JPH0566689A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce cost and the quantity of the generation of ozone and to fix a toner image with satisfactory image quality by charging both sides of a transfer material, which advances to fixing unit by a specified electrifying means with charges having opposite polarities. CONSTITUTION:When the transfer material 100 passes between an upper electrifier 25 and a conductive member 27 positioned under it while being in contact with the member 27, charges are injected into the transfer material 100 from the conductive member 27 by the corona discharge of the electrifier 25. The surface on the toner image side is charged with, for example, negative polarity charges which are the same as toner T and positive polarity charges are induced on an opposite surface, thereby electrifying the material with charges having the polarities opposite to each other. Therefore, the toner T advances to a transfer unit 80 while being stably held on the surface of the transfer material 100. Thus, the toner image carried on the surface of the transfer material 100 is not affected by the pressure of a heat roller pair and the pushing force of air at the time of fixation in the fixed unit 80 to obtain the satisfactory image.

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 for transferring and fixing a toner image formed on an image carrier by an electrophotographic method to record an image on a transfer material, and more particularly to corona charging means before fixing.

[0002]

2. Description of the Related Art Generally, in an electrophotographic image forming apparatus such as a copying machine or an image scanner, a platen on which a document is placed, a document irradiation lamp which reciprocates below the platen, an opposite mirror, a fixed projection lens and a reflection mirror. And a photosensitive drum which is endlessly rotated by a scanning electrode and a predetermined potential charged by a band electrode, and toner is applied to the electrostatic latent image formed on the surface of the photosensitive drum by the scanning optical system. Developing device, a transfer electrode for transferring the toner image onto the surface of the transfer material that is conveyed below the surface of the photoconductor drum, a separation electrode and a removing electrode, and a transfer electrode on the surface of the transfer material. And a cleaning device for removing the toner and paper dust remaining on the surface of the photoconductor after transfer.

Then, desired toner images are successively recorded on the surface of the transfer material which is intermittently conveyed along a predetermined conveying path.

Conventionally, the transfer material onto which the toner image is transferred and conveyed to the fixing device may disturb the toner image fixed by the pressing force of the fixing roller or the pushing force of the air. First, corona charging for charging opposite polarity charges to both surfaces of the transfer material is performed once, and the toner image is stably held and fixed on the transfer material by this charging effect. Such measures are well known, for example, by the technical means disclosed in JP-A-61-100767.

That is, as shown in FIG. 3, a pair of chargers 25 and 25A facing each other across a transfer material 100, which is conveyed toward a fixing roller 80, is provided on both sides of the transfer material 100 at a predetermined interval. To the charger 25 located at, a power source 26 for charging, for example, a negative (-) polarity charge of the toner T is connected. A power source 26A for charging electric charges of (+) polarity is connected to the charger 25A located below the chargers 25A, 25A.
Corona discharge is carried out across the entire width of the transfer material conveyed by 25A, and the toner image is held by the electric charge of the opposite polarity formed on the surface of the transfer material 100 so that the fixed toner image of good image quality is recorded. It has become.

[0006]

As described above, when the transfer material on which the toner image is transferred enters the heat roller of the fixing device, the repulsive force of the frictional charge on the fixing roller or the pressure contact roller and the heat roller pair When the transfer paper is squeezed by the pressing force or the like, the toner image on the transfer material is extruded in the direction opposite to the advancing direction, and toner scattering development occurs, which adversely affects the image quality of the toner image. As a measure against such a problem, the technical means shown in the above-mentioned Japanese Patent Laid-Open No. 61-100767 is shown, but two expensive high voltage power supplies required for the corona charger are required and the number of accessory parts is increased to increase the cost. It is a factor. Further, as the number of corona chargers is increased, the amount of ozone generated will inevitably increase, which is a problem in terms of safety standards for the human body. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide an image forming apparatus capable of recording a good toner image at the time of fixing by using a charging unit that reduces cost and generates a small amount of ozone.

[0007]

To this end, the toner on the image bearing member on which the toner image has been transferred is transferred to the fixing device by corona charge removal at the separating position to separate the transferring material, and then the toner is conveyed to the fixing device for fixing. In the image forming apparatus, a corona charger is disposed on the toner image side of the transfer material before fixing the toner image, and a conductive member is disposed on the opposite side of the toner image side to face the corona charger. Is achieved by an image forming apparatus.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. 1 which is a side view showing the structure of a charging means for a transfer material before fixing and FIG. 2 which is a side sectional view showing the structure of a color image forming apparatus.

However, the present invention is not limited to this embodiment.

As shown in FIG. 2, the color image forming apparatus 1
Reference numeral 10 is a drum-shaped image bearing member, that is, a photosensitive drum.
The C photoconductor is applied on the drum, and is grounded and driven and rotated clockwise. 20 is a scorotron charger for applying electric charges to the photoconductor on the peripheral surface of the photoconductor drum 10, and 13 is an image exposure light or a laser beam for focusing on the peripheral surface of the photoconductor drum 10 by an exposure optical system (not shown). Is an image exposure unit on which is projected.

A laser writing system unit is used for the exposure optical system, for example. When a color signal output from an image reading apparatus separate from the color image forming apparatus 1 is input to the laser writing system unit, the laser writing system unit emits a laser beam (wavelength). 780 nm) is rotated and scanned by the polygon mirror, the optical path is bent by the reflection mirror through the fθ lens, and projected onto the peripheral surface of the photoconductor drum 10 which is uniformly charged by the charger 20 in advance.

On the other hand, when the scanning is started, the laser beam is detected by the index sensor, the modulation of the laser beam by the first color signal is started, and the modulated laser beam scans the peripheral surface of the photosensitive drum 10. To do. Therefore, a latent image for the first color is formed on the image portion on the photosensitive drum 10 by the main scanning by the laser beam and the sub-scanning by the rotation of the photosensitive drum 10. This latent image is subjected to reversal development by a developing means that contains, for example, yellow (Y) toner as the first color, and a yellow toner image is formed on the peripheral surface of the photosensitive drum 10. The toner image of the obtained image portion is held on the peripheral surface of the photoconductor drum 10 while being held.
After passing under the transfer unit and the cleaning unit separated from the peripheral surface of 10, the next copy cycle is started.

That is, the photosensitive drum 10 is recharged by the charger 20, and then the second color signal output from the signal processing unit is input to the writing system unit.
Similar to the case of the first color signal described above, the photoconductor drum
Writing is performed on the 10th circumferential surface by the second color signal to form a latent image. This latent image is subjected to reversal development by a developing unit that contains, for example, magenta (M) toner as the second color, and a magenta toner image is formed. The magenta toner image is formed on the previously formed yellow toner image.

The toner image of the image portion thus obtained is held on the peripheral surface of the photoconductor drum 10 and is retained.
After passing under the transfer means and the cleaning means separated from the peripheral surface, the next copy cycle is started.

In the same manner, writing with the third color signal is performed on the photosensitive drum 10 to form a latent image. This latent image is subjected to reversal development by a developing means that contains, for example, cyan (C) toner as the third color. A color image is obtained by forming the cyan toner image on the yellow and magenta toner images described above. Further, as in the present embodiment, a developing unit containing a black toner is provided, and a high-quality color image can be obtained by further superposing the black toner image in the same manner as described above.

The developing device 41 is yellow, the developing device 42 is magenta, the developing device 43 is cyan, and the developing device 44 is a developing device as a developing means for accommodating each black toner.

The charging by the charger 20 provided on the photosensitive drum 10 and the peripheral portion thereof, the exposure by the laser writing system unit for each color, and the development processing by the developers 41 to 44 are performed four times for each color. That is, a color toner image is formed on the image portion on the peripheral surface of the photoconductor drum 10 by superposition. Further, 51 and 52 of the first transfer material conveying section 50 are paths of transfer material of different sizes which are fed one by one from the transfer material supply device, and 53 is movement of the color toner image on the photosensitive drum 10. It is a registration roller for conveying the transfer material to the transfer unit 160 in synchronization with.

Reference numeral 70 is a transfer belt device, 71 is a transfer belt which is a belt portion, and 72 and 73 are rollers made of a conductive metal material. The upstream roller 72 is grounded or set to a predetermined potential close to the grounded state. The roller having a rotatable shaft and the roller 73 on the downstream side are rollers for driving the transfer belt 71 having a fixed shaft. 74 is a belt supporting member, one end of which is fixed to the axis of the roller 73 and the other end of which is connected to the movable shaft of the roller 72. An elastic member (not shown) urges the roller 72 to be positioned below. Has been done. Therefore, the transfer belt 71 is normally retracted from the peripheral surface of the photoconductor drum 10 (at the time of non-transfer), and the eccentric cam 77 operated by the control of the apparatus control unit at the time of transfer is driven by the belt spring 78 via the plate spring 78. In the figure, the roller 73 is rotated counterclockwise around the swing center of the roller 73, and the rollers 76 provided on both side ends of the belt support member 74 are located at the side end portions of the peripheral surface of the photosensitive drum 10 outside the image portion. Then, the transfer belt 71 is brought into contact with the transfer portion 160 of the photosensitive drum 10.

Reference numeral 79 is a cleaning blade of a belt cleaning device for scraping off the toner adhered on the transfer belt 71,
Reference numeral 95 denotes a toner conveying pipe having a flexible conveying screw inside, and conveys the toner scraped by the cleaning blade 79 to a toner collecting box (not shown).

The transfer belt 71 is composed of, for example, two layers, and the main body is an endless high-resistivity sheet having a volume resistivity of about 10 ¹⁰ Ω · cm such as silicon rubber, polyurethane rubber or butyl rubber having a thickness of about 0.5 to 1 mm. Then, for example, a fluorine resin is sprayed on the upper layer of this sheet to reduce the frictional resistance and prevent the adhesion of dirt.

Reference numeral 16 is a transfer device which is a transfer charging device provided at a position facing the transfer portion 160, and 60 is wound around a roller 72 in a wedge-shaped cross section space between the transfer belt 71 and the photosensitive drum 10. A paper charger, which is a paper charging means for the transfer material, is arranged so as to face the transfer belt 71. Reference numeral 61 is a conductive fiber material provided in the paper charger 60 and is made of a conductive material for charging the paper before transfer. 66 is a charging brush with elasticity as a member.
It is a power supply for applying a bias voltage to 61. A protective resistor may be inserted in series between the charging brush 61 and the power supply 66 in order to prevent a large current from flowing when the charging brush 61 comes into contact with a ground portion or the like.

The paper charger 60 is rotatably supported with a shaft 60A as a fulcrum, and holds a charging brush 61 made of a conductive elastic fiber member at its tip.

Further, the paper charger 60 is elastic with respect to the peripheral surface of the transfer belt 71 in which the tip of the charging brush 61 is in contact with the photosensitive drum 10 due to the rotational phase of the eccentric cam 62 inscribed in the square hole 60B. The charging brush 61 by rotating the paper charger 60 in a clockwise direction to bring it into contact with each other.
Can be retracted from the peripheral surface of the transfer belt 71 in contact with the photosensitive drum 10. Transfer belt 71
Is separated from the photosensitive drum 10, the eccentric cam 62
The charging brush 61 does not contact the transfer belt 71 in any of the above phases.

That is, as described above, the photosensitive drum 10
After the development by the developing device 44 containing the toner of the fourth color is started, the operation of the registration roller 53 and the pressure contact operation of the transfer belt 71 are performed, and when the transfer paper is further fed, the paper is transferred. The contact operation and voltage application by the charging brush 61 of the charger 60, and the retracting operation of the charging brush 61 are performed when the transparency is fed.

When the front end of the transfer material reaches the transfer portion 160, the transfer material is pressed against the photosensitive drum 10 by the transfer belt 71. Then, the transfer device 16 charges the toner on the photoconductor drum 10 in a polarity opposite to that of the toner, and transfers the toner image onto the transfer material. The transfer material on which the toner image has been transferred is separated and discharged, and further conveyed by the transfer belt 21 and is charged by a charging device including a charging device 25 and a conductive member 27, which are connected to a power source 26 described later provided on the right side of the fixing device 80. After being charged with a predetermined electric charge and reaching the fixing device 80 to be fixed by heating and welding, the paper is discharged to an external paper discharge tray. 55 is a separation claw for preventing the recording paper from accidentally entering upward.

Rotation, pressure contact and transfer device 16 of the transfer belt 71
The photoconductor drum 10 that has been transferred by the charging action by the cleaning device is cleaned by the cleaning device 90. The cleaning device 90 includes a cleaning blade 91 as a cleaning unit, a toner recovery roller 92 that electrostatically collects residual toner, and the like. Having a photoconductor drum 10
While the toner image is being formed on the peripheral surface, the cleaning blade
91 is in the retracted state, and the photosensitive drum
Press to 10 and clean. In addition, the static elimination lamp 93 is provided on the upstream side of the cleaning device 90 and the static elimination lamp is provided on the downstream side.
94 is located, and the static elimination lamp 93 eliminates static electricity so that the residual toner on the peripheral surface of the photosensitive drum 10 can be easily removed.
Reference numeral 94 uniformly removes the cleaned peripheral surface of the photosensitive drum 10 so that uniform charging is performed. Further, at the bottom of the cleaning device 90, a toner carrying pipe 95 having a toner carrying screw made of a flexible material is provided, and the waste toner collected by the cleaning is carried to a toner collecting box (not shown). The photoconductor drum 10 that has completed the cleaning starts the next image forming process.

The present invention eliminates the above-mentioned problems and reduces the cost for preventing the disturbance of the toner image due to the fixing process. Moreover, the charging means that generates a small amount of ozone is configured as follows.

As shown in FIG. 1, the transfer material 100 to which the toner image has been transferred is conveyed toward the fixing device 80 by the second conveying section 50A in the direction indicated by the arrow. Then, at a suitable position immediately before the transfer material 100 reaches the fixing device 80, a charger 25 is provided at a predetermined interval above the surface of the transfer material 100 on which the toner image is formed, and the charging device 25 is provided. For example, with the same polarity (-)
It is connected to a power supply 26 for charging the polarity with electric charge.

On the other hand, on the surface of the transfer material 100 opposite to the toner image, a conductive member 27 made of a rotatable conductive rod-shaped metal material is provided to be grounded.
Comes into contact with and rotates in the direction indicated by the arrow. And charger
The 25 and the conductive member 27 are configured to be uniformly charged with a predetermined charge over the entire width direction of the transferred transfer material 100.

When the transfer material 100 passes between the upper charging device 25 and the lower conductive member 27 in contact with the conductive member 27, the transfer material 100 is transferred from the conductive member 27 by corona discharge of the charging device 25. Charge is injected into the material 100, and as shown in the figure, the surface of the toner image side is charged with, for example, the electric charge of the (−) polarity which is the same polarity as the toner T, and the opposite surface is induced with the electric charge of the (+) polarity, and the two surfaces are charged with each other. An electric charge of opposite polarity is charged.

The timing of this corona discharge is discharged in synchronization with the sequence of the transfer material 100 being conveyed.
Predetermined charges are sequentially charged over the entire region from the front end to the rear end of the. This corona discharge is performed in synchronism with the transfer material that is intermittently conveyed, but it may be possible to discharge continuously while the color image forming apparatus 1 is operating (the fixing device is operating). ..

Therefore, for example, the toner T having the (-) polarity enters the fixing device 80 while being stably held on the transfer material surface 100 by the charge of the (+) polarity charged on the opposite surface of the transfer material 100. To do.

In this way, the toner image carried on the surface of the transfer material 100 is a very good toner image without being affected by the pressing force of the heat roller pair and the pushing force of air during fixing in the fixing device 80. It is fixed.

Then, the transfer material 10 on which the toner image is fixed
0 is discharged by passing through a known charge removal brush provided in a discharge port (not shown) of the color image forming apparatus 1 and discharged to the outside of the apparatus.

In the charging means of the present invention thus constructed, the cost is reduced because the expensive high-voltage power supply and its attached members are omitted as one charger is omitted as compared with the conventional charging means. In addition, the amount of ozone generated can be reduced inevitably.

[0036]

EFFECT OF THE INVENTION Since charging means composed of one charging device of the present invention and a conductive member facing the charging device charges both sides of the transfer material entering the fixing device with opposite polarities, the conventional method is used. In comparison, the cost is remarkably reduced and the amount of ozone generated is also reduced, so that a toner image of good quality is fixed.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a charging unit for a transfer material before fixing according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing the configuration of a color image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a side view showing a configuration of a conventional charging unit for a transfer material before fixing.

[Explanation of symbols]

 1 Color Image Forming Device 10 Photosensitive Drum 16 Transfer Device 25 Charging Device 26 Power Supply 27 Conductive Member 41 Developing Device (Yellow) 42 Developing Device (Magenta) 43 Developing Device (Cyan) 44 Developing Device (Black) 50A Transfer Material Conveying Section 70 Transfer belt device 80 Fixing device 90 Cleaning device 100 Transfer material

Claims (1)

[Claims] 1. An image forming apparatus in which a transfer material on a transfer material carrier, on which a toner image on the image carrier is transferred, is separated by corona charge removal at a separation position, and is conveyed to a fixing device for fixing.
An image characterized by disposing a corona charger on the toner image side of the transfer material before fixing the toner image, and disposing a conductive member on the opposite side of the toner image side so as to face the corona charger. Forming equipment.