JPS60142371A - Transfer device - Google Patents

Abstract

PURPOSE:To stabilize transfer performance and conveyance performance by shifting the position of a guide member which guides a transfer material according to variation in the thickness of paper, and making the passing path of the transfer material to an image carrier constant. CONSTITUTION:A detecting means which detects the thickness of the transfer material is provided on the path of the transfer material 3. This detecting means operates as a conveyor roller, and when the transfer material 3 conveyed by rollers 9 and 10 varies in thickness (t), the driven roller 10 driven in press contact by the force P of the driving roller 9 generates force P' as shown by an arrow. The difference between the constant force P and varying force P' is detected by a pressure sensor 11 such as a strain gauge to obtain the displacement extent of the driven roller 10. This displacement extent corresponds to the thickness (t) of the transfer material 3. Then, an arithmetic controller 12 is provided to calculates the relation between the displacement extent and positions of preset transfer guides 5 and 6 and move the transfer guides 5 and 6 to proper positions. This arithmetic controller regards the distance (a) between a tangent to the image carrier and the tip of the guide 5 as a controlled variable during guide position movement.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for transferring a developed image on an image carrier to a transfer material using a corona discharger, and relates to a transfer device used for example in electrophotographic copy decoration. It is.

For development on an image bearing member such as a photosensitive drum, a method is widely used in which corona discharge is applied from the back side of the transfer material. Nowadays, with the diversification of transfer materials, it is difficult to maintain stable conveyance of the transfer material and transfer performance using this method.

Tip 9: In corona transfer, it is preferable to reliably hold all types of transfer material at the optimal transfer position, but the conveyance path of the transfer material may vary depending on the conditions of the transfer material, especially differences in thickness or stiffness. Transfer performance and conveyance capacity may change. When the guide member to the transfer position is fixed, it is difficult to achieve both transfer ability and conveyance ability.

An object of the present invention is to stabilize transfer performance and conveyance performance by moving a member that guides to a transfer position to a position close to the optimum position in response to changes in the thickness of the transfer material, particularly the paper at the center.

A transfer device according to the present invention is a device for transferring a developed image on an image carrier to a transfer material using a corona discharger, and includes means for transporting the transfer material to the entire transfer area, and a guide member for guiding the transfer material to the transfer position. , a means for detecting the thickness of the transfer material provided on the path from the conveying means to the guide section, and a means for making the passage of the transfer material with respect to the image carrier constant regardless of changes in the thickness of the transfer material. The present invention is characterized in that it includes a means for completely changing the position of the guide portion H in response to a signal from the above-mentioned detection means.

The present invention will be described below with reference to all the drawings.

FIG. 1 shows a transfer device used in an electrophotographic copying machine. In the figure, 1 is an image carrier consisting of a photosensitive drum, 2 is a toner image formed on its surface, 3 is a transfer material, 4 is a conveyance roller that conveys the transfer material to the transfer area, 5 and 6 are transfer materials 3 is a guide for guiding the transfer material to the transfer position, 7 is a corona discharger for transfer, and 8 is a separating section for separating the transfer material from the image carrier. In the illustrated transfer device, the toner image 2 on the surface of the image carrier 1 is conveyed by a conveyance roller 4, guided by transfer guides 5 and 6, and transferred from the back surface of the transfer material 3, which is brought into contact with the image carrier, by a corona discharger 7. The toner 2 is transferred to the surface of the transfer material 3 by a corona discharge having a polarity opposite to that of the toner 2 provided through the transfer material, and then transferred to the image carrier 1 by a separated phase 8.
A copy image 2' is obtained.

In the above structure, the relative relationship between the positions of the carrier transfer corona discharge distribution transfer material is what determines the high specific gravity among the conditions for good transfer. When the image carrier and the corona discharge distribution are constant, the approach angle of the transfer material governs the transferability. However, even with transfer paper, changes in thickness change the path of the image carrier to the image carrier, making stable transfer difficult.

Therefore, it is effective to change the passage and swivel of the transfer material according to the conditions for good transfer depending on the difference in the transfer material, especially the change in the thickness of the paper.

The transfer device according to the present invention changes the position of the guide member that guides the entire transfer material according to the change in the thickness of the paper, thereby making the passage and speed of the transfer material relative to the image carrier constant. , which stabilizes transfer performance and conveyance performance.

FIG. 2 shows an embodiment of the transfer device l according to the invention. In the figure, the same reference numerals as those in FIG. 1 indicate parts that perform similar operations. In the embodiment shown in FIG. will be provided. In the illustrated embodiment, this detection means also functions as a conveying roller, and is comprised of a drive roller 9 and a driven roller 10 that is pressed against and follows the drive roller. Reference numeral 11 denotes a pressure sensor such as a strain gauge, which presses the driven roller 10 against the driving roller 9 by a force P. As the thickness t of the transfer material 3 conveyed by the rollers 9 and 10 changes, the driving roller 9
The driven roller 10, which is driven by pressure with a force P, should apply a force P' in the direction of the arrow. The difference between the constant force P and the varying force P' is detected by a pressure sensor 11 such as a strain gauge to obtain the amount of displacement of the driven roller 10. This amount of displacement is the thickness t of the transfer material 3
corresponds to

In order to make the passage path of the transfer material 3 with respect to the image carrier 1 constant regardless of changes in the thickness of the transfer material by changing the position of the guide member 5.6 in accordance with the signal indicating the above-mentioned displacement amount. , the above displacement amount and the preset transfer guide 5
, 6, and moves the transfer guides 5, 6 to appropriate positions. This arithmetic and control device uses the distance a between the tangent to the image carrier and the tip of the guide 5 as the amount to be controlled when moving the guide position. Thick paper has high stiffness and if a is small, the resistance will be large, resulting in transfer deviation or lower transfer efficiency, so the transfer guide moves in the direction of widening a.

FIGS. 3(a) and 3(b) show the positions of the guides 5 and 6 and the movement of the paper in the transfer area in the case of small paper thickness (,) and the case of thick paper with holes, respectively.

In order to keep the length of paper contact with the drum in the transfer area constant, shown as t, r t,' in the figure, the positions of the guides 5 and 6 are moved by distances t,, t,' from the transfer center. . That is, when the paper is small in thickness, the paper is not stiff, so the paper is conveyed with a tendency to follow the drum, so the contact length becomes a dog.

Also, when using thick paper, the paper is stiff, so guide 5
Since the distance is close to a straight line connecting the tip of the roller and the separation roller 13, the length of contact with the drum is small. Therefore, the guides are moved so that each tl=tl' is increased from (a) 62 when the paper thickness is small to (b) tz' when the paper thickness is large.

The control target of the above device is the transfer guide position, which controls the transport path of the transfer material, but the relationship between the detected thickness information of the transfer material, the transfer guide position, and the transfer corona discharge current is also sent to the control circuit. If you enter the information in advance, the transfer will be more reliable and stable.

As explained above, the passage of the transfer material to the image bearing member has a great influence on the transfer.
According to the present invention, by detecting changes in the thickness of the transfer material and moving the transfer ID position to keep the passage and waste constant, it is possible to stabilize the transfer efficiency and image quality in a good state.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a transfer device used in an electrophotographic copying machine, Fig. 2 is a diagram showing an embodiment of a transfer bag H according to the present invention, and Fig. 3 (,) (b) shows the movement of a guide. FIG. DESCRIPTION OF SYMBOLS 1... Image carrier, 2... Toner image, 3... Transfer material, 4... Conveyance roller, 5.6... Guide, 7
... Corona discharger for transcription, 8... Separate department system, 9.
...Drive roller, 10...Followed roller, 11...
Pressure sensor, 12... Arithmetic control device.

Claims (1)

[Claims] 1. In an apparatus for transferring a developed image on an image carrier to a transfer material using a corona discharger, means for transporting the transfer material to a transfer area and a guide section for guiding the transfer material to a transfer position. a means for detecting the thickness of the transfer material provided on the path from the conveyance means to the guide member, and a means for making the passage path of the transfer material relative to the image carrier constant regardless of changes in the thickness of the transfer material. A transfer device characterized in that said transfer device further comprises means for changing the position of said guide member in response to a signal from said detection means. 2. Claims characterized in that as the thickness of the detected transfer material increases, the guide member is moved in a direction that moves the guide member away from the image carrier or in a direction that shortens the distance to the transfer position. The transfer device according to item (1). 3. Claim No. 3, characterized in that the transfer material thickness detecting means is a pressure sensor provided on the conveying means.
1) The transfer device described in section 1).