JPH0844220A - Image forming device - Google Patents

Abstract

(57) [Summary] [Purpose] Toner images of a plurality of colors formed on an image carrier are sequentially transferred to an intermediate transfer member, and then the toner images on the intermediate transfer member are thermally collectively transferred onto a transfer material. In an image forming apparatus for transferring and fixing, a problem that an intermediate transfer member portion heated in the transferring and fixing unit comes into contact with the image carrier again and heats the image carrier and a developing device and the like around the image carrier is solved. [Structure] Toner images of a plurality of colors are sequentially formed on an image carrier (1), and the toner images are electrostatically superposed on an intermediate transfer member (8) made of a heat-resistant film having a high releasability. The primary transfer portion for transferring and the toner images of a plurality of colors formed on these intermediate transfer bodies are thermally collectively transferred from the intermediate transfer body to the transfer material (P) by the heating means (9) arranged on the back surface of the film. In an image forming apparatus having a secondary transfer portion for transferring and fixing by transfer, a cooling means (86) for the intermediate transfer body is provided around or inside the intermediate transfer body, so that the heated intermediate transfer body transfers the image to the image carrier. Prevent thermal effects of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus, in which toner images of a plurality of colors are sequentially transferred from an image carrier to an intermediate transfer member and then collectively transferred from the intermediate transfer member to a transfer material. The present invention relates to a fixing image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, there are the following techniques for transferring a multicolor toner image using an intermediate transfer member.

1) According to Japanese Patent Publication No. 49-209,
A technique is disclosed in which electrostatic transfer is performed in the primary transfer and pressure transfer is performed in the secondary transfer. This is a cloth,
When multicolor printing is performed on a flexible material having elasticity such as paper, it is an improvement of the so-called color shift in which an image shifts when transferring each color in an overlapping manner.

That is, the purpose and effect are to transfer each color image to an intermediate blanket drum and transfer them all at once to reduce color misregistration and to print high-speed multicolor.

2) Japanese Patent Laid-Open No. 50-23234 discloses that
It is disclosed that the secondary transfer portion has a pressing / heating means. That is, when the transfer process and the fixing process are separated, paper dust or the like adversely affects the photosensitive drum in the transfer process.

At the time of fixing, the thermal efficiency is poor.

An image is disturbed during the transfer of the transfer material carrying the toner from the transfer section to the fixing section.

This is an improvement of the above drawbacks.

The purpose and effect of the present invention is to transfer and fix the toner image formed on the surface of the photoconductor to the transfer material as a faithful and clear image.

3) Japanese Unexamined Patent Publication No. 59-12576 discloses that
It is disclosed that primary transfer is performed by pressure and transfer and fixing are performed by secondary transfer.

This is because registration is difficult when multiple transfer is performed on the same transfer material, and the transfer material does not have sufficient force to hold the toner image to be transferred, so that the transfer material is being conveyed during the next transfer. In addition, it is an improvement in that the toner image is peeled off.

In this technique, since each toner image is transferred onto the intermediate transfer member, it is easy to obtain the transfer position alignment accuracy of each toner image onto the intermediate transfer material, and a high quality image is always reproduced with good reproducibility. Can be formed on the transfer material.

Further, since each toner image is further transferred to the next transfer material after the transfer of each toner image to the intermediate transfer member, the synchronization allowance becomes large especially when the transfer material is transferred, and the transfer mechanism can be simplified and reliability is improved. Also improves.

Further, since the intermediate transfer member has a transfer layer (especially rubber type) capable of strongly holding the transferred toner image, it has excellent transfer characteristics.

The following are known techniques for simultaneous transfer and fixing.

1) Japanese Patent Laid-Open No. 49-78559 discloses that
The surface energy (adhesive force), hardness, and heat quantity of the intermediate transfer material are specified.

2) JP-A-57-23975 and JP-A-59-50473 disclose intermediate transfer layers containing addition polymerization type silicone rubber.

The addition-polymerization type silicone rubber has few unreacted parts and leached parts, so that the photosensitive layer is less contaminated and the transfer layer is excellent in film strength and processability, and a good image can be obtained.

3) JP-A-59-139070 discloses that primary transfer is performed by electrostatic transfer and pressure fixing is performed by secondary transfer. The object of the invention is to provide an apparatus which can obtain a good copy image even in plain paper copying using a low-resistance magnetic toner and in high humidity, and which can be easily made compact.

4) Japanese Patent Laid-Open No. 62-293270 discloses that the intermediate transfer member has a transfer layer of silicon rubber on a polyamide fiber woven fabric substrate. here,
Since polyamide fiber woven cloth is used as the base material of the intermediate transfer material, it is flexible and has good adhesion to the image carrier and the transfer material, thus improving transfer efficiency. It is said that the adhesiveness is good and the endless belt can be easily formed.

As described above, many examples of the intermediate transfer member and the example of simultaneous transfer and fixing in the case of a multicolor toner image have been proposed.

In many cases of monochromatic image forming means, an intermediate transfer member having adhesiveness and releasability is used.
There is a system in which the toner image on the photosensitive drum is once adhesively transferred onto an intermediate transfer member, and then the intermediate transfer member is fused and fixed on the transfer material. In the primary transfer portion, which is an adhesive transfer, the intermediate transfer body made of silicon rubber and the photosensitive drum are brought into pressure contact with each other, and the toner image is adhered onto the intermediate transfer body by adhesiveness. Next, in the secondary transfer portion which is the melt transfer, the heat roller and the intermediate transfer body are pressed against each other, and the toner image is heated and melted by the heat roller via the transfer material. The melted toner penetrates into the fibers of the transfer material due to the pressure. At the same time, due to the releasability of the intermediate transfer body, the intermediate transfer body is peeled off.

In the case of multicolor image forming means, it is difficult to use adhesive transfer at the primary transfer portion, and therefore, there are many cases where electrostatic transfer is used. Simultaneous transfer fixing device
The transfer efficiency of electrostatic transfer is relatively low at 80 to 90%,
It has been proposed to solve the problems that the transfer efficiency is affected by the resistance / capacitance change due to the change of the water content of the transfer material, and the scattering is caused.

Further, as a device for preventing color misregistration and color unevenness in a conventional multicolor image forming apparatus using an intermediate transfer member, for example, as described in JP-A-57-673, Some are designed to prevent meandering.

Further, as an example of successfully maintaining the accurate resist control required for full color machines with each color multiplex using relatively inexpensive components, US Pat. No. 4,65.
No. 2,115 and No. 4,788,572, which use a method of synchronizing the photosensitive belt and the intermediate transfer belt.

As a multi-color image forming apparatus using these intermediate transfer bodies, for example, a multi-transfer type copying apparatus, a document is CC-printed.
After being read by a D-line sensor or the like, the image signal that has been subjected to various kinds of processing and the image signal directly output from the computer are output to the laser driver, and the laser is driven to perform laser exposure so that the laser light is evenly distributed in advance. A latent image is formed on the charged photoreceptor. Next, this latent image is developed with the toner in the developing device for the first color, and then the toner image is electrostatically transferred from the photosensitive member to the intermediate transfer member in the primary transfer portion. These series of steps are sequentially repeated with, for example, yellow, magenta, cyan, and black toners to form a full-color toner image on the intermediate transfer member,
In the secondary transfer portion, these full-color toner images are thermally transferred from the intermediate transfer member to the transfer material (for example, paper) all together at the same time and fixed, and the sequence of full-color image formation is completed. And the required full-color image formation is completed.

[0027]

However, after the toner images of the respective colors are formed on the intermediate transfer member as described above, they are thermally transferred from the intermediate transfer member to the transfer material at the same time by thermal transfer at the secondary transfer portion. As a result, the following problems occur when a full-color image is formed.

(1) In the case where the secondary transfer portion is thermally thermally transferred from the intermediate transfer member to the transfer material (for example, paper) at the same time, the heated portion of the intermediate transfer member reaches the contact position with the photosensitive member. The temperature of the photoconductor is raised by being conveyed. As a result of this temperature rise of the photoconductor, the charging characteristics, the photosensitivity characteristics, etc. of the photoconductor change, so that image stabilization is difficult.

(2) Around the photosensitive member, a developing device for accommodating the toner and the toner remaining on the surface of the photosensitive member by the primary transfer from the photosensitive member to the intermediate are cleaned from the surface of the photosensitive member to accommodate the waste toner. Cleaners etc. are arranged.
As described above, these toners are powders having a volume average particle diameter of about 1 to 20 μm, which are made of a thermoplastic resin having a glass transition temperature (Tg) of about 45 to 75 ° C., because they are thermally fixed to the transfer material. Therefore, when heated to Tg or higher, so-called blocking, which is agglomeration of powder, and fusion to the surface of the photoreceptor, the developing container, the cleaning means, etc. occur.

As these cooling means, a device has been proposed in which the surface of the intermediate transfer member is cooled by blowing air with a fan or the like, or a cooling roller is provided in the intermediate transfer member.

However, if the blower cooling is performed on the toner images of a plurality of colors sequentially formed on the surface of the intermediate body by the fan as in the former case, the toner images may be disturbed.

Further, regarding the cooling roller, the contact area with the intermediate body is relatively small, the cooling efficiency is poor, and heat is trapped inside the intermediate transfer body.

Therefore, it is an object of the present invention to provide an image forming apparatus which solves the problems associated with the temperature rise of these intermediates and is capable of stable image output.

[0034]

The above object can be achieved by an image forming apparatus according to the present invention.

In summary, the present invention sequentially forms toner images of a plurality of colors on an image carrier and electrostatically sequentially forms the toner images on an intermediate transfer member made of a heat-resistant film having a highly releasable surface. A primary transfer portion that is transferred in an overlapping manner, and a plurality of color toner images formed on these intermediate transfer bodies are thermally transferred and fixed from the intermediate transfer body to the transfer material all at once by a heating means provided on the back surface of the film. In an image forming apparatus having a secondary transfer portion, this is achieved by disposing a cooling means for the intermediate transfer body around or inside the intermediate transfer body.

Further, as these cooling means, at least one of a blower fan, a cooling roller, a heat radiating plate, a heat pipe, etc. is effectively arranged inside the intermediate transfer member.

Further, in a system in which the toner image primarily transferred onto the intermediate transfer member is presumably attached on the intermediate member by heating the heating device when passing through the secondary transfer portion, the system of blowing means This is achieved by disposing such a non-contact cooling means at a position for directly blowing air to the toner image after passing through the secondary transfer portion.

[0038]

【Example】

 (Embodiment 1) Hereinafter, an embodiment of the present invention will be described in detail.

FIG. 1 is a block diagram showing an embodiment of a full-color image forming apparatus to which the present invention is applied.

The photoconductor drum 1 as an image carrier is made of a photoconductor such as OPC or a-Si, and the periphery of the photoconductor drum 1 is irradiated with a pre-exposure lamp 7, a corona charger 2, and a laser beam corresponding to each color signal. An exposure unit including a laser scanner 3, a mirror 4 and the like, a rotary developing unit 5 having four developing units for respectively containing yellow, magenta, cyan, and black toners, an intermediate transfer member 8, and a cleaning unit 6.
Etc. are arranged. A pressure roller 9 is disposed above the intermediate transfer member 8 so that it can be brought into contact with and separated from the pressure roller 9.

The sequence of the entire image forming apparatus having the above configuration will be briefly described as follows.

That is, when the photosensitive drum 1 rotates in the direction of the arrow and is uniformly charged by the primary charger 2, image exposure is performed by the laser beam E pulse-width modulated according to the yellow image signal of the original. , An electrostatic latent image of a yellow image is formed on the photosensitive drum 1. The electrostatic latent image of the yellow image is developed by the yellow developing device 5Y which is previously set at the developing position by the rotation of the rotary developing device 5.
At this time, the developing bias applied to the developing sleeve of the yellow developing device 5Y is such that the alternating voltage value Vpp is 2 kV and the rectangular wave alternating voltage having the frequency f of 2 kHz is VDC = 400 v.

Further, the toner in the developing device, which has been consumed by the development, is replenished from the toner hopper 51.

This yellow image is electrostatically transferred onto the film 80 of the intermediate transfer member 8 at the primary transfer portion X which is the contact portion between the photosensitive drum 1 and the intermediate transfer member 8. Here, the film 80 of the intermediate transfer member 8 is rotating in the direction of the arrow in synchronization with the photosensitive drum 1, and continues to rotate while holding the yellow toner image on the surface, and the next color (in FIG. Prepare for transfer of magenta).

On the other hand, the surface of the photosensitive drum 1 is cleaned by the cleaning means 6 and then uniformly charged again by the primary charger 2, and is subjected to image exposure according to the next magenta image signal.

The rotary developing device 5 rotates while the electrostatic latent image is formed on the photosensitive drum 1 according to the image signal of magenta by the image exposure described above, and the magenta developing device 5M is fixed at the developing position. , Perform predetermined magenta development.
This magenta toner image is transferred onto the film 80 at the primary transfer portion.

Subsequently, the above-described process is carried out for the cyan color and the black color, respectively, and the transfer of the four colors to the intermediate transfer member is completed or during the transfer of the final color black, the paper feeding unit 100 The paper P, which is the transfer material accommodated in, is fed by the paper feed roller 101 and conveyed to the secondary transfer portion Y of the intermediate transfer body via the registration rollers 102, 103 and the paper feed guide 104.

Here, four layers formed in multiple on the intermediate transfer member.
The color toner visible image is transferred and fixed onto the paper at the same time by the heat of the heating body 83 arranged in the intermediate transfer body 8 and the pressure of the pressure roller 9 which is brought into contact with the paper P as it is conveyed. The sheet is discharged onto the discharge tray 107 through the discharge rollers 105 and 106, and the full-color image formation on the paper is completed.

After that, the toner resin remaining on the surface of the film 80 of the intermediate transfer member is cleaned by bringing the intermediate transfer member cleaning means 84 such as a felt pad into contact therewith, and the film 80 heated is heated.
Is cooled to 40 ° C. or less by contact with the driven roller 82 and a blower fan or a cooling fan which is a cooling means arranged inside the intermediate transfer member 8 to prepare for the next step.

Here, the blower fan 86 has a structure such as a sirocco fan so as to blow the film 80 over the entire area in the longitudinal direction, but a conventionally known propeller fan may be used instead. Not limited. It is also effective to arrange a plurality of these.

In this structure, the air blowing position is between the driving roller 81 and the driven roller 82, but it is between the heating body 83 and the driven roller 82, or between the heating body 83 and the driving roller 81.
Any position may be used as long as it is inside the intermediate body such as the inside of the space film 80.

Further, as shown in FIG. 3, the air can be sent to the driving roller 81, the driven roller 82, the heating body 83 and the like simultaneously with the film 80.

Next, the intermediate transfer member 8 of this embodiment used in the image forming apparatus will be described with reference to FIG.

FIG. 2 is a schematic diagram of an intermediate transfer member using an endless belt type film material.

Numeral 80 is an endless belt type thin film heat resistant film material as described above, the construction of which will be described later.

Reference numeral 81 is a film driving roller which also serves as a transfer roller, 82 is a driven roller which also serves as a film expanding roller, and 83 is a heating body (thermal heater). The drive roller 81, the driven roller 82, and the heating body 83 are arranged substantially parallel to each other, and the film 80 is suspended and stretched between these three members. Here, the driven roller 82 may be the driving roller.

Both ends of the driving roller 81 and the driven roller 82 are rotatably supported between bearing members (not shown). The heating body 83 is a stationary member fixedly supported by an immovable member (not shown). The drive roller 81 is rotationally driven clockwise in the drawing by a drive system (not shown),
A conveyance force is applied to the film 80 by the frictional force between the outer peripheral surface of the drive roller 81 and the inner surface of the film as the drive roller 81 is driven to rotate, and the inner surface of the film slides on the heating surface of the heating body 83 while being driven by the drive roller 81. Roller 82, heating element 8
3 between the three members in the clockwise direction on the drawing, and the transfer speed of the transfer paper P as the material to be heated (50 mm / s in this embodiment).
It is rotationally driven at the same peripheral speed as ec).

Since the driving roller 81 of this embodiment also serves as a transfer roller, a cored bar made of a conductive rigid material such as metal, polyurethane, EPDM (ethylene propylene dimethyl rubber), polyisoprene, butadiene-styrene copolymer is used. , Polybutadiene, isobutylene-isoprene copolymer, butadiene-acrylonitrile copolymer, ethylene-propylene copolymer, chlorosulfonated polyethylene, acrylic ester copolymer, organic polysiloxane, perfluoropropene, vinylidene fluoride copolymer Conductive particles such as carbon are dispersed in a rubber elastic member such as, and the volume resistance RV is adjusted to 10 ⁵ to 10 ¹⁰ Ωcm and the Asker C hardness is adjusted to ^{10 to} 65 degrees, preferably 20 to 50 degrees. Structure or elastic layer formed of rubber elastic body It is.

In this example, with emphasis on heat resistance, conductive particles were dispersed in a rubber elastic body having heat resistance such as silicone rubber to obtain a volume resistance of 10 ⁷ to 10 ⁹ Ωcm and Asker C.
It has a hardness of 40 to 50 degrees, an outer diameter of 30 mm, and a 7 mm thick silicone rubber single layer.

The contact pressure with the photosensitive drum 1 is 10 g to 2 kgf, preferably 0.3 to 1 kgf with the film 80 being sandwiched.

A bias of 1 to 2 kV is applied from the transfer bias power source 85 to the core of the drive roller 81, which is the transfer roller. This bias gradually increases according to the order of stacking the toner, and is set to 1 kV for the first color, 1.5 kV for the second color, 2 kV for the third color, and 2.5 kV for the fourth color. Also, when there is only a single color, 1k as in the first color.
It becomes V. These transfer biases are controlled by a constant voltage or a constant current. As for this transfer bias,
Although only direct current is used in this embodiment, an alternating current component may be superimposed.

Reference numeral 84 is a felt pad that contacts the outer surface of the film material 80 and is impregnated with a release agent such as silicone oil for cleaning and supplying oil.

The heating element 83 is a low heat capacity linear heating element having a longitudinal direction in the axial direction of the film 80 (direction orthogonal to the rotational movement direction of the film, hereinafter referred to as film width direction).

In this embodiment, a heater base 83a, an electric heating element layer 83b formed in a strip shape or a linear shape along the longitudinal direction at the substantially central portion of the upper surface of the substrate, and the electric heating element layer 83b. And a substrate 83a, which is a heat-resistant glass 83c which is a surface protective layer having a thickness of about 10 μm coated on the upper surface of the substrate including
The temperature measuring element 83d provided on the lower surface of the substrate and the heater support 83e that heat-insulates and supports this substrate.

The heater substrate 83a is a member having heat resistance, insulating properties, and low heat capacity, and as an example, the thickness is 1 mm and the width is 5 to 1.
It is an alumina substrate having a length of 0 mm and a length of 310 mm.

The heating element layer 83b is, for example, a coating layer made of an electric resistance material such as Ag / Pd (silver palladium) .Ta ₂ N and having a thickness of about 10 μm and a width of 1 to 3 mm formed by screen printing or the like. .

The temperature detecting element 83d is, for example, bonded to the lower surface of the substrate with a resistance thermometer having a low heat capacity such as a Pt film coated by screen printing or the like, and to the approximate center of the lower surface of the substrate with a silicone adhesive having good thermal conductivity. It is a low heat capacity NTC thermistor.

The heater support 83e is the heaters 83a-83.
Insulates and supports d with respect to the entire fixing device and copying device, and has high heat resistance, high heat resistance, and rigidity, for example, high heat resistant resin such as polyphenylene sulfide, polyamide imide, polyimide, polyether ether ketone, liquid crystal polymer, etc. Or a composite material of these resins and ceramics, metal, glass or the like.

The temperature control of these heating elements is controlled so that the paper P as the transfer material reaches a predetermined temperature immediately before passing through the second transfer portion Y, and the current is stopped immediately after passing each to increase the temperature of the intermediate transfer element and the surrounding area. It is preferable to prevent it.

Here, the energization is, for example, a pulsed waveform with a cycle of 20 ms of 100 V DC, and a pulse according to a desired temperature and energy release amount controlled by the temperature measuring element 83d is given with its pulse width varied. In general, the pulse width is 0.5 to 5 ms. Alternatively, AC100V
Then, the energization power is controlled by controlling the energizing phase angle by the energization control circuit (not shown) including the triac according to the heater substrate detection temperature of the temperature detecting element 83d.

In the heating element 83, the heat capacity of the heater substrate 83a, the heating element layer 83b, the surface protective layer 83c, and the temperature detecting element 83d is small, and this is insulated by the support element 83e. The temperature reaches a temperature at which the toner layer on the film 80 and the transfer paper P can be fixed in a short time (quick start property), and there is no need for standby temperature control in which the heating body 83 is previously energized to generate heat, and energy can be saved. At the same time, it is possible to prevent the temperature inside the intermediate transfer body and the photosensitive drum 1 and the like around the intermediate transfer body from rising.

The film material 80 is not limited to the endless belt shape, but is a long film having a roller winding and having an end, and is made to run at a predetermined speed from the feeding shaft to the winding shaft via the heating body. Can also be used as the intermediate transfer member.

The pressure roller 9 has a highly releasable skin layer such as PFA or PTFE formed on a heat-resistant rubber elastic body such as silicone rubber, like the pressure roller in a general fixing device. Then, this is brought into contact with and separated from the heating surface of the heating body 83 so as to sandwich the film 80.

The timing of this contact / separation is to prevent the toner images transferred on the film 80 from being offset to the pressure roller 9 by the film 8 at the first transfer portion X.
After forming the fourth color toner image (here, black, which is the final color) on 0, the paper P, which is just before passing through the second transfer portion Y or is a transfer material, is fed by the feed roller 101, and the registration roller 102, Immediately before being conveyed to the second transfer portion Y of the intermediate transfer body via 103 and the paper feed guide 104, the heating body 83 is sandwiched by the contact force of 2 to 20 kgf, preferably 4 to 8 kgf. The film 80 is pressed against the upper surface, and the film 80 is rotated in the forward direction along with the rotational speed of the film 80 at substantially the same speed as the film speed.

FIG. 4 is a schematic cross-sectional view of the layer structure showing an embodiment of the film 80 according to the present invention, in which 80a is a heat resistant resin as a base layer (base film) of the film,
High heat resistance of polyester, PET (polyethylene terephthalate), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyphenylene sulfide, polyamide imide, polyimide, polyether ether ketone, liquid crystal polymer, etc. Resin, a metal sheet of aluminum, nickel, or the like, or a composite material of these and ceramics, metal, glass, or the like.

Reference numeral 80b is a high release layer having a heat resistance of, for example, 5 μm, such as PET and P similar to the above-mentioned base layer.
A fluororesin such as FA or PTFE, a fluororubber, a silicone resin or a silicone rubber is used.

Further, as a more preferable film structure, these heat-resistant sheets have a relatively low resistance layer, and the volume resistance RV equivalent to that of the driving roller 81 is obtained.
Is 10 ⁵ to 10 ¹⁰ Ωcm.

These films 80 have a total thickness of 100 μm or less, preferably 40 μm or less. In this embodiment, the base layer (base film) 8 of the film 80 is used.
0a is a polyimide film of 20 μm layer, and high release layer 80b is 5 μm, which has a low resistance due to carbon dispersion.
An m-thick PFA layer is applied.

Since the film 80 has a particularly excellent releasability as in this constitution, the transfer efficiency to the transfer material in the secondary transfer is close to 100%.

In the present embodiment, the drum-shaped photoconductor has been described, but if it is applied to a belt-shaped photoconductor, it is more effective in terms of the contact state between the photoconductor and the intermediate transfer member. Needless to say.

In this embodiment, a semiconductor laser system is used as the latent image forming means, but the invention is not limited to this, and the latent image forming means may be a digital latent image forming means such as an LED, a liquid crystal, or ionography, and the reader 2. It is also effective in a so-called analog latent image forming means in which an image signal is directly formed on the photoconductor as light without using such an image reading means.

In this embodiment, a full-color image forming apparatus having a four-color developing system has been described, but it goes without saying that it can be applied to a single-color or plural-color image forming apparatus.

As described above, in this structure, the cooling efficiency of the intermediate transfer member is high, the problem associated with the temperature rise of the intermediate member can be solved, and stable full-color image output can be performed. Also,
Since the cooling means is arranged inside the intermediate body, the size of the apparatus including the intermediate transfer body can be simplified.

(Embodiment 2) In Embodiment 1, cooling was performed by the blower fan 86, but in this embodiment of FIG. 5, the heat dissipation plate 87 is brought into contact with the film 80 in the longitudinal direction,
It was used as a cooling means.

The heat radiating plate 87 is a plate-shaped member made of a metal having a high thermal conductivity such as iron, steel, aluminum and SUS.

As these heat dissipation plates 87, a plurality of fins may be provided upright in order to expand the heat dissipation area as conventionally known.

In this embodiment, the blower fan 86 is provided for this heat radiating plate in order to enhance the cooling efficiency, but the blower fan 86 may be omitted.

Further, the heat radiating plate 87 is not limited to a flat one, and may have a curvature as shown in FIG. 6 to stretch the film 80.

Like the first embodiment, this structure has a high cooling efficiency of the intermediate transfer member, can solve the problem associated with the temperature rise of the intermediate member, and can output a stable full-color image. Further, since the cooling means is provided inside the intermediate body, the apparatus including the intermediate transfer body can be made compact and simple.

(Embodiment 3) In the structure shown in FIG. 7, the driven roller 82 is in contact with the heat absorbing portion of the heat pipe 88 and is used as a cooling means.

Here, the heat pipe 88 is fixed, the driven roller 82 circulates around this, and the heat radiating portion is arranged outside the intermediate transfer member 8 in the longitudinal direction (not shown).

Although the heat pipe 88 is arranged inside the driven roller 82 in this embodiment, it may be arranged inside the intermediate transfer member 8 by a single heat pipe.

It is more effective to dispose the heat dissipation portion of the heat pipe 88 outside the image forming apparatus.

Even with the cooling means having the above structure, the cooling efficiency of the intermediate transfer member is high, and the problem associated with the temperature rise of the intermediate member can be solved.

(Embodiment 4) FIG. 8 shows that when the toner images sequentially formed on the film 80 pass through the secondary transfer portion Y, the heating member 83 is electrically heated so that the toner images are once formed on the film. Is assumed, and the toner image is directly blown and cooled on the toner image.

As the non-contact cooling means for the hypothesized toner image, it is possible to adopt a structure in which the cooling is performed from the back side of the toner image forming surface of the film 80 as described in the first to third embodiments. It is also possible to use this configuration together with this configuration.

In this configuration, when the toner images sequentially formed on the photoconductor 1 are sequentially transferred at the primary transfer portion X on the intermediate transfer body 8, the toner images are transferred onto the intermediate transfer body 8 last time (one round before). The formed toner image is transferred to the photoconductor 1 again,
So-called retransfer occurs, and a toner image transferred earlier has a smaller amount of toner transferred in the initial stage, thereby eliminating the problem that the image quality deteriorates.

Further, since the cooling means is also non-contact, there is no offset from the intermediate transfer member to the cooling roller by, for example, bringing the cooling roller into contact with the toner image.

[0099]

As described above, according to the present invention, toner images of a plurality of colors are sequentially formed on an image carrier, and electrostatically transferred onto an intermediate transfer member made of a heat-resistant film having a highly releasable surface. The primary transfer portion for sequentially superimposing the toner images on the intermediate transfer member and the toner images of a plurality of colors formed on these intermediate transfer members are thermally transferred from the intermediate transfer member to the transfer material by the heating means provided on the back surface of the film. In an image forming apparatus having a secondary transfer unit for transferring and fixing all at once, at least one of a blower fan, a cooling roller, a heat radiating plate, a heat pipe, etc. is provided around or inside the intermediate transfer body as a cooling means for the intermediate transfer body. By disposing the intermediate transfer member, the cooling efficiency of the intermediate transfer member is high, the problem associated with the temperature rise of the intermediate transfer member can be solved, and stable full-color image output can be performed.

Further, since the cooling means is provided inside the intermediate body, the apparatus including the intermediate transfer body can be downsized and simplified.

Further, in a device in which the toner image primarily transferred onto the intermediate transfer member is presumably attached to the intermediate transfer member by heating the heating means when the toner image passes through the secondary transfer portion, air is blown. By arranging a non-contact cooling means such as a means at a position where the toner image after passing through the secondary transfer portion is directly blown, the cooling efficiency of the toner image assumed not only on the intermediate transfer body but also on the intermediate transfer body is cooled. Since it is also high, the problem that the melted toner adheres to the surface of the photoconductor can be solved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is an enlarged view of an intermediate transfer member used in an embodiment of the image forming apparatus of the present invention.

FIG. 3 is an enlarged view of another example of the intermediate transfer member used in one embodiment of the image forming apparatus of the present invention.

FIG. 4 is an enlarged side view of a film used for an intermediate transfer member used in the image forming apparatus of the present invention.

FIG. 5 is a schematic configuration diagram showing a second embodiment of the image forming apparatus of the invention.

FIG. 6 is a schematic configuration diagram showing another example of the heat dissipation plate in the second embodiment of the image forming apparatus of the present invention.

FIG. 7 is a schematic configuration diagram showing a third embodiment of the image forming apparatus of the invention.

FIG. 8 is a schematic configuration diagram showing a fourth embodiment of the image forming apparatus of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 2 ... Charging device 3 ... Laser scanner 4 ... Mirror 5 ... Rotating developing device 6 ... Cleaner unit 7 ... Pre-exposure lamp 8 ... Intermediate transfer body 80 ... Film 81 ... Driving roller 82 ... Followed roller 83 ... Heating body 84 ... Cleaning member 85 ... Transfer bias power supply 86 ... Cooling fan 87 ... Radiating plate 88 ... Heat pipe 9 ... Pressure roller 100 ... Paper feeding unit

Claims (7)

[Claims] 1. A primary method in which toner images of a plurality of colors are sequentially formed on an image carrier, and the toner images are electrostatically superposed and sequentially transferred onto an intermediate transfer member made of a heat-resistant film having a highly releasable surface. A transfer unit and a secondary transfer unit that thermally transfers and fixes the toner images of a plurality of colors formed on these intermediate transfer members to the transfer material collectively from the intermediate transfer member by a heating means provided on the back surface of the film. An image forming apparatus having the image forming apparatus, wherein cooling means for the intermediate transfer body is arranged around or inside the intermediate transfer body. 2. The image forming apparatus according to claim 1, wherein the cooling unit is a fan. 3. The image forming apparatus according to claim 1, wherein the cooling means is a heat dissipation plate. 4. The cooling means is a heat pipe.
The image forming apparatus according to item 1. 5. The image forming apparatus according to claim 2, wherein the cooling unit is provided inside the intermediate transfer member. 6. A primary method in which toner images of a plurality of colors are sequentially formed on an image carrier, and the toner images are electrostatically superposed and sequentially transferred onto an intermediate transfer member made of a heat-resistant film having a highly releasable surface. A transfer unit and a secondary transfer unit that thermally transfers and fixes the toner images of a plurality of colors formed on these intermediate transfer members to the transfer material collectively from the intermediate transfer member by a heating means provided on the back surface of the film. As a cooling means of the image forming apparatus, which has a toner image transferred at the primary transfer portion and which is thermally post-fixed on the heat-resistant film sequentially when passing through the secondary transfer portion, and simultaneously fixed to the transfer material at the same time, The image forming apparatus according to claim 1, wherein a fan is arranged at a position where the toner image after passing through the secondary transfer portion is directly blown. 7. The image forming apparatus according to claim 4, wherein the heat pipe also serves as a driving unit or an expanding unit of the intermediate transfer member or is arranged inside thereof.