JPH05303294A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device high in image quality, a transfer efficiency transfer-fixing efficiency, short in a waiting time, and having excellent durability in low rated power with a extremely simple and small-sized mechanism. CONSTITUTION:A thin elastic cylindrical intermediate transfer body 2 is abutted on a transfer image carrier 1 in a first transfer part and a transfer material 4 is inserted and transported by a first roller 3 internally touching with the intermediate transfer body 2 in a second transfer part and having a heating element 8, and a second roller 5 opposed to the first roller 3 with the intermediate transfer body 2 between, and the intermediate transfer body 2 is noncircularly compressed/deformed to heat/press the transfer material 4 while being rotated. A large nip can easily be secured with a low load because the intermediate transfer body 2 is a thin shell, stable contact and excellent heat conductivity are obtained, high transfer efficiency is secured in the first and second transfer parts, and the miniaturization and high reliability of a device can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an image forming apparatus for transferring a toner image formed on a toner carrying member onto an intermediate transfer member and transferring and fixing the toner image on the intermediate transfer member onto the transfer member. ..

[0002]

2. Description of the Related Art Conventionally, as the image forming apparatus as described above, Japanese Patent Laid-Open Nos. 2-213885 and 2-10807 have been used.
No. 2, JP-A-59-77471, JP-A-57-673.
As disclosed in Japanese Patent Laid-Open No. 56-167164 and the like, a toner image carrier is a drum type, and an intermediate transfer member is often in the form of a belt which easily adheres to the toner image carrier. .. On the other hand, JP-A 2-113284 and JP-A-5-113284
There is also known one in which an intermediate transfer member is constituted by a roller as described in Japanese Patent Publication No. 8-90655 and the like.

[0003]

However, in the method of forming the intermediate transfer member with a belt, at least two rotary driving rollers are required inside the belt to drive the intermediate transfer member belt. In order to prevent lateral movement and meandering and to carry the belt stably, it is necessary to have at least four rollers inside the belt, such as tension rollers and rollers for correcting meandering. Various related mechanisms are required, which not only hinders the reduction in size and weight of the apparatus, but also causes a reduction in the mechanical reliability and durability of the apparatus due to the complicated mechanism.

On the other hand, a method of using a roller having high rigidity as an intermediate transfer member will be described. FIG. 2 is a schematic diagram of an image forming apparatus using a conventional roller intermediate transfer member. Although not shown, charging, exposing, developing, and cleaning means are arranged around the toner image carrier 1, and the toner image carrier 1 rotates while forming an electrostatic latent image and a toner image on the surface thereof. .. The drum-shaped intermediate transfer member 53 is brought into pressure contact with the toner image carrier 1 via the toner image, and the toner image carrier 1 is transferred onto the surface of the drum-shaped intermediate transfer member 53 by a method such as electrostatic or adhesion. Rotate at the same speed in the opposite direction. The drum-shaped intermediate transfer member 53 has a heat generating means 8 therein, and transfers and fixes the toner image on the transfer material 4 by nipping and conveying the transfer material 4 together with the second roller 5 while heating and pressing the transfer material 4. In this case, it is necessary to secure a considerable amount of nip in the transfer and fixing section in order to supply the amount of heat necessary for softening and melting the toner. Therefore, the second roller 5 must be pressed against the drum-shaped intermediate transfer member 53 with a pressure of several kilograms to several tens kilograms. Further, when the toner image carrier 1 is transferred to the drum-shaped intermediate transfer member 53 by the adhesive force, a large pressing force is required for both, so that the drum-shaped intermediate transfer member 53.
Is required to have high rigidity, and the roller base 52 needs to be made of a thick metal. However, because of this, not only does the thermal capacity of the drum-shaped intermediate transfer member 53 increase, a long time is required for the transfer and the temperature rise in the fixing unit, and the cooling rate is slow,
While the roller base body 52 remains at a high temperature, the toner image carrier 1 is transferred at the transfer portion.
To contact. Therefore, the temperature of the toner image carrier 1 also rises,
The electrostatic latent image forming performance is deteriorated, and the charging performance and mechanical strength of the toner at the time of development are deteriorated, resulting in deterioration of image quality.
Furthermore, since the drum-shaped intermediate transfer member 53 and the second roller 5 are pressed against each other with a large load, a large amount of electric power is consumed for driving rotation, and driving noise is very large. Further, in order to secure a nip at the transfer / fixing unit, the drum-shaped intermediate transfer member 5
3. The second roller 5 was forced to have a large diameter, which hindered the downsizing and cost reduction of the device. On the other hand, the toner image carrier 1
It is necessary to surely transfer the above toner image onto the drum-shaped intermediate transfer member 53. However, in various transfer methods such as electrostatic transfer, adhesive transfer, and thermal pressure transfer, it is thick and highly rigid such as an aluminum tube. A surface layer 5 made of an elastic material layer such as rubber on the roller base 52.
1 is provided to make uniform and uniform contact. But,
A nip width of several mm or more is required to make uniform and uniform contact. Therefore, the elastic layer is made of, for example, silicone rubber having a thickness of about 2 mm or more. In the case of contact-type electrostatic transfer, it is necessary to apply a voltage higher than a predetermined value to the toner.Therefore, a transfer nip with a time constant determined by the electric capacity and resistance of the transfer member is required, or a high voltage is applied. Had to do. Further, since there is a limit to the increase in the nip width due to the increase in the diameters of the toner image carrier 1 and the drum-shaped intermediate transfer member 53, the pressure applied between the two is increased to increase the nip width, but at the same time, the contact pressure is also increased. However, in particular, in the case of electrostatic transfer, a phenomenon of hollow image due to aggregation of toner occurs and the image quality is deteriorated. If the intermediate transfer member is provided with a rubber-like elastic layer having a low thermal conductivity and a large thickness, the thermal resistance is further increased.Therefore, the waiting time from the start of heating to the transfer and fixing is extremely long. A heating element with a large rated power is used to make it longer and to reduce it as much as possible. This consumes a large amount of power when heat is generated, so the power supply capacity of the device must be increased. Not only that, in order to maintain a predetermined surface temperature during fixing, the interface temperature between the elastic body layer and the substrate 52 rises, causing thermal deformation of the elastic body layer and deterioration of durability due to thermal cycling. Further, since the elastic layer is inferior in mechanical durability such as abrasion resistance, it is a factor that the wear is seriously caused by the contact of the temperature detecting thermistor, the claw for separating the transfer material, or the contact of the transfer material itself, which shortens the life of the apparatus. It was. further,
When the elastic layer such as silicone rubber is the surface layer, wettability,
In many cases, the releasability from the toner is worse than the smoothness of the surface,
The transfer efficiency at the time of transfer fixing was low, and an offset phenomenon in which toner remained on the intermediate transfer member occurred. Due to the rotation of the intermediate transfer member, the toner adheres to the toner carrier, is transferred and fixed to the next transfer material again, or adheres to the second roller and stains the back surface of the transfer material to deteriorate the image. . Not only that, the roller intermediate transfer body has a thick base body and a thick surface layer elastic body, and the belt-shaped intermediate transfer body also has a thick elastic layer, so that the heat capacity is large and after transfer fixing. The temperature of the intermediate transfer member does not drop sufficiently. Therefore, the toner is relatively soft, and in the case of the contact type transfer, the toner adheres firmly to the toner layer carrier due to the contact pressure and causes cleaning failure. Therefore, the continuous occurrence of a plurality of image defects after offsetting leads to the replacement of the toner image carrier and the cleaning means, which is a fatal defect of the apparatus.

The present invention has been made to solve the above problems, and an object thereof is to efficiently transfer a toner image on a toner image carrier to an intermediate transfer member and a toner image on the intermediate transfer member to a transfer material. An image forming device that enables transfer, does not cause offset, has high mechanical reliability with excellent wear resistance and durability of the intermediate transfer member and the entire device, and has a short waiting time and low power consumption is extremely simple. And it is to provide with a small mechanism.

[0006]

In the image forming apparatus of the present invention, the toner image formed on the toner image carrier 1 is transferred onto the intermediate transfer member 2 at the first transfer portion, and the toner image is transferred onto the intermediate transfer member 2. In an image forming apparatus that transfers and fixes a toner image on a transfer material 4 at a second transfer portion, the intermediate transfer body 2 is configured as an elastically deformable thin-walled cylindrical shape, and the second transfer portion is provided with the intermediate transfer body 2 of the intermediate transfer body 2. A first roller 3 that is in contact with the inner periphery and has a heating element 8 and a second roller 5 that sandwiches the intermediate transfer body 2 and faces the first roller 3 are arranged. The transfer material 4 is the intermediate transfer body 2 and the second roller. The intermediate transfer member 2 is heated and pressed between 5 and 5, and is compressed and deformed into a non-circular shape by the pressing of the first transfer portion and the second transfer portion, and is rotated.

Further, the toner image formed on the toner image carrier 1 is transferred to the intermediate transfer member 2 at the first transfer portion, and the toner image on the intermediate transfer member 2 is transferred to the transfer material 4 at the second transfer portion. In the image forming apparatus for transferring and fixing the image on the upper surface, the intermediate transfer member 2 has conductivity or high resistance and is electrically grounded at the second transfer portion.

Further, the toner image formed on the toner image carrier 1 is transferred onto the intermediate transfer member 2 at the first transfer portion, and the toner image on the intermediate transfer member 2 is transferred at the second transfer portion 4 to the transfer material 4. In the image forming apparatus for transferring and fixing the image on the upper surface, the intermediate transfer body 2 is characterized by containing a filler having high thermal conductivity.

Further, the toner image formed on the toner image carrier 1 is transferred onto the intermediate transfer member 2 at the first transfer portion, and the toner image on the intermediate transfer member 2 is transferred at the second transfer portion 4 to the transfer material 4. In an image forming apparatus that transfers and fixes an image onto an intermediate transfer member 2, the intermediate transfer member 2 is configured to have a thin cylindrical shape that is elastically deformable, and contacts the inner periphery of the intermediate transfer member 2 at the first transfer portion and sandwiches the intermediate transfer member 2 therebetween. A third roller 9 facing the toner image carrier 1 is arranged, and the intermediate transfer body 2 is compressed and deformed into a non-circular shape by the pressure of the first transfer portion and the second transfer portion, and is rotated.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.

The term "conductivity" as used in the present invention means that the resistivity is 10
Indicates ¹⁰ Ωcm or less. Also, high resistance means a resistivity of 10 ¹¹
It refers to 10 ¹⁴ Ωcm or less in the range of Ωcm or more.

(Embodiment 1) FIG. 1 is a main schematic view of a first image forming apparatus according to the present invention. On the surface of the drum-shaped toner image carrier 1, a photoconductor made of a photoconductive material such as selenium, zinc oxide, or an organic photoconductor, or an insulator made of an insulating material is used. Although not shown, although not shown in the drawing, the electrostatic latent image is formed by the charging and exposure means, which are provided on the periphery of the substrate, and then rotated clockwise while forming the toner image by the developing means. The intermediate transfer body 2 is composed of a thin-walled cylindrical elastic body that can be easily elastically deformed. FIG. 3 is an illustration of an intermediate transfer member of the image forming apparatus of the present invention. The intermediate transfer member 2 has a thickness of several tens to several hundreds of μm and a fluororesin layer of several tens of μm thickness or several hundreds of μm thickness on a thin elastic cylindrical base 7 made of nickel, stainless steel, plastic or the like. A surface layer 6 composed of a thin elastic layer of silicone rubber or the like and having releasability is arranged. The intermediate transfer body 2 having such a thin shell structure has sufficient rigidity to keep the substantially cylindrical shape 42 when no force is applied from the outside, and easily when a compressive force acts in the diametrical direction, for example. It is elastically deformed and deformed into a substantially elliptical shape 43. The toner image carrier 1 is in contact with the outer periphery of the intermediate transfer member 2 to form a first transfer portion. Further, a second roller 5 circumscribing the intermediate transfer body 2 is arranged in a direction substantially opposite to the first transfer portion. Further, a first roller 3 having a heating element 8 is arranged at a position facing the second roller 5 and on the inner circumference of the intermediate transfer body 2, and is rotated counterclockwise.
The first roller 3 and the second roller 5 narrow the intermediate transfer member 2 to form a nip and form a second transfer portion. Further, the distance between the first transfer portion and the second transfer portion is set shorter than the diameter of the intermediate transfer body 2 when it is free (when there is no load), and therefore the intermediate transfer body 2 is elastically deformed like a substantially elliptical shape 43. It rotates counterclockwise with the toner image carrier 1 at a constant peripheral speed. Further, the second roller 5 rotates clockwise along with the rotation of the first roller 3.
The transfer material 4 such as paper is guided to the nip portion between the intermediate transfer body 2 and the second roller 5 of the second transfer portion and is conveyed under a narrow pressure, so that the heat from the heating element 8 is transferred to the toner and the transfer material 4. The toner is transferred and fixed onto the transfer material 4 together with the pressure applied by the pressing of the first roller 3 and the second roller 5. Since the intermediate transfer member 2 can be deformed into a substantially elliptical shape with a small pressing force,
Also, the radius of curvature in the vicinity of the second transfer portion becomes large, and when a large-diameter member is used, the same effect is obtained, and the nip width is increased.

As described above, since the intermediate transfer body 2 has a thin shell structure, it has a high ability to retain its own shape and can rotate while maintaining a substantially elliptical shape without the need for a tension applying mechanism such as a tension roller. Is. Therefore, at least the first roller 3 inside the intermediate transfer member 2 and the second roller 5 outside should be arranged. Further, as in the conventional example, there are a plurality of rollers inside the belt, and when tension is applied, the belt meanders due to the parallelism deviation of the respective axes, so a complicated meandering prevention mechanism is required. Then, since the intermediate transfer body 2 is held at one place by the first roller 3 and the second roller 5 and abuts on the first transfer portion, the deviation and the meandering of the intermediate transfer body due to the parallelism deviation of the respective axes are prevented. Very few.
Only the deviation of the intermediate transfer member 2 due to the difference in the diameter of the first roller 3 in the axial direction is a problem, but the amount of deviation due to this alone is small. It is possible to completely suppress it with a simple structure such as providing a perforation hole in the above to guide it with a sprocket, or providing a first roller 3 with a crown that becomes thick toward the center in the axial direction. In this way, the device of the present invention has a much simpler structure than the conventional belt system, has a small number of parts, is small and compact, and is easy to assemble and replace, realizing a device with high mechanical reliability and durability. did it.

Since the intermediate transfer body 2 has a thin shell structure, a large transfer nip width is secured in the first transfer portion with a very small pressing force, so that stable, uniform and uniform contact is secured. .. Therefore, the transfer efficiency can be increased by any of the adhesive, electrostatic and thermal pressure transfer methods. For example, in the case of adhesive transfer, since the spring constant for the deformation of the intermediate transfer body 2 is small, the pressure change due to the variation in the diameter, the thickness, etc. of the intermediate transfer body 2 and the variation in the deformation amount is small.
Since the nip width and the pressing force can be maintained at substantially constant values, the adhesive force between the toner and the intermediate transfer member 2 is stable, and good transfer is possible. Also in the case of electrostatic transfer, stable transfer is possible because a large nip width can be stably maintained at low pressure, and transfer with a low bias voltage and high-quality toner image transfer with no void due to aggregation are realized. did. Even in the case of the thermal pressure transfer method, since the nip width is wide, the amount of heat transferred to the toner and the intermediate transfer member 2 is large, and good transfer efficiency is obtained. Further, since the nip width is wide, the temperature of the heating element for securing a constant amount of heat received by the toner may be low, so that the temperature rise of the toner image carrier 1 is small and the adverse effect on the photoconductor layer is reduced.

Further, since the intermediate transfer member 2 has a thin shell structure, the high temperature portion of the intermediate transfer member 2 due to the heat generated during transfer and fixing in the second transfer portion has a small heat capacity of the intermediate transfer member 2 and is re-established. It is sufficiently cooled to reach the first transfer portion, and transfer is possible at room temperature. Therefore, the temperature of the toner image carrier 1 or the toner does not rise, the electrostatic latent image forming performance is not adversely affected, and the stable charging performance and high image quality are realized without deteriorating the charging performance and mechanical strength of the toner. did.

In the second transfer section, the intermediate transfer member 2
Is deformed into a substantially elliptical shape and the radius of curvature is increased, so that the contact nip width between the intermediate transfer body 2 and the transfer material 4 is increased, so that sufficient heat conduction can be secured even if the diameter of the second roller 5 is reduced. The heat capacity of the two rollers 5 was reduced. Further, the intermediate transfer member 2 has a very small heat capacity because the substrate 7 has a thickness of several tens to several hundreds of μm, and the thermal resistance is small, so that the temperature rising rate is also high. Therefore, the temperature of the second transfer portion rapidly rises to a temperature at which transfer and fixing can be performed in a few seconds by heating the heating element 8 and the heat stable state is reached immediately so that the waiting time of the apparatus is shortened and a quick start is realized. ..

Further, since the diameter of the intermediate transfer member 2 and the second roller 5 can be reduced, the size and cost of the apparatus can be reduced.

On the other hand, the toner image carrier 1, the intermediate transfer member 2,
Since the first roller 3 and the second roller 5 are each pressed by a small load, the electric power required for driving rotation is small, and a device with low driving noise and excellent quietness is realized.

Since the intermediate transfer member 2 has a thin shell structure, a large transfer nip width is ensured with a very small pressure in the first transfer portion, so that stable, uniform and uniform contact is ensured, and transfer efficiency is improved. Since it is possible to increase the temperature, it is not necessary to use a thick elastic body layer such as rubber for the surface layer 6 of the intermediate transfer body 2, and the toner release at the transfer and fixing at the second transfer portion can be performed. It is only necessary to consider the properties, and by arranging a fluororesin layer with a thickness of several tens of μm or a thin silicone rubber layer of several hundreds of μm, good transfer efficiency was achieved in both the first transfer part and the second transfer part. .. When an elastic body such as thin-walled silicone rubber is used for the surface layer 6, it is possible to improve wear resistance and thermal conductivity with additives. further,
In order to improve releasability and durability, the surface layer 6 may be a thin film surface layer of fluororesin provided on the elastic body. In this case, since the elastic body such as silicone rubber is thin, heat transfer is not hindered and sufficient transfer efficiency is achieved. Generally, the elasticity is lost by the additive, but in the present invention, since the elasticity is added to the substrate 7 which is a thin shell, even if the elasticity of the surface layer 6 is slightly lost, the entire intermediate transfer body 2 sufficiently acts as an elastic body. Therefore, since the thermal resistance and the thermal capacity of the surface layer 6 of the intermediate transfer member 2 are minimized, the waiting time from the start of heating to the transfer and fixing can be shortened, and the rated power of the heating element is also small. Therefore, the power supply capacity of the device can be reduced. Further, it is possible to prevent the interface temperature between the surface layer 6 and the base body 7 from becoming higher than that, to prevent the thermal deformation of the surface layer and the deterioration of the durability due to the thermal cycle, and to prevent the temperature detection thermistor and the claw for separating the transfer material. It has excellent wear resistance against contact and contact of the transfer material itself, improving the life of the device.

Further, in the present invention, since the intermediate transfer member 2 is thin, the heat resistance and heat capacity are small, the surface layer 6 has a good releasability, the wear resistance is excellent, and the fluorine having a stable surface smoothness is used. Since good heat conduction can be realized even if a resin is used, the releasing property from the toner is good, the transfer efficiency at the time of transfer fixing is high, and the offset phenomenon in which the toner remains on the intermediate transfer member is prevented. Therefore, due to the rotation of the intermediate transfer member, the toner adheres to the toner carrier, is again transferred and fixed to the next transfer material, or adheres to the second roller to stain the back surface of the transfer material to deteriorate the image. There is no. In addition, since the heat capacity is small, the temperature of the intermediate transfer member is sufficiently lowered after the transfer and fixing. Therefore, there is no softening of the toner, and in the case of contact type transfer, the toner is firmly attached to the toner image bearing member by the contact pressure, and cleaning failure does not occur. Therefore, it is possible to prevent a fatal defect of the device such as continuous occurrence of image defects of a plurality of sheets after the offset, replacement of the toner image carrier, replacement of the cleaning means, etc., and a highly reliable device is realized. did it.

(Second Embodiment) FIG. 4 is a main schematic view of a second image forming apparatus according to the present invention.

The drum-shaped toner image carrier 1 has a photoconductive material such as selenium, zinc oxide, or an organic photoconductive material on its surface, which is a photoconductor having a sensitivity of at least 700 to 800 nm, or an insulator made of an insulating material. Is formed on a high-rigidity substrate made of aluminum or an alloy thereof, and an electrostatic latent image is formed by the charging means 10, the exposure means 11 and the like arranged in the periphery, and then a toner image is formed by the developing means 12. Rotate clockwise. As the charging means 10, a contact type roller charging means, a brush charging means, a non-contact scorotron charging means, or the like is used. As the exposing means 11, a laser scanning exposing means, an exposing means using a linear light source such as an LED, or the like is used. The developing means 12 is constituted by a contact type or non-contact type developing means. The intermediate transfer body 2 is composed of a thin-walled cylindrical elastic body that can be easily elastically deformed. The cleaning unit 13 is disposed after the first transfer unit and removes untransferred residual toner. The contact type means may be configured to be separable and contactable as necessary.

The intermediate transfer member 2 is made of a metal or alloy thin film such as nickel or stainless steel having a thickness of several tens to several hundreds of μm, or a resin thin film such as polyimide, polyaramid, polyamide, polyamideimide, polysulfone or polyester. For example, PTFE (tetrafluoroethylene) having a thickness of several μm to several tens of μm is formed on the elastic cylindrical thin substrate 7.
Fluorine resin layer such as FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), or silicone rubber having a thickness of several tens to several hundreds of μm The surface layer 6 is formed by arranging a thin elastic layer such as a fluororubber and a mixture thereof with a fluororesin. The intermediate transfer body 2 having such a thin shell structure has sufficient rigidity to maintain a substantially cylindrical shape when no force is applied from the outside, and is easily elastic when a compressive force acts in the diametrical direction, for example. It deforms and transforms into a substantially elliptical shape. The toner image carrier 1 is in contact with the outer periphery of the intermediate transfer member 2 to form a first transfer portion.

Toner transfer is performed by electrostatic transfer in the first transfer section. The third roller 9 is arranged to face the toner image carrier 1 and to sandwich the intermediate transfer member 2. The transfer bias voltage can be applied from the intermediate transfer body 2 by direct contact with a terminal or the like, but in the present embodiment, conductivity is imparted to the third roller 9, and further the base body 7 of the intermediate transfer body 9 is provided. Electrostatic transfer was realized by making one or both of the surface layers 6 conductive and supplying a transfer bias voltage to the third roller 9. When the transfer bias voltage is applied using the third roller 9, the voltage is applied from this shaft or the like, so that the contact stability is excellent and the generation of noise due to the contact can be suppressed with a simple configuration. Further, it is convenient to prevent a large current from flowing when a pinhole or the like is generated in the toner image carrier 1 by appropriately setting the resistance value of the third roller 9. That is, since the selection range of the resistance value of the intermediate transfer body 2 is widened, a material excellent in releasability, elasticity and the like can be used. Further, since the intermediate transfer body 2 is nipped and conveyed at the first transfer portion, vibration, slippage, and the like are suppressed, and conveyance stability is improved. Particularly, it has a remarkable effect at the time of high-speed transfer.

In the intermediate transfer member 2, when the substrate 7 is made of resin, low resistance substance powder such as metal powder, for example, carbon is added by several tens weight percent or less, preferably 3 weight percent to 10 weight percent to improve conductivity. Granted. Also for the surface layer 6, conductivity is imparted by adding an appropriate amount of low resistance powder. For example, carbon fluoride may be contained in an amount of 1 to 25% by weight, or carbon may be contained in an amount of 25% by weight or less, preferably 3% by weight.
It is also possible to add conductivity by weight percent to 10 weight percent, or to add conductivity by filling powder of metal, titanium dioxide, zinc oxide or the like. In this case, the substrate 7 and the surface layer 6 each have a resistivity of 10 ¹⁰ Ωcm or less, preferably 10 ⁸ Ωcm or less.

Further, a second roller 5 circumscribing the intermediate transfer member 2 is arranged in a direction substantially opposite to the first transfer portion. Further, a first roller 3 having a heating element 8 is arranged at a position facing the second roller 5 and on the inner circumference of the intermediate transfer body 2, and is rotated counterclockwise. The first roller 3 and the second roller 5 narrow the intermediate transfer member 2 to form a nip and form a second transfer portion. Further, the distance between the first transfer portion and the second transfer portion is set to be shorter than the diameter of the intermediate transfer body 2 when it is free (when there is no load).
The intermediate transfer body 2 is elastically deformed like a substantially elliptical shape and rotates counterclockwise with the toner image carrier 1 at a constant circumferential speed. Further, the second roller 5 rotates clockwise along with the rotation of the first roller 3. The transfer material 4 such as paper is guided to the nip portion between the intermediate transfer body 2 and the second roller 5 of the second transfer portion and is conveyed under a narrow pressure, so that the heat from the heating element 8 is transferred to the toner and the transfer material 4. The toner is transferred and fixed onto the transfer material 4 together with the pressure applied by the pressing of the first roller 3 and the second roller 5. Since the intermediate transfer body 2 can be deformed into a substantially elliptical shape with a small pressing force, the radius of curvature in the vicinity of the first transfer portion and the second transfer portion becomes large, and the same effect can be obtained by using a large diameter member. Each nip width increases. In this case, the first roller 3 and the second row 5 of the second transfer portion are each made of an electrically insulating or highly resistive material.

In the case of the contact type electrostatic transfer system, it is necessary to apply a voltage higher than a predetermined value necessary for the transfer to the toner. When a transfer bias voltage is applied to the combined electric capacity C and combined resistance R of the transfer member and the toner, the voltage applied to the toner gradually rises according to a time constant proportional to C / R and saturates at a constant value. .. Therefore, in order to keep the voltage of the toner at the predetermined value or higher, it is necessary to secure the transfer time of the predetermined value or higher or increase the transfer bias voltage. Transfer time T
Is determined by the transfer nip width W / transfer portion passing speed S, and it is desirable that the transfer nip W is sufficiently large or the transfer speed S is sufficiently small. With the configuration of the present invention, a large nip width can be easily secured at a low load in the first transfer portion, and good transfer efficiency can be secured even if the transfer speed is increased. As well,
Because of the low load, hollowing due to toner aggregation did not occur and high quality transfer became possible. Further, the transfer bias voltage can be set to a value lower than the discharge start voltage, and problems such as toner explosion that may be observed in electrostatic transfer can be suppressed, and higher image quality and higher resolution can be achieved. A non-contact type electrostatic transfer means such as a corotron may be used as the electrostatic transfer means. Further, the intermediate transfer member 2 may have a structure in which the base 7 and the surface layer 6 are integrated.

The configuration and effects described in the first embodiment are the same as in the second embodiment.

(Embodiment 3) A third embodiment of the present invention will be described.

When a transfer method other than electrostatic transfer such as adhesive transfer is adopted in the first transfer section, it is necessary to impart conductivity to the intermediate transfer body 2 or the surface layer 6 by transferring the second transfer section. It also has a special effect during fixing. When the intermediate transfer body 2 is electrically insulating, the intermediate transfer body 2 and the second roller 5 are charged to several KV by the passage of the transfer material 4, but when the intermediate transfer body 2 is electrically conductive and is grounded, it is intermediate. The charging of the transfer body 2 and the second roller 5 is extremely reduced. In addition, even when the second roller 5 is not grounded, it has the effect of absorbing and uniformizing the charge of the second roller 5. As a result, in the case of positively charged toner, the electrostatic charge on the intermediate transfer member 2 is greatly reduced, and the attraction force does not act on the toner and the intermediate transfer member 2. Therefore, the releasing property of the surface of the intermediate transfer member 2 is low or the heating temperature is high. If the toner is too high, the toner adheres to the intermediate transfer member 2 and the offset phenomenon in which the toner is not transferred and fixed on the transfer material 4 does not occur, the toner adheres to the toner image carrier 1 by the rotation of the intermediate transfer member 2, or Good fixing characteristics were realized without causing image deterioration due to transfer-fixing to the next transfer material 4 or adhesion to the second roller 5 to stain the back surface of the transfer material 4. When the intermediate transfer member 2 is conductive with negatively charged toner and is not grounded, the second roller 5 is strongly negatively charged as the transfer material 4 passes, but both are not charged while the transfer material 4 is absent. And the negative charge of the second roller 5 moves to the intermediate transfer member 4. Therefore, the intermediate transfer member 4
Both the toner and the toner were negatively charged, and the repulsive force suppressed the offset phenomenon. Further, due to the electrostatic force and the offset force, the transfer material 4 is less likely to be wound around the intermediate transfer body 2 and the second roller 5, and stable transfer fixing and conveyance of the transfer material 4 without paper jams or the like are possible.

Embodiment 2 Needless to say, the configurations and effects described in the following are the same as in Embodiment 3.

(Embodiment 4) A fourth embodiment of the present invention will be described.

When the electrostatic transfer system is adopted in the first transfer section, it is very important to impart high resistance to the intermediate transfer member 2 or the surface layer 6 even during transfer and fixing of the second transfer section. Have a significant effect. The high resistance referred to here means that the resistivity is 10
^It means ¹¹ Ωcm or more and 10 ¹⁴ Ωcm or less. Intermediate transfer body 2
Is electrically insulative, the intermediate transfer member 2 and the second roller 5 are charged to several KV by the passage of the transfer material 4.
Has a high resistance and is grounded, the charging of the intermediate transfer body 2 and the second roller 5 is reduced. In addition, even when the second roller 5 is not grounded, it has the effect of absorbing and uniformizing the charge of the second roller 5. As a result, in the case of positively charged toner, the charge of the intermediate transfer body 2 is reduced, and the attraction force between the toner and the intermediate transfer body 2 is also reduced, so that the releasing property of the surface of the intermediate transfer body 2 is low or the heating temperature is too high. In some cases, toner is used as the intermediate transfer member 2
The occurrence of an offset phenomenon that is adhered to the transfer material 4 and is not transferred and fixed to the transfer material 4 is suppressed, and the toner is adhered to the toner image carrier 1 by the rotation of the intermediate transfer body 2 or is transferred and fixed to the next transfer material 4 again. The image is not deteriorated by being attached to the second roller 5 and soiling the back surface of the transfer material 4, thus achieving good fixing characteristics. In addition, the intermediate transfer member 2 is charged with negatively charged toner.
Has high resistance and is not grounded, the second roller 5
Is strongly charged with a negative polarity as the transfer material 4 passes, but both are in contact while the transfer material 4 is not present, and the negative charge of the second roller 5 moves to the intermediate transfer body 4. Therefore, both the intermediate transfer member 4 and the toner are negatively charged, and the repulsive force suppresses the offset phenomenon. Furthermore, due to electrostatic force and offset force,
The transfer material 4 is less likely to wind around the intermediate transfer body 2 and the second roller 5, and stable transfer fixing and transfer of the transfer material 4 without paper jams or the like are possible.

In the case of electrostatic transfer, a transfer bias voltage is applied between the intermediate transfer body 2 and the toner image carrier 1 at the first transfer portion, but the intermediate transfer body 2 of this embodiment has a resistivity of 10%. ¹¹ Ω
cm to 10 ¹⁴ Ωcm, which is a high resistance material, and the intermediate transfer member 2 has a thin thickness of several hundreds μm or less, even if the intermediate transfer member 2 is grounded at the second transfer portion, The leak between the transfer part and the second transfer part is virtually negligible. As an example, the nip width 1, the length w between the first transfer portion and the second transfer portion of the intermediate transfer body 2, the thickness h of the intermediate transfer body 2, the resistance value r1 in the thickness direction of the intermediate transfer body 2, the intermediate If the resistance value in the circumferential direction of the transfer body 2 is r2, the resistance value ratio in the circumferential direction and the thickness direction is r2 / r1 = (l · w) / h ² , and l = 1 cm, w
= 3 cm, h = 0.1 cm even in the extreme case of this embodiment, r2 / r1 = 300, and since the ratio is at least 100 or more and usually 1000 or more, there is a leak between the first transfer portion and the second transfer portion. Can be ignored. Therefore, in the first transfer portion, it is possible to apply a voltage of a predetermined value or more necessary for transfer to the toner, and good transfer can be realized.

It goes without saying that the configuration and effects described in the first embodiment are the same as in the fourth embodiment.

(Fifth Embodiment) A fifth embodiment according to the present invention will be described.

The intermediate transfer member 2 is formed of a thin film of metal or alloy such as nickel or stainless steel having a thickness of several tens to several hundreds of μm, or a resin thin film such as polyimide, polyaramid, polyamide, polyamideimide, polysulfone or polyester. A few μm to a few tens of μ on a thin-walled substrate 7 having an elastic cylindrical shape
m thickness, for example, PTFE (tetrafluoroethylene), F
Fluorine resin layer such as EP (tetrafluoroethylene-hexafluoropropylene copolymer), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), or silicone rubber having a thickness of several tens to several hundreds of μm The surface layer 6 is formed by arranging a thin elastic layer such as a fluororubber and a mixture thereof with a fluororesin. When the intermediate transfer member 7 is made of the above resin, when the surface layer 6 is a fluororesin, or when the surface layer 6 is a thin rubber, the resin or the rubber contains a high thermal conductive filler. For example, as the filler, metal powder such as aluminum and copper, silicone carbide (SiC), silicon oxide (SiO),
Inorganic compounds such as alumina, nickel oxide, cobalt oxide, zinc oxide, titanium oxide and the like are preferably used in combination of 10
When the content was from 25% by weight to 25% by weight, there was no offset and transfer and fixing with sufficient fixing strength could be performed. If it is less than 10% by weight, the heat conduction remains within a certain range, resulting in poor fixing, and if it is 25% by weight or more, the releasability deteriorates and offset occurs.
In the case of the surface layer 6, a solution of fluororubber or fluororesin dispersed in water mixed with a filler having a high thermal conductivity and a curing agent is coated on the substrate 7 to a thickness of 500 μm, and then at 250 ° C.
To 400 ° C.

Usually, the thermal conductivity of fluororesin is 0.000.
5 cal / cm · sec · ° C, and even silicone rubber 0.0003 to 0.0006 cal / cm · sec ·
The temperature is as low as about 1 / 1,000 of that of aluminum and copper, and it is necessary to make the thickness as thin as possible in terms of heat conduction. However, in order to cover the irregularities of the base body 7 and in terms of abrasion resistance against contact with a thermistor for temperature detection, a claw for separating the transfer material, etc., a film thickness of the surface layer 6 of 20 μm or more is required. In order to ensure stable contact with the transfer material, 100 μm
As described above, the rubber-like elastic layer having a thickness of 300 μm or more is preferable, and the deterioration of the fixing property due to the heat resistance and the deterioration of the durability due to the high temperature are as described in the conventional example. But,
As described above, the thermal conductivity of the intermediate transfer member 2 is remarkably improved by adding an appropriate amount of the high thermal conductive filler, and the thickness is a thin shell having a thickness of several tens to several hundreds of μm. Since it is remarkably small, the improvement effect described in Example 1 is further promoted, and a device with a short waiting time for the device to reach a thermal stable state, power saving, low rated power, and a small and long-life device are realized and sufficient. It has become possible to achieve transfer fixing with excellent fixing strength and offset. The configurations and effects described in the first and second embodiments are the same as in the third embodiment.

(Embodiment 6) FIG. 5 is a main schematic view of a sixth image forming apparatus according to the present invention.

On the surface of the drum-shaped toner image carrier 1, a photoconductor made of a photoconductive material such as selenium, zinc oxide, or an organic photoconductor or an insulator made of an insulating material is made of aluminum or its alloy. It has a highly rigid substrate. Charging means 20 and exposure means 11 arranged in the periphery
After the electrostatic latent image is formed by, for example, the developing means 22, 23,
The toner particles 24 and 25 rotate clockwise while forming a toner image. As the charging means 20, for example, a non-contact scorotron charging means or the like is used. As the exposing means 11, a laser scanning exposing means, an exposing means using a linear light source such as an LED, or the like is used.
The developing means 22 is a yellow (Y) color toner, the developing means 23 is a magenta (M) color toner, the developing means 24 is a cyan (C) color toner, and the developing means 25 is a black (K) color toner. Each color toner is stored. Also,
These are constituted by contact type or non-contact type developing means. The intermediate transfer body 2 is composed of a thin-walled cylindrical elastic body that can be easily elastically deformed. The cleaning unit 26 is disposed after the first transfer unit and removes untransferred residual toner. The contact type means may be configured to be separable and contactable as necessary.

FIG. 3 is an illustration of an intermediate transfer member of the image forming apparatus of the present invention. The intermediate transfer member 2 has a thickness of several tens to several hundreds of μm and a fluororesin layer of several tens of μm thickness or several hundreds of μm thickness on a thin elastic cylindrical base 7 made of nickel, stainless steel, plastic or the like. A surface layer 6 composed of a thin elastic layer of silicone rubber or the like and having releasability is arranged. The intermediate transfer body 2 having such a thin shell structure has sufficient rigidity to maintain a substantially cylindrical shape when no force is applied from the outside, and is easily elastic when a compressive force acts in the diametrical direction, for example. It deforms and transforms into a substantially elliptical shape. The toner image carrier 1 is in contact with the outer periphery of the intermediate transfer member 2 to form a first transfer portion. The transfer of the toner in the first transfer portion is performed by, for example, electrostatic transfer. The third roller 9 is arranged to face the toner image carrier 1 and to sandwich the intermediate transfer member 2. The transfer bias voltage can be applied from the intermediate transfer member 2 by direct contact with a terminal or the like, but in the present embodiment, the third roller 9 is made conductive, and the intermediate transfer member 2 is made conductive or Electrostatic transfer was realized by providing high resistance and supplying a transfer bias voltage to the third roller 9. When the transfer bias voltage is applied using the third roller 9, the voltage is applied from this shaft or the like. Further, a second roller 5 circumscribing the intermediate transfer body 2 is arranged in a direction substantially opposite to the first transfer portion. Further, a first roller 3 having a heating element 8 is arranged at a position facing the second roller 5 and on the inner circumference of the intermediate transfer body 2, and is rotated counterclockwise.
The first roller 3 and the second roller 5 narrow the intermediate transfer member 2 to form a nip and form a second transfer portion. Further, the distance between the first transfer portion and the second transfer portion is set shorter than the diameter of the intermediate transfer body 2 when it is free (when there is no load), and therefore the intermediate transfer body 2 is elastically deformed like a substantially elliptical shape 43. It rotates counterclockwise with the toner image carrier 1 at a constant peripheral speed. Further, the second roller 5 rotates clockwise along with the rotation of the first roller 3.
The transfer material 4 such as paper is guided to the nip portion between the intermediate transfer body 2 and the second roller 5 of the second transfer portion and is conveyed under a narrow pressure, so that the heat from the heating element 8 is transferred to the toner and the transfer material 4. The toner is transferred and fixed onto the transfer material 4 together with the pressure applied by the pressing of the first roller 3 and the second roller 5. Since the intermediate transfer member 2 can be deformed into a substantially elliptical shape with a small pressing force,
Also, the radius of curvature in the vicinity of the second transfer portion becomes large, and when a large-diameter member is used, the same effect is obtained, and the nip width is increased. Further, the intermediate transfer member 2 is determined so that its total length is longer than the maximum recording paper used or the maximum value of the length of the image to be recorded is taken into consideration. The second roller 5 is rotatably supported at one end of a lever 30 which is rotatably supported by a fulcrum 31, and a spring 27 is connected to the lever 30 to apply a negative biasing force to the second roller 5 to move the intermediate transfer body 2 Pressurized. On the other hand, the solenoid 28 is connected to the lever 30 and operates by a signal 29 to release the negative force of the spring 27,
The second roller 5 can be moved back and forth.

Recording of a color image by this apparatus is performed in the following procedure.

First, the surface of the toner image carrier 1 rotating in the direction of the arrow is uniformly charged by the charging means 20. Next, an electrostatic latent image is formed thereon by the exposure means 11, and this latent image is developed by the Y-color developing means 22. At this time, the developing means 23, 24, 25 for the other colors are not developed because the developing operation is canceled and only the Y color is developed. The Y-color toner image is electrostatically transferred to the intermediate transfer body 2 by the electrostatic transfer means such as the third roller 9 at the first transfer portion. Y remaining on the toner image carrier 1 without being transferred
The color toner is removed by the cleaner means 26. At the time of transferring the Y-color toner, the second roller 5 causes the solenoid 28
The pressure contact with the intermediate transfer body 2 is released by the operation of and the Y-color toner image is conveyed to the first transfer portion again while being held on the intermediate transfer body 2.

On the other hand, on the toner image carrier 1, only the developing means 23 is operated to develop the M color. The M color toner image is sent to the first transfer portion and transferred. Since the intermediate transfer body 2 rotates in synchronization with the toner image carrier 1, the M color toner image is superposed and transferred in a state in which it is highly accurately aligned with the Y color toner image that already exists. It

The same development and transfer are performed for the C and K colors, the toner images of all colors are transferred, and the toner images superposed on the intermediate transfer member 2 are transferred to the second transfer portion. Be transported. At the same time, the transfer material 4 is sent to the second transfer portion, and the second roller 5 is brought into pressure contact with the intermediate transfer member 2 immediately before the transfer and fixing of the toner image onto the transfer material 4 is started. This pressure contact is performed by releasing the operation of the solenoid 28 by the signal 29. At the second transfer portion, the heat of the heating element 8 is applied to the first roller 3 and the intermediate transfer element 2.
The toner image is supplied to the transfer material 4 and the toner image through the heat transfer medium, and the toner image is transferred and fixed to the transfer material 4 by heat and pressure.

Particularly in the case of a color image, since a thick toner image is formed, a large amount of heat is required for fixing and it is necessary to easily supply heat. As described in Embodiments 1 and 3, in the configuration of the present invention, since the intermediate transfer body 2 has a thin shell structure, the nip width at the second transfer portion can be easily increased, and the time required for heat conduction can be increased. The total heat transfer is large because it can be taken for a long time. Further, since the thickness is as thin as several hundreds of μm and it is made of a metal or a material having high thermal conductivity, the rate of heat conduction is high and the increase of the total amount of heat transfer is promoted. Further, this effect becomes remarkable during high-speed transportation. Since the heat capacity of the intermediate transfer member 2 is small, the waiting time until the heat stabilization of the apparatus can be reduced. Moreover, the rated power of the heating element 8 is small and the driving power is also small.
Furthermore, since the intermediate transfer member 2 itself has sufficient transfer fixing property even at a relatively low temperature, thermal cycle fatigue and the like are reduced, durability is improved, and device life is improved.

The present invention is not limited to the above embodiments.

[0048]

As described above, the image forming apparatus of the present invention is: 1. The toner image formed on the toner image carrier is transferred onto the intermediate transfer member at the first transfer portion, and the toner on the intermediate transfer member is transferred. In an image forming apparatus that transfers and fixes an image on a transfer material at a second transfer section, the intermediate transfer body is configured as an elastically deformable thin-walled cylindrical shape, and the second transfer section contacts the inner circumference of the intermediate transfer body. A first roller that is in contact with the heating element and a second roller that sandwiches the intermediate transfer member and faces the first roller are arranged. The transfer material is heated and pressed between the intermediate transfer member and the second roller. It is compressed and deformed into a non-circular shape by the pressing of the first transfer portion and the second transfer portion, and is rotated.

2. The toner image formed on the toner image carrier is transferred onto the intermediate transfer member at the first transfer portion, and the toner image on the intermediate transfer member is transferred onto the transfer material at the second transfer portion. In the image forming apparatus for fixing, the intermediate transfer member has conductivity or high resistance and is electrically grounded at the second transfer portion.

3. The toner image formed on the toner image bearing member is transferred onto the intermediate transfer member at the first transfer portion, the toner image on the intermediate transfer member is transferred onto the transfer material at the second transfer portion, In the image forming apparatus for fixing, the intermediate transfer member contains a filler having high thermal conductivity.

4. The toner image formed on the toner image carrier is transferred onto the intermediate transfer member at the first transfer portion, and the toner image on the intermediate transfer member is transferred onto the transfer material at the second transfer portion. In the image forming apparatus for fixing, the intermediate transfer member is formed into a thin cylindrical shape that is elastically deformable, and contacts the inner periphery of the intermediate transfer member at the first transfer portion and sandwiches the intermediate transfer member so as to face the toner image carrier. A third roller is arranged, and the intermediate transfer member is compressed and deformed into a non-circular shape by the pressure of the first transfer portion and the second transfer portion, and rotates.

5. In the above 4, in the first transfer section, the third roller has conductivity and performs electrostatic transfer.

6. In the above items 2 and 3, the intermediate transfer member is formed into a thin cylindrical shape which is elastically deformable, and the second transfer portion has a first roller which is in contact with the inner periphery of the intermediate transfer member and has a heating element. A second roller sandwiching the intermediate transfer body and facing the first roller is arranged, the transfer material is heated and pressed between the intermediate transfer body and the second roller, and the intermediate transfer body is placed between the first transfer portion and the second transfer portion. When pressed, it compressively deforms into a non-circular shape and rotates.

7. In the above items 1, 2, 3, 4, and 6, the intermediate transfer member comprises an elastic thin-walled cylindrical substrate and a surface layer having releasability.

8. In the above 7, the substrate is made of metal.

9. In the above 7, at least one of the substrate and the surface layer has conductivity.

10, the above 1, 2, 3, 4, 5, 6, 7,
At 8 and 9, toner images of a plurality of colors are formed on the intermediate transfer member.

Therefore, the following effects are obtained.

1. Since the intermediate transfer member has a thin shell structure,
It has a high self-shape retention capability, does not require a tensioning mechanism such as a tension roller, and has less deviation and meandering of the intermediate transfer member, so the device has a very simple structure and is compact and compact with few parts. It was possible to realize a device that is easy, mechanically reliable, and highly durable.

2. Since the intermediate transfer member 2 has a thin shell structure, a large nip width can be secured with a small pressure in the first transfer portion, stable and uniform contact can be obtained, and transfer efficiency is improved. .. In particular, in the thermal pressure transfer system, the temperature rise of the toner image carrier was small and the adverse effect on the photoconductor layer was also reduced.

3. Since the high temperature portion of the intermediate transfer member in the second transfer portion has a small heat capacity of the intermediate transfer member, it is sufficiently cooled until it reaches the first transfer portion again, and transfer can be performed at room temperature. Therefore, the temperature of the toner image carrier or the toner does not rise, the electrostatic latent image forming performance is not adversely affected, and the stable charging performance of high image quality is realized without deteriorating the charging performance and mechanical strength of the toner. ..

4. In the second transfer portion, the contact nip width between the intermediate transfer member and the transfer material is increased, so that sufficient heat conduction can be ensured even if the diameter of the second roller is reduced, and the second roller has a small heat capacity. Furthermore, the heat transfer capacity of the intermediate transfer member is very small because the substrate is only tens to hundreds of μm thick.
Since the thermal resistance is small, the temperature rising rate is also high. Therefore, the temperature of the second transfer portion rapidly rises to a temperature at which transfer and fixing can be performed in a few seconds by heating the heating element, and the heat-stable state is reached immediately so that the waiting time of the apparatus is shortened and a quick start is realized.

5. Since the diameter of the intermediate transfer member and the second roller can be reduced, the size and cost of the apparatus can be reduced.

6. The toner image bearing member, the intermediate transfer member, the first roller, and the second roller are pressed by a small load, so that the power required for driving rotation is small and the driving noise is low. Realized an excellent device.

7. In the first transfer portion, a large transfer nip width is ensured with a very small pressing force, so that a stable and uniform contact can be obtained. It is not necessary to use an elastic layer such as thick rubber having a thickness of several millimeters, and a fluororesin layer having a thickness of several tens of μm or a thin silicone rubber layer having a thickness of several hundreds of μm can be arranged to make Good transfer efficiency was achieved in both the transfer section. When an elastic body such as thin-walled silicone rubber is used for the surface layer 6, it is possible to improve wear resistance and thermal conductivity with additives. Therefore, the thermal resistance and heat capacity of the surface layer of the intermediate transfer member are minimized, so the waiting time from the start of heating to the transfer and fixing is further shortened,
The rated power of the heating element is also small. Therefore, the power supply capacity of the device can be reduced.

8. Further, it is possible to prevent the interface temperature between the surface layer and the substrate from becoming higher than that, to prevent thermal deformation of the surface layer and deterioration of durability due to thermal cycle, and to prevent temperature detection thermistor and transfer material separation. It has excellent wear resistance against contact with nails and the transfer material itself, improving the life of the device.

9. In the first transfer portion, a large nip width can be easily secured with a low load, the required transfer nip passage time is secured even if the transfer speed is increased, and a sufficient transfer bias voltage is applied to the toner. As a result, good transfer efficiency can be secured. Not only that, because of the low load, the hollow image due to the aggregation of the toner does not occur, and the high quality transfer is possible. further,
The transfer bias voltage can also be set lower than the discharge start voltage,
Problems such as toner explosion seen in electrostatic transfer can also be suppressed, and higher image quality and higher resolution have become possible.

10, imparting conductivity or high resistance to the intermediate transfer member or the surface layer is the transfer of the second transfer portion,
It also has a special effect during fixing. When the intermediate transfer body is electrically insulating, the intermediate transfer body and the second roller are charged to several KV by the passage of the transfer material, but when the intermediate transfer body is conductive or has high resistance and is grounded, the intermediate transfer body is transferred. The charging of the body and the second roller is reduced. In addition, even if it is not grounded, it has the effect of absorbing and uniformizing the charging of the second roller.
As a result, in the case of a positively charged toner, the electrostatic charge on the intermediate transfer member is greatly reduced, and the adsorbing force between the toner and the intermediate transfer member is reduced, so that the releasing property of the surface of the intermediate transfer member is low or the heating temperature is too high. Even when the toner adheres to the intermediate transfer member, there is no offset phenomenon in which the toner is not transferred and fixed on the transfer material, and the toner adheres to the toner image carrier due to the rotation of the intermediate transfer member or is transferred and fixed again on the next transfer material. A good fixing characteristic was realized without image deterioration due to the adherence to the second roller and the back surface of the transfer material being soiled. Also,
If the intermediate transfer member is a negatively charged toner and has conductivity or high resistance and is not grounded, the second roller will be strongly charged to the negative polarity as the transfer material passes, but both will contact each other while there is no transfer material. Then, the negative charge of the second roller moves to the intermediate transfer body.
Therefore, both the intermediate transfer member and the toner were negatively charged, and the repulsive force suppressed the offset phenomenon. Further, due to the electrostatic force and offset force, the transfer material is less likely to be wound around the intermediate transfer body 2 and the second roller, and stable transfer fixing and transfer of the transfer material without paper jams or the like are possible.

11. The thermal conductivity of the intermediate transfer member is remarkably improved by adding an appropriate amount of the high thermal conductive filler to the substrate or surface layer of the intermediate transfer member of one layer or the intermediate transfer member consisting of a plurality of layers. However, since it is a thin shell with a thickness of several tens of μm to several hundreds of μm and both the thermal resistance and the thermal capacity are remarkably small, the improvement effect explained in 7 is further promoted, and the waiting time of the apparatus until the thermal stable state is reached is further enhanced. We have realized a compact, long-life device with short power consumption, low power consumption, and sufficient transfer strength without offset and fixing strength.

12. Since the intermediate transfer member is thin, the heat resistance and heat capacity are small, the surface layer has good releasability, and the fluororesin having excellent abrasion resistance and stable surface smoothness is used. Since good heat conduction can be realized, the releasing property from the toner is good, the transfer efficiency at the time of transfer fixing is high, and the offset phenomenon in which the toner remains on the intermediate transfer member is prevented. Therefore, due to the rotation of the intermediate transfer member, the toner adheres to the toner carrier, is again transferred and fixed to the next transfer material, or adheres to the second roller to stain the back surface of the transfer material to deteriorate the image. There is no. In addition, since the heat capacity is small, the temperature of the intermediate transfer member is sufficiently lowered after the transfer and fixing. Therefore, there is no softening of the toner, and in the case of contact type transfer, the toner is firmly attached to the toner image bearing member by the contact pressure, and cleaning failure does not occur. Therefore, it is possible to prevent a fatal defect of the device such as continuous occurrence of image defects of a plurality of sheets after the offset, replacement of the toner image carrier, replacement of the cleaning means, etc., and a highly reliable device is realized. did it.

It is particularly effective if the image forming apparatus of the present invention is applied to a printer, a video printer, a facsimile, a copying machine or the like.

[Brief description of drawings]

FIG. 1 is a main schematic view of a first image forming apparatus according to the present invention.

FIG. 2 is a schematic diagram of an image forming apparatus using a conventional roller intermediate transfer member.

FIG. 3 is an explanatory diagram of an intermediate transfer member of the image forming apparatus of the present invention.

FIG. 4 is a main schematic diagram of a second image forming apparatus according to the present invention.

FIG. 5 is a main schematic diagram of a fourth image forming apparatus according to the present invention.

[Explanation of symbols]

 1 toner image carrier 2 intermediate transfer member 3 first roller 4 transfer material 5 second roller 6 surface layer 7 substrate 8 heating element 9 third roller 10, 20 charging means 11 exposure means 12, 22, 23, 24, 25 development Means 13 and 26 Cleaning means 27 Spring 28 Solenoid 29 Signal 30 Lever 31 Support point 51 Surface layer 52 Roller base 53 Drum-shaped intermediate transfer member

Claims (10)

[Claims] 1. A toner image formed on a toner image carrier 1 is transferred onto an intermediate transfer member 2 at a first transfer portion, and the toner image on the intermediate transfer member 2 is transferred onto a transfer material at a second transfer portion. In the image forming apparatus for transferring and fixing the image onto
Is configured as an elastically deformable thin-walled cylindrical shape, the first transfer roller 3 having a heating element 8 in contact with the inner periphery of the intermediate transfer member 2 at the second transfer portion, and the second roller sandwiching the intermediate transfer member 2 therebetween. A second roller 5 facing the one roller 3 is disposed, the transfer material 4 is heated and pressed between the intermediate transfer body 2 and the second roller 5, and the intermediate transfer body 2 is connected to the first transfer portion. An image forming apparatus, which is compressed and deformed into a non-circular shape by the pressing of the second transfer portion and is rotated. 2. A toner image formed on a toner image carrier 1 is transferred onto an intermediate transfer member 2 at a first transfer portion, and the toner image on the intermediate transfer member 2 is transferred onto a transfer material at a second transfer portion. In the image forming apparatus for transferring and fixing the image onto
Is electrically conductive or has high resistance, and is electrically grounded at the second transfer portion. 3. A toner image formed on a toner image carrier 1 is transferred onto an intermediate transfer member 2 at a first transfer portion, and the toner image on the intermediate transfer member 2 is transferred at a second transfer portion. In the image forming apparatus for transferring and fixing the image onto
Is an image forming apparatus characterized by containing a filler having high thermal conductivity. 4. A toner image formed on a toner image carrier 1 is transferred onto an intermediate transfer member 2 at a first transfer portion, and the toner image on the intermediate transfer member 2 is transferred onto a transfer material at a second transfer portion. In the image forming apparatus for transferring and fixing the image onto
Is a thin-walled cylinder that is elastically deformable. The third roller is in contact with the inner periphery of the intermediate transfer body 2 at the first transfer portion and sandwiches the intermediate transfer body 2 and faces the toner image carrier 1. 9 is arranged, and the intermediate transfer member 2 is compressed and deformed into a non-circular shape by the pressing of the first transfer portion and the second transfer portion, and is rotated. 5. The third roller 9 at the first transfer portion.
The image forming apparatus according to claim 4, wherein the image forming apparatus has conductivity and performs electrostatic transfer. 6. The intermediate transfer body 2 is formed into a thin cylindrical shape that is elastically deformable, and the second transfer portion has a first roller 3 that is in contact with an inner circumference of the intermediate transfer body 2 and has a heating element 8. A second roller 5 is disposed to face the first roller 3 with the intermediate transfer body 2 sandwiched therebetween. The transfer material 4 is heated and pressed between the intermediate transfer body 2 and the second roller 5, The image forming apparatus according to claim 2 or 3, wherein the transfer body 2 is compressed and deformed into a non-circular shape by the pressure of the first transfer portion and the second transfer portion, and is rotated. 7. The intermediate transfer member 2 comprises an elastic thin-walled cylindrical substrate 7 and a surface layer 6 having releasability, claim 1, claim 2, claim 3, claim 4. Or the image forming apparatus according to claim 6. 8. The image forming apparatus according to claim 7, wherein the base 7 is made of metal. 9. The image forming apparatus according to claim 7, wherein at least one of the substrate 7 and the surface layer 6 has conductivity. 10. A toner image of a plurality of colors is formed on the intermediate transfer member 2, claim 1, claim 2, claim 3, claim 4, claim 5, claim 6, claim 6. The image forming apparatus according to claim 7, claim 8 or claim 9.