JPH05333715A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate turbulence of a toner image when the toner image is transferred, especially on and after the second transferring in a both side or multiple copying. CONSTITUTION:The toner image is formed on a photosensitive drum 1 by a primary electrifier 2, an exposure means 3 and a developing device 5, etc. This toner image is transferred to the transfer material P by a transfer electrifier 6. A guide member 11 guiding the transfer material P from downward is arranged between the transfer electrifier 2 and a transfer material carrying part 12. Multiple number of guts 13 are extended as a sliding contact prevention member in the width direction of the transfer paper P on the top surface of the guide member 11. Thus, when the transfer material P is passed over the guide member 11, an appropriate space is formed between the rear side of the transfer material P and the top surface of the guide member 11, both are brought into a sliding contact with each other and the triboelectrification of the guide member 11 is prevented. The turbulence of the toner image caused by the triboelectrification at the time of transferring can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer, and more specifically, it is mounted between a transfer separation device and a transfer material conveying section on the downstream side thereof to form a transfer material. The present invention relates to a guide member for guiding the lower part from below.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, when double-sided copying or multiple copying is performed on one transfer material, the transfer is performed twice or more on this one transfer material. It Therefore, the transfer material passes through the fixing device once and the toner image is fixed, and then, the toner image is fixed again by the fixing device. At this time, the resistance value of the transfer material that has once passed through the fixing device and is heated changes abruptly. Therefore, by changing the transfer condition between the first transfer and the second transfer, the transfer material is transferred during the second transfer and thereafter. Which tends to occur,
Distortion of the transferred image is prevented. Specifically, in the case where the transfer charger and the separation charger are provided, the transfer current of the transfer charger after the second time is made smaller than that of the first time, or the transfer current of the separation charger is changed. This is dealt with by making the separation current after the second time larger than that at the first time.

[0003]

However, as in the above-described conventional example, in a copying process in which a double-sided or multiplex copy, that is, a transfer material having a low humidity due to the heating at the time of the first fixing is transferred twice or more. Even if the transfer is properly performed, frictional electrification occurs due to strong rubbing between the transfer material immediately after the transfer and the guide member that guides the transfer material conveyance, and the guide member is There is a possibility that the image is strongly charged, and that this charging may cause remarkable disturbance in the transferred images after the second transfer.

Therefore, according to the present invention, a gap is formed between the transfer material and the guide member for guiding the transfer material from below by the rubbing prevention member, so that the rubbing of the both can be prevented and the transfer image of the transfer image can be prevented. An object of the present invention is to provide an image forming apparatus that prevents disturbance.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and is a latent image forming means for forming an electrostatic latent image on an image carrier, and the electrostatic latent image is inverted. In an image forming apparatus equipped with a developing device for developing by development to form a toner image, and a transfer separation device for transferring the toner image onto a transfer material, the image forming device is arranged downstream of the transfer separation device and separated. Between the guide member that guides the lower side of the transfer material and transfers the transfer material to the transfer material transporting portion on the further downstream side, and the transfer material that is disposed on the guide member and is separated from the upper surface of the guide member. And a rubbing prevention member that forms a gap.

In this case, the rubbing prevention member is a linear member wound a plurality of times around the guide member, or a plurality of the rubbing prevention members are arranged in a direction perpendicular to the conveying direction of the transfer material, and the tip end portion thereof is aforesaid. It may be a rib protruding from the upper surface of the guide member, or a roller-shaped member rotatably arranged in the transfer material conveyance direction.

Further, a latent image forming means for forming an electrostatic latent image on the image bearing member, a developing means for developing the electrostatic latent image by reversal development to form a toner image, and a transfer material for transferring the toner image. An image forming apparatus including a transfer separation device that transfers the transfer material to the downstream side of the transfer separation device, and guides the separated transfer material downward to convey the transfer material further downstream. It is also possible to provide a guide member to be delivered to the section and set the volume resistance value of the guide member to 10 ⁸ to 10 ¹³ Ωcm.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the vicinity of the image carrier of the image forming apparatus according to the present invention. In the image forming apparatus, a photosensitive drum 1 as an image carrier is arranged rotatably in the arrow R1 direction. Around the photosensitive drum 1, a latent image forming unit including a primary charger 2, an exposing unit 3, and a developing unit 5 as a developing unit are arranged along the rotation direction. In this embodiment, the electrostatic latent image is developed by reversal development. That is, the surface of the photosensitive drum 1 is uniformly charged by, for example, negative (-) by the primary charger 2, and an electrostatic latent image is formed by exposure with a semiconductor laser or the like. This electrostatic latent image is developed by the negatively charged toner of the developing device 5 and becomes a toner image.

Next, the toner image on the photosensitive drum 1 is transferred onto the transfer material P by the transfer charger 6. The transfer material P is
The toner image is transferred from a paper feed cassette (not shown) to a registration roller 7 via a paper feed roller or the like, and is evenly brought into close contact with the photosensitive drum 1 by a transfer guide 9. To be done. At this time, the transfer material P is provided with a charge having a polarity (plus) opposite to that of the toner on the back surface side by corona discharge, whereby the toner on the photosensitive drum 1 is electrically strongly adsorbed on the transfer material P. And transcribed.

The transfer material P on which the toner image has been transferred is separated from the photosensitive drum 1 by removing the residual charge on the back surface by the separation charge-eliminating needle charger 10. The separated transfer material P is conveyed along the guide member 11 and transferred to the transfer material conveying unit 12. After that, the toner image is fixed on the transfer material P by a fixing device (not shown), and the transfer material P is ejected outside the device.

By the way, in the case of copying on one surface of the transfer material P on both sides or multiple copies on one side, the toner image is transferred once and heat-fixed by the fixing device as described above. The toner image is transferred to the transfer material P again. At this time, the transfer material P is in a so-called low-humidity state with little water content after the first fixing. Therefore, at the time of the second and subsequent transfer of the toner image onto the transfer material P, the low-humidity transfer material P and the guide member 11 slide and frictionally charge, and the guide member 11 is strongly charged and the transfer material P is charged. In some cases, the unfixed toner image that has been transferred to is disturbed significantly.

Therefore, a rubbing prevention member 13 is provided. The linear rubbing prevention member shown in FIGS. 1 and 2 uses, for example, nylon-made 100 μm thick Tegus 13. This gut 13 is hung over the opening in the upper part of the transfer charger 6 many times, whereby the guts 13 are arranged on the upper surface of the guide member 11 at appropriate intervals. The appropriate interval means a degree to which the upper surface of the guide member 11 and the rear surface of the transfer material P do not directly contact each other when the transfer material P is conveyed along the upper surface of the guide member 11. That is, by these tegues 13 arranged at appropriate intervals, the tegues 1 are almost formed between the upper surface of the guide member 11 and the back surface of the transfer material P.
A gap corresponding to the thickness of 3 is formed.

More specifically, even when the transfer material P having the maximum width is used for the respective tegs 13 near both ends in the longitudinal direction of the transfer charger 6, each tegs 13 is transferred to the transfer material P.
It is arranged so as to be positioned outside the left and right end edges of the above, and a total of 22 pieces are arranged in the middle portion between these left and right Tegs 13 at intervals of 10 to 20 mm. Table 1 shows the relationship between the potential and the image disturbance due to the frictional charging of the guide member 11 (20 ° C., 5% environment).

[0015]

[Table 1] From Table 1, it is possible to extend the guide member 11 by increasing the number of the gussets 13.
It was found that the electrification was reduced and the image was not disturbed. It was also found that the charging of the guide member 11 should be 1.0 kV or less. As a result, even if a large number of thin ribs projecting the upper end from the upper surface of the guide member 11 instead of the gussets 13 are installed in the direction perpendicular to the transport direction of the transfer material P (longitudinal direction of the transfer charger 6), the same is true. It turns out that the effect of is obtained.

As another embodiment of the rubbing prevention member, FIG.
It is also possible to use roller members 15, 15 ... As shown in FIG. On the upper surface of the guide member 11, a large number of notches 11
a, 11a ... Forming these notches 11a, 11a
The roller members 15, 15 ... Are arranged on the ... And these roller members 15, 15 ... Are rotatably supported by the shaft 16. The upper end of each roller member 15 is slightly projected from the upper surface of the guide member 11, and its rotation direction is aligned with the conveying direction of the transfer material P. When the transfer material P contacts these roller members 15, 15, ... Rotate,
Moreover, the back surface of the transfer material P is prevented from coming into contact with the top surface of the guide member 11. Therefore, the guide member 11 is prevented from being unnecessarily charged due to friction with the transfer material P. Table 2 shows the relationship between the potential of the roller member 15 due to friction and the image disturbance.

[0017]

[Table 2] From Table 2, image disturbance did not occur even in the roller member 15, and the guide potential was 1.0 KV or less as in the above-mentioned embodiment.

In each of the above embodiments, a sliding contact preventing member is provided to prevent frictional electrification between the guide member 11 and the transfer material P. However, the transfer material P and the guide member 11 rub strongly against each other. However, the same effect can be obtained by changing the material of the guide member 11 to prevent frictional electrification.

However, if the volume resistance of the guide member 11 is too low, the transfer corona generated by the transfer charger 6 is drawn into the guide member 11 side, which causes another problem that transfer failure occurs. Therefore, the volume resistance of the guide member 11 has a good medium-high resistance value. Specifically, it is desirable to be 10 ⁸ Ωcm or more and 10 ¹³ Ωcm or less. Table 3 shows the relationship between the volume resistance value, image distortion and transfer failure.

The material of the guide member 11 may be any resin as long as it has a medium to high resistance value by containing carbon.

[0021]

[Table 3]

[0022]

As described above, according to the present invention,
A rubbing prevention member is provided between the guide member and the transfer material to prevent frictional electrification due to sliding contact between them, or
By setting the volume resistance value of the guide member to 10 ⁸ to 10 ¹³ Ωcm, the guide member is prevented from being charged,
A good image can be obtained by effectively preventing the image disturbance at the time of the second and subsequent toner image transfer at the time of double-sided or multiplex copying.

[Brief description of drawings]

FIG. 1 is a sectional view of the vicinity of a transfer charger of an image forming apparatus.

FIG. 2 is a perspective view of a transfer charger.

FIG. 3 is a perspective view showing another embodiment of the rubbing prevention member.

[Explanation of symbols]

 1 Image Carrier (Photosensitive Drum) 2 Electrostatic Latent Image Means (Primary Charger) 3 Electrostatic Latent Image Means (Exposure Means) 5 Developing Means (Developer) 6 Transfer Charger 11 Guide Member 13 Rubbing Prevention Member (Tegus) ) 15 Rubbing prevention member (roller member) P Transfer material

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 2, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

[0017]

[Table 2] From Table 2, image disturbance did not occur even in the roller member 15, and the guide potential was 1.0 KV or less as in the above-mentioned embodiment.

Claims (5)

[Claims] 1. A latent image forming means for forming an electrostatic latent image on an image carrier, a developing means for developing the electrostatic latent image by reversal development to form a toner image, and a transfer material for transferring the toner image. And a transfer separation device that transfers the transfer material to the transfer separation device, which is disposed on the downstream side of the transfer separation device and guides the lower part of the separated transfer material to convey the transfer material further downstream. A guide member that is delivered to the portion, and a slide prevention member that is disposed on the guide member and forms a gap between the upper surface of the guide member and the separated transfer material,
An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the rubbing prevention member is a linear member wound around the guide member a plurality of times. 3. The rubbing prevention member is a rib having a plurality of sheets arranged in a direction perpendicular to the transfer direction of the transfer material and having a tip portion protruding from the upper surface of the guide member. The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein the rubbing prevention member is a roller-shaped member that is rotatably disposed in a transfer direction of the transfer material. 5. A latent image forming means for forming an electrostatic latent image on an image carrier, a developing means for developing the electrostatic latent image by reversal development to form a toner image, and a transfer material for transferring the toner image. And a transfer separation device that transfers the transfer material to the transfer separation device, which is disposed on the downstream side of the transfer separation device and guides the lower part of the separated transfer material to convey the transfer material further downstream. An image forming apparatus, comprising: a guide member that is delivered to a portion, and the volume resistance value of the guide member is 10 ⁸ to 10 ¹³ Ωcm.