JP3023975B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and more particularly to a flexible transfer of a toner image formed on an image carrier to a transfer apparatus. The present invention relates to an image forming apparatus that electrostatically transfers onto a transfer material held on a material supporting member to obtain an image on the transfer material.

2. Description of the Related Art For example, in a color electrophotographic copying machine, after a toner image is formed on an image carrier by an electrophotographic method, the toner image is transferred onto a transfer material by a transfer device equipped with a transfer drum, and is transferred onto the transfer material. The image has been obtained.

The transfer device is provided with the above-described transfer drum as a transfer material carrier, and the transfer drum is a cylindrical transfer material support sheet made of a high-resistance film as a flexible transfer material support member between cylindrical end frames. It is wound in a shape. The transfer material is supplied to the transfer drum of the transfer device, and is applied and held on the transfer material support sheet by applying an electrostatic attraction force between the transfer material support sheet and the transfer material, and wound on the transfer drum. (See JP-A-55-32079).

In a transfer device that holds a transfer material by this electrostatic suction method, the transfer material is sucked onto a transfer material carrying sheet of a transfer drum,
At the holding position of the transfer material to be held, an adsorbing corona charger is arranged on the inner side of the transfer material carrying sheet, and a detachable conductive roller for rolling and contacting the transfer material is arranged on the outer side in opposition to the corona charger. . The transfer material is adsorbed onto the transfer material carrying sheet by applying a charge having a polarity opposite to that of the toner constituting the toner image of the image carrier with a corona charger and a conductive roller.
Will be retained.

In a color electrophotographic copying machine, a plurality of transfer drums are used to transfer a toner image of each color on an image carrier on a transfer material held on a support sheet of a transfer drum as described above. By performing the multi-transfer on the toner images of a plurality of colors in the process of rotating, a color image obtained by superimposing the toner images of a plurality of colors on the transfer material is obtained.

The transfer material onto which the toner images of a plurality of colors have been transferred in this manner is then weakened by electrostatic attraction (Coulomb force) generated between the transfer material and the supporting sheet using a corona discharger. Then, the transfer material is separated from the support sheet by inserting the separation member between the transfer material and the support sheet.

By the way, usually, the leading end of the transfer material adsorbed and held on the transfer material carrying sheet is detected, and this is used as an image forming signal to form an image on the image carrier, thereby forming a toner image formed on the image carrier. 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 positional relationship, the circumferential length of the image carrier between the exposure position and the transfer position on the image carrier and L _1, between the sensor position and the toner image transfer position for transmitting the image formation signal the circumference of the carrying sheet and L _2, when the peripheral length of the carrying sheet between the transfer material sucking position and the toner image transfer position and L _3, between such transfer positions and the suction positions of the above, these distances L ₁ ,
Using L ₂ and L ₃ , there was a relationship such as L ₂ = L ₂ <L ₃ .

However, in recent years, in the copier market, downsizing of the device has been regarded as important, and the transfer material supply unit has also been reduced in size. is there.

With this arrangement of the transfer material supply unit, the suction position of the transfer material needs to be provided close to the transfer position, and the relationship between the transfer position and the suction position described above is L ₁ = L ₂ > L It becomes ₃ .

In the above case, the image formation is already started on the image carrier before the transfer material is adsorbed and held on 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 end of the transfer material adsorbed and held on the transfer material carrier sheet is detected. Unlike the case where an image is formed on an image carrier using an image forming signal as an image forming signal, it is necessary to surely adsorb and hold the transfer material at a predetermined position of the carrier sheet.

However, the type of transfer material and the state of its humidity and the like also vary, and particularly when the transfer material is curled paper, etc., it is difficult to guide the transfer material to the suction position from the leading end, and the suction position is displaced or uneven. Tends to occur.

If the transfer material is misaligned or fluctuated, the position of the toner image does not match the position of the transfer material, and the image obtained by transferring the toner image onto the transfer material (registration) fluctuates. If the deviation or dispersion of the material adsorption position is large, not only is the toner image transferred onto the carrier sheet to stain the carrier sheet, but also a transfer material separation failure at the rear transfer material separation unit, so-called jam occurs. Cause.

Therefore, in view of the above situation, it is an object of the present invention to securely adsorb and hold a transfer material at a predetermined position on a carrier sheet wound around a transfer drum as a transfer material carrier of a transfer device, and By transferring the toner image formed on the transfer material,
It is an object of the present invention to provide an image forming apparatus capable of obtaining a high-quality image on a transfer material with no variation in alignment and capable of reducing the size of the apparatus.

Means for Solving the Problems The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image carrier for carrying an image, a transfer material carrier for carrying a transfer material, and a suction charging unit for electrostatically attracting the transfer material to the transfer material carrier at a suction position. Provided on the surface side of the transfer material supported by the transfer material support,
A first guide member that guides the transfer material to the suction position; and a second guide member that is provided on a side of the transfer material opposite to a surface of the transfer material that is supported by the transfer material carrier, and guides the transfer material to the suction position. An image forming apparatus having a guide member and transferring an image on the image carrier to a transfer material adsorbed and carried on the transfer material carrier by the attraction / charging means; The image forming apparatus is characterized in that the first guide member includes an insulating member at a tip closer to the suction position in order to regulate a formed suction electric field.

According to one aspect of the present invention, the suction charging unit is provided on a side of the transfer material carrier that supports the transfer material, and is a suction member that can be brought into contact with and separated from the transfer material carrier at the suction position. A charger provided to face the adsorbing member via a material carrier, and charging the transfer material carrier. When the transfer material is adsorbed to the transfer material carrier by the adsorption charging means, The member contacts the transfer material.

According to another aspect of the present invention, the suction member is a roller having conductivity, and the suction member is a second roller.
In the vicinity of the tip of the guide member.

According to another aspect of the present invention, the insulating member has elasticity, and the insulating member is a sheet.

According to still another aspect of the present invention, the first guide member includes a rigid body, and the insulating member is provided at a distal end of the rigid body closer to the suction position.

Examples Hereinafter, examples of the present invention will be described in detail.

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

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

The primary charger 2 applies uniform primary charging to the photosensitive drum 1, and the optical system 3 applies a color-separated light image or a light image L corresponding thereto to the surface of the photosensitive drum 1 at a predetermined timing, and An electrostatic latent image is formed. A laser beam scanning device or the like is used for the optical system 3. The developing device 4 is movable in the tangential direction thereof facing the surface of the photosensitive drum 1, and includes four developing devices that specifically store magenta toner, cyan toner, yellow toner, and black toner as developers. It has 4M, 4C, 4Y and 4B. The developing device 4
A developing device containing a toner of a color corresponding to the electrostatic latent image formed on the photosensitive drum 1 faces the photosensitive drum 1, and the toner of the facing developing device electrostatically flies on the surface of the photosensitive drum 1. Then, the electrostatic latent image adheres to the electrostatic latent image on the photosensitive drum 1 and is developed to be visualized as a toner image.

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

On the right side of the photosensitive drum 1, a transfer device 6 is provided.
6A is provided in contact with or slightly away from the surface of the photosensitive drum 1. As shown in FIG. 4, the transfer drum 6A is formed by winding a transfer material carrying sheet 6a as a flexible transfer material carrying body between cylindrical end frames 6b in a cylindrical shape.

Inside the transfer material carrying sheet 6a of the transfer drum 6A,
As shown in FIG. 1, a corona charger 7 is provided at a transfer position facing the photosensitive drum 1, and a suction corona charger 19 is provided at a position upstream of the transfer position in the rotation direction of the transfer drum 6A. Are arranged. A conductive roller 20 is disposed outside the support sheet 6a as a charge injection unit, facing the corona charger 19.

At positions downstream of the transfer position in the rotation direction of the transfer drum 6A, corona dischargers 10 and 11 for static elimination are disposed outside and inside the transfer material supporting sheet 6a, respectively. Pressing roller 1 for separating from carrier sheet 6a
2 and 13 are provided, and a separating blade 14 is further provided in the vicinity thereof. Separation blade 14 if necessary
A corona discharger 29 is installed in the vicinity of the transfer sheet P, and by performing an AC corona discharge, when the transfer material P having finished transferring the toner images of a plurality of colors is separated from the supporting sheet 6a, the transfer material P It is possible to prevent the toner image on P from being disturbed.

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

At a position downstream of the separation blade 14 in the rotation direction of the transfer drum 6A, a brush for cleaning the toner attached to the outer surface (transfer material holding surface) of the support sheet 6a outside the transfer material support sheet 6a. A roller 15 is provided, and if necessary, a corona discharger or a brush type static eliminator 16 for removing the adhesive force (residual Coulomb force and Van der Waals force) of the toner is provided inside the support sheet 6a.

Note that in Figure 1, the reference numeral L ₁ is a circumferential length of the photosensitive drum 1 between the toner image transfer position by the transfer charger 7 and the exposure position by the optical system 3 on the photosensitive drum 1, L ₂ is an image forming signal the circumference of the carrying sheet 6a between the sensor position and the toner image transfer position for transmitting a, L ₃ denotes a circumferential length of the carrying sheet 6a between the transfer material sucking position and the toner image transfer position. In the present image forming apparatus, the transfer material supply unit is downsized for the purpose of downsizing the apparatus, and the suction position of the transfer material is also provided close to the transfer position. The distance L ₁ , L ₂ , and L ₃ are used to establish a relationship of L ₁ = L ₂ > L ₃ .

In the image forming apparatus having the above configuration, the surface of the photosensitive drum 1 is uniformly primary-charged by the primary charger 2, and the optical system 3 firstly passes the optical image on the surface of the photosensitive drum 1 through a green filter, for example. When L is irradiated, an electrostatic latent image mainly composed of the magenta component of the light image L is formed.
The developing device 4 moves in a tangential direction with respect to the photosensitive drum 1 in synchronization with the feeding of the electrostatic latent image due to the rotation of the photosensitive drum 1 and transfers the developing device 4M containing magenta toner to the photosensitive drum 1. In opposition, 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 photosensitive drum 1
The toner remaining on the surface of the photosensitive drum 1 is neutralized by a static eliminator 27 and cleaned by a blade 28, thereby cleaning the surface of the photosensitive drum 1. Thereafter, images of cyan, yellow, and black are formed in the same manner.

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 adsorbed and held on the support sheet 6a, and passes between the corona dischargers 10 and 11 and below. At this time, the corona dischargers 10 and 11 are not operated, the pressing rollers 12 and 13 are also separated from the support sheet 6a, and the brush roller 15 and the corona discharger or the brush type static eliminator 16 are also separated from the support sheet 6a. I'm separated. Further, the operation of the suction corona charger 19 as the suction charging means and the contact of the conductive roller 20 as the suction charging means with the transfer material P are caused by the tip of the toner image on the transfer material P.
The transfer is completed before the transfer material P reaches the position of the conductive roller 20, and when the transfer material P passes between them, the charge for adsorption is not applied to the transfer material P.

As described above, the transfer material P is transferred to the corona discharger 10 without disturbing the toner image carried by the Coulomb force.
After 11 or less, the sheet passes through the space between the corona charger 19 and the conductive roller 20, and is again sent to the transfer position. Then, in the same manner, a cyan toner image, a yellow toner image,
The transfer of the black toner image is performed.

Now, the transfer material suction unit in the transfer device in the image forming apparatus of the present invention will be described.

In FIG. 1, a transfer material P is fed from a paper feed unit (not shown), and is transferred by a pair of registration rollers 21a, 21a in front of the transfer device 6 at a timing when the transfer material P reaches a predetermined position on a supporting sheet 6a of a transfer drum 6A. It is sent out at the same speed as the peripheral speed of the drum 6A. At this time, the conductive roller 20 contacts the support sheet 6a.

The conductive roller 20 is a pair of the transfer drum 6A and the registration roller.
A pair of upper and lower transfer material guides provided between 21a and 21b
It is rotatably mounted near the tip of the lower guide 22 of 31 and 22. Lower guide 22 as a second guide member
Is supported so as to be swingable about a fulcrum shaft 23 at the base end thereof, and the contact of the conductive roller 20 near the tip with the support sheet 6a is urged by a coil spring 24 attached to the fulcrum shaft 23. 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 posture for suction and holding is shown above, and the lower guide 22 shown in FIG. 2 shows the retracted posture due to the displacement of the eccentric cam 30 after the suction and holding of the transfer material P.

The conductive roller 20 in contact with the support sheet 6a rotates at the same speed following the transfer drum 6A by the pressing force of the coil spring 24 and the frictional force with the support sheet 6a.

The upper guide 31 is rotatably supported by the shaft 33 of the eccentric cam 30, and is urged counterclockwise by its own weight or a pressing spring (not shown). The upper guide 31
It is possible to follow the posture of the lower guide 22 when the transfer material P is attracted to the support sheet 6a and when the transfer material P is retracted after being attracted and held. Upper guide
The urging force of 31 is sufficiently smaller than the urging force of the lower guide 22 by the coil spring 24.

As shown in FIG. 3, an insulating sheet 32 protruding from the upper guide 31 is provided at the distal end of the upper guide 31.
A projection 31a is provided on the lower surface of the distal end portion 31. Projection 3
1a is in contact with the upper surface of the lower guide 22 and the upper and lower guides 31, 22
The gap between them is determined, and the gap between these is gradually narrowed from the upper registration roller 21a toward the conductor roller 20.

With reference to FIG. 3, the transfer material suction portion in the present invention will be described in more detail.

The upper surface of the lower guide 22, which becomes the transfer material passage surface, is in contact with the top of the conductive roller 20 or slightly lower than the top of the conductor roller 20 on the extension line, so that the upper guide 31 as the first guide member is moved. Toward the transfer material suction position Q represented by the contact point between the transfer material carrying sheet 6a of the transfer drum 6A and the conductive roller 20, the insulating sheet 32 at the tip of the upper guide 31 extends to just before the suction position Q, and It is located with a slight gap between the roller 20 and the supporting sheet 6a.

The upper guide 31 and the lower guide 22 are made of metal, and the transfer material P
In order to prevent frictional electrification with the ground, it is grounded directly or via a varistor or the like. For this reason, if the upper guide 31 and the lower guide 22 are installed close to the transfer material suction position Q without being provided with the insulating sheet 32 at the distal end of the upper guide 31 so as to approach the carrier sheet 6a, the carrier sheet 6a Damage the transfer sheet P, and reduce the electrostatic force of the transfer sheet P by discharging the carrier sheet 6a.
Further, charging unevenness occurs on the carrier sheet 6a or the transfer material P, which may cause a transfer failure. Further, the upper guide 31 plays the role of the counter electrode of the suction corona charger 19 inside the transfer material supporting sheet 6a, and disperses the corona that should be concentrated on the conductive roller 20 and the transfer material. P
Will be significantly reduced.

In the state where the insulating sheet 31 is not provided at the end of the upper guide 31, the upper guide 31 and the lower guide 22 are moved to the transfer material suction position Q
If the transfer material P is placed away from the suction position Q, there is no means for regulating the transfer material P immediately before the suction position Q, and this is particularly remarkable when the transfer material P is curled paper or the like. The adsorption position of P varies.

On the other hand, in the present invention, the insulating sheet 32 is provided at the tip of the upper guide 31. This insulating sheet 32 has a thickness of several tens to several hundreds mm in order to have elasticity at the same time.
Mylar sheet (trade name dialamie, lumirror, etc.).

According to such an insulating sheet 32, this can be extended to just before the transfer material suction position Q, and the upper guide 31 is insulated and protected from the suction corona charger 19, so that the upper guide 31 is located just before the suction position Q. Corona dispersion is prevented and the corona is
You can concentrate on Further, even if the insulating sheet 32 comes into contact with the transfer material carrying sheet 6a, the insulating sheet 32 is an elastic body, and the extending direction of the insulating sheet 32 is directed to the transfer material adsorbing position Q, and Since the direction of movement of the sheet 6a is completely in the escape direction, the insulating sheet 32 does not damage the support sheet 6a.

Therefore, in the present invention, the transfer material P can be sucked and held at the suction position Q of the transfer material supporting sheet 6a while suppressing the variation in the position. Therefore, the image forming apparatus in which the suction position Q is close to the transfer position, that is, Thus, a simplified image forming apparatus can be realized.

Effects of the Invention As described above, according to the image forming apparatus of the present invention, the attraction charging unit that electrostatically attracts the transfer material to the transfer material carrier such as the transfer drum at the suction position, and the attraction of the transfer material A first guide member for guiding a transfer material to the suction position, and a second guide member for guiding the transfer material to the suction position. Is provided with an insulating member at the end closer to the suction position, the following effects can be obtained. That is, (1) a sheet extending to the end of the guide above the upper and lower transfer material guides provided in front of the transfer material suction position of the transfer material carrying sheet wound around the transfer drum of the transfer device, immediately before the transfer material suction position. Since the transfer material is provided, the transfer material can be guided to a position immediately before the suction position, and the variation in the suction position of the transfer material to the supporting sheet can be suppressed. This is particularly effective when the transfer material is curl paper or the like.

(2) Since the sheet extending to the position immediately before the transfer material suction position is an insulating sheet, the suction force of the transfer material by suction charging can be applied intensively to the transfer material at the suction position. Also, by making the insulating sheet elastic, it is possible to reliably prevent the supporting sheet from being damaged.

(3) From the above, the adsorption position of the transfer material to the transfer material carrier such as the transfer drum can be made closer to the transfer position,
Therefore, the size of the image forming apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the image forming apparatus of the present invention. FIG. 2 is an explanatory view showing that the upper and lower transfer material guides provided at a position before the transfer material suction unit of the transfer device provided in the image forming apparatus of FIG. 1 are in a retracted posture. FIG. 3 is an enlarged view showing a transfer material suction portion of a transfer device provided in the image forming apparatus of FIG. FIG. 4 is a perspective view showing a transfer drum of a transfer device provided in the image forming apparatus of FIG. 1: Photosensitive drum 6: Transfer device 6A: Transfer drum 6a: Transfer material carrying sheet 19: Suction corona charger 20: Conductive roller 22: Lower guide 31: Upper guide 32: Insulating seed

Claims (7)

(57) [Claims] An image carrier for carrying an image; a transfer material carrier for carrying a transfer material; an adsorption charging means for electrostatically adsorbing the transfer material to the transfer material carrier at a suction position; A first guide member provided on the surface of the transfer material carrying member for guiding the transfer material to the suction position; and a side opposite to the surface of the transfer material supported on the transfer material carrying member. And a second guide member for guiding the transfer material to the suction position, wherein the image on the image carrier is transferred to the transfer material adsorbed and carried on the transfer material carrier by the suction charging unit. In the image forming apparatus for transferring, the first guide member is provided with an insulating member at a tip end closer to the suction position in order to regulate a suction electric field formed by the suction charging unit at the suction position. Image forming apparatus. 2. An adsorption member provided on a side of the transfer material carrier for supporting a transfer material, the adsorption member being capable of coming into contact with and separating from the transfer material carrier at the adsorption position; A charging device that is provided to face the adsorbing member through the intermediary of the transfer member, and charges the transfer material carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus contacts the material. 3. The image forming apparatus according to claim 1, wherein said suction member is a roller having conductivity. 4. The image forming apparatus according to claim 2, wherein said suction member is provided near a tip of said second guide member. 5. The apparatus according to claim 1, wherein said insulating member has elasticity.
5. The image forming apparatus according to any one of items 4. 6. The image forming apparatus according to claim 5, wherein said insulating member is a sheet. 7. The image forming apparatus according to claim 5, wherein the first guide member has a rigid body, and the insulating member is provided at a tip of the rigid body closer to the suction position.