JP3099145B2 - Image forming device - Google Patents

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 copying machine, and more particularly, to a transfer belt device having a rotating transfer belt for transferring a toner image obtained by developing a latent image on an image carrier. The present invention relates to an image forming apparatus that transfers a recording sheet on which a toner image is adhered to a fixing unit after transferring the recording sheet to the recording sheet by physical means, and performs fixing.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a charger is used to uniformly charge, for example, the peripheral surface of an image carrier, for example, a photosensitive drum. To form an electrostatic latent image. This latent image is developed and visualized by a developing unit to become a toner image. The toner image formed on the peripheral surface of the photosensitive drum is transferred by a physical means onto recording paper fed in time, and the recording paper on which the toner image has been transferred is separated from the photosensitive drum and fixed by the fixing means. The toner image is fixed on a recording sheet and then discharged out of the apparatus.

As a means for transferring the toner image adhering to the peripheral surface of the photosensitive drum onto recording paper, a transfer device which discharges from the back of the recording paper is charged with a polarity opposite to the charging polarity of the toner. The image is transferred to recording paper,
After the transfer, a high voltage of AC is applied by a separator to eliminate the charge, and the recording paper is separated from the photosensitive drum. However, it is difficult to reliably maintain transferability and separability, especially when the drum diameter of the photosensitive drum is large, and it is difficult to separate, and the recording paper after the transfer of the toner image adheres to the photosensitive drum without being separated. It has the drawback of easily causing paper jams and the like. A transfer belt device is used as a technique for improving this disadvantage.

A transfer belt device rotates a transfer belt stretched by a plurality of holding rollers at the same speed as a photosensitive drum. The transfer belt device is provided with a charge applying means for applying a charge to the recording paper and adsorbing the recording paper to the transfer belt by electrostatic force. In the transfer section, a high voltage having a polarity opposite to the toner charging polarity is applied under constant current control to transfer the toner image. In such a transfer belt device, excellent transfer efficiency and separation effect can be obtained in the transfer section.

Such a transfer belt device is used as a particularly preferable device in a color image forming apparatus in which toner images are formed on a photosensitive drum in a superimposed manner and are transferred onto recording paper at one time. In such a color image forming apparatus, since a plurality of developing devices are provided on the peripheral portion of the photosensitive drum in order to overlap the toner image on the photosensitive member, the diameter of the drum becomes large, and sufficient separation performance cannot be obtained by the conventional electrostatic transfer separation method. Therefore, a more reliable separation performance is required, and the method of superimposing toner images requires a large transfer charge amount because a large amount of toner adheres to the toner, so that a large transfer charge holding capability is required. This is because the transfer belt device is excellent in two points.

[0006]

When a transfer belt is used for a long time, toner, paper dust and the like gradually adhere. When the toner image on the photosensitive drum is transferred onto the recording paper, if a jam occurs during the transfer and corona discharge occurs without the recording paper coming to the transfer area, the toner image on the photosensitive drum is Is transferred onto the transfer belt, and the transfer belt becomes largely soiled. If the transfer belt is dirty, the back surface of the recording paper is stained and the quality is degraded, so that the transfer belt is cleaned. As a cleaning means of the transfer belt, cleaning is performed by bringing a blade or a fur brush into contact with the transfer belt. However, when the blade cleaning means is used, the transfer belt and the blade are worn, the durability is reduced, and the cleaning performance is reduced. Further, the fur brush has a problem in that the capability is insufficient at the time of the above-described jam and the removed toner is scattered.

[0007] The present invention less wear of the transfer belt, an image forming apparatus including a transfer belt device good cleaning properties and excellent durability is sustained, when a jam occurs
Quality image immediately without being affected by
It is an object of the present invention to provide an image forming apparatus .

[0008]

SUMMARY OF THE INVENTION The present invention achieves the above object, and the present invention records a toner image formed on a rotating photosensitive drum by corona discharge from a transfer belt stretched between holding rollers and a back surface thereof. in the image forming apparatus having a transfer belt device for transferring the paper, the one of is brought into contact with the roller via the transfer belt to the holding roller, with respect to the holding roller, the roller is the corona discharge having the same polarity potential difference cleaning means is provided for cleaning the transfer belt by applying a bias to have, Ja
Built-in recovery program in case of
And the recovery program operates the cleaning means.
The transfer belt operates so as to pass a plurality of times.
The present invention provides an image forming apparatus characterized by performing the corona discharge .

[0009]

FIG. 1 is a sectional view showing the structure of a color image forming apparatus as an embodiment of the image forming apparatus of the present invention.
First, the configuration and operation will be described.

In FIG. 1, reference numeral 10 denotes a photosensitive drum serving as an image carrier, which has an OPC photosensitive layer coated on the drum, is grounded, and is driven to rotate clockwise. Reference numeral 12 denotes a scorotron charger, which applies V _H (−600 to −800) to the peripheral surface of the photosensitive drum 10.
The uniform charging of V) is given by a corona discharge by a grid and the corona discharge wire which is the potential held in the V _G (-550~-850V). Prior to the charging by the scorotron charger 12, exposure by the PCL 11 using a light emitting diode or the like is performed to eliminate the history of the photoconductor up to the previous print to eliminate the charge on the peripheral surface of the photoconductor.

After the photosensitive member is uniformly charged, the image exposure means 13 performs image exposure based on the image signal. Image exposure means
Reference numeral 13 denotes a reflection mirror 1 via a polygon mirror 131 rotating with a laser diode (not shown) as a light source, an fθ lens, and the like.
The optical path is bent by 32 to perform scanning, and a latent image is formed by rotation (sub-scan) of the photosensitive drum 10.
In the present embodiment, a character portion is exposed to form a reversal latent image such that the character portion has a lower potential V _L (−100 V to 0).

Around the periphery of the photosensitive drum 10, yellow (Y),
Developing devices each containing a built-in developer composed of a toner and carrier such as magenta (M), cyan (C), black (K), etc.
First, development of the first color is performed by a developing sleeve 141 which rotates with a built-in magnet and holding a developer. The developer is a carrier coated with an insulating resin around a ferrite core, a pigment and a charge control agent according to the color with polyester as the main material,
It consists of a toner added with silica, titanium oxide, etc.
It is conveyed to the development area with the layer thickness being regulated to 600600 μm.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is 0.4 to larger than the layer thickness (developer).
1.0mm, _AC of V _AC (1.5-3.0kV _PP ) during this time
A DC bias of V _DC (−500 to −700 V) is superimposed and applied. V _DC and V _H, for charging the toner are both the same polarity, the toner given the opportunity to leave from the carrier by V _AC higher potential than V _DC V _H
Is adhered to the _VL portion having a lower potential than _VDC , and visualization (reversal development) is performed.

After the visualization of the first color is completed, the image forming process for the second color is started, and the uniform charging is again performed by the scorotron charger 12, and a latent image based on the image data of the second color is formed by the image exposure means 13. Is done. At this time, the charge elimination by the PCL 11 performed in the image forming process of the first color is not performed because the toner adsorbed on the image portion of the first color scatters due to a sharp drop in the surrounding potential.

Again, V is applied over the entire surface of the photosensitive drum 10
A latent image similar to that of the first color is formed and developed on a portion of the photoconductor having the potential of _H where there is no image of the first color. the part for a latent image of V _M 'is formed by the charge possessed by the shading and toner itself by adsorption toner of the first color, V _DC
And development according to the potential difference between V _M ′ and V _M ′. In the overlapping portion of the first color image and the second color image, the development of the first color is performed by V _L
When the latent image is formed, the balance between the first color and the second color is lost, so that the exposure amount of the first color is reduced and V _H > V _M (−
(100 to -300 V)> V _{L in} some cases.

The same image forming process as that of the second color is performed for the third color and the fourth color, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10.

On the other hand, the recording paper P fed from the paper feed cassette 21 by the paper feed mechanism 22 is transferred to a transfer belt 31 described later.
The multi-color image on the peripheral surface of the photosensitive drum 10 is collectively fed to the transfer area by the transfer belt
Moved up.

The transfer belt 31 has a thickness of 0.46 having a resistance of 10 ⁶ to 10 ¹⁴ Ω · cm, on which an outer FLC layer of a urethane rubber substrate is formed.
It is an endless rubber belt of about 1.0 mm, and a rib may be provided at an end to prevent a deviation during rotation.

If a static elimination mechanism or the like is provided, a high resistance belt such as a film such as PET or a film coated with PET may be used.

The holding roller 3 that stretches the transfer belt 31
V is applied to the shaft 32a of the upstream holding roller 32 of
A voltage of _PC (1.0 to 3.0 kV) is applied.
A conductive brush 34 as a means for applying electric charges to the recording paper P is grounded at a position where the transfer belt 31 is set via the transfer belt 31 or is grounded via a non-linear element or a resistor. The fed recording paper P enters between the brush 34 and the transfer belt 31, charges are injected into the recording paper P from the brush 34, and an attraction force is applied between the recording paper P and the transfer belt 31. Occurs. Thereafter, the recording paper P enters a nip (transfer area) 35 formed by the photosensitive drum 10 and the transfer belt 31, and a transfer electric field is applied from the back surface of the transfer belt 31 by a corona discharger 36 or a bias roller instead of the corona discharger 36. The multicolor image is transferred onto the recording paper P. In order to ensure pressure contact and transfer at the nip 35, a pressing roller 39 is provided near the upstream side thereof.

The recording paper P separated from the photosensitive drum 10 is
The shaft 33a of the downstream holding roller 33 that stretches the transfer belt 31
The transfer belt 31 is subjected to AC corona discharge as a counter electrode and then subjected to AC corona discharge or while receiving AC corona discharge.
Separate from The toner adhered to the transfer belt 31 is cleaned by cleaning means using a cleaning roller 37 described later with reference to FIG.

The recording paper P holding the multicolor image separated from the transfer belt device 30 is conveyed to a fixing device 23 composed of at least two pressure rollers having a heater inside one of the rollers, and between the pressure rollers. The applied toner is melted by application of heat and pressure, is fixed on the recording paper P, and is discharged out of the apparatus.

The residual toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is subjected to static elimination by a static eliminator 15 using an AC corona discharger, and then enters a cleaning device 16 or from a rubber material in contact with the photoreceptor. The toner is scraped into the cleaning device 16 by the cleaning blade 16a, discharged by a screw or the like, and stored in a collection box. Depending on the arrangement, the above-described static eliminator 15 can be arranged at a position as shown in FIG. 1 so as to simultaneously perform static elimination of the recording paper.

The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 16 is uniformly charged by the scorotron charger 12 after being exposed by the PCL 11,
The next image forming cycle is started. During the formation of the multicolor image, the cleaning blade 16a is separated from the photoreceptor surface,
The AC neutralization by 15 is kept in the OFF state.

FIG. 2 shows the transfer belt device 30 of the image forming apparatus shown in FIG. 1 taken out. FIG. 2B shows a state in which the transfer belt 31 is separated from the photosensitive drum 10, and FIG. (A) shows a state at the time of transfer in which the transfer belt 31 is in contact with the photosensitive drum 10 via the recording paper P. Holding roller
A cleaning roller 37 made of metal or conductive resin is brought into contact with the fixing roller 33 via the transfer belt 31.The holding roller 33 is grounded and the cleaning roller
A positive bias (2 KV) is applied to 37 by a cleaning power supply E (37). Also, this cleaning device has a switch S (37),
The switch S (37) may be turned on in conjunction with the transfer operation shown in FIG. 2A to apply a bias for cleaning, or may be turned on only while the transfer belt 31 is rotating to perform cleaning. A bias may be applied, or the bias may be kept ON regardless of the operation state of the transfer belt 31.

Since the toner that has moved from the photosensitive drum 10 to the transfer belt 31 before or after the transfer or during the transfer is negatively charged by the peeling discharge, the toner attached to the transfer belt 31 contacts the cleaning roller 37 and passes therethrough. At this time, the transfer belt 31 is attracted to the cleaning roller 37 to which a positive bias is applied, and the transfer belt 31 is cleaned. The toner adsorbed on the cleaning roller 37 is removed by the cleaning roller.
It is scraped off by an elastic blade 37a made of PET, rubber, or the like, which comes into sliding contact with 37. When the cleaning means having such a configuration is used, the belt is hardly worn and the cleaning means is also excellent in durability, so that good cleaning properties are maintained for a long time.

In an image forming apparatus using such a belt transfer device, if a recording sheet is not in the nip portion 35 at the time of transfer due to a jam or the like immediately before transfer, a large amount of toner is attracted to the transfer belt 31. I do. In such a case, the transfer belt only needs to pass through the cleaning means once.
Cleaning of 31 will be insufficient. Therefore, when such a jam occurs, a program for the jam is prepared in advance, and the cleaning roller in the state where the bias that has turned on the switch S (37) in the recovery operation is applied is applied.
By transferring the transfer belt 31 several times through the 37 portions and repeating cleaning insufficiently once,
Complete cleaning can be performed. The rotation of the transfer belt 31 for cleaning is performed in such a manner that the transfer belt 31 comes into contact with the photosensitive drum 10 as shown in FIG. 2A, and the transfer discharge by the corona discharger 36 is also performed. Is further improved. Also, during the rotation driving for cleaning the transfer belt 31, the photosensitive drum
10 also rotated without performing image formation, cleaning device
By bringing the cleaning blade 16a of the 16 into sliding contact with the photosensitive drum, not only the transfer belt 31 but also the photosensitive drum 10
Also, the recovery operation after the jam is performed.

[0028]

According to the present invention, the transfer belt is always kept in a clean state without worrying about wear and the like.
An image forming apparatus having a highly reliable transfer belt device capable of obtaining a good recorded image over a long period of time has been provided.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram illustrating a configuration of a transfer belt device of the present invention.

[Explanation of symbols]

 10 Photoconductor drum 11 PCL 12 Scorotron charger 13 Image exposure means 14 Developing device 15 Static eliminator 16 Cleaning device 21 Paper cassette 22 Paper feed mechanism 23 Fixing device 30 Transfer belt device 31 Transfer belt 32, 33 Holding roller 34 Brush (charge Application means) 35 Nip (transfer area) 36 Corona discharger (for transfer) 37 Cleaning roller (transfer belt) 37a Blade (cleaning roller) 39 Press roller E (37) Power supply (for cleaning) S (37) Switch (cleaning) Power supply)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-134560 (JP, A) JP-A-4-174874 (JP, A) JP-A-1-263676 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/16

Claims (1)

(57) [Claims] 1. An image forming apparatus comprising: a transfer belt that stretches a toner image formed on a rotating photosensitive drum between holding rollers; and a transfer belt device that transfers onto a recording sheet by corona discharge from the back surface thereof. A roller is brought into contact with any of the holding rollers via a transfer belt, and a bias is applied to the holding roller so that the roller has a potential difference having the same polarity as the corona discharge, thereby cleaning the transfer belt. cleaning means is provided to perform the recovery program for when a jam occurs is incorporated
And the recovery program is
Actuate the transfer belt through the step a plurality of times,
An image forming apparatus, wherein the corona discharge is sometimes performed .