JPH04121344A - Guide device before transcription - Google Patents

Abstract

PURPOSE:To improve stability of a transcription sheet by forming a point end part, opposed to a picture carrier, of a lower guide plate, provided below a conveying route of the transcription sheet, as a protrusive curved guide to a picture carrier side, and positioning the most adjacent position to the picture carrier of this point end part in the vicinity of an action region to the picture carrier of a transcription charger. CONSTITUTION:A point end 7b of a lower guide plate 7 appears in an action region to a picture carrier of a transcription charger 3. Consequently, even when a manufacture error, mounting position error, etc., are provided in the lower guide plate 7, a transcription sheet 2 is surely guided to a transcription region to improve stability of the transcription sheet 2 in the transcription region. A point end part 7a of the lower guide plate 7 is formed in a protrusive curved shape to a picture carrier side and opposed to the picture carrier to increase a closely attached area to the picture carrier of the guided transcription sheet 2 in a conveying direction of the transcription sheet. Further, the point end part 7a of the lower guide plate 7 is set so that the most adjacent position to the picture carrier is positioned in the vicinity of the action region of the transcription charger 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pre-transfer guide device used in an image forming apparatus such as a copying machine or a laser printer that forms an image using an electrostatic transfer method. The present invention relates to a pre-transfer guide device that guides a transfer sheet toward a transfer section where a transfer charger and a transfer charger that transfer an image on an image carrier onto a transfer sheet face each other.

BACKGROUND OF THE INVENTION Conventionally, various methods have been proposed and employed for guiding a transfer sheet toward a transfer section, such as those using only a guide plate and those using a guide roller in combination. Those with only a guide plate are widely used because of their simple structure and reliable guide function. Many of these, for example,
As in the one described in Publication No. 3, guide plates are provided both above and below the transport path of the transfer sheet (FIG. 4).

Problem to be Solved by the Invention However, the closer the lower guide plate is to the front end facing the transfer section or closer to the image carrier, the better the adhesion between the transfer sheet and the image carrier, which may cause transfer misalignment. It becomes difficult to do. Furthermore, the closer the tip of the lower guide plate is to the transfer area, the more stable the transfer sheet is in the transfer area. This is known from experience. Further, the larger the area of the transfer sheet in close contact with the image carrier in the transfer area, the better the transferability. However, the conventional pre-transfer guide device is only provided in front of the transfer section, and does not satisfy the above points.

In the one described in the above publication, as shown in FIG. 4, an elastic guide b is provided at the tip of the lower guide plate a so as to extend toward the transfer charger g, but there is still a distance between it and the transfer charger g. The transfer sheet d cannot be guided all the way to the transfer area because it leaves X and does not reach the transfer area, and the closest part to the photoconductor e is the extreme bend f, so the transfer sheet d is guided to the photoconductor e. It cannot be backed up so that the contact area becomes large. Therefore, sufficient transferability has not yet been obtained. This is especially a problem when guiding a seat with weak backs or a seat that is curled.

Therefore, it is conceivable to simply make the tip of the lower guide plate face the transfer area. However, the leading end of the lower guide plate that extends into the transfer area approaches the image carrier and is charged by the transfer discharge from the transfer charger, causing the toner on the image carrier to adhere to the toner. Dirt grows. This toner stain may stain the transfer sheet, or the toner may fall or scatter, staining the inside of the image forming apparatus.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pre-transfer guide device that can solve the above-mentioned conventional problems by improving the shape and installation structure of the lower guide plate.

Means for Solving the Problems In order to achieve the above-mentioned problems, the present invention aims to move a transfer sheet toward a transfer section where an image carrier and a transfer charger for transferring an image on the image carrier to a transfer sheet face each other. In a pre-transfer guide device that guides a transfer sheet, the tip of a lower guide plate provided below the conveyance path of the transfer sheet, which faces the image carrier, is a curved guide portion that is convex toward the image carrier. The transfer charger is characterized in that the position closest to the transfer charger is located near the area of action of the transfer charger on the image carrier, and the tip thereof faces into the area of action.

According to the above structure of the present invention, the tip of the lower guide plate faces the area of action of the transfer charger on the image carrier, so even if there is a manufacturing error or an installation position error of the lower guide plate, the transfer is not possible. The stability of the transfer sheet in the transfer area can be improved by reliably guiding the sheet to the transfer area. In addition, the tip of the lower guide plate has a curved shape convex toward the image carrier and faces the image carrier, unlike the conventional case in which the edge of the lower guide plate or a portion close to this faces the edge. The contact area of the guided transfer sheet to the image carrier can be made thicker in the transfer sheet conveyance direction, and the tip of the lower guide plate is positioned closest to the image carrier during transfer charging. Since the contact area of the transfer sheet to the image carrier can be increased over the transfer area, the area of contact of the transfer sheet to the image carrier can be increased over the transfer area. The tip side from the part closest to the image carrier extends into the action area, but due to the curved shape of the tip, it gradually moves away from the image carrier, so the tip side reaches the action area. Even if the toner image on the image bearing member is charged due to the influence of transfer discharge of the transfer charger due to the presence of the image bearing member, it is possible to prevent the toner image on the image bearing member from being electrostatically attracted by this charging.

Embodiment An embodiment of the present invention shown in FIGS. 1 to 3 will be described.

The figure shows a transfer section of an image forming apparatus that forms images using an electrostatic transfer method. In FIG. 1, a photosensitive drum 1 forms an electrostatic latent image by being subjected to image exposure in a negative charged state. This electrostatic latent image is visualized by toner development, and this developed image is transferred onto the conveyed transfer sheet 2 by transfer discharge during transfer charging 3, thereby forming an image on the transfer sheet 2. A timing roller 5 is provided in front of the transfer section 4. This timing roller 5 stops receiving the transferred transfer sheet 2 in a stopped state, corrects the skew of the transfer sheet 2 by aligning the leading edge, and forms the image on the transfer sheet 2 and the photosensitive drum 1 according to the driving start timing. The transfer sheet 2 is sent out toward the transfer section 4 at a timing such that its leading edge coincides with the developed image.

A pair of upper and lower guide plates 6.7 are provided on the conveyance path 9 of the transfer sheet 2 between the timing roller 5 and the transfer section.
The transfer sheet 2 sent out from the timing roller 5 is guided toward the transfer section 4. The upper and lower guide plates 6.7 guide the transfer sheet 2, which is sent out at a predetermined entry angle toward the photosensitive drum 1 by the timing roller 5, in the sending direction depending on the material, thickness, presence or absence of curl, and direction of the curl of the transfer sheet 2. Even if there are variations, the device is guided from above and below so as to face the transfer part 4 reliably and smoothly without being affected by these variations. In particular, the upper guide plate 6 guides the transfer sheet 2 to loosen it when the entry angle is steep to ensure the transferability of the transfer sheet 2 to the transfer section 4, and the lower guide plate 7
When the entry angle of the transfer sheet 2 is gentle, it is guided to make it tighter to ensure adhesion to the photosensitive drum 1.

A separation charger 8 is provided behind the transfer charger 3 to separate the transfer sheet 2 from the photosensitive drum 1 after transfer so that it can be transported to the next step.

By the way, as described above, the closer the lower guide plate 7 is to the photosensitive drum 1 with its leading end facing the transfer section 4, the more the transfer sheet 2
The adhesion between the photosensitive drum 1 and the photosensitive drum 1 is improved, and transfer misalignment is less likely to occur. Also, attach the tip of the lower guide plate 7 to the photosensitive drum 1.
The closer it is to , the more stable the transfer sheet is in the transfer area. Furthermore, the photosensitive drum 1 in the transfer area of the transfer sheet 2
The larger the area of contact with the ink, the better the transferability.

In order to satisfy this requirement, in this embodiment, as clearly shown in FIG. 2, the lower guide plate 7 is made of metal such as stainless steel, or made of resin with high rigidity so that it can be easily deformed. It is assumed that it will not be done. The tip 7a of the lower guide plate 7 forms a gently arcuate curved portion convex toward the photosensitive drum 1 and faces the photosensitive drum 1, and the tip 7b is placed within the transfer discharge area α of the transfer charger 3. I try to be present. Further, the tip end 7a of the lower guide plate 7 is arranged to be closest to the photosensitive drum 1 in the vicinity of the transfer discharge area α.

As a result, the tip 7b of the lower guide plate 7 faces the action area α of the transfer charger 3 on the photosensitive drum 1, so even if there are manufacturing errors or installation position errors of the lower guide plate 7,
The stability of the transfer sheet 2 in the transfer area can be improved by reliably guiding the transfer sheet 2 to the transfer area.

Further, the tip end 7b of the lower guide plate 7 has a curved shape convex toward the photosensitive drum 1 side, and is opposed to the photosensitive drum, and the edge portion of the lower guide plate 7 or a portion close to this is opposed. Compared to the conventional case, the area in which the guided transfer sheet 2 is in close contact with the photosensitive drum 1 can be increased in the conveyance direction of the transfer sheet 2. To explain this with reference to FIG. 3, the tip portion 7b having the above shape is attached to the transfer sheet 2 between the adhesion limit line LI of the transfer sheet 2 to the photosensitive drum 1 and the effective transfer separation limit line L2. , the transfer sheet 2 can be brought into contact with the photosensitive drum 1 within a range of length S in the sheet conveyance direction, and the transfer sheet 2 can be corrected and brought into close contact with the photosensitive drum 1 within the range so as not to exceed the effective separation limit, and the tip of the lower guide plate 2 is simply In the case of the conventional method in which the photosensitive drum 1 is close to the photosensitive drum 1, the correction contact range is smaller than the SI, as shown by the broken line in FIG. High adhesion is evident.

At the same time, since the tip end 7a of the lower guide plate 7 is positioned closest to the photosensitive drum 1 in the vicinity of the action area α of the transfer charger 3, the transfer sheet 2 is directed toward the photosensitive drum 1. It is possible to increase the adhesion area over the transfer area, and moreover, the area from the portion P closest to the photosensitive drum 1 near the action area α of the tip 7a of the lower guide plate 7 to the tip 7b is in the action area α. However, due to the curved shape of the tip portion 7a, it gradually moves away from the photosensitive drum 1, and the gap d1 with the photosensitive drum 1 at the closest portion
On the other hand, since the gap d2 at the tip 7b becomes larger,
Since the front end 7a side faces the action area α, the influence of the transfer discharge of the transfer charger 3 is received within the range β.
It is possible to avoid electrostatic adhesion of the upper toner image.

Therefore, in the case of this embodiment, since the transfer efficiency is high and there is no transfer deviation, the transfer performance is greatly improved.
There is no possibility that toner may adhere to the transfer sheet or the inside of the apparatus. Since the lower kite plate 7 has high rigidity, it is not easily deformed by external force, and can maintain the above-mentioned form and various initial conditions such as the gap with the photosensitive drum 1 well, so that the above characteristics can be maintained over a long period of time. can perform stably.

Effects of the Invention According to the present invention, even if the tip of the lower guide plate faces the action area of the transfer charger on the image carrier, and there are manufacturing errors or installation position errors of the lower guide plate, the transfer sheet can be moved. The stability of the transfer sheet in the transfer area can be improved by reliably guiding the sheet to the transfer area, and the tip of the lower guide plate has a curved shape convex toward the image carrier and faces the image carrier. Therefore, it is possible to increase the contact area of the guided transfer sheet to the image carrier in the transfer sheet conveyance direction compared to the conventional case in which the edge portion or a portion close to the edge portion of the lower guide plate faces each other. In addition, the tip of the lower guide plate is configured such that the closest position to the image carrier is located near the action area of the transfer charger, thereby increasing the contact area of the transfer sheet to the image carrier. Although the tip side of the lower guide plate extends from the part closest to the image carrier in the vicinity of the action area to the action area, due to the curved shape of the end part, Although it gradually moves away from the image carrier and is charged under the influence of the transfer discharge of the transfer charge because its tip side faces the action area, the charge on the image carrier is Since it is possible to prevent the toner image from being electrostatically attracted, it is possible to significantly improve transfer performance by improving transfer efficiency and preventing transfer misalignment. It is possible to prevent toner stains on the tip of the lower guide plate due to the toner entering the inner action area, and staining of the transfer sheet and the inside of the device due to this.

[Brief explanation of drawings]

FIG. 1 is a side view of a transfer section of an image forming apparatus showing an embodiment of the present invention, FIG. 2 is a partially enlarged view, and FIG. 3 is a partially illustrating state of contact between the transfer sheet and the photosensitive drum. FIG. 4 is a side view of a transfer section showing a conventional example.

Claims (1)

[Claims] (1) In a pre-transfer guide device that guides a transfer sheet toward a transfer section where an image carrier and a transfer charger that transfers the image on the image carrier to a transfer sheet face each other, a pre-transfer guide device is provided below the conveyance path of the transfer sheet. The tip of the lower guide plate facing the image carrier is a curved guide portion that is convex toward the image carrier, and the closest position of this tip to the image carrier is the area of action of the transfer charger on the image carrier. 1. A pre-transfer guide device, characterized in that the pre-transfer guide device is located in the vicinity of the transfer guide device, and has a leading end facing into the action area.