JPH0572914A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image with high quality by reducing the shock of a transfer material carrying member or the change of rotational load occurring when an electrical conductive roller being a transfer material attraction means is made to abut or retreated with respect to the transfer material carrying member such as the transfer material carrying sheet of a transfer drum, thereby preventing color slippage from occurring, further preventing the electrical conductive roller from being stained with toner. CONSTITUTION:A cylindrical member 35 is axially supported on the identical shaft of the supporting point 30 of a pressing spring 222 and a torque limiter 38 is concentrically fitted to the cylindrical member 35. By the limiter 38, rotational driving transmitted from a resist roller 21 by a belt 37 is transmitted to the cylindrical member 35 by prescribed torque. Besides, the cylindrical member 35 is provided with a projection part 36 and the spring 222 is pressed in a direction shown by an arrow by the projection part 36 while the driving from the roller 21 is transmitted to the cylindrical member 35.

Description

Detailed Description of the Invention

[0001]

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 visible image such as a toner image formed on an image carrier on a transfer material carrying member. The present invention relates to an image forming apparatus that obtains an image by transferring the image onto a transfer material held by.

[0002]

2. Description of the Related Art For example, in a color electrophotographic copying machine, an image is obtained by forming a toner image on an image carrier such as a photosensitive drum and transferring the toner image onto a transfer material as a recording material. Usually, the transfer material is carried and carried by a transfer material carrying member, usually a transfer drum constituted by winding a transfer material carrying sheet such as a high resistance film. That is, the transfer material supplied to the transfer drum is
At the transfer material supply position, electrostatic attraction is exerted between the transfer material carrying sheet and the transfer material, and the transfer material carrying sheet is wound around the transfer material carrying sheet by being fixedly held around the transfer drum (JP-A-55). -32079). Then, by rotating the transfer drum, the transfer material is transported to the transfer position a plurality of times, and the toner images of a plurality of colors are electrostatically transferred from the image carrier to the surface of the transfer material by multiple transfer.

The transfer material is fed from a paper feeding section and sent to a suction position on the transfer material carrying sheet at a predetermined timing by a pair of conveying rollers. At the adsorption position, a corona charger is provided on the back surface of the transfer material carrying sheet, and a conductor roller (charge injection roller) is provided on the transfer material carrying sheet to make contact with the transfer material to be attracted and held. Then, by applying an electric charge having a polarity opposite to that of the toner image to the transfer material, the transfer material is adsorbed on the carrier sheet.

Here, the conductor roller is driven by the transfer drum and contacts the transfer drum to suck and convey the transfer material at the same conveying speed as the transfer drum, that is, the transfer material carrying sheet.

[0005]

However, in the above-mentioned conventional example, since the conductor roller directly contacts the transfer drum, the impact of this contact causes the image formation (latent image formation) in the transfer drum. The sensor or sensor flag that issues the start signal vibrates. When this happens, only the latent image of the first color of the multi-color copy is started from the position deviated from the normal position, and as a result, only the first color in the transfer material transporting direction is spread over the entire area of other colors. It will be displaced.

In recent years, in the copying machine market, miniaturization of the apparatus has been emphasized, and the feeding portion of the transfer material has also been miniaturized, and it tends to be arranged close to the photosensitive drum. or,
The above-mentioned image forming start signal sensor position and the contact position (adsorption position) of the conductor roller with respect to the transfer drum are close to each other. Therefore, the influence of vibration due to the contact shock of the conductor roller with respect to the transfer drum directly forms an image. By shifting the start timing of the signal, the color shift becomes more noticeable.

Further, with respect to the axial direction of the transfer material carrying sheet (which is also the axial direction of the conductor roller), a large number of continuous copies are made on the transfer material having a size smaller than the size of the transfer material carrying sheet, that is, a narrow width. Then, the toner is gradually accumulated in the non-image portion of the transfer material carrying sheet that does not adsorb the transfer material, and so-called "fogging" occurs. Then, when the conductor roller comes into contact with the transfer material carrying sheet in an attempt to adsorb the transfer material on the transfer material carrying sheet, a part of the fog toner in the non-image area is transferred to the conductor roller.

Subsequently, when a copy is to be obtained with a large-sized transfer material, the image surface of the transfer material is stained by the fog toner transferred to the conductor roller.

Further, in order to keep the toner density of the developer at an appropriate level, a method of forming a patch image of a constant density level on the photosensitive drum, reading this density, and controlling the toner density causes a part of the toner of the patch image to be lost. The transfer material carrying sheet is transferred to the conductor roller. Therefore, a cleaning member for cleaning the conductor roller is provided.

However, with this cleaning member,
The rotation load of the conductor roller increases. For this reason, when the conductive roller comes into contact with the transfer drum and is driven, a load variation is applied to the rotation of the transfer drum when the contact is made or when the conductive roller is retracted. For this reason, it is necessary to reduce the pressure applied to the transfer drum by the conductor roller in order to reduce the shock and fluctuations in the rotational load when the conductor roller is in contact with the transfer drum or when retracted. If you do too much,
Due to the reduction of the frictional force between the transfer drum and the conductor roller and the rotation load of the cleaning member on the conductor roller, it is difficult to rotate the conductor roller, and cleaning cannot be performed sufficiently.

Therefore, an object of the present invention is to provide a transfer material holding member, such as a transfer material holding sheet of a transfer drum, with which a conductive material roller, which is a transfer material suction means, comes into contact.
Alternatively, it is possible to obtain a high-quality image by reducing a shock and a rotational load fluctuation of the transfer material supporting member which occur at the time of retreating to prevent color misregistration and also preventing the conductive roller from being soiled with toner. An image forming apparatus is provided.

[0012]

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention forms an image by forming a visible image on an image carrier and transferring the image to a transfer material that is electrostatically adsorbed to a transfer material carrying member by an adsorbing means. In the image forming apparatus, the suction means includes an abutting member that abuts the transfer material carrying member, a pressurizing means that presses the abutting member against the transfer material carrying member, and the transfer of the abutting member. An image forming apparatus comprising: a pressing force control unit that changes a pressing force applied to a material carrying member at a predetermined timing.
According to a preferred aspect, the pressurizing force control means has a pressure increasing mechanism for increasing the pressurizing force at a predetermined timing or a depressurizing mechanism for decreasing the pressurizing force at a predetermined timing. Further, the suction means has a contacting / separating means for contacting / separating the contact member with the transfer material carrying member.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

FIG. 1 schematically shows a sectional structure of a color electrophotographic copying machine which is an embodiment of the present invention. In this embodiment, the photosensitive drum 1, which is an image carrier, is rotationally driven in the arrow direction. A primary charger 2, an optical system 3, a developing device 4, and a pre-transfer charger 5 are arranged in the rotational direction of the photosensitive drum 1 so as to face the outer peripheral surface of the photosensitive drum 1. The primary charger 2 applies a uniform amount of charge to the photosensitive drum 1, and the optical system 3 applies an optical image color-separated at a predetermined timing or a light ray L corresponding thereto to the surface of the photosensitive drum 1 to generate an electrostatic latent image. Form an image. A laser beam scanning device or the like is used for the optical system 3.

Further, the developing device 4 is a horizontal moving type developing device which moves in the tangential direction so as to face the surface of the photosensitive drum 1 in this embodiment, and is a magenta color developing agent, a cyan color developing agent or a yellow color developing agent. , Four developing devices 4M, 4C, 4Y and 4BK for separately storing the four color developer toners of black color developer. The developing device 4 makes the developing device selected corresponding to the irradiation of the light image of the selected color or the light beam L corresponding thereto by the optical system 3 face the photosensitive drum 1,
A toner image is formed on the surface of the photosensitive drum 1.

Next, a transfer device 6 is arranged on the downstream side of the developing device 4 in the moving direction of the photosensitive drum 1 so as to face the photosensitive drum 1. In this embodiment, the transfer device 6 includes a transfer material holding member that holds the transfer material between the cylindrical end frames 6b, 6b, that is, the transfer material holding sheet 6 as schematically shown in FIG.
The transfer drum 6 is formed by winding a in a cylindrical shape. Usually, the transfer material carrying sheet 6a is a high resistance film such as PV.
It is made of a flexible film material having a thickness of about 100 to 200 μm made of DF or PET. Further, as shown in FIG. 1, at the image forming position facing the photosensitive drum 1, that is, at the transfer position, on the side opposite to the transfer material holding surface of the transfer material carrying sheet 6 a, that is, inside the transfer drum 6. A corona charger 7 for transfer is disposed in the.

As described above, by the photosensitive drum 1, the process means 2, 3, 4, 5 for forming a toner image on the photosensitive drum as the image forming means, and the corona charger 7 for transferring the toner image from the photosensitive drum to the transfer material. An image is formed on the transfer material.

The transfer drum 6 is rotationally driven in the direction of the arrow,
On the upstream side of the transfer position where the corona charger 7 is arranged,
A suction corona charger 19 is provided on the opposite side of the transfer material holding surface of the transfer material carrying sheet 6a, that is, inside the transfer drum 6, and
A grounded conductor roller (charge injection roller) 20 is arranged as a charge injection means so as to face the transfer material holding surface. In this way, the transfer material is electrostatically adsorbed to the carrying sheet 6a by the adsorbing means 19 and 20, so that the transfer drum 6
It is no longer necessary to provide a gripper for gripping the transfer material.

Further, on the downstream side of the transfer position, corona dischargers 10 and 11 for static elimination are arranged with the transfer material carrying sheet 6a interposed therebetween, and the transfer held by the transfer material carrying sheet 6a is performed. Pressing rollers 12 and 13 for separating the material P by deforming the transfer material carrying sheet 6a.
Are arranged so as to sandwich the transfer material carrying sheet 6a, and a separation claw 14 is arranged in the vicinity thereof. Further on the downstream side is a brush roller 15 for cleaning the holding surface of the transfer material carrying sheet 6a, and if necessary, a corona discharger or a brush type remover for removing the adhesive force (residual Coulomb force and van der Waals force). An electric appliance 16 is provided.

Further, a fixing device 18 consisting of a pair of fixing rollers is arranged adjacent to the transfer drum 6, and on the transfer material P separated from the transfer material carrying sheet 6a by the separating claw 14 and conveyed by the conveyor 17. To fix the toner image of.

Further, around the photosensitive drum 1, as shown in FIG. 1, a static eliminator 27 for removing electrostatic charges on the surface of the photosensitive drum 1 and a cleaning blade 28 for removing residual toner are arranged. Further, if necessary, in the vicinity of the separation claw 14, for the purpose of preventing image disturbance due to peeling discharge that occurs when the transfer material P is separated from the transfer material carrying sheet 6a,
It is advisable to install a corona discharger 29 for AC corona discharge.

With this structure, the surface of the photosensitive drum 1 is uniformly charged by the primary charger 2, and then the optical system 3 is charged.
Thus, for example, when the photosensitive drum is irradiated with a color image that has passed through a green filter, a latent image mainly composed of a magenta component of the color image is formed. In synchronism with the feed of the latent image, the developing device 4 moves in the tangential direction with respect to the photosensitive drum 1 and contains the magenta developer.
M is made to face the photosensitive drum 1, and a magenta toner image is formed on the photosensitive drum 1.

On the other hand, the transfer material P is introduced into the upper guide 100 and the lower guide 22 by the function of registration rollers (transfer material transfer rollers) 21 and 21 'as a transfer means for transferring the transfer material to the transfer drum. Guided by the upper and lower guides, the conductor roller 20 and the suction corona charger 19 are supplied to the suction position where they face each other along the surface of the transfer material carrying sheet 6a.

According to this embodiment, the lower guide 22 has the fulcrum 3
It is swingably supported about 0 and is normally urged clockwise in FIG. 1 by a pressing means, that is, a coil spring 222 as an elastic member. The conductor roller 20 is rotatably attached to the tip of the lower guide 22. Therefore, when the lower roller 22 swings around the fulcrum 30 by the contacting / separating means, that is, the eccentric cam 221, the conductor roller 20 is rotationally driven in the direction of the arrow by the driving means (not shown), and the transfer material carrying sheet. 6a moves away from and contacts. The eccentric cam 221 is driven at the same timing as the supply timing of the transfer material P, and when the transfer material P is supplied to the suction position, the conductor roller 20 moves the transfer material carrying sheet 6a as shown in FIG. Is positioned in contact with.

In this embodiment, at a position where the transfer material P is supplied to the transfer material carrying sheet 6a, that is, in the vicinity of the suction position, an elastic sheet 24 of 150 μm and a sheet are provided on the surface opposite to the holding surface of the transfer material carrying sheet 6a. The distortion correcting means 23 including the supporting member 25 is provided and the transfer material carrying sheet 6a is provided.
Is pressed and held from the inside to correct or prevent mechanical deformation of the transfer material carrying sheet 6a by the brush roller 15 or the like or deformation by electrostatic force by the corona charger 19.

In this case, the elastic force of the strain correcting means 23 is in the direction in which the transfer material carrying sheet 6a is stretched, that is, from the free end of the elastic sheet 24 in contact with the transfer material carrying sheet 6a.
It is preferable that the direction toward the support portion of 4 is the opposite direction to the moving direction of the transfer material carrying sheet, so that the distortion of the transfer material carrying sheet 6a in the thrust direction (longitudinal direction of the transfer drum) can be reduced. .. Further, as shown in the figure, by providing the elastic sheet 24 so as to cover the discharge area where the shield member of the corona charger 19 is open, the circumferential discharge distribution of the charger 19 can be regulated. It is possible.

With the above-described structure, the transfer material P is supplied to the transfer material adsorption position where the conductor roller 20 is located, and then electrostatically adsorbed and held on the transfer material carrying sheet 6a by the corona charger 19. It is sent to the transfer position where the transfer charger 7 is located, which faces the photosensitive drum 1. Of course, the registration roller 2
The transfer material feeding timings 1 and 21 'are synchronized with the latent image forming timing by the optical system 3, and they coincide at the transfer position.

According to this embodiment, the transfer material transport guide 223 is provided so as to be located between the transfer position and the position where the transfer material is supplied to the transfer material carrying sheet 6a or the suction position. The transfer material transport guide 223 is formed integrally with the lower guide 22. Therefore, the transfer material P is not adsorbed and held by the transfer material carrying sheet 6a at the adsorbing position due to a change in the environment, a change in the paper thickness of the transfer material P, etc., and a state in which the tip of the transfer material P hangs down in the direction of gravity occurs. Also in this case, the transfer material P is guided by the transfer material transport guide 223 onto the transfer material carrying sheet 6a, and is transferred to the transfer position without being jammed. The transfer material transport guide 2
Similarly to the lower guide, the reference numeral 23 rotates about the fulcrum 30, and when the conductor roller 20 is in contact with the surface of the transfer material carrying sheet 6a, the thickness of the transfer material carrying sheet 6 is smaller than that of the transfer material carrying sheet 6a. It is positioned and arranged so as to be separated by a slightly larger gap d.

At the transfer position, the transfer corona charger 7 operates to generate a transfer electric field, and the toner image on the photosensitive drum 1 is transferred onto the transfer material P by the electric charge applied to the transfer material carrying sheet 6a.

Further, according to this embodiment, as shown in FIG. 2, the eccentric cam 221 is driven to the bottom dead center by the driving means at the timing when the rear end of the transfer material P passes through the conductor roller 20. Is driven to rotate. As a result, the lower guide 22 is biased by the eccentric cam 221 and rotates counterclockwise about the fulcrum 30, and as a result, the conductor roller 20 and the transfer material transport guide 223 largely retract from the transfer material transport sheet 6a. To do.

FIG. 3 is an enlarged detailed view of the portion K in FIG.
The main part of the present invention will be described with reference to FIGS.

In FIG. 3, a biasing spring 2 which is a pressing means.
A cylindrical member 35 is rotatably supported coaxially with the fulcrum 30 of 22, and a pressing force control means, for example, a torque limiter 38 is concentrically attached to the cylindrical member 35 as shown in FIG. The torque limiter 38 has a function of transmitting the rotational drive from the registration roller 21 transmitted by the belt 37 to the cylindrical member 35 with a predetermined torque. or,
The cylindrical member 35 has a protrusion 36, and the protrusion 3
6 presses the biasing spring 222 in the direction of the arrow while the drive from the registration roller 21 is transmitted to the cylindrical member 35.

When the image formation (copying) is started, the transfer material P is first sent out from the registration rollers 21 and 21 'and driven by the registration rollers 21 via the belt 37 and the torque limiter 38. Is transmitted to the cylindrical member 35, and the protrusion 36 starts to pressurize the biasing spring 222. Then, until the torque between the cylindrical member 36 and the torque limiter 38 reaches a predetermined value, the protrusion 3
The biasing spring 222 continues to deform in the arrow direction from the initial position a shown in FIG. After that, the lower guide 22 swings clockwise by the movement of the eccentric cam 221, and the conductor roller 20 as the contact member contacts the transfer drum 6 (FIG. 3).

At this time, the pressing force for lifting the lower guide 22 at the position b of the biasing spring 222 is equal to that of the conductor roller 2.
0 is set to the minimum pressing force required for contacting the transfer drum 6.

Further, the biasing spring 222 reaches the position C before the deformation of the biasing spring 222 progresses and the transfer material P reaches the suction position. The pressing force for lifting the lower guide 22 at this time has reached a pressing force sufficient for the conductive roller 20 to rotate and perform adsorption. On the other hand, the torque limiter 38 is set so as to idle with the torque when the biasing spring 222 reaches the position C, and thereafter, the registration roller 21
The pressure applied by the biasing spring 222 is constant while the drive force from (1) is transmitted to the torque limiter 38. Therefore, the pressure applied to the conductor roller 20 is constant during the transfer material adsorption.

As described above, the pressure applied when the conductor roller 20 is brought into contact with the transfer drum 6 is set lower than that during the suction operation, and the pressure required for the suction is maintained until the suction starts thereafter. By increasing the number, it is possible to reduce the shock at the time of contact with the conductor roller without hindering the attraction of the transfer material, and it is possible to improve the color misregistration.

If desired, a viscous clutch may be used instead of the torque limiter 38, and the same effect can be expected, and these may be used in combination.

Further, if the rotation of the registration roller 21 is stopped before the conductor roller 20 is retracted from the transfer drum 6 after the transfer material P has been attracted, the conductor roller 20 can be stopped.
The pressing force at the time of retreating can be lower than that at the time of adsorption.

Further, when the conductor roller 20 is provided with a cleaning member, it is possible to apply a pressure to the conductor roller 20 to rotate the conductor roller even under the load resistance of the cleaning member. The transmission torque characteristic of the torque limiter 38 or the viscous clutch may be adjusted so that it can be achieved.

As described above, by controlling the pressure applied when the conductor roller, which is the contact member, is brought into contact with the transfer drum, the shock when the conductor roller is brought into contact and withdrawn can be alleviated. It is possible to obtain a high-quality image with improved color misregistration.

[0041]

As described above, the image forming apparatus according to the present invention controls the pressing force during the contact of the contact member such as the transfer material attracting conductor roller that contacts the transfer material carrying member. Since the structure is adopted, it is possible to reduce shock and rotational load fluctuation of the transfer material supporting member to prevent color misregistration, and also to prevent the conductive roller from being soiled with toner to obtain a high quality image. It has the feature.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of the configuration of an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a schematic cross-sectional view of an embodiment of an image forming apparatus according to the present invention, showing a state in which a conductor roller is separated from a transfer material carrying sheet.

FIG. 3 is an enlarged view of a portion K in FIG.

FIG. 4 is a perspective view of a torque limiter.

FIG. 5 is a front view showing an operating position of a biasing spring.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 image carrier (photosensitive drum) 6 transfer device (transfer drum) 6a transfer material carrying member (transfer material carrying sheet) 20 contact member (conductor roller) 35 pressure control means (torque limiter) 222 pressurizing means (attached) Power spring)

Claims (1)

[Claims] 1. An image in which a visible image is formed on an image carrier, and the image is obtained by electrostatically adsorbing the image to a transfer material carrying member by an adsorbing means and transferring the image to a transfer material conveyed. In the forming apparatus, the suction means includes an abutting member that abuts the transfer material carrying member, a pressurizing means that presses the corresponding contact member against the transfer material carrying member, and the transfer material carrying member of the abutting member. And a pressing force control unit that changes the pressing force applied to the image forming device at a predetermined timing.