JP2002062752A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus, capable of improving image quality without making the device large and complicated. SOLUTION: Since a heating roller 14 is constituted of conductive base material covered with a heat resistant elastic body, nip width for excellently heating and press-contacting transfer paper 3 in the case of fixing is secured. An external heating roller 16 equipped with a metallic cylindrical core bar 16a and a halogen lamp 16c for heating the mandrel 16a and constituted, by coating the surface layer of the core bar 16a with conductive PFA resin is made to abut on the surface of the roller 14, whereby the surface temperature of the roller 14 is precisely controlled, and the situation that the surface of the roller 16 is electrified to cause disturbances in a toner image is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electronic copying machine and a printer, and more particularly to an image forming apparatus having excellent fixing properties.

[0002]

2. Description of the Related Art In a fixing section of an image forming apparatus such as an electronic copying machine, a heater as a heating source is built in one roller called a heating roller, and a predetermined contact width (hereinafter, referred to as a nip width) with the heater is provided. A pressure roller or a belt is provided for pressing and holding (some types also have a heating source on the pressure roller or the belt side). The two rollers are pressed and rotated, and the toner image is transferred between the two rollers. The toner image is heat-fixed by passing the material through.
There is an optimum temperature for the thermal fixing of the toner image, and the power supply to the heater is automatically controlled so that the surface temperature of the heating roller maintains an allowable temperature range including the optimum temperature (for example, 150 ° C. to 200 ° C.). This automatic control is performed by providing a thermistor or an infrared sensor as a temperature-sensitive element in sliding or non-contact with the heating roller, and sending a detection output of the thermistor or the like to the temperature control unit to adjust power supply to the heater. Will be Known heaters include a halogen lamp fixed in a space inside a roller to control the power supply, and a heater in which an insulating thin film is provided on the inner surface of the roller and a resistance heating element is further provided inside the roller to control the power supply.

By the way, the heat generated from the heater is:
The toner image is thermally fixed from the inside of the heating roller to the peripheral surface, and therefore, in a monochrome image forming apparatus, a metal such as aluminum or stainless steel having high thermal conductivity is used for the heating roller in a monochrome image forming apparatus. It is common to use a layer having a surface layer provided with a fluororesin layer having a releasability to the toner on the order of several tens of μm. in this case,
Since it is necessary to have a predetermined nip width, the pressure roller is configured with an elastic layer. However, when such a heating roller is brought into contact with an unfixed image surface,
It has been pointed out that the surface of the heating roller cannot follow the unevenness of the transfer paper or the toner layer, and in the case of a color image or the like, uneven melting of each toner occurs, thereby deteriorating the image quality.

On the other hand, in a conventional fixing device, an elastic layer is provided on a surface of a roller (hereinafter, referred to as a heating roller) on a side which comes into contact with a surface of a transfer material which carries an unfixed toner image. In some cases, the image quality is improved by the configuration. In particular, in a color image forming apparatus, it is usual that the heating roller has such a configuration, and a heat-resistant elastic layer such as silicone rubber is coated around a metal cylindrical core around 0.5 to 5 mm, Further, in order to further enhance the durability of the surface, there is a case where a fluororesin having high heat resistance such as PFA or PTFE is provided in a thickness of about 15 to 70 μm by coating or tube coating.

The nip shape when two rollers are pressed against each other is, for example, when the hardness (hardness under the same thickness condition) of the elastic layer of the heating roller and the pressure roller and the outer diameter of the roller are the same, As the thickness of the elastic layer of the heating roller increases, the nip shape seen from the side becomes more convex (the state where the opposing roller cuts into the surface of the heating roller),
As a result, the self-stripping effect that the transfer material is easily peeled off from the surface of the heating roller is easily exerted, and the nip width (length in a direction perpendicular to the width of the contact surface with the transfer material) is reduced by thickening the elastic layer of the heating roller. Since the larger the gain, the more the fixing performance can be secured even if a roller having a relatively small diameter is used, there is an advantage that the entire apparatus can be made compact.

[0006]

However, since the thermal conductivity of silicone rubber or the like is generally lower than that of metal or the like, the thicker the elastic layer of the heating roller, the more the heat conductivity.
Heat transfer from the internal heater to the roller surface deteriorates, lowering the surface temperature during paper passing, increasing the WUT (warm-up time), and keeping the surface at a predetermined temperature during paper passing. The temperature rise of the elastic body becomes large (the temperature of the elastic body at the core metal bonding portion is the highest), which may cause thermal deterioration of the elastic body and separation of the elastic body from the core metal.

In order to improve this phenomenon by supplying heat not only from the inside of the roller but also from the roller surface, JP-A-8-314323, JP-A-10-10919, JP-A-10-97150, JP-A-11-721, and Kaihei 11-
24465, JP-A-11-38802, and the like have proposed a device in which an external heating roller having no elastic layer is provided on the surface of the heating roller. In these prior arts, as an external heating roller, a roller having an alumite-treated aluminum cylindrical core, a stainless steel roller, a mirror-finished iron roller that does not damage the heating roller surface, and a stainless roller having a lower release than the heating roller (The surface roughness should be set to Rz0.0 so as not to damage the heating roller.
7 mm or less, and contact the cleaning web with the surface)
It describes a highly heat-conductive aluminum, iron, or stainless steel core bar coated with a highly releasable rubber / resin. Further, with respect to a pressure roller having an elastic layer, a roller in which an external heating roller is contacted so as to stably maintain the surface temperature has been proposed in order to secure fixing performance.

However, in the technology that does not ensure the releasability on the surface of the external heating roller, toner and paper powder adhere to and accumulate on the external heating roller, which causes defects such as image stains and uneven heating. There is a problem. In the above prior art, the upstream side of the surface of the heating roller (and / or the pressure roller) where the external heating roller is in contact,
Although there is an example in which the cleaning web is brought into contact, it is difficult to completely remove the toner on the surface of the heating roller (and / or the pressure roller) with the cleaning web, and the time until the generation of dirt is prolonged. However, eventually, dirt accumulates on the surface of the external heating roller. It is also difficult to completely remove the toner fused to the metal surface with the web.

On the other hand, aluminum, iron,
No specific material is described for the case where a high release rubber / resin is coated on a stainless steel core, and even if the release property of the toner can be ensured, the surface of the heating roller (and / or the pressure roller) can be secured. May be frictionally charged, thereby causing a problem such as causing disturbance of the toner image.

Further, the heater in the external heating roller is constituted by a plurality of heaters having so-called different heat distributions capable of heating each of a plurality of areas to prevent a rise in the temperature at the roller end portion when copying a narrow width transfer material. However, there is a problem that the roller becomes large and complicated in order to correspond to all transfer material sizes.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of improving image quality without increasing the size and complexity of the apparatus.

[0012]

In order to achieve the above object,
An image forming apparatus according to a first aspect of the present invention is an image forming apparatus including a pair of pressed rollers or a fixing device including a pressed roller and a belt, wherein at least one of the rollers has a high thermal conductivity and rigidity. It is configured by covering a heat-resistant elastic body on a cylindrical base material, and further includes a metal cylindrical core, and a heating source for heating the metal cylindrical core, and the metal cylindrical core An external heating roller whose surface layer is covered with a conductive fluororesin is brought into contact with the surface of the heat-resistant elastic body.

According to a second aspect of the present invention, there is provided an image forming apparatus including a pair of pressed rollers or a fixing device including a pressed roller and a belt, wherein at least one of the rollers has high thermal conductivity and rigidity. A cylindrical base material having a heat-resistant elastic body coated thereon, and further comprising a metal cylindrical core, and a heating source for heating the metal cylindrical core, and An external heating roller whose surface layer is covered with an insulating fluororesin having no conductive filler or the like is brought into contact with the surface of the heat-resistant elastic body. A static eliminator is provided on the downstream side in the rotation direction of one roller.

According to a third aspect of the present invention, there is provided an image forming apparatus including a pair of pressed rollers or a fixing device including a pressed roller and a belt, wherein at least one of the rollers has high thermal conductivity. It is configured by coating a heat-resistant elastic body on a rigid cylindrical base material, and further comprises a conductive fluororesin layer on the surface, which is in contact with the surface of the heat-resistant elastic body, and at least a metal core. An auxiliary roller partially constituted by a heat pipe is provided, a metal cylindrical core is provided, and a heating source for heating the metal cylindrical core is provided, and the surface layer of the metal cylindrical core is formed of a thin heat-resistant elastic body. Characterized in that the external heating roller covered with the above is brought into contact with the surface of the auxiliary roller.

[0015]

According to a first aspect of the present invention, there is provided an image forming apparatus including a pair of pressed rollers or a fixing device including a pressed roller and a belt, wherein at least one of the rollers is a heat-resistant elastic body. Since it is composed of a cylindrical substrate having high thermal conductivity and rigidity coated with a nip, it is possible to increase a nip width for satisfactorily thermocompression bonding a transfer material when performing fixing. Further, an external heating roller comprising a metal cylindrical core and a heating source for heating the metal cylindrical core, and an outer heating roller having a surface layer of the metal cylindrical core coated with a conductive fluororesin, By contacting the surface of the external heating roller, the problem of the internal heating method can be improved, and since the fluororesin is coated on the external heating roller surface, adhesion of toner and the like can be suppressed, and the fluororesin of the external heating roller surface layer can be suppressed. Is electrically conductive, the charging of the surface of the heating roller can be suppressed. Grounding the surface layer of the external heating roller, or grounding the core with a conductive metal or the like, further stabilizes the charging of the surface of the heating roller. In addition, as the conductive fluororesin, PFA, PTFE mixed with a conductive filler, or the like can be used, but is not limited thereto.

Further, PFA is further added to the surface of the heat-resistant elastic body.
By providing a high release insulating resin layer such as, the toner heated in the nip portion adheres to the surface of the heating roller,
The so-called offset phenomenon can be suppressed, and the durability and abrasion resistance of the surface releasability can be improved. In this case, the offset phenomenon can be suppressed even when a release agent such as silicone oil is not applied to the heating roller or when a very small amount is applied.
It is better not to mix a conductive filler or the like with respect to the releasability of the fluororesin, but in this case, there is a disadvantage that triboelectric charging is liable to occur. However, since the surface of the external heating roller is covered with the conductive fluororesin, in the present invention, frictional charging can be suppressed after contact with the external heating roller and before the nip portion.

In such a configuration, when the toner slightly offset to the surface of the heating roller at the nip has a negative polarity, the toner slightly offset to the surface of the heating roller at the nip is charged to the minus side with respect to the external heating roller. Electrostatic transfer from the heating roller to the external heating roller is easy. Therefore, the surface of the external heating roller is brought into contact with a cleaning member for the external heating roller, which is made of an elastic material having a lower toner releasability than the conductive fluororesin, so that the surface of the external heating roller is reduced. The cleaning can be performed efficiently, and the accumulation of dirt on the external heating roller and the problems resulting therefrom can be suppressed for a long period of time.

Further, it is preferable that the cleaning member has a roller shape because the rotation resistance is small.

Further, the surface roughness of the external heating roller is made rougher than the surface roughness of the heat-resistant elastic body or the highly releasable insulating resin layer, and the surface roughness of the cleaning member for the external heating roller is made rougher. It is preferable because the cleaning effect is enhanced.

According to a second aspect of the present invention, there is provided an image forming apparatus comprising a pair of pressed rollers or a fixing device comprising a pressed roller and a belt, wherein at least one of the rollers is made of a heat-resistant elastic material. A cylindrical base material having high thermal conductivity and rigidity coated with a metal cylindrical core, further comprising a heating source for heating the metal cylindrical core, and the metal cylindrical core An external heating roller in which the surface layer of gold is coated with an insulating fluororesin having no conductive filler or the like is brought into contact with the surface of the heat-resistant elastic body,
Since the static elimination means is provided on the downstream side in the rotation direction of the at least one roller from the contact position with the external heating roller, when the toner that is extremely small offset to the surface of the heating roller at the nip portion has a negative polarity, the offset toner is The electrostatic transfer from the heating roller to the external heating roller is improved, and the problem of accumulation and derivation of dirt on the external heating roller for a long period of time can be suppressed without bringing the cleaning roller into contact with the external roller. Further, in this case, the surface of the heating roller is easily frictionally charged by contact with the external heating roller, but the static elimination means is provided on the downstream side in the rotation direction of the at least one roller from the contact position with the external heating roller. In addition to the effects of the invention described above, since the charging of the roller contacting the external heating roller can be suppressed, the disturbance of the toner image can be suppressed.

Further, PFA is further added to the surface of the heat-resistant elastic body.
By providing a high release insulating resin layer such as, the toner heated in the nip portion adheres to the surface of the heating roller,
The so-called offset phenomenon can be suppressed, and the durability and abrasion resistance of the surface releasability can be improved. In this case, the offset phenomenon can be suppressed even when a release agent such as silicone oil is not applied to the heating roller or when a very small amount is applied.
It is better not to mix a conductive filler or the like with respect to the releasability of the fluororesin, but in this case, there is a disadvantage that triboelectric charging is liable to occur. However, since the static eliminator is set to face the surface of the external heating roller, the present invention can suppress the triboelectric charging.

Further, it is desirable that the static elimination means is a non-contact type, for example, a non-contact ground static elimination brush without contamination by toner or the like.

According to a third aspect of the present invention, there is provided an image forming apparatus including a pair of pressed rollers or a fixing device including a pressed roller and a belt, wherein at least one of the rollers has a high thermal conductivity. It is constituted by covering a heat-resistant elastic body on a cylindrical base material having properties and rigidity, and further abuts on the surface of the heat-resistant elastic body, comprising a conductive fluororesin layer on the surface and a metal cored bar. An auxiliary roller at least partially constituted by a heat pipe is provided, and a metal cylindrical core is provided, and a heating source for heating the metal cylindrical core is provided, and a surface layer of the metal cylindrical core is thinly heat-resistant. Since the external heating roller covered with the elastic body is brought into contact with the surface of the auxiliary roller, in addition to the effects of the above-described invention, even if the heating source uniformly heats the roller, Peripheral local Since heating is possible, even when the transfer material having a small width is repeatedly heated, the temperature rise in the roller end region can be suppressed, and therefore, it is possible to form an image on a transfer material having a different size. Even in such a case, quick processing can be performed while maintaining the image quality. Since the auxiliary roller composed of a heat pipe is composed of a roller with a hard surface, the external heating roller has a thin elastic layer on the surface to stabilize the contact with the external heating roller. Efficiency will be worse).

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of the image forming apparatus according to the first embodiment. In FIG. 1, an image forming apparatus 1 feeds transfer paper 3, which is a transfer material stored in a paper feed cassette 2, one by one by a paper feed roller 4 and a double running prevention unit 5. Thus, the transfer paper 3 is guided by a guide plate (not shown) and inserted into the transport roller 6. Further, the transfer paper 3 sent out from the transport roller 6 is inserted into the registration roller 7 and sent out to the transfer area of the transfer processing unit. Thereafter, the transfer paper 3 passes between the photosensitive drum 8, the transfer charger 9, and the separation charger 10 and carries the toner image.
Sent to. The transfer paper 3 heated and pressurized in the fixing unit 13 fixes the toner image and is sent to a discharge tray (not shown).

FIG. 2 is an enlarged view showing the periphery of the roller in the fixing unit 13. In FIG. 2, the fixing unit 13 includes
Around the aluminum core 14a having high thermal conductivity and rigidity, a silicone rubber 14b as a heat-resistant elastic body is coated,
Further, the heat roller 14 having its periphery coated in layers with an insulating PFA resin 14c, which is an insulating resin having high toner release properties (for example, insulating fluororesin), and an aluminum core metal 15a having high thermal conductivity and rigidity are heat-resistant. Pressure roller 15 coated with silicone rubber 15b as an elastic body (a fluorine resin layer may be provided around silicone rubber 15b)
And an external heating roller 16 in which a conductive PFA resin is coated in a layer around an aluminum core 16a which is a metal cylindrical core, and a toner releasing property around the aluminum core 17a from the conductive fluororesin. It has a cleaning roller 17 which is a cleaning member coated with silicone rubber 17b which is a bad elastic body.

The heating roller 14 has a halogen lamp 14d as a heating source inside, the pressing roller 15 has a halogen lamp 15c as a heating source inside, and the external heating roller 16 has a heating source inside. As a halogen lamp 16c. Each halogen lamp 14d, 15
c and 16c are connected to the temperature control unit 18. The main body control unit 19 controls the temperature control unit 18 in accordance with the temperature detected by a sensor (not shown) provided on the surface of each roller, and controls the halogen lamps 14d, 15c, 1c.
6c is controlled so as to maintain the roller surface temperature in a predetermined temperature range. By a spring (not shown)
The pressure roller 15 is urged against the heating roller 14, and both rollers are maintained in a pressed state.

The operation of the fixing unit 13 will be described. The transfer paper 3 on which the toner image is formed is passed between the heating roller 14 and the pressure roller 15 while being heated and pressed, and the toner image is thermally fixed during that time. . In the present embodiment,
Since the external heating roller 16 that contacts the heating roller 14 is provided, the surface temperature of the heating roller 14 can be controlled more efficiently.

The toner carried on the transfer paper 3 is heated and pressed into a semi-fluid state, but the surface of the heating roller 14 is covered with an insulating PFA resin 14c.
The semi-fluidized toner can be prevented from adhering to such a surface.

If the toner powder is negatively charged, the toner powder attached to the heating roller 14 becomes negatively charged (insulating P).
The FA resin is easily negatively charged due to frictional charging or the like). The electric field at the contact portion between the heating roller 14 and the external heating roller coated with a conductive fluororesin that is not so charged is electrostatically attracted to the external heating roller 16. The surface may be contaminated. Therefore, in the present embodiment, the cleaning roller 17 is provided so that the external heating roller 16
Is cleaned to minimize image disturbance.

In particular, the periphery of the cleaning roller 17 is
Since the conductive PFA resin coated on the external heating roller 16 is covered with the silicone rubber 17b having poor toner releasability, the cleaning roller 17 is brought into contact with the external heating roller 16 so that the toner is removed from the external heating roller. 1
6 can easily move from the surface of the cleaning roller 17 to the surface of the cleaning roller 17, and cleaning can be performed more efficiently.

Further, the surface roughness of the external heating roller 16 is made coarser than the surface roughness of the high toner release insulating PFA resin 14c coated on the heating roller 14, and the surface roughness of the cleaning roller 17 for the external heating roller 16 is further increased. By making the surface roughness coarser, the toner easily moves from the heating roller 14 to the external heating roller 16 and easily moves from the external heating roller 16 to the cleaning roller 17, so that the cleaning effect is enhanced, which is preferable.

FIG. 3 is a view similar to FIG. 2 showing a second embodiment of the present invention. The second embodiment differs from the first embodiment only in the material of the external heating roller and the point that a ground conductive brush is provided instead of the cleaning roller. Will not be described.

More specifically, the difference is that the external heating roller 16 has the surface of a cored bar 16a coated with an insulating fluororesin having no conductive filler or the like. Further, in FIG. 3, a grounding conductive brush 20 as a static eliminator is provided on the downstream side in the rotation direction of the heating roller 14 from the contact position between the heating roller 14 and the external heating roller 16. According to the present embodiment, in addition to the effect of the above-described embodiment (excluding the effect of the cleaning roller), the charging of the external heating roller 16 can be suppressed by the grounding conductive brush 20, and therefore, the heating roller 14 in contact with the external heating roller 16 can be suppressed. Since the charging can be suppressed, the disturbance of the toner image can be further suppressed.

The surface of the heat-resistant elastic body of the heating roller 14 has PF
A, by providing a highly releasable insulating resin layer as shown in FIG.
The so-called offset phenomenon, which adheres to the surface of No. 4, can be suppressed, and the durability and abrasion resistance of the releasability of the surface can be improved.
In this case, the offset phenomenon can be suppressed even when a release agent such as silicone oil is not applied to the heating roller 14 or when a very small amount is applied. It is better not to mix a conductive filler or the like with respect to the releasability of the fluororesin, but in this case, there is a disadvantage that triboelectric charging is liable to occur. Therefore, in the present embodiment, the grounding conductive brush 20 is set as a static eliminator in opposition to the surface of the external heating roller 16, thereby effectively suppressing triboelectric charging.

FIG. 4 is a view similar to FIG. 2 showing a third embodiment of the present invention. The third embodiment is different from the first embodiment mainly in that an auxiliary roller is provided between a heating roller and an external heating roller. Therefore, the common configuration will be described. Omitted. The cleaning roller may be brought into contact with the external heating roller.

The difference will be described more specifically.
In the above, between the heating roller 14 and the external heating roller 16, the auxiliary roller 2
1 is arranged. The auxiliary roller 21 has a heat pipe 21b inserted into an aluminum cylindrical core 21a, and a PFA resin 21c which is a conductive fluororesin on the outer surface.
Are coated in layers. A medium such as water is sealed in the heat pipe 21b. The auxiliary roller may use the heat pipe itself without providing a cored bar.

According to the present embodiment, since the auxiliary roller 21 is disposed between the heating roller 14 and the external heating roller 16, even if the halogen lamp 1 of the heating roller 14 is used.
4d and the halogen lamp 16c of the external heating roller 16,
Even if there is a heat generation distribution, the medium in the heat pipe 21b conducts heat and functions to uniformly adjust the surface temperature of the heating roller 14 in the width direction and the circumferential direction. This makes it possible to suppress uneven heating of the transfer paper 3 during fixing and form a high-quality image. In the case where the transfer paper 3 of a large size is fixed after the transfer paper 3 of a small size is fixed, the end of the heating roller 14 through which the transfer paper 3 does not pass after the transfer paper 3 of a small size is fixed. In some cases, the medium in the heat pipe 21b of the auxiliary roller 21 conducts heat, and the surface temperature of the heating roller 14 is quickly and uniformly adjusted in the width direction. I do. Thereby, large transfer paper 3
This makes it possible to form a high-quality image by suppressing uneven heating during fixing. Further, since the auxiliary roller 21 including the heat pipe 21b is a roller having a hard surface, the contact with the external heating roller 16 is stabilized. (The heat transfer efficiency from the lamp 16c is deteriorated). The PFA resin 21b coated around the auxiliary roller 21 is desirably thin enough to ensure contact between the auxiliary roller 21 and the external heating roller 16 and not to hinder heat conduction.

FIG. 5 is a schematic configuration diagram showing a color image forming apparatus according to the fourth embodiment. Reference numeral 110 denotes a drum-shaped image forming body, that is, a photosensitive drum. A transparent conductive layer and an organic photosensitive layer (OP) are formed around a cylindrical base formed of a transparent member such as optical glass or transparent acrylic resin.
C) is applied.

The photosensitive drum 110 has a flange (not shown) at one end supported by a guide pin (not shown) of the cartridge 130, and a flange (not shown) at the other end of the photosensitive drum. Power is transmitted via a plurality of guide rollers (not shown) provided on a substrate (not shown), and the transparent conductive layer is rotated clockwise by the power while the transparent conductive layer is grounded.

Numeral 111 denotes a scorotron charger for charging the above-mentioned organic photoreceptor layer of the photoreceptor drum 110 by a grid maintained at a predetermined potential and corona discharge by a discharge wire. Give a similar potential.

Reference numeral 112 denotes an exposure optical system composed of LEDs and selfoc lenses arranged in the axial direction of the photosensitive drum 110. Image signals of respective colors read by a separate image reading device are sequentially taken out from a memory. Each of the exposure optical systems 112 is input as an electric signal.

Each of the exposure optical systems 112 is attached to a column-shaped support member (not shown) which is fixed with a guide pin (not shown) as a guide to a substrate (not shown) of the apparatus main body. It is housed inside the substrate of the drum 110.

113Y to 113K are yellow (Y), magenta (M), cyan (C) and K (black)
And a developing sleeve 130 that rotates in the same direction while maintaining a predetermined gap with respect to the peripheral surface of the photosensitive drum 110.

Each of the above-mentioned developing devices is provided with the above-described charger 111.
The electrostatic latent image on the photoconductor drum 110 formed by the charging of the photosensitive drum 110 and the image exposure by the exposure optical system 112 is reversely developed in a non-contact state by applying a developing bias voltage.

The operation of the second embodiment will be described. An original image is read by an image reading device separate from the present device, and an image read by an image sensor or an image edited by a computer is converted into Y, M, The image signals are temporarily stored and stored in the memory as image signals for each color of C and K.

When the photosensitive drum drive motor is started by the start of image recording, the drive gear 140G rotates to rotate the photosensitive drum 110 clockwise, and at the same time, the charger 1
The application of a potential to the photosensitive drum 110 is started by the charging action of 11 (Y).

After a potential is applied to the photosensitive drum 110, the exposure optical system 112 (Y) starts exposure with an electric signal corresponding to a first color signal, that is, an image signal of yellow (Y). An electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the photosensitive layer on the surface by rotational scanning.

The latent image is reversal-developed by the developing device 113 (Y) in a state where the developer on the developing sleeve is not in contact, and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 110.

Next, the photosensitive drum 110 is further provided with a potential on the yellow (Y) toner image by the charging action of the charger 111 (M), and the exposure optical system 112 (M).
Exposure is performed using an electrical signal corresponding to the second color signal, i.e., the magenta (M) image signal.
By the non-contact reversal development by (M), a magenta (M) toner image is sequentially superimposed on the yellow (Y) toner image.

The charger 111 is manufactured by the same process.
(C), exposure optical system 112 (C) and developing unit 113
(C) further produces a cyan (C) toner image corresponding to the third color signal, and the charger 11 (K), the exposure optical system 112 (K), and the developing device 113 (K) produce a fourth color signal. Are sequentially superimposed, and a color toner image is formed on the peripheral surface of the photosensitive drum 110 within one rotation.

The photosensitive drum 1 by each of these exposure optical systems
Exposure to the 10 organic photosensitive layers is performed from the inside of the drum through the transparent substrate described above. Therefore, the second and third
And exposure of the image corresponding to the fourth color signal is performed without any influence of the previously formed toner image,
An electrostatic latent image equivalent to an image corresponding to the first color signal can be formed. In order to stabilize the temperature inside the photosensitive drum 110 and prevent the temperature from rising due to the heat generated by each exposure optical system 112, a material having good thermal conductivity is used for the support member 120. In the case of (1), measures such as radiating heat to the outside through the heat pipe can be suppressed to a level that does not cause any trouble. In the developing operation of each developing device, a developing bias to which a direct current or a further alternating current is applied is applied to the developing sleeve, and a one-component or two-component developer contained in the developing device is subjected to jumping development, and the transparent conductive material is developed. Non-contact reversal development is performed on the photosensitive drum 110 whose layer is grounded.

The color toner image formed on the peripheral surface of the photosensitive drum 110 is once transferred to the peripheral surface of the intermediate transfer belt 114 as an intermediate transfer member.

The intermediate transfer belt 114 has a thickness of 10
Rollers 114A and 114B are made of urethane rubber having an electrical resistance of 10 ⁸ to 10 ¹¹ Ω · cm and having a Teflon (registered trademark) layer having a similar resistance value for separation on the surface layer. , 114C and 114D
And is circulated and conveyed counterclockwise in synchronization with the peripheral speed of the photosensitive drum 110 by the power transmitted to the roller 114D.

Intermediate Transfer Belt 1 as Intermediate Transfer Body
Reference numeral 14 designates a belt surface between the rollers 114A and 114B in contact with the peripheral surface of the photosensitive drum 110.
The transfer roller 115 serving as a transfer member is used to transfer
To form a toner image transfer area at each contact point.

The color toner image adhered to the peripheral surface of the photosensitive drum 110 is first transferred to the intermediate transfer belt 11.
By applying a bias voltage having a polarity opposite to that of the toner to the roller 114 </ b> B at the contact point between the transfer belt 4 and the transfer roller 4, the toner image is sequentially transferred to the peripheral surface of the intermediate transfer belt 114. That is, the color toner image on the drum is conveyed to the transfer area without scattering the toner by the guidance of the grounded roller 114A.
By applying a bias voltage of 1 to 2 kV to B, the image is efficiently transferred to the intermediate transfer belt 114 side.

On the other hand, the transfer paper P is carried out by the operation of the paper feed roller 117 of the paper feed cassette 116 and fed to the timing roller 118, and the transfer roller 115 is synchronized with the transfer of the color toner image on the intermediate transfer belt 114. The paper is fed to the transfer area.

The transfer roller 115 is connected to the intermediate transfer belt 1.
The transfer paper P, which has been rotated clockwise in synchronization with the peripheral speed of the transfer roller 14, is subjected to intermediate transfer in a transfer area formed by a nip portion between the transfer roller 115 and the roller 114 C in the ground state. The color toner images are successively transferred onto the transfer paper P by applying a bias voltage of 1 to 2 kV opposite to the toner to the transfer roller 115 in close contact with the color toner image on the belt 114.

The transfer paper P to which the color toner image has been transferred is neutralized by a static elimination needle 119A, transported to a fixing device 121 via a transport belt 119, and nipped and transported between a heating roller 121A and a pressure roller 121B. Then, after the toner is fused and fixed, the toner is discharged to the outside of the apparatus via a paper discharge roller 122. Also in the present embodiment, by contacting the outer periphery of the heating roller 121A,
Since the above-described external heating roller 16 is disposed, and the above-described cleaning roller 17 is disposed so as to be in contact with the external heating roller 16, image quality can be improved as in the first embodiment. . Note that the configuration shown in FIGS. 3 and 4 can be incorporated in the present embodiment.

Cleaning devices 100, 140, and 150 are installed on the photosensitive drum 110, the intermediate transfer belt 114, and the transfer roller 115, respectively, and the blades of the cleaning devices 100, 140, and 150 are constantly pressed to remove residual toner adhered. The peripheral surface is always kept clean.

FIG. 6 is a view similar to FIG. 2 showing a fifth embodiment of the present invention. The fifth embodiment differs from the above-described embodiment of FIG. 2 only in that the cleaning roller 17 is omitted, and the other configuration is common, so that the description is omitted.

FIGS. 7 to 9 are views similar to FIGS. 2 to 4 showing sixth to eighth embodiments of the present invention. The sixth to eighth embodiments are different from the above-described embodiments of FIGS. 2 to 4 in that instead of the pressure roller 15,
The difference is that a pressure belt 203 is provided.

More specifically, between the pulleys 201 and 202 extending in parallel below the heating roller 14, the surface is formed of a heat-resistant material such as metal such as SUS or PI or the like. A fluororesin having moldability is coated on the order of several tens of μm, or a heat-resistant elastic material such as silicone rubber is coated on the order of several hundred μm (furthermore, the surface of the heat-resistant elastic material is coated with a fluororesin of several tens μm.
A pressure belt 203 is stretched, and its upper surface is in contact with the peripheral surface of the heating roller 14. The pressure belt 203 moves in synchronization with the heating roller 14 in the same manner as the pressure roller 15, and passes through the heating roller 14 while sandwiching the transfer paper on which the toner image has been formed and applying heat and pressure. It has a function of thermally fixing a toner image on transfer paper. For other configurations, see FIG.
Since the fourth embodiment is similar to the fourth to fourth embodiments, the description is omitted.

FIG. 10 is a view similar to FIG. 6, showing a ninth embodiment of the present invention. The ninth embodiment is different from the above-described embodiment of FIG.
The difference is that instead of making contact with the peripheral surface of the heating roller 14, the contact is made with the peripheral surface of the pressure roller 15 and the halogen lamp 15 c is omitted. I do. The surface of the pressure roller 15 is coated with an insulating PFA resin 15d (the same applies to the embodiments of FIGS. 11 to 16 described later).

FIGS. 11 to 13 are views similar to FIGS. 2 to 4 showing tenth to twelfth embodiments of the present invention. Tenth
The twelfth embodiment is different from the above-described embodiment of FIGS. 2 to 4 in that the external heating roller 16 is provided on the pressure roller 15 side instead of providing the external heating roller 16 on the heating roller 14 side.
And the like, and the point that the halogen lamp 15c is omitted.

FIGS. 14 to 16 are views similar to FIGS. 11 to 13 showing thirteenth to fifteenth embodiments of the present invention. First
In the embodiments 3 to 15, a belt mechanism is provided instead of providing the heating roller 14 in the embodiment shown in FIGS.

More specifically, in FIGS. 14 to 16, reference numeral 224 denotes an endless belt-shaped fixing film, which includes a left driving roller 225 and a right driven roller 2.
26 and a heater support 227 of a low heat capacity linear heating element 220 as a heating element disposed below the driving roller 225 and the driven roller 226.

The driven roller 226 also serves as a tension roller for an endless belt-shaped fixing film 224. The fixing film 224 has a predetermined peripheral speed, ie, an image, in a clockwise direction accompanying the clockwise rotation of the driving roller 225. At the same peripheral speed as the transfer speed of the transfer paper (not shown) carrying the unfixed toner image conveyed from the forming unit side on the upper surface, it is rotated and driven without wrinkles, meandering, and speed delay.

The pressing roller 15 is pressed against the lower surface of the heating element 220 by a biasing means (not shown) with a total pressure of, for example, 4 to 7 kg, with the lower film portion of the endless belt-shaped fixing film 224 interposed therebetween. The transfer paper is rotated in a counterclockwise direction, which is a forward direction in the transfer direction of the transfer sheet.

A low heat capacity linear heating element 220 as a heating source
Is a heater support 227 having rigidity, high heat resistance, and heat insulation properties of a lateral hand whose longitudinal direction is the transverse direction of the fixing film (the direction perpendicular to the running direction of the fixing film 224).
The heating element 222 and the temperature measuring element 22 are integrally attached to and held by the lower surface of the heater support 227 along the length of the lower surface.
3 and the like.

The heater support 227 supports the heating element 220 in a heat-insulating manner with respect to the entire apparatus. For example, PPS (polyphenylene sulfide), PAI (polyamide imide), PI (polyimide), PEEK (polyether ether ketone), liquid crystal It can be composed of a high heat-resistant resin such as a polymer, or a composite material of these resins with ceramics, metal, glass and the like.

The temperature measuring element 223 is, for example, a heater substrate 2
Pt provided by applying by screen printing or the like to a substantially central portion of the upper surface of 21 (the surface opposite to the surface on which the heating element is provided)
It is a low-heat-capacity temperature measuring resistor such as a membrane. As the temperature measuring element, a thermistor having a low heat capacity or the like may be arranged so as to be in contact with the substrate.

In the case of the heating element 220 of the present embodiment, electricity is supplied to the linear or band-shaped heating element 222 from both ends in the longitudinal direction, and the heating element 222 generates heat over substantially the entire length.
The energization is 100 V AC, and the energization power is controlled by controlling the phase angle to be energized by an energization control circuit (not shown) including a triac according to the temperature detected by the temperature detecting element 223.

The fixing film 224 is generally 100 μm or less, preferably 40 μm, having heat resistance, releasability and durability.
A single-layer or multi-layer film of μm or less can be used.

Next, the operation of the apparatus of this embodiment will be described.
The description of the operation in the image forming step before the fixing step is omitted.

At the time of fixing, the transfer paper enters between the fixing film 224 and the pressure roller 15 at the pressure contact portion between the heating element 220 and the pressure roller 15, and the unfixed toner image surface is reduced by the transfer speed of the transfer paper. The heating element 2 is in close contact with the lower surface of the fixing film 224 that is rotated in the same direction at the same speed and is overlapped with the fixing film 224 without causing surface deviation or wrinkling.
It passes while receiving a pressing force between the mutual pressure contact portions of the pressure roller 20 and the pressure roller 15. The heating element 220 is energized and heated just before the transfer sheet enters the pressure contact portion by the image formation start signal.

The heat generated by the heating element 220 is transferred to the surface of the fixing film 224 immediately because the heat capacity of the fixing film 224 is very small, and the surface of the fixing film 224 immediately reaches a fixing temperature. When the transfer paper has passed through the pressure contact portion, the power supply is stopped and the fixing film 32 is stopped.
The surface of 4 is immediately cooled.

Although the present invention has been described with reference to the embodiments, it should be understood that the present invention should not be construed as being limited to the above embodiments, and that modifications and improvements can be made as appropriate. is there. For example, when a belt-shaped heating roller is used, an external heating roller may be brought into contact with the surface thereof. Further, as a heating source, an electric heating means such as a nichrome wire or an electromagnetic heating means for heating using an eddy current may be used in addition to the halogen lamp, and the roller itself may be heated.

[0078]

According to the present invention, it is possible to provide an image forming apparatus capable of improving image quality without increasing the size and complexity of the apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged view showing a periphery of a roller in a fixing unit 13;

FIG. 3 is a view similar to FIG. 2, showing a second embodiment of the present invention.

FIG. 4 is a view similar to FIG. 2, showing a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram illustrating a color image forming apparatus according to a fourth embodiment.

FIG. 6 is a view similar to FIG. 2, showing a fifth embodiment of the present invention.

FIG. 7 is a view similar to FIG. 2, showing a sixth embodiment of the present invention.

FIG. 8 is a view similar to FIG. 3, showing a seventh embodiment of the present invention.

FIG. 9 is a view similar to FIG. 4, showing an eighth embodiment of the present invention.

FIG. 10 is a view similar to FIG. 6, showing a ninth embodiment of the present invention.

FIG. 11 is a view similar to FIG. 2, showing a tenth embodiment of the present invention.

FIG. 12 is a view similar to FIG. 3, showing an eleventh embodiment of the present invention.

FIG. 13 is a view similar to FIG. 4, showing a twelfth embodiment of the present invention.

FIG. 14 is a view similar to FIG. 11, showing a thirteenth embodiment of the present invention.

FIG. 15 is a view similar to FIG. 12, showing a fourteenth embodiment of the present invention.

FIG. 16 is a view similar to FIG. 13 showing a fifteenth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming apparatus 2 paper feed cassette 3 transfer paper 4 paper feed roller 5 double running prevention means 6 transport roller 7 registration roller 8 photosensitive drum 9 transfer charger 10 peeling charger 11 separation claw 12 transport belt 13 fixing unit 14 heating roller 15 Pressure roller 16 External heating roller 17 Cleaning roller 18 Temperature control unit 19 Main body control unit 20 Ground conductive brush 21 Auxiliary roller 110 Photosensitive drum 111 Scorotron charger 112 Exposure optical system 114 Intermediate transfer belt 115 Transfer roller 116 Paper feed cassette 117 Paper feed roller 118 Timing Roller 121 Fixing Device 130 Developing Sleeve 221 Heater Substrate 222 Heating Element 223 Temperature Sensor 224 Fixing Film 225 Drive Roller 226 Driven Roller 227 Heater Support 230 Fixing Device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 13/00 F16C 13/00 DE (72) Inventor Kazunori Katata 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term within the formula company (reference) 2H033 AA01 AA21 BA13 BA49 BA54 BA55 BB03 BB04 BB05 BB23 BB24 3J103 AA02 AA14 AA15 AA24 AA41 AA51 BA03 BA15 BA16 BA31 BA41 BA43 FA01 FA02 FA06 FA07 FA18 FA19 GA02 GA52 GA57 HA03 GA04 HA15 HA20 HA37 HA43 HA53 HA54

Claims (9)

[Claims] 1. An image forming apparatus comprising a pair of pressed rollers or a fixing device comprising a pressed roller and a belt, wherein at least one of the rollers is heat-resistant on a cylindrical base material having high thermal conductivity and rigidity. An elastic body is coated, further comprising a metal cylindrical core, a heating source for heating the metal cylindrical core, and a surface layer of the metal cylindrical core is made of a conductive fluororesin. An image forming apparatus, wherein an external heating roller covered with a member is brought into contact with the surface of the heat-resistant elastic body. 2. The image forming apparatus according to claim 1, further comprising a highly releasable insulating resin layer provided on the heat-resistant elastic body. 3. A cleaning member for the external heating roller, which is made of an elastic material having a lower toner releasability than the conductive fluororesin, is brought into contact with the surface of the external heating roller. Item 3. The image forming apparatus according to item 1 or 2. 4. The image forming apparatus according to claim 3, wherein the cleaning member has a roller shape. 5. The surface roughness of an external heating roller is made rougher than the surface roughness of the heat-resistant elastic body or the highly releasable insulating resin layer, and the surface roughness of the cleaning member for an external heating roller is made rougher. The image forming apparatus according to claim 3, wherein: 6. An image forming apparatus comprising a pair of pressed rollers or a fixing device comprising a pressed roller and a belt, wherein at least one of the rollers is heat-resistant on a cylindrical substrate having high thermal conductivity and rigidity. An elastic body is coated, further comprising a metal cylindrical core, a heating source for heating the metal cylindrical core, and a surface layer of the metal cylindrical core is made of a conductive filler or the like. An external heating roller coated with an insulating fluororesin that does not have an abutment on the surface of the heat-resistant elastic body, and from a contact position with the external heating roller, in a rotation direction downstream side of the at least one roller. An image forming apparatus comprising a charge removing unit. 7. The image forming apparatus according to claim 6, wherein a highly releasable insulating resin layer is further provided on the heat-resistant elastic body. 8. The image forming apparatus according to claim 6, wherein said static elimination means comprises a non-contact ground conductive brush. 9. An image forming apparatus comprising a pair of pressed rollers or a fixing device comprising a pressed roller and a belt, wherein at least one of the rollers is provided on a cylindrical base material having high thermal conductivity and rigidity. The heat-resistant elastic body is covered with a conductive fluororesin layer on the surface, and at least a part of the metal core is formed of a heat pipe. An external heating roller provided with an auxiliary roller and provided with a metal cylindrical core and a heating source for heating the metal cylindrical core, and covering the surface layer of the metal cylindrical core with a thin heat-resistant elastic body, An image forming apparatus, wherein the image forming apparatus is in contact with a surface of an auxiliary roller.