JPH03100577A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine and a printer thereof.

(Prior Art and Problems to be Solved) The well-known image forming apparatus as described above includes an image bearing member, a transfer roller or a contact type transfer means that comes into pressure contact with the image bearing member, and a pressure nip portion between the two. A transfer site has already been proposed in which a transfer material such as paper is inserted through the transfer site to perform the transfer.

FIG. 5 is a schematic side view showing a typical configuration of such an image forming apparatus, in which an image carrier l (hereinafter referred to as a photosensitive member) has an axis perpendicular to the plane of the paper and rotates in the direction of the arrow. A surface photosensitive layer (referred to as a body) is uniformly charged by a power source 6 via a charging roller 2, and an image signal such as an image-modulated laser beam is projected onto the charged surface to generate a corresponding potential difference. This occurs to form an electrostatic latent image.

As the photoreceptor 1 rotates, the latent image is transferred between the photoreceptor 1 and the developing device 4.
When the latent image reaches the developing area facing the photoreceptor 1, charged toner is supplied from the developer 4 to cleanse the latent image and form a toner image.Then, this toner image is transferred to the photoreceptor 1 and the transfer roller that is in pressure contact therewith. 5, the transfer material P is conveyed to the transfer site at the same timing, and at almost the same time, a transfer bias is applied to the transfer roller 5 by a power source 6. The toner image on the photoreceptor side is transferred to the transfer material by the action of the electric field thus formed.

Reference numerals 9 in the figure indicate springs that are located at both ends of the transfer roller 5 (only one of which is shown in the figure) and press the roller against the photoreceptor at a predetermined pressure.

In the illustrated device, the passage of the transfer material is confirmed by a paper feed sensor consisting of a bin 7 that comes into contact with the transfer material and is rotationally displaced, and a photosensor 8 arranged so that the optical path is blocked by the rotation of the bin. It is now done by

FIG. 6 shows a part of the sequence of the above-mentioned device. After the leading edge of the transfer material reaches the paper feed sensor, the transfer material When the leading end reaches the transfer site, a transfer bias is applied to the transfer roller 5 at the same time.

In this way, since the arrival of the transfer material at the transfer site and the application of the transfer bias are almost constant, the contact force of the transfer roller and the electrostatic effect caused by the application of the transfer bias cause When using such lightweight and weak paper as a transfer material, there was a drawback of poor separation and frequent jams due to this.

The present invention has been made to deal with this situation, and at the leading end of the transfer material, the force that presses it toward the photoreceptor is released, and at the same time, the transfer bias is not applied. Ensures separation of transfer material after transfer,
The object of the present invention is to provide an image forming apparatus that can form images smoothly.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides an image forming apparatus equipped with an image bearing member and a transfer means in contact with the image bearing member. The present invention is characterized in that a means is provided for separating the transfer means from the image carrier when the leading edge region of the transfer material passes through a transfer site that is a contact portion between the image carrier and the transfer member.

With this configuration, even if a lightweight and weak thin paper is used as the transfer material, it can be easily and reliably separated from the image carrier after transfer.

(Description of Embodiments) FIG. 1 is a schematic side view of an image forming apparatus showing an embodiment of the present invention, and each member used in the apparatus is basically different from the apparatus shown in the above-mentioned figures. Corresponding parts are designated by the same reference numerals, and explanations thereof will be omitted unless particularly necessary.

In the illustrated device, a spring 9 that presses the transfer roller 5 against the photoreceptor l is supported by a plunger of a solenoid 10, and the transfer roller 5 is normally located at a position separated from the photoreceptor as shown in the figure. do.

A predetermined time after the transfer material P passes the paper feed sensor, the transfer material reaches the position of the transfer site, but after a further predetermined time, the tournoid 1° is biased and the transfer material 5
moves upward in the figure and comes into pressure contact with the photoreceptor 1 to form a transfer site, and a transfer bias is applied to perform the transfer.

After the transfer material passes through the transfer site, the solenoid lO of the transfer roller 5 is deenergized and the transfer roller returns to a position separated from the photoreceptor l as shown.

Regarding an experimental example, the process speed was 50 mm.
Using an OPC photoreceptor with a diameter of 30n+rn that rotates at a speed of A toner image is formed by development.

In the apparatus used, the distance between the paper feed sensor and the transfer site was 100 mm, so the transfer material reached the transfer site 2 seconds after being detected by the paper feed sensor.

Matching the timing with the toner image arriving at the transfer site,
A further 0.1 second after the transfer material P is supplied to the transfer site, the transfer roller 5 is brought into pressure contact with the photoreceptor 1, and the toner image is transferred from the photoreceptor 1 to the transfer material P by a negative transfer bias.

In the above case, by not pressing the transfer roller against the photoconductor for 0.1 seconds, there will be a 5 mm portion of the leading edge of the transfer material that is not pressed and transferred. Of course, it was possible to easily separate 54 gr/ from thin paper as shown below.

It has been found that even thin paper can be reliably separated by pressing the leading edge of the transfer material by at least 31III11 and not performing transfer.

FIG. 2 shows the sequence of the above device.

FIG. 3 shows another embodiment, in which only the related parts between the photoreceptor 1 and the transfer roller 5 are shown, and the other construction and operation are the same as in the experimental example.

In this device, a solenoid IO for bringing the transfer roller 5 into contact with and away from the photoreceptor 1 is provided only at one end.

As is well known, when placing originals in a predetermined position in a copying machine, there are some copying machines configured to place originals of all sizes along one edge of the placing area.

The illustrated device is suitable for such a so-called one-sided reference, and in such a case, one solenoid 10 for moving the transfer roller 5 toward and away from the photoreceptor 1 is sufficient. It is.

FIG. 4 shows the operation sequence of the above device. In this case, the solenoid 10 is energized and the transfer roller 5 comes into pressure contact with the photoreceptor 1 to establish the transfer site. The transfer bias is applied only until the transfer material passes through the transfer site, and after the transfer material has passed the transfer site, the solenoid 10 is deenergized and the transfer bias is also turned off to efficiently and efficiently apply the bias. Can be applied.

It goes without saying that such an application method can also be applied to the embodiments described above.

Further, although the case where a transfer roller is used as the transfer means has been described above, the present invention is not limited to this (the present invention can also be applied to those using a pressure-contact type transfer means such as a transfer belt). Needless to say, it is.

(3) As described in detail, according to the present invention, an image carrier;
By placing the image forming apparatus in an image forming apparatus including a transfer means in pressure contact with the transfer material and using the pressure nip portion of the two as the transfer site, and forming an area at the leading end of the transfer material where no pressure contact or transfer bias is applied. Since the transfer material can be easily and reliably separated from the image carrier after transfer, it prevents jamming and toner contamination in the device, and is extremely effective in obtaining high-quality images. be.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of an image forming apparatus showing an embodiment of the present invention, FIG. 2 is a sequence showing the same operation as above, FIG. 3 is a perspective view of main parts showing another embodiment, and FIG. It is a schematic side view explaining the operation|movement of a well-known apparatus, and is a sequence which shows the operation|movement of the 6th same. 1...Photoconductor, 2...Charging roller, 3...Image signal, 4...Developer, 5...Transfer roller, 6...Power source, 9...Spring, 10... ·solenoid. Hand-selling Shinbo Seijaku ζ (Method) April IO date, 1990

Claims (1)

[Scope of Claims] An image forming apparatus including an image carrier and a transfer means that comes into contact with the image carrier, wherein a leading end region of the transfer material passes through a transfer site that is a contact portion between the image carrier and the transfer means. An image forming apparatus is provided with means for separating a transfer means from an image carrier.