JP2001215830A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device where the wall of a fixing roll member is made thinner without having the fixing roll member damaged from metal fatigue, energy is saved, time for warming up is shortened, a wide nip part is formed and separating function of transfer material at the nip part is improved. SOLUTION: In the fixing device, the fixing roll member is made of a thin walled cylindrical elastic body, both ends of the fixing roll member are hold by retaining members provide with a greater inner diameter than the outside diameter of the fixing roll member. The deformation of the fixing roll member for a constant weight is greater than the deformation of a press roll member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used for an image forming apparatus such as a copying machine, a printer, a facsimile, etc., and more particularly to a fixing device capable of saving energy and shortening a warm-up time.

[0002]

2. Description of the Related Art Conventionally, as a fixing device used in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., a fixing roller member (fixing roller) having a heating means inside as a stable device having high technical perfection has been proposed. The heat roller fixing method used is widely used from low-speed machines to high-speed machines and from monochrome machines to full-color machines.

However, in a conventional heat roller fixing type fixing device, it is necessary to heat a fixing roller member (fixing roller) having a large heat capacity when heating a transfer material or toner. In addition, there is a problem that it takes time to warm up the fixing device during printing, and the printing time (warming-up time) becomes longer.

In order to solve this problem and to make the fixing roller member short in warm-up time with energy saving, it is required to make the fixing roller member thinner.
The fusing roller member is constructed by using a cylindrical elastic body having a heating means (halogen heater) inside, and the fusing roller member is made thinner, the nip width is wide, energy saving and the warming-up time is shortened. And
It is proposed in Japanese Patent Application No. 11-230499.

[0005]

However, in the fixing device using the fixing roller member using the cylindrical elastic body proposed above, the cylindrical elastic body needs to be thinned. However, if the thickness is reduced, the fixing roller member is deformed. As a result, the fixing roller member is damaged (damaged) due to metal fatigue caused by deformation. In addition, the nip width (width of the nip portion) is insufficient, resulting in poor fixing and poor transfer material separation at the nip exit side.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, reduces the thickness of the fixing roller member without damaging the fixing roller member due to metal fatigue, saves energy, shortens the warm-up time, and has a wide nip. It is an object of the present invention to provide a fixing device in which the formation of a portion and the separation performance of a transfer material at a nip portion are improved.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device for fixing a toner image on a transfer material, comprising a fixing roller member having heating means and a pressure roller member facing the fixing roller member. The fixing roller member is made of a thin cylindrical elastic body, and both ends of the fixing roller member are held by a holding member having an inner diameter larger than an outer diameter of the fixing roller member. A fixing device wherein a deformation amount of a fixing roller member is larger than a deformation amount of the pressure roller member (first invention).
Achieved by

The above object is also achieved by providing a fixing device for fixing a toner image on a transfer material by providing a fixing roller member having heating means and a pressure roller member facing the fixing roller member. Is a thin cylindrical elastic body, and both ends of the fixing roller member are held by a holding member having an inner diameter larger than the outer diameter of the fixing roller member, and the outer diameter of the fixing roller member is This is achieved by a fixing device (second invention) characterized in that it is larger than the outer diameter of the pressure roller member.

[0009]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Further, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning or technical scope of the terms of the present invention.

An image forming process and each mechanism of an embodiment of an image forming apparatus using a fixing device according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional configuration view of a color image forming apparatus showing an embodiment of an image forming apparatus using a fixing device according to the present invention, and FIG. 2 is a side cross-sectional view of the image forming body of FIG. FIG. 3 is a schematic sectional view of a fixing device according to the present invention, and FIG. 4 is a schematic side view showing a method of holding the fixing device of FIG.
Is a diagram showing a layer configuration and function of the fixing roller member,
FIG. 6 is a diagram illustrating setting conditions for the amount of deformation of the fixing roller member and the pressing roller member, and FIG. 7 is a diagram illustrating setting conditions for the outer diameters of the fixing roller member and the pressing roller member.

According to FIG. 1 or FIG. 2, a photosensitive drum 10, which is an image forming member, is provided on the outer periphery of a cylindrical base formed of a light-transmitting member such as glass or light-transmitting acrylic resin. It is formed by forming a photoconductive layer and a photoconductor layer of an organic photosensitive layer (OPC).

The photoreceptor drum 10 is rotated clockwise as indicated by an arrow in FIG. 1 by a power from a driving source (not shown) while the light-transmitting conductive layer is grounded.

In the present invention, the exposure beam for image exposure is
The photoconductor layer of the photoconductor drum 10, which is the image forming point, only needs to have an exposure light amount of a wavelength that can provide an appropriate contrast with respect to the light attenuation characteristic (photocarrier generation) of the photoconductor layer. . Therefore, the light transmittance of the light-transmitting substrate of the photosensitive drum in the present embodiment does not need to be 100%, and may have a characteristic of absorbing a certain amount of light when transmitting the exposure beam. . The point is that any suitable contrast can be provided. As a material of the light-transmitting substrate, an acrylic resin, particularly one obtained by polymerizing a methyl methacrylate monomer, is preferably used because of its excellent light-transmitting properties, strength, accuracy, surface properties, etc. Various translucent resins such as acryl, fluorine, polyester, polycarbonate, polyethylene terephthalate and the like used for the above can be used. Further, as long as it has a light-transmitting property with respect to the exposure light, it may be colored. As the light-transmitting conductive layer, indium tin oxide (I
TO), tin oxide, lead oxide, indium oxide, copper iodide, or a metal thin film of Au, Ag, Ni, Al, or the like that maintains light transmissivity. Reactive deposition method, various sputtering methods, various CV
D method, dip coating method, spray coating method and the like can be used.
Various organic photosensitive layers (OPC) can be used as the photoconductor layer.

The organic photosensitive layer serving as the photosensitive layer of the photoconductor layer includes a charge generation layer (CGL) mainly composed of a charge generation substance (CGM) and a charge transport layer (CTM) mainly composed of a charge transport substance (CTM). And CTL). An organic photosensitive layer having a two-layer structure has high durability as an organic photosensitive layer due to its thick CTL and is suitable for the present invention.
The organic photosensitive layer may have a single layer structure containing a charge generation material (CGM) and a charge transport material (CTM) in one layer. ,
Usually, a binder resin is contained.

A scorotron charger 11 as a charging unit described below, and an exposure optical system 1 as an image writing unit will be described.
2. The developing device 13 as a developing unit is prepared for an image forming process for each color of yellow (Y), magenta (M), cyan (C) and black (K), respectively. Are arranged in the order of Y, M, C, and K with respect to the rotation direction of the photosensitive drum 10 indicated by the arrow in FIG.

Scorotron charger 11 as charging means
Is mounted so as to face and be close to the photosensitive drum 10 in a direction perpendicular to the moving direction of the photosensitive drum 10 as an image forming body (the direction perpendicular to the plane of FIG. 1). A control grid (no symbol) maintained at a predetermined potential with respect to the body layer;
As a, for example, a sawtooth electrode is used, and a charging action (in this embodiment, negative charging) is performed by corona discharge having the same polarity as that of the toner, thereby giving a uniform potential to the photosensitive drum 10. As the corona discharge electrode 11a, a wire electrode or a needle electrode may be used.

The exposure optical system 12 for each color has a linear exposure element (LED) in which a plurality of LEDs (light emitting diodes) as light emitting elements for image exposure light are arranged in an array parallel to the axis of the photosensitive drum 10. (Not shown) and a selfoc lens (not shown) as an equal-magnification imaging element are configured as an exposure unit attached to a holder. An exposure optical system 1 for each color is placed on a cylindrical holder 20 as an exposure optical system holding member.
2 is mounted and housed inside the substrate of the photosensitive drum 10. Other exposure elements include FL (phosphor emission),
A linear element in which a plurality of light emitting elements such as EL (electroluminescence) and PL (plasma discharge) are arranged in an array is used.

An exposure optical system 12 serving as an image writing means for each color moves an exposure position on the photosensitive drum 10 between the scorotron charger 11 and the developing device 13 with respect to the developing device 13. It is arranged inside the photoconductor drum 10 in a state provided on the upstream side in the rotation direction of the drum 10.

The exposure optical system 12 performs image processing based on image data of each color sent from a separate computer (not shown) and stored in a memory, and then forms an image on a uniformly charged photosensitive drum 10. Exposure is performed to form a latent image on the photosensitive drum 10. The emission wavelength of the light-emitting element used in this embodiment is usually 6 for the toners of Y, M, and C, which have high translucency.
The wavelength in the range of 80 to 900 nm is good, but the wavelength may be shorter than this, since the color toner does not have sufficient translucency since image exposure is performed from the back surface.

The developing device 13 as a developing means for each color includes
Inside yellow (Y), magenta (M), cyan (C)
Alternatively, it contains a black (K) two-component (or one-component) developer and is formed of, for example, a cylindrical non-magnetic stainless steel or aluminum material having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm, respectively. And a developing sleeve 13a as a developer carrier.

In the developing area, the developing sleeve 13a is kept out of contact with the photosensitive drum 10 with a predetermined gap, for example, 100 to 1000 μm, by abutting rollers (not shown). At the closest position, it rotates in the forward direction, and at the time of development, an AC voltage AC is superimposed on a DC voltage of the same polarity as the toner (in the present embodiment, a negative polarity) or a DC voltage with respect to the developing sleeve 13a. By applying the developing bias voltage, non-contact reversal development is performed on the exposed portion of the photosensitive drum 10. At this time, the precision of the development interval needs to be about 20 μm or less in order to prevent image unevenness.

As described above, the developing unit 13 transfers the electrostatic latent image formed on the photosensitive drum 10 by the charging by the scorotron charger 11 and the image exposure by the exposure optical system 12 in a non-contact state. Reversal development is performed with toner having the same polarity as the charge polarity of No. 10 (in the present embodiment, the photosensitive drum is negatively charged, and the toner has negative polarity).

As shown in FIG. 2, the photosensitive drum 10 and a holder 20 as an exposure optical system holding member rotatably support the photosensitive drum 10 at the rear and front ends of the apparatus. Drum flanges 10A and 10B as photoconductor drum support members, and optical system flanges 120A and 1 as exposure optical system support members that support holder 20
20B is integrally formed through press-fitting or means such as screws. The photoreceptor drum 10 includes a drum flange 10A and a drum flange 10B serving as a photoreceptor drum support member and an optical system flange 120A of the holder 20.
Shaft 121 and optical system flange 1 integrated with each other
20B is rotatably supported via bearings B1 and B2, respectively.

The shaft 121 has a shaft portion 121A for holding the photoreceptor drum 10, and a support shaft 130 as a shaft holding means having an engagement hole 130A is provided on the rear device board 70. The linear bearing B4 is fitted into the engagement hole 130A, and the receiving member 13
The support shaft 130 is fixed to the device substrate 70 on the rear side by screws or the like with the Oa interposed therebetween. The support shaft 130 is located at the center of the gear G2 that meshes with the drive gear G1, and rotatably supports a conductive member 131 that integrates the gear G2 via a bearing B3. On the other hand, the apparatus substrate 70 on the front side of the apparatus has an opening 70A through which the photosensitive drum 10 having the exposure optical system 12 fixed to the holder 20 can be inserted and removed.

The holder 20 inserts the shaft portion 121A of the shaft 121 into the linear bearing B4 provided on the support shaft 130 with respect to the device board 70 on the rear side, and the shaft portion 121A
The engaging pin 121P inserted into the
The exposure optical system 12 is attached by regulating the angular relation position of the exposure optical system 12 by engaging with a V-shaped groove formed on the front side of the exposure optical system 12. With the optical system flange 120C as a support member sandwiching the cushioning material K and pressing the front lid 120D in the axial direction, the screw 5
2 to be mounted at a predetermined position.

A coupling 10C attached to a side surface of a drum flange 10A as a photosensitive drum supporting member for supporting the photosensitive drum 10, a drive pin 131A attached to a side surface of a conductive member 131 integrated with a gear G2;
With the set screw 51, the drum flange 10A and the gear G
When the photosensitive drum 10 with the holder 20 is integrated, the drum flange 1
Coupling 10C attached to the side of 0A is gear G2.
After the engagement, the conductive member 131 having the gear G2 and the photosensitive drum 10 having the drum flange 10A are aligned with the center and the outer peripheral surface. , From the side of the photosensitive drum 10 using the set screw 51
1A and the coupling 10C are fixed, and the drum flange 10A and the gear G2 are connected and fixed.

When the image forming body drive motor (not shown) is started by the start of image formation, the rotational power of the drive gear G1 is transmitted to the photosensitive drum 10 via the coupling portion by the gear G2, and the photosensitive drum 10 is moved to the position shown in FIG. , And at the same time, application of a potential to the photosensitive drum 10 is started by the charging action of the Y scorotron charger 11.
After a potential is applied to the photosensitive drum 10, exposure (image writing) by a first color signal, that is, an electrical signal corresponding to Y image data is started in the Y exposure optical system 12, and the rotation of the photosensitive drum 10 is started. By scanning, an electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the photosensitive layer on the surface. This latent image is reversely developed in a non-contact state by the Y developing device 13, and a yellow (Y) toner image is formed on the photosensitive drum 10.

Next, the photoreceptor drum 10 places an M scorotron charger 11 on the yellow (Y) toner image.
A potential is applied by the charging action of the M exposure optical system 12
Exposure (image writing) is performed using an electrical signal corresponding to the second color signal of m, i.e., magenta (M) image data.
The magenta (M) toner image is formed on the yellow (Y) toner image by non-contact reversal development by the developing device 13.

According to the same process, the cyan (C) toner image corresponding to the third color signal is further obtained by the C scorotron charger 11, the exposure optical system 12, and the developing device 13, and the K scorotron charger 11 , Exposure optical system 1
A black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed by the second and developing units 13, and a color toner image is formed on the peripheral surface within one rotation of the photosensitive drum 10. You.

As described above, in this embodiment, Y, M,
The exposure of the organic photosensitive layer of the photoconductor drum 10 by the C and K exposure optical systems 12 is performed through a transparent substrate from the inside of the photoconductor drum 10. Therefore, the exposure of the image corresponding to the second, third, and fourth color signals can form an electrostatic latent image without being shielded by the previously formed toner image, which is preferable. Photoconductor drum 1
0 may be exposed from outside.

On the other hand, the recording paper P as a transfer material is sent out from a paper feed cassette 15 as a transfer material storage means by a feed roller (no code), fed by a feed roller (no code), and fed to a timing roller. It is conveyed to 16.

The recording paper P is synchronized with the color toner image carried on the photosensitive drum 10 by the driving of the timing roller 16, and the paper charger 1 as paper charging means is synchronized.
Due to the electrification of 50, the toner is attracted to the conveyor belt 14a and fed to the transfer area. The recording paper P, which is closely transported by the transport belt 14a, is moved around the photosensitive drum 10 by a transfer unit 14c as a transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied in a transfer area. The color toner images on the surface are collectively transferred to the recording paper P.

The recording paper P on which the color toner image has been transferred is
The paper is discharged by a paper separation AC neutralizer 14h as a transfer material separating unit, separated from the transport belt 14a, and transported to the fixing device 17.

As will be described in detail later, the fixing device 17 includes a resin bearing 171j as a ring-shaped holding member.
The fixing roller 17a is a thin plate-like fixing roller 17a which is an upper fixing roller member (on the side of the color toner image on the recording paper P) for fixing a color toner image, and a pressing roller member which is a lower hard roller. A halogen heater 171g, which is a heating unit having a heating filament as a heat source, is provided inside the fixing roller 17a.

The recording paper P is nipped by a nip N formed between the fixing roller 17a and the pressure roller 47a, which is a hard roller.
The upper color toner image is fixed, and the recording paper P is fed by the paper discharge rollers 18 and discharged to the tray on the upper part of the apparatus.

The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is transferred to a cleaning blade 19 provided in a cleaning device 19 as an image forming body cleaning means.
Cleaning is performed by a. The photosensitive drum 10 from which the residual toner has been removed is uniformly charged by the scorotron charger 11, and enters the next image forming cycle.

According to FIG. 3 to FIG.
Is a thin cylindrical elastic body on the upper side (on the side of the color toner image on the recording paper P) which is held by a resin bearing 171j as a ring-shaped holding member and has a spring property for fixing the color toner image. A fixing roller 17a as a fixing roller member using the thin plate elastic roller 171a is disposed, and a pressing roller 47a as a pressing roller member as a hard roller is disposed below the fixing roller 17a. Inside the roller 17a, there is provided a halogen heater 171g, which is a heating means having a heat generating filament (no symbol) as a heat source.

As shown in FIG. 5, the upper fixing roller 17a, which is a thin plate-like fixing roller member, includes a thin plate elastic roller 171a which is a thin cylindrical elastic body having a spring property and an outer side of the thin plate elastic roller 171a. (Outer peripheral surface) rubber layer 17
1b.

The thickness (thickness) t (mm) of the thin plate elastic roller 171a is 0.07 to 0.7, although it depends on the diameter.
For example, nickel having a thickness of about 0 mm can be used, but a spring material having a fatigue limit which can be used as a spring material is preferably formed of a thin metal member having a spring property using stainless steel, phosphor bronze, or the like. By using the metallic member of the above, it is possible to prevent the occurrence of fatigue failure due to the elastic deformation of the thin plate elastic roller 171a that is a cylindrical elastic body when the thin plate elastic roller 171a is applied to the fixing device 17. In preventing the occurrence of fatigue failure due to elastic deformation, at Plane Bending Fatigue Test method (JIS, Z2275), by repeating several 10 ⁷ times, a thin metal plate (thin) with 140 N / mm ² or more fatigue strength It has been experimentally confirmed that it is preferable to use a conductive member.

The thickness t of the thin plate elastic roller 171a is
(Mm), the outer diameter of the thin plate elastic roller 171a is R
(Mm), the following condition is satisfied: R / 50>t> R / 300.
In this case, the width of the nip portion N can be increased to 5 to 20 mm without deformation or breakage. Outer diameter R of thin plate elastic roller 171a
Is preferably 15 to 40 mm. t ≧ R / 5
In the case of 0, when the thin plate elastic roller 171a is too thick and applied to the fixing device 17, it does not deform into an elliptical shape and the width of the nip portion N does not become wide. There is also a disadvantage that the rate of temperature rise is slow due to a large heat capacity. When t ≦ R / 300, the thickness of the thin plate elastic roller 171a is too thin, and when applied to the fixing device 17, the strength is too low and the pressing force is insufficient, resulting in uneven fixing. Further, the heat capacity is small, which causes a temperature difference during paper passing.

Outside (outer peripheral surface) of the thin plate elastic roller 171a
As the rubber layer 171b provided on the base material, a rubber hardness of 10 Hs to 70 Hs (JI
S, A rubber hardness), preferably 15Hs to 40Hs,
The layer thickness is preferably about 0.3 to 1 mm. By providing the rubber layer 171b, occurrence of fixing unevenness is reduced. Thereby, it can be used also as a fixing device for color fixing that can give glossiness.

The pressure roller 47a as the lower pressure roller member is, for example, a rod-shaped metal pipe 471a made of a stainless steel material, and a rubber material having a rubber hardness of 20 Hs or more made of, for example, a silicon material outside the metal pipe 471a. 80Hs (J
IS, A rubber hardness), preferably 30Hs to 50Hs
Thus, a hard roller having a rubber roller layer 471b with a thickness of 3 mm to 10 mm is formed. Fixing roller 17
a presses (presses) the pressing roller 47a (the pressing roller 47a may press the fixing roller 17a), and the nip portion N is formed.

As the lower pressure roller 47a, a hard rubber roller having high heat insulation is used, and the upper thin elastic roller 171 is used.
In addition to preventing the diffusion of heat from a to the lower pressure roller 47a, a nip width of about 5 to 20 mm is secured.

As shown in FIG. 4, both ends of the fixing roller 17a are penetrated through a fixing roller 17a which is a fixing roller member using a thin plate elastic roller 171a which is a thin cylindrical elastic body having a spring property. For example, a resin bearing 171j as a ring-shaped holding member using a heat-insulating resin member such as a fluororesin is fitted, and both ends of the fixing roller 17a are used as holding members having an inner diameter larger than the outer diameter of the fixing roller 17a. It is held by a resin bearing 171j. The fixing roller 17a integrated with the resin bearings 171j at both ends is rotatable by bearings B5 as bearing members fitted into the resin bearings 171j as holding members at both ends. At this time, both ends of the bearing B5
It is also possible to directly hold the fixing roller 17a. A receiving plate PL made of a resin member having good slipperiness using, for example, fluororesin is provided on both ends of the fixing roller 17a.
b, and the fixing roller 17a is positioned from both ends.

The center positions of the bearing bearings B5 at both ends, which are fitted so as to coincide with the center positions of the resin bearings 171j at both ends provided through the fixing roller 17a, are fixed by a pressing spring SPa, for example, 50 to 50%. With a load of 500N, the fixing roller 17 is fixed via the resin bearing 171j.
is pressed to fix the fixing roller 17a and the pressure roller 47a. The center between the center positions of the holding portions of bearing bearings B5 as the bearing members pressed by the pressing springs SPa at both ends (positional intervals of the width indicated by L1 in FIG. 4) is the center position of the resin bearing 171j as the holding member at both ends. Resin bearings 171j and bearings B5 at both ends are provided with the same spacing. This prevents deformation of the end of the thin plate elastic roller 171a which is pressed by the pressing roller 47a narrower than the fixing roller 17a.

The lower pressure roller 47a is provided with a gear G12 fixed to one end of a metal pipe 471a of the pressure roller 47a, and a gear G22 driven and rotated by a fixing drive motor M1. The fixing roller 17a is connected to the gear G12, and rotates the pressing roller 47a by driving the fixing driving motor M1, so that the fixing roller 17 is pressed by the pressing roller 47a.
a is driven to rotate. Following rotation, the fixing roller 17
The rotation of a is made uniform, and uneven fixing is prevented.

The rubber layer 171b of the above-described fixing roller 17a, which is indicated by oblique lines in FIG.
It is preferable that the rubber layer 171b is prevented from being scraped by the resin bearing 171j when the fixing roller 17a is rotated.

As described above, the fixing roller 17a serving as the fixing roller member is a thin thin elastic roller 171a having a spring property, and the resin bearing 171j holding the fixing roller 17a is pressed, and the pressure roller serving as the hard roller is pressed. The pressing force of the roller 47a is received by the elastic force of the thin plate elastic roller 171a of the fixing roller 17a (the pressing roller 47a is pressed against the fixing roller 17a, and the pressing force with the pressing roller 47a is reduced by the spring property of the fixing roller 17a. It may be received by the elastic force of the thin elastic roller 171a. As a result, the thin elastic roller 171a expands in an elliptical shape without plastic deformation, and the pressure roller 4 which is a hard roller.
The thin plate elastic roller 171a is pressed against 7a, and a slightly convex nip portion N having a width of about 5 to 20 mm is formed on the upper side.

As described above, the nip width is 5 to 20 by the cylindrical elastic body and the pressure roller member which is a hard roller.
mm, so that a fixing device that saves energy and has a short warming-up time can be realized. In order to secure a wider nip portion N, the curvature of the nip portion N is set so that the thin elastic roller 1
The elastic force of 71a and the rubber roller layer 47 of the pressure roller 47a
It is necessary to balance with the rubber hardness of 1b, but the radius of curvature of the nip N formed on the fixing roller 17a side by the fixing roller 17a and the pressing roller 47a is 5
It is preferable to set it to 0 mm or more. As a result, the occurrence of poor fixing and wrinkling on thick paper, particularly the occurrence of fixing wrinkles on a double transfer material such as an envelope, is reduced. Further, the large curvature (the radius of the curved surface is small) of the thin plate elastic roller 171a of the fixing roller 17a at the exit of the nip N improves the separability from the recording paper P.

As described above, the thickness of the fixing roller member can be reduced without plastic deformation by the thin cylindrical elastic body, and the fixing roller member can be stably held by the bearing member, and the nip width is 5 to 20 mm. It is possible to provide a fixing device that is somewhat wider, saves energy, and has a shorter warm-up time.

However, in the fixing device 17, in the fixing roller 17a using the pressing roller 47a as a hard roller and the thin plate elastic roller 171a as a cylindrical elastic member pressed against each other, the width of the nip portion N is insufficient. There is a problem that the transfer material is poor or the transfer material at the exit side of the nip portion N has poor separability.

It is preferable to set the following conditions in order to solve the above problem and secure a wide nip portion of about 15 to 30 mm and improve the separation performance of the transfer material.

First, as described above with reference to FIG. 4, the fixing roller 17a as a fixing roller member is pressed (pressed) against a pressing roller 47a as a pressing roller member (the pressing roller 47a is fixed). The nip portion N is formed. However, as shown in FIG. 6, the fixing roller 17a is pressed against the fixing roller 17a and the pressing roller 47a. The deformation amount ΔD1 (mm) of the elastic roller 171a is
It is preferable to set larger than the deformation amount ΔD2 (mm) of 7a (ΔD1> ΔD2). That is, the pressure roller 47a
Is hardened, the deformation amount of the thin plate elastic roller 171a is kept constant, and the fixing unevenness caused by the rotation unevenness due to the deformation of the fixing roller 17a is prevented, and the damage (breakage) due to metal fatigue is prevented.
The width of the wide nip portion N of about 15 to 30 mm is obtained by using the elastic force of the recording paper P at the exit side of the nip portion N.
To improve the separation performance.

As a constant load, for example, a load of 50 to 500 N, a thin elastic roller 171 of the fixing roller 17a is used.
It has been experimentally confirmed that the deformation amount ΔD1 of the pressure roller a is approximately 3 to 10 mm, and the deformation amount ΔD2 of the pressure roller 47a is preferably approximately 1 to 5 mm. 17a deformation amount ΔD1 (mm)
Ratio of the pressure roller 47a to the deformation amount ΔD2 (mm), Δ
It is preferable to set D1 / ΔD2 to ΔD1 / ΔD2 = 2 to 5. The value of the ratio ΔD1 / ΔD2 is set to 2 or more so that the pressure roller 47a is too soft and the width of the nip portion N is too small or the separation performance is not reduced. The value of the ratio ΔD1 / ΔD2 is set to 5 or less so that the thin elastic roller 171a of the fixing roller 17a is not too hard, the deformation of the fixing roller 17a is small, and the width of the nip N is not too narrow.

In the above description, the fixing roller 17a, which is the upper thin plate-shaped fixing roller member, is composed of the thin elastic roller 171a, which is a thin cylindrical elastic body having spring properties, as described above with reference to FIG. The elastic roller 171a has a layer configuration including a rubber layer 171b on the outer side (outer peripheral surface).

The thickness (thickness) t (mm) of the thin plate elastic roller 171a is 0.07 to 0.7, although it depends on the diameter.
For example, nickel having a thickness of about 0 mm can be used, but a spring material having a fatigue limit which can be used as a spring material is preferably formed of a thin metal member having a spring property using stainless steel, phosphor bronze, or the like. By using the metallic member of the above, it is possible to prevent the occurrence of fatigue failure due to the elastic deformation of the thin plate elastic roller 171a that is a cylindrical elastic body when the thin plate elastic roller 171a is applied to the fixing device 17. In preventing the occurrence of fatigue failure due to elastic deformation, at Plane Bending Fatigue Test method (JIS, Z2275), by repeating several 10 ⁷ times, a thin metal plate (thin) with 140 N / mm ² or more fatigue strength It has been experimentally confirmed that it is preferable to use a conductive member.

The thickness t of the thin elastic roller 171a is
(Mm), the outer diameter of the thin plate elastic roller 171a is R
(Mm), the following condition is satisfied: R / 50>t> R / 300.
In this case, the width of the nip portion N can be increased to 5 to 20 mm without deformation or breakage. Outer diameter R of thin plate elastic roller 171a
Is preferably 15 to 40 mm. t ≧ R / 5
In the case of 0, when the thin plate elastic roller 171a is too thick and applied to the fixing device 17, it does not deform into an elliptical shape and the width of the nip portion N does not become wide. There is also a disadvantage that the rate of temperature rise is slow due to a large heat capacity. When t ≦ R / 300, the thickness of the thin plate elastic roller 171a is too thin, and when applied to the fixing device 17, the strength is too low and the pressing force is insufficient, resulting in uneven fixing. Further, the heat capacity is small, which causes a temperature difference during paper passing.

Outside (outer peripheral surface) of the thin plate elastic roller 171a
As the rubber layer 171b provided on the base material, a rubber hardness of 10 Hs to 70 Hs (JI
S, A rubber hardness), preferably 15Hs to 40Hs,
The layer thickness is preferably about 0.3 to 1 mm. By providing the rubber layer 171b, occurrence of fixing unevenness is reduced. Thereby, it can be used also as a fixing device for color fixing that can give glossiness.

The pressure roller 47a as the lower pressure roller member is composed of, for example, a rod-shaped metal pipe 471a made of a stainless steel material, and a silicon material made of a silicon material outside the metal pipe 471a and having a rubber hardness of 20 Hs. ~ 80Hs
(JIS, A rubber hardness), preferably 30Hs-50H
s, and is configured as a hard roller on which a rubber roller layer 471b having a thickness of 3 mm to 10 mm is formed.

The fixing roller 17a presses (presses) the pressing roller 47a (the pressing roller 47a
May be pressed). A wide nip portion N of about 15 to 30 mm is formed.

By setting the above conditions, it is possible to prevent the fixing roller member from being damaged (damage) due to metal fatigue from deformation of the cylindrical elastic body by using the thinned elastic body, and
By increasing the amount of deformation of the cylindrical elastic body of the fixing roller member,
The transfer material separation performance at the nip exit side is improved,
In addition, the spread of the nip portion is ensured, and the fixing property is improved.

Second, as described above with reference to FIG. 4, the fixing roller 17a as a fixing roller member is pressed (pressed) against a pressing roller 47a as a pressing roller member (the pressing roller 47a is 17a), a nip portion N is formed. As shown in FIG. 7, the outer diameter D1 (mm) of the fixing roller 17a (the outer diameter D1 of the fixing roller 17a is Elastic roller 171a
Is substantially equal to the outer diameter R of the pressure roller 47a.
(D1> D2) is preferably set to be larger than (mm). The outer diameter D1 of the fixing roller 17a is
By making the diameter larger than the outer diameter D2 of a, the separation performance of the recording paper P is improved, and a wide nip portion N of about 15 to 30 mm is secured to improve the fixing performance.

The fixing roller 17a has an outer diameter D1 of 2
Experiments have been conducted using a roller having an outer diameter D2 of about 15 to 40 mm as a pressure roller 47a using a roller having a diameter of about 0 to 50 mm. To secure and improve the fixing performance, the ratio of the outer diameter D1 (mm) of the fixing roller 17a to the outer diameter D2 (mm) of the pressure roller 47a, D1 / D2, is D1 / D2 = 1.2. It has been experimentally confirmed that it is preferable to set the value to 2.0.

In addition to the above settings, in order to improve the separation performance of the recording paper P, secure a wide nip N, and improve the fixing performance, the fixing roller 17a described with reference to FIG.
And the pressing roller 47a, for a constant load.
Deformation amount Δ of thin plate elastic roller 171a of fixing roller 17a
D1 (mm) is determined by the deformation amount ΔD2 (m
m) (ΔD1> ΔD2) is preferable (see FIG. 6).

As described above with reference to FIG. 5, the fixing roller 17a, which is a thin plate-like fixing roller member on the upper side, includes a thin plate elastic roller 171a, which is a thin cylindrical elastic body having spring properties, and The elastic roller 171a has a layer configuration including a rubber layer 171b on the outer side (outer peripheral surface).

The thickness (thickness) t (mm) of the thin plate elastic roller 171a is 0.07 to 0.7, depending on the diameter.
For example, nickel having a thickness of about 0 mm can be used, but a spring material having a fatigue limit which can be used as a spring material is preferably formed of a thin metal member having a spring property using stainless steel, phosphor bronze, or the like. By using the metallic member of the above, it is possible to prevent the occurrence of fatigue failure due to the elastic deformation of the thin plate elastic roller 171a that is a cylindrical elastic body when the thin plate elastic roller 171a is applied to the fixing device 17. In preventing the occurrence of fatigue failure due to elastic deformation, at Plane Bending Fatigue Test method (JIS, Z2275), by repeating several 10 ⁷ times, a thin metal plate (thin) with 140 N / mm ² or more fatigue strength It has been experimentally confirmed that it is preferable to use a conductive member.

The thickness t of the thin plate elastic roller 171a
(Mm), the outer diameter of the thin plate elastic roller 171a is R
(Mm), the following condition is satisfied: R / 50>t> R / 300.
In this case, the width of the nip portion N can be increased to 5 to 20 mm without deformation or breakage. Outer diameter R of thin plate elastic roller 171a
Is preferably 15 to 40 mm. t ≧ R / 5
In the case of 0, when the thin plate elastic roller 171a is too thick and applied to the fixing device 17, it does not deform into an elliptical shape and the width of the nip portion N does not become wide. There is also a disadvantage that the rate of temperature rise is slow due to a large heat capacity. When t ≦ R / 300, the thickness of the thin plate elastic roller 171a is too thin, and when applied to the fixing device 17, the strength is too low and the pressing force is insufficient, resulting in uneven fixing. Further, the heat capacity is small, which causes a temperature difference during paper passing.

Outside (outer peripheral surface) of the thin plate elastic roller 171a
As the rubber layer 171b provided on the base material, a rubber hardness of 10 Hs to 70 Hs (JI
S, A rubber hardness), preferably 15Hs to 40Hs,
The layer thickness is preferably about 0.3 to 1 mm. By providing the rubber layer 171b, occurrence of fixing unevenness is reduced. Thereby, it can be used also as a fixing device for color fixing that can give glossiness.

The pressure roller 47a as the lower pressure roller member is composed of, for example, a rod-shaped metal pipe 471a made of stainless steel, and a silicon material made of, for example, silicon outside the metal pipe 471a and having a rubber hardness of 20 Hs. ~ 80Hs
(JIS, A rubber hardness), preferably 30Hs-50H
s, and is configured as a hard roller on which a rubber roller layer 471b having a thickness of 3 mm to 10 mm is formed.

The fixing roller 17a presses (presses) the pressing roller 47a (the pressing roller 47a
May be pressed). A wide nip portion N of about 15 to 30 mm is formed.

By setting the above conditions, it is possible to prevent the fixing roller member from being damaged (damage) due to metal fatigue from deformation of the cylindrical elastic body by using the thinned elastic body, and
By making the fixing roller member larger in diameter than the pressure roller member, a wide nip portion can be formed even if the amount of deformation is small, and the fixing property is improved.

[0072]

According to the first aspect of the present invention, the fixing roller member is prevented from being damaged due to metal fatigue caused by deformation of the cylindrical elastic body by using the thinned-walled elastic body.
By increasing the amount of deformation of the cylindrical elastic body of the fixing roller member,
The transfer material separation performance at the nip exit side is improved,
In addition, the spread of the nip portion is ensured, and the fixing property is improved.

According to the second aspect of the present invention, the fixing roller member is prevented from being damaged by metal fatigue due to deformation of the cylindrical elastic body, and the fixing roller member is connected to the pressing roller member. By making the diameter larger, a wide nip portion is formed even if the deformation amount is small, and the fixing property is improved.

According to the third aspect, it is possible to increase the nip width without deformation and breakage of the cylindrical elastic body, and to obtain an appropriate pressing force.

[Brief description of the drawings]

FIG. 1 is a sectional view of a color image forming apparatus showing an embodiment of an image forming apparatus using a fixing device according to the present invention.

FIG. 2 is a side sectional view of the image forming body of FIG. 1;

FIG. 3 is a schematic sectional view of a fixing device according to the present invention.

FIG. 4 is a schematic side view showing a method for holding the fixing device of FIG. 3;

FIG. 5 is a diagram illustrating a layer configuration and a function of a fixing roller member.

FIG. 6 is a diagram illustrating a setting condition of a deformation amount of a fixing roller member and a pressure roller member.

FIG. 7 is a diagram showing conditions for setting outer diameters of a fixing roller member and a pressure roller member.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 17 fixing device 17a fixing roller 47a pressure roller 171a thin plate elastic roller 171j resin bearing 171g halogen heater B5 bearing bearing N nip P recording paper

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yotaro Sato 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H033 AA30 AA32 BB12 BB14 BB15 BB29 BB36

Claims (3)

[Claims] A fixing roller member having a heating unit; and a pressure roller member facing the fixing roller member.
In a fixing device for fixing a toner image on a transfer material, the fixing roller member is formed of a thin cylindrical elastic body, and both ends of the fixing roller member are held with an inner diameter larger than an outer diameter of the fixing roller member. A fixing device, wherein the amount of deformation of the fixing roller member with respect to a constant load is larger than the amount of deformation of the pressure roller member. 2. A fixing roller member having heating means, and a pressure roller member facing the fixing roller member are provided.
In a fixing device for fixing a toner image on a transfer material, the fixing roller member is formed of a thin cylindrical elastic body, and both ends of the fixing roller member are held with an inner diameter larger than an outer diameter of the fixing roller member. A fixing device, wherein an outer diameter of the fixing roller member is larger than an outer diameter of the pressure roller member. 3. An outer diameter of the cylindrical elastic body is R (mm),
The fixing device according to claim 1, wherein when a thickness of the cylindrical elastic body is t (mm), R / 50>t> R / 300.