JPH0823720B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus for electrostatically forming an image, such as an electrophotographic copying machine and the same printer.

(Problems to be Solved by Prior Art) A photoconductor having a photoconductive layer on its surface is uniformly charged with a specific polarity, and an optical image is projected on the photoconductive layer by an appropriate image signal writing means. An electrostatic latent image is formed, and then a fine-grained toner having a polarity opposite to that of the latent image is electrostatically imparted to the toner image to form a toner image. Contacting or approaching a sheet-shaped transfer material, applying an electric charge having a polarity opposite to that of the toner to the transfer material to electrostatically transfer the toner image to the transfer material, and further bringing this transfer material to a fixing portion, An image forming apparatus configured to apply pressure or heat and pressure to fix and fix a toner image on a transfer material has been widely used in the past.

For example, as shown in JP-A-55-134872 or US Pat. No. 4,195,927, a transfer means using pressure has been proposed.

Further, as seen in U.S. Pat.Nos. 3,013,878 and 3,669,706, the latent image formed on the photoconductor is visualized and then transferred to an intermediate transfer member having a silicone rubber layer. It has been proposed to transfer a transfer image by applying heat and pressure to the transfer material. In the apparatus having the above-described configuration example, it is necessary that the front end of the transfer image on the intermediate transfer material comes on the nip of the pressing body at the same time in synchronization with the front end of the transfer material. In the conventional device, when the front end of the transfer image on the intermediate transfer material comes to the nip portion with the pressure body, the visible image on the surface of the photoreceptor, which corresponds to the rear end portion of the transfer image, is still transferred to the intermediate transfer material. During transfer, the visible image on the nip part with the photoconductor is misaligned due to a shock when the transfer material enters between the nip between the pressure body and the intermediate transfer material, or uneven rotation due to load change of the driving device. And the image quality on the transfer material is significantly deteriorated.

(Technical means for solving the problem and its action) In order to achieve the above object, in the present invention, an image carrier, an intermediate transfer member to which an image formed on the image carrier is transferred at a transfer position, An image in which a transfer material is brought into pressure contact with the intermediate transfer body, and a transfer material is passed between the intermediate transfer body and the pressure transfer body to transfer an image of the intermediate transfer body to the transfer material. In the forming device, from the transfer position to the press contact portion between the intermediate transfer member and the pressure transfer member, the maximum length in the feeding direction of the transfer material that can be used in the device,
The peripheral length of the intermediate transfer member in the moving direction is increased. By configuring in this way,
When the transfer paper enters the pressure section, the transfer image is not disturbed even if the mechanical load changes, and it is possible to obtain a high-quality image.

(Description of Embodiments) FIG. 1 is a schematic side view of an image forming apparatus showing an embodiment of the present invention, in which a photoreceptor 1 having a photoconductive layer on its surface is
It rotates in the direction of arrow A by a drive source (not shown).

Reference numeral 2 is an intermediate transfer member made of a rigid material such as steel having a film of silicon rubber or the like formed on its surface in the form of a rotating cylinder, and the photosensitive member is formed by an appropriate means such as a spring (not shown) arranged at the end of the bearing. It is pressed against and rotates.

A rotating cylindrical pressure member 3 made of a rigid material coated on the surface with a resin having an appropriate film thickness is in pressure contact with the intermediate transfer member 2, and the pressure contact force between them is the same as that of the photosensitive member and the intermediate transfer member. It is larger than that between the body and a heater 12 for heating the pressurizing body.

As the photoconductive layer formed on the surface of the photoconductor 1, it is preferable to use amorphous silicon having a relatively high pressure resistance or an organic semiconductor, and further, a material having a surface energy of 35 dyne / cm or less on the surface, For example, it is suitable to form a photosensitive layer by directly coating or mixing a silicone resin, a fluororesin or a block polymer having these functional groups. The thickness of the surface layer formed at this time is 2 μm or less, preferably 1 μm, and the surface roughness is 0.5 μm RM.
S or more, preferably about 0.2 μm RMS. The core metal of the photoconductor is formed of a conductive material such as aluminum, the same alloy, or a copper alloy, and its thickness is sufficient to withstand the contact pressure with the intermediate transfer member.

In the intermediate transfer member 2, a resin such as silicon rubber or urethane rubber is appropriately determined on the surface of a cored bar made of a rigid material such as steel by the pressure at the time of pressure contact.

As the pressurizing member 3, a resin having excellent compression resistance and heat resistance, such as Teflon and silicon, is appropriately set on a hollow steel core metal according to the contact pressure with the intermediate transfer member.

Further, as the heat source installed inside the pressure body,
Appropriate ones such as a halogen lamp and a sheet heating element can be used, and the surface temperature of the pressing body is kept constant by a control means (not shown).

As is well known on the periphery of the photoconductor 1, a primary charger 5 for uniformly charging the photoconductive layer, for providing image information on the charged surface to form an electrostatic latent image. Exposure unit 6, a developing device 7 that supplies toner to visualize the latent image, a cleaning device 4 that removes residual toner remaining on the surface of the photoconductor after transfer, an erase lamp 4b that removes residual charge, and static charge A container 4a and the like are provided.

Although the image forming means having such a structure is well known in the art, a detailed description thereof will be omitted. However, the toner image formed at the position of the developing device 7 is in contact with the intermediate transfer member 2 as the photosensitive member 1 rotates. Up to N ₁ . At this position, the toner image on the photosensitive member is pressure-transferred to the intermediate transfer member.

The toner image transferred to the intermediate transfer body in this way is pressed by the pressing body 3 as the transfer body rotates.
Leading to N _2. At this time, the surface circumferential length of the intermediate transfer member in the rotation direction from the nip portion N ₁ to the nip portion N ₂ is l ₂ .

On the other hand, the transfer paper 14 having a maximum length l _{1 in} the feeding direction of the transfer material that can be used in the apparatus taken out from the reservoir 9 such as a cassette and sent to the transport path 13 once waits at the position of the registration roller 10, Then, the toner image advancing on the intermediate transfer member is brought into contact with the toner image at the nip portion N _{2 at the same} timing, the toner image is received by the action of pressure and heat, and then discharged through the discharge roller 11 to the outside of the apparatus. .

In the above apparatus, the relationship of l ₁ <l ₂ is established.
Further, since the image formed on the surface of the photoconductor 1 is transferred onto the transfer paper 14, the image length is limited to l ₁ or less. Under the above conditions, when the leading edge of the image transferred to the intermediate transfer member 2 contacts the transfer paper 14 at the pressure contact nip portion N ₂ , the trailing edge of the image passes the pressure contact nip portion N ₁ , and the transfer paper 14 When the pressure contact nip member N ₂ enters, even if slips, vibrations, or the like occur between the photosensitive body 1 on the drive side and the intermediate transfer body 2 on the passive side due to load fluctuation, the transferred image is not affected.

(Effect) Since the present invention uses the above-described structure, it is possible to stably obtain a high-quality image even during continuous transfer.

[Brief description of drawings]

FIG. 1 is a schematic side view showing the structure of an image forming apparatus as an embodiment of the present invention, 1 ... Photosensitive member 2, 20 ... Intermediate transfer member 3 ... Pressing members N ₁ , N ₂ ... Nip portion

Claims (1)

[Claims] 1. An image carrier, an intermediate transfer member on which an image formed on the image carrier is transferred at a transfer position, and a pressure transfer member that is in pressure contact with the intermediate transfer member. In an image forming apparatus for transferring an image of the intermediate transfer body onto a transfer material by passing a transfer material between the transfer body and the pressure transfer body, the maximum length of the transfer material in the feeding direction usable in the apparatus. Rather, the image forming apparatus is characterized in that the peripheral length from the transfer position to the pressure contact portion between the intermediate transfer body and the pressure transfer body in the moving direction of the intermediate transfer body is increased.