 13, and 14, an image forming process for each color is performed by a known electrophotographic method. First, the photosensitive drums 11, 12, 1
For example, photosensitive drums using an OPC photosensitive member having a diameter of 20 mm are used as the photosensitive drums 3, 14, and these photosensitive drums 11, 12, 13, and 14 are driven to rotate at a rotation speed of, for example, 95 mm / sec. You. The photosensitive drums 11, 12, 13, 14
As shown in FIG. 3, the surface of is charged to about -300 V, for example, by applying a DC voltage of about -840 V to the charging rolls 21, 22, 23, and 24 as contact-type charging devices. The contact-type charging device includes a roll-type charging device, a film-type charging device, and a brush-type charging device, but any type may be used.
In this embodiment, a charging roll generally used in an electrophotographic apparatus in recent years is employed. Further, in this embodiment, in order to charge the surfaces of the photosensitive drums 11, 12, 13, and 14, a charging method of applying only DC is used, but a charging method of applying AC + DC may be used.

Thereafter, the surfaces of the photosensitive drums 11, 12, 13 and 14 correspond to the respective colors of yellow (Y), magenta (M), cyan (C) and black (K) by ROS03 as an exposure device. The laser beams 31, 32, 33, and 34 are applied to form an electrostatic latent image corresponding to the input image information for each color. When an electrostatic latent image is written by ROS03 on the photosensitive drums 11, 12, 13, and 14, the surface potential of the image exposed portion is
The charge is removed to about -60 V or less.

An electrostatic latent image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) formed on the surface of the photosensitive drums 11, 12, 13, and 14. Are developed by the developing devices 41, 42, 43, and 44 of the corresponding colors, and yellow (Y), magenta (M), cyan (C), and black (K) are formed on the photosensitive drums 11, 12, 13, and 14, respectively. Are visualized as toner images of the respective colors.

In this embodiment, the developing devices 41, 42, 4
The magnetic brush contact type two-component developing method is adopted for 3, 44, but the scope of the present invention is not limited to this developing method, and the present invention can be sufficiently applied to the non-contact type developing method. Of course.

The developing devices 41, 42, 43, and 44 contain toners of yellow (Y), magenta (M), cyan (C), and black (K) of different colors, respectively, and a developer composed of a carrier. Is filled. These developing devices 41, 42,
As shown in FIG. 2, when the toner is supplied from the toner boxes 04Y, 04M, 04C, and 04K of the corresponding colors, the supplied toner is sufficiently stirred with the carrier by the auger 404. Is charged by friction. Inside the developing roll 401, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is arranged in a fixed state. By a paddle 403 for transporting the developer to the developing roll 401,
The developer transported near the surface of the developing roll 401 is
The amount conveyed to the developing section is regulated by the developer amount regulating member 402. In this embodiment, the amount of the developer is
30 to 50 g / m ² , and at this time, the developing roll 401
The charge amount of the toner present on the surface is approximately -20 to 35 μC / g.
It is about.

The toner supplied onto the developing roll 401 is in the form of a magnetic brush composed of a carrier and toner due to the magnetic force of the magnet roll, and the magnetic brush is applied to the photosensitive drums 11, 12, 13, and 14. Is in contact with An AC + DC developing bias voltage is applied to the developing roll 401 to apply toner on the developing roll 401 to the photosensitive drums 11, 12, and 12.
By developing the electrostatic latent image formed on 13, 14
A toner image is formed. In this embodiment, for example,
When the AC component of the developing bias voltage is 4 kHz and 1.5 kVpp,
The DC component is set to about -230V.

In this embodiment, the developing devices 41, 4
2, 43 and 44, the toner is a so-called "spherical toner" which is a substantially spherical toner and has an average particle diameter of 3 to
For example, the average particle diameter of the black toner is set to 8 μm, and the average particle diameter of the color toner is set to 7 μm.

Next, the respective photosensitive drums 11, 12, 13, 14
The toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) formed on the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52
Is electrostatically secondary-transferred. The yellow (Y) and magenta (M) toner images formed on the photoconductor drums 11 and 12 are formed on the first primary intermediate transfer drum 51 by the cyan (C) formed on the photoconductor drums 13 and 14. The toner images of C) and black (K) are respectively transferred onto the second primary intermediate transfer drum 52. Accordingly, on the first primary intermediate transfer drum 51, the monochrome image transferred from either of the photosensitive drums 11 and 12 and the two-color toner image transferred from both of the photosensitive drums 11 and 12 are superimposed. A double-color image is formed. Also, on the second primary intermediate transfer drum 52, similar single color images and double color images are formed from the photosensitive drums 13 and 14.

The first and second primary intermediate transfer drums 5
The surface potential required for electrostatically transferring the toner images from the photosensitive drums 11, 12, 13, and 14 onto the surface 1, 52 is approximately +250 to 500 V. This surface potential is set to an optimum value depending on the charged state of the toner, the ambient temperature, and the humidity. The ambient temperature and the humidity can be easily known by detecting the resistance value of a member having a characteristic in which the resistance value changes depending on the ambient temperature and the humidity. As described above, when the charge amount of the toner is in the range of -20 to 35 .mu.C / g and the environment is normal temperature and normal humidity, the surface potential of the first and second primary intermediate transfer drums 51 and 52 becomes , + 380V is desirable.

The first and second primaries used in this embodiment
The intermediate transfer drums 51 and 52 have, for example, an outer diameter of 42 mm.
And the resistance is 10⁸It is set to about Ω. 1st, 2nd
The primary intermediate transfer drums 51 and 52 are single-layer or
Consists of flexible or elastic cylindrical
Rotating body, generally made of metal such as Fe or Al
Conductive silicone rubber on metal pipe as core
Low resistance elastic rubber layer (R = 10^Two~Ten^ThreeΩ)
Is provided with a thickness of about 0.1 to 10 mm. Furthermore,
The outermost surfaces of the first and second intermediate transfer drums 51 and 52 are typically
Is fluororubber with fluororesin microparticles dispersed in a thickness of 3 to
100 μm high release layer (R = 10^Five~Ten⁹Ω)
And connect with a silane coupling agent-based adhesive (primer).
Is being worn. What is important here is the resistance value and surface release.
And the resistance of the high release layer is R = 10 ^Five~Ten⁹About Ω
Yes, as long as the material has a high mold release property, the material is particularly limited
Not done.

The single-color or double-color toner images thus formed on the first and second primary intermediate transfer drums 51 and 52 are
The image is electrostatically tertiarily transferred onto the secondary intermediate transfer drum 53. Therefore, on the secondary intermediate transfer drum 53, a final toner image from a single color image to a quadruple color image of yellow (Y), magenta (M), cyan (C), and black (K) is formed. Will be.

The surface potential required for electrostatically transferring the toner images from the first and second primary intermediate transfer drums 51 and 52 onto the secondary intermediate transfer drum 53 is about +600 to 1200 V. . The surface potential is the same as when the toner is transferred from the photosensitive drums 11, 12, 13, and 14 to the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52. Will be set to the optimum value. Also, since what is necessary for the transfer is the potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53, the first and second primary intermediate transfer drums 51 and 5 are required.
It is necessary to set the value according to the surface potential of 2.
As described above, the charge amount of the toner is in the range of -20 to 35 .mu.C / g, and the surface potential of the first and second primary intermediate transfer drums 51 and 52 is +380 V under normal temperature and normal humidity environment. In this case, the surface potential of the secondary intermediate transfer drum 53 is about +880 V, that is, the potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53 is +880 V. It is desirable to set to about 500V.

The secondary intermediate transfer drum 53 used in this embodiment has, for example, an outer diameter of 42 mm, which is the same as the first and second primary intermediate transfer drums 51 and 52, and a resistance value of 10 ¹¹ Ω.
Set to about. Also, the secondary intermediate transfer drum 53 has a single-layer structure, similarly to the first and second primary intermediate transfer drums 51 and 52.
Alternatively, the rotating body is a cylindrical rotating body having a flexible or elastic surface having a plurality of layers, and is generally made of conductive silicone rubber or the like on a metal pipe as a metal core made of Fe, Al, or the like. A typical low-resistance elastic rubber layer (R =
10 ² to 10 ³ Ω) in a thickness of about 0.1 to 10 mm. Further, the outermost surface of the secondary intermediate transfer drum 53 is typically made of a fluoro rubber in which fluoro resin fine particles are dispersed, having a thickness of 3 to
It is formed as a high release layer having a thickness of 100 μm, and is bonded with a silane coupling agent-based adhesive (primer). here,
The resistance value of the secondary intermediate transfer drum 53 needs to be set higher than those of the first and second primary intermediate transfer drums 51 and 52.
Otherwise, the secondary intermediate transfer drum 53 charges the first and second primary intermediate transfer drums 51 and 52, and it is difficult to control the surface potential of the first and second primary intermediate transfer drums 51 and 52. Become. The material is not particularly limited as long as it satisfies such conditions.

Next, the final toner image from the single color image to the quadruple color image formed on the secondary intermediate transfer drum 53 is
The third transfer is performed by the final transfer roll 60 onto the sheet P passing through the sheet transport path. The paper P passes through a paper transport roll 90 through a paper feeding process (not shown), and is transferred to the secondary intermediate transfer drum 53.
Is transferred to the nip portion of the final transfer roll 60. After this final transfer step, the final toner image formed on the paper is fixed by the fixing device 70, and a series of image forming processes is completed.

The fixing device according to this embodiment includes a heating roller having a heating source therein, a fixing belt formed in an endless belt shape, and a state in which the fixing belt is fitted inside both ends of the fixing belt. A belt guide member disposed rotatably on an inner surface of the fixing belt; a pressure contact member disposed inside the fixing belt to press the fixing belt against the surface of the heating roll; An oil supply member for supplying oil to the inner surface, wherein the fixing is performed by passing a recording medium carrying an unfixed toner image through a nip formed between the heating roll and the fixing belt. ing.

FIG. 4 is a perspective view showing the appearance of the fixing device according to this embodiment, and FIG. 5 is a sectional view showing the fixing device according to this embodiment.

The fixing device 70 according to this embodiment is similar to the fixing device 70 shown in FIG.
As shown in FIG. 7, a heating roll 70 having a heating source 701 therein.
2, a fixing belt 703 having an endless belt shape, a belt guide member 704 supporting both ends of the fixing belt 703 so that the fixing belt 703 is rotatable,
The fixing roller 703 includes a pressing member 705 for pressing the fixing belt 703 against the surface of the heating roll 702, and a felt member 706 as an oil supply member for supplying oil to the inner surface of the fixing belt 703. It is configured. In FIG. 5, reference numeral 750 denotes an exit roll of the fixing device 70.

As will be described in detail later, the heating roll 702 has a thin cylindrical core made of iron, stainless steel or the like, and a thickness of about 0.65 mm made of silicon rubber coated on the surface of the core. And a release layer having a thickness of about 30 μm made of PFA or the like coated on the surface of the elastic layer. A 600 W halogen lamp 701 is provided inside the heating roll 702 as a heating source.

The fixing belt 703 is made of a synthetic resin such as polyimide and has an inner diameter of 30 mm and a thickness of 75 μm.
m, and is provided with a release layer made of PFA or the like on the surface as necessary.

Further, as shown in FIG. 6, the belt guide member 704 is constructed so as to be integrally assembled with the press contact member 705.

As shown in FIGS. 6 and 7, the pressing member 705 includes a belt housing 707 made of a synthetic resin, and a metal belt having a substantially U-shaped cross section which is attached to the belt housing 707 in a fitted state. Frame 708 and fixing belt 703
Nip head member for pressing the heater against the heating roll 702
709 and a pad member 710 mounted on the nip head member 709.

The belt guide member 704 is the same as that shown in FIG.
As shown in FIG. 7, the belt frame 708 is attached to both ends of the belt housing 707 in a state of being fitted to fitting portions 708a projecting in parallel from each other at both ends of the belt frame 708.

Further, the felt member 706 serving as the oil supply member is made of, for example, Nomex (trade name), and the felt member 706 is impregnated with about 2.0 g of oil made of amino Si oil having a viscosity of 300 cs. Have been. As shown in FIGS. 5 and 7, the felt member 706 is fixed to the back side of the belt frame 708 by a means such as bonding.

As shown in FIG. 8, the pressing member 705 is connected to an arm member 717 via a belt guide member 704.
The arm member 717 is configured such that the pressing member 705 is
, At a predetermined pressure (for example, 24 kgf). 7 and 8, reference numeral 719 denotes a synthetic resin film-shaped sheet member interposed between the fixing belt 703 and the pressure contact member 705.
Although the friction between the fixing belt 703 and the pressure contact member 705 is reduced, it is not always necessary to provide it.

The fixing device according to this embodiment is a fixing device using a thin cylindrical fixing roller. The fixing roller is driven to rotate at an axial end of the thin cylindrical fixing roller. A key portion of the drive gear for engaging the key portion of the drive gear, and a contact area between the key portion of the drive gear and the edge portion of the rotation stop portion of the fixing roller on the downstream side in the roller rotation direction. It is configured to provide a contact area increasing member for increasing.

The contact area increasing member is constituted, for example, by a member in which the rotation preventing portion of the fixing roller is bent inward. Further, the contact area increasing member is disposed, for example, inside a predetermined distance from an axial end of the fixing roller.

That is, a heating roll as the fixing roll
As described above, 702 is a thin cylindrical core made of iron, stainless steel or the like, an elastic layer made of silicon rubber or the like coated on the surface of the core and having a thickness of about 0.65 mm, Thickness 30 made of PFA or the like coated on the surface
and a release layer of about μm.

As shown in FIG. 9, the thin cylindrical core metal 720 is made of a metal such as iron or stainless steel to have a thickness of 0.5 mm.
It is formed in a thin cylindrical shape so as to have a thickness of mm. As shown in FIGS. 1 and 9, one end of the thin cylindrical metal core 720 in the axial direction is made of synthetic resin for rotating a heating roll 702 composed of the thin cylindrical metal core 720. A detent part 721 for fitting the key part 731 of the drive gear 730 is provided. As shown in FIG. 10, the detent portion 721 is formed by cutting a thin cylindrical cored bar 720 into an elongated flat U-shape from its end toward the inside in the axial direction.

As shown in FIG. 10, the detent portion 721 has a contact portion with the edge portion 722 on the downstream side in the rotation direction of the heating roller 702 to increase the contact area with the key portion 731 of the drive gear 730. An area increasing member 723 is provided, and the contact area increasing member 723 includes a thin cylindrical core bar 72.
0 and formed integrally. In other words, when the contact area increasing member 723 forms the substantially U-shaped detent portion 721 by pressing or the like, the detent portion 721 is formed.
The thin cylindrical cored bar 720 located at
It is formed by bending about m. Further, the contact area increasing member 721 includes a thin cylindrical core 721.
Is not provided from the end in the axial direction, but a predetermined distance (for example, 5 m) from the end of the thin cylindrical cored bar 720.
m) along the edge portion 722 of the detent portion 721 from the inside in the axial direction. By doing so, in order to perform the step of coating the surface of the thin cylindrical core metal 720 with an elastic layer or the like, when the thin cylindrical core metal 720 is held, the end of the thin cylindrical core metal 720 is tapered. The contact area increasing member 723 is prevented from contacting the tapered holding member 740 when the holding member 740 is inserted. If there is no problem in holding the thin cylindrical core bar 720, the contact area increasing member 723 may be provided from the end of the thin cylindrical core bar 720. The contact area increasing member 723 is formed, for example, by bending a general sheet metal.

As shown in FIG. 11, an elastic layer 725 made of silicon rubber or the like and having a thickness of about 0.65 mm and a PF are provided on the surface of the thin cylindrical cored bar 720 constructed as described above.
A heating roll 702 is formed by coating with a release layer 726 made of A or the like and having a thickness of about 30 μm.

Then, at the end of the heating roll 702,
As shown in FIG. 1, a drive gear 730 made of synthetic resin for rotating the heating roll 702 is provided.
Key part 731 to the detent part 721 of the thin cylindrical core bar 720.
(Key groove), and fitted and attached.

In the fixing device according to the present embodiment, even if a thinned roll is used as a fixing roll, the drive gear made of synthetic resin may be damaged in the following manner. In addition, it is possible to stably rotate the thinned fixing roll without increasing the cost and reducing the life of the fixing device.

That is, the fixing device according to this embodiment
In FIG. 5, as shown in FIG. 5, a heating roll 702 having a heating source 701 therein, a fixing belt 703 formed in an endless belt shape, and a fixing belt 703 are provided so that the fixing belt 703 can rotate. Belt guide member supporting both ends
704, a pressure contact member 705 disposed inside the fixing belt 703 to press the fixing belt 703 against the surface of the heating roll 702, and a felt member 706 for supplying oil to the inner surface of the fixing belt 703. Fixing is performed by passing a recording medium P carrying an unfixed toner image through a nip formed between the heating roll 702 and the fixing belt 703.

At this time, as shown in FIG. 5, the heating roller 702 is rotated in the direction of the arrow (clockwise in the figure) in a state of being pressed against the fixing belt 703 by the pressing member 705 so as to be pressed. Is also circulated and driven by the heating roll 702.

As shown in FIG. 1, a driving gear 730 for rotatingly driving the heating roll 702 is attached so as to be fitted to the outer periphery of the heating roll 702 at the axial end. The drive gear 730 is fitted on the outer periphery of the axial end of the heating roll 702, and at the same time, a key portion 731 protruding radially inward on the inner periphery of the drive gear 730 is connected to the heating roll 730. 702 is attached in a state where it is fitted to the detent part 721 (key groove).

At this time, the core metal 720 of the heating roll 702
Is formed in a thin cylindrical shape having a thickness of about 0.5 mm, the edge of the rotation preventing portion 721 (key groove) of the heating roll 702 becomes a knife edge as it is.

Therefore, in the above-described embodiment, as shown in FIGS. 1 and 10, the rotation preventing portion 72 of the thin cylindrical cored bar 720 is used.
1, a contact area increasing member 723 for increasing the contact area with the key portion 731 of the drive gear 730 is provided at the edge portion 722 on the downstream side in the rotation direction of the heating roller 702. By drive gear 730
The contact area with the key portion 731 is several times to several tens times the thickness of the thin cylindrical cored bar 720. Therefore, when the heating roller 702 is driven to rotate by the driving gear 731, a large shearing force does not act on the key portion 731 of the driving gear 730, so a thinned roll is used as the heating roll 702. Even in this case, the key portion 731 of the drive gear 730 made of synthetic resin is not damaged, and the contact area increasing member 723 is formed by bending a part of the thin cylindrical metal core 720 so that the cost is reduced. It is possible to stably rotate the thinned heating roll without causing an increase and without reducing the life of the fixing device.

Second Embodiment FIG. 12 shows a second embodiment of the present invention. The same portions as those in the first embodiment are denoted by the same reference numerals and described. The contact area increasing member is constituted by a separate member fitted to the rotation preventing portion of the fixing roller.

That is, in Embodiment 2, FIG.
As the contact area increasing member 740, a member obtained by bending a metal piece such as iron, which is a member different from the thin cylindrical cored bar 720 of the heating roll 702, into a substantially L-shaped cross section is used.
The contact area increasing member 740 is, for example, a thin cylindrical cored bar.
The rotation preventing portion 721 of the 720 is fixed to the edge portion 722 on the downstream side in the rotation direction of the heating roller 702 by means such as bonding. The contact area increasing member 740 is provided in a state where the mounting of the drive gear 730 is not hindered.

The contact area increasing member 740 is, as a result, a detent part 721 of the thin cylindrical cored bar 720,
Edge 722 on the downstream side in the rotation direction of heating roller 702
May be provided on the key portion 731 side of the drive gear 730 in some cases.

In the above-described embodiment, the contact area increasing member is provided at the rotation preventing portion of the thin cylindrical core metal at the downstream side in the rotation direction of the heating roller. You may comprise so that it may be provided also in the rotation direction upstream. In this case, it is effective when the heating roller is manually reversely rotated to remove a jam or the like.

[0069]

As described above, according to the present invention,
Even when a thinned roll is used as the fixing roll, the synthetic resin drive gear is not damaged, and the thickness is stably reduced without increasing the cost or shortening the life of the fixing device. A fixing device capable of rotating and driving a fixing roll and an image forming apparatus using the same can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram illustrating a main part of a fixing device according to a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram showing a tandem-type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a configuration diagram showing a print head device of a tandem-type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 4 is an external perspective view showing a fixing device.

FIG. 5 is a sectional configuration diagram showing a fixing device according to the first embodiment of the present invention.

FIG. 6 is an external perspective view showing a pressing member.

FIG. 7 is an exploded perspective view showing a pressing member.

FIG. 8 is a configuration diagram showing a fixing device according to the first embodiment of the present invention.

FIG. 9 is a configuration diagram showing a cylindrical cored bar.

FIG. 10 is a configuration diagram showing a main part of a cylindrical cored bar.

FIG. 11 is a configuration diagram showing a heating roll.

FIG. 12 is a cross-sectional configuration diagram illustrating a main part of a fixing device according to a second embodiment of the present invention.

[Explanation of symbols]

70: fixing device, 701: heating source, 702: heating roll, 720
: Thin cylindrical core bar, 721: Detent, 722: Edge, 723: Contact area increasing member, 730: Drive gear, 731
: Key part.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/16 103 G03G 15/16 103 (72) Inventor Yasutaka Goto 3-7-1 Funai, Iwatsuki-shi, Saitama No. Within Fuji Xerox Co., Ltd. (72) Inventor Takeshi Fukuda 3-7-1, Fuuchi, Iwatsuki-shi, Saitama F-term within Fuji Xerox Co., Ltd. (Reference) 2H030 AA05 AB02 AD04 BB42 2H033 AA21 AA23 BB13 BB37 2H200 FA09 GA12 GB22 GB25 JC02 3J103 AA02 AA24 AA81 BA03 BA46 FA12 GA02 GA57 GA58 GA60 GA66

Claims (5)

[Claims] In a fixing device using a thin cylindrical fixing roller, a key portion of a driving gear for rotating and driving the fixing roller is fitted to an axial end of the thin cylindrical fixing roller. And a contact area increasing member for increasing a contact area with a key portion of the drive gear is provided at an edge portion of the rotation preventing portion of the fixing roller on the downstream side in the roller rotation direction. Fixing device. 2. The fixing device according to claim 1, wherein the contact area increasing member is formed by bending a detent portion of the fixing roller inward. 3. The fixing device according to claim 1, wherein the contact area increasing member is a separate member fitted to a rotation preventing portion of the fixing roller. 4. The fixing device according to claim 1, wherein the contact area increasing member is disposed at a predetermined distance inside an axial end of the fixing roller. 5. After transferring toner images of different colors formed on a plurality of image carriers onto a recording medium via one or more intermediate transfer members, a thin cylindrical fixing roller is used. In an image forming apparatus that forms an image by fixing with a fixing device, the fixing device includes a key portion of a driving gear for rotating and driving the fixing roller at an axial end of the thin cylindrical fixing roller. A detent portion for fitting is provided, and a contact area increasing member for increasing a contact area with the key portion of the drive gear is provided at an edge portion of the detent portion of the fixing roller on the downstream side in the roller rotation direction. An image forming apparatus comprising: