JPH04125666A - Image forming device - Google Patents

Abstract

PURPOSE:To suppress the variation of positions at which a transfer material is attracted to a carrying sheet by providing the sheet extending extremely near to the transfer material attracting position, at the top end of a guide on a transfer material guide prepared at the front of the transfer material attracting position of the transfer material carrying sheet with which the transfer drum of a transfer device is wound. CONSTITUTION:A conductive roller 20 abutted to a carrying sheet 6a rotates at the same speed by following a transfer drum 6A by a frictional force between a added pressure due to a coil spring and the carrying sheet 6a. An upper guide 31 follows the attitude of a lower guide 22 when the transfer material is attracted to and drawn back from the carrying sheet 6a. Then, an insulated sheet 32 is provided at the top end of the upper guide 31. Therefore, the insulated sheet 32 can be extended extremely near to a transfer material attracting position Q, and the distribution of a corona at the front of the attracting position Q can be prevented, and the corona can be gathered to the conductive roller 20, by insulating the upper guide 31 from a corona electrifier 19 for attraction to protect it. Thus, the transfer material can be sucked and held at the attracting position Q of the transfer material carrying sheet 6a with the variation of position suppressed.

Description

Detailed Description of the Invention [1 Epithelial hill portion 11] The present invention relates to an image forming device such as an electrophotographic device or an electrostatic recording device, and in particular, toner images formed on an image carrier are transferred to a flexible portion of a transfer device. The present invention relates to an image forming apparatus that electrostatically transfers images onto a transfer material held on a transfer material carrying member to obtain an image on the transfer material.

For example, a color electrophotographic copying machine has 51! After a toner image is formed on an image carrier using a secondary photographic method, the toner image is transferred onto a transfer material by a transfer device equipped with a transfer drum to obtain an image on the transfer material.

The transfer device is equipped with the above-mentioned transfer drum as a transfer material holder, and the transfer drum has a transfer material carrying sheet usually made of a high resistance film as a flexible transfer material carrying member between both end frames of the cylinder. It is wrapped in a shape. The transfer material is supplied to the transfer drum of the transfer device, and by applying electrostatic adsorption force between the transfer material carrying sheet and the transfer material, it is attracted and held onto the transfer material carrying sheet and wound onto the transfer drum. (Refer to Japanese Patent Application Laid-Open No. 55-32079).

In a transfer device that holds a transfer material using this electrostatic adsorption method, the transfer material is attracted and held on the transfer material carrying sheet of the transfer drum at the transfer material adsorption position, and the inside of the transfer material carrying sheet is charged with a corona charge for adsorption. A conductor roller is placed on the outside facing the transfer material, and is movable into and out of contact with the transfer material. The transfer material is attracted to the transfer material carrying sheet by applying an electric charge with a polarity opposite to that of the toner constituting the toner image on the image carrier using a corona charger and a conductive roller.
Retained.

In a color electrophotographic copying machine, as described above, a plurality of transfer drums are used to transfer a toner image of each color onto the transfer material held on the transfer drum's carrier sheet each time it is formed on the image carrier. By performing multiple transfers on toner images of multiple colors during the process of rotating the transfer material, a color image is obtained in which toner images of multiple colors are superimposed on the transfer material.

The transfer material onto which the toner images of multiple colors have been transferred in this way is then used to weaken the electrostatic attraction force (Coulomb force) generated between the transfer material and the carrier sheet using a corona discharger. Then, by inserting a separation member between the transfer material and the carrier sheet, the transfer material is separated from the carrier sheet.

By the way, normally, the leading edge of the transfer material adsorbed and held on the transfer material carrying sheet is detected, and this is used as an image formation signal to form an image on the image carrier, and the toner image formed on the image carrier is The position of the transfer material and the transfer material on the transfer material carrying sheet are matched at the transfer position.

To explain the above positional relationship, the circumference of the image carrier between the exposure position and the transfer position on the image carrier is L, and the toner image is transferred between the sensor position that transmits the image forming signal and the toner image transfer position. If the circumference of the sheet is L2, and the circumference of the carrying sheet between the transfer material adsorption position and the toner image transfer position is,
The distance LL between the above transfer positions, adsorption positions, etc.
*, L-, there was a relationship such as L+ = Lm < Ls.

However, in recent years, miniaturization of equipment has become important in the copier market, and the transfer material supply section has also become smaller.
The direction is to place it close to the image carrier.

When the transfer material supply section is arranged in this way, it is necessary to provide a suction position for the transfer material close to the transfer position, and the relationship between the transfer position and suction position described above is as follows: L + = L t > L It becomes s.

In the above case, image formation on the image carrier has already started before the transfer material is attracted and held by the carrier sheet. Therefore, in order to match the positions of the toner image on the image carrier and the transfer material on the carrier sheet at the transfer position, the leading edge of the transfer material adsorbed and held on the transfer material carrier sheet is detected and detected. Unlike the case where an image is formed on an image carrier using the image forming signal as an image forming signal, it is necessary to reliably attract and hold the transfer material at a predetermined position on the carrier sheet.

However, the type of transfer material and its humidity and other conditions vary, and especially when the transfer material is curled paper, it is difficult to guide the transfer material from its tip to the suction position, and the suction position may be misaligned or uneven. tends to occur.

If there is any misalignment or variation in the suction position of the transfer material, the toner image and the transfer material will not match, resulting in variations in alignment (registration) in the image obtained by transferring the toner image onto the transfer material, and further transfer If there is a large deviation or variation in the material suction position, not only will the toner image be transferred onto the carrier sheet and stain it, but also the transfer material will not be separated properly at the rear transfer material separation section, resulting in a so-called jam. Cause.

Therefore, in view of the above-mentioned current situation, it is an object of the present invention to reliably adsorb and hold a transfer material at a predetermined position on a carrier sheet wound around a transfer drum of a transfer device, thereby improving the toner image formed on an image carrier. It is an object of the present invention to provide an image forming apparatus which can obtain a high-quality image without variation in alignment on a transfer material by transferring onto the transfer material, and which also enables miniaturization of the apparatus.

for The above object is achieved by an image forming apparatus according to the present invention.

In summary, the present invention includes a flexible transfer material holding member wound around a transfer material holding member of a transfer device, and a charge applying means provided inside the transfer material adsorption position, and a charge applying means provided outside opposite to the transfer material adsorption position. A charge injection means that contacts the transfer material is disposed on the transfer material holding member so as to be able to move toward and away from the transfer material, and the transfer material is charged by the charge applying means and the charge injection means, thereby holding the transfer material. Image formation in which a toner image formed on an image carrier is electrostatically attracted to and held by a member, and a toner image formed on an image carrier is transferred onto a transfer material held on the transfer material holding member to obtain an image on the transfer material. In the apparatus, a pair of transfer material guides that are movable toward and away from the transfer material holding member and have a gap that gradually narrows toward the suction position are provided outside the transfer material holding member and in front of the transfer material adsorption position. , the suction position is located on the extension line of the guide on the side closer to the transfer material holding member, and the front M is located near the tip of the guide on the side closer to the transfer material holding member of the pair of transfer material guides. The image forming apparatus is characterized in that an insulating sheet is provided protrudingly extending to just before the transfer material adsorption position, and the charge injection means is installed at the tip of the guide on the side far from the transfer material holding member.

According to one aspect of the present invention, the charge injection means is a conductive roller, and the insulating sheet has elasticity.

LIW Examples of the present invention will be described in detail below.

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention.

In FIG. 1, l is a photosensitive drum as an image carrier,
The photosensitive drum 1 is pivotally supported at its center and rotated in the direction of the arrow. Around the photosensitive drum 1, a primary charger 2, an optical system 3, and a developing device 4 are arranged opposite to the photosensitive drum 1 in the direction of rotation thereof.
, a pre-transfer charger 5 are arranged.

The primary charger 2 applies a uniform primary charge to the photosensitive drum 1, and the optical system 3 applies a color-separated optical image or a corresponding optical image to the surface of the photosensitive drum 1 at a predetermined timing.
Forms an electrostatic latent image. The optical system 3 uses a laser beam scanning device or the like. Further, the developing device 4 includes a photosensitive drum l.
The toner is movable in the tangential direction facing the surface of the toner, and is equipped with four developing units 4M, 4G, 4Y, and 4B, each containing magenta toner, cyan toner, yellow toner, and black toner. are doing. The developing device 4 has a developing device containing toner of a color corresponding to the electrostatic latent image formed on the photosensitive drum 1 facing the photosensitive drum 1, and the toner in the facing developing device is electrostatically exposed to light. The toner particles fly onto the surface of the drum 1 and adhere to the electrostatic latent image on the photosensitive drum 1, and the electrostatic latent image is developed and visualized as a toner image.

Further, around the photosensitive drum 1, as shown in FIG. 1, a static eliminator 27 for removing static charge from the surface of the photosensitive drum 1 and a cleaning blade 28 for removing toner are provided.

Further, on the right side of the photosensitive drum 1, a transfer device 6 is installed.
A is provided so as to be in contact with the surface of the photosensitive drum 1 or to be slightly separated from the surface. The transfer drum 6A is the fourth
As shown in the figure, a flexible transfer material holding member 6a is wound in a cylindrical shape between both cylindrical end frames 6b.

Inside the transfer material carrying sheet 6a of the transfer drum 6A, as shown in FIG. An adsorption corona charger 19 is disposed at a position on the upstream side in the rotational direction. A conductive roller 20 is disposed on the outside of the carrier sheet 6a, facing the corona charger 19, as a charge injection means.

At a position on the downstream side in the rotational direction of the transfer drum 6A from the transfer position, charge eliminating corona dischargers 10 and 11 are provided on the outside and inside of the transfer material carrying sheet 6a, respectively, and the transfer material P is disposed downstream thereof. Pressing rollers 12, 13 for separating from the carrier sheet 6a are provided, and a separating blade 14 is also provided in the vicinity thereof. If necessary, a corona discharger 29 is installed near the separation blade 14,
By performing AC corona discharge, when the transfer material P after which the toner images of multiple colors have been transferred is separated from the carrier sheet 6a, the toner image on the transfer material P is prevented from being disturbed by peeling discharge. It can be prevented.

When the transfer material P is separated from the carrier sheet 6a by the separating blade 14, it is conveyed to the fixing roller pair 18 via the conveyor 17 nearby, and is transferred onto the transfer material P at the transfer position by the fixing roller pair 18. The transferred toner image is fixed.

At a position on the downstream side of the separation blade 14 in the rotational direction of the transfer drum 6A, there is a brush roller 15 on the outside of the transfer material 6a for cleaning toner adhering to the outer surface (transfer material holding surface) of the carrier sheet 6a. If necessary, a corona discharger or a brush type static eliminator 16 for removing toner adhesion force (residual Coulomb force and van der Waals force) is provided inside the carrier sheet 6a.

In FIG. 1, the symbol L1 represents the circumference of the photosensitive drum 1 between the exposure position by the optical system 3 on the photosensitive drum 1 and the toner image transfer position by the transfer charger 7, and 2 represents the image forming apparatus. L3 indicates the circumferential length of the carrying sheet 6a between the transmitting sensor position and the toner image transfer position, and L3 indicates the circumferential length of the carrying sheet 6a between the transfer material adsorption position and the toner image transfer position.

In this image forming apparatus, the transfer material supply section is made smaller for the purpose of downsizing the apparatus, and accordingly, the transfer material suction position is also located close to the transfer position, and the Using the above distance L1 and Ls%L, the relationship Lt = l, s > Ls is established between them.

In the image forming apparatus with the above configuration, the surface of the photosensitive drum 1 is uniformly and primarily charged by the primary charger 2, and a light image that has first passed through, for example, a green filter is formed on the surface of the photosensitive drum 10 by the optical system 3. When the light is irradiated, an electrostatic latent image consisting mainly of the magenta component of the light image is formed. In synchronization with the above-described feeding of the electrostatic latent image due to the rotation of the photosensitive drum 1, the developing device 4 moves in a tangential direction with respect to the photosensitive drum 1, and transfers the developing device 4M containing magenta toner onto the photosensitive drum 1. Opposingly, the electrostatic latent image on the photosensitive drum 1 is developed with magenta toner, thereby forming a magenta toner image. The magenta toner image is transferred onto the transfer material P by the transfer device 6.

When the transfer of the magenta toner image is completed, the toner remaining on the surface of the photosensitive drum 1 is removed by a static eliminator 27 and cleaned by a blade 28, thereby cleaning the surface of the photosensitive drum 1. Then, in the same way, cyan, yellow,
Image formation in black color is performed.

On the other hand, the transfer material P to which the magenta toner has been transferred moves as the transfer drum 6 rotates while being attracted and held by the carrier sheet 6a, and passes through the corona dischargers 10 and 11. During this passage, the corona discharger 10.11
is not operated, and the pressing rollers 12 and 13 are also not activated.
a, and the brush roller 15 and the corona discharger or brush static eliminator 16 are also separated from the carrier sheet 6a. Further, the operation of the corona charger 19 and the contact of the conductive roller 20 with the transfer material P are completed before the leading edge of the toner image on the transfer material P reaches the positions of the corona charger 19 and the conductive roller 20. , when the transfer material P passes between these, no charge for adsorption is applied to the transfer material P.

As described above, the transfer material P can be transferred to the corona waste electric device 10 without disturbing the toner image carried thereon by Coulomb force.
11, passes between the corona charger 19 and the conductive roller 20, and then is sent to the transfer position again.

Thereafter, the cyan toner image, yellow toner image, and black toner image are transferred in the same manner.

Now, the transfer material adsorption section in the transfer device in the image forming apparatus of the present invention will be explained.

In FIG. 1, the transfer material P is fed from a paper feed section (not shown), and is placed in front of the transfer device 6 by a pair of registration rollers 21a, 21.
b, the transfer drum 6A is sent out at the same timing as the peripheral speed of the transfer drum 6A and at the same speed as the peripheral speed of the transfer drum 6A. At this time, the conductive roller 20 is brought into contact with the carrier sheet 6a.

The conductive roller 20 is rotatably mounted near the tip of the lower guide 22 of the pair of upper and lower transfer material guides 31 and 22 provided between the transfer drum 6A and the pair of registration rollers 21a and 21b. There is. The lower guide 22 is swingably supported around a fulcrum shaft 23 at its base end, and the contact of the conductive roller 20 near the tip with the support sheet 6a is caused by a coil spring 24 attached to the fulcrum shaft 23. This is performed by the biasing of the upper guide 31 located above the lower guide 22 and the displacement of the eccentric cam 30 provided on the upper guide 31 located above the lower guide 22.

The lower guide 22 shown in FIG.
The lower guide 22 shown in FIG.
It shows a retracted posture with a displacement of 0.

The conductive roller 20 that is in contact with the supporting sheet) 6a is pressed by the urging force of the coil spring 24 and the supporting sheet) 6a.
Due to the frictional force between the transfer drum 6A and the transfer drum 6A, the transfer drum 6A rotates at the same speed.

The upper guide 31 is rotatably supported by the shaft 33 of the eccentric cam 30, and is biased counterclockwise by its own weight or by a pressure spring (not shown). Upper guide 3
1 is when the transfer material P is attracted to the carrier sheet 6a;
It is possible to follow the posture of the lower guide 22 when it is retracted after being held. The biasing force of the upper guide 31 is made sufficiently smaller than the biasing force of the lower guide 22 due to the coil spring 24.

As shown in FIG. 3, an insulating sheet 32 is provided at the tip of the upper guide 31 and protrudes from the insulating sheet 32, and a protrusion 31a is provided on the lower surface of the tip of the upper guide 31.

The protrusion 31a comes into contact with the upper surface of the lower guide 23 to determine the gap between the upper and lower guides 31.23, and the gap between them gradually increases from the upper registration roller 21a toward the conductive roller 20. It is made to be narrower.

Referring to FIG. 3, the transfer material suction section in the present invention will be explained in more detail.

The upper surface of the lower guide 22, which serves as the transfer material passing surface, is in contact with the top of the conductive roller 20 on an extended line or is located at a position slightly lower than this, so that the upper guide 31 supports the transfer material on the transfer drum 6A. Sheet 6a and conductive roller 20
The insulating sheet 32 at the tip of the upper guide 31 extends to just before the suction position Q toward the transfer material suction position Q represented by the contact point with the conductive roller 20 and the supporting sheet 6a, so that there is a slight gap between the conductor roller 20 and the carrier sheet 6a. Open and position.

The upper guide 31 and the lower guide 22 are made of metal, and are grounded directly or via a varistor or the like to prevent frictional electrification with the transfer material P. For this reason, if the upper guide 31 and the lower guide 22 are installed close to the transfer material suction position Q without providing the insulating sheet 32 at the tip of the upper guide 31 and brought close to the carrier sheet 6a, the carrier sheet 6a This may damage the carrier sheet 6a, neutralize the charge on the carrier sheet 6a and weaken the suction force of the transfer material P, or cause uneven charging of the carrier sheet 6a or the transfer material P, causing a transfer failure. Furthermore, the upper guide 31 plays the role of a counter electrode for the adsorption corona charger 19 located inside the transfer material carrying sheet 6a, and the corona that should normally be concentrated on the conductive roller 20 is dispersed, and the transfer material is This will significantly weaken the adsorption power of P.

Furthermore, if the insulating sheet 31 is not provided at the tip of the upper guide 31 and the upper guide 31 and the lower guide 22 are installed away from the transfer material suction position Q, the transfer material P is restricted immediately before the suction position Q. This is particularly noticeable when the transfer material P is curled paper, etc., but in general, the path of the transfer material P is not constant, and the suction position of the transfer material P varies.

In contrast, in the present invention, an insulating sheet 32 is provided at the tip of the upper guide 31. In order to make this insulating sheet 32 elastic at the same time, for example, a Mylar sheet (trade name: Diaramy) with a thickness of several tens to several hundreds of mm is used.
(such as a luminaire).

According to such an insulating sheet 32, it can be extended to just before the transfer material adsorption position Q, and the upper guide 31
By insulating and protecting the corona from the suction corona charger 19, it is possible to prevent the corona from dispersing before the suction position 0 and concentrate the corona on the conductive roller 20. Also, insulating sheet 32
Even if the insulating sheet 32 is an elastic body and the extending direction of the insulating sheet 32 is directed toward the transfer material adsorption position Q, the movement of the carrying sheet 6a may be prevented even if Since the insulating sheet 32 is completely oriented in the escape direction, the supporting sheet 6a is not damaged by the insulating sheet 32.

Therefore, in the present invention, the transfer material P can be attracted and held at the attraction position Q of the transfer material carrying sheet 6a while suppressing positional variations. It becomes possible to realize an image forming apparatus that is

Menzu Koyoshi 1 As explained above, according to the image forming apparatus of the present invention,
The following effects can be obtained.

(1) A sheet extending to just before the transfer material suction position is provided at the tip of the upper and lower transfer material guides provided in front of the transfer material suction position of the transfer material carrying sheet wrapped around the transfer drum of the transfer device. Therefore, the transfer material can be guided to just before the suction position, and variations in the suction position of the transfer material to the carrier sheet can be suppressed. This is particularly effective when the transfer material is curled paper or the like.

(2) Since the sheet extending immediately before the transfer material adsorption position is an insulating sheet, the adsorption force of the transfer material due to adsorption and charging can be concentratedly applied to the transfer material at the adsorption position. Furthermore, by providing elasticity to the insulating sheet, damage to the carrier sheet can be reliably prevented.

(3) From the above, the position at which the transfer material is attracted to the transfer drum can be brought closer to the transfer position, and therefore the image forming apparatus can be downsized.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention. FIG. 2 is an explanatory diagram showing that the upper and lower transfer material guides provided in front of the transfer material adsorption section of the transfer device provided in the image forming apparatus of FIG. 1 are in the retracted position. FIG. 3 is an enlarged view showing a transfer material suction section of a transfer device provided in the image forming apparatus of FIG. 1. 4 is a perspective view showing a transfer drum of a transfer device provided in the image forming apparatus of FIG. 1. FIG. A a: Photosensitive drum; Transfer device: Transfer drum: Transfer material carrying sheet: Adsorption corona charger: Conductive roller lower guide, upper guide: Insulating seed

Claims (1)

[Scope of Claims] 1) A charge applying means is disposed inside the transfer material adsorption position of a flexible transfer material holding member wound on the transfer material holding body of the transfer device, and an electric charge applying means is disposed on the outside opposite to the transfer material adsorption position. A charge injection means that contacts the transfer material is disposed on the transfer material holding member so as to be able to come into and out of contact with the transfer material, and the transfer material is charged by the charge applying means and the charge injection means. electrostatically attracting and holding the toner image formed on the image carrier onto the transfer material held on the transfer material holding member;
In the image forming apparatus for forming an image on the transfer material, the transfer material holding member has a gap that is gradually narrowed toward the adsorption position at a position outside the transfer material holding member and in front of the transfer material adsorption position. A pair of transfer material guides that can be moved in and out of
The suction position is located on the extension line of the guide on the side closer to the transfer material holding member, and the transfer material is adsorbed at the tip of the guide on the side closer to the transfer material holding member of the pair of transfer material guides. An image forming apparatus characterized in that an insulating sheet is provided protrudingly extending to just before the transfer material holding member, and the charge injection means is installed near the tip of the guide on the far side of the transfer material holding member. 2) The image forming apparatus according to claim 1, wherein the charge injection means is a conductive roller. 3) The image forming apparatus according to claim 1 or 2, wherein the insulating sheet has elasticity.