JP3196525B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transfer type electrophotographic apparatus.
The present invention relates to an image forming apparatus such as an electrostatic recording device.

More specifically, a developer image (transferable image, toner image) formed on an image carrier is brought into contact with the back surface of a fed transfer material (recording material) to transfer charges for transfer. An image forming apparatus for transferring from an image carrier to a transfer material by a contact type transfer unit that imparts a toner image, that is, a transfer portion between the image carrier and a transfer unit that comes into contact with the image carrier (contact nip between the image carrier and the transfer unit) The present invention relates to an image forming apparatus of a type in which a transfer material is fed to a transfer unit and a developer image formed and carried on an image carrier is transferred onto the transfer material.

[0003]

2. Description of the Related Art Conventionally, in a transfer type image forming apparatus,
Transfers a developer image corresponding to the target image information, formed and supported on an image carrier such as a photoreceptor, dielectric or magnetic material by an appropriate image forming process such as electrophotography, electrostatic recording, or magnetic recording A non-contact type transfer device using a corona charger has been widely used as a transfer means for transferring to a material.

In this method, a corona charger is provided in a non-contact manner on an image carrier, and a transfer material is fed between the image carrier and the corona charger. A corona discharge charge of a predetermined polarity for transfer is applied by a charger, and the formed and carried toner image as a developer image on the image carrier is electrically attracted to the surface of the transfer material to be transferred.

However, this transfer means must apply a considerably high voltage to the corona charger to generate corona discharge, and therefore requires a high-voltage power supply, and ozone is generated due to the corona discharge. And so on.

For this reason, in recent years, a contact-charging type transfer means (contact-type transfer means) in which a relatively low voltage only needs to be applied.
An image forming apparatus using the same has been developed.

In this method, a charging member such as a conductive roller or a conductive brush is provided in contact with a transfer member as a transfer member, and a transfer material is fed to a transfer portion which is a contact nip portion between the two.
A bias voltage is applied to the back surface of the transfer material to a transfer member that is in contact with the back surface to charge (contact charge) a predetermined polarity for transfer so that the toner image formed on the image carrier is formed on the front surface of the transfer material. The image is transferred electrically by being electrically sucked.

In such a contact charging type transfer means, the voltage applied to the transfer member may be relatively low, and the current may be relatively small.
There are advantages such as lower cost and less ozone generation.

On the other hand, the transfer member may be contaminated by the oppositely charged toner adhered to the non-sheet passing area on the image carrier or the residual toner after the occurrence of the jam.

Therefore, in such an image forming apparatus, the toner adhering to the transfer member is removed during non-sheet passing such as during pre-rotation at the beginning of operation or during continuous sheet feeding. Means is employed in which a polarity voltage (same polarity as the toner) is applied to transfer the toner adhered to the transfer member to the image carrier to clean the transfer member.

When a jam occurs, the transfer member is significantly contaminated because the toner image on the image carrier is directly transferred. In order to cope with this, when a jam occurs, after the power is turned on again,
A warm-up time is provided until the apparatus is activated, and a means for applying a voltage for transferring the toner from the transfer member to the image carrier during this time is used.

[0012]

However, when the transfer member is significantly contaminated with toner, the cleaning during the warm-up time alone does not sufficiently remove the contamination of the transfer member, and contaminates the back surface of the subsequent transfer material. is there.

An object of the present invention is to solve this problem in an image forming apparatus using a contact type transfer unit.

[0014]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

The image of the image-forming agent image formed on the support member, an image forming apparatus for transferring onto the transfer material from the image bearing member by the contact-type transfer means for imparting an electric charge to be transferred in contact with the back surface of the transfer material And a means for forming an electric field between the image carrier and the transfer means when the transfer material is not passing the paper, in a direction to transfer the developer adhered to the transfer means from the transfer means to the image carrier. After the occurrence , give the transfer material
Bias and the surface potential of the image carrier
Image forming apparatus and controls the magnitude of the electric field Te.

[0016]

[0017]

[Function] After a jam occurs, transfer is performed while a fixed number of transfer materials are passed .
Surface electrostatic image bearing member with increasing the bias applied to the means
By controlling the magnitude of the electric field by increasing the level , cleaning of the transfer member after the recovery from the jam is promoted, and remarkable dirt on the transfer member and back dirt on the transfer material based on the dirt can be avoided.

[0018]

FIG. 1 is a schematic view of an image forming apparatus according to an embodiment. The image forming apparatus of this embodiment is a transfer-type laser printer or copier utilizing an electrophotographic process.

Reference numeral 1 denotes a drum-type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) serving as an image carrier, which is attached to a conductive base layer 1b made of aluminum, iron, or the like, and to an outer peripheral surface thereof. For example, a photoconductive layer 1a made of an organic photoconductor is used as a basic constituent layer, and is driven to rotate around a support shaft 1d in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed). The conductive base layer 1b is grounded.

The photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the primary charging device 2 during its rotation.
In this example, the photosensitive drum is charged negatively.

The primary charging device 2 of this embodiment is a contact charging roller, and includes a conductive roller 2c such as a metal roller serving as a core metal, a conductive layer 2b formed on the outer peripheral surface thereof, and a resistance layer formed on the outer peripheral surface thereof. consists 2a ₁ · 2a ₂ Prefecture, the both end portions of the conductive roller 2c disposed rotatably supported to parallel with the photosensitive drum 1 by a bearing member omitted in the figure, the pressing of the spring or the like (not shown) The photosensitive drum 1 is pressed against the photosensitive drum 1 with a predetermined pressing force by means, and is rotated by the rotation of the photosensitive drum 1.

An electric contact 3a is applied to the conductive roller 2c.
By applying a predetermined bias voltage (DC voltage or vibration voltage) from the power supply 3 via the power supply 3, the peripheral surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by a contact charging method.

Next, the charged surface is subjected to image exposure processing of the target image information by an image exposure means 5 such as a laser scanner / slit exposure means, and an electrostatic latent image of the target image information is formed on the photosensitive drum 1 surface. It is formed.

The electrostatic latent image is developed by a developer (developer, toner) carried in a thin layer on the developing sleeve 6a of the developing device 6 to become a visible image (toner image). In this example, development is performed with a positively charged toner (positive toner).

The toner image is fed to the transfer portion N at a predetermined timing from the paper feeding portion side in a transfer portion N which is a contact nip portion between the photosensitive drum 1 and the transfer member 7 brought into contact therewith. The transfer material 14 is sequentially transferred to the transferred transfer material 14. The transfer material 14 is introduced one by one into the apparatus from a paper feed unit such as a paper feed cassette or a manual feed tray (not shown), and is transferred along a route of a paper feed roller 11 → a transport roller 12 → a resist roller 13 → a guide 9 before transfer. It is fed to the section N.

The transfer member 7 of this embodiment is a contact charging transfer roller, and a conductive roller 7a such as a metal roller serving as a core metal,
And a cylindrical conductive layer 7b formed on the outer peripheral surface thereof. Both ends of the conductive roller 7a are rotatably supported by bearing members (not shown), and are disposed in parallel with the photosensitive drum 1. The photosensitive drum 1 is pressed against the photosensitive drum 1 by pressing means such as a spring shown in the drawing, and rotates following the rotation of the photosensitive drum 1. The transfer nip portion is a contact nip portion between the photosensitive drum 1 and the transfer roller 7.

The transfer material 14 is fed to the transfer portion N and is nipped and conveyed. When the leading end of the transfer material 14 enters the transfer portion N, a predetermined transfer bias voltage (minus in this example) is applied from the power supply 4 to the conductive roller 7a, and the back surface of the transfer material with which the transfer roller 7 is in contact is transferred. The toner image on the photoreceptor drum 1 is transferred to the surface of the transfer material by being charged in a contact charging type with a polarity (minus) opposite to the toner (plus).

The transfer material 14 to which the toner image has been transferred through the transfer portion N is separated from the surface of the photosensitive drum 1 and sent to an image fixing means (not shown), and the transferred toner image is transferred to the transfer material 14.
The image is fixed thereon as a permanent fixed image, and is discharged outside the machine as a print or a copy.

On the other hand, the surface of the photoreceptor drum after passing through the transfer section is cleaned by removing the residual developer and other deposits by a cleaner 8, and further, a static eliminator (static elimination lamp) 1
It is initialized by being neutralized by 0, and repeatedly provided for image formation.

The charging roller 2 and the transfer roller 7 of the contact charging type may be provided with gears or the like, and may be forcibly driven by driving means such as a motor.

(2) Cleaning Sequence of Transfer Roller 7 a) Normal Time During non-transfer, that is, during the pre-rotation, post-rotation and continuous copying of the image forming apparatus, the power supply 4 transfers the transfer roller 7
(Hereinafter referred to as a cleaning bias) is changed to a polarity (plus, the same polarity as the toner) opposite to that at the time of transfer (minus) to form an electric field in which the toner is directed toward the photosensitive drum. The transfer roller 7 is cleaned by transferring the toner attached to the transfer roller 7 to the photosensitive drum 1 side. The toner transferred from the transfer roller 7 to the photosensitive drum 1 is removed by the cleaner 8.

To explain this more specifically, at the time of non-transfer, a cleaning bias of +2.5 KV is applied to the transfer roller 7 from the power supply 4 for one rotation or more of the transfer roller (for a process speed of 105 mm / sec, the transfer roller 7 of φ16 mm is used). (Approximately 500 msec). At the same time, a voltage is applied to the charging roller 2 from the power supply 3 to uniformly charge the surface potential of the photosensitive drum 1 to -400 V, so that the toner on the transfer roller 7 is easily transferred to the photosensitive drum 1.

B) Jam When the jam occurs, the toner image on the photosensitive drum 1 is directly transferred to the transfer roller 7, so that the transfer roller 7 is significantly contaminated. Therefore, when a jam occurs, the transfer roller 7 is cleaned as described above during a warm-up time after the power is turned on again and before the apparatus is activated.

. Reference Example 1 In the present reference example 1 , the cleaning time of the transfer roller 7 at the time of occurrence of a jam, after recovery, during copying of a fixed number of transfer materials, during pre-rotation, post-rotation, and between sheets, is reduced. Extend.

FIG. 2 is a graph in which the application time of the cleaning bias to three copies of A4 size paper after the recovery from the jam and the paper back stain at that time are evaluated in five levels. As shown in this graph, when the cleaning time is extended for several sheets after the recovery from the jam, the cleaning property of the transfer roller 7 is improved.

As a comparative example, a case where the cleaning time is constant (about 500 msec) will be described. When the cleaning time is the same as the conventional length, the cleaning is not sufficiently performed when the transfer roller 7 is extremely contaminated as described above. Conversely, if the cleaning time is set to be always long, a memory may be generated in the photosensitive drum 1 and deterioration may be stopped.

[0037] Thus, after the jam recovery as shown in the reference example 1, when pre-rotation only while the copy of the transfer material predetermined number is performed, to extend the cleaning time of the transfer roller 7 at the post-rotation time and the sheet interval The method is effective.

[0038]. REFERENCE EXAMPLE 2 In this reference example 2 , cleaning applied to the transfer roller 7 from the power supply 4 during a copy operation of a predetermined number of transfer materials during a jam occurrence, after recovery, during pre-rotation, post-rotation and between sheets. Increase bias.

FIG. 3 is a graph in which the cleaning bias for three copies of A4 size paper and the stain on the back of the paper at that time are evaluated in five stages after the recovery from the jam. As shown by the solid line in this graph, the cleaning property of the transfer roller 7 is improved by increasing the cleaning bias for several sheets after the recovery from the jam.

[0040]. Embodiment The basic configuration is the same as that of the second embodiment . In the present embodiment, the power supply 4 during the pre-rotation, the post-rotation, and the paper interval during the copying of a fixed number of transfer materials after the recovery from the jam.
, The cleaning bias applied to the transfer roller 7 is increased, and the surface potential of the photosensitive drum 1 by the charging roller 2 is increased.

In FIG. 3, the solid line indicates the case where the surface potential of the photosensitive drum 1 is -400V, the broken line indicates the case where -600V, and the one-dot chain line indicates the case where -200V.

As shown here, when the cleaning bias is increased and the surface potential of the photosensitive drum is increased, the toner on the transfer roller 7 is easily transferred to the photosensitive drum 1, and the cleaning of the transfer roller 7 is further promoted. .

Therefore, the configuration of this embodiment sufficiently cleans the transfer roller 7 after the jam.

In the above embodiment, the case where the transfer roller is used as the transfer member has been described. However, the present invention is not limited to the roller type, and the present invention can be applied to other types of members such as a transfer belt or a transfer brush. It is also possible to apply.

[0045]

As described above, according to the present invention, in the case of an image forming apparatus using a contact-type transfer means, when a jam occurs, cleaning of the transfer member after the recovery from the jam is promoted, so that the transfer member is markedly remarkable. It is possible to avoid stains and back stains on the transfer material based on the stains.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an example of an image forming apparatus.

FIG. 2 is a graph showing the relationship between the application time of the cleaning bias of the transfer roller after the recovery from the jam and the level of stain on the back of the paper after copying three sheets of A4 size paper.

FIG. 3 is a graph showing a relationship between a transfer roller cleaning bias application voltage after a jam recovery and a level of paper back stain after copying three sheets of A4 size paper.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image carrier (electrophotographic photosensitive drum) 2 primary charging device (contact charging roller) 3.4 bias application power supply 5 image exposure means 6 developing device 7 transfer member (contact charging transfer roller) 8 cleaner 9 pre-transfer guide 10 remove Appliance 11 Paper feed roller 12 Transport roller 13 Registration roller 14 Transfer material

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-104836 (JP, A) JP-A-5-11641 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/00 303

Claims (1)

(57) [Claims] 1. An image in which a developer image formed on an image carrier is transferred from the image carrier to a transfer material by a contact-type transfer unit that contacts a back surface of the transfer material and applies a charge for transfer. A forming device configured to form an electric field between the image carrier and the transfer unit when the transfer material is not fed, in a direction to transfer the developer adhered to the transfer unit from the transfer unit to the image carrier; After a paper jam occurs, raise the bias applied to the transfer
An image forming apparatus for controlling the magnitude of the electric field by increasing the surface potential of the image carrier .