JP2001166617A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of shortening the warming up time by accelerating the temperature rise of a belt member low in thermal conductivity, capable of excellently fixing the toner image on the transfer material in a nip part with less fixation unevenness by eliminating the temperature change of the belt member and the nonuniformity of the temperature at the time of continuous printing, and having a property adaptable to a high-speed fixation, high in heating effect and high in thermal efficiency. SOLUTION: A planar fixed heat generating body for heating the belt member abutting on the belt member from the inside of the belt member is arranged between a 1st fixing roller member and a heat generating roller member, then the transfer material is preliminarily heated by being electrostatically brought into tight contact with the belt member, and the toner image on the transfer material is fixed in the nip part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt-type fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, a fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile or the like includes a heating rubber roller having an elastic layer and maintained at a predetermined temperature, and a heating rubber roller. A heat roller fixing method in which a transfer material on which an unfixed toner image is formed is heated while being nipped and conveyed by a pressurized rubber roller having an elastic layer while being pressed against the roller.

However, in this type of apparatus, the heat capacity of the heat-generating rubber roller is large, so that the warm-up time is long, the temperature inside the elastic layer is high, and the life of the heat-generating rubber roller is shortened.

Further, many color images have a large solid area, and many of the solid images are other than black, so that uneven gloss is noticeable. When a hard roller is used as the heating rubber roller and the pressure rubber roller, there is a problem that image quality is deteriorated because uneven gloss is generated in accordance with unevenness of the paper or toner layer.

In order to solve the above problem, a heat roller (heat roller member) for heating the belt member is provided inside the belt member using a metal belt (belt member) provided with a rubber layer, and the heat roller is used to heat the heat. Japanese Patent Application Laid-Open No. Hei 9-138599 discloses a fixing method for fixing a toner image on a transfer material at a nip portion provided on the downstream side of a heating roller in the rotation direction of the belt member. I have.

[0006]

However, in the fixing device disclosed in Japanese Patent Application Laid-Open No. 9-138599, a good image quality is obtained by using a belt member (metal belt) having an elastic layer (rubber layer). However, the temperature rise of the belt member having poor thermal conductivity is slow due to the elastic layer, so that it takes time to warm up.
In addition, when the temperature is excessively increased, the belt member is deteriorated mainly at the interface between the elastic layer and the base member of the belt member, and the transfer at the nip portion is caused by the temperature change and uneven temperature of the belt member during continuous printing. At the time of fixing a toner image on a material, there arises a problem that fixing unevenness occurs and good fixability cannot be obtained. Further, a guide member before fixing is provided on the lower surface of the belt member, and the transfer material is warmed by the residual heat gap between the heated belt member and the guide member. However, there is a problem that the heating effect is small.

The present invention solves the above problems, speeds up the temperature rise of a belt member having poor thermal conductivity, shortens the warm-up time, and reduces the temperature change and uneven temperature of the belt member during continuous printing. A fixing device that eliminates the problem of fixing unevenness when fixing a toner image on a transfer material at a nip portion, has high-speed responsiveness, has a large heating effect, and has high thermal efficiency. The purpose is to provide.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a first fixing roller member which stretches a belt member on one side, and a heat generating roller which stretches the other side of the belt member together with the first fixing roller member. Member and the belt member,
And a second fixing roller member provided to face the fixing roller member and forming a nip between the first fixing roller member and the first fixing roller member. In between, a planar fixed heating element that contacts the belt member from the inside of the belt member and heats the belt member is provided, and the transfer material is electrostatically brought into close contact with the belt member to perform preheating. And fixing the toner image on the transfer material at the nip portion.

[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. 3 is an explanatory diagram of a first example of the structure of the fixing device and the application of the bias voltage on the belt member side, and FIG. 4 is an explanatory diagram of a second example of the application of the bias voltage on the belt member side. Yes, FIG.
FIG. 6 is a diagram illustrating a third example of the application of a bias voltage on the belt member side. FIG. 6 is a diagram illustrating a heat equalizing member provided on a fixed heating element of the fixing device in FIG. 3, and FIG. FIG. 8 is a diagram showing a first example of application of a bias voltage on the material side, and FIG.
FIG. 9 is a diagram illustrating a second example of application of a bias voltage on the transfer material side, and FIG. 9 is a diagram illustrating another example of the structure of the fixing device.

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. Cylindrical holding member 2
At 0, the exposure optical system 12 for each color is attached and housed inside the base of the photosensitive drum 10. In addition, as the exposure element, a linear element in which a plurality of light emitting elements such as FL (phosphor emission), 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 serving as photosensitive drum support members and optical system flanges 120A and 120B serving as exposure optical system support members that support holder 20.
And are integrally formed via means such as press fitting or screws. The photosensitive drum 10 includes a drum flange 10A as a photosensitive drum support member and a drum flange 1.
0B is the bearing B1 and the bearing B respectively with respect to the shaft 121 and the optical system flange 120B integrated with the optical system flange 120A of the holder 20.
It is rotatably supported via 2.

The shaft 121 has a shaft portion 121A for holding the photoreceptor drum 10, and an apparatus shaft 70 on the back side is provided with a support shaft 130 as shaft holding means having an engagement hole 130A. The linear bearing B4 is fitted into the engagement hole 130A, and the receiving member 130
The support shaft 130 is fixed to the device substrate 70 on the rear side by screws or the like with the a 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. The optical system flange 120C, which is a support member, is
With the front lid 120D pressed in the axial direction.
It is mounted at a predetermined position by fixing with.

A coupling 10C attached to the side surface of a drum flange 10A which is 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, and a set screw 51, the drum flange 10A and the gear G2
When the photoreceptor drum 10 having the holder 20 is integrated, the drum flange 10
A coupling 10C attached to the side of A is a drive pin 1 attached to the side of a conductive member 131 having a gear G2.
31A, and after engagement, the photoconductive drum 1 having the conductive member 131 having the gear G2 and the drum flange 10A
The drive pin 131 is set from the side of the photoreceptor drum 10 by using the set screw 51 with the center and the outer peripheral surface aligned.
A and the coupling 10C are fixed, and the drum flange 1
0A 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 by the first color signal, that is, an electric signal corresponding to Y image data is started in the Y exposure optical system 12, and the surface of the photosensitive drum 10 is rotated by the rotational scanning. An electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the photosensitive layer. 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 is performed using an electrical signal corresponding to the second color signal of m, i.e., magenta (M) image data.
Yellow (Y) by non-contact reversal development
A toner image of magenta (M) is formed on the toner image of FIG.

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 separated from the conveyor belt 14 a by a static electricity eliminator 14 h as a transfer material separating unit, and is conveyed to the fixing device 700. In this state, the recording paper P is charged to a positive polarity, and the toner of the negative polarity on the recording paper P is on the upper side.

The fixing device 700 includes a first fixing roller 17a as a first fixing roller member on one side, a heating roller 17A as a heating roller member on the other side, and a first fixing roller 17A.
A fixing belt 27A as a belt member stretched around the fixing roller 17a and the heat generating roller 17A;
A second fixing roller 17b as a second fixing roller member provided opposite to the first fixing roller 17a with A interposed therebetween;
It is composed of a guide plate 173 and an introduction plate 174 as an introduction member attached to the guide plate 173. A halogen lamp HL1 as a heat ray irradiating means for emitting heat rays such as infrared rays or far infrared rays for heating the heat generation roller 17A is provided inside the heat generation roller 17A as a heat generation roller member.
And a xenon lamp (not shown). The fixing belt 2 has a ceramic heater 171 as a heating element.
A heating element unit 170 as a planar fixed heating element for heating 7A is provided in contact with (in contact with) the fixing belt 27A inside. A nip portion N is formed between the first fixing roller 17a and the second fixing roller 17b with the fixing belt 27A interposed therebetween. Below the fixing belt 27A, there is provided a guide plate 173 that receives the heat of the fixing belt 27A to form a residual heat gap (remaining heat region).
Then, the recording paper P is introduced into the fixing belt 27A and brought into close contact therewith.
An introduction plate 174 is provided as an introduction member for transporting the recording paper P as a transfer material to the nip portion N.

The recording paper P, which has been brought into close contact with the fixing belt 27A by the introduction plate 174, is conveyed while receiving the residual heat from the guide plate 173 and the preliminary heating from the fixing belt 27A, which has been brought into close contact therewith. Roller 17b
Into the nip N between
Heating of the fixing belt 27A by heat and the first fixing roller 1
7a and the pressure by the second fixing roller 17b,
The color toner image on the recording paper P is fixed.

The recording paper P on which the color toner image has been fixed is sent by a paper discharge roller 18 and discharged to a tray at the top 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.

As shown in FIG. 3, the fixing device 700 includes a first fixing roller 1 serving as a first fixing roller member on one side.
7a, a heating roller 17A as a heating roller member on the other side, a first fixing roller 17a and a heating roller 1A.
Fixing belt 27A as belt member stretched around 7A
A second fixing roller 17b as a second fixing roller member provided opposite to the first fixing roller 17a with the fixing belt 27A interposed therebetween, a guide plate 173, and a guide plate 173.
And an introduction plate 174 as an introduction member attached to the main body. Under the fixing belt 27A, a fixing belt 2 is provided.
A guide plate 173 that receives the heat of 7A and forms a preheat gap (preheat region) is provided.
An introduction plate 174 is provided as an introduction member that introduces the recording paper P to the fixing belt 27A, makes the recording paper P adhere to the fixing belt 27A, and conveys the recording paper P as a transfer material to the nip N. A wide contact portion (preliminary heating area) M of the recording paper P with the fixing belt 27A is formed on the downstream side of the heating roller 17A in the rotation direction of the fixing belt 27A (the contact portion M is on the upstream side of the heating roller 17A).
Is formed).

Heat generation roller 17A as heat generation roller member
A halogen lamp HL1 and a xenon lamp (not shown) are provided inside as a heat ray irradiating means for emitting heat rays such as infrared rays or far infrared rays for heating the heat generating roller 17A.

A ceramic heater 1 as a heating element
A heating element unit 170 having, for example, a rectangular fixed heating element having a surface shape for heating the fixing belt 27A and having a width corresponding to the maximum transfer material size to be used is provided in a direction in which the fixing belt 27A rotates. On the downstream side of the roller 17A,
It contacts (contacts) the inside (inner peripheral surface) of the fixing belt 27A,
The fixing belt 27 </ b> A is provided in parallel with the heating roller 17 </ b> A and is heated by the heating unit 170. Wide contact area of recording paper P with fixing belt 27A (preheating area)
M is formed on the back surface of the heating element unit 170. The heating element unit 170 contacts (contacts) the inside (inner peripheral surface) of the fixing belt 27A in the rotation direction of the fixing belt 27A and on the upstream side of the heat generating roller 17A, as shown by a dashed line in FIG. It may be provided. In these cases,
The ceramic heater 171 as the heating element does not necessarily need to be in direct contact with the fixing belt 27A, and may be configured to contact the fixing belt 27A via the heater holder 172.

The heater holder 172 and the ceramic heater 171 provided in the heating element unit 170 as a planar fixed heating element have a radius of curvature R on the contact surface side (contact surface side) of 1.
A wide heating portion having a thickness of 00 to 1000 mm is formed and is brought into contact (contact) with the fixing belt 27A as a belt member.
Heater holder 172 provided on heating element unit 170
And a contact surface (contact surface) of the ceramic heater 171 with the fixing belt 27A (in a case where the ceramic heater 171 is not in direct contact with the fixing belt 27A, a contact surface (contact surface) of the heater holder 172 with the fixing belt 27A. Face)
In order to make the sliding with the fixing belt 27A good, it is preferable to apply a fluorine coating process of about 5 to 20 μm, and the inside of the fixing belt 27A (the inner peripheral surface) is also fixed. In order to improve the slip, it is preferable to apply a fluorine coating.

A fixing belt 27A as a belt member
Is provided with a fixing separation claw TR3, a fixing oil cleaning roller TR1, and an oil application roller TR2 in the rotation direction of the fixing belt 27A from the position of the nip portion N, and a felt member impregnated with oil is provided by a cylindrical aluminum pipe or the like. Oil is applied to the fixing belt 27A by an oil application roller TR2 wound around a paper tube or the like. The oil on the peripheral surface of the fixing belt 27A is cleaned by the fixing oil cleaning roller TR1.

The fixing belt 27A serving as a belt member has an inner diameter of about 80 to 150 mm and a thickness of about 20 to 150 mm.
On the outside (outer peripheral surface) of a metal belt using, for example, a nickel electroformed belt having a thickness of about 30 to 300 μm.
One coated with about m of insulating silicon rubber is used.

Heating roller 17A as heating roller member
The outer diameter is about 20-40mm and the thickness is 0.5-2m
A metal pipe made of an aluminum material and having a thickness of about 10 to 100 μm coated with a fluororesin is used on the outside (outer peripheral surface). Inside the heating roller 17A, a halogen lamp HL1 or a xenon lamp (not shown) is provided as a heat ray irradiating unit for emitting heat rays such as infrared rays or far infrared rays for heating the heating roller 17A.

Ceramic heater 171 as heating element
Is formed integrally with the heater holder 172 in a state of being in contact with or not in contact with the fixing belt 27A to form the heating element unit 170. The alumina substrate has a thickness of about 0.5 to 2 mm and a width of about 5 to 25 mm. In this case, a layer in which a resistance heating layer and an overcoat glass having a thickness of about 10 μm as a surface protection layer are sequentially provided by thick film printing is used.
The thermal resistance between the fixing belt 27A and the ceramic heater 171 is reduced by the overcoat glass as the surface protection layer. The surface protective layer also functions to protect the resistance heating layer and prevent the fixing belt 27A from being worn. Further, when the ceramic heater 171 is in contact with the fixing belt 27A, a smooth surface such as a fluorine coat is provided on at least the contact surface of the ceramic heater 171 with the fixing belt 27A to facilitate rotation with the fixing belt 27A. The ceramic heater 171 as a heating element provided in the heating element unit 170 as a planar fixed heating element enables responsive heating of the fixing belt 27A.

The heater holder 172 for holding the ceramic heater 171 has a width of 10 to 100 mm, preferably 30 to 100 mm.
Approximately 70 mm, and is formed of a metal member having good thermal conductivity using, for example, aluminum or iron. At the same time, it serves as a travel guide for the fixing belt 27A. Heater holder 172
A smooth surface such as a fluorine coat is provided on at least the contact surface with the fixing belt 27A to facilitate the rotation with the fixing belt 27A.

The first fixing roller 17a as an upper first fixing roller member is provided with a foamed silicone rubber layer (unsigned) on the outside (outer peripheral surface) of a metal pipe (unsigned) having an outer diameter of about 10 to 15 mm. It is a low-hardness sponge roller (soft roller) having an outer diameter of about 15 to 25 mm and a rubber hardness of 20 to 60 Hs (JIS, A rubber hardness).

The second fixing roller 17b serving as a second fixing roller member for pressing the first fixing roller 17a with the fixing belt 27A interposed therebetween is provided outside a metal pipe (not numbered) having an outer diameter of about 15 to 20 mm (not shown). Surface), outer diameter 15-2
Approximately 5mm, rubber hardness 40Hs-80Hs (JI
(S, A rubber hardness) provided with a silicone rubber layer (no symbol), and is formed as a hard roller harder than the first fixing roller 17a.

A nip portion N having a convex upper side is formed between the first fixing roller 17a as a soft roller and the second fixing roller 17b as a hard roller with the fixing belt 27A interposed therebetween. As a result, the curvature of the nip portion N at the exit side of the recording paper P becomes large, and the recording paper P after the toner image is fixed is separated satisfactorily.

A metal guide plate 173 using an aluminum plate or a stainless steel plate is provided below the ceramic heater 171 and below the fixing belt 27A, and from about 5 to 15 mm from the opening on the entrance side of the recording paper P. As the nip portion N is approached, the intervals gradually become narrower, and the guide plate 173 receives heat from the fixing belt 27A heated by the heating element unit 170 in which the ceramic heater 171 is integrated.
Is heated to form a wide residual heat gap (remaining heat region) of the toner image with the fixing belt 27A.

The introduction plate 174 as an introduction member is formed of a plate-like metal member using an aluminum plate or a stainless steel plate. The recording paper P as a transfer material is introduced into the fixing belt 27A and brought into close contact therewith. To the nip N.
As the introduction member, a roller-shaped member may be provided on the guide plate 173 instead of the plate-shaped member, and the recording paper P may be introduced and adhered to the fixing belt 27A using the roller-shaped introduction member.

TS1 is mounted on the heat generating roller 17A and has a halogen lamp HL1 as an internal heat ray irradiation means.
A temperature sensor as a temperature detecting means using, for example, a contact-type thermistor for controlling the temperature of heating of the heat roller 17A by a heater or a xenon lamp (not shown);
TS2 is embedded in the heater holder 172 provided in the heating element unit 170 in the direction of movement of the fixing belt 27A so as to be embedded downstream of the ceramic heater 171 and is fixed. For example, a contact type thermistor for controlling the temperature of the heater 171 is a temperature sensor as a temperature detecting means using a thermistor. TS3 is a contact type for controlling the temperature attached to the lower second fixing roller 17b. Is a temperature sensor as a temperature detecting means using a thermistor, and TS4 is a temperature sensor mounted on the lower guide plate 173 as a temperature detecting means using a contact type thermistor for performing temperature control. .
As the temperature sensors TS1, TS2, TS3, and TS4, a non-contact type sensor can be used in addition to a contact type sensor.

The recording paper P brought into close contact with the fixing belt 27A by the introduction plate 174 receives the residual heat from the guide plate 173 and the preliminary heating from the fixing belt 27A in the wide contact area M, thereby warming the recording paper P. A relatively small width of 10 mm or less, preferably 5 mm or more, between the first fixing roller 17a and the second fixing roller 17b, which is formed with the fixing belt 27A interposed therebetween while the toner image on the recording paper P is melted. Into the narrow nip N,
At this time, the toner image on the recording paper P is fixed by heating the fixing belt 27A with heat and applying pressure by the first fixing roller 17a and the second fixing roller 17b. At this time, even if the recording paper P is separated from the transport belt 14a, the recording paper P is charged to a positive polarity, the fixing belt 27A is grounded (grounded), and the recording paper P is electrostatically transferred from the introduction plate 174 to the fixing belt 27A. Adhere.

Further, as shown in FIG.
In order to ensure that the electrostatic recording paper P closely adheres to the fixing belt 27A from the fixing belt 27A, the heating unit 170 provided on the back of the fixing belt 27A has a polarity opposite to that of the recording paper P (in this embodiment, toner and toner). A bias voltage E1 of the same polarity (minus polarity) is applied. Thereby, the fixing belt 2
The back surface of 7A is biased to the opposite polarity (minus polarity in the present embodiment) to the recording paper P, and the recording paper P is electrostatically attracted to the fixing belt 27A, so that the fixing belt 27
A is adhered to. Preheating from the fixing belt 27A in the wide contact area (preheating area) M and the guide plate 173
The recording paper P is warmed by the
The recording paper P enters the nip portion N while the toner image on the recording paper P is melted, and the toner image on the recording paper P is fixed. At this time, due to the large curvature at the exit side of the recording paper P in the nip portion N having a convex upper side, the recording paper P after the toner image is fixed is favorably separated.

The recording paper P can be brought into close contact with the fixing belt 27A by charging the surface of the fixing belt 27A. That is, as shown in FIG. 5, the heating roller 17A is grounded (grounded) and provided (contacted) with the fixing belt 27A, and has a polarity opposite to that of the recording paper P (minus polarity in the present embodiment). The recording paper P is brought into close contact with the fixing belt 27A using the charging brush TB1 to which the bias voltage E2 is applied. Recording paper P is fixing belt 27A
The recording paper P is electrostatically attracted to the fixing belt 27A and securely adheres to the fixing belt 27A, and receives the preliminary heating from the fixing belt 27A in the wide contact portion (preliminary heating area) M and the residual heat from the guide plate 173, so that the recording paper P The recording sheet P may enter the nip portion N while the toner image on the recording sheet P is being melted while being heated, and the toner image on the recording sheet P may be fixed. In this case, a corona discharger may be used instead of the charging brush TB1.

With the fixing device 700 described above,
The transfer material is electrostatically adhered to the belt member from the introduction member,
By the belt member heated by the heating of the heating roller member and the fixed heating element in the contact portion (preliminary heating area),
Since the transfer material and the toner image on the transfer material are previously melted (preheated) and fixed at the nip portion, the warm-up time is reduced, and the heat roller member and the belt member using the heat ray irradiating means are used. The contacting (fixing) fixed heating element speeds up the temperature rise of the belt member having poor thermal conductivity, and shortens the warm-up time. Also,
The heating of the heating roller member and the fixed heating element using the heat ray irradiating means eliminates the temperature change and uneven temperature of the belt member during continuous printing, and fixes the toner image on the transfer material at the nip. In this case, a good fixing property with little unevenness in fixing can be obtained, and a fixing device having high-speed capability can be obtained. Further, in the initial stage of heating, it is necessary to raise the temperature of the first fixing roller member and the second fixing roller member in the nip portion via the belt member, and the temperature of the belt member has not reached a fixing temperature. Therefore, as described above, the fixed heating element is set to be responsive, and assists in increasing the temperature of the belt member at the beginning of heating. Even during continuous printing, even if the temperature of the belt member fluctuates due to heating by the heating roller member, the temperature of the belt member can be adjusted with good response by responsive heating by the downstream fixed heating element. Further, the fixing temperature setting condition can be changed in accordance with the type of the transfer material by changing the temperature setting of the fixed heating element.

However, in order to speed up the temperature rise of the belt member having poor thermal conductivity and shorten the warm-up time, and to further prevent the temperature change and the temperature non-uniformity of the belt member during continuous printing, the following is required. It is preferable to set the following conditions.

First, the heat capacity (Q1 (J / deg)) of the heat-generating roller 17A as the heat-generating roller member is determined by using the ceramic heater 171 and the heater holder 17 as the heat-generating element.
Heating element unit 1 as a fixed heating element integrated with 2
Preferably, the heat capacity is set to be larger than the heat capacity (Q2 (J / deg)) of 70 (Q1> Q2). Thereby, the temperature rise of the fixing belt 27A having poor thermal conductivity is accelerated, the warm-up time is shortened, and the temperature change and the temperature non-uniformity of the fixing belt 27A during the continuous printing are eliminated, so that the fixing property is good. It is possible to realize a simple fixing device.

More specifically, when the heat capacity of the heat generating roller 17A is Q1 (J / deg) and the heat capacity of the heat generating unit 170 is Q2 (J / deg), the heat capacity Q1 of the heat generating roller 17A and the heat generating unit 170 It is preferable to set the ratio of the heat capacity to the heat capacity Q2, Q1 / Q2, as follows: Q1 / Q2 = 1.5-10. It is preferable that the heat capacity Q1 of the heat generating roller 17A is large and the heat capacity Q2 of the heat generating unit 170 is small. The heat capacity Q1 of the heating roller 17A is
This is because a sufficient heat capacity is required to sufficiently warm the fixing belt 27A, which has a remarkable decrease in temperature after fixing. The heating roller 17A plays the role of this heat reservoir, while the heating element unit 170 plays a role of temperature control utilizing good responsiveness. When the heat capacity Q2 of the heat generating unit 170 is too large and the ratio of the heat capacity Q1 of the heat generating roller 17A to the heat capacity Q2 of the heat generating unit 170, Q1 / Q2, is less than 1.5, the heat generating unit 170 by the ceramic heater 171 is activated. The heating time becomes longer and the responsiveness is reduced. The temperature control of the fixing belt 27A becomes insufficient. Further, the heat capacity Q2 of the heat generating unit 170 is too small, and the heat capacity Q1 of the heat generating roller 17A and the heat capacity Q
If the ratio Q2 / Q2 exceeds 10, the heat capacity of the heating element unit 170 becomes insufficient, and the fixing belt 27A cannot be sufficiently heated.

By setting the above conditions in the fixing device 700 described with reference to FIG. 3, the transfer material is brought into close contact with the belt member by the introduction member, and the heating roller member and the fixed heating element are brought into close contact with each other (preheating area). Since the transfer material and the toner image on the transfer material are previously melted (preliminarily heated) and fixed at the nip portion by the belt member heated by the heating in the above, the warm-up time is reduced, and Due to the heating by the heating roller member and the fixed heating element using the heat ray irradiating means, the temperature of the belt member having poor thermal conductivity is increased more quickly, and the warm-up time is further reduced. In addition, for a fixed heating element having a small heat capacity, a heat roller member having a large heat capacity on the upstream side of the nip portion serves as a heat reservoir, and the temperature of the belt member during continuous printing is stabilized, and A wide pre-heating area for pre-heating the toner image is provided at the bottom, and the fixed heating element having a small heat capacity allows the temperature of the belt member entering the nip portion to be responsively heated during continuous printing. Eliminates temperature changes and non-uniformity in temperature of the members, and at the time of fixing the toner image on the transfer material at the nip portion, obtains good fixability with less fixing unevenness and has high-speed capability. A fixing device becomes possible. In the initial stage of heating, the temperature of the first fixing roller member and the second fixing roller member in the nip portion via the belt member is not sufficiently increased,
The belt member has not reached a fixing temperature. Also in this case, as described above, the warming-up time can be substantially shortened by setting the fixed heating element to be responsive and assisting the belt member to raise the temperature at the initial stage of heating. In addition, during continuous printing, even if the temperature of the belt member fluctuates due to heating by the heating roller member, the temperature of the belt member at the nip can be adjusted to a constant temperature by responsive heating by the downstream fixed heating element. Further, the fixing temperature setting condition can be changed in accordance with the type of the transfer material by changing the temperature setting of the fixed heating element.

Second, the surface temperature T1 (° C.) of the heat generating roller 17A as the heat generating roller member is set as T1 <T2 when the surface temperature of the heat generating unit 170 as the fixed heat generating element is T2 (° C.). Is preferred. Downstream heating element unit 1
It is preferable that a high heat supply is performed at 70 so that the front surface of the fixing belt 27A has a high temperature distribution with respect to the back surface to have responsiveness, and T1 <T2. Normally, the surface temperature T1 of the heating roller 17A is maintained at about 150 to 160 ° C.
The surface temperature T2 of the heating element unit 170 is 180 to 200
Keep at about ° C.

Specifically, the ratio of the surface temperature T2 of the heating element unit 170 to the surface temperature T1 of the heating roller 17A,
It is preferable to set T2 / T1 as follows: T2 / T1 = 1.05 to 1.25. The surface temperature T2 of the heating element unit 170 is too low, and the ratio of the surface temperature T2 of the heating element unit 170 to the surface temperature T1 of the heating roller 17A, T
When 2 / T1 is less than 1.05, the heating element unit 1
No responsive control of heating of the fixing belt 27A by 70 is performed. The surface temperature T1 of the heating roller 17A is too low, and the ratio of the surface temperature T2 of the heating element unit 170 to the surface temperature T1 of the heating roller 17A, T2 / T1, is 1.2.
5, the fixing belt 27 by the heat-generating roller 17A
A is not sufficiently heated, and fixing defects such as uneven fixing occur.

By setting the above-described conditions in the fixing device 700 described with reference to FIG. 3, the transfer material is brought into close contact with the belt member by the introduction member, and the heating roller member and the fixed heating element are brought into close contact with each other (preheating area). Since the transfer material and the toner image on the transfer material are previously melted (preliminarily heated) and fixed at the nip portion by the belt member heated by the heating in the above, the warm-up time is reduced, and By heating with the heating roller member and the fixed heating element,
The temperature rise of the belt member having poor thermal conductivity is accelerated, and the warm-up time is further reduced. In addition, the heating roller member functions as a heat reservoir, which stabilizes the temperature of the belt member during continuous printing, and a wide preheating area (adhesion portion) for preheating the transfer material and the toner image. The temperature of the belt member entering the nip portion during continuous printing is quickly and responsively controlled by the fixed heating element having a substantially high heating rate (the belt member temperature control is performed responsively), and continuous printing is performed. The temperature change and unevenness of the temperature of the belt member at the time are more eliminated, and at the time of fixing the toner image on the transfer material at the nip portion, good fixing performance with less fixing unevenness is obtained, and high speed operation is possible. This makes it possible to provide a fixing device having an appropriate property. Further, even if the substantial heating rate of the fixed heating element is high, the temperature of the first fixing roller member and the second fixing roller member in the nip portion is not sufficiently increased via the belt member in the initial stage of heating, and the belt is not heated. The member has not reached the fixing temperature. In this case, as described above, the warming-up time is substantially reduced by setting the heating rate of the fixed heating element to be high and setting the temperature of the fixed heating element to be high to assist the heating of the belt member at the beginning of heating. Can be shortened. In addition, during continuous printing, even if the temperature of the belt member fluctuates due to heating by the heating roller member, the temperature of the belt member at the nip can be adjusted to a constant temperature by responsive heating by the downstream fixed heating element. Further, the fixing temperature setting condition can be changed in accordance with the type of the transfer material by changing the temperature setting of the fixed heating element.

Third, the maximum power (W1 (W)) of a halogen lamp HL1 or a xenon lamp (not shown) as a heat ray irradiating means provided inside a heat roller 17A as a heat roller member is used as a fixed heat element. (W1> W2) is preferably set to be larger than the maximum power (W2 (W)) of the ceramic heater 171 as a heating element provided in the heating element unit 170. The sum of the respective maximum powers that can be consumed for normal fixing, W1 + W2, is limited to about 0.8 to 1.2 kW due to use conditions as a printer function.

Halogen lamp HL as heat ray irradiation means
1 or xenon lamp (not shown)
(W)) is set to be larger than the maximum power (W2 (W)) of the ceramic heater 171 as the heating element (W1> W).
2) As a result, it is possible to supply sufficient power to the heat generating roller 17A having a role of a heat reservoir.

Specifically, when the maximum power of the halogen lamp HL1 or the xenon lamp (not shown) is W1 (W) and the maximum power of the ceramic heater 171 is W2 (W),
Maximum power W1 of halogen lamp HL1 or xenon lamp (not shown) and maximum power W2 of ceramic heater 171
It is preferable to set the ratio of W1 / W2 to W1 / W2 = 1.5 to 5. The maximum power W1 of the heating roller 17A is large, and the maximum power W of the ceramic heater 171 is large.
2 is preferably smaller. The maximum power W1 of the heating roller 17A is too small, and the ratio of the maximum power W1 of the heating roller 17A to the maximum power W2 of the ceramic heater 171 is expressed as W1 /
If W2 is less than 1.5, the heating of the heating roller 17A is insufficient, and the fixing belt 27A whose temperature has decreased after fixing is not sufficiently warmed. Also, the maximum power W2 of the ceramic heater 171 is too small, and the maximum power W1
Of the maximum power W2 of the ceramic heater 171 and W1
When / W2 exceeds 5, the ceramic heater 171 cannot sufficiently heat the fixing belt 27A with responsiveness.

As described above, the maximum power W1 (W) of the heating roller 17A is used as the fixed heater and the ceramic heater 1 is used.
71 is larger than the maximum power W2 (W) (W1> W2)
In addition, it is preferable to increase the temperature of the ceramic heater 171 quickly.

Therefore, the heat capacity of the heat generating roller 17A as the heat generating roller member is Q1 (J / deg), and the heat capacity of the heat generating unit 170 as a fixed heat generating element in which the ceramic heater 171 as the heat generating element and the heater holder 172 are integrated. Is defined as Q2 (J / deg), the ratio of the maximum power W2 of the ceramic heater 171 to the heat capacity Q2 of the heating element unit 170, W2 / Q2,
It is preferable to set the ratio W1 / Q1 between the maximum power W1 of the halogen lamp HL1 and the xenon lamp (not shown) inside the lamp A and the heat capacity Q1 of the heat generating roller 17A as (W2 / Q2)> (W1 / Q1). .

That is, (W2 / Q2) is the value of the heating element unit 17 in the heating element unit 170 itself (in the state of the heating element unit 170 alone separated from the fixing belt 27A).
0, and (W1 / Q1) is the substantial heating rate of the heating roller 17A itself (in the state of the heating roller 17A alone separated from the fixing belt 27A). The substantial heating rate of the body unit 170 (W2 /
The actual temperature rise rate (W1 / Q1) of the heat generating roller 17A with respect to Q2) is increased ((W2 / Q2)> (W1 / Q)
1)) It is preferable to set.

Specifically, it is preferable to set (W2 / Q2) / (W1 / Q1) = 2-7. Originally heating element unit 170
Of the heat generating roller 17A, the substantial temperature increasing speed (W1 / Q1) of the heat generating roller 17A is increased.
A slows down. The substantial heating rate (W2 / Q2) of the heating element unit 170 is slow (small), and the substantial heating rate (W2 / Q2) of the heating element unit 170 and the substantial heating of the heating roller 17A. The ratio to the speed (W1 / Q1), (W2 / Q2) / (W1 / Q1), is preferably 2 or more in view of the responsiveness of the substantial heating rate of the fixing belt 27A in the heating element unit 170. In addition, the substantial temperature increase rate (W1 / Q1) of the heat generating roller 17A is slow (small), and the substantial temperature increase rate (W2
/ Q2) and the substantial temperature increase rate (W1
/ Q1) and (W2 / Q2) / (W1 / Q1) is 7
When the temperature exceeds the setting, the temperature rise of the fixing belt 27A becomes faster, but the heat capacity Q2 of the heating element unit 170 with respect to the fixing belt 27A becomes too small, and the fixing belt 27A
Temperature becomes unstable. Further, even if the speed is excessively high, it is not effective because there is time for heat conduction from the back surface to the front surface of the fixing belt 27A, and a value of 7 or less is sufficient.

By setting the above conditions in the fixing device 700 described with reference to FIG. 3, the transfer material is brought into close contact with the belt member by the introduction member, and the heating roller member and the fixed heating element are brought into close contact with each other (preheating area). Since the transfer material and the toner image on the transfer material are previously melted (preliminarily heated) and fixed at the nip portion by the belt member heated by the heating in the above, the warm-up time is reduced, and By heating with the heating roller member and the fixed heating element,
The temperature rise of the belt member having poor thermal conductivity is accelerated, and the warm-up time is further reduced. In addition, for a fixed heating element with a small heat capacity and maximum power, a heat roller member that increases the heat capacity and maximum power on the upstream side of the nip serves as a heat reservoir, stabilizing the temperature of the belt member during continuous printing. Is maintained, and has a wide preheating area (adhesion part) for preheating the toner image, and the fixed heating element having a substantially high temperature rising speed allows the belt member to enter the nip part during continuous printing. The temperature is warmed up with responsiveness (the temperature control of the belt member is performed with good response)
The temperature change and non-uniformity of the temperature of the belt member during continuous printing are more eliminated, and at the time of fixing the toner image on the transfer material at the nip portion, good fixability with less fixing unevenness is obtained. A fixing device having high-speed capability can be provided.
In addition, even if the actual heating rate of the fixed heating element is high,
In the initial stage of the heating, the temperature of the first fixing roller member and the second fixing roller member in the nip portion via the belt member is not sufficiently increased, and the temperature of the belt member has not reached a fixing temperature. In this case, as described above, the warming-up time is substantially reduced by setting the heating rate of the fixed heating element to be high and setting the temperature of the fixed heating element to be high to assist the heating of the belt member at the beginning of heating. Can be shortened. In addition, during continuous printing, even if the temperature of the belt member fluctuates due to heating by the heating roller member, the temperature of the belt member at the nip can be adjusted to a constant temperature by responsive heating by the downstream fixed heating element. Further, the fixing temperature setting condition can be changed in accordance with the type of the transfer material by changing the temperature setting of the fixed heating element.

Fourth, the setting of the second substantial heating rate is specified, and a halogen lamp HL as a heat ray irradiating means provided inside the heating roller 17A is provided.
1 and a heating roller 17A alone as a heating roller member heated by a xenon lamp (not shown) (fixing belt 2
The heating rate (S1 (deg) at the fixing belt 27A contact surface position in the state of the heating roller 17A alone separated from the fixing roller 7A.
/ Sec)), the heating element unit 170 alone as the fixed heating element in which the ceramic heater 171 as the heating element and the heater holder 172 are integrated (the fixing belt 2).
In the state of the heating element unit 170 alone separated from 7A,
The temperature rising speed (S2 (d) at the fixing belt 27A contact surface position)
eg / sec)) is preferably set faster.

Specifically, the heating rate S is set to a time Δt (se
c) is determined by the temperature rise temperature ΔT (°) (S = ΔT / Δt), the rate of temperature rise of the heating roller 17A as a heating roller member is S1 (deg / sec), and the heating element unit 170 as a fixed heating element. The temperature rise rate of S2 (deg / s
When ec), it is preferable to set S2 / S1 = 2 to 7. Originally heating element unit 170
The temperature rise speed S2 of the heat roller 17A is made quicker while the temperature rise speed S1 of the heat roller 17A is reduced by the heat roller 17A having a large heat capacity Q1. Heating element unit 170
Of the heating element unit 170 and the heating rate S2 of the heating roller 17A are slow (small).
The ratio S2 / S1 to 1 is preferably 2 or more because the responsiveness of the heating rate of the fixing belt 27A in the heating element unit 170 is lost. Further, the temperature rise speed S1 of the heat generating roller 17A is slow (small) and the heat generating unit 170
When the ratio S2 / S1 of the temperature rising speed S2 of the heat roller 17A to the temperature rising speed S2 of the heating roller 17A exceeds 7, the fixing belt 27
Even if the temperature rise of A is fast, the heat capacity Q1 of the heat generating roller 17A with respect to the fixing belt 27A is too small, and the temperature of the fixing belt 27A becomes unstable. Further, even if the speed is excessively high, it is not effective because there is time for heat conduction from the back surface to the front surface of the fixing belt 27A, and a value of 7 or less is sufficient.

By setting the above conditions in the fixing device 700 described with reference to FIG. 3, the transfer material is brought into close contact with the belt member by the introduction member, and the heating roller member and the fixed heating element are brought into close contact with each other (preheating area). Since the transfer material and the toner image on the transfer material are previously melted (preliminarily heated) and fixed at the nip portion by the belt member heated by the heating in the above, the warm-up time is reduced, and By heating with the heating roller member and the fixed heating element,
The temperature rise of the belt member having poor thermal conductivity is accelerated, and the warm-up time is further reduced. Also, for a fixed heating element having a fast heating rate, the heating roller member on the upstream side of the nip portion having a slow heating rate serves as a heat reservoir.
The temperature of the belt member entering the nip portion during continuous printing is quickly and responsively increased by the fixed heating element having a high temperature rising rate while the temperature of the belt member is stabilized during continuous printing (the temperature of the belt member). The control is performed with good response), the temperature change and the temperature non-uniformity of the belt member at the time of continuous printing are more eliminated, and the fixation of the toner image on the transfer material at the nip portion is less likely to be uneven. This makes it possible to obtain a fixing device having high fixing performance and high-speed capability. Further, since the fixed heating element has a wide preheating area (adhesion portion) for preheating the toner image, heating of the belt member is easy, and the temperature control is performed by increasing the heating rate of the fixed heating element. Becomes easier. Further, even if the heating rate of the fixed heating element is high, the temperature of the first fixing roller member and the second fixing roller member in the nip portion is not sufficiently increased via the belt member at the initial stage of heating, and the belt member is not fixed. Not at a possible temperature. Also in this case, as described above, the warming-up time is increased by setting the heating rate of the fixed heating element to be high and by setting the temperature of the fixed heating element to be high to assist in increasing the temperature of the belt member at the beginning of heating. Can be substantially reduced. In addition, during continuous printing, even if the temperature of the belt member fluctuates due to heating by the heating roller member, the temperature of the belt member at the nip can be adjusted to a constant temperature by responsive heating by the downstream fixed heating element. Further, the fixing temperature setting condition can be changed in accordance with the type of the transfer material by changing the temperature setting of the fixed heating element.

As shown in FIG. 6, a heater holder 172A for holding a ceramic heater 171 as a heating element.
May be provided with a heat equalizing roller TR4 as a heat equalizing member to form a heating element unit 170A as a fixed heating element. As the heat equalizing roller TR4, for example, a metal roller member having good thermal conductivity, such as an aluminum material or a stainless steel material, is used. Temperature direction) is uniformed. Heat uniformizing roller TR
As 4, it is preferable to use a heat pipe that has both heat storage and heat radiation.

As shown in FIG. 7, a bias voltage E3 having the same polarity (positive polarity in this embodiment) as that of the recording paper P is applied to an introduction plate 174 as an introduction member on the transfer material side, and a heating element unit 170 is provided. Is grounded to ground the fixing belt 27A. As a result, the recording paper P is repelled by charges of the same polarity (positive polarity in this embodiment) as the recording paper P generated on the introduction plate 174, and the recording paper P is electrostatically attracted to the fixing belt 27A. Therefore, the recording paper P is securely brought into close contact with the fixing belt 27A. The recording paper P is heated by the preliminary heating from the fixing belt 27A in the wide contact portion (preliminary heating area) M and the residual heat from the guide plate 173, and the recording paper P is melted while the toner image on the recording paper P is melted. P is the nip N
(See FIG. 3, not shown in FIG. 7), and the toner image on the recording paper P is fixed. At this time, due to the large curvature of the nip portion N (see FIG. 3 and not shown in FIG. 7) having a convex upper side on the exit side of the recording paper P, the recording paper P after the toner image is fixed.
Separation is performed favorably.

As shown in FIG. 8, a charging roller 175 is provided at the tip of an introduction plate 174 as an introduction member on the transfer material side, and the charging roller 175 has the same polarity as the recording paper P (positive polarity in this embodiment). The fixing belt 27A is grounded by applying the bias voltage E4) and grounding the heating element unit 170. As a result, the recording paper P is repelled by an electric field having the same polarity (positive polarity in the present embodiment) as the recording paper P of the charging roller 175, and the recording paper P is electrostatically attracted to the fixing belt 27A, thereby ensuring the reliability. Is brought into close contact with the fixing belt 27A. The recording paper P is heated by the preliminary heating from the fixing belt 27A in the wide contact portion (preliminary heating area) M and the residual heat from the guide plate 173, and the recording paper P is melted while the toner image on the recording paper P is melted. P enters the nip portion N (see FIG. 3, not shown in FIG. 8), and the toner image on the recording paper P is fixed. At this time, due to the large curvature at the exit side of the recording paper P of the nip portion N (see FIG. 3, not shown in FIG. 8) having a convex upper side, the separation of the recording paper P after fixing the toner image is excellent. Done.

In the above, without providing the introduction plate 174,
The same polarity as the recording paper P (plus polarity in this embodiment)
, The recording paper P may be electrostatically brought into close contact with the fixing belt 27A by providing only the charging roller 175 to which the bias voltage E4 is applied.

As described above, the temperature rise of the belt member having poor thermal conductivity is accelerated, the warm-up time is shortened,
In addition, the temperature change and the temperature non-uniformity of the belt member during continuous printing are eliminated, and good fixability with less fixing unevenness is obtained at the time of fixing the toner image on the transfer material at the nip portion. Thus, a fixing device having high-speed capability, a large heating effect, and high thermal efficiency can be provided.

As shown in FIG. 9, a metal roller 177 made of, for example, aluminum or stainless steel is provided in place of the heat generating roller 17A described in FIG.
A halogen lamp HL2 or a xenon lamp (not shown) as a heat ray irradiating means is provided inside the first fixing roller 17a as a fixing roller member, and the inside of the fixing belt 27A is replaced with the heating element unit 170 described in FIG. To
The fixing device 710 may be formed by providing a belt guide plate 176 that contacts the fixing belt 27A and guides the rotation of the fixing belt 27A, for example, a belt guide member using an aluminum or stainless steel plate. Good.
The wide contact area (preheating area) M is the belt guide plate 1
The fixing belt 27 is provided on the fixing belt 27A on the back surface of the fixing belt 76. In the case of this example, a temperature sensor TS5 as a temperature detecting means for performing temperature control is provided on the first fixing roller 17a, and the temperature of the heating of the first fixing roller 17a by the halogen lamp HL2 or a xenon lamp (not shown). Perform control.

In order to cope with all transfer material sizes, the belt guide plate 176 and the metal roller 177 are made of a metal member having a small heat capacity to increase the heat diffusion in the lateral direction (the direction orthogonal to the transfer material feed direction).

No heat beam irradiating means (heating means) is provided on the upstream side, and is preheated by a fixing belt 27A which is heated by a halogen lamp HL2 or a xenon lamp (not shown) provided inside the first fixing roller 17a, and recording is performed. Paper P
Is heated and the toner image on the recording paper P is melted while the fixing belt 27A is sandwiched between the first fixing roller 17a as a soft roller and the second fixing roller 17b as a hard roller. The recording paper P enters a relatively narrow narrow nip N having a width of 10 mm or less, preferably 5 mm or more, and the upper side of which is convex. In the nip N, the halogen lamp H inside the first fixing roller 17a is formed.
The recording paper P is heated by heating the fixing belt 27A heated by the L2 and the xenon lamp (not shown) and applying pressure by the first fixing roller 17a and the second fixing roller 17b.
The upper toner image is fixed. At this time, due to the large curvature at the exit side of the recording paper P in the nip portion N having a convex upper side,
The separation of the recording paper P after fixing the toner image is favorably performed.

As described above, in the same manner as described above, a bias voltage (not shown) having a polarity opposite to that of the recording paper P (not shown in the present embodiment) is applied to the fixing belt 27A and the belt guide plate 176, or a ground (not shown). Grounding) and the fixing belt 27 of the recording paper P by electrostatic attraction force.
A may be set to have good contact with the recording paper P, and an introduction plate 174 as an introduction member and the above-described charging roller (not shown) are provided, and the recording sheet P is attached to the introduction plate 174 and the charging roller (not shown). By applying a bias voltage (not shown) of the same polarity (plus polarity in the present embodiment) and grounding the belt guide plate 176, the fixing belt 27
A may be grounded (grounded) to improve the adhesion of the recording paper P to the fixing belt 27A by electrostatic repulsion.

According to the above, the temperature rise of the belt member having poor thermal conductivity is accelerated, the warm-up time is shortened, and the temperature change and the temperature non-uniformity of the belt member during continuous printing are eliminated, and the nip portion is reduced. In the case of fixing a toner image on a transfer material by using the method described above, good fixing performance with less fixing unevenness can be obtained, and a fixing device having high-speed response, a large heating effect, and high thermal efficiency can be realized. .

[0085]

According to the present invention, the temperature rise of the belt member having poor thermal conductivity is accelerated, the warm-up time is shortened, and the temperature change and the temperature non-uniformity of the belt member during continuous printing are eliminated. A fixing device that has good fixing performance with less fixing unevenness when fixing a toner image on a transfer material in a nip portion, has high-speed capability, has a large heating effect, and has high thermal efficiency. Becomes possible.

[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 an explanatory diagram of a first example of a structure of a fixing device and application of a bias voltage on a belt member side.

FIG. 4 is an explanatory diagram of a second example of application of a bias voltage on the belt member side.

FIG. 5 is an explanatory diagram of a third example of application of a bias voltage on the belt member side.

6 is a diagram showing a heat equalizing member provided on a fixed heating element of the fixing device of FIG.

FIG. 7 is a diagram illustrating a first example of application of a bias voltage on the transfer material side.

FIG. 8 is a diagram illustrating a second example of application of a bias voltage on the transfer material side.

FIG. 9 is a diagram illustrating another example of the structure of the fixing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 17A heating roller 17a first fixing roller 17b second fixing roller 27A fixing belt 170, 170A heating element unit 171 ceramic heater 172, 172A heater holder 173 guide plate 174 introduction plate 176 Belt guide plate 177 Metal roller 700,710 Fixing device HL1, HL2 Halogen lamp M Adhesive part P Recording paper

Claims (6)

[Claims] A first fixing roller member that stretches the belt member on one side; a heating roller member that stretches the other side of the belt member together with the first fixing roller member; And a second fixing roller member provided to face the first fixing roller member and forming a nip between the first fixing roller member and the first fixing roller member. A planar fixed heating element that contacts the belt member from the inside of the belt member and heats the belt member is provided between the roller member and the roller member. A fixing device that performs heating and fixes the toner image on the transfer material at the nip portion. 2. The image forming apparatus according to claim 1, wherein the transfer material is provided on an upstream side of a contact portion where the transfer material is in close contact with the belt member with respect to a rotation direction of the belt member.
The fixing device according to claim 1, wherein the fixed heating element is provided. 3. The fixing device according to claim 1, wherein the fixed heating element is provided on a back surface of a contact portion where the transfer material is in close contact with the belt member. 4. The fixing device according to claim 1, further comprising an introduction member that introduces the transfer material into the belt member. 5. The fixing device according to claim 1, wherein a bias voltage for bringing the transfer material into close contact with the belt member is provided on the belt member side. 6. The fixing device according to claim 1, wherein a bias voltage for bringing the transfer material into close contact with the belt member is provided on the transfer material side.