JPS61138974A - Device for separating transfer material - 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) Purpose of the Invention (Field of Industrial Application) This invention relates to image forming apparatuses that utilize an electrostatic transfer process, such as electrophotographic copying machines and printers, and particularly to separation control of transfer materials therein. It is related to the device.

(Prior art and problems to be solved) First, the photoconductive layer on the surface of the image carrier is uniformly charged, and then a light image corresponding to a multi-transferred image is projected onto it to form an electrostatic latent image. A transferable toner image is formed by supplying and adhering powder toner charged to the opposite polarity to the latent image, and a transfer material, mainly paper, is brought into contact with this, and a powder toner having a polarity opposite to that of the toner is applied to the back of the transfer material. An image configured to transfer a toner image from an image carrier side to a transfer material side by applying a charge, separate the transfer material carrying the toner image from the image carrier, and convey the transfer material to a next process site. Forming devices are well known in the art.

In such an image forming apparatus, after transfer, it is necessary to separate the transfer material from the image carrier so as not to disturb the toner image formed on the surface of the transfer material by relatively weak adhesion force called electrostatic adsorption force. This is extremely important in order to obtain good quality images.

Separation methods for this purpose include mechanical means such as a separation belt, separation rollers, separation claws, etc. that forcefully separate the transfer material at the transferred position, and mechanical means that forcefully separates the transfer material at the transfer location. After the transfer, the charge of the transfer material is neutralized by applying a charge of the opposite polarity to the toner, that is, a charge of the same polarity as the toner, or a discharge by adding AC discharge to the charge. Many electrostatic charge eliminating means have been proposed in the past that utilize their own elasticity and weight to separate them from the image carrier, and the present invention particularly relates to the latter.

The mechanism of the static electricity removal means is basically as described above, but as can be easily understood, the separation of the transfer material is largely related to the difficulty of separating the transfer material at its leading edge in the running direction. It has been confirmed through experiments that there is a difference in separation performance depending on whether or not toner is present in a portion, and when no toner is present, the adhesion between the image bearing member and the transfer material is good and separation is difficult.

Regarding the image forming action in the vicinity of the transfer site, this means that the transfer of the toner to the transfer material is facilitated by operations such as pre-transfer charging to the same polarity as the toner and pre-transfer exposure at the pre-transfer position.

Due to the neutralization effect of transfer material charge due to separation charge, the residual charge remaining on the image carrier even after transfer is relatively /J%,
In addition, since the amount of residual toner remaining on the surface of the image carrier without contributing to transfer is small, the image is carried by electrostatic induction at a position after the separation site on the transfer material, which is almost in an uncharged state due to separation charging. Regarding the adhesion of the transfer material to the body, once the transfer material has adhered to the surface of the image carrier at the transfer site, in the absence of toner, it mechanically adheres strongly to the mirror-like surface of the image carrier. On the other hand, if a small amount of toner is present, this will act to form minute irregularities on the surface of the image carrier, which will have a greater tendency to weaken the adhesion between the transfer material and the image carrier. This is considered to be the result of the experiment described above.

Therefore, if the separation conditions are set so that the exposure intensity and discharge current for pre-transfer exposure, pre-transfer charging, transfer charging 1-separation charging, etc. are suitable for when there is no toner at the leading edge of the image, the toner once transferred to the transfer paper There is a risk that the toner will be retransferred to the image carrier, and if separation conditions are set when toner is present at the leading edge of the image, it will be difficult to separate the transfer material that does not have toner in that area.

The present invention has been made to deal with such situations, and by changing the separation conditions to suit the amount of toner at the leading edge of the image, it solves the above-mentioned drawbacks and always maintains a good condition. It is an object of the present invention to provide a separation control device that can separate transfer materials in a stable state.

(2) Structure of the invention (technical means for solving problems and their effects) In order to achieve the above-mentioned object, the present invention provides an image forming apparatus that uses an electrostatic transfer process by disposing a sensor at an appropriate position. The image density at the leading edge of the image is detected, and in response to this, the discharge currents of the pre-transfer charger, transfer charger 1-separation charger are determined to optimal values.

With this configuration, the transfer process can be performed easily.

Since the transfer material functions to be easily separated after transfer, it is possible to effectively prevent the occurrence of jams due to poor separation due to occurrence of re-transfer.

(Description of Embodiment) FIG. 1 is a schematic side view showing the main parts of an embodiment in which the present invention is applied to a copying machine.

The surface photoconductive layer of the photoconductor 1, which has a photoconductive layer on its surface and is formed into a cylindrical shape that rotates in the direction of the arrow A, is uniformly charged by the primary charger 2, and the photoconductive layer is uniformly charged by the primary charger 2, and the photoconductive layer is uniformly charged by the primary charger 2.
is irradiated and scanned by the light source 11, and the reflected light forms an image on the charged surface of the photoreceptor through the mirror 11a + llb + lens system 12 to form an electrostatic latent image, and as the photoreceptor rotates, the latent image changes. Powder toner is supplied by a developing device 3 to form a toner image. Next, a corona discharge having the same polarity as the toner is applied to the pre-transfer charger 14 including a lamp for static elimination to weaken the adhesion of the toner, and then the transfer material supplied through the conveyance path 5 is A transfer material is brought into contact with a photoreceptor having a toner image at a transfer site equipped with a transfer charger 6,
At this time, the charger 6 charges the back side of the transfer material with a polarity opposite to that of the toner, thereby transferring the toner on the photoreceptor side to the transfer material side.

After transfer, the transfer material that advances with the photoreceptor reaches the position of the separation charger 7, where it is charged with the same polarity as the toner to neutralize the charge on the transfer material, and the transfer material is now in an uncharged state. is separated from the photoreceptor traveling upward by its own elasticity and is fed to the fixing site by the conveying means 9.

It is assumed that residual toner remaining on the surface of the photoreceptor without contributing to transfer is removed and cleaned by the cleaning device 8 before entering the next image forming step.

In the illustrated embodiment, an appropriate optical sensor 10 using a phototransistor, CCD, etc. is disposed at a suitable location upstream of the primary charger 2 when viewed from the direction in which the photoreceptor travels, and an optical sensor 10 is provided to reflect the original. The sensor receives reflected light from a semi-transparent plate 14 placed in the optical path to detect the density of the leading edge of the original image.

This density signal is applied to the pre-transfer charger 4. The transfer charger 6 and the separation charger 7 are inputted to a control unit 34, which is equipped with a means for generating a predetermined high voltage and a means for controlling separation conditions, and applies a voltage suitable for the image density to each charger to obtain a suitable voltage. Separation conditions can be obtained.

Specifically, when there is no toner at the leading edge of the image, it is difficult to separate the transfer material, so the current of the pre-transfer charger is increased, that of the transfer charger is decreased, and the current of the separation charger is increased to perform the separation function. improve.

On the other hand, when the density at the leading edge of the image is high, the separation of the transfer paper is good, so the current of the pre-transfer neutralization charger is decreased, that of the transfer charger is increased, and the current of the separation charger is decreased to cause retransfer. to prevent

FIG. 2 is a schematic diagram of the main parts of a copying machine showing another embodiment of the present invention, in which the same parts as in FIG. Since they are similar, their explanation will be omitted.

In this embodiment, the high voltage control section 13 is connected to the original optical image 16.
A potential sensor 15 is disposed at a position after the projection of the electric potential sensor 15, and each charger is controlled by the output signal thereof.The same function as described above can also be obtained in this manner. would be easy to understand.

In addition, the current of the separation charger can be changed in accordance with the amount of toner at the leading edge of the transfer material, and the same effect can be achieved by changing the current of the separation charger according to the amount of toner at the leading edge of the transfer material. can be obtained.

Although the present invention has been described above for a case where it is applied to a copying machine, it goes without saying that the present invention can also be applied to other image forming apparatuses.

(3) Effects of the invention This is because the present invention has the configuration described above.

An electrostatic separation device in an image forming apparatus can always separate transfer materials in a good condition regardless of the image density, and effectively prevents retransfer and jamming to perform stable separation. be able to.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts of an embodiment in which the present invention is applied to a copying machine, and FIG. 2 is a schematic side view showing another embodiment. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... -order charger, 4... Pre-transfer charger, 6... Transfer charger, 7... Separation charger, 1
0... Optical sensor, 15... Potential sensor

Claims (1)

[Claims] After the transferable toner image formed on the surface of the image carrier is electrostatically transferred to a transfer material in contact with the image carrier, means is provided for electrostatically separating the transfer material from the image carrier. 1. A transfer material separation device in an image forming apparatus comprising: at least a means for changing a discharge current of the electrostatic separation means in accordance with an image density at a leading edge of a transferred image.